Analele Universităţii
"Eftimie Murgu"
Fascicula de Inginerie
ISSN-L 1453-7397
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Anul XXI (2014), Nr. 1




A Combined Control Scheme for Monitoring Quality Characteristics

Adekeye K. S, Bada Olatunbosun

In the literature, the Exponentially Weighted Moving Average (EWMA) and Exponentially Weighted Moving Variance (EMWV) control schemes have been used separately to monitor the process average and process variability respectively. Here the two are combined and applied on simulated process with different level of variation. The control limit interval (CLI) and the average run length (ARL) were evaluated for the combined chart. The combined chart performed better than the two independently. Furthermore, an algorithm was developed for the two control charts and implemented on visual basic VB6.0. The obtained results show that the combined EWMA and EWMV control chart is very sensitive in detecting shift in production process and every shift in the process mean is always preceded by shift in the process variability..

Keywords: statistical process control, control chart, Exponentially Weighted Moving Average (EWMA), Exponentially Weighted Moving Variance (EMWV)

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Stochastic Modelling of Linear Programming Application to Brewing Operational Systems

Akanbi O.P.

System where a large number of interrelated operations exist, technically-based operational mechanism is always required to achieve potential. An intuitive solution, which is common practice in most of the breweries, perhaps may not uncover the optimal solution, as there is hardly any guarantee to satisfy the best policy application. There is always high foreign exchange involved in procurement of imported raw materials and thus increases the cost of production, abandonment and poor utilization of available locally-sourced raw materials. This study focuses on the approaches which highlight the steps and mechanisms involved in optimizing the wort extract by the use of different types of adjuncts and formulating wort production models which are useful in proffering expected solutions. Optimization techniques, the generalized models and an overview of typical brewing processes were considered.

Keywords: wort, extracts, adjuncts, models optimization, brewing, techniques, raw, materials, production

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Performance and Sensitivity Evaluation of a Developed Cassava-Grating Machine

Akanbi O.P.

Performance and economic returns of developed cassava-grating machine was investigated. The equipment has a realistic functional efficiency of 71.5% and the discharge capacity 4.04 tons per day. Simulation of its economic analysis shows that $26.3 could be saved while using cassava grater over convection system for 1-ton of cassava tuber. At 0.01 and 0.05 level of significance, it showed that the machine has a good economic potential over the convection method of grating. It saves time and labor requirements by a factor of 0.67.

Keywords: Cassava, Grating, Convectional, Efficiency, Economic, Potential, Ton, Discharge

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Economical Utilization of Associated Gas in Nigeria

Lukman Obayopo Alimi

Oil production is often accompanied by associated natural gas as valuable by-product of oil processing. Large amount of this vital energy component is flared during these processes, mostly in developing countries. For a longer period of time more gas is flares in Nigeria than anywhere else in Africa and second to Russian in the world, with daily estimates of roughly 2.5 billion cubic feet. This is equivalent to around 40% of all Africa´s natural gas consumption, and annual financial loss to Nigeria is about 1.8 billion Euros. Gas flaring contributes to major environmental pollution problems, which affects oil producing areas of the Niger Delta in Nigeria. This research attempts to look into the environmental issues in the region and proposes possible solutions, with recommendations that will contribute to improve associated gas utilization. This study describes gas to liquid (GTL) conversion technology as a sustainable option to utilize associated gas in Nigeria, and also evaluates the economic attractiveness of the process. This conversion technology could contribute to total elimination of gas flaring and reduces the overdependence on importation of refined products (petrol, diesel and kerosene) from foreign countries into Nigeria.

Keywords: associated natural gas, gas utilization, gas to liquid technology, Fischer Tropsch Synthesis, market analysis

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Potential of Computerized Maintenance Management System in Facilities Management

Noor Farisya Azahar, Md Azree Othuman Mydin

For some time it has been clear that managing buildings or estates has been carried out in the context of what has become known as facilities management. British Institute of Facilities Management defined facilities management is the integration of multi-disciplinary activities within the built environment and the management of their impact upon people and the workplace. Effective facilities management is vital to the success of an organisation by contributing to the delivery of its strategic and operational objectives. Maintenance of buildings should be given serious attention before (stage design), during and after a building is completed. But total involvement in building maintenance is after the building is completed and during its operations. Residents of and property owners require their building to look attractive, durable and have a peaceful indoor environment and efficient. The objective of the maintenance management system is to stream line the vast maintenance information system to improve the productivity of an industrial plant. a good maintenance management system makes equipment and facilities available. This paper will discuss the fundamental steps of maintenance management program and Computerized Maintenance Management System (CMMS)

Keywords: facilities management, building, computerized maintenance, built environment, CMMS

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Stability Analysis for Hand-arm-forearm Dynamic System

Florin Bausic, Alexandru Cosmescu, Filip G?rd?reanu

In this paper we propose a model with four degrees of freedom for hand-arm-forearm dynamic system. Using experimental data from [9] by means of the Simulink program, is built block diagram to simulate the dynamic system motion and phase diagrams are drawn by using Matlab. From the interpretation of these diagrams result, for a set of parameters ( m, c, k, FO, ? ), stable moves for the hand-arm-forearm dynamic system.

Keywords: stability, dinamic system, Simulink, Matlab

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Influence of Cutting Regime Parameters on Edge Endurance of Lathe Tool

Ana-Maria Budai

In mechanical industry, to increase productivity is very important to correctly establish the factors that influence the process dynamic. One of these factors is the features cutting regime. In practice, the technological process optimization depending by the value of the characteristics parameters. The paper purpose is to reveal the influence of operating speed and penetration speed over edge endurance of a lathe tool.

Keywords: cutting, regime, parameters, endurance, tool

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Best Practice of Construction Waste Management and Minimization

Khor Jie Cheng, Md Azree Othuman Mydin

Material management is an important issue as seen in construction waste management. Best practice of material management is accompanied by various benefits which are acknowledged by several studies. The site layout has particular effects on both materials and their waste through effective waste management practice. Ignoring the benefits of material management could result in a daily reduction in productivity of up to 40% by material wastage. Thus, the benefits of effective material management must be well comprehended for the sake of waste minimization. Another convincing fact about waste is that poor site management accounts for the largest factor of waste generation. Hence the site condition is very crucial in developing effective material management. Factors contributing to the efficiency of material management process are effective logistical management and supply chain management. The logistics system must be performing as schedule so that materials are wisely managed on-site without encountering presence of excessive materials. As materials management is closely related to logistics in construction projects, there will be delay in construction projects when materials are not delivered to site as scheduled. The management must be effective in terms of delivery, off-loading, storage, handling, on-site transportation and on-site utilization of materials.

Keywords: sustainable practice, prefabrication, construction, waste, management, building material, waste control, IBS

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Influence of Thread Root Radius on Maximum Local Stresses at Large Diameter Bolts under Axial Loading

Vasile Cojocaru, Zoltan Iosif Korka

In the thread root area of the threaded bolts submitted to axial loading occur local stresses, higher that nominal stresses calculated for the bolts. These local stresses can generate failure and can reduce the fatigue life of the parts. The paper is focused on the study of the influence of the thread root radius on the maximum local stresses. A large diameter trapezoidal bolt was subjected to a static analysis (axial loading) using finite element simulation.

Keywords: threaded bolts, local stress, FEM analysis, 2D simplification

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Numerical Study of Shear Stress Around an Ideal Roughness

Michaela Fomin Vasilache, Ionut Cristian Rominu, Ilie Musca

In EHD lubrication conditions the viscosity of the lubricants increases, occuring at high shear rates of plastic behavior. Previous researches showed that the shear stress in the film thickness of the lubricant may vary, affecting the lubrication. This paper presents a numerical study on the effect of the presence of an ideal roughness on the flow behavior and the shearing of the lubricant film.

Keywords: plastic shear, pressure distribution, roughness

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Modelling Water-Sanitation Relationship in Edo State, Nigeria

Philipa O. Idogho, Olotu Yahaya, Dagona A.G.

An effective understanding of water and sanitation supply in developing states such as Edo-state is a veritable tool in addressing uneven distribution of these utilities. This research study focuses on the evaluation of water and sanitation supply in the state using baseline and demand responsiveness approaches to capture data on water and sanitation supplies in all the 18 local government areas in the State. Variables such as coverage of access or no access to water and sanitation supply, sources of water and incidences of water-related diseases were captured and technically analysed. The output of the analysis revealed that 62% representing 1,346, 649, population could not access portable water, while 38% corresponding to 813,199 could fairly access portable water in 1993. However, coverage for safe drinking water between 1993 and 2002 in Edo-State is not significant at 95% confidence interval. In addition, 72% (2,009,566 population) did not have any access to sanitation; while 28% (777,210 population) had fair supply of sanitation. The regions with poor sanitation and water index are Etsako central, Etsako west, Esan west, Esan north-west, while Oredo, Akoko-Edo, Egor and Owan east have improved sanitation and water index. The results obtained also indicate widespread of water and sanitation related diseased in the State with the recorded highest cases of Schistosomaisis (134, 361:43%); Typhoid (81,981:27%); Cholera (62,191:20%) and Diarrhea (29,893:10%) respectively. Water harvesting is the major source of water supply in the Edo-state with 69.8% in Etsako West, 65.6% in Esan north East 65.5% in Etsako central while Oredo and Akoko-Edo had 5.9% and 4.3% respectively. Protected water supply from pipe borne water and borehole were noticeable in Oredo with 54.2%, 19.9% and Akoko-Edo with 5.2% and 6.0 respectively. The result on social sector expenditure shows that water and sanitation had least allocation of 18.4%, while Education, Health and Security had 23.5%, 37.0% and 21.1% allocation respectively. However, this research study concludes that serious attention should be given to water and sanitation sector for general growth, productivity and for the State to be on track with the attainment of meeting Millennium Development Goals on the sector by 2015.

Keywords: access water, sanitation, population, index, disease, portable water, demand, supply, coverage

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Climate Change on Discharge and Sedimentation of River Awara, Nigeria

Philipa O. Idogho, Olotu Yahaya, Alimi L.O.

The dynamics of variation in effect of climate change on discharges and sedimentation mechanism of River Awara is investigated using 14-year data of rainfall (mm), discharges (m3/s), temperature (0c) and sediment load (t). Surface runoff (mm) was computed using Water Balance Equation and some other empirical iteration based on the observed rainfall and temperature over a period of time. Analysis of Paired Sample reveals the relationship between tested hydrological variables: Rainfall-Runoff; Runoff-Sediment load; and Discharge- Sediment load are significant at 0.95 level of confidence interval. Logarithm calibration curve further illustrates that Rainfall-Runoff and Runoff-Sediment have coefficient values (R2) of 0.996 and 0.822 respectively. Analytical iteration shows that the intensity and duration of precipitation determine the magnitude of river, generation of surface runoff and sedimentation rate. Increase in rainfall depth by 100 mm within the 14-year has resulted to serious erodobility and erositivity around River Awara. Cumulative average sediment load ratio of 0.46 has significantly reduced the reservoir capacity of the river by 10%. 78% of total annual surface runoff is lost to ocean; since reservoir capacity has been silted up which in turns reduces the volume of water that could be held for storage, treatment and distribution for its intended purposes. Comparative physics-based output indicates that temperature increase of 0.70c between 1997 and 2004, due to internal processes of the Earth and some human activities. It is however projected that temperature will rise by 0.90c by the end of 2015. Projected rise in temperature will adversely affect hydrological cycle and complicate already scarce-water resources due to intensive evapotranspiration, infiltration and reduction in stream flow. Holistic integration using bottom-up mechanism needs to be applied to address this constraint. Dredging of river Awara is very important to enhance its storage capacity and planting well covered crop across the tributaries to trap sediment flow and reduce river siltation. Comprehensive adaptive measures are strongly encouraged to cope with multiple impacts of climate change in various human endeavors.

Keywords: Rainfall, Runoff, sediment, temperature, climate change, calibration, discharges, iteration, period, reservoir capacity

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Determination of Water Sensitivity Index in Estako- West and Esan Central, Nigeria

Philipa O. Idogho, Olotu Yahaya

As world population and industrial-agricultural outputs have increased, the use of water has accelerated. This development leads to extreme difficulty to provide sufficient safe drinking water in Etasko-West and Esan Central. Water sensitivity was measured in six major towns in Etasko-West and Esan Central. Water Measuring Indicators such as Water Poverty Index-Real Time (WPIr), Water Factor Value (WFV) and Access-Demand Factor (?) were applied to generate water sensitivity iterations. The outputs of these iterations show that Irrua has the fairest water supply and distribution with WPIr, WFA and ? index value of 0.22; 0.77 and 0.76, while Auchi and Ewu experience acute water shortage with the following index values: WPIr-0.43, 0.39; WFV-0.06, 0.16; and ?-0.64, 0.6 respectively. Results of One-Sample Test and Paired Sample Statistics show that the proportion of monthly income spent on portable water is significant at 0.95 confidence interval in all towns, except Auchi. Comparative analysis indicates strong relationship (R2=0.667) between the resources spent in procuring clean water and accessibility-demand ratio in the region. Private sector participation recorded highest investment value of 62% on water sector; government and corporate organization recorded 23% and 15% respectively. Since private sector determines the progresses of water sector, this accounts for the exorbitant tariff of 1, 500 N per m3 in this region. It is deduced that the most significant problems faced with water accessibility-affordability are transportation, finance and power supply with computed constraint index value of 47%, 40% and 13% respectively. Finally, Etasko-West and Esan Central are highly waterstressed. Government, corporate organization and private investors need to establish technically-based measures to ensure perfect accessibility and affordability of this scarce utility

Keywords: Water, Accessibility, Sensitivity, WPIr, Estako-West, Esan Central

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Effects of Pre-Treatment and Temperature on the Quality and Drying Rate of Tomatoes

R.A Iyanda, A.O Adeboye, K.A Yusuf

The effect of pre-treatment and temperature on the quality and the drying rate of tomatos (Lycopersicon esculentus) were studied. A 3× 5 factorial experiment in a randomized complete block (RCBD) design was used. Firm and fresh ripe tomatoes were washed and sliced to a uniform thickness of 5mm, pre-treatment by boiling for 3 minutes was given to some of the sliced tomatoes while some were blanched by soaking in water at 900C for 3 minutes and the remaining part was dried raw. 200g each of the sample was dried at temperatures of 50, 55, 60, 65, and 700C in a cabinet drier until no moisture removal was observed. The moisture removal from the samples in the cabinet was observed and measured on an hourly basis and the vitamin C content of the dried samples was also analyzed. The results obtained for the drying rate and Vitamin C content were statistically analyzed using SPSS software to generate the ANOVA and DNMRT. It was found that samples dried at higher temperatures had higher drying rates irrespective of the pre-treatment. Raw samples and Samples dried at lower temperatures had better quality in terms of vitamin C retention.

Keywords: tomato, blanching, boiling, drying

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A Statistical Comparison of Nine Rock Failure Criteria

Hasan Jamali, Adel Asakereh

Today the rock failure criteria have a wide range of usage for determining the stress conditions around underground structures and slope stability methods .In this study we examine nine different failure criteria by comparing them to published polyaxial test data (s1 >s 2 >s 3) for five different rock types at a variety of stress states. several article have published about this subject with different criteria and rock data currently. For this purpose we need a factor named Least Mean Standard Deviation Misfits. In this paper we used all of them and try to gather them and present general result. Result of this article shows that polyaxial criteria has more accuracy.

Keywords: Rock failure criteria, polyaxial test data, Misfits

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Influence of the Cutting Parameters on Vibration Level in Metal Turning

Zoltan Iosif Korka, Calin-Octavian Miclosina, Vasile Cojocaru

Cutting vibration is a phenomenon that often appears in the process of metal machining, being one of primary factors that affects the processing quality and limits the productivity enhances. The analysis of vibration in the cutting process became very important, because the vibrations may cause the damaging of the machine spindle, cutting tool, or workpiece and leave behind a poor quality machined surface. The present paper intended to study the influence of the cutting parameters on the vibration level of the tool in turning process of mild steel.

Keywords: metal cutting, vibration, cutting tool, cutting parameters

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A Review of Dynamic Models Used in Simulation of Gear Transmissions

Zoltan Iosif Korka, Ion-Cornel Mituletu

The investigation of relevant scientific literature regarding gear modeling enabled us to discover a significant number of papers dating back several decades and continuing to the present. The purpose of the dynamic models was quite diverse, but all modeling efforts share the goal of replicating the complex physics of power transmission through gear interaction. This paper investigates the relevant aspects regarding the dynamic modeling of gear transmissions, starting with the simplest model (1DOF), then developing it into a model with three degrees of freedom (3DOF) and finishing with six degrees of freedom model (6DOF).

Keywords: Dynamic model, simulation, gear transmission

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The Study of chemical Inhomogenety Formation in Cast Ingots

Cinca Ionel Lupinca, Constantin Marta, Cornelia Ecaterina Cornean

This paper presents a study of chemical inhomogeneity formation indirect casting of a 6 to ingot, using the AnyCasting software (Var.3.10, 2009). The ingot was obtained from steel with a medium content of carbon alloyed with chromium, molybdenum and vanadium, type 1.2344 (X40CrMoV51) (conf. DIN 17350), using the procedure of ingot mould gravity filling (direct casting). Such an ingot is subsequently subjected to a hot plastic deformation in order to obtain flat semifinished. The presence of these semi-finished of chemical inhomogeneities influences the behaviour of the ingot deformation.

Keywords: ingot, chemical segregations, gravity casting

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A Theoretical investigation on HC Mixtures as Possible Alternatives to R134a in Vapor Compression Refrigeration

Feiza Memet

This paper provides a theoretical comparison of the performance of refrigerants in use in a vapor comparison cycle. It is about the phase-out of R134a from actual refrigeration system, comparison being performed for this chemical and two more ecological mixtures: R290/R600a described as (30/70) and (40/60). Were investigated effects of condensation temperatures and evaporation temperatures on performance measures as COP (Coefficient of Performance) and VCC (volumetric cooling capacity). COP is a measure of the performance of the refrigeration cycle, while VCC is an indicator of compressor size. Results of this study will reveal that R290/R600a (30/70) is a good option when it is about substitution of R134a, from energy efficiency point of view, in terms of COP. R290/R600a (40/60) has VCC values bellow the ones of R134a, but comparable.

Keywords: evaporation, condensation, temperature, performance, compressor

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Key Performance Indicator of Building Maintenance and Its Effect on the Building Life Cycle

M.A. Othuman Mydin

Building maintenance is considered as one of the national agenda. Multitude barriers received by the services providers have undergone various difficulties in satisfying public interest have been progressively resolved as a sign towards becoming a more developed country. In real practice, building maintenance is the thing which we mostly tolerate. If the building is able to weather the elements, we may with delay taking action on it. Most buildings are always treated with ‘ad-hoc’ maintenance. In some instances, the building disrepair will wait until complaints are made before any repair work is done. It shows that the situation is not considered critical as it may. Maintenance is still being practiced in improper procedure by the maintenance managers which subsequently caused bad impacts to the facilities and the services provided. It can be seen that the managers prefer carrying out reactive maintenance works rather than proactive works and at times do not consider the clients satisfaction and also the performance of services. This paper will focus on some important elements of building maintenance and its relation to building performance holistically.

Keywords: building maintenance, building performance, disrepair, building defects, failure, asset management

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Connection in Joints for Thin-Walled Steel Sections and Sheeting

M.A. Othuman Mydin

Thin-walled cold-formed members are thin, this will give rise to behavioural phenomena, which are not usually encountered in the more familiar hot-rolled sections. When compared to hot-rolled steel sections, cold-formed thin-walled steel sections are more likely to fail in l ocal buckling, distortional buckling, various global buckling and shear buckling. This paper will discuss types of connection in Jjoints for coldformed thin-walled sections and steel sheeting. Bolts, screws, blind rivets or cartridge fired pins are commonly used in joints for coldformed thin-walled sections or steel sheet connections. Fasteners in light gauge steel tend to be relatively less stiff than their counterparts in heavier construction so that connection flexibility can be significant in certain assemblies. Furthermore, as in any load-bearing structure, it is i mportant that connections are not brittle and this implies that there should be adequate deformation capacity.

Keywords: connection, joint, steel, cold formed, sheeting, sections

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Human Factors in Fire Safety Management and Prevention

M.A. Othuman Mydin

Fire protection is the study and practice of mitigating the unwanted effects of potentially destructive fires. It involves the study of the behavior, compartmentalization, and investigation of fire and its related emergencies, as well as the research and development, production, testing and application of mitigating systems. Problems still occurred despite of the adequate fire safety systems installed. For most people in high-risk buildings, not all accidents were caused by them. They were more likely to be the victims of a fire that occurred. Besides damaging their properties and belongings, some people were burned to death for not knowing what to do if fire happens in their place. This paper will present the human factors in fire safety management and prevention system.

