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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

Advances in Electrical and Computer Engineering Journal (AECE Journal)

AECE - Advances in Electrical and Computer Engineering Journal to czasopismo wydawane w Rumunii

M., DJUKIC, M., POPOVIC, N., CETIC, I., POVAZAN, In the recent years, research of special compiler techniques and algorithms for embedded processors broaden the knowledge of how to achieve better compiler performance in irregular processor architectures. However, industrial strength compilers, besides ability to generate efficient code, must also be robust, understandable, maintainable, and extensible. This raises the need for compiler infrastructure that provides means for convenient implementation of embedded processor oriented compiler techniques. Cirrus Logic Coyote 32 DSP is an example that shows how traditional compiler infrastructure is not able to cope with the problem. That is why the new compiler infrastructure was developed for this processor, based on research. in the field of embedded system software tools and experience in development of industrial strength compilers. The new infrastructure is described in this paper. Compiler generated code quality is compared with code generated by the previous compiler for the same processor architecture.

http://dx.doi.org/10.4316/aece.2014.03016 2014/09/23 - 21:56

R., MUNTEANU, A., CIMPEANU, A., GRAUR, C., FILOTE, G., LIUBA, The paper analyzes the behavior of an induction machine having the stator winding fed with two voltages of different frequencies. Usually, this particular operation is exploited in practice for testing high power induction machine (Ytterberg method). The specific aspects of this typical dynamic electromechanical process can be quantified only by simulation.

http://dx.doi.org/10.4316/aece.2014.03017 2014/09/23 - 21:56

R., CAMPEANU, M., CERNAT, An experimental exploration of using an Electronically Controlled Capacitor (ECC) in the supply system of a two speed single phase induction motor drive is presented. The ECC solution and the method with solution with a fixed value capacitor are comparatively analyzed in terms of efficiency and maximum torque availability. The losses and the over-voltages due to the electronic commutation are also analyzed. The paper proves the feasibility of the ECC solution and underlines its advantages and drawbacks. The optimal value of the switching frequency of ECC has been experimentally determined.

http://dx.doi.org/10.4316/aece.2014.03018 2014/09/23 - 21:56

J., CHO, E., SEO, J., JEONG, Web browsing on mobile networks is slow in comparison to wired or Wi-Fi networks. Particularly, the connection establishment phase including DNS lookups and TCP handshakes takes a long time on mobile networks due to its long round-trip latency. In this paper, we propose a novel web browser architecture that aims to improve mobile web browsing performance. Our approach delegates the connection establishment and HTTP header field delivery tasks to a dedicated proxy server located at the joint point between the WAN and mobile network. Since the traffic for the connection establishment and HTTP header fields delivery passes only through the WAN between the proxy and web servers, our approach significantly reduces both the number and size of packets on the mobile network. Our evaluation showed that the proposed scheme reduces the number of mobile network packets by up to 42% and, consequently, the average page loading time is shortened by up to 52%.

http://dx.doi.org/10.4316/aece.2014.03001 2014/09/21 - 14:03

D. T., VUZA, R., FROSCH, H., KOEBERL, M., VLADESCU, Class D amplifiers find new applications in RFID systems, because of their high efficiency. Most textbooks describe the case of a load directly connected to the amplifier. However, in most RFID systems the usage of a transmission line is mandatory and this may introduce some novel effects, in the form of an infinite series of peaks in the system frequency response functions. If not appropriately taken care of, these effects may lead to electromagnetic compatibility problems. The purpose of the paper is to develop the theory of the peak control function, which is conceived as a tool that allows the designer to keep the magnitude of the peaks, and hence their influence on the system, into well defined limits.

http://dx.doi.org/10.4316/aece.2014.03002 2014/09/21 - 14:03

Y., ZHANG, Z., WANG, The new type of backup protection can utilize different kinds of information in a larger scale. The research of this paper is focused on the centralized decision and distributed implementation of wide area backup protection system in large-scale power grid. Topology analysis of power network is substantially network connectivity judgment. The operation conditions in case of a failure should be truthfully reflected in the actual structure of network topology, which requires the system failure must be detected promptly and accurately, and prepare for the subsequent adjustment of operation scheme. In the research of this paper, for different kinds of complex system failures, we have put forward a novel fault factor analysis scheme which can realize rapid, accurate and effective fault detection. Many simulations have verified that the fault factor analysis can successfully detect the failures in complex electric power system.

