2019-05-23T12:27:21Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=347
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
DiReT: An effective discriminative dimensionality reduction approach for multi-source transfer learning
J.
Tahmoresnezhad
S.
Hashemi
Transfer learning is a well-known solution to the problem of domain shift in which source domain (training set) and target domain (test set) are drawn from different distributions. In the absence of domain shift, discriminative dimensionality reduction approaches could classify target data with acceptable accuracy. However, distribution difference across source and target domains degrades the performance of dimensionality<br />reduction methods. In this paper, we propose a Discriminative Dimensionality Reduction approach for multi-source Transfer learning, DiReT, in which discrimination is exploited on transferred data. DiReT nds an embedded space, such that the distribution dierence<br />of the source and target domains is minimized. Moreover, DiReT employs multiple source<br />domains and semi-supervised target domain to transfer knowledge from multiple resources,<br />and it also bridges across source and target domains to nd common knowledge in an<br />embedded space. Empirical evidence of real and articial datasets indicates that DiReT<br />manages to improve substantially over dimensionality reduction approaches.
Multi-source transfer learning
Domain adaptation
Discriminative dimensionality reduction
Fisher discriminant analysis
2017
06
01
1303
1311
http://scientiairanica.sharif.edu/article_4113_daa2cf1b28ae27e3c0fb4de485ab84cd.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Frequency-domain-based switching median filter for the restoration of images corrupted with high-density periodic noise
J.
Varghese
The paper proposes an adaptive Frequency-Domain-based Switching Median Filter (FDSMF) for the restoration of images corrupted by periodic noise. The proposed algorithm incorporates region-growing technique to eectively identify noisy peak areas of the Fourier transformed image in a binary noise map image. The restoration phase of the algorithm replaces the corrupted frequencies with the median of uncorrupted frequencies by recursive median lter. Experimental results from dierent naturally and articially corrupted images at various noise levels/types reveal that the performance of the proposed algorithm in restoring images corrupted by periodic noise is better than other competing algorithms in terms of subjective and objective metrics.
Periodic noise
Quasi-periodic noise
Median filter
Adaptive filter
Image restoration
Non-linear filter
2017
06
01
1312
1324
http://scientiairanica.sharif.edu/article_4114_58df0469f60c7c7ec45221e0d7e661d9.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Effiiently computing the smallest axis-parallel squares spanning all colors
P.
Khanteimouri
A.
Mohades
M.A.
Abam
M.R.
Kazemi
S.
Sedighin
For a set of colored points, a region is called color-spanning if it contains at least one point of each color. In this paper, we rst consider the problem of maintaining the smallest color-spanning interval for a set of n points with k colors on the real line, such that the insertion and deletion of an arbitrary point takes O(log2 n) the worst-case time. Then, we exploit the data structure to show that there is O(n log2 n) time algorithm to<br />compute the smallest color-spanning square for a set of n points with k colors in the plane. This is a new way to improve O(nk log n) time algorithm presented by Abellanas et al. [1] when k = !(log n). We also consider the problem of computing the smallest color-spanning square in a special case in which we have, at most, two points from each color. We present O(n log n) time algorithm to solve the problem which improves the result presented by Arkin et al. [2] by a factor of log n.
algorithm
Location planning
Dynamic data structure
Color-spanning objects
2017
06
01
1325
1334
http://scientiairanica.sharif.edu/article_4115_cb4ed198903fbb95043c785180d4b344.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Time complexity of two disjoint simple paths
M.
Razzazi
A.
Sepahvand
Finding two disjoint simple paths on two given sets of points is a geometric problem introduced by Je Erickson. This problem has various applications in computational geometry, e.g. robot motion planning, generating polygon, etc. We willm present a reduction from planar Hamiltonian path to this problem, and prove that it is NPcomplete. To the best of our knowledge, no study has considered its complexity up until now. We also present a reduction from planar Hamiltonian path problem to the problem of nding a path on given points in the presence of arbitrary obstacles" and prove that it is also NP-complete. Also, we present a heuristic algorithm with time complexity of O(n4) to solve this problem. The proposed algorithm rst calculates the convex hull for each of the entry points and then produces two simple paths on the two entry point sets.
Hamiltonian path
NP-complete
Planar graph
Simple path
2017
06
01
1335
1343
http://scientiairanica.sharif.edu/article_4116_eb58976172267e329120321fe7774f09.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Optimization of magnetic devices using Surface Current Method (SCM)
M.
Arehpanahi
E.