Keywords: fire safety, fire hazards, human, protection, compartmentalization, fire-fighting, evacuation

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Construction Waste Material Management and Logistic System

M.A. Othuman Mydin, Khor Jie Cheng

Construction is one of the industries that produces significant amount of waste. Construction site produces waste as a result of construction work. In the context of direct waste, it is a mixture of surplus materials arising from any kind of construction works, be it construction, site clearance, excavation, renovation or refurbishment. Construction waste consumes a large amount of natural resources and hence a strategic management is significant to reduce or manage construction waste. There are studies showing that waste represents a relatively high percentage of production costs. Previous researcher defined waste as the loss of any kind of resources produced by activities which generate direct or indirect costs and do not add any value to the final product from the point of view of client. The society’s concern has gone from the perspective of efficiency to the impact to the environment. It is undeniable that the waste generated has caused an impact to the environment. However, building waste can hardly be recycled as it may be highly contaminated in the process of production or assembly. Building materials and inventory on site will contribute to waste generation if not handled properly and systematically. This paper will discuss some important elements of construction waste and management such as waste material management, construction logistic system and generation of construction waste.

Keywords: construction, waste, management, building material

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A Path toward Safer Heritage Buildings through Excellent Fire Prevention and Control System in Malaysia

M.A. Othuman Mydin, Khaw Yen Yen

Fire prevention & control system by Fire Rescue Department Malaysia states that protection in the aspects of fire prevention, control and extinguishment for a certain area based on the availability of risks in that area. It is a practice of mitigating the unwanted effects of fires. Besides that, a fire safety system also includes the study of the behaviour, compartmentalisation, suppression and investigation of fire and its related emergencies. In protecting and preserving the historic fabric of the heritage structure there are some major differences which is a challenge for the architect and fire protection engineer in the application of general fire protection principles. The challenge in protecting heritage structure is to maintain their historical fabric while providing a reasonable level of safety for their occupants and contents. In order to avoid harming the building’s historic character, the architect and engineer will need to have the sensitivity and ingenuity approaches to provide fire prevention and protection measures that do not damage the historic fabric of the building. This paper focuses on path toward safer heritage buildings through excellent fire prevention and control system in Malaysia.

Keywords: fire prevention, control system, fire, building, passive protection, active protection

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Stochastic Analysis of Land Degradation on Edo State Agricultural System

Olotu Yahaya, Diamond Blessing, Dagona A.G, Morakinyo T.A.

Edo state, like many other states in Niger-Delta and Nigeria as a nation has resultant land and water degradation problems such as persistent oil spillage, erosion of arable land, sedimentation of dam and reservoirs. This research study investigates the effects of land degradation in all the local government areas in Edo state. The results of the findings indicated that 28% corresponding to 634,416.3 ha of arable land had totally been affected by soil erosion. Highest erodibility index of 0.75 was obtained at Estako west (Auchi), while least value of 0.1 was found at Akoko-Edo local government area respectively. Between 1976 and 1997, 1,820,410.50 barrels of crude oil spilled with maximum spill value 600,511.02 barrels in 1984 and minimum spill of 5,956 barrels in 1989. Reduction of cassava production was estimated and analyzed. The result showed that the reduction is highly significant at 95% confidence interval. Etasko -west had the highest reduction from 7.26 MT/HA in 1993 to 1.1 MT/HA in 2002. In addition, analysis of erosion and land degradation control expenditures showed that little attention has been paid to controlling land degradation in the state. Erosion control expenditure was increased from 4.1% in 1990 to 10% in 2002. This increase is not significant at 0.01 and 0.05 levels of significance. All these constraints affect agricultural production, human well-being, social and economic growth of the people in Edo state.

Keywords: degradation, land, erosion, spillage, index, state, hectare, expenditure

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Evaluation of Waterloss Impacts on Water Distribution and Accessibility in Akure, Nigeria

Olotu Yahaya, Bada Olatunbosun, Ehibor O.G., Ososomi A.S.

Safe drinking water is a necessity for life. Providing quality drinking water is a critical service that generates revenues for water utilities to sustain their operations. Population growth put an additional strain on the limited resources. The annual volume of water lost is an important indicator of water distribution efficiency, both in individual years, and as a trend over a period of years. Application of deterministic simulation model on public water supply variables reveals the volume of nonrevenue water (NRW) and its cost effects have further created a complex system for the availability, distribution and affordability of the utility. Gradual annual increase in public water supply (AWS) from 9.0 *106m3 to 14.4 * 106m3 had negative effect on annual water accessed (AWA) with R2 = 0.096; and highly significant with annual water loss (AWL) with R2 = 0.99. This development indicates that water loss mainly through leakages and bursts is a function of public water supply. Hence, estimated volume and cost annual revenue water (NRW) in Akure is 6 million m3 and 15.6 million USD respectively. Critical analysis shows that the lost annual revenue could be used to provide education and health services for a period of 6-month in the region.

Keywords: water, NRW, simulation, distribution, resources, public, cost

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Sensitivity-Based Modeling of Evaluating Surface Runoff and Sediment Load using Digital and Analog Mechanisms

Olotu Yahaya, Bada Olatunbosun, Rodiya A.A., Omotayo F.S.

Analyses of runoff- sediment measurement and evaluation using automated and convectional runoff-meters was carried out at Meteorological and Hydrological Station of Auchi Polytechnic, Auchi using two runoff plots (ABCDa and EFGHm) of area 2m2 each, depth 0.26 m and driven into the soil to the depth of 0.13m. Runoff depths and intensities were measured from each of the positioned runoff plot. Automated runoff-meter has a measuring accuracy of ±0.001l/±0.025 mm and rainfall depth-intensity was measured using tipping-bucket rainguage during the period of 14-month of experimentation. Minimum and maximum rainfall depths of 1.2 and 190.3 mm correspond to measured runoff depths (MRo) of 0.0 mm for both measurement approaches and 60.4 mm and 48.9 mm respectively. Automated runoffmeter provides precise, accurate and instantaneous result over the convectional measurement of surface runoff. Runoff measuring accuracy for automated runoff-meter from the plot (ABCDa) produces R2 = 0.99; while R2 = 0.96 for manual evaluation in plot (EFGHm). WEPP and SWAT models were used to simulate the obtained hydrological variables from the applied measurement mechanisms. The outputs of sensitivity simulation analysis indicate that data from automated measuring systems gives a better modelling index and such could be used for running robust runoff-sediment predictive modelling technique under different reservoir sedimentation and water management scenarios.

Keywords: runoff, sediment, intensities, modeling, rainfall, variables, runoff-meter

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Analytical Modelling of Rainwater Harvesting and Groundwater Resources in Auchi, Nigeria

Olotu Yahaya, Bada A.O., Egbor O.C., Adeniyi E.O.

Shortage in supply of water for potable and non-potable applications and exponential world population increase is a strong constrain to Human Development Index and social-economic advancement in Nigeria. ClimGen (Version 4.1.05) was used to simulate and create large dataset of annual rainfall depth. Generated average annual rainfall from 1430 mm to 1600 mm was subjected to varying roof plan surfaces of 250 m2; 500 m2; 1000 m2; and 2000 m2 respectively. Simulation analysis showed that an average of 5,300m3 of rainwater was harvestable and this value of water could only meet water demand of 170 people annually. The relationship of roof plan surface (RPS) and collected rainwater is very strong with R2= 0.84 and 0.95 respectively. Again, the volume of groundwater withdrawal increased from 12.4×104m3 to 32.7×104m3, this could only meet an annual water demand for 10,480 people representing about 6.2% of the population in Auchi. This development reveals that water supply from the alternative sources could not meet up to 6.3% of total water demand in Auchi and increasing water availability and accessibility to about 65% (31.3×105m3) coverage requires integrated rainwater harvesting system and technically-based groundwater exploration mechanism.

Keywords: potable, accessibility, rainfall depth, RPS, volume, demand, integrated

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Design and Development of Electro-Mechanical Twins Tipping Buckets Runoff-Meter

Olotu Yahaya, Alimi L.O, Rodiya A.A., Omotayo F.S.

Electro-mechanical tipping bucket runoff-meter was designed and developed to measure surface runoff water using locally-sourced components. The instrument consists of metallic-fabricated runoff plot area of 2 m2, depth 0.25 m and metal gauge of 3mm. The tipping operation was initiated by arranging the sensitive electro-mechanical components such digital micro-switch (SW1,SW2, SW3 and SW4), pair of open/close circuit breakers (No,Nc), electronic speed gear and circular rotating disc to a pair of twins buckets of runoff volume 0.141 liter capacity per bucket which corresponds to 0.25 mm runoff depth. The whole arrangement was powered by a 12V by 75 AH battery and the tipping processes was being recorded by the electro-mechanical data logger. The instrument has a measuring accuracy of ±0.001 liter per tip. It was calibrated to measure minimum and maximum runoff volume from 0.14l to 200 liters, these values correspond to 0.25 mm and 800 mm runoff depths respectively. Therefore, precise results obtained using the instrument could be used to establish strong database for measuring and storing accurate surface runoff data which in turn could be applied for hydrological modeling for sustainable water resources management and design of hydraulic structures.

Keywords: runoff, water, Micro-switch, Tipping bucket, Data logger, accuracy

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Poor Workmanship in Construction of Low Cost Housing

N.A. Othman, M.A. Othuman Mydin

Most defects in construction projects are due to human error. In other word, we can say that human error happened due to poor performance in workmanship during construction of a building. Poor workmanship in housing construction, and poor management and control of building contractors have contributed to the housing problem. According to research conducted by the Building Research Establishment (BRE), 90% of building failures are due to problems arising in the design and construction stages. These problems include poor communication, inadequate information or failure to check information, inadequate checks and controls, lack of technical expertise and skills, and inadequate feedback leading to recurring errors. The quality issues of low cost housing nowadays begin to arise as there are many complaints about defects in some of the building elements of the house. One of the causes of this condition is due to poor quality of workmanship during construction. This will affect the quality of life of occupants and also giving bad image of the parties involved in the construction of low cost housing. This paper will discuss some variables that related to the causes of poor quality of workmanship in construction projects and some common building defects found at low cost housing.

Keywords: building defects, workmanship, low cost housing, project management, poor quality

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A Comparative study about the Influence of Vibration on Elbow Joint Mobility

Radu Panaitescu-Liess

The results shown in [1] have referred to a particular appreciation of the elbow joint mobility of a subject to the action vibrations produced by a fitness device. Experiments - performed on four subjects - were held at the Institute of Research - Development - Innovation of the University "Transilvania" of Brasov and focused on the effects of vibrations on the joint mobility. This article represents a complement to the paper [1].

