Al-Khalid Othman - Academia.edu (original) (raw)

Papers by Al-Khalid Othman

Asia-Pacific Symposium on Information and Telecommunication Technologies, Jun 15, 2010

Abstract Optical couplers are important device in optical communication networks to perform coupl... more Abstract Optical couplers are important device in optical communication networks to perform coupling functionalities. Gathering several signals in one optical communication network is not the significant problem now due to the emergence of various inventions of optical ...

The widespread adoption of Renewable Energy Resources (RER) and Plug-in Electric Vehicles (PEVs) ... more The widespread adoption of Renewable Energy Resources (RER) and Plug-in Electric Vehicles (PEVs) in distribution systems has achieved a substantial energy share, allowing the microgrid to participate in the open market. In fact, the high penetrations of RER and PEVs have increased the importance of impact assessment involving system protection. A framework is presented in this paper for modeling the combined operations of RER based solar Photovoltaic (PV) systems and PEVs in a microgrid integrated with power grid. The paper also proposes a fault current limiter connected in parallel (anti-islanding protection) with the circuit breaker in the point of common coupling (PCC), thus providing current bypass circuit during abnormal conditions. The concept of the proposed scheme is validated under various operating conditions using a 24-hourly dynamic simulation. The results demonstrate the effectiveness of the proposed approach.

Bulletin of Electrical Engineering and Informatics

In this paper, the proposed single boost converter aims to harness more than one renewable energy... more In this paper, the proposed single boost converter aims to harness more than one renewable energy (RE) input source and achieve a high voltage gain. The interleaved technique combined with voltage multiplier (VM) cells, reduced inductor current and attained high voltage transfer ratio. The boost converter possesses two unidirectional input ports and a bidirectional input port that is connected to a battery storage. The duty ratios of the power and interleaving switches are used to regulate the output voltage of the proposed converter. Three operation modes are identified, and steady state analyses of the converter are presented and discussed. The converter can store excess energy in the battery during periods of abundance and deliver power to the loads when the RE sources are low or unavailable. In addition, the output voltage is higher than that of the conventional boost converter. The converter delivered 278 V from 12 V and 24 V dual input sources. The converter operation is simul...

Journal of Telecommunication, Electronic and Computer Engineering, 2016

IEEE802.15.4 standard for Wireless Sensor Network (WSN) provides low-power transmission in the lo... more IEEE802.15.4 standard for Wireless Sensor Network (WSN) provides low-power transmission in the low-rate wireless personal area network (WPAN). It has three types of topology: star, peer-to-peer and cluster tree. Star topology has limit to expand network. Peer-to-peer topology has a complex multihop routing during network expansion due to the large number of full-function devices. A full-function device can act as coordinator and personal area network coordinator (PAN-C). Cluster tree topology is preferable because it can expand networks using less number of full-function devices and thus reduces complexity in routing messages. A cluster tree topology consists of a wireless PAN-C, several cluster coordinators and a number of end devices. The coordinators periodically transmit beacon frames to one another to allow synchronization and communication. However, collision will happen if the coordinators transmit beacon frames at the same time and will degrade the network performance. Diffe...

Journal of Telecommunication, Electronic and Computer Engineering, 2017

Sarawak is the largest state in Malaysia, in spite of this, the population of Sarawak is relative... more Sarawak is the largest state in Malaysia, in spite of this, the population of Sarawak is relatively small and 42 percent of that population residing in the rural areas. Consequently, the Sarawak government is facing immense challenges in providing basic need such as electricity to the entire state due to the remoteness and small sizes of these settlements. Although the state produces sufficient amount of power, the cost of connecting these rural and non-rural small settlements to the grid is just impractical. The current energy scenario in Sarawak will be reviewed with a focus on the two reliable renewable energy resources currently being pursued by the Local Electrical Authority (LEA) for rural electrification projects which are the Hydro Power and Solar Energy. The paper will address the technical and localized challenges facing the micro-hydro and solar electric energy generation in Sarawak. The micro hydropower potential in Sarawak is estimated at 10.2MW but is not being fully d...

ArXiv, 2017

Wireless communication technology has seen a remarkably fast evolution due to its capability to p... more Wireless communication technology has seen a remarkably fast evolution due to its capability to provide a quality, reliable and high-speed data transmission amongst the users. However, transmission of information in wireless channels is primarily impaired by deleterious multipath fading, which affects the quality and reliability of the system. In order to overcome the detrimental effects of fading, Multiple-Input Multiple-Output (MIMO) technology is an attractive scheme that employs multiple transceiver antennas to carry the data over the same frequency band over a variety of signal paths. This technology has shown great solutions due to its ability to provide better spectral efficiency, capacity, throughput and robustness of the data transmission. But in practice, it is impractical to install multiple antennas on small-sized devices. Hence, to overcome the limitations of MIMO gain in the future wireless networks, cooperative diversity has recently draw in attention due to its abili...

