2021-10-16T02:31:20Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=267
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
On-Chip Interconnection Network with an Ecient Parallel Buer Structure and Generic Trac Model
N.
Bagherzadeh
J.H.
Bahn
In this paper, we present two important topics indirectly related to the design and simulated
analysis of Network-on-Chip (NoC) architectures. In order to enhance the performance of the baseline
router to achieve maximum throughput,a new parallel buer architecture and its management scheme
are introduced. By adopting an adjustable architecture that integrates a parallel buer with each incoming
port, the design complexity and its utilization can be optimized. By utilizing simulation-based performance
evaluation and comparison with previous NoC architectures, its eciency and superiority are proven. One
of the key areas of research addressed in this work is to nd more realistic trac models in order to properly
test the buer management schemes proposed in this work. Therefore, we introduce a generic trac
model for on-chip interconnection networks that is superior to previous techniques for NoC architectural
performance evaluation. Our trac model is based on three empirically-derived statistical characteristics
using temporal and spatial distributions. With captured parameters, accurate trac patterns can be
generated recursively to show similar statistical characteristics of the observed on-chip networks.
Network-on-Chip
Virtual channel
Parallel buer
Router
Generic trac mode
2009
12
01
http://scientiairanica.sharif.edu/article_3275_08cdfd9e3269fb74c4bf5ad7986f952a.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
An Efficient Content-Based Video Coding Method for Distance Learning Applications
S.
Kasaei
T.
Lotfi
M.
Bagheri
A. A.
Darabi
This paper presents a novel method for cooperative educational dissemination systems.
Taking into consideration the inherent characteristics of distance learning video streams (existence of a
few slow moving objects in a classroom), we have proposed a novel content-based video coding method that
is very ecient at low bitrate channels. On the encoding side, we have applied a background subtraction
algorithm for motion segmentation using a novel statistical background modeling approach. At each frame,
the moving objects are extrapolated with a rectangular model and tracked frame by frame (which forms the
only data needed to be sent over the channel). On the decoding side, we have used a new error concealment
algorithm (based on edge information of frames) to eliminate probable channel errors in the received data.
Moreover, a new fuzzy scene modeling algorithm is proposed that adaptively computes the alpha blending
coecient (used in dynamic video mosaicing) and reconstructs the original video scene from partially
overlapped frames. Our experiments show that the proposed coding system is very ecient in real-time
video webcasting with approximately 24 fps for CIF formatted sequences (and at a minimum of 13 fps
transmission for 720576 frame sizes). Applying our proposed system has reduced the required bitrate of
H.264 and MPEG-4 coding standards by about 2.5% to 8%, respectively, with almost the same, or even
better, reconstructed video qualities.
Content-based video coding
Distance learning
Motion segmentation
Mosaicing
2009
12
01
http://scientiairanica.sharif.edu/article_3276_f3000c241017cc3ef5af11427f3561ad.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
Optimal Size and Location of Distributed Generations for Minimizing Power Losses in a Primary Distribution Network
B.
Kermanshahi
R.M.
Kamel
Power system deregulation and shortage of transmission capacities have led to an increase
interest in Distributed Generations (DGs) sources. The optimal location of DGs in power systems is
very important for obtaining their maximum potential benets. This paper presents an algorithm to
obtain the optimum size and optimum location of the DGs at any bus in the distribution network. The
proposed algorithm is based on minimizing power losses in the primary distribution network. The developed
algorithm can also be used to determine the optimum size and optimum location of the DGs embedded
in the distribution network, including power cost and the available rating of DGs if the DGs exist in
a competitive market. An algorithm is applied to three test distribution systems with dierent sizes (6
buses, 18 buses and 30 buses). Results indicated that, if the DGs are located at their optimal locations and
have optimal sizes, the total losses in the distribution network will be reduced by nearly 85%. The results
can be used as a look-up table, which can help design engineers when inserting DGs into the distribution
networks.
Distributed generation
optimal location
Optimal size
Loss minimization
2009
12
01
http://scientiairanica.sharif.edu/article_3277_af656963243bcddcb06601073fdfd597.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
Theory of Optimal Mixing in Directly Modulated Laser Diodes
B.
Cabon
S.
Khorasani
Using a simple nonlinear model based on rate equations, and by employing a harmonic
balance method, we develop a theory of optimal mixing in directly modulated semiconductor laser diodes.
We perform a consistent numerical solution to the mixing in laser diodes to the arbitrary accuracy and
intermodulation index (m; n). Through numerical computations we demonstrate that there is an optimal
bias in mixing, corresponding to a relaxation frequency, fr, coinciding with the subcarrier frequency, f1,
at which the mixing power is maximized nearly simultaneously for all intermodulation products, fmn. In
terms of increasing the signal's current amplitude, it will be shown that it would result in a monotonic
increase in the optical power of all intermodulation products, as is normally expected. More generally
and for the rst time to the best of our knowledge, the condition for optimal mixing power is found as
fmn = kfr = mf1+nf2. Applications are in data transmission beyond the resonant frequency of the laser
diode as needed in future communication standards.
