Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
An 8-Bit Current-Mode Folding ADC with Optimized Active Averaging Network
2955
EN
M.
Sharif Bakhtiar
Department of Electronical Engineering,Sharif University of Technology
M.
Azin
Department of Electrical Engineering and Computer Science,Case Western Reserve University
Journal Article
2009
05
30
In this paper, an 8-bit CMOS current-mode folding-interpolating ADC is presented. A new
active averaging-interpolating network is described, which results in a better error correction
factor compared to its resistive counterpart. Using novel circuits for fast settling and careful
transistor sizing, a fast (>160 Msps) and low power (70 mW in 2.5 V supply voltage) 8-bit
ADC, with a total chip area of 1 1:4 mm in a 0.25 micron CMOS process, is demonstrated.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
A New, Publicly Veriable, Secret Sharing Scheme
2956
EN
T.
Eghlidos
Department of Mathematical Sciences,Sharif University of Technology
0000-0002-3182-0277
A.
Behnad
Department of Electrical Engineering,Sharif University of Technology
Journal Article
2009
05
30
A Publicly Veriable Secret Sharing (PVSS) scheme, as introduced by Stadler, has a feature
where anyone, besides the participants, can verify the validity of the shares distributed by
the dealer. Schoenmakers added a new feature, by providing a proof of correctness of the
shares released by the players in the reconstruction process. This protocol is claimed to
be an improvement on Stadler's and Fujisaki-Okamoto's, both in eciency and in the type
of intractability assumptions. However, Young-Yung improved Schoenmakers' PVSS, using a
Discrete-Log instead of a Decision Die-Hellman. In this paper, a new PVSS is presented,
having an intrinsic dierence with its predecessors, that is, the participants can prove the validity
of their given shares, implicitly, proving their membership by a zero-knowledge protocol. This
feature prevents cheaters from participating in the reconstruction process to gain valid shares.
Hence, the new proposed PVSS is more secure than previous ones. Besides, the dealer only
sends the amount of commitments limited to the threshold value, regardless of the number of
shareholders; this leads to a more dynamic protocol.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
Analytical Mode Distributions and Resonant Frequencies in Ladder Networks Used in Power Combining Oscillator Arrays
2957
EN
M.H.
Akbarpour
Department of Electrical Engineering,Sharif University of Technology
F.
Farzaneh
Department of Electrical Engineering,Sharif University of Technology
Journal Article
2009
05
30
An analysis of resonant modes in ladder networks is performed using dierence equations. Linear
and loop congurations are studied and analytical relations are derived for the mode distributions
and resonant frequencies of these networks, having arbitrary elements. Furthermore, it is shown
that a) Modes with an exponential distribution along network nodes may exist in some cases and
b) The mode distributions in loop networks are independent of network elements. Finally, a simple
criterion is obtained for a loop structure to control the spacing between resonant frequencies.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
Direct Introduction of Semicon Layers in a Cable Model
2958
EN
M.
Vakilian
Department of Electrical Engineering,Sharif University of Technology
Journal Article
2009
05
30
The detection and location of any Partial Discharge (PD) signal requires an accurate frequency
dependent cable model to correctly simulate the PD signal attenuation during its propagation
in the cable. This model should be capable of simulating the semiconducting layers, which have
signicant eects on PD signal attenuation and its propagation velocity. There is a substantial
need for improvements in the
exibility of the transient cable model through direct introduction
of the two semiconducting layers in the cable model. This can be employed in the next step
to develop a 3-phase cable model for ATP. This paper has derived an impedance formula for
the semiconducting layers. The propagation characteristics of the PD signal, in a cable having
two semiconducting layers, are evaluated by applying the derived formula and are compared with
the related characteristics in a cable with no semiconducting layer. The propagation of a PD
signal applied to the sending end of the core conductor is investigated. In the application of the
semicon pick-up sensor in the cable joint, there would be a considerable high frequency voltage
across each semiconducting layer, which can be used for the study of PD phenomenon.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
A Variational Iteration Method for Solving Systems of Partial Dierential Equations and for Numerical Simulation of the Reaction-Diusion Brusselator Model
2959
EN
Y.