Hesam
In this paper, application of the Surface Current Method (SCM) in analysis and optimization of electromechanical devices is proposed. SCM is one of the numerical techniques in electromagnetic field analysis. In SCM, only magnetic boundaries are subdivided against Finite Element Method (FEM) which is subdivided into all of domains; therefore, the calculation resources of SCM are much lower than FEM. SCM with<br />low-calculation resource is one of the best numerical techniques for magnetic devices' optimization. In this paper, using SCM, three electromechanical systems have been optimized based on minimization of weight per force. Verication of simulation results is done by FEM.
optimization
Surface current method
Electric magnet and finite element method
2017
06
01
1345
1352
http://scientiairanica.sharif.edu/article_4117_fd84275243b07b9a799572fe2eab2e54.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Amplitude reconstruction of clipped OFDM by using DFT-based least squares
A.
Ahmadi
S.
Talebi
OFDM is an eective multicarrier transmission technique with one primary disadvantage; it suers from high Peak-to-Average Power Ratio (PAPR). Although clipping and ltering is a simple and eective method for PAPR reduction, it makes in-band and out-of-band noise, which degrades the bit error rate performance and spectral eficiency. Publications on this subject show that clipped samples could be reconstructed at the receiver by using oversampled signal and bandwidth expansion. By building on published literature, this paper aims to achieve a low-complexity method. The proposed method has complexity order of O(L2) to solve linear system, where L indicates the number of clipped samples. Simulation results conrm that our proposed method leads to both a better biterror rate performance and a lower complexity than similar methods. These results also show that our method oers adequate performance, especially at low clipping ratios.
OFDM
PAPR
Clipping
DFT-based least squares
Fast amplitude reconstruction
2017
06
01
1353
1362
http://scientiairanica.sharif.edu/article_4118_01504c5bb4a32b9ab1811cc98a24192a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
A new algorithm for the computation of the decimals of the inverse
P.
Saha
D.
Kumar
Ancient mathematical formulae can be directly applied to the optimization of the algebraic computation. A new algorithm used to compute decimals of the inverse based on such ancient mathematics is reported in this paper. Sahayaks (auxiliary fraction) sutra has been used for the hardware implementation of the decimals of the inverse. On account of the ancient formulae, reciprocal approximation of numbers can generate on the <br />y" either the rst exact n decimal of inverse, n being either arbitrary large or at least 6 in almost all cases. The reported algorithm has been implemented, and functionality has been checked in T-Spice. Performance parameters, like propagation delay and dynamic switching power consumptions, are calculated through spice-spectre of 90 nm CMOS technology. The propagation delay of the resulting 4-digit reciprocal approximation algorithm was only 1:8 uS and consumed 24:7 mW power. The implementation methodology offered substantial reduction of propagation delay and dynamic switching power consumption from its counterpart (NR) based implementation.
algorithm
Arithmetic
Decimal inverse
T-Spice
Propagation delay
Ancient mathematics
2017
06
01
1363
1372
http://scientiairanica.sharif.edu/article_4119_1e9d03f3bda660d71a8869c6b2b7c2b1.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Using integrated method to rank the power system contingency
M.
Simab
S.
Chatrsimab
S.
Yazdi
A.
Simab
Contingency ranking is one of the most important stages in the analysis of power system security. In this paper, an integrated algorithm has been proposed to address this issue. This algorithm employs neural networks method to quickly estimate the power system parameters and Stochastic Frontier Analysis (SFA) in order to calculate the eciency of each contingency. Network security indices (voltage violation and line <br />flow violation) and economic indices (locational marginal price and congestion cost) have been simultaneously considered to rank the contingencies. The eciency of each contingency shows its severity, and indicates that it aects network security and economic indices concurrently. The proposed algorithm has been tested on IEEE 14-bus and 30-bus test power systems. Simulation results show the high eciency of the algorithm. Test results<br />indicate that predicted quantities are estimated accurately and quickly. The proposed method is capable of producing fast and accurate network security and economic indices, so that it can be used for online ranking.
Contingency ranking
Neural network
Network security indices
Power system security
Stochastic frontier analysis
2017
06
01
1373
1383
http://scientiairanica.sharif.edu/article_4120_cb327707866201e0af24ff86b1469718.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Recognizing traffic signs using flexible Discrete Cosine Transform (DCT) grid
S.K.
Noon
K.
Javed
A.
Mannan
H.A.
Babri
Traffic sign recognition can be performed in two phases of detection and recognition; detection deals with sensing a trac sign in real-world image or video frame while recognition is about reading its contents. A traffic signs database may contain samples with varying font sizes and styles used for printing the interior of a traffic sign and the contents may also be shifted away from the center of gravity. In this paper, we utilize the energy compaction property of Discrete Cosine Transform (DCT) to propose a Trac Sign Recognition (TSR) system, which can generate invariant features for varying font styles and scaled up, scaled down, and translated contents of a sign. Experiments on synthetic and real-world images datasets show that the features generated by our proposed method have great intra-class similarity and inter-class variation. We have also shown that our proposed method outperforms Eigen based recognition method [1] and is comparable with the Histogram of Oriented Gradient (HOG) approach [2] using Support Vector Machine (SVM) classier.