2018 IEEE 7th International Conference on Power and Energy (PECon), 2018

Integrating renewable energy resources (RER) into the power grid may jeopardize the whole power s... more Integrating renewable energy resources (RER) into the power grid may jeopardize the whole power system if the penetration level or solar PV uncertainty is not thoroughly managed. The critical impact on the behaviour of power system can be observed during the line outage in a power grid connected with large-scale RER. Therefore, contingency analysis (CA) is crucial to assess such hybrid power grid. This paper proposes a framework based on CA to assess the simultaneous effect of large-scale solar photovoltaic (PV) power plants integrated with the existing power grid, particularly, in the aspects of implementing effective measuring indices. Simulation studies have been carried out on a practical power system, which was modelled by considering the probability of solar irradiance at different locations in Sarawak. The study presented in this paper can provide an insight to identify the level of insecurity for a large-scale deployment of solar PV systems in Sarawak.

International Journal of Recent Technology and Engineering (IJRTE), 2019

This paper describes the design of a 400 V, three-phase voltage source inverter system using Sinu... more This paper describes the design of a 400 V, three-phase voltage source inverter system using Sinusoidal Pulse Width Modulation (SPWM) control technique. Pulse Width Modulation (PWM) is an internal control technique for inverters. The Sinusoidal Pulse Width Modulation (SPWM) technique is the type of PWM used in this work. The aim is to reduce the harmonic produced by the inverter. Current standards require that total harmonic distortion (THD) be minimal. A three-phase SPWM signal is implemented in order to create an output voltage which is closer to a true sine wave and reduce harmonics. The development and model were implemented using MATLAB Simulink soft-ware and hardware parameters. The addition of a low pass filter circuit aids the achievement of smoother sine waveforms and a reduced THD value of 0.17%. The proposed concept has been validated through experimentally on a laboratory prototype by using DSP TMS320F28335 real-time digital control. The experimental outcomes emphasize t...

The International Conference on Electrical Engineering, 2008

This paper presents the results of measured TCP performance in the LA process during the deployme... more This paper presents the results of measured TCP performance in the LA process during the deployment of GPRS CS1 and CS2 coding schemes and after the activation of two more coding schemes, CS3 and CS4. The measurements are carried out in one of the commercially deployed live GPRS networks in Malaysia, using end-to-end FTP file transfer application for the assessment. Tracing at the GPRS air interface is done simultaneously. The results show that TCP works well in the LA process and can adapt to the frequent switching between the coding schemes without any problem. The average throughput is increased by 23% for urban areas owing to the activation of higher coding schemes and aided by TCP tuning. It is also shown that throughput is limited by the current coding scheme used and good channel condition is necessary to optimize TCP performance.

Indonesian Journal of Electrical Engineering and Computer Science, 2018

This paper describes the design of an artificial neural network (ANN) control with power sharing ... more This paper describes the design of an artificial neural network (ANN) control with power sharing control abilities of a new proposed double-input boost power converter (DIBC). The goal of this research is to model and design a high effectiveness and great performance double-input power converter for renewable energy applications. First, an artificial neural network controller design which is flexible versus a variable input voltage resource and variable load (to achieve the line regulation test and load regulation test) is proposed. Lastly, the suggested concept has been validated through experimentally on the laboratory prototype by using DSP TMS320F28335 real-time digital control. The experimental outcomes emphasize the authenticity of the suggested topology, which can be promising a novel topology that includes double-input power converter appropriate for renewable energy application systems.

Proceedings of 2nd International Conference on Information Technology and Electronic Commerce, 2014

The 'Beyond 3G Wireless Networks Architecture' proposes to assimilate numerous heterogeneous wire... more The 'Beyond 3G Wireless Networks Architecture' proposes to assimilate numerous heterogeneous wireless network technologies over an Internet Protocol Backbone. However, in order to offer seamless mobility, cost-effective connectivity and desired Quality of Service (QoS) in such a diverse environment; efficacious vertical handover support still remains a major design challenge. In this research/manuscript, a novel handover decision mechanism, 'Travelling Time Prediction Based on the Consecutive RSS Measurements' in an IEEE 802.11 WLAN cell is suggested. The method uses a time threshold which is computed by a Mobile Terminal (MT) as soon as it penetrates into a WLAN boundary. The estimated travelling time is then compared with the time threshold, so as to make handover decisions for minimizing the probability of unnecessary handovers. Our performance analysis reveals that the suggested mechanism effectively reduces number of unnecessary handovers by 60% as compared to the already proposed schemes.