Jalilian
Department of Mathematical Sciences,Sharif University of Technology
Journal Article
2009
05
30
In this work, systems of linear and nonlinear partial dierential equations and the reactiondi
usion Brusselator model are handled by applying the variational iteration method. The
Variational iteration method has the advantage of being more concise for analytical and numerical
purposes. The results reveal that the method is very eective and convenient.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
A Two-Class M/M/1 System with Preemptive Non Real-Time Jobs and Prioritized Real-Time Jobs under Earliest-Deadline-First Policy
2960
EN
M.
Kargahi
School of Electrical and Computer Engineering,University of Tehran
A.
Movaghar
Department of Computer Engineering,Sharif University of Technology
Journal Article
2009
05
30
This paper introduces an analytical method for approximating the performance of a two-class
priority M=M=1 system. The prioritized class-1 jobs are real-time, served either with the
preemptive or non-preemptive Earliest-Deadline-First (EDF) policy and can preempt the non
real-time class-2 jobs. The preempted service of the class-2 job is resumed from the time in
instances where no class-1 job is in the system. The service discipline of class-2 jobs is FCFS.
The required mean service times may depend on the class of the jobs. The real-time jobs have
exponentially distributed relative deadlines until the end of service. The system is approximated
by a Markovian model in the long run, which can be solved numerically, using standard Markovian
solution techniques. The performance measures of the system are the loss probability of the
class-1 jobs and the mean sojourn (waiting) time of the class-2 jobs. Comparing numerical and
simulation results, it is found that the existing errors are relatively small.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
Principal Color and its Application to Color Image Segmentation
2961
EN
S.
Kasaei
Department of Computer Science and Engineering,Sharif University of Technology
A.
Abadpour
Department of Mathematical Sciences,Sharif University of Technology
Journal Article
2009
05
30
Color image segmentation is a primitive operation in many image processing and computer
vision applications. Accordingly, there exist numerous segmentation approaches in the literature,
which might be misleading for a researcher who is looking for a practical algorithm. While many
researchers are still using the tools which belong to the old color space paradigm, there is evidence
in the research established in the eighties that a proper descriptor of color vectors should act
locally in the color domain. In this paper, these results are used to propose a new color image
segmentation method. The proposed method searches for the principal colors, dened as the
intersections of the cylindrical representations of homogeneous blocks of the given image. As
such, rather than using the noisy individual pixels, which may contain many outliers, the proposed
method uses the linear representation of homogeneous blocks of the image. The paper includes
comprehensive mathematical discussion of the proposed method and experimental results to
show the eciency of the proposed algorithm.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
The Eect of an Interline Power Flow Controller (IPFC) on Damping Inter-area Oscillations in Interconnected Power Systems
2962
EN
A.
Kazemi
Biochemical and Bioenvironmental Research Center,Iran University of Science and Technology
E.
Karimi
Department of Electrical Engineering,Iran University of Science and Technology
Journal Article
2009
05
30
The eect of an Interline Power Flow Controller (IPFC) on damping low frequency oscillations
has been implied in some papers, but has not been investigated in detail. This paper investigates
the damping control function of an interline power
ow controller installed in a power system.
For this purpose, a single machine-innite bus model, integrated with IPFC, is used and the
linearized model is established. Using this model, the Phillips-Heron model of the system for
steady state digital simulations is derived. In this paper, the numerical results are presented
using the MATLAB simulink toolbox, which shows the signicant eect of IPFC on damping
inter-area oscillations.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
On Domination and its Forcing in Mycielski's Graphs
2963
EN
D.A.
Mojdeh
Department of Mathematics,University of Mazandaran
Journal Article
2009
05
30
In this paper, for a given graph, G, some domination parameters and the forcing domination
number of the graph, M(G), obtained from G arising in Mycielski's construction, are studied.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
New Wavelet-Based Approach for Internal Fault Current Identication in Power Transformers
2964
EN
H.
Monsef
Department of Electrical Engineering,University of Tehran
Journal Article
2009
05
30
This paper demonstrates a novel approach for the dierential protection of power transformers.
This method uses the Wavelet Transform (WT) and the Adaptive Network-based Fuzzy Inference
System (ANFIS) to detect a fault current from an inrush current. The proposed method has
been designed, based on the dierences between the amplitudes of wavelet transform coecients
in a special band of frequency that is caused by faults and inrush currents. The performance of
this algorithm has been simulated and tested under dierent conditions of the switching on of
power transformers, using the PSCAD/EMTDC environment software.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
Variable, Step-Size, Block Normalized, Least Mean, Square Adaptive Filter: A Unied Framework
2965
EN
A.
