Department of Electrical Engineering

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https://escholar.umt.edu.pk/handle/123456789/1175

The mission of the electrical engineering program is to prepare its graduates for successful professional engineering careers by providing electrical engineering capabilities necessary to engage in service, research and development that serve the needs of their homeland Pakistan as well as the other parts of the globe.

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Method for transmission of voice over wireless packet-switched networks
(2006) Foster, Gerry; Hobbis, Kevan; Sesmun, Amardiya; Sajjad Shami
A method for the determination of the optical constants ( n and k ) of thin films with large optical inhomogeneities
(Journal of Modern Optics, 2007) E. E. Khawaja; M. F AL-Kuhaili .; S. M. A. Durrani
The existing methods for determining the optical constants of inhomogeneous thin films deal with non-absorbing films or at the most with films that have very small absorption (k < 0:02). In this work, a method is presented for the determination of the optical constants of inhomogeneous thin films with large optical inhomogeneities. The optical constants are derived from normal-incidence measurements of reflectance and transmittance. The refractive index was modelled by quadratic variation. However, the absorption index was replaced by its mean value. The accuracy of this assumption was tested and its range of validity was determined. Subsequently, the method was applied to the determination of the optical constants of cerium oxide thin films.
Reduced order multiport parallel and multidirectional neural associative memories
(Biological Cybernetics, 2009) Abdul Aziz Bhatti
This paper proposes multiport parallel and multidirectional intraconnected associative memories of outer product type with reduced interconnections. Some new reduced order memory architectures such as k-directional and k-port parallel memories are suggested. These architectures are, also, very suitable for implementation of spatiotemporal sequences and multiassociative memories. It is shown that in the proposed memory architectures, a substational reduction in interconnections is achieved if the actual length of original N-bit long vectors is subdivided into k sublengths. Using these sublengths, submemory matrices, Ts or Ws , are computed, which are then intraconnected to form k-port parallel or k-directional memories. The subdivisions of N-bit long vectors into k sublengths save (k−1)×100 k % of interconnections. It is shown, by means of an example, that more than 80% reduction in interconnections is achieved. Minimum limit in bits on k as well as maximum limit on subdivisions in k is determined. The topologies of reduced interconnectivity developed in this paper are symmetric in structure and can be used to scale up to larger systems. The underlying principal of construction, storage and retrieval processes of such associative memories has been analyzed. The effect of complexity of different levels of reduced interconnectivity on the quality of retrieval, signal to noise ratio, and storage capacity has been investigated. The model possesses analogies to biological neural structures and digital parallel port memories commonly used in parallel and multiprocessing systems.
Efficient medium access control protocols for broadband wireless communications
(Intech Open Science, 2011) Suvit Nakpeerayuth; Pisit Vanichchanunt; Warakorn Srichavengsup; Muhammad Saadi
In wireless communication systems, an efficient medium access control (MAC) protocol is usually required so that multiple wireless stations can efficiently share the scarcely-limited wireless channel. In a typical wireless environment, wireless stations are usually geographically distributed over a service area and are not synchronized. As a consequence, wireless stations are typically required to contend for transmission opportunities. In general, if the MAC protocol is not properly designed, channel contention may cause serious transmission collisions and can considerably degrade the system throughput performance. Over the past several decades, numerous MAC protocols have been developed to smartly utilize the wireless channel, e.g., ALOHA (Abramson, 1970), carrier-sense multiple access (CSMA) (Kleinrock & Tobagi, 1975; Tobagi & Hunt, 1980), and many other variants (Tasaka & Ishibashi, 1984; Karn, 1990; Frigon, et al., 2001; Amitay & Greenstein, 1994). These conventional MAC protocols have been successfully deployed in practice for different applications and environments, including the widely adopted IEEE 802.11 a/b/g/n wireless local area network systems, the emerging IEEE 802.16 (WiMAX) wireless metropolitan area network, the IEEE 802.15.4 (Zigbee) wireless sensor networks, and various famous MAC protocols for satellite communication networks. In addition, the emerging multimedia technologies in recent years have continuously driven the requirements for higher and higher system transmission throughput. In such an environment, the round trip propagation delays between the base station and wireless stations have increasingly become relatively larger and larger compared with a packet transmission time. As a consequence, a fair deal of recent research work has been directed toward the renewed studies of efficient MAC schemes for systems with relatively large propagation delays. This chapter overviews the existing MAC technologies and summarizes recent research advancements toward the improvements and analysis of various MAC protocols. In particular, a class of efficient modified random channel contention and reservation schemes based on our proposed work (Sivamok, et al, 2001; Srichavengsup, et al, 2005) is presented with a complete discussion of mathematical performance evaluation and numerical results.