http://dx.doi.org/10.4316/aece.2014.03003 2014/09/21 - 14:03

J., ESCOBEDO, A., MEDINA, J.-C., HERNANDEZ, G., ALMONACID, P., VIDAL, The detection of irregularities such as a fraudulent branch line or a fault in short-length low voltage (LV) lines is of great interest for electricity supply companies as well as for other businesses. This paper describes and systematizes new techniques that afford in-depth knowledge of the occurrence of irregularities in these lines for the first time. Firstly, it has been characterized the response of a typical short-length tapped line by means of conventional time-domain reflectometry (TDR) technique as well as the additional new techniques proposed. These techniques are based on a conventional mathematical treatment of discrete-time signals. Moreover, they obviate the need for visual inspection at remote locations and only involve a moderate computational effort. Finally, it is exposed how fraudulent branch lines were detected in two real domestic supplies at the local electricity supply company by the proposed techniques. The first fraudulent line was detected in a long incoming main line buried in the ground by mean of the line-symmetry technique. The second one was detected in a short incoming main line located in building voids by the second echo and power spectral density methods. The accuracy of the results has been assessed in laboratory tests as well.

http://dx.doi.org/10.4316/aece.2014.03004 2014/09/21 - 14:03

J. P., KRSTIVOJEVIC, M. B., DJURIC, A new method of avoiding malfunctioning of the transformer restricted earth fault (REF) protection is presented. Application of the proposed method would eliminate unnecessary operation of REF protection in the cases of faults outside protected zone of a transformer or a magnetizing inrush accompanied by current transformer (CT) saturation. On the basis of laboratory measurements and simulations the paper presents a detailed performance assessment of the proposed method which is based on digital phase comparator. The obtained results show that the new method was stable and precise for all tested faults and that its application would allow making a clear and precise difference between an internal fault and: (i) external fault or (ii) magnetizing inrush. The proposed method would improve performance of REF protection and reduce probability of maloperation due to CT saturation. The new method is robust and characterized by high speed of operation and high reliability and security.

http://dx.doi.org/10.4316/aece.2014.03005 2014/09/21 - 14:03

Y., PARK, Building and measuring trust is one of crucial aspects in e-commerce, social networking and computer security. Trust networks are widely used to formalize trust relationships and to conduct formal reasoning of trust values. Diverse trust network analysis methods have been developed so far and one of the most widely used schemes is TNA-SL (Trust Network Analysis with Subjective Logic). Recent papers claimed that TNA-SL always finds the optimal solution by producing the least uncertainty. In this paper, we present some counter-examples, which imply that TNA-SL is not an optimal algorithm. Furthermore, we present a probabilistic algorithm in edge splitting to minimize uncertainty.

http://dx.doi.org/10.4316/aece.2014.03006 2014/09/21 - 14:03

O. T., ALTINOZ, A. E., YILMAZ, G.-W., WEBER, Nature-inspired optimization algorithms can obtain the optima by updating the position of each member in the population. At the beginning of the algorithm, the particles of the population are spread into the search space. The initial distribution of particles corresponds to the beginning points of the search process. Hence, the aim is to alter the position for each particle beginning with this initial position until the optimum solution will be found with respect to the pre-determined conditions like maximum iteration, and specific error value for the fitness function. Therefore, initial positions of the population have a direct effect on both accuracy of the optima and the computational cost. If any member in the population is close enough to the optima, this eases the achievement of the exact solution. On the contrary, individuals grouped far away from the optima might yield pointless efforts. In this study, low-discrepancy quasi-random number sequence is preferred for the localization of the population at the initialization phase. By this way, the population is distributed into the search space in a more uniform manner at the initialization phase. The technique is applied to the Gravitational Search Algorithm and compared via the performance on benchmark function solutions.

http://dx.doi.org/10.4316/aece.2014.03007 2014/09/21 - 14:03

T., HUANG, S. L., VORONCA, A. A., PURCAREA, A., ESTEBSARI, E., BOMPARD, Contemporary power systems are facing increasing intricate conditions that have never been considered when initially designing the infrastructure, such as malicious threats, accommodating smart grids, etc. As a consequence, blackouts albeit seldom but stubbornly keep appearing from time to time the world around, and demonstrate their devastating capability to create vast damage on both power systems and the society at large. Patterns of the blackout starting from the first triggering events to the system final status have emerged. A framework of a coding system was proposed in this paper in order to capture the common feature in the system evolution during the development of cascades. Cascades in a blackout can be tracked by a chain of events with the help of the codes. It is facile to adopt the framework to build up a knowledge base of blackouts. By applying the proposed framework to 31 selected historic blackouts, most frequent events, effects and origins are identified; the findings can provide useful information for grid designers and security experts for ranking the most imminent issues in their study.

http://dx.doi.org/10.4316/aece.2014.03008 2014/09/21 - 14:03

I.-V., BORNOIU, O., GRIGORE, This paper presents a method for identifying human stress levels by using a Kohonen neural network. The study focuses on differentiating between a relaxed and a stressed state and it presents a series of parameters (skin conductance response signal power, skin conductance response signal frequency, skin conductance level gradient, response rise time and response amplitude) extracted only from the electrodermal activity signal. A very strict recording protocol was used to minimize the artifacts caused by the bad connection between electrodes and skin. A stress inducing method is presented that can be used to replicate results in laboratory conditions.

http://dx.doi.org/10.4316/aece.2014.03009 2014/09/21 - 14:03

I., AYDIN, M., KARAKOSE, E., AKIN, Comfort and safety of railway transport has become more important as train speeds continue to increase. In electrified railways, the electrical current of the train is produced by the sliding contact between the pantograph and catenary. The quality of the current depends on the reliability of contact between the pantograph and catenary. So, pantograph inspection is very important task in electrified railways and it is periodically made for preventing dangerous situations. This inspection is operated manually by taking the pantograph to the service for visual anomalies. However, this monitoring is impractical because of time consuming and slowness, as locomotive remains disabled. An innovative method based on image processing and pattern recognition is proposed in this paper for online monitoring of the catenary-pantograph interaction. The images are acquired from a digital line-scan camera. Data are simultaneously processed according to edge detection and Hough transform, and then the obtained features are provided to a D-Markov based state machine, and the pantograph related faults, such as overheating of the pantograph strip, bursts of arcing, and irregular positioning of the contact line are diagnosed. The proposed method is verified by real faulty and healthy pantograph videos.

http://dx.doi.org/10.4316/aece.2014.03010 2014/09/21 - 14:03

A., DURUSU, I., NAKIR, A., AJDER, R., AYAZ, H., AKCA, M., TANRIOVEN, Maximum power point trackers (MPPTs) play an essential role in extracting power from photovoltaic (PV) panels as they make the solar panels to operate at the maximum power point (MPP) whatever the changes of environmental conditions are. For this reason, they take an important place in the increase of PV system efficiency. MPPTs are driven by MPPT algorithms and a number of MPPT algorithms are proposed in the literature. The comparison of the MPPT algorithms in literature are made by a sun simulator based test system under laboratory conditions for short durations. However, in this study, the performances of four most commonly used MPPT algorithms are compared under real environmental conditions for longer periods. A dual identical experimental setup is designed to make a comparison between two the considered MPPT algorithms as synchronized. As a result of this study, the ranking among these algorithms are presented and the results show that Incremental Conductance (IC) algorithm gives the best performance.

http://dx.doi.org/10.4316/aece.2014.03011 2014/09/21 - 14:03

P., ROZGA, D., CIESLINSKI, M., STANEK, M., KACZMAREK, This article describes the measurement techniques used for the study of mechanisms of electrical discharge development in ester fluids under lightning impulse voltage. These techniques were applied in a laboratory experimental system which enabled the acquisition of a wide range of experimental data. An analysis of the data gives the possibility of assessing the processes responsible for electrical discharge propagation in different types of dielectric liquids. The photographic registration system provides photographs of developing discharges. This uses the shadowgraph method with an impulse laser as a flash lamp. The system of light emission registration enables collection of the time courses of light emitted by the developing discharge. Both systems operating together are synchronized using light guide communication. They are also unaffected by external disturbances such as network overvoltages and high electrical field stress. Preliminary results obtained on the basis of the described techniques, in the field of electrical discharge development in synthetic and natural esters, are presented in the article. These results confirm suitability of the methods used and give the possibility to formulate first conclusions.

http://dx.doi.org/10.4316/aece.2014.03012 2014/09/21 - 14:03

O., ROSHCHUPKIN, R., SMID, A., SACHENKO, V., KOCHAN, Results of studying the neural network method are presented to reduce the amount of calibration points for the multisensor (MS), in particular for the photodiode. This allows transmitting to the MS individual conversion function and provides the high accuracy of measurement. The structure of synthesized information-measuring system and its measuring channel has created for implementing of the proposed approach. A structural scheme is proposed as well for values transmitting the etalon measures to measuring systems. Its used to determine the errors of photodiodes, as those which are produced for customers. This assures the interchangeability of sensors when using the individual conversion function.

http://dx.doi.org/10.4316/aece.2014.03013 2014/09/21 - 14:03

M., LUCANU, O., URSARU, C., AGHION, N., LUCANU, The paper presents a single-phase direct AC-AC boost converter. The circuit of the converter is simple and it has good performances, irrespective of the load nature. The adequate functioning and high performance of the circuit (the efficiency and waveform of the absorbed input current) were tested both by simulation and experimentally.

http://dx.doi.org/10.4316/aece.2014.03014 2014/09/21 - 14:03

S., BORA, In this paper, findings and analysis detail the implementation of fault tolerance services into a goal-oriented multi-agent systems development platform. Fault tolerance services are used to provide replication-based fault tolerance policies (i.e. static and adaptive) to multi-agent systems. This approach provided flexibility and reusability to multi-agent systems because fault tolerance policies were implemented as reusable plan structures. Thus, whenever an agent was needed to be made fault-tolerant, plans for fault tolerance policies were simply activated by sending a request message.

http://dx.doi.org/10.4316/aece.2014.03015 2014/09/21 - 14:03

S., GORGUNOGLU, I. M., ORAK, A., CAVUSOGLU, M., GOK, In analysis of minutiae based fingerprint systems, fingerprints needs to be pre-processed. The pre-processing is carried out to enhance the quality of the fingerprint and to obtain more accurate minutiae points. Reducing the pre-processing time is important for identification and verification in real time systems and especially for databases holding large fingerprints information. Parallel processing and parallel CPU computing can be considered as distribution of processes over multi core processor. This is done by using parallel programming techniques. Reducing the execution time is the main objective in parallel processing. In this study, pre-processing of minutiae based fingerprint system is implemented by parallel processing on multi core computers using OpenMP and on graphics processor using CUDA to improve execution time. The execution times and speedup ratios are compared with the one that of single core processor. The results show that by using parallel processing, execution time is substantially improved. The improvement ratios obtained for different pre-processing algorithms allowed us to make suggestions on the more suitable approaches for parallelization.

http://dx.doi.org/10.4316/aece.2014.02001 2014/06/25 - 16:51

B., ZHANG, C., ZHAO, C., GUO, X., XIAO, L., ZHOU, Compared with high voltage direct current (HVDC), the primary and secondary systems of modular multilevel converter based HVDC (MMC-HVDC) are complicated. And the characteristics of the control system determine the properties of the MMC-HVDC system to a certain extent. This paper investigates the design of control architecture. First, the structure and parameters of the 21-level MMC-HVDC are designed. Second, the framework of the control system is studied in details and a complete control system is established. The communication mode and content are built between each layer, and the control system program is developed and debugged. Then The steady state test platform of the sub-module and the relevant control system are designed. Finally, the steady-state tests and the system test of the physical MMC-HVDC simulation system are conducted, which prove that the SMC can control the sub-module (SM) efficiently, and the control system could realize efficient start and stop of the physical system. Meanwhile, the capacitor voltage balance between the sub-modules and the basic fault protection and control of the DC voltage and power are verified to be effective.