Keywords: mobility, elbow joint, vibrations

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Proposed an Optimal Search Algorithm to Find the Best Answer in a Question Answering Systems

Sasan Saqaeeyan, Mohsen Shakibafakhr, Mohsen Roshanzadeh

QA systems extract answers in natural language question from a large set of documents. In this paper, we will design and implement Restricted Domain QA System based on a knowledge database. In this system we will use a genetic algorithm and optimal-genetic algorithm to search in the knowledge base for finding the answers. Web pages are sources of knowledge system. To validate the proposed approach, we will implement these algorithms; results indicate a significant increase in accuracy of the proposed system compare to previous systems.

Keywords: Algorithms Optimal Genetic Algorithms, Question Answering Systems, Mutation, Crossover

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Slope Stability Analysis and Mitigation Measures in the Area of the Sighisoara Medieval Citadel

George-Catalin Silvas

The Sighisoara Medieval Citadel has a very big importance to the cultural, architectural and historical heritage of Romania. The citadel is situated on the Fortress Hill and it is the only inhabited fortress in Romania. But underneath the beauty of the Citadel lies some problems that only the inhabitants and the authorities know. These problems consist in the presence of the slope instability phenomenon. Throughout the years the slopes of the Fortress Hill, because of a series of factors, became instable. Thus landslides occurred that affected the Citadel fortress walls. There are still some areas of the walls that have never been reconstructed yet. So a slope stability analysis shall show if the slope instability phenomenon is still active and the mitigation measures recommended will stop the activity of this phenomenon.

Keywords: slope, stability, analysis, mitigation, citadel

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Effects of Structural Defects on Dynamic Behavior at Sandwich Composite Beams- Part I-Theoretical Approach

Tufoi Marius, Gilbert Rainer Gillich, Hatiegan Cornel, Mituletu Ion-Cornel, Vasile Iancu

This paper series presents an analysis regarding the dynamics of sandwich composite beams, embedded at one end, in order to highlight the effect of geometrical and material discontinuities upon the natural frequencies and damage location in sandwich panels and similar composite. In first part (Part I), analysis was performed with Euler-Bernoulli analytical method for determining the vibration modes and in second part (Part II), analysis was performed with numerical simulation in SolidWorks software. Finally, in the last section of the paper, is shown an example how to interpret the obtained results.

Keywords: beam, finite element, frequency, simulation, structure

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Effects of Structural Defects on Dynamic Behavior at Sandwich Composite Beams- Part II- FEM Analysis

Tufoi Marius, Gilbert Rainer Gillich, Hatiegan Cornel, Mituletu Ion-Cornel, Zoltan Iosif Korka

This paper presents results obtained by modal analysis on composite beam like structures in healthy and damaged state. The aim is to obtain damage “signatures” for all possible damage scenarios and to use these data to assess transversal cracks based on vibration techniques, by involving natural frequency shifts. The analysis was performed in SolidWorks software for a five-layer composite, 40 vibration modes being obtained by numerical simulations. An example how to interpret the results is shown in the last section of the paper.

Keywords: beam, finite element, frequency, simulation, structure

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Statistical Analysis of the Effects of Drying Temperature and Pretreatment on the Proximate Composition of Dried Matured Green Plantain (Musa Paradisiaca)

K.A. Yusuf, O.A. Adeboye, A.A. Adebayo

Drying has been identified as the efficient means of ensuring continuous food supply to the growing population of any country and to enable the farmers produce more high quality marketable products. In this study, the effects of drying temperature and pretreatment on the quality of dried mature green plantain (Musa paradisiaca) were studied using an electrically-powered cabinet dryer. The product was dried from an initial moisture content of 62% (w.b) to a moisture content of 11.9% (w.b). A factorial experiment in a Randomized Complete Block Design (RCBD) involving three levels of temperature (50, 60 and 700C); three levels of pretreatment (blanching, boiling and control) and three replications were used. The quality analysis of the dried samples at different level of drying temperatures and pre-treatments was carried out for protein, fat, ash and fibre content and the data obtained were statistically analyzed using SPSS 16.0 software to determine the level of significance among the treatment factors on the dried samples. The protein, fat and fibre content decreased with increase in temperature but the ash content increased with increase in temperature. In pretreatments, control had the highest protein content of 4.27% at 600C, lowest fat content of 2.26% at 700C and moderate fibre and ash contents of 0.68% and 1.82% respectively at 600C. Boiled sample also had the highest fat content of 4.27% at 500C, lowest fat content 2.26% at 700C and moderate fibre and ash contents of 0.88% and 1.73% respectively at 600C. lastly, blanched sample had the highest fat content of 4.11% at 500C, lowest fat content 2.54% at 700C and moderate fibre and ash contents of 0.83% and 1.45% respectively at 600C.

Keywords: plantain, pre-treatment, drying, temperature

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Energy Performance of Eco-friendly R152a and R600a Refrigerants as Alternative to R134a in Vapour Compression Refrigeration System

Bukola Olalekan Bolaji, Zhongjie Huan, Francis Olusesi Borokinni

In this study, the energy performance of eco-friendly refrigerants (R152a and R600a) was investigated theoretically as alternative to R134a in refrigeration system. The results showed that the vapour pressure and specific volume of R152a are very close to those of R134a. R152a emerged as the most energy efficient with average Power Per Ton of Refrigeration (PPTR) of 10.6% less than that of R134a. R152a also exhibited higher Volumetric Refrigerating Capacity (VRC) and Coefficient of Performance (COP) than both R600a and R134a. The average COPs obtained for R152a and R600a were 13.4% higher and 5.4% lower than that of R134a, respectively. Generally, R152a performed better as R134a substitute in that it has the lowest PPTR, highest thermal conductivity, refrigerating effect, VRC and COP.

Keywords: alternative refrigerants, eco-friendly, energy, performance

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Anul XXI (2014), Nr. 2




The Hermetic Synchronous Engines for Pumping the Aggressive Liquids

Tudor Ambros, Marcel Burduniuc

The paper covers brief information about asynchronous and synchronous engines used for driving centrifugal pumps. It is argued the fact that asynchronous engines do not, actually, satisfy the requirements for hermetic engines designed for pumping radioactive and chemical liquids, because they possess low technical and economic indexes. Modification of rotor construction of these engines gives the possibility to increase these indexes. The shortcut rotor was replaced with a ferromagnetic rotor in hermetic asynchronous engine serially produced and permanent magnets had been inserted into its body. Different synchronous engine constructions with permanent magnets had been analyzed and developed, which operating characteristics had been compared with those of the asynchronous one.

Keywords: hermetic motors, permanent magnets, protection cylinders, synchronism, magnetic field image

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EInfluence of Starting Cage Material upon Dynamic Behaviour of Reluctance Synchronous Motors

Sorin Enache, Aurel Campeanu, Ion Vlad, Monica-Adela Enache

In this paper there is studied the dynamic regime behaviour of a reluctance synchronous motor fitted out with a starting cage. There are analyzed two concrete situations: cage made of aluminium and cage made of copper. There are presented the mathematical model of the motor, the simulation program and the simulations carried out for the two situations. For the case of cage made of aluminium there have been performed experimental tests for direct-on-line no-load starting, tests that confirm the simulations carried out. The paper ends with conclusions regarding the influence of the cage material upon the timedependent variation of the main electrical and mechanical quantities of the motor.

Keywords: reluctance synchronous motor, mathematical model, simulations, experimental tests

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Utility of Numerical Methods in Establishing Performances of Low Power Synchronous Motors

Ion Vlad, Aurel Campeanu, Sorin Enache, Monica-Adela Enache

In case of electromechanical equipments driven by alternating current motors, it is possible to reduce the exploitation costs by choosing correctly the driving motor (asynchronous motor or permanent magnet synchronous motor). One of the objectives followed in this paper is the comparative approach from the view point of operation performances and exploitation cost obtained for the two types of motors (asynchronous motor and the permanent magnet one), with the help of some specialized computation soft-wares. The utilization of a permanent magnet synchronous motor, which has an efficiency increased with 11.2% and the power factor better with 10.6%, is a solution for reducing the exploitation cost and for preserving the drive performances.

Keywords: AC machines, modeling, simulation

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Influence of Stator Winding Resistance upon Maximum Torque of Reluctance Synchronous Motors

Monica-Adela Enache, Gheorghe-Eugen Subtirelu, Niculae Boteanu, Mircea Dobriceanu

In this paper there is studied the dynamic regime behaviour of a reluctance synchronous motor fitted out with a starting cage. There are analyzed two concrete situations: cage made of aluminium and cage made of copper. There are presented the mathematical model of the motor, the simulation program and the simulations carried out for the two situations. For the case of cage made of aluminium there have been performed experimental tests for direct-on-line no-load starting, tests that confirm the simulations carried out. The paper ends with conclusions regarding the influence of the cage material upon the timedependent variation of the main electrical and mechanical quantities of the motor.

Keywords: reluctance synchronous motor, stator resistance, maximum torque, angular characteristics, experimental tests

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Investigation on Self-Organization Processes in DC Generators by Synergetic Modeling

Ion Voncila, Madalin Costin, Razvan Buhosu

In this paper is suggested a new mathematical model, based on which it can be justified the self-excitation DC generators, either shunt or series excitation, by self-organization phenomena that appear to overcome threshold values (self-excitation in these generators is an avalanche process, a positive feedback, considered at first glance uncontrollable).

Keywords: DC generators, synergetic modeling, self-organization processes, self-excitation non-linear dynamics

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Topology Optimization of Switched Reluctance Motors to Increase Energy Efficiency

Ion Voncila, Razvan Buhosu, Madalin Costin

This paper proposes - and analyses in comparison – new topologies for switched reluctance motors (armature rotor thereof). The aim is to find a topology that minimizes losses and maximizes the torque developed by the SRM. For purposes of comparative analyse it is used PSIM software. Based on the results, conclusions are drawn regarding the design strategies of this type of electric machines in the near future.

Keywords: SRM, torque ripple, energy efficiency

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Considerations Regarding the Opportunity of Using Psychological Techniques to Stimulate Solutions Characterized by Novelty and Inventive Step in TISR Transformers and Electric Motors with Shorted Moving Coil

Dan Stefan Georgescu, Mihaela Poienar, Ovidiu – Magdin Tanta, Adrian Neculai Romanescu, Elena Daniela Olariu, Dorel Cernomazu

This paper presents the appreciations and contributions regarding the use of psychological techniques to stimulate technical creativity with special reference to consonant association technique and inversion technique. The study is performed in the field of TISR transformers and electric motors with limited movement, starting from the analogy between a transformer and an electric motor with shorted coil. It approached a particular aspect of inversion technique in relation with the transformation of negative effects and results of laws, phenomena and processes into useful applications. The matter reffered to is related to the question: ,,why disadvantages and no advantages ?". At the end of the paper are presented and discussed some experimental models produced and studied by the authors in the Research Laboratory of Machines, Equipment and Drives at the University of Suceava and are exposed conclusions drawn from the experimental study and directions for future research.