Tec mapping for the determination of seismo-ionospheric anomaly behavior
((ICEES 2011), NUST, Islamabad, Pakistan, 2011) Muhammad Saadi; Rabeel Manzoor; Wuttisittikulkij, Lunchakorn
Outlier and event detection in harsh environments: an application of wireless sensor networks
(LAMBERT Academic Publishing (LAP), 2012) Nauman Shahid
Impact of wind farms on birds: a review
(2012) Mehwish Mujahid; Ayesha Mohy-Ud-Din
Islam is recognized as a broad approach of life whose teachings cover every likely human relationship including that with the environment. We, human beings, are permitted to employ the earth's resources land, water, air, minerals, flora, fauna, feathered creatures to accommodate our needs, but only in an approach that does not disturb ecological equilibrium and that does not discredit the ability of future generations to meet their needs. Wind farming is a mean of obtaining electric energy that does not produce air toxic wastes, effluence, greenhouse gasses, smog, fumes, litter, trash or other forms of environmental squalor associated with fossil fuel technologies. For a wind farm model, birds may be injured by direct impact with turbine blades, towers and/or transmission lines. This review explains the impact of wind farms on birds with an assessment of the probable bird species/groups that may fabricate problems by wind farm occurrences. It describes a couple of means by which wind farms can possibly have cogent effects on birds. Firstly they can pose a risk of collision, with birds soaring into rotor blades, resulting in increased mortality rates. Secondly they can cause loss of habitat, mainly through movement of birds from an area around the wind turbines. The degree and austerity of all impacts could best be lessened by the careful laying of proposed wind farms and by preparing a site management plan and design through numerous active strategies as explained in the paper
Model based analysis and efficient control system design for fuel cell power system
(2012) Mashood Nasir; Abdul Aziz Bhatti; Waqas Tariq Toor
In this research work a Fuel cell based power system is explicitly modeled and analyzed under the various possible operating conditions. In order to ensure a reliable, efficient, durable and cost effective operation, a control system based on the management of air and fuel flow regulations can be designed. Fuel cell systems produce clean energy and they have got higher energy conversion efficiencies as compared to Internal Combustion Engines based power plants. In order to make this technology economically viable, feed of the air and fuel, pressure regulations, flow rates and the heat produced must be optimally controlled. Oxygen depletion, during the transient reactions, is the major cause of low performance and subsequent deteriorations. In order to overcome the stated limitations, internal subsystem reactions are modeled deliberately and examined carefully. Based on the mathematical deductions and feedback control techniques, optimal pressures and flow rates for hydrogen and oxygen are selected. Breath control unit can be efficiently controlled by using this model to avoid degradation. The output voltage model is also delineated in terms of internal electrochemical dynamics to confirm the maximum power gain by the selected parameters. Results are also verified using MATLAB/ Simulink tool. The Proposed methodology is equally valid for both Polymer Electrolyte Membrane and Solid Oxide Fuel Cells based power systems with some modifications.
Neural network based optimal placement of base stations in three dimensional plane
(IEEE, 2012) Waqas Tariq Toor; Abdul Aziz Bhatti
The paper proposes a solution to the problem of optimal placement of base stations, with effective utilization of resources. First, it analyzes the placement of base stations in x-y plane. Then this analysis is extended to 3-dimenional system, by including the z coordinate for representing height. This analysis optimizing these xy coordinate values as well as value of z coordinate, as height also contributes in covering the area of base stations. The Hopfield neural network model is used to find the solution to our problem.. Neural network and all parameters, i.e. x, y and z coordinates are used to maximize the coverage area and to minimize the interference, as optimal placement of base stations refer to these two points. In wireless communication system, the placement of base stations requires work force and costly equipments like GPS etc. resulting in loss of time and money. However, with proposed strategy only a laptop or desktop PC will be required to compute the positions of base stations within very less time. The energy equations are developed for our network which shows that the solution resulting from these equations is stable. The computer simulations and graphs are also included to validate the results.
