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23,598 Article Results

Study of Small Signal of 4H-SiC Static Induction Transistor

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2297
Gang Chen , Yang Lu , Li Li , Song Bai , Yun Li , Haiyan Lu
Silicon carbide (SiC) SITs were fabricated using home-grown epi structures. The gate is a recessed gate - bottom contact (RG - B). We designed that the mesa space 2.5 μm and the gate channel is 1.5 μm. One cell has 400 source fingers and each source finger width is 50 μm. 0.5 mm gate periphery SiC SIT yielded a maximum drain current density of 160 mA/mm at a drain voltage of 80 V and a gate voltage of 2.5 V. The device blocking voltage with a gate bias of -16 V was 400 V. Packaged 0.5-mm devices were evaluated using amplifier circuits designed for class AB operations. Small signal of SIT was studied. the maximum stable gain (MSG) were 11.2 dB at 500MHz and 7.85 dB at L band 1 GHz with Vds = 80V and Vg = 2V. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2559
Volume: 11
Issue: 5
Page: 2838-2844
Publish at: 2013-05-01

Reliability and Security Analysis on Two-Cell Dynamic Redundant System

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2267
Hongsheng Su
Based on analysis on reliability and security on three types of two-cell dynamic redundant systems which has been widely applied in modern railway signal system, whose isomorphic Markov model was established in this paper. During modeling several important factors, including common-cause failure, coverage of diagnostic systems, online maintainability, and periodic inspection maintenance, and as well as many failure modes, were considered, which made the established model more credible. Through analysis and calculation on reliability and security indexes of the three types of two-module dynamic redundant structures, the paper acquires a significant conclusion, i.e., the safety and reliability of the kind of structure possesses an upper limit, and can not be inordinately improved through the hardware and software comparison methods under the failure and repairing rate fixed. Finally, the paper performs the simulation investigations, and compares the calculation results of the three redundant systems, and analysis each advantages and disadvantages, and gives out each application scope, which provides a theoretical technical support for the railway signal equipments selection. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2492
Volume: 11
Issue: 5
Page: 2594-2604
Publish at: 2013-05-01

Research on Early Fault Diagnostic Method of Wind Turbines

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2233
Zhai Yongjie , Wang Dongfeng , Zhang Junying , Han Yuejiao
Challenging environmental factors combined with high and turbulent winds make serious demands on wind turbines and result in significant component fault rates. In this paper, an early fault diagnostic research is conducted upon wind turbines. Firstly, the SCADA (Supervisory Control and Data Acquisition) system is used to analyze the units’ long-hour operating data, preparing for the further modeling work. Then the MSET (Multivariate State Estimation Technique) is adopted to estimate the temperature of the gear box and to obtain a result of high accuracy; with the Moving Window Calculation (MWC), the residual value between the estimated value and the real value is studied to get the dynamic trend of its average value; according to this trend in training, we define the threshold region of the residual mean value. Considering a man-made deviation in the observation vectors, faults of the gear box are simulated and studied. When the residual mean value curve exceeds the setting thresholds, an alert will be given to remind the operators of hidden problems in the unit. Research shows that this early diagnostic method is quite effective in detecting the abnormal performance of wind turbines in a real-time manner. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2457
Volume: 11
Issue: 5
Page: 2330-2341
Publish at: 2013-05-01

Electric and Thermal Properties of a Single Phase Cable Buried in Soil: An Analysis with the Finite Element Method (FEM)

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2225
Kanikella Sushman Kumar
Current carrying capacity of power cable should be determined by the maximum operating temperature which the insulation can withstand. The temperature rise in cable is mainly due to Joule’s loss in conductor and induced eddy loss in sheath. In this paper, based on the coupled electromagnetic-thermal theory, the power losses calculated in electric field analysis are used as the input data of thermal analysis to predict the temperature rise in different layers of cable. The Distribution radial temperature characteristic analyzed with the method of finite element. Result obtained indicates that the radial temperature distribution of the Single Phase cable do not flattened distribution. It is showed that the highest distribution radial temperature in the conductor shares, while the cable insulation near grounded showed lower distribution temperature as according to given boundary condition. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2086
Volume: 11
Issue: 5
Page: 2271-2279
Publish at: 2013-05-01

Research on Mining Development in Yunnan under Ecological Environment Compensation

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2299
Jianqun Xiang , Yunzhong Liu , Dan Dong , Meng Zhang
Yunnan province is rich of mineral resources, and the mining industry is the pillar industry in Yunnan. But with the development of mining economy, the problems of the ecological environmental damage have come out. Under the mechanism of ecological environment compensation, the mining economic development in Yunnan needs to deal well with the problems of environmental protection. According to the natural ecological conditions of mining area in Yunnan Province, and combining with the phenomena on economic, social, and environmental development, the paper will analyze the impact on ecological environment in Yunnan in the process of mineral exploitation and utilization. It will also provide the mining development and environmental protection in Yunnan with reasonable proposal and give decision-making references about development plans for government. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2561
Volume: 11
Issue: 5
Page: 2853-2859
Publish at: 2013-05-01