Mahlooji Far
Department of Electrical Engineering,Tarbiat Modares University
Journal Article
2009
05
30
Employing a recently introduced framework, within which a large number of classical and modern
adaptive lter algorithms can be viewed as special cases, a generic, variable step-size adaptive
lter has been presented. Variable Step-Size (VSS) Normalized Least Mean Square (VSSNLMS)
and VSS Ane Projection Algorithms (VSSAPA) are particular examples of adaptive algorithms
covered by this generic variable step-size adaptive lter. In this paper, the new VSS Block
Normalized Least Mean Square (VSSBNLMS) adaptive lter algorithm is introduced, based on
the generic VSS adaptive lter. The proposed algorithm shows the higher convergence rate and
lower steady-state mean square error compared to the ordinary BNLMS algorithm.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
Design of an Automatic Alignment System for Video Displays Using an Adaptive Alignment Algorithm
2966
EN
A.
Peiravi
Department of Electrical Engineering,Ferdowsi University of Mashhad
Journal Article
2009
05
30
One of the critical stages in a display production line is the image alignment of displays that
includes the precise adjustment of the geometric parameters and the color of the image. The
mutual in
uences of the parameters of the display's image necessitate a complex and interactive
alignment process. In this paper, the eect of the mutual in
uences of geometric parameters
on the alignment process of a display's image are shown, a suitable model for the geometric
characteristics of a display's image are suggested and, then, the unknown parameters of the
proposed model are estimated by the RLS estimator. Using an o-line estimator, an initial
measure of the values of the unknown parameters of the display model is obtained. To modify the
model parameters of the consecutive video displays on the production line, an on-line estimator
is applied. Variations of the parameters of the display model on a production line are traced
using on-line estimation. This model estimation is used to implement an adaptive alignment
algorithm. Both the adaptive and the proportional alignment processes have been experimentally
implemented under similar working conditions. Experimental results show that the use of the
adaptive alignment process considerably increases the speed and reliability of convergence of
geometric parameters to their desired values. An IA-32, 3.4 GHz Pentium P4 processor has been
used in this research. Considering the rapid developments in UDSM technology and the IA-64
architecture, the application of the proposed adaptive alignment algorithm in an auto-alignment
system has the potential for real-time implementation in the near future.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
A Programmable GPS Receiver with Test Circuits in 0.18 m CMOS
2967
EN
M.
Jenabi
Department of Engineering,Auburn University
A.
Fotowat Ahmady
Department of Engineering,Auburn University
N.
Riahi
Department of Engineering,Alzahra University
Journal Article
2009
05
30
A 0.18 m single chip GPS receiver, with 19.5 mA current consumption, is implemented in
6.5 mm2. Low-IF architecture was used for a high level of integration and low power consumption.
A serial input digital control, with additional testing structure, not adding more than 4% to the
Si area, is used in the actual RF circuits, in case of problems, minimizing the number of Si runs.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
On the Existence of Periodic Solutions for Nonlinear Ordinary Dierential Equations
2968
EN
D.
Shadman
Department of Mathematical Sciences,Sharif University of Technology
B.
Mehri
Department of Mathematics,Sharif University of Technology
Journal Article
2009
05
30
In this paper, the existence of periodic solutions of autonomous ordinary dierential equations of
a 4th and 5th order is investigated. The method used is based on the Brower's degree theorem
using the homotopy invariant a property of a topological degree.
Sharif University of Technology
Scientia Iranica
1026-3098
15
2
2008
04
01
GLR Detector for Coded Signals in Noise and Interference
2969
EN
M.R.
Aref
Department of Electrical Engineering,Sharif University of Technology
Journal Article
2009
05
30
In this paper, the detection of a coded signal in additive white Gaussian noise and the interference
is studied, where there is no knowledge about the correlation between the received symbols and
about the noise and interference parameters. The Maximum Likelihood (ML) estimates of the
unknown parameters are found, they are substituted in the probability density functions of the
observation and the Generalized Likelihood Ratio (GLR) detector is derived. This detector can
also be used for the activity detection of a signal in unknown Inter-Symbol Interference (ISI). In
this case, the interference is modeled as the unknown correlation between the received symbols.
Simulation examples are performed to evaluate the performance of the proposed detector.