Critical analysis of hopfield's neural network model for tsp and its comparison with heuristic algorithm for shortest path computation
(IEEE, 2012) Farah Sarwar; Abdul Aziz Bhatti
For shortest path computation, Travelling-Salesman problem is NP-complete and is among the intensively studied optimization problems. Hopfield and Tank's proposed neural network based approach, for solving TSP, is discussed. Since original Hopfield's model suffers from some limitations as the number of cities increase, some modifications are discussed for better performance. With the increase in the number of cities, the best solutions provided by original Hopfield's neural network were considered to be far away from those provided by Lin and Kernighan using Heuristic algorithm. Results of both approaches are compared for different number of cities and are analyzed properly
Frequency synchronization algorithms for 802.11n based mimo-ofdm systems: a performance analysis
(IEEE, 2012) Awais Riaz; Nauman Shahid; Ahmad Usman; Farhan Bin Khalid
Orthogonal Frequency Division Multiplexing (OFDM) is a bandwidth efficient signaling scheme for digital communications that was first proposed by Chang. In OFDM, the spectrum of individual orthogonal subcarriers mutually overlaps, giving therefore an optimum spectrum efficiency. A data communications system based on OFDM is particularly sensitive to frequency offset in the channel. Frequency offset is a phenomena, which causes phase shift and hence, reduction in signal strength at the output of the filters matched to each of the carriers and introduces ICI from other carriers which are now no longer orthogonal to the filter. In OFDM the carriers are inherently closely spaced in frequency compared to the channel bandwidth, the tolerable frequency offset becomes a very small fraction of the channel bandwidth. This paper is based on the study and comparison of algorithms that estimate the carrier and sampling frequency offsets from the demodulated data signals in the receiver. An implementation of these techniques to correct the respective offsets along with the performance of these algorithms, via simulation, is also presented.
Comparative analysis of fuel cells and suggestions to improve their efficiencies for sustainable future
(2012) Manzar Ahmed; Mashood Nasir
In this paper an analytical comparison is presented between the various developed configuration of fuel cells under the different operating conditions of temperature and load variations with respect to their efficiency and output power. The fuel cells such as Polymer Electrolyte Membrane, Solid oxide, Molten Carbonate and Alkaline fuel cells have very high conversion efficiency and they can be used for distribution generation and electric utility. However performance and degrading issues are always of concern for researchers. Carbon black is one of the major causes of performance degradation of fuel cells. Carbon Nanotubes having the carbon support materials with a higher graphitic character are used to improve the efficiency and stability of these fuel cells. Further, the potential of alternate energy resources would be compared based on several important parameters such as efficiency, economics, ease of construction and other important parameters. Attempts would also be made to make a technical and economic comparison of these types of cells and evaluate their merits and de-merits. Although, out of all of these cells under consideration the solid oxide carries a risk of high temperature corrosion and breakdown of components, improvements are being worked out. Finally all results obtained from different cells will be simulated by using Matlab Simulation Tools.
A microcomputer-based methodology for distance protection on long uhv transmission lines using symmetrical components
(2012) Abdul Aziz Bhatti; Mashood Nasir
This paper proposes a methodology for the long UHV transmission lines distance protection using microprocessor for fault detection, isolation and auto reclosing processes. In the present era, with the development of microprocessor technology, their extra efficient controlling and computing abilities can be utilized in distance relaying for efficient computing of fault distance and the type of fault occurred on the transmission line. Using Symmetrical component theory a single performance equation is developed that will encounter all type of faults on transmission lines regardless of the nature of the fault. Microprocessor will process on these sequence components to estimate the type of fault and the distance of fault from the relay. ETAP is used as a simulation tool to obtain the desired results. Although the formulation described here is independent of hardware yet it provides a complete analytical base for distance protection and is analyzed for different types of fault conditions using simulation tools.
Formulation of an electric equivalent circuit of pemfc and its behavioral studies under steady state and transient conditions
(2012) Asfa Javed; Abdul Aziz Bhatti; Mashood Nasir
In this paper electric equivalence model is formulated for the constructional and operational features of a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The proposed model is capable of explaining the behavior of PEMFC in both steady state and transient modes of operation.. For the efficient designing of fuel cell related applications it is highly desirable to model the electrical output of fuel cell in terms of its internal electrochemical dynamics. The proposed model includes the phenomenon like activation polarization, ohmic polarization and mass transport effect. An analogical electrical circuit is formulated by taking these phenomena into considerations. Within acceptable limits, the effects of load variation on output voltage, efficiency and fuel flow demands are also investigated. The static and dynamic characteristics obtained through simulations are compared with the standard available data. Simulation results show that the model can be used in PEM fuel cell distributed generation related control studies.