Magnetoelectric Speed Sensor to Detect Ultra-Low Frequency Vibrations

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2256
Dong Ke , Qian Yuxia , Yuan Zhangyi
Ultra-low frequency vibrations are ordinary physical phenomena, and absolute vibrant sensors are usually used to detect them. The author presents a method that using magnetoelectric speed sensor to detect ultra-low frequency vibrations. With cascade correcting circuit, the lowest frequency that can be measured will be less than 0.5Hz while the best damping is maintained. The author has systematically analyzed the correcting circuit, transfer function, theory of operation, and the difference between output characteristics before and after correcting to the ultra-low frequency sensor. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2480
Volume: 11
Issue: 5
Page: 2502-2507
Publish at: 2013-05-01

Competitiveness Comparative Research on Jiaozuo Service Industry Based on Synchronic and Diachronic Data

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2288
XU Jun
Service industry plays a more and more important role in economic development, it had become an important symbol for the enhancement of one region competitiveness. The paper constructed the Jiaozuo service competitive evaluation model, which used 2004-2011 years sequence data of Jiaozuo and synchronic data of Zhengzhou, Kaifeng, Luoyang, Xinxiang, Jiaozuo five cities, based on the DEA method, designed input index including employees and fixed assets, designed output index including service industry output value and growth rate, then it solved the answer with LINGO8.0 linear programming software. Model could not only evaluate sequence change on development of service industry competitiveness for eight years in Jiaozuo, but also did a horizontal section comparison with Zhengzhou, Kaifeng, Luoyang, Xinxiang four Cities. Model operation results showed that Jiaozuo service industry appeared to be on the mend but unstable situation on the overall effectiveness according to the longitudinal input and output, the horizontal section comparing showed that it had slightly shortage than Zhengzhou, Kaifeng city, it was in a horizontal line with Xinxiang, Luoyang, but the total amount was insufficient, it was totally in accord with the actual situation in Jiaozuo service industry development. Finally, it proposed the countermeasure and suggestion from Jiaozuo important development industries, service industry development policy and talent training. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2514
Volume: 11
Issue: 5
Page: 2763-2770
Publish at: 2013-05-01

An Efficient Approach To Voltage Stability Evaluation Using Tellegen’s Equations

https://ijece.iaescore.com/index.php/IJECE/article/view/5471
Payman Mohammadi , Hamid Lesani
In this paper, the adjoint networks based on Tellegen’s Theorem are used to improve the PV curve assessment. PV curve is the most widely accepted method for determining the margin of the power system state to the voltage collapse point. The repetitive power flow and continuation power flow are used to access PV curves through tracing the power flow solutions for the change of loads. Since the Minimum Jacobi matrix eigenvalue is practically close to zero at neighbor voltage collapse point, there is a restriction in order to access the voltage stability level by repetitive power flow method. This problem solved by appropriate combination of adjoint networks based on Tellegen’s Theorem and conventional equations. The proposed method was tested on SWCC test system. Comparison of three method results show advantages and efficiency of the proposed method.DOI:http://dx.doi.org/10.11591/ijece.v3i2.1964
Volume: 3
Issue: 2
Page: 158-163
Publish at: 2013-04-02

Velocity Perception: Collision Handling Technique for Agent Avoidance Behavior

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2224
Nazreen Abdullasim , Ahmad Hoirul Basori , Md Sah Hj Salam , Abdullah Bade
Collision avoidance behavior is always about maintaining free collision between virtual objects. It is also about generating evasion routing for the agents in virtual environment such as in crowd simulation. It consists of three processes which are construction of Field of Vision, Collision handling and collision response. Constructing field of vision is always a daunting task and always in enigma for the designer because it is subjected towards agent’s perception which is varies to each of them. There are few attempts on designing field of vision based on the agent’s dynamic focus toward its surrounding. Therefore, we present a top down approach study from crowd simulation modeling until the collision handling level in order to identify the suitable crowd modeling for our approach. Hence, at the end of this paper we will be able to discuss the possible techniques for constructing agent’s field of vision and analyze its potential in crowd simulation environment. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2599
Volume: 11
Issue: 4
Page: 2264-2270
Publish at: 2013-04-01

DMC Based on Weighting Correction of Predictive Model Errors

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2217
Liu Yumin , Sun Yonghe , XU Fengming , Wang Tao
Ordinary dynamic matrix predictive control (DMC) correct predictive value only using current error, so the correction is not enough. This paper proposes an algorithm. In error correction, it introduces predictive model error and predictive value are weighting corrected to improve the capability of resisting disturbance and regulating speed of the control system. By theoretical analysis and simulation, it has been proven that the algorithm is effective. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2428
Volume: 11
Issue: 4
Page: 2209-2213
Publish at: 2013-04-01