Keywords: iinversion technique, consonant association technique, electric motor with shorted mobile coil, electric motor with limited movement

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Contributions to the Transient Study of an Electric Motor with Shorted Moving Coil

Daniel Georgescu, Nitan Ilie, Ovidiu – Magdin Tanta, Mihaela Poienar, Dorel Cernomazu

In this article is studied the transient regime of an electric motor with a shorted moving coil, into alternating current supplied. The authors present their contributions related to the conceiving, achieving and testing of experimental stands of an electric motor with a shorted moving coil and to the identification of the mathematical model, indexical function parameters and the coefficients of the mathematical equation of this engine. Finally, the authors' conclusions are presented on the results of experimental studies and moving coil motor behavior in transient regime.

Keywords: electric motor with shorted moving coil, indexical function, transient regime

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Particular Matrix in the Study of the Index Hour Mathematical Model

Mihaela Poienar, Dan Stefan Georgescu, Ovidiu – Magdin Tanta, Nitan Ilie, Elena Daniela Olariu, Dorel Cernomazu

The three phase transformer clock hour figure mathematical model can be conceived in his regular form as a 3X3 square matrix, called matrix code, or as a matrix equation, called code equation and is conceived through the elementary matrices: Ma, Mb, Mc or by defining matrices: M100, M10, M1. The code equation expression is dependent on the definition function: the sgn function or the trivalent variable function. Interrelated with the two possibilities are shown, defined and explained the following particular matrix: transfer matrix T. Finally are presented the interrelation between these particular matrixes and highlighted the possibilities of exploitation.

Keywords: clock hour figure, mathematical model, particular matrix

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Considerations Concerning Matrix Diagram Transformations Associated with Mathematical Model Study of a Three-phase Transformer

Mihaela Poienar, Dan Stefan Georgescu, Ovidiu – Magdin Tanta, Nitan Ilie, Elena Daniela Olariu, Dorel Cernomazu

The clock hour figure mathematical model of a threephase transformer can be expressed, in the most plain form, through a 3X3 square matrix, called code matrix. The lines position reflect the modification in the high voltage windings terminal and the columns position reflect the modification in the low voltage winding terminal. The main changes on the transformer winding terminal are: the circular permutation of connection between windings; terminal supply reversal; reverse direction for the phase winding wrapping; reversal the beginning with the end for a phase winding; the connection conversion from N in Z between phase winding or inverse. The analytical form of these changes actually affect the configuration of the mathematical model expressed through a transformations diagram proposed and analyzed in two ways: bipolar version and unipolar version (fanwise). In the end of the paper are presented about the practical exploitation of the transformations diagram.

Keywords: clock hour figure, transformation diagram, mathematical model

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Current State of Research at the EMAD Research Centre from „Stefan cel Mare“ University in Connection with Actuators and Solar Motors with Solid Heating Medium

Adrian Neculai Romanescu, Ovidiu – Magdin Tanta, Mihaela Poienar, Nitan Ilie, Constantin Ungureanu, Leon Mandici, Dorel Cernomazu

Within the EMAD Research Center of the USV have been developed since 1996 a number of solutions in heliothermic actuators and motors area made on the basis of solid heating medium. The solutions relates to rotary actuators and motors as well as linear actuators with limited movement. Are presented the primary constructive solutions with the peculiarities and finally, the general conclusion regarding the experimentation and practical implementation.

Keywords: thermo bimetal, shape memory material, heliothermic actuators and motors

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New Aspects Concerning the CEUS Figures Identified at Ferrofluid Utilisation in Rotating Magnetic Field

Ovidiu – Magdin Tanta, Mihaela Poienar, Adrian Neculai Romanescu, Mihaela-Brandusa Negru, Dorel Cernomazu

Within the EMAD Research Center was initiated researches about CEUS figures obtained by exposing the content of a cylindrical container on the progressive action of the magnetic field produced by a special winding associated with GROSU stator. Inside the recipient was stored a quantity of ferrofluid which surface were scattered gold or bronze particles. The assembly thus obtained was studied using a suitable video camera, obtaining the so-called CEUS figures that constitute true stamps that highlight and identify the particularities of the studied types of electric drives.

Keywords: Ferrofluid, CEUS effect, rotary field

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Contributions Concerning the Clock Hour Figure Utilization for the Power Transformer Diagnostic

Cristina Prodan, Mihaela Poienar, Ovidiu – Magdin Tanta, Adrian Neculai Romanescu, Dan Stefan Georgescu, Dorel Cernomazu

The paper is based on a study for the diagnosis of power transformer through the signal configuration that are part of the clock hour figure code for a defect transformer. The investigations made have the purpose to compare the code signal before and after the transformers damage. The comparative analyzes of the signal form, course and polarity are constituted in diagnosis criteria and are formulated the conclusion about the defect location, nature and dimension.

Keywords: clock hour figure, three-phase transformer, CEUS matrix, direct current supply method

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Application of Finite Element Method to Determine the Performances of a Permanent Magnet Synchronous Motor for Driving a Bicycle

Nicolae Diga, Constantin Ghita, Silvia-Maria Diga, Dorinel Constantin, Maria Brojboiu

In this paper, the authors present a case study in which was analyzed by finite element method a permanent magnet synchronous motor for driving a bicycle using the analysis and simulation software ANSYS Electromagnetics Low Frequency of ANSYS Inc. Company. Modelling and simulation with ANSYS ® Maxwell 2D of electromagnetic field in the studied motor was conducted for different initial positions (internal angle rotor-stator configured (set)) d1. It was identified the internal angle for which the performances of PMSM are very close to those obtained by computation.

Keywords: AC motor drives, electromagnetic fields, finite element methods, permanent magnet motors, software packages

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On the Magnetic Flux Density Analytical Calculation in the Air-Gap of Electric Machines with Wide Open Slots

Alina Cristina Viorel, Ioan-Adrian Viorel, Larisa Strete

The magnetic flux density distribution in the air-gap of electric machines with wide open slots is discussed in the paper. The finite element methods (FEM) obtained results are compared with that calculated analytic estimations. The case of double sided slotted machines with large values of the slot to opening tooth pitch ratio is considered, interesting conclusions being draw.

Keywords: double slotted electric machines, air-gap flux density

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New Adaptive Observer for Sensorless Induction Motor Drives

Olimpiu Stoicuta, Teodor Pana

The paper deals with a new type of observer for the rotor flux and speed of the induction motor. The new observer is designed to be used within a speed sensorless direct rotor field oriented control of induction motors. In order to present the performances of the new observer, it was compared to extended Luenberger observer. The comparative analysis was simulated using Matlab – Simulink – dSPACE platform.

Keywords: induction motor drives, adaptive observers, simulation

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Teaching Platform for DC Electric Drives

Ioan-Dragos Deaconu, Aurel-Ionut Chirila, Valentin Navrapescu, Anca-Simona Deaconu

This paper describes an educational platform for teaching DC electric drives. The drive has as objective an efficient system for controlling the speed of a DC motor driven by a chopper. The chopper is manufactured using metal oxide semiconductor field effect transistors for low power consumption and high switching frequency. The control part is performed using the LabVIEW environment, thus allowing for monitoring of the main signals such as voltages, currents and speed. The applied principles and the obtained results are also shown.

Keywords: Control engineering education, DC motor drives, DC-DC power conversion, Educationn

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Rotor Pole Pitch Factor Influence on the Operation Parameters of a 9/10 Pole Permanent Magnet Synchronous Machine

Lazar Florin, Alecsandru Simion, Leonard Livadaru, Ovidiu Dabija

The present paper is aimed to determine the pole pitch factor influence on the operating parameters for the considered structure. Transient analysis is used to obtain the results for each of the studied pole pitch factor. The results concern the cogging torque values, the back EMF, medium torque and torque ripple values.

Keywords: permanent magnet machines, finite element methods, rotating machine transient analysis, torque

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Practical Platform for Open and Closed Loop Speed Control of an Inverter Driven Asynchronous Machine Used for Teaching Purposes

Dan Claudiu Rus, Stefan Matis, Ioan Iov Incze, Iulian M.T. Birou

The paper presents a laboratory setup based on a SIMOVERT MASTERDRIVES MC Inverter from SIEMENS used for open and closed loop speed control of an induction machine. The platform allows four quadrant operation of the machine using both the classical V/Hz scalar principle and field oriented vector control principle. The rectifier unit consists of a classical three phase diode bridge and two high voltage capacitors in order to obtain a voltage source behavior of the converter. In order to obtain the four quadrant operation of the drive, several methods are investigated out of which one is proposed and implemented. The theoretical aspects of V/Hz scalar principle and field oriented vector control principle are better explained using the proposed experimental platform.

Keywords: electrical braking, voltage source inverter, educational platform

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Researches Regarding the Factory Test of Electric High-duty and High voltage Equipment Used for Teaching Purposes

Aurel Campeanu, Gheorghe Liuba, Ion Piroi, Ladislau Augustinov, Elisabeta Spunei

This paper shows a review of the present methods of testing the highduty and high voltage electric machines and transformers, to which the authors brought their own contributions concerning their elaboration and exploitation. We have especially presented the methods which make possible the concluding heating tests in factories and the elimination of the eventual errors which can occur at the installation place.

Keywords: AC machines, heating test, simulation

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Comparative FEM-based Analysis of Multiphase Induction Motor

Leonard Livadaru, Cristian Nutescu, Adrian Munteanu, Alecsandru Simion, Margareta Cojan

This paper presents a comparative study of multiphase induction motor, which has alternately three-, five- and six-phase stator winding. The machine has been designed particularly for this purpose and has individual ring coils placed in each stator slot. The study consists in FEM analyses and mainly looks for the particularities of magnetic quantities such as air-gap flux density and electromagnetic torque.

Keywords: multiphase induction motor, FEM analys

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A MATLAB Graphical User Interface Dedicated to the Optimal Design of the High Power Induction Motor with Heavy Starting Conditions

Virginia Ivanov, Maria Brojboiu

In this paper, a Matlab graphical user interface dedicated to the optimal design of the high power induction motor with heavy starting conditions is presented. This graphical user interface allows to input the rated parameters, the selection of the induction motor type and the optimization criterion of the induction motor design also. For the squirrel cage induction motor the graphical user interface allows the selection of the rotor bar geometry, the material of the rotor bar as well as the fastening technology of the shorting ring on the rotor bar. The Matlab graphical user interface is developed and applied to the general optimal design program of the induction motor described in [1], [2].