Critical analysis of hopfield's neural network model and heuristic algorithm for shortest path computation for routing in computer networks
(IEEE, 2012) Farah Sarwar; Abdul Aziz Bhatti
Shortest path routing and its computation is a crucial point in computer networks, and has significant impact on overall network's performance. Being an issue of salient importance, many algorithms were proposed for shortest path computation and are still under research for more enhancements. Hopfield proposed a neural network based architecture for such optimization problems. Mehmet and Park Keum suggested improved energy functions for this neural network to implement it for routing in computer networks. A * search algorithm is a heuristic based approach, with the properties of Dijikstra algorithm and is used for same purpose. Performances of both approaches are compared and results are analyzed.
Dynamic modeling and characterization of a proton exchange membrane fuel cell
(2012) Muhammad Salik; Abdul Aziz Bhatti; Mashood Nasir
This paper presents the equivalent dynamic model accounting for the thermodynamic and electrochemical characteristics of Proton Exchange Membrane Fuel Cell (PEMFC). The proposed model was implemented in MATLAB/SIMULINK environment. The effects of temperature variations, fluid flow changes and capacitance due to double layer charging were incorporated in this model. The proposed model responses are in good correspondence with the published experimental results. It also predicts the temperature and pressure response of the PEMFC. The model formulated here would be helpful for the optimal prediction of characteristics and dynamic operation of a fuel cell stack.
Neural networks based physical cell identity: assignment for self organized 3gpp long term evolution
(IEEE, 2012) Muhammad Basit Shahab; Abdul Aziz Bhatti
This paper proposes neural networks based graph coloring technique to assign Physical Cell Identities throughout the self organized 3GPP Long Term Evolution Networks. PCIs are allocated such that no two cells in the vicinity of each other or with a common neighbor get the same identity. Efficiency of proposed methodology resides in the fact that minimum number of identities is utilized in the network wise assignment. Simulations are performed on a very large scale network, where initially all the cells are without any PCIs assigned. Results of simulations are demonstrated to analyze the performance of the proposed technique
Microcontroller based implementation of fuel cell and battery integrated hybrid power source
(2012) Fahad Ali; Syed Mohsin Ali; Abdul Aziz Bhatti; Mashood Nasir
This paper presents the implementation of a digitally controlled hybrid power source system, composed of fuel cell and battery. Use of individual fuel cell stacks as a power source, encounters many problems in achieving the desired load characteristics. A battery integrated, digitally controlled hybrid system is proposed for high pulse requirements. The proposed hybrid power source fulfils these peak demands with efficient flow of energy as compared to individual operations of fuel cell or battery system. A dc/dc converter is applied which provides an optimal control of power flow among fuel cell, battery and load. The proposed system efficiently overcomes the electrochemical constraints like over current, battery leakage current, and over and under voltage dips. By formulation of an intelligent algorithm and incorporating a digital technology (AVR Microcontroller), an efficient control is achieved over fuel cell current limit, battery charge, voltage and current. The hybrid power source is tested and analyzed by carrying out simulations using MATLAB simulink. Along with the attainment of desired complex load profiles, the proposed design can also be used for power enhancement and optimization for different capacities.
Transformer less design of polymer exchange membrane fuel cell based uninterruptable power supply
(University of Management and Technology, 2013) Mohsin Ali
This research work presents a transformer less model of fuel cell powered uninterruptable power supply (UPS). The design consideration of this research includes the utilization of Polymer Exchange Membrane Fuel Cell ( PEMFC) market available stack model and designing of an efficient, low loss, cheap and high power design of a transformer less inverter model for 6kW UPS. This model is controlled with the help of embedded controller which ensures ripple and glitch free voltage regulated inverter providing pure sine wave as an output. This efficient inverter uses high frequency ferrite core transformer which would have a very small size and high efficiency. This model also ensures a very low total harmonic distortion. The proposed model utilizes a super capacitor module to overcome the electric transient conditions for the instantaneous power fluctuation, slow dynamics of the fuel cell and idealizing the overload response. Finally with synchronization techniques this UPS is connected to AC supply mains, also the calculations of fuel required for one hour continuous operation of 6kW UPS is formulated. The model proposed in this research work is implemented in MATLAB – SIMULINK environment.
A survey of different speech synthesis techniques
(TAEECE, 2013) Madiha Jalil; Faran Awais Butt; Ahmed Malik
The Objective of this paper is to present comprehensive overview of format and concatenative speech synthesis techniques. Initially, format synthesis is explored and then concatenative synthesis. Using softwares, speech synthesis is performed by both methods and then their results are compared. The pros and cons of both these methods are discussed as well.

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