Evaluation of Power System Reliability Considering Direct Load Control Effects

https://ijece.iaescore.com/index.php/IJECE/article/view/5482
Ali Mansouri , Ali Aazami , Amin Omidian , Ehsan Mohamadian , Rahmat Aazami
With the development of deregulated power systems and increase of prices in some hours of day, demand side management programs were noticed more by customers. In restructured power systems, DSM programs are introduced as DEMAND RESPONSE. In this paper we try to evaluate the effect of DR programs on power system reliability and nodal reliability. In order to reach to this target, Direct Load Control program, as the most common demand response program, is considered. Effects of demand response programs on system and nodal reliability of a deregulated power system are investigated using direct load control and economic load model, DC power-flow-based optimal load curtailment objective and reliability evaluation techniques. The proposed method is evaluated by numerical studies based on a small reliability test system (RBTS), and simulation results show that demand response program can improve the system and nodal reliability.DOI:http://dx.doi.org/10.11591/ijece.v3i2.2295
Volume: 3
Issue: 2
Page: 254-259
Publish at: 2013-04-01

Speckle Reduction of Ultrasound Elastography with Bilateral Filter

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2164
Xiaoming Zhou , Wen Liu , Dong C. Liu
Ultrasound elastography has been well applied in early tumor diagnosis for obtaining tissue stiffness information. Elastograpyy may provide useful clinical information for the tissue characterization. But ultrasonic wave interference will produce speckle in both phase and envelope. So in conventional ultrasound elastography, there are noise artifacts which produce some misdiagnosis. In this paper, we investigate bilateral filter de-noising method to reduce the speckle. Because the bilateral filter de-noising method can greatly smooth the speckle at the same time protect the lesion edge well, it has been well proved good impact in B-mode. But in ultrasound elastography, the bilateral filter hasn’t been used. So we use the bilateral filter to reduce artifacts to prove the performance of this method .In the experiment, because of the bilateral filter de-noising method, the noise artifacts will be reduced largely. We use SNRe and CNRe to verify the performance of the bilateral filter and finally this method proved a significant improvement to SNRe and CNRe. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2343
Volume: 11
Issue: 4
Page: 1868-1870
Publish at: 2013-04-01

Experimental Research on Failure Behavior of Soil around Pile under Compression

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2187
Yongmei Qian , Guanghan Xu , Ruozhu Wang
Through small scale model laboratory experiments, the article proves that the effect of pile and soil work together of Push-extend Multi-under-reamed Pile under compression, and identifies failure modes and failure principle of soil around the pile, and for further determining ultimate bearing capacity of soil under compressive state about the Push-extend Multi-under-reamed Pile, it provides a reliable foundation. At the same time, this article provides a new method for laboratory test, which calls small scale model laboratory experiments used for research about soil body failure states of pile foundation. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2377
Volume: 11
Issue: 4
Page: 2013-2017
Publish at: 2013-04-01

A Robust Steganography method Using Adjustable Parameters

https://ijece.iaescore.com/index.php/IJECE/article/view/5476
Ahmad Reza Eskandari
In this paper, a new steganography method based on contourlet transform is presented. Compared with the previous works, the proposed method causes far fewer distortions in high frequency coefficients. This significantly increases the quality of stegano image and extracted secret image and its robustness against to steganalysis algorithm. Furthermore, we proposed two adjustable parameters that could be suited in direction of changing the quality of stegano image and extracted secret images or its robustness against to attacks and steganalysis algorithms. Using these parameters, much better performance of storing data is accessible. The proposed algorithm has higher robustness against to steganalysis algorithm in comparison with related state of the art methods. Likewise, the experimental results show robustness respect to Gaussian noise and other attacks such as JPEG compression.DOI:http://dx.doi.org/10.11591/ijece.v3i2.2236
Volume: 3
Issue: 2
Page: 207-214
Publish at: 2013-04-01

Study on Fault Current of DFIG during Slight Fault Condition

https://ijeecs.iaescore.com/index.php/IJEECS/article/view/2219
Xiangping Kong , Zhe Zhang , Xianggen Yin , Zhenxing Li
In order to ensure the safety of DFIG when severe fault happens, crowbar protection is adopted. But during slight fault condition, the crowbar protection will not trip, and the DFIG is still excited by AC-DC-AC converter. In this condition, operation characteristics of the converter have large influence on the fault current characteristics of DFIG. By theoretical analysis and digital simulation, the fault current characteristics of DFIG during slight voltage dips are studied. And the influence of controller parameters of converter on the fault current characteristics is analyzed emphatically. It builds a basis for the construction of relay protection which is suitable for the power gird with accession of DFIG. DOI: http://dx.doi.org/10.11591/telkomnika.v11i4.2542
Volume: 11
Issue: 4
Page: 2221-2230
Publish at: 2013-04-01
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