Keywords: induction motor, optimization, Matlab GUI

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Assessment of Electromagnetic Stress in a Permanent Magnet Synchronous Machine with Commutable Poles

Madalin Costin, Ion Dobrota, Ion Voncila, Ion Paraschiv

The permanent magnet synchronous machine is an adequate solution in a large range of power in high performance electrical drives and energy conversion systems. In this paper has been assessed the permanent magnet synchronous machine electromagnetic stress for the case of stator winding with commutable poles. Based on simplified assumptions, an analytic relationship of the dependence of electromagnetic stress has been obtained. Numerical simulation performed for a case study confirms the validity of the theoretical approach developed.

Keywords: permanent magnet synchronous machine, electromagnetic stress, commutable poles, design

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Modernization of the Grinding Electromechanical Drive System of the Automated Coffee Machine

Ilie Nuca, Adrian Turcanu

The paper refers to espresso coffee machines high quality and some possibilities to increase the level of automation and productivity. Existing machines require manual adjustment of coffee grinder depending on the quality of coffee beans. To eliminate this flaw has been developed and implemented an adjustable electromechanical system with DC servomotor and numerical control of coffee grinder. Computer simulation results demonstrate the functionality of the proposed electromechanical drive system of the coffee grinder.

Keywords: coffee machines, electromechanical system, DC servomotor, numerical control

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On the Optimal Selection of Electrical Machines Fans

Madalin Costin, Ion Dobrota, Ion Voncila, Marcel Oanca

In this paper an analytic relationship for electrical machine fan design has been developed. In the particularly case of salient poles synchronous machine (with salient poles – for electromagnetic field excitation or surface mounded permanent magnet), this approach allowed to express the fan power as a function of machine middle axe air gap. This analytic foundation developed may leads to different optimization criteria as specific active materials or costs. Numerical simulations confirm our approach.

Keywords: PMSM, thermal flow, fan, design

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Alternative Design Relationship of Inner Diameter for Fault Approach of Salient Poles Synchronous Machine

Ion Dobrota, Madalin Costin, Ion Voncila, Marcel Oanca

In this paper an alternative relationship of inner diameter for design computing on salient poles synchronous machine that take into account fault approach, has been developed. This approach is based on the finding of a dependence of inner diameter by relative reactive drop voltage. Numerical simulations for a concrete case study of salient poles synchronous machine prove the work developed.

Keywords: fault approach, salient poles synchronous machine, inner diameter, design

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The Use of Current Generators in Electrical Converter Drives for Stepper Motors

Emanoil Toma

This paper presents some ways to realize electrical converters for stepper motor drives. The first part analyzes aspects for unipolar stepper motor and use of constant current generators. The second part present current sources based on peak limiting current trough the inductance of motor coil. A complete drive module for bipolar stepper motor was conceived and simulation results confirm their functionability.

Keywords: current limiting, micro-stepping, Pspice simulation

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dSPACE Implementation of the Third Harmonic Insertion based Modulation on the Three Phase Power Inverter

Marian Gaiceanu, Cristian Nichita

This paper shows the implementation of real-time modulation based on the third order harmonic insertion in three-phase power inverter. Two methods of implementation have been proposed. As a working methodology the mathematical model of the duty cycles of the threephase power inverter have been designed and implemented in Matlab/ Simulink®. By an adequate design the appropriate ControlDesk interface send the adequate signals to power inverter and collect all the necessay data to be viewed. Harmonic analysis has been performed. The advantages of using this type of modulation are highlighted.

Keywords: power inverter, Matlab Simulink, dSpace, third harmonic insertion

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dD.c.-d.c. Converter Controlled by Optic Fiber Channels

Marinel Popescu, Costel Caramida, Catalin Boltasu

The using of optic fiber is recommended in environments with intense electric and magnetic fields to send the control and measuring signals. The paper presents the structure of a simple d.c.-d.c. converter used to control the energy transfer of a large inductance coil. The closed loop control system requires two optic fiber links to send feed-back analog signal, respectively digital control signal for controlled semiconductor device. Also, the paper presents the drivers adapted to this type of control and waveform recorded during tests.

Keywords: optical link, d.c. converter, driver, semiconductor device

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The Command by GSM for positioning Systems of Anti-hail Ramps

Gheorghe Manolea, Florin Ravigan, Alexandru Novac

The points of anti-hail missiles are the technical stations distributed being often isolated from the viewpoint of power systems and communication channels. The solution that can be used to achieve communication with these stations is based on mobile network infrastructure which could be used to transport data packets useful.

Keywords: communication, mobile networks, anti-hail, modem

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Control System for Producing Electricity with Dual Stator Winding Cage-Rotor Induction Generator

Lucian Nicolae Tutelea, Sorin Ioan Deaconu, Gabriel Nicolae Popa

This paper will present the key design equations and control design model of the Dual Stator Winding Cage-Rotor Induction Generator (DSWIG) to achieve wide-speed-range operation with reduced capacity of the static power controller for low power wind or hydro applications. The proposed induction generator consists of a standard squirrel-cage rotor and a stator with two separate windings wound for a similar number of poles. Moreover, the system control strategy using the stator flux orientation is consequently proposed. The aim of the paper is to emphasize that the low speed induction generators with power electronic converters represent a realistic and useful solution for direct drive power applications.

Keywords: dual stator winding, induction generator, active rectifier (inverter, control design, low speed

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Some Aspects Regarding the Use of Digital Signal Controllers in Electrical Drivers for Stepper Motors

Emanoil Toma

In the first part of this paper are presented and compared two practical implementation of unipolar stepper drives for didactical destination, one with 8 bit microcontroller and one with 16 bits digital signal controller. In the second part, a practical implementation of micro stepping drive for bipolar motor with a 16 bits digital signal controller designed for switching mode power supply. A physical prototype was realized and some experimental measurements are presented.

Keywords: micro-stepping, peak current limiting, MOSFET H-Bridge

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The command of the Flour Transport Pumps in a Cereal Mill with PLC Siemens S7-1200

Eugen Raduca, Marius Schmidt, Dan Ungureanu-Anghel, Mihaele Raduca, Cornel Hatiegan, Nicolina Pop,, Florica Novacescu

This paper presents pump control with PLC Siemens Simatic S7 - 1200, for transporting flour designed to be implemented in the Pfalzmühle Mannheim. The order was designed to replace the old system made in various traditional contacts and relays. Programming PLC Simatic S7 - 1200, which is a powerful and reliable, a new generation, was conducted in FBD. In order to verify the accuracy and to optimize the operation of the control system was built a functional model.

Keywords: command, PLC, algorithm, FBD, experimental model

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A Solution to Study Different Homing Methods Using a PLC

Mihai Rata, Adrian Graur, Leon Mandici, Gabriela Rata

In a positioning control with stepper motors it is very important to know zero location. For this purpose it is necessary a homing command. This paper presents a solution that allows the study of different methods implemented to find a home position (also called: zero point) and to observe the differences between these methods.

Keywords: position control, stepper motors, educational technology, automation

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Speed Digital Control of Brushless DC Motor Using dsPIC Controller

Gheorghe Baluta, Gheorghe Ursanu

This paper presents the digital control of the Brushless DC motor (BLDCM) speed. The dsPICDEM MC1 development system (with the dsPIC30F6010A microcontroller) and the dsPICDEM MC1L power module, manufactured by Microchip Company, were used. The control program was developed in C programming language. The graphical user interface was realized in LabVIEW 8.6 graphical programming language. For speed control, a digital controller PI type was implemented. Due to digital controller well chosen and well tuned, the system response at speed step variation is very good. Therewith, the experimental results obtained also show a good compensation of disturbance which does not happen in open-loop control.

Keywords: brushless machine, microcontrollers, digital control, speed control

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Command and Running of an Experimental Model Vehicle for Covering a Labyrinth Type Runway

Eugen Raduca, Adrian-Florin Paun, Mihaela Raduca, Cornel Hatiegan, Silviu Draghici,, Cristian Rudolf, Lenuta Candea

The paper presents the command and running of an autonomous vehicle - experimental model – for covering a labyrinth type runway. The command is realized with a Micro Arduino type platform and the running with two mini engines of continuous power, each coupled to a tire. The program has been written in C++.

Keywords: command, running, vehicle, experimental model, C++

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Design and Control of the Electric Drive of the Anti- Hail Launching System

Gheorghe Manolea, Sergiu Ivanov, Laurentiu Alboteanu, Constantin Sulea, Stefan-Marian Nicolae

In the present, the Romanian anti-hail launchers are manually operated. This means that the positioning of the launcher on the two directions (azimuth and elevation) are adjusted based on the commands, by the human operator. The paper describes the design, implementation and experimental results of the electric drives of the two axes by using permanent magnets synchronous motors (PMSM) supplied by smart drives. The solution offers the possibility of automation and integration of the anti-hail launchers within intelligent systems.

Keywords: anti-hail, design, PMSM drive

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Design and Control of the Swing Gates with Implementation of Multiple Command Systems

Ciprian Afanasov, Leon Mandici, Rata Mihai

The paper presents a drive system for a swing gate. The control of opening and closing of the gate was made in different ways: sound control, control by changing the light flux, control by overload protection, control by laser barrier, remote control and control from central panel. The gate is driven with a single motor which drives a mechanical motion transmission system. The drive system is controlled by a programmable smart relay.

Keywords: swing gate, drive system, sound control, smart relay

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Regarding the NVH Behaviour of the more Electric Vehicles. Study Case of a Small PM Motor

Florin Lazar, Dorin Lucache, Alecsandru Simion, Paul Borza, Leonard Livadaru

The noise and vibration behaviour of electric and hybrid vehicles is dramatically different from conventional vehicles. The noise and vibration mechanisms of the individual components (combustion engine, electric motor, transmission etc.) are known in principle, but an electric or hybrid powertrain features additional and different components as well as new operation modes compared to a conventional powertrain. This results in new interactions which are uncommon in this form for conventional vehicles. In the case of the electric traction, the electric motor becomes an important noise and vibrations source. Depending on the design of the motor, the electromagnetic (EM) pulses and corresponding torque pulses from the motor can be very strong. These can be radiated as noise directly from the motor housing and can also be transmitted structurally to the support structure through the motor mounts. However, the EM forces are generally lower than the combustion and reciprocating mass forces of an IC engine, and significantly, they are at a much higher frequency. On the other side, the electric drives are quite numerous in cars. Lot of smaller motors are involved in X-by-wire systems or other comfort oriented systems. As a study case, the paper is focused on the NVH produced by a 0.25kW PM motor.

