Showing 12 results for Error
Sh. Mohammad-Nejad, M. Pourmahyabadi, A. Lajevardizadeh,
Volume 2, Issue 3 (7-2006)
Abstract
In this paper, the performance of a Ring Laser Gyro based inertial navigation is
investigated. Dynamic and stochastic modeling are applied to gyro simulation and
performance evaluation. In the dynamic model, some parameters such as scale factor and
environmental sensitivity have been determined, whereas in the stochastic model, the other
parameters such as random drift and measurement noise have been computed. The
performance of the system is evaluated for several inputs. Also, the parameter variation of
output noise as a result of changing the dither characteristics is analyzed.
H. Ghanei Yakhdan, M. Khademi, J. Chitizadeh,
Volume 5, Issue 1 (3-2009)
Abstract
The performance of video transmission over wireless channels is limited by the
channel noise. Thus many error resilience tools have been incorporated into the MPEG-4
video compression method. In addition to these tools, the unequal error protection (UEP)
technique has been proposed to protect the different parts in an MPEG-4 video packet with
different channel coding rates based on the rate compatible punctured convolutional
(RCPC) codes. However, it is still not powerful enough for the noisy channels. To provide
more robust MPEG-4 video transmission, this paper proposes a modified unequal error
protection technique based on the mutual information of two video frames. In the proposed
technique, the dynamic channel coder rates are determined online based on the mutual
information of two consecutive video frames. With this technique, irregular and high
motion areas that are more sensitive to errors can get more protection. Simulation results
show that the proposed technique enhances both subjective visual quality and average peak
signal to noise ratio (PSNR) about 2.5 dB, comparing to the traditional UEP method.
M. Esmaili, H. A Shayanfar, N. Amjady,
Volume 6, Issue 1 (3-2010)
Abstract
Congestion management in electricity markets is traditionally done using deterministic values of power system parameters considering a fixed network configuration. In this paper, a stochastic programming framework is proposed for congestion management considering the power system uncertainties. The uncertainty sources that are modeled in the proposed stochastic framework consist of contingencies of generating units and branches as well as load forecast errors. The Forced Outage Rate of equipment and the normal distribution function to model load forecast errors are employed in the stochastic programming. Using the roulette wheel mechanism and Monte-Carlo analysis, possible scenarios of power system operating states are generated and a probability is assigned to each scenario. Scenario reduction is adopted as a tradeoff between computation time and solution accuracy. After scenario reduction, stochastic congestion management solution is extracted by aggregation of solutions obtained from feasible scenarios. Congestion management using the proposed stochastic framework provides a more realistic solution compared with the deterministic solution by a reasonable uncertainty cost. Results of testing the proposed stochastic congestion management on the 24-bus reliability test system indicate the efficiency of the proposed framework.
H. Abbasi, A. Gholami, A. Abbasi, ,
Volume 7, Issue 1 (3-2011)
Abstract
This paper consist of two sections: control and stabilizing approach for chaotic behaviour of converter is introduced in first section of this paper for the removal of harmonic caused by the chaotic behaviour in current converter. For this work, a Time- Delayed Feedback Controller (TDFC) control method for stability chaotic behaviour of buck converter for switching courses in current control mode is presented. This behaviour is demonstrated by presenting a piecewise linear discrete map for this converter and then combining the feedback equation to obtain the overall equation of the converter. A simple time-delay feedback control method is applied to stabilize the Unstable Periodic Orbits (UPOs). In second section is studied the effect of a parallel metal oxide surge arrester on the ferroresonance oscillations of the transformer. It is expected that the arresters generally cause ferroresonance drop out. Simulation has been done on a three phase power transformer with one open phase. Effect of varying input voltage has been studied. The simulation results reveal that connecting the arrester to the transformer poles, exhibits a great mitigating effect on ferroresonant over voltages. Phase plane along with bifurcation diagrams are also presented. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos and magnitude of ferroresonant voltages has been obtained, shown and tabulated.
H. Radmanesh, M. Rostami,
Volume 7, Issue 4 (12-2011)
Abstract
this work studies the effect of neutral earth resistance on the controlling ferroresonance oscillation in the power transformer including MOV surge arrester. A simple case of ferroresonance circuit in a three phase transformer is used to show this phenomenon and the three-phase transformer core structures including nonlinear core losses are discussed. The effect of MOV surge arrester and neutral earth resistance on the onset of chaotic ferroresonance and controlling chaotic transient in a power transformer including nonlinear core losses has been studied. It is expected that these resistances generally cause into ferroresonance control. Simulation has been done on a power transformer rated 50 MVA, 635.1 kV with one open phase. The magnetization characteristic of the transformer is modelled by a single-value two-term polynomial with q=7, 11. The core losses are modelled by third order in terms of voltage. The simulation results reveal that connecting the MOV arrester and neutral resistance to the transformer, exhibits a great impact on ferroresonance over voltages.
Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved.
S. M. Marvasti Zadeh, H. Ghanei Yakhdan, Sh. Kasaei,
Volume 10, Issue 3 (9-2014)
Abstract
Sending compressed video data in error-prone environments (like the Internet and wireless networks) might cause data degradation. Error concealment techniques try to conceal the received data in the decoder side. In this paper, an adaptive boundary matching algorithm is presented for recovering the damaged motion vectors (MVs). This algorithm uses an outer boundary matching or directional temporal boundary matching method to compare every boundary of candidate macroblocks (MBs), adaptively. It gives a specific weight according to the accuracy of each boundary of the damaged MB. Moreover, if each of the adjacent MBs is already concealed, different weights are given to the boundaries. Finally, the MV with minimum adaptive boundary distortion is selected as the MV of the damaged MB. Experimental results show that the proposed algorithm can improve both objective and subjective quality of reconstructed frames without any considerable computational complexity The average PSNR in some frames of test sequences increases about 4.59, 4.44, 3.57, and 2.98 dB compared to classic boundary matching, directional boundary matching, directional temporal boundary matching, and outer boundary matching algorithm, respectively.
A. A. Abedi, M. R. Mosavi, K. Mohammadi, M. R. Daliri,
Volume 12, Issue 3 (9-2016)
Abstract
One of the instruments for determination of position used in several applications is the Global Positioning System (GPS). With a cheap GPS receiver, we can easily find the approximate position of an object. Accuracy estimation depends on some parameters such as dilution of precision, atmospheric error, receiver noise, and multipath. In this study, position accuracy with GPS receiver is classified in three classes. Nine classification methods are utilized and compared. Finally, a new method is selected for classification. Results are verified with experimental data. Success rate for classificationis approximately 84%.
M. Soleimani, S. Toofan,
Volume 14, Issue 3 (9-2018)
Abstract
This paper presents a high-speed, low-power and low area encoder for implementation of flash ADCs. Key technique for design of this encoder is performed by convert the conventional 1-of-N thermometer code to 2-of-M codes (M = ¾ N). The proposed encoder is composed from two-stage; in the first stage, thermometer code are converted to 2-of-M codes by used 2-input AND and 4-input compound AND-OR gates. In the second stage by two ROM encoders, 2-of-M codes determine n-1 MSB bits and one LSB bit. The advantages of the proposed encoder rather than other similar works are high speed, low power consumption, low active area, and low latency with same bubble error removing capability. To demonstrate the mention specifications, 5-bit flash ADCs with conventional and proposed encoders in their encoder blocks, are simulated at 2-GS/s and 3.5-GS/s sampling rates in 0.18-μm CMOS process. Simulation results show that the ENOB of flash ADCs with conventional and proposed encoders are equal. In this case, the proposed encoder outputs are determined almost 30-ps faster rather than the conventional encoder at 2-GS/s. Also, the power consumptions of the conventional and proposed encoders were 17.94-mW and 11.74-mW at 3.5-GS/s sampling rate from a 1.8-V supply, respectively. Corresponding, latencies of the conventional and proposed encoders were 3 and 2 clock cycles. In this case, number of TSPC D-FFs and logic gates of the proposed encoder is decreased almost 39% compared to the conventional encoder.
V. Abbasi,
Volume 14, Issue 3 (9-2018)
Abstract
Cable termination faults are problematic in electrical networks almost always. Technology has solved problems somewhat, but there are many annual reports about damaged cable terminations. For analyzing the problems, faults in two regional electricity companies are studied. At first step, damaged cable terminations are analyzed statistically and grouped according to their problems. Then, some of the damaged cable terminations are checked to classify vulnerable areas. The investigation is completed by simulation, analysis and study of equivalent circuit. Conclusions underline important points which can be helpful for reducing the damages.
A. Hassannejad Marzouni, A. Zakariazadeh,
Volume 16, Issue 3 (9-2020)
Abstract
State estimation is essential to access observable network models for online monitoring and analyzing of power systems. Due to the integration of distributed energy resources and new technologies, state estimation in distribution systems would be necessary. However, accurate input data are essential for an accurate estimation along with knowledge on the possible correlation between the real and pseudo measurements data. This study presents a new approach to model errors for the distribution system state estimation purpose. In this paper, pseudo measurements are generated using a couple of real measurements data by means of the artificial neural network method. In the proposed method, the radial basis function network with the Gaussian kernel is also implemented to decompose pseudo measurements into several components. The robustness of the proposed error modeling method is assessed on IEEE 123-bus distribution test system where the problem is optimized by the imperialist competitive algorithm. The results evidence that the proposed method causes to increase in detachment accuracy of error components which results in presenting higher quality output in the distribution state estimation.
S. M. Zabihi, H. Ghanei-Yakhdan, N. Mehrshad,
Volume 16, Issue 4 (12-2020)
Abstract
In order to enhance the accuracy of the motion vector (MV) estimation and also reduce the error propagation issue during the estimation, in this paper, a new adaptive error concealment (EC) approach is proposed based on the information extracted from the video scene. In this regard, the motion information of the video scene around the degraded MB is first analyzed to estimate the motion type of the degraded MB. If the neighboring MBs possess uniform motion, the degraded MB imitates the behavior of neighboring MBs by choosing the MV of the collocated MB. Otherwise, the lost MV is estimated through the second proposed EC technique (i.e., IOBMA). In the IOBMA, unlike the conventional boundary matching criterion-based EC techniques, not only each boundary distortion is evaluated regarding both the luminance and the chrominance components of the boundary pixels, but also the total boundary distortion corresponding to each candidate MV is calculated as the weighted average of the available boundary distortions. Compared with the state-of-the-art EC techniques, the simulation results indicate the superiority of the proposed EC approach in terms of both the objective and subjective quality assessments.
A. Mirsamadi, Y. Damchi, M. Assili,
Volume 17, Issue 1 (3-2021)
Abstract
Power systems should have acceptable reliability in order to operate properly. Highly available and dependable protective relays help to obtain the desirable reliability. The relays should be periodically evaluated during specific intervals to achieve the mentioned characteristics. The Routine Test Interval (RTI) should be optimized in order to economically maximize the reliability of the protection system. The failure rate of the relays plays a vital role in determination of the Optimum Routine Test Interval (ORTI). Human error is one of the effective factors in the failure rate of the relays. Therefore, in this paper, a Markov model is proposed to investigate the impact of human error on the failure rate and the ORTI of the protection system. The model is applied for the protection system of power transformer. The obtained results indicated that human error has a significant impact on the increase of protection system failure, the decrease of the desired reliability indices, and the reduction of ORTI of the protection system.