http://dx.doi.org/10.4316/aece.2014.02002 2014/06/25 - 16:51

X., XU, C., HUANG, C., WU, Q., WANG, L., ZHAO, In this paper, the algorithm based on graph learning and graph embedding framework, Speaker-Penalty Graph Learning (SPGL), is proposed in the research of speech emotion recognition to solve the problems caused by different speakers. Graph embedding framework theory is used to construct the dimensionality reduction stage of speech emotion recognition. Special penalty and intrinsic graphs of the graph embedding framework is proposed to penalize the impacts from different speakers in the task of speech emotion recognition. The original speech emotion features are extracted by various categories, reflecting different characteristics of each speech sample. According to the experiments in speech emotion corpus using different classifiers, the proposed method with linear and kernelized mapping forms can both achieve relatively better performance than the state-of-the-art dimensionality reduction methods.

http://dx.doi.org/10.4316/aece.2014.02003 2014/06/25 - 16:51

A. W., REZA, T. T., RUI, A. S., KAUSAR, Radio frequency identification (RFID) is the widely used identification system that uses radio frequency for the detection of object position. A new RFID technique for the localization of tags in a 3D space is presented in this study. According to this technique, the optimized number of mobile readers is needed to afford full coverage within a given period of time. The mobile readers are programmed in such a way that they move in a zigzag pattern for detecting the tags. The received signal strength (RSS) model is used for determining the tag positions. From the obtained results, it can be observed that the proposed model can achieve an average error distance as low as 0.27 m for a given scenario and if the obstacles are placed in the test environment, the average error distance has only increased to 0.38 m. In order to evaluate the accuracy of the proposed technique, a comparison between the existing and proposed model is presented.

http://dx.doi.org/10.4316/aece.2014.02004 2014/06/25 - 16:51

P., KOVAR, S., JELEN, The cold start of the LEO satellite GPS receiver is complicated due to a large Doppler frequency shift, Doppler frequency rate of the navigation signals and a rapid change of the satellite visibility. The cold start time can be shortened by a proper strategy of a selection of the satellites to be searched for. The cold start simulator was developed and used for optimization of the sequence of the satellites search, for development and testing of an advanced satellite selection algorithm that utilizes information on the satellites already detected and for optimization of a frequency search range. The best performance was achieved by using an advanced selection strategy. The strategy is based on the selection of the satellites nearest to the detected satellite, using the average angle between the Earth center (apex) and the satellites. Furthermore, the simulation shows that it is not practical to investigate all frequencies within the range of the maximum possible Doppler frequency shift of the carrier wave of the navigation signal, but investigate approximately +/- 35 kHz range and, if not successful, switch to the next satellite. The simulations proved that a simple GPS receiver with the sequential search algorithms can operate in the LEO orbit.

http://dx.doi.org/10.4316/aece.2014.02005 2014/06/25 - 16:51

S., HAMAD, A., KHALIFA, A., ELHADAD, The flourishing field of Steganography is providing effective techniques to hide data into different types of digital media. In this paper, a novel technique is proposed to hide large amounts of image data into true colored images. The proposed method employs wavelet transforms to decompose images in a way similar to the Human Visual System (HVS) for more secure and effective data hiding. The designed model can blindly extract the embedded message without the need to refer to the original cover image. Experimental results showed that the proposed method outperformed all of the existing techniques not only imperceptibility but also in terms of capacity. In fact, the proposed technique showed an outstanding performance on hiding a secret image whose size equals 100% of the cover image while maintaining excellent visual quality of the resultant stego-images.

http://dx.doi.org/10.4316/aece.2014.02006 2014/06/25 - 16:51

A., BOUMASSATA, D., KERDOUN, In this paper, we propose a wind energy conversion system (WECS) at variable speed using a doubly fed induction generator (DFIG) controlled on the rotor side through a cycloconverter. The dynamic behavior of the WECS, including the models of the wind turbine, the DFIG, the cycloconverter, and the power control of this system, is investigated. The power control of this system is applied to achieve the independent control of the active and reactive powers exchanged between the wind generator and the grid. In addition, a maximum power point tracking (MPPT) control is included in the control system to capture the maximum power from the wind. Moreover, the cycloconverter with DFIG are used to test the possibility to operate in two quadrant modes (sub-synchronous and super-synchronous modes). The description of the proposed system is presented with the detailed dynamic modeling equations. The simulation results are presented, to demonstrate the performance and the efficiency of this system.

http://dx.doi.org/10.4316/aece.2014.02007 2014/06/25 - 16:51

G., SCUTARU, H., GAVRILA, I., PETER, More than 60% of industrial electricity consumption is made by electrical drives with induction motors. In 2008, by IEC 60034-30, the International Electrotechnical Commission defined the efficiency classes of induction motors namely: IE1, IE2 and IE3. The IE4 was defined in 2010 by IEC 60034-3. From 1 January 2015, the induction motors with a rated output of 7.5-375 kW shall not be less efficient than the IE3 class (Premium Efficiency Class). In order to obtain IE3 motors, manufacturers need to have a design method which takes into account the influence of the technological process on the properties of materials used; specially magnetic properties. This paper presents a new method to estimate the iron losses taking into account the effect of the mechanical cutting on the specific iron losses of the sheets. The method presented enables more accurate determination of the iron losses taking into account the effect of the punching process on the magnetic properties of sheets without a significant increase of the computational time. The case of M400 iron sheets was analyzed.

http://dx.doi.org/10.4316/aece.2014.02008 2014/06/25 - 16:51

S., KANG, J.-H., KIM, J., SEO, Overcoming speech recognition errors in the field of humancomputer interaction is important in ensuring a consistent user experience. This paper proposes a semantic-oriented post-processing approach for the correction of errors in speech recognition. The novelty of the model proposed here is that it re-ranks the n-best hypothesis of speech recognition based on the user's intention, which is analyzed from previous discourse information, while conventional automatic speech recognition systems focus only on acoustic and language model scores for the current sentence. The proposed model successfully reduces the word error rate and semantic error rate by 3.65% and 8.61%, respectively.

http://dx.doi.org/10.4316/aece.2014.02009 2014/06/25 - 16:51

O., BREKHOV, M., RATNIKOV, This article approaches the solution of FPGA testing and research of characteristics at early development stages. The approach offers error-detection code based on universal test firmware. The performed test firmware based on CRC and Hamming codes detect single and multiple faults, and locate fault place (for Hamming code based test firmware).

http://dx.doi.org/10.4316/aece.2014.02010 2014/06/25 - 16:51

V., SKLYAROV, I., SKLIAROVA, This paper is dedicated to the design, implementation and evaluation of fast FPGA-based circuits that compute Hamming weights for binary vectors and compare the results with fixed thresholds and variable bounds. It is shown that digital signal processing (DSP) slices that are widely available in contemporary FPGAs may be used efficiently and they frequently provide the fastest and least resource consuming solutions. A thorough analysis and comparison of these with the best known alternatives both in hardware and in software is presented. The results are supported by numerous experiments in recent prototyping boards. A fully synthesizable hardware description language (VHDL) specification for one of the proposed core components is given that is ready to be synthesized, implemented, tested and compared in any FPGA that contains embedded DSP48E1 slices (or alternatively DSP48A1 slices from previous generations). Finally, the results of comparisons are provided that include discussions of designs in an ARM processor combined with reconfigurable logic for very long vectors.