2017
06
01
1384
1394
http://scientiairanica.sharif.edu/article_4121_a5b9e32ea1a6c266bfc30254470be63b.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
A novel time varying dynamic modeling for hysteresis motor
A.
Halvaei Niasar
Hysteresis motors are used in special applications such as gyroscope and gascentrifuge due to their unique features such as synchronism, self-starting, and developing smooth torque. Dynamic modeling of hysteresis motors is essential to the prediction of the transient performance, the study of the dynamic stability, the development of modern closed-loop control, and the estimation strategies. This paper develops a new time varying Dynamic model for a high-speed, circumferential- flux type hysteresis motor, in which the parameters of equivalent circuit of rotor's material are adjusted based on operational B-H loop. For this purpose and based on the elliptical assumption about B - H loops, the hysteresis lag angle, , is updated due to the applied stator voltage and available load torque. Developed mathematical model satises many theoretical aspects of hysteresis motor behavior in transient and steady-state situations. The model offers a tool to study the start-up of hysteresis motor, the change of stator voltage, the variation of load torque, the frequency tracking of variable-speed applications, and transient-state response to design parameters. Some simulations are provided to demonstrate the validity of developed model in Matlab/Simulink and are veried by some experimental results. The proposed results verify the advantages of this model over previous research works.
Dynamic Modeling
Hysteresis motor
Simulation
Transient
Circumferential- Flux
2017
06
01
1395
1409
http://scientiairanica.sharif.edu/article_4122_99a70a31fe919cd0948920264409e00e.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Nonsingular fast terminal sliding-mode stabilizer for a class of uncertain nonlinear systems based on disturbance observer
S.
Mobayen
F.
Tchier
This paper investigates a novel nonsingular fast terminal sliding-mode control method for the stabilization of the uncertain time-varying and nonlinear thirdorder systems. The designed disturbance observer satises the nite-time convergence of the disturbance approximation error and the suggested nite-time stabilizer assures<br />the presence of the switching behavior around the switching curve in the nite time. Furthermore, this approach can overcome the singularity problem of the fast terminal sliding-mode control technique. Moreover, knowledge about the upper bounds of the disturbances is not required and the chattering problem is eliminated. Usefulness and effectiveness of the offered procedure are conrmed by numerical simulation results.
Finite-time stabilizer
nonsingular fast terminal sliding mode
third-order system
disturbance observer
robustness
2017
06
01
1410
1418
http://scientiairanica.sharif.edu/article_4123_4f7cf0ef6ee7d45c15a3a26acc031cd2.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Repeating average filter for noisy texture classification
M.H.
Shakoor
F.
Tajeripour
In this paper, it is shown that repeating average lter increases the uniform patterns of noisy textures and, consequently, increases the classication accuracy of textures. In other words, for noisy textures, rst, an average lter, such as 3 3 mean filter, is applied to each image; then, a feature extraction method, such as LBP, is used to extract features of the ltered image. The more value of noise, the more repeating of average lter should be applied to textures. Moreover, it is shown that by repeating the 3 3 average lter for textures, the variance of texture decreases, then increases. Thus, average lter must be repeated while the variance of image decreases and when the variance starts increasing, it must be stopped. Using convolution to apply average lter for an image takes so much time; therefore, a simple technique is proposed in this paper that increases the speed of average ltering signicantly. After noise reduction, by using LBP operator, features of texture are extracted for classication. Implementations on Outex, CUReT, and UIUC datasets determine that the performance of the proposed method is better than that of some advanced noise-resistant LBP variants such as BRINT and CRLBP.
Local binary pattern
Texture classification
Repeating average filter
Completed local binary pattern
Noise robustness
2017
06
01
1419
1436
http://scientiairanica.sharif.edu/article_4124_48664dfe925db34a0bd22d20bc4a2d4e.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Spectral method for PEMFC operation mode monitoring based on electrical fluctuation analysis
E.
Denisov
Yu.K.
Evdokimov
R.R.
Nigmatullin
S.
Martemianov
A.
Thomas
N.
Adiutantov
This work considers the possibility of applying electrochemical noise analysis to fuel cell diagnostics. Theoretical hypothesis and experimental result have shown that spectral characteristics of electrical <br />fluctuations depend on water management processes inside the PEMFC. It has been established that the spectrum of electrical fluctuations in low frequency range has the nature of flicker noise. The frequency ranges of 0.1-1 Hz convenient for single cell as well as for stack diagnostics are revealed. The results show that the proposed approach can be considered as an effective tool to diagnose of fuel cells, namely allowing for prediction of drying and flooding.
