IIUM Engineering Journal
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TORSIONAL DEFORMATION AND FATIGUE BEHAVIOUR OF 6061 ALUMINIUM ALLOY
Get PDFTorsional deformation and fatigue behaviour of both solid and thin-walled tubular specimens were made from as-received and heat treated 6061 aluminium alloy were studied. 6061 aluminium alloy have been widely used as a candidate material in automobile, aerospace, aircraft and structural application because of their superior mechanical properties such as high strength to weight ratio, good ductility and others. The differences in cyclic deformation and fatigue behaviours between round and solid specimens where a stress gradient exist, and thin-walled tubular specimens where a uniform stress state is commonly assumed, are also discussed. Von Mises and Tresca criteria has been used to predict the monotonic and cyclic deformation curve and compared to the torsional data obtained from the experiment. The S-N curve was used to present and evaluate the fatigue life of the specimens. Through fractographic analysis, failure criteria of fracture surfaces were observed and discussed. 
Modification of ITU-R Rain Fade Slope Prediction Model Based on Satellite Data Measured at High Elevation Angle
Get PDFRain fade slope is one of fade dynamics behaviour used by system engineers to design fade mitigation techniques (FMT) for space-earth microwave links. Recent measurements found that fade slope prediction model proposed by ITU-R is unable to predict fade slope distribution accurately in tropical regions. Rain fade measurement was conducted in Kuala Lumpur (3.3° N, 101.7° E) where located in heavy rain zone by receiving signal at 10.982 GHz (Ku-band) from MEASAT3 (91.5° E) on 77.4° elevation angle. The measurement has been carried out for one year period. Fade slope S parameter on ITU-R prediction model has been investigated. New parameter is proposed for the fade slope prediction modeling based on measured data at high elevation angle, Ku-band. ABSTRAK: Cerun hujan pudar adalah salah satu dinamik tingkah laku pudar yang digunakan oleh jurutera sistem untuk mereka bentuk teknik-teknik pengurangan pudar (FMT) bagi link gelombang mikro ruang bumi. Ukuran baru-baru ini mendapati bahawa cerun pudar ramalan model yang dicadangkan oleh ITU-R tidak mampu untuk meramalkan pengagihan cerun pudar tepat di kawasan tropika. Pengukuran hujan pudar telah dijalankan di Kuala Lumpur (3.3° N, 101.7° E) yang terletak di kawasan hujan lebat dengan menerima isyarat pada 10,982 GHz (Ku-band) dari MEASAT3 (91.5° E) pada sudut ketinggian 77.4°. Pengukuran telah dijalankan untuk tempoh satu tahun. Parameter cerun pudar S pada model ramalan ITU-R telah disiasat. Parameter baru adalah dicadangkan untuk pemodelan cerun pudar ramalan berdasarkan data yang diukur pada sudut paras ketinggian, Ku-band.KEYWORDS: fade slope; ITU-R; fade mitigation techniques; sampling time interva
Controller Design Of Unicycle Mobile Robot
Get PDFABSTRACT: The ability of unicycle mobile robot to stand and move around using one wheel has attracted a lot of researchers to conduct studies about the system, particularly in the design of the system mechanisms and the control strategies. This paper reports the investigation done on the design of the controller of the unicycle mobile robot system to maintain its stability in both longitudinal and lateral directions. The controller proposed is a Linear Quadratic Controller (LQR) type which is based on the linearized model of the system. A thorough simulation studies have been carried out to find out the performance of the LQR controller. The best controller gain, K acquired through the simulation is selected to be implemented and tested in the experimental hardware. Finally, the results obtained from the experimental study are compared to the simulation results to study the controller efficacy. The analysis reveals that the proposed controller design is able to stabilize the unicycle mobile robot.ABSTRAK: Kemampuan robot satu roda untuk berdiri dan bergerak di sekitar telah menarik minat ramai penyelidik untuk mengkaji sistem robot terutamanya didalam bidang rangka mekanikal dan strategi kawalan robot. Kertas kajian ini melaporkan hasil penyelidikan ke atas strategi kawalan robot bagi memastikan sistem robot satu roda dapat distabilkan dari arah sisi dan hadapan. Strategi kawalan yang dicadang, menggunakan teknik kawalan kuadratik sejajar (Linear Quadratic Control) yang berdasarkan model robot yang telah dipermudahkan. Kajian simulasi secara terperinci telah dijalankan bagi mengkaji prestasi strategi kawalan yang dicadangkan. Dari kajian simulasi sistem robot, pemilihan faktor konstan, K yang sesuai di dalam strategi kawalan telah dibuat, agar dapat dilaksanakan ke atas sistem robot yang dibangunkan. Keputusan dari kajian simulasi dan tindak balas oleh sistem robot yang dibangunkan akhirnya dibandingkan bagi melihat kesesuaian faktor kostan, K yang dipilih. Analisa menunjukkan dengan menggunakan strategi kawalan yang dicadangkan dapat menstabilkan robot satu roda.KEYWORDS: unicycle mobile robot; nonholonomic system; LQ
Book Review: Materials Science aAnd Engineering: An Introduction by William D. Callister
Get PDFFor a number of decades, Materials Science and Engineering an Introduction, has been an essential and trusted source of literature, as an introduction to Materials Science and Engineering. Now revised and updated the sixth edition is now available
Influence of Temperature and Pressure on Dispersion Properties of Nonlinear Single Mode Optical Fibers
Get PDFNear field distribution, propagation constant and dispersion characteristics of nonlinear single-mode optical fibers have been investigated. Shooting-method technique is used and implemented into a computer code for both profiles of step-index and graded-index fibers. An error function is defined to estimate the discrepancy between the expected electric-field radial derivative at the core-cladding interface and that obtained by numerically integrating the wave equation through the use of Runge-Kutta method. All of the above calculations done under the ocean depth in which the depth will affect the refractive index that have a direct effect on all the optical fiber parameters.KeyWords: Nonlinear refractive index, Normalized propagation constant, Mode delay factor, Material dispersion, Waveguide dispersion
Comparison: Simulation and Experimental Characterisation of an all-Optical Gain-Clamped Erbium-Doped Fibre Amplifier
Get PDFThis paper presents the GC-EDFA characteristics comparison between the simulated results (using EDFA_Design software) and experimental results. The comparisons reveal the usefulness of the software in simulating the behaviour of an all-optical GC-EDFA system. Comparisons are made for values obtained from the system operated at high laser power, in order to highlight the differences between the experimental and simulated values. The main objective for this comparison is to prove the capability of the software in simulating the gain-clamped system. Therefore, the software can be used to test new configurations, aimed at improvising current gain-clamped EDFA performances.Keywords optical, gain-clamping, erbium, fibre amplifier, simulation, experimen
Conventional Treatment of Surface Water Using Moringa Oleifera Seeds Extract as a Primary Coagulant
Get PDFThe present study involved the use of a model pilot scale water treatment plant to treat turbid surface water from a stream using processed Moringa oleifera seed with 25 % w/w oil extracted as primary coagulant. The water treatment plant was made up of four unit operations: coagulation, flocculation, sedimentation, and filtration (rapid sand filter). Test runs were carried out for three hours per run over a three-month period with turbidities ranging from 18 to 261 NTU. The turbidity, pH, and alkalinity as well as the filter head loss were measured every 30 minutes during the experimental runs. Average turbidity removal of up to 96 % at an effective doses of 20 and 30 mg/l of oil extracted M. oleifera for low (< 50 NTU) and moderate turbidity (< 100 NTU) water respectively was observed doses 50 – 80 mg/l for high turbidity (> 100 NTU) water. M. oleifera seed extract was found to have no significant effect on pH or alkalinity of the water. The residual turbidities measured during most of the test runs satisfied the Malaysian Guideline for Drinking Water Supplies. Key Words: Moringa oleifera, primary coagulant, coagulation, pilot plant, filtration
Erbium Doped Fiber Amplifier Performance using Different Host Materials in the Band 1450-1650 Nm: A Comparative Study
Get PDFA numerical investigation of the performance characteristics of erbium doped fiber amplifier using different host materials is presented. The emission and absorption curves of each of these hosts are fitted to Guassian fitting parameters. A software program is then implemented to calculate the gain coefficient, gain spectrum and the equivalent input noise factors in forward and reverse directions. The hosts under consideration are: almino-germanosilicate, bismuth, LiNbO3, tellurite, sodium niobium phosphate, oxyfluoride silicate, Al2O3 and fluoride phosphate glasses. The corresponding gain covers the 1450-1650 nm wavelength range
Solid State Culture Conditions for Composting Sewage Sludge
Get PDFComposting is applied to treat sewage sludge from treatment plants to enhance its quality and suitability for agricultural use. In this work the optimal conditions for composting sewage sludge from domestic wastewater treatment plants in a horizontal drum bioreactor (HDB) were investigated. This study investigated the physico-chemical conditions affecting the use of filamentous fungi in composting. The average number of faecal coliforms was 2.3 ï‚´ 107 bacteria/g waste dry weight at the beginning of the composting process, and decreased considerably to 8.2 ï‚´ 103, 8.1 ï‚´ 103, 8.5 ï‚´ 103, 8.0 ï‚´ 103,and 8.4 ï‚´ 103 bacteria/g, respectively for experiments T1 to T5. This decrease was presumably the result of raising temperature. The phase of hygienisation was marked by a very significant decrease in the number of E. coli cells (1.8 ï‚´ 107, to 3.7 ï‚´ 103, 3.8 ï‚´ 103, 3.3 ï‚´ 103, 3.2 ï‚´ 103, and 3.6 ï‚´ 103 bacteria/g) for T1 to T5 experiments, respectively: A second aspect was the investigation of a possible reduction of hazardous pollutants. The highest concentration was for Fe and the lowest for Pb, showing that Fe is the most loosely bound to the sewage sludge organic matrix and Pb the most strongly bound, the Cd reduction by composting was more than 50%.Keywords: Sewage sludge, compost, horizontal drum bioreactor, hazardous
Mems Electromagnetic Micro Relays Overview and Design Considerations
Get PDFMiniature electromagnetic relay matrices capable of switching currents up to one ampere range are widely used in commercial applications such as instrumentation and telecommunication. Traditionally these devices have been fabricated from a number of discrete components, however in recent years the emergence of Micro Electro Mechanical System (MEMS) technology has opened up the possibility for batch fabrication of microrelays at much reduced unit cost. While several electromagnetic microrelay designs have been successfully developed and commercialized for use as individual units, development work on electromagnetic microrelay matrices where individual relays can be selectively switched on and off have been fewer and less successful. Due to inherent limitations of the micromachining processes, significant dimensional and material property variations occur among individual relays in a matrix. These variations severely limit the tolerance window and hence the reliability of operation of the device. After reviewing existing designs of electromagnetic microrelays, a set of desirable design features that would make the electromagnetic microrelay more robust are identified. A novel design incorporating these features is proposed and preliminary results of ANSYS1 simulation studies are presented.Keywords: MEMS, microrelay and electromagneti