http://dx.doi.org/10.4316/aece.2014.02011 2014/06/25 - 16:51

P., PALACKY, P., BRANDSTETTER, P., CHLEBIS, V., SLADECEK, P., SIMONIK, D., SLIVKA, The article deals with the research of algorithms for controlling electronic differential and differential lock of an electrically driven vehicle. The simulation part addresses the development of algorithms suitable for the implementation into a real system of a road vehicle. The algorithms are then implemented into a vehicle, a propulsion unit of which is consists of two separate electric drives with induction motors fed by voltage inverters with own control units using advanced signal processors. Communication among control units is provided by means of SPI interface. A method of vector control is used for the control of induction motors. The developed algorithms are experimentally verified for correct function in a laboratory using a roll test stand and while driving an electrically driven vehicle on the road.

http://dx.doi.org/10.4316/aece.2014.02012 2014/06/25 - 16:51

L., LIVADARU, A., MUNTEANU, A., SIMION, B., VIRLAN, S., BENELGHALI, In this paper an investigation on the fault tolerance capability of the five-phase permanent magnet synchronous generator is presented. The electric machine, which has lap stator winding and surface permanent magnets, has been designed for islanded-use purposes. The study takes into consideration the open-circuit type faults. It was analyzed the operation under healthy, one-phase open-circuited and two-phase open-circuited (adjacent and non-adjacent) conditions respectively. The results derive from FEM-based simulations and experimental tests.

http://dx.doi.org/10.4316/aece.2014.02013 2014/06/25 - 16:51

D.-H., KIM, In this paper, two new addressing modes are introduced to the 16-bit Thumb instruction set architecture to improve performance of the ARM/Thumb processors. Contrary to previous approaches, the proposed approach focuses on the addressing mode of the instruction set architecture. It adopts scaled register offset addressing mode and post-indexed addressing mode from the 32-bit ARM architecture, which is the superset of the 16-bit Thumb architecture. To provide the encoding space for the new addressing modes, the register fields in the LDM and STM instructions are reduced, which are not frequently executed. Experiments show the proposed extension achieves an average of 7.0% performance improvement for the seven benchmark programs when compared to the 16-bit Thumb instruction set architecture.

http://dx.doi.org/10.4316/aece.2014.02014 2014/06/25 - 16:51

R. S., ARASHLOO, J. L., ROMERAL MARTINEZ, M., SALEHIFAR, V., SALA, Efficiency improvement under faulty conditions is one of the main objectives of fault tolerant PM drives. This goal can be achieved by increasing the output power while reducing the losses. Stator copper loss not only directly affects the total efficiency, but also plays an important role in thermal stress generations of iron core. In this paper, the effect of having control on neutral point current is studied on the efficiency of five-phase permanent magnet machines. Open circuit fault is considered for both one and two phases, and the distribution of copper loss along the windings are evaluated in each case. It is shown that only by having access to neutral point, it is possible to generate less stator thermal stress and more mechanical power in five-phase permanent magnet generators. Wind power generation and their applications are kept in mind, and the results are verified via simulations and experimental tests on an outer-rotor type of five-phase PM machine.

http://dx.doi.org/10.4316/aece.2014.02015 2014/06/25 - 16:51

J., MILOS, S., HANUS, A Physical Hybrid ARQ Indicator Channel (PHICH) is a very important element of the Long Term Evolution (LTE), Release 8 communication system. Via the PHICH, a Hybrid ARQ Indicator (HI) acknowledge message is transmitted. The HI informs the result if the previous data transfer in uplink direction. Imperfect protection of PHICH transfer can cause superfluous repetitions of incorrect confirmed data and uplink overhead grows. In the paper, the PHICH signal processing and performance results of a single HI message in AWGN and fading channel models are presented depending on the representative antenna modes. The performance results for a number of HI messages greater than one within a single PHICH group, have not been found.

http://dx.doi.org/10.4316/aece.2014.02016 2014/06/25 - 16:51

A., PATRASCU, V.-V., PATRICIU, Cloud Computing is a rather new technology which has the goal of efficiently usage of datacenter resources and offers them to the users on a pay per use model. In this equation we need to know exactly where and how a piece of information is stored or processed. In today's cloud deployments this task is becoming more and more a necessity and a must because we need a way to monitor user activity, and furthermore, in case of legal actions, we must be able to present digital evidence in a way in which it is accepted. In this paper we are going to present a modular and distributed architecture that can be used to implement a cloud digital forensics framework on top of new or existing datacenters.