Proceedings of the International Engineering Conference, 2014

Most of the countries are developing their own energy depending on their natural resources and en... more Most of the countries are developing their own energy depending on their natural resources and energy consumption by their industrial production, transportation and population. Globally, reduction of gas emission and replacement of fusel fuel by green energy is the target of the world in order to avoid the global warming and the increase of CO2 emission and the decrease of oil storage. Consequently, the international solar energy society ISES had established to collect all researches in solar technology and to advise many countries to implement an optimal solar projects. A part of this society, The Asia Pacific Solar Society and Hybrid Technology APSSAHT has been recently established to consider all parts of hybrid energy technology, not only solar, and to advise the Asia pacific region on implementing a hybrid energy projects. This talk will present the objectives of this society and the target of the renewable energy in the year 2020, and briefly introduce the hybrid technology, microgrid, natural resources and fuels used.

International Journal of Communication Networks and Information Security (IJCNIS)

Decoding high complexity is a major issue to design a decode and forward (DF) relay protocol. Thu... more Decoding high complexity is a major issue to design a decode and forward (DF) relay protocol. Thus, the establishment of low complexity decoding system would beneficial to assist decode and forward relay protocol. This paper reviews existing methods for the min-sum based LDPC decoding system as the low complexity decoding system. Reference lists of chosen articles were further reviewed for associated publications. This paper introduces comprehensive system model representing and describing the methods developed for LDPC based for DF relay protocol. It is consists of a number of components: (1) encoder and modulation at the source node, (2) demodulation, decoding, encoding and modulation at relay node, and (3) demodulation and decoding at the destination node. This paper also proposes a new taxonomy for min-sum based LDPC decoding techniques, highlights some of the most important components such as data used, result performances and profiles the Variable and Check Node (VCN) operatio...

Visual attention allows user to select the most relevant information to ongoing behaviour. This p... more Visual attention allows user to select the most relevant information to ongoing behaviour. This paper presents a study on; i) the performance of people measurements, ii) accurateness of people measurement of the peaks that correspond to chemical quantities from the Magnetic Resonance Spectroscopy (MRS) graphs and iii) affects of people measurements to the algorithm-based diagnosis. Participant-s eye-movement was recorded using eye-tracker tool (Eyelink II). This experiment involves three participants for examining 20 MRS graphs to estimate the peaks of chemical quantities which indicate the abnormalities associated with Cerebellar Tumours (CT). The status of each MRS is verified by using decision algorithm. Analysis involves determination of humans-s eye movement pattern in measuring the peak of spectrograms, scan path and determining the relationship of distributions of fixation durations with the accuracy of measurement. In particular, the eye-tracking data revealed which aspects ...

This study considers the resource allocation problem in relay networks for downlink transmission ... more This study considers the resource allocation problem in relay networks for downlink transmission where base station (BS) communicates with multiple mobile stations (MSs) via relay stations (RSs) operating in either half-duplex (HD) or full-duplex (FD) mode. Relay gain factors for Amplify and Forward (AF) protocol are studied and a new one called adaptive AF (AAF) relaying is proposed. The AAF scheme attempts to equalize the signal-to-noise ratio (SNR) across subcarriers, thus providing increased throughputs and proportional fairness in resource distribution. Simulation results of comparative analysis of the AAF relaying scheme and the two basic relaying protocols namely AF and Decode and Forward (DF) are presented in terms of average system throughput, fairness and percentage of call outage under maximum-sum rate (MSR) resource allocation technique. The results show that the AAF scheme achieves superior performances compared to the other ones.

The aim of this paper is to present the simulation modelling process of an end suction centrifuga... more The aim of this paper is to present the simulation modelling process of an end suction centrifugal pump using commercial Computational Fluid Dynamics software. The study pump is a radial flow pump with specific speed of 1075.0 (mm/mm). Three distinct models, called Volute, Impeller and Draft Tube, were generated based on the geometry and dimension of the pump. Unstructured tetrahedral mesh were applied to all flow domains, utilizing the advantage of good meshing capability for complex surface geometries. The governing equations that were used are steady-state three-dimensional Navier-Stokes equations coupled with the k-epsilon turbulence model. It can be observed that the simulation result yield comparable performance when compared with the manufacturer data sheet. Pressure distribution, velocity vector and velocity streamline visualization show local losses inside the pump. It is believed that the finding from this study complement the ongoing research relevant to turbomachinery mo...