The cellular phone industry in Malaysia: toward IMT-2000

Explosive growth of the cellular phone industry in Malaysia has been witnessed in the 1990s. Eight nationwide cellular phone operators with different technology bases exist in a single market. This article provides an overview of the telecommunications industry, especially the cellular phone sector, and also the activities on IMT-2000 in Malaysia     

Air flow and thermal comfort simulation studies of wind ventilated classrooms in Malaysia

A CFD software called VORTEX is used as a tool to simulate air flow and thermal comfort in naturally wind ventilated classrooms of an educational institution, which are at different locations, have different configurations and slightly differing outdoor environmental conditions. Simulations of the various classrooms are compared to get the most thermally comfortable and uncomfortable naturally ventilated classroom. An analysis of the simulations will be done, taking into consideration, among others, location of inlets and outlets and the sheltering effect of the surrounding built-up environment. Recommendations will then be made on how to improve the ventilation of the least comfortable room, based on hypothetical simulation results.     

Problems associated with the direct torque control of an interior permanent-magnet synchronous motor drive and their remedies

This paper investigates problems associated with the implementation of a direct torque control (DTC) strategy for an interior permanent-magnet synchronous motor drive. The DTC technique is increasingly drawing attention because of elimination of current controllers and, hence, their inherent delays, and elimination of the rotor position sensor. The latter advantage perhaps is the main impetus for considering this new approach of torque control. Problems associated with this controller, namely, the offset in the current measurements, the stator resistance variation, and the requirement of initial rotor position are addressed in this paper. Ways of mitigating of these problems are also investigated in this paper. These are evaluated with modeling and experimental studies, results of which are also presented.     

Second order wave diffraction by large cylinders

A non-linear mathematical model of diffraction theory is formulated to evaluate the wave forces on large cylinders. An attempt is made to amend the coefficient of mass C_M arising in the Morison equation on the linear theory by introducing second-order effects on the irrotational flow part of the wave loading. Analytical solutions are obtained and compared with the experimental data collected by the Hydraulics Laboratory of the National Research Council of Canada, Ottawa. The comparison shows favourable agreement.     

Regional economic integration and foreign direct investment: The case of NAFTA

Abstract and Key Results

The tunable bistable and multistable memory effect in polymer nanowires

Tunable bistable and multistable resistance switching in conducting polymer nanowires has been reported. These wires show reproducible switching transition under several READ-WRITE-ERASE cycles. The switching is observed at low temperature and the ON/OFF resistance ratio for the voltage biased switching transition was found to be more than 10(3). Current biased measurements show lower ON/OFF ratio and some of the nanowires exhibit a multistable switching transition in current biased measurements. The threshold voltage for switching and the ON/OFF resistance ratio can be tuned by changing doping concentration of the nanowires.     

Model-based development of neural prostheses for movement

Neural prostheses for restoration of limb movement in paralyzed and amputee patients tend to be complex systems. Subjective intuition and trial-and-error approaches have been applied to the design and clinical fitting of simple systems with limited functionality. These approaches are time consuