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Transaction on Civil Engineering
 
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Transaction on Mechanical Engineering
 
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Volume 16, Issue 2, 2009
Transaction on Computer Science & Engineering and Electrical Engineering


On-Chip Interconnection Network with an Ecient Parallel Bu er Structure and Generic Trac Model
 
        N. Bagherzadeh (PhD.)
  • J.H. Bahn [PhD.]

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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 bu er architecture and its management scheme are introduced. By adopting an adjustable architecture that integrates a parallel bu er 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 bu er 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.

Keywords:
Network-on-Chip

    Virtual channel
      Parallel bu er
        Router
          Generic trac mode.


An Efficient Content-Based Video Coding Method for Distance Learning Applications
 
        S. Kasaei (PhD.)
  • T. Lotfi [PhD.]
  • M. Bagheri [PhD.]
  • A. A. Darabi [PhD.]

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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.

Keywords:
Content-based video coding

    Distance learning
      Motion segmentation
        Mosaicing.


Optimal Size and Location of Distributed Generations for Minimizing Power Losses in a Primary Distribution Network
 
        B. Kermanshahi (Professor)
  • R.M. Kamel [PhD.]

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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 bene ts. 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 di erent 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.

Keywords:
Distributed generation

    Optimal location
      Optimal size
        Loss minimization.


Theory of Optimal Mixing in Directly Modulated Laser Diodes
 
        S. Khorasani (PhD.)
  • B. Cabon [Professor]

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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.

    Keywords:
    Laser diode
      Mixing
        Microwave photonics.


Harmonic Content and Relaxation Resonant Frequency of a Modulated Laser Diode
 
        S. Khorasani (PhD.)
  • H. Zandi [MSc.]
  • M. Bavafaa [MSc.]
  • M. Chamanzar [MSc.]

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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.

    Keywords:
    Laser diode
      Optical modulation
        Relaxation resonant frequency
          Total harmonic distortion.


Convergence Analysis of Spline Solution of Certain Two-Point Boundary Value Problems
 
        J. Rashidinia (PhD.)
  • R. Jalilian [PhD.]
  • R. Mohammadi [PhD.]

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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 speci c 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 di erent choices of step size, we conclude that our presented methods produce accurate results in comparison with those obtained by existing methods.

Keywords:
Two-point boundary value problem

    Non-polynomial Quintic spline
      Convergence analysis.


Estimation of Hottest Spot Temperature in Power Transformer Windings with NDOF and DOF Cooling
 
        M. A. Taghikhani (PhD.)
  • A. Gholami [PhD.]

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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.

Keywords:
Power transformer

    Temperature distribution
      Hot spot
        Forced cooling
          Heat equation
            Finite element.


A Multiple Slot Cell Scheduling Algorithm for Multicast Switching Systems
 
        W.F. Wang (PhD.)
  • F.Ch. Lee [PhD.]
  • J.B. Shih [PhD.]

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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 di erent 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.

Keywords:
Multicast

    Packet switch
      Multicast scheduling algorithm
        Switch.