http://dx.doi.org/10.4316/aece.2014.02017 2014/06/25 - 16:51

V., GRIGORAS, C., GRIGORAS, We introduce a novel third order analogue nonlinear system, using three multipliers as nonlinear functions. The proposed system exhibits rich nonlinear dynamics, with periodic and chaotic behaviors, depending on the system parameters. The strange attractor of the system, under chaotic parameter choice, is characterized by a limited domain occupied in the state space. The analysis of the nonlinear dynamics of the system is presented and in depth simulation results confirm the desired properties. Suggested applications of the proposed system include analogue noise generators and spread spectrum clock generators.

http://dx.doi.org/10.4316/aece.2014.02018 2014/06/25 - 16:51

F., AGUIRRE-RAMOS, A., MORALES-REYES, R., CUMPLIDO, C., FEREGRINO-URIBE, This article presents a composed architecture for the CORDIC algorithm. CORDIC is a widely used technique to calculate basic trigonometric functions using only additions and shifts. This composed architecture combines an initial coarse stage to approximate sine and cosine functions, and a second stage to finely tune those values while CORDIC operates on rotation mode. Both stages contribute to shorten the algorithmic steps required to fully execute the CORDIC algorithm. For comparison purposes, the Xilinx CORDIC logiCORE IP and previously reported research are used. The proposed architecture aims at reducing hardware resources usage as its key objective.

http://dx.doi.org/10.4316/aece.2014.02019 2014/06/25 - 16:51

A., KULANTHAISAMY, R., VAIRAMANI, N. K., KARUNAMURTHI, C., KOODALSAMY, This paper presents a Multi- objective Optimal Placement of Phasor Measurement Units (MOPP) method in large electric transmission systems. It is proposed for minimizing the number of Phasor Measurement Units (PMUs) for complete system observability and maximizing the measurement redundancy of the system, simultaneously. The measurement redundancy means that number of times a bus is able to monitor more than once by PMUs set. A higher level of measurement redundancy can maximize the total system observability and it is desirable for a reliable power system state estimation. Therefore, simultaneous optimization of the two conflicting objectives are performed using a binary coded Artificial Bee Colony (ABC) algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is considered to the main model. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems. The valuable approach of ABC algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing the performance with earlier works.

http://dx.doi.org/10.4316/aece.2014.02020 2014/06/25 - 16:51

A. L., BALAN, N. D., ALEXANDRU, A novel family of inter-symbol interference (ISI) free pulses generated by improved Nyquist filters with a frequency characteristic composed of six parabolic pieces is proposed. We studied the performance of the new pulses in terms of the ISI error probability when the impulse response is sampled with a timing offset. To illustrate the achieved improvement, the new pulses are compared with other performing pulses that were reported in the literature. Simulation results show that comparable or enhanced ISI performance can be obtained at reasonable complexity.

http://dx.doi.org/10.4316/aece.2014.02021 2014/06/25 - 16:51

V., MURESAN, M., ABRUDEAN, M.-L., UNGURESAN, T., COLOSI, In this paper, a solution for the automatic control of a residual water blunting system is proposed. The blunting technological process, being a distributed parameter one, is modeled using partial differential equations. This approach implies very big technological advantages due to the fact that the user has access to the pH value in each point of the tanks of the blunting system. Another element of originality is the inclusion of a distributed parameter process in a control structure, having the possibility to maintain the pH value constant in each point in the volume of the liquid from the system. A method based on the matrix of partial derivatives of the state vector (Mpdx) associated with Taylor series is used for the modeling-simulation of both the blunting process and the control system. The results assured by a simple control structure are not sufficient due to the restrictive imposed performances, so a cascade structure is treated in the paper.

http://dx.doi.org/10.4316/aece.2014.02022 2014/06/25 - 16:51