Keywords: noise, vibrations, electric motors.

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Anul XXI (2014), Nr. 3




A New Method for Modeling and Control of Hybrid Stepper Motors
George Mihalache, Gheorghe Livint, Vasile Horga

Over time the mathematical models of the hybrid stepper motors (HSM) have been developed in various forms. In this paper we propose to use for HSM a model of a two-phase synchronous machine with permanent magnet in which the number of pole pairs is equal to the number of rotor teeth of the HSM. It analyzes the behavior of hybrid stepper motor controlled in open loop. Control signals are obtained by implementing the control sequences:one-phase-on, two-phases-on, half step.

Keywords: hybrid stepper motor, mathematical model, one-phase-on, two-phases-on, half step

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Optimal Control of an Electrical Drive System with Variable Torque
Corneliu Botan, Florin Ostafi

The optimal control from the energetic point of view of the transient state of electrical drive systems is presented. A step variation of the load torque in the optimization interval is considered. The performance criteria consider only Joule losses, since they significantly overcome other ones in the transient state. The paper refers to a structure with voltage control of the drive. The study is performed in continuous time domain for a fixed end point problem.

Keywords: motor drives, variable load torque, linear quadratic optimal control, fixed end point

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Current Control of the Single-Phase Full-Bridge Power Inverter
Marian Gaiceanu, Razvan Buhosu, Gelu Gurguiatu, Ciprian Daniel Balanuta

This paper shows the Matlab/Simulink implementation of the current control in a single phase full-bridge power inverter. In order to increase the performances of the power inverter an LC filter is connected at the input. Mathematical modelling of the power inverter is based on the switching functions. Unipolar asymmetric PWM modulation method, and hysteresis current control will be analyzed for a connected RL load to power inverter output. Simulation results based on the Matlab/Simulink® control implementation are shown.

Keywords: power inverter, Matlab Simulink, single-phase, asymmetric PWM, unipolar

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Flywheel Energy Storage Drive System for Wind Applications
Marius Constantin Georgescu

This paper presents a wind small power plant with a Smart Storage Modular Structure (SSMS), as follows: a Short Time Storage Module (STSM) based on a flywheel with Induction Motor (IM) and a Medium/ Long Time Storage Module (MLTSM) based on a Vanadium Redox flow Battery (VRB). To control the speed and torque of the IM are used a nonlinear sensorless solution and a direct torque solution which have been compared. Now, the author proposes to replace the IM by a dc motor with permanent magnet energy injection. In this aim, are accomplished some laboratory tests.

Keywords: flywheel, induction motor, magnetic device, wind energy

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Study on the Identification of an Actuator
Ioan Ruja, Elisabeta Spunei, Constantin Marta, Ion Piroi, Monica Rosu

The paper presents the results obtained from the study conducted on an execution element in view of its modelling and identification. The mathematical model obtained from the studied execution element constitutes the basic information serving to the design of the adjustment algorithm of the automatic system where the actuator will be introduced, as well as the establishment of the technical parameters of the static converter for the supply of the electric motor.

Keywords: actuator, identification, transfer function, modelling, indicial response

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Monitoring System Dynamic Regimes with Variable Reluctance Synchronous Motors
Gheorghe-Eugen Subtirelu, Mircea Dobriceanu, Adela-Monica Enache, Niculae Boteanu

This paper will present an overview of how can we use a data acquisition (DAQ) device to quickly and easily acquire and present the data of dynamic regimes of variable reluctance synchronous motors. The described monitoring system is built from two principal parts: hardware component (LEMs transducer for measurement voltages and currents, supply voltage, elements for signals conditioning and start command, USB multifunction I/O module); software component based on the industry standard Lab VIEW graphical development environment. The command for synchronization of start acquisition and start motor is on the front panel of data acquisition virtual instrument. The values of data acquisition are displayed numerically and graphically.

Keywords: adata acquisition, power system monitoring, voltage measurement

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Integrated Photovoltaic System Used as an Alternative Power Source
Ionel Laurentiu Alboteanu, Gheorghe Manolea, Florin Ravigan

This paper presents a solution to use solar energy as an alternative source of electricity to conventional sources. The solution is to use a compact photovoltaic system integrated into a micro smart grid. The studied photovoltaic system is used into concrete application for the power supply lighting in a didactic laboratory.

Keywords: photovoltaic system, lighting, monitoring, alternative power source, smart grid

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Integrated Photovoltaic System Used as an Alternative Power Source
Ionel Laurentiu Alboteanu, Gheorghe Manolea, Florin Ravigan

This paper presents a solution to use solar energy as an alternative source of electricity to conventional sources. The solution is to use a compact photovoltaic system integrated into a micro smart grid. The studied photovoltaic system is used into concrete application for the power supply lighting in a didactic laboratory.

Keywords: photovoltaic system, lighting, monitoring, alternative power source, smart grid

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On-line Identification of the DC motor Parameters by using Least Mean Square Recursive Method
Marian Gaiceanu, Razvan Solea, Bogdan Codres, Cristinel Eni

The on-line least square parameters (electrical and mechanical) identification method of the separately DC motor is presented in this paper. The parameters of the DC machine are time dependent; therefore, for the DC drive control the on-line parameters identification procedure is mandatory. By knowing accurately the DC motor parameters, the parameters of the DC speed and current cascade controllers can be obtained.

Keywords: DC motor, least mean square, identification, recursive

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System for Monitoring and Analysis of Vibrations at Electric Motors
Gabriela Rata, Mihai Rata

The monitoring of vibration occurring at the electric motors is of paramount importance to ensure their optimal functioning. This paper presents a monitoring system of vibrations occurring at two different types of electric motors, using a piezoelectric accelerometer (ICP 603C11) and a data acquisition board from National Instruments (NI 6009). Vibration signals taken from different parts of electric motors are transferred to computer through the acquisition board. A virtual instrument that allows real-time monitoring and Fourier analysis of signals from the vibration sensor was implemented in LabVIEW.

Keywords: Vibration measurement, FFT, AC motors, DC motors, Sensors

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A.c. Power Measurement Using Power Analyzer Associated with External Transducers. Accuracy and Uncertainty Evaluation
Marinel Popescu, Catalin Dobrea, Stefan Seitan

The development of the digital signal processors and their implementation in measuring technique has led to the manufacturing of power analyzers used as multifunction meters in industry, automation, tests and laboratory activities, monitoring and control of processes, etc. The parameters of a three-phase system can be known if the phase currents, the phase voltages and the phase difference between them can be known.A power analyzer has six inputs for currents and voltages measuring signals. The paper presents a method of determination of errors and uncertainties of electrical quantities measurement using a power analyzer associated with external transducers. The best estimation of measured quantity and uncertainty of measurement are used to report the result of measurement process.

Keywords: measuring signal, transducer, power analyzer, accuracy, uncertainty

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Diagnosis System for Elements Power Rectifiers
Virginia Ivanov, Maria Brojboiu, Sergiu Ivanov

The diagnosis of the electric systems is an actual item for the specialists in domain. The direction is interesting due to the multitude of the measuring points and large number of possible faults to be analyzed. The algorithms used for determining the normal/fault operation use new concepts and automatic systems as the expert systems. The proposed diagnosis system based on the analytic model investigates the output waveforms of a rectifier for two types of possible faults of the switches: interrupted and short circuit. For identifying the elements in fault, the waveforms corresponding to different faults are stored in an information database and compared with the ones corresponding to normal operation.

Keywords: Fault diagnosis, Rectifiers, Expert systems

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Reliability Evaluation of Electrical Networks
Victor Popescu

The problems of the evaluation of reliability in electrical networks of the different class of voltage a have probabilistic nature, they discretely change and depend on the number of factors both definite and indefinite and have importance by selection of electric equipment, graph of development of electrical networks and voltage levels. The definition of the major factors, which have determining significance on their value and speed of their change allow to elaborate methods of their optimization and to elaborate effective methods of their growth limitation in electrical networks with the different class of voltage. The present work is devoted to problems of calculation and assessment of indicators of reliability of distribution systems and supply of electricity to consumers, both agricultural and industrial.

Keywords: reliability indicators, the reliability of electrical networks

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Power System Restoration with Black-Start Pump Storage Power Plants
Walter Sattinger

One of the main duties of a transmission system operator (TSO) is to be prepared for the power system worst case, which means to restore the power system operation after a total blackout. To this aim two main principles are currently available. The first one is based on power system restoration with external voltage support and the second more challenging one is based on own voltage support from black-start generation units. The current paper describes experiences of power system restoration based on detailed dynamic system modelling and tested in the real system by interconnecting for the first time two hydro-power generation centers over the Alps and also by using as load the currently worldwide largest voltage source full converter-driven-pump of 100 MVA.

Keywords: Power system simulation and control, power system restoration tests

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Technical and economic analysis of Soft Starter Providing in LV Electrical Installation
Virgil Maier, Sorin G. Pavel, Iulian Birou, Horia G. Beleiu

The main aim of this paper is to identify the consequences magnitude of providing electronic starters, also called Soft Starters, in AC electrical motors with largest powers and the economical appreciation of this measure. Through this, it aims not only to identify the technical and economic arguments for applying more decided the provision of electronic starters, but also the limits of its application, given the great diversity of receivers rated power. Thus, it is appreciated that there is no question of applying Soft Starters for the whole power range of asynchronous motors.In context of the proposed analysis, a summary of electronic starters issues is made which may be a guide of their choice and application, facilitating the specialists access in the technical manuals of the companies producing Soft Starters.

Keywords: Soft Starter, LV distribution network

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Determination of the Level of Influence of Various Factors on the Reliability of Power System
Victor Popescu

Consumers supply with qualitative electric power is one of the priority requirements imposed to power systems. Currently, in electricity networks take place a number of planned and unplanned disconnections, which interrupt the power and affect consumers, causing economic damage. To ensure the quality of power supply it is essential to know the factors that influence the reliability of power systems, which have a visible impact on the variation of reliability of equipment installed in power systems. This paper is devoted to problems of calculation and analysis of power systems reliability and estimation of the impact of various factors that influence the supply of consumers.

Keywords: electrical equipments, electrical distribution systems, indicators of reliability, causal factors of refusals

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High Performance Shunt Active Power Filter: Design Consideration and Experimental Evaluation
Alexandru Bitoleanu, Mihaela Popescu, Vlad Suru

The paper presents an active power filter with high performance, achieved by the authors. To obtain these performances some contributions were brought, both in the power part and in the control part, those are highlighted. First, some design considerations of interface filter are done. Next, the experimental setup is presented and a lot of experimental determinations for different conditions of voltage and load are shown. These and some indices calculated show that, indeed, the achieved filtering platform has very good performances.