Laser diode
Mixing
Microwave photonics
2009
12
01
http://scientiairanica.sharif.edu/article_3278_4bb8597650768bd9ebabddb69089d931.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
Harmonic Content and Relaxation Resonant Frequency of a Modulated Laser Diode
H.
Zandi
M.
Bavafaa
M.
Chamanzar
S.
Khorasani
In this paper, an analysis of the harmonic contents of the optical output power for an
in-plane single mode laser diode is performed, and the results are described in detail. In the rst step, the
absolute value of power for each harmonic is obtained in terms of various laser diode parameters, and the
variations of external parameters, such as modulation current, bias current and frequency, are discussed.
The analysis is done by direct solution of the rate equations of an arbitrary laser diode for carrier and
photon densities. It is known that the optical power has a nonlinear dependence on frequency, and the
maximum optical power of each harmonic is attained in its resonance frequency. The resonant frequency is
shown to be tunable by the bias current; thus we obtain exact expressions for the output power of various
harmonics, allowing better optimization to gain improved results. We extend the approach to higher
harmonics, and numerically calculate the Total Harmonic Distortion (THD) versus major parameters,
such as frequency, bias current and modulation current. Furthermore, we nd optimal operation points
in which the desired characteristics of the laser diode can be achieved. It is also possible for the sequence
for every arbitrary single-mode laser structure to be developed by the approach presented in this work.
Laser diode
Optical modulation
Relaxation resonant frequency
Total harmonic distortion
2009
12
01
http://scientiairanica.sharif.edu/article_3279_3dc33a40f139ad716f18de6f133c04f3.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
Convergence Analysis of Spline Solution of Certain Two-Point Boundary Value Problems
J.
Rashidinia
R.
Jalilian
R.
Mohammadi
The smooth approximate solution of second order boundary value problems are developed
by using non-polynomial quintic spline function. We obtained the classes of numerical methods, which are
second, fourth and six-order. For a specic choice of the parameters involved in a non-polynomial spline,
truncation errors are given. A new approach convergence analysis of the presented methods are discussed.
Three test examples are considered in our references. By considering the maximum absolute errors in
the solution at grid points and tabulated in tables for dierent choices of step size, we conclude that our
presented methods produce accurate results in comparison with those obtained by existing methods.
Two-point boundary value problem
Non-polynomial Quintic spline
Convergence analysis
2009
12
01
http://scientiairanica.sharif.edu/article_3280_7ca9e7e1289d2f6dc2edc7e5a3a0133f.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
Estimation of Hottest Spot Temperature in Power Transformer Windings with NDOF and DOF Cooling
M. A.
Taghikhani
A.
Gholami
Power transformer outages have a considerable economic impact on the operation of an
electrical network. One of the most important parameters governing a transformer's life expectancy is the
Hot-Spot Temperature (HST) value. The classical approach has been established to consider the hot-spot
temperature as the sum of the ambient temperature, the top-oil temperature rise in the tank, and the hotspot-
to-top-oil (in tank) temperature gradient. In this paper, the heat conduction equation for temperature
is solved. For numerical solution of the heat conduction equation, the nite element method is used. The
selected model for simulation is a 32MVA transformer with Non-Directed Oil-Forced (NDOF) cooling and
Directed Oil-Forced (DOF) cooling.
Power transformer
temperature distribution
Hot spot
Forced cooling
Heat equation
Finite Element
2009
12
01
http://scientiairanica.sharif.edu/article_3281_892fbe80d81ebe8a3c82b5f7218dd3ba.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2009
16
2
A Multiple Slot Cell Scheduling Algorithm for Multicast Switching Systems
W.F.
Wang
F.Ch.
Lee
J.B.
Shih
In this study, we propose a multicast switching system called the Blocking Reduction
Multiple Slot Cell Scheduler (BRMSCS) switch. The BRMSCS switch consists of shared memory banks, a
crossbar fabric and the BRMSCS scheduler. Our goals are to relieve the blocking situation in the scheduler
and to guarantee freedom from a memory access con
ict, that is, no more than two output ports should
access dierent cells that come from the same input port. To meet the goals, the BRMSCS scheduler can
quickly insert address cells into a scheduling table and ll the scheduling table as full as possible. The
simulation results show that the BRMSCS scheduler can eciently insert the address cells into the con
ict
free locations of the scheduling table and has the advantage of reducing blocking.
Multicast
Packet switch
Multicast scheduling algorithm
Switch
2009
12
01
http://scientiairanica.sharif.edu/article_3282_3e243e2a5560a1c478dcf646f2b68bb3.pdf