فهرست مطالب

مهندسی برق و الکترونیک ایران - سال پنجم شماره 2 (زمستان 1387)

مجله مهندسی برق و الکترونیک ایران
سال پنجم شماره 2 (زمستان 1387)

  • تاریخ انتشار: 1387/11/22
  • تعداد عناوین: 7
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  • R. P. Buinevicius, J. G. Webster Page 1
    Pulse oximetry measures the relative concentration of arterial oxygenated hemoglobin and reduced hemoglobin. This paper presents the design of a pulse oximeter, which measures the presence of a third substance, carboxyhemoglobin (HbCO), by unfiltered LEDs at 660 nm, 810 nm, and 940 nm. Background information is given on the theory of pulse oximetry. Theoretical approximations and calculations which are implemented in our instrument are presented. Sensor design and a flowchart, showing the signal processing routine that accomplishes the required analysis is included. The problem of noise occurrence during the signal processing routine is also discussed.
  • M. Moulavi, Kakhki, D. Rejaly Page 8
    In this work the performance of a wavelength division multiple access (WDMA) system with direct detection receiver is investigated. For this purpose, the probability of error in a WDMA network with OOK modulation considering crosstalk, ISI, photo detector noise and thermal noise is calculated and the effect of each on system performance is investigated. The system performance in presence of PIN and APD Photo detectors are compared. Besides the accurate calculations of bit error rate, these calculations have also been performed using Gaussian, Chernoff bound and modified Chernoff bound approximations for the decision variable. Results of our calculations of the photo detector noise penalty in presence PIN and APD photo detectors are presented and compared for different number of channels. Also, from the calculations of the receiver sensitivity, an optimum value for the avalanche gain of APD is obtained. The superiority of APD over PIN photo detection is also demonstrated.
  • A. Khoobroo, B. Fahimi Page 21
    The present paper explores the impact of an on-board hydrogen harvesting system (fuel reformer) on the overall efficiency of a fuel-cell powered vehicle. Various methods of hydrogen production for automotive applications have been discussed first. As the hydrogen production is one of the major challenges for application of proton exchange membrane (PEM) fuel cells, especially in vehicular industry, this paper aims to provide an overview on different methods of cold plasma generation and plasmatrons which can be used to improve hydrogen production problem. Experimental results from a laboratory prototype have been included as a point of reference.
  • A. Ketabi, M. Khoshkholgh Page 31
    In this paper power system model is represented in a new domain that relates to Multi-Resolution Analysis (MRA) space. By developing mathematical model of elements in this space using Galerkin method, a new alternative method for power system simulation in nonsinusoidal and periodic conditions is developed. The mathematical formulation and characteristics of new proposed space is expressed. Also the relation between this domain and spectral analysis is presented. Transmission line and switching devices modeling in the proposed domain is investigated. To consider frequency dependency of line parameters and to obtain harmonics information, the relationship between this dependency and the new suggested domain is discussed. Then the new algorithm is presented and demonstrated for two case studies.
  • M. A. Golkar, S. Hosseinzadeh, A. Hajizadeh Page 41
    This paper presents a multi-objective formulation for optimal siting and sizing of distributed generation (DG) resources in distribution systems in order to minimize the cost of power losses and energy not supplied. The implemented technique is based on a genetic algorithm (GA) and weight method that employed to obtain the best compromise between these costs. Simulation results on 33-bus distribution test system are presented to demonstrate the effectiveness of the proposed procedure.
  • A. Abadpour, S. Kasaei Page 49
    Since the birth of multi–spectral imaging techniques, there has been a tendency to consider and process this new type of data as a set of parallel gray–scale images, instead of an ensemble of an n–D realization. Although, even now, some researchers make the same assumption, it is proved that using vector geometries leads to better results. In this paper, first a method is proposed to extract the eigenimages from a color image. Then, using the energy compaction of the proposed method, a new color image compression method is proposed and analyzed. The proposed compression method, which uses vector–based operations, applies a grayscale compression algorithm on the eigenimages. Experimental results show that, at the same bandwidth, the proposed method produce 3.6dB and 1.9dB enhancement in the quality, compared to JPEG and JPEG2000, respectively.
  • M. H. Yaghmaee, G. Khojasteh Toussi, M. Bahekmat Page 58
    Quality of Service (QoS) refers to a set of rules or techniques that help the network administrators use the available network resources optimally to manage the effects of congestion and to treat the applications according to their needs. The differentiated services architecture (DiffServ) allows providing quality of service to users. The major DiffServ premise is that individual flows with similar QoS requirements can be aggregated in larger traffic sets and identified as classes. Relative service differentiation is a simple and easily deployed approach compared to the absolute differentiation service. In this paper, we use fuzzy logic systems to design a novel algorithm for queue management and scheduling of classified packets in the differentiated service IP networks. The proposed model consists of two parts. The first part of the proposed model is used for absolute differentiated services and tries to optimize QoS parameters and to share sources between different requests fairly. The second part of the proposed fuzzy system is dedicated to relative Diffserv model. As one of the famous existing algorithms for both buffer management and scheduling in the relative differentiated service is Jobs algorithm, in the second parts of the proposed system, we modify the traditional Jobs algorithm and proposed a fuzzy based modification of existing Jobs algorithm. The proposed algorithm uses different fuzzy logic controllers to differentiate the delay of traffic classes. Simulation results confirm that the proposed fuzzy system, can provide better delay differentiated than the traditional algorithms.