Keywords: power filters, reactive power control, harmonic distortion

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Improving Compensation Performance in Three- Phase Active Power Line Conditioners by DC-Voltage Control
Mihaela Popescu, Mircea Dobriceanu, Gheorghe Oprea

This paper analyses the influence of the prescribed DC-link voltage on the filtering efficiency, in terms of current harmonic distortion after compensation, in a three-phase three-wire shunt active power line conditioner. The AC voltage controller as nonlinear load and two configurations of the coupling filter are taken into consideration. It is pointed out that, for each rms current to be compensated, there is an optimal set value of the DC-link voltage which minimizes the supply current distortion after compensation. Experimental tests validate the simulation results.

Keywords: Power conditioning, Harmonic distortion, Voltage control

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Evaluation of Current Control Methods in Three- Phase Shunt Active Power Filters System
Constantin Vlad Suru, Mihaita Linca, Cristina Alexandra Patrascu

This paper aims the implementation of the control techniques for shunt power active filters and the achievement of a comparative study regarding the performance achieved by these techniques both in simulation and on an experimental active filter. The experimental active filter is using the dSpace DS1103 DSP board for the control section so different methods for the compensating current computation as well as for the DC-Link voltage and output current control can be investigated.

Keywords: DSP, harmonic distortion, current decomposition, active compensator

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Considerations on Numerical Protections for Induction Motors Connected in MV Industrial Power Systems
Gheorghe Hazi, Aneta Hazi

The paper presents some considerations on the calculation and adjustment of numerical protections used for induction motors connected in MV (6-10 kV) power systems. It examines the setting for the next protections: overcurrent, earth fault and thermal overload. An example for a 6 kV motor, 200 kW is presented.

Keywords: induction motors, motor protection, overcurrent protection, software protection

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Calculation of Industrial Power Systems Containing Induction Motors
Gheorghe Hazi, Aneta Hazi

The current paper proposes two methods and algorithms for determining the operating regimes of industrial electrical networks which include induction motors. The two methods presented are based on specific principles for calculating electrical networks: Newton-Raphson and Backward-Forward for iteratively determining currents and voltages. The particularity of this paper is how the driven load influences the determination of the motors operating regimes. For the industrial machines driven by motors we take into account the characteristic of the resistant torque depending on speed. In this way, at the electrical busbars to which motors are connected, the active and the reactive power absorbed are calculated as a function of voltage as opposed to a regular consumer busbar. The algorithms for the two methods are presented. Finally, a numerical study for a test network is realized and the convergence is analyzed.

Keywords: load flow analysis, induction motors, industrial power systems

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Gas Boiler Powered by the Fuel Cell System
Nicolae Badea, Madalin Costin

The paper presents a new solution for supply of boilers with electrical energy in the order to achieve autonomy from electrical grid. The paper presents the experimental system implemented in the university lab, the components and implementation in Matlab-Simulink for simulation. As a result of numeric simulation performed, the experimental bench has been achieved. The problem of power quality, especially the THD factor, affects the sensitivity of equipment at perturbations. In achieving of these systems, the authors propose that the electrical part of the supply system for building appliances must satisfy the EN 50160 standard, having the main voltage parameters and their permissile deviation ranges at the customer’s point of common coupling in public low voltage (LV), under normal operating conditions.

Keywords: PEM fuel cell, renewable source, power quality, hydrogen

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Improving Filter Performances for Conducted Electromagnetic Interferences Suppression
Adina Racasan, Calin Munteanu, Vasile Topa, Claudia Pacurar, Claudia Hebedean

Improving the performances of a filter for conductive electromagnetic interferences suppression involves two major directions of action: the first direction refers to the increase of attenuation at high frequency, while the second direction refers to the suppression of the parasitic effects in the constitutive devices. Thus, in this light, the paper presents the authors’ contribution to the two major directions of actions mentioned above; in the first part, techniques for HF loss increase are presented, while in the second part techniques for minimizing the structural parasitic capacitance are shown. In the third part of the paper these techniques are applied simultaneously to an EMI filter made in planar electromagnetic technology in order to study its performance.

Keywords: electromagnetic interferences, structural parasitic capacitance, HF losses, planar electromagnetic technology, EMI filters

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Retention of Powders from Flue Gases Resulted from the Combustion of Lignite in High Energy Boilers in Thermal Power Stations
Ion Teodor Ciochiu, Viorel Osiac, Bebe Huza, Gherghe Marius Leonard Ciurezu, Anemona Madalina Mousavi

Energy is essential for the economic and social welfare, for the smooth operation of most industrial and commercial activities. However, energy production and consumption exerts considerable pressures on the environment, which include contributions to climate changes, damage to natural ecosystems, damage to the environment built and generation of adverse effects on human health. The solutions to be implemented to make mechanical and electrical cyclones with high level of retention of powders from combustion gases are presented, taking into account the optimisation of gas flow through the active area of the electrostatic precipitator and the removal of dust re-drives from the collectors.

Keywords: powders, electrostatic precipitators, voltage

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Powder Collection from Flue Gases Resulting from the Burning of Lignite in Boilers from High Power Energy Power Plants
Ion Teodor Ciochiu, Viorel Osiac, Anemona Madalina Mousavi, Bebe Huza, Gherghe Marius Leonard Ciurezu

In the current economic context, marked by the increasingly broader recognition of interdependences between environment and development, we witness the increase of society’s demands on the environmental protection, demands materialised in increasingly more severe international rules. This paper sets out the most significant achievements, but it especially emphasises the solutions taken into account in the applications in the near future, so that the dust emissions on the stack would fall within the national legislation on environmental protection, which is sometimes hard to achieve, taking into account it is acted on some existing plants within a limited space.

Keywords: coal, frequency, voltage

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Optimizing Street Lighting Systems Design
Elisabeta Spunei, Ion Piroi, Florina Piroi

This work presents solutions to improve the quality parameters for outdoor illumination. The work starts from a case study which measured the outdoor lighting quality indicators on a street of the town Resita. We measured levels of lighting and brightness, and we computed various lighting indicators. The obtained values were then compared to the values recommended by actual technical norms observing that they do not fit into the normed limits. Using the Dialux software we calculated the optimal mounting variant of the lighting installation for the street under lighting analysis. In the optimizing software we kept the pole’s height and place in space constant to the values in the real situation. This work presents new variants of lighting installations that can ensure the best lighting indicators possible.

Keywords: lighting level, optimization methods, brightness

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Notes on LED Installations in Street Illumination
Elisabeta Spunei, Ion Piroi, Florina Piroi

The paper presents a study made on choosing LED street lighting installations, such that the quality requirements for exterior artificial lighting are fulfilled. We analyze two types of LED street lighting installations from a technical point of view, together with lighting level and brightness values obtained during the measurements. Following on the field measurements, the lighting quality parameters are calculated, and, for the lighting installation with the best performance, optimal mounting suggestions are made. The optimal quality parameters are calculated by simulations using the Dialux software. The same software and the same light sources we also compute an optimal street lighting by determining the size of the installation that provides the best lighting parameter values.

Keywords: lighting level, lighting installation, brightness, optimization

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Educational Approach to Information Transmission Channels of Data from Two Different Viewpoints: Combinatorial and Probabilistic
Silviu Draghici, Cornelia Victoria Anghel Drugarin, Andrea Amalia Minda, Mihaela Raduca, Eugen Raduca

For future engineers is important to know how to make the transfer of information, data and tasks between different systems and thus we can say that the problem of communication is as important as the determination of the amount of information. Elements of information theory and communications are useful to all students of the electrical engineering specializations who must be able to collect, store, process and interpret information of any kind. In order to determine the amount of information we can use a mathematical tool based on elements of probability theory and algebra.

Keywords: amount of information, data transmission channel, bit coding, signal

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Overview of the Orientation of Solar Generator Surfaces for Photovoltaic (PV) Systems
Cristian Paul Chioncel, Ladislau Augustinov, Valentin Nedelea, Petru Chioncel, Eugen Raduca

One of the most readily, espacialy for households as well as for higher installed power, renewable energy techniques to generate electrical power, are the solar photovoltaic (PV) systems. In the designing process of solar photovoltaic systems, a certain number of factors have to be considered in order to be able to capture maximum of solar radiant energy, for a given location, as ambient conditions, PV cells and the entire necessary equipment. Considering these factors, it allows to gain the maximum power with the existing equipment for the given radiation.

Keywords: PV system, orientation, solar generator surface

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Calculation of Control Circuits in Time Domain using Scilab/ Xcos Environment
Petru Chioncel, Silviu Draghici, Cristian Paul Chioncel

The paper presents the computing of control circuits in time domain, starting from the mathematical model of the control path described by differential equation’s with constant coefficients, whose solution can be obtained through Laplace transform and transfer functions. In the field of electric drives, the control circuits can be reduced to elements of PT1 and PT2 type, for which, the responses obtained from step and impulse function in the test process, are analyzed. The presented calculation, done in Scilab, highlights the test responses of the process and, the speed control circuit implemented as block diagrams in Xcos, reveals the improve of the process parameter through the control loop.

Keywords: mathematical model, transfer function, impulse and step response, Scilab / Xcos environment

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Calculation of Control Circuits in Frequency Domain using Scilab Environment
Petru Chioncel, Elisabeta Spunei, Cristian Paul Chioncel

The paper presents the computing of control circuits in the frequency domain, starting from the mathematical model of the frequency response H(jw) obtained from the transfer function H(s) where the operational variable keeps just the image part. For PT1 and PT2 elements, using Scilab, the geometrical place is illustrated and the frequency diagrams are determinate for different duping constants (PT2). The logarithmic frequency diagrams (Bode), determine the amplitude and phase reserve for a control circuits with three PT1 elements.

Keywords: mathematical model, transfer function, impulse and step response, Scilab / Xcos environment

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The Role of Mentoring in Entrepreneurship Training PREMIO Case Study
Gillich Nicoleta, Cristian Paul Chioncel

In company foundation and development, not just in entrepreneurial training, mentoring has an important place. The relation of mentoring is a win-win one, with advantages for both parties: mentee and mentor. Mentoring transmit and/or complete competences, skills and abilities that are not acquired through the classical education system. The paper presents practical tips to construct and enforce a productive mentoring system, starting with the mentor(s) selection to the outputs and process evaluation.

Keywords: education, mentoring, entrepreneurship

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