Fuel cell
Technical diagnostics
Flicker noise
Water management
2017
06
01
1437
1447
http://scientiairanica.sharif.edu/article_4125_092a0444667c07c5b98aab07f61dc32d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
A lattice-based changeable threshold multi-secret sharing scheme and its application to threshold cryptography
H.
Pilaram
T.
Eghlidos
In this paper, we propose a threshold increasing algorithm for a (t; n) latticebased Threshold Multi-Stage Secret Sharing (TMSSS) scheme. To realize the changeability feature, we use the zero addition protocol to construct a new (t0; n) TMSSS scheme. Therefore, the new scheme enjoys the signicant feature of threshold changeability along with the inherited features of being multi-stage, multi-use, and veriable derived from<br />our previously proposed lattice-based TMSSS scheme. Furthermore, we use the improved TMSSS scheme to propose a threshold decryption algorithm for the Learning With Error (LWE) based public key encryption scheme based on the study of Lindner and Peikert. For threshold decryption, each authorized subset of participants decrypts the ciphertext partially and sends the result to the combiner. The combiner can decrypt the ciphertext using the partial decryptions. The security of both schemes is based on hardness of lattice problems, i.e. LWE and Inhomogeneous Small Integer Solution (ISIS) problems, which are believed to resist against the quantum algorithms. The proposed schemes are eficient, especially on the participants' side, making them suitable for the applications in which the participants have limited processing capacities.
Threshold multi-stage secret sharing
Changeable threshold secret sharing
Threshold decryption
Lattice-based Cryptography
2017
06
01
1448
1457
http://scientiairanica.sharif.edu/article_4126_6d7a452961a54b3caefc69a62e78deae.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Enhancing power system transient stability using optimal unified power flow controller based on Lyapunov control strategy
P.
Avaz Pour
A.
Lashkar Ara
S.A.
Nabavi Niaki
This paper presents a new control strategy for an Optimal Unied Power Flow Controller (OUPFC) through a Lyapunov energy function in terms of local parameters to improve the transient stability of a power system. The OUPFC is a hybrid conguration of Flexible AC Transmission System (FACTS) devices, i.e. an arrangement of small-sized Unied Power Flow Controller (UPFC) and a full-scale Phase Shifting Transformer (PST).<br />In this study, a new term of OUPFC's energy function and its injection model in a simplied structure preserving model is developed and implemented in a two-machine power system using MATLAB/Simpower. The ability of the OUPFC controller to enhance the transient stability is compared to that of UPFC. The results show that using the proposed control strategy for OUPFC leads to more abatement of the rst swing oscillations and enlargement of stability margin. It is concluded that compensation of UPFC's angle displacement may<br />come true using OUPFC with appropriate angles in proper locations. So, compared to UPFC, OUPFC enjoys another degree of freedom.
OUPFC
UPFC
FACTS
CLF
Lyapunov
2017
06
01
1458
1466
http://scientiairanica.sharif.edu/article_4127_d5dc96faaff6cc39ed766728441d204a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
3
Robust fault detection and isolation scheme using fuzzy wavelet network with a hybrid design algorithm
M.
Shahriari-kahkeshi
This paper presents a new robust fault detection and isolation scheme using fuzzy wavelet network based on the bounded error approach. An ecient hybrid design algorithm, which consists of the orthogonal least square and the articial bee colony algorithms, is proposed to design fuzzy wavelet network for modeling normal and faulty behaviors of the system. The proposed model provides an alternative description of the behavior of the system with high accuracy, but it suers from model uncertainty because of model-reality mismatch in practical applications. To overcome this diculty, the bounded error approach inspired from robust identication theory is applied to estimate the model uncertainty which denes a condence interval of the model output and derives adaptive threshold for residual evaluation. Also, online fault isolation process is performed using fuzzy wavelet network models of the faulty system and analyzing the relation between a bank of residuals. Performance and eciency of the proposed scheme is evaluated by simulating the nonlinear two-tank liquid level control system. Finally, some performance indexes are dened, and then the Monte-Carlo analysis is carried out to evaluate the reliability and robustness of the proposed scheme.<br /><br />
Robust fault detection and isolation
Fuzzy wavelet network
Adaptive threshold generation
Bounded-error approach
artificial bee colony algorithm
2017
06
01
1467
1481
http://scientiairanica.sharif.edu/article_4128_120a7a4ff8d2935c5d26413f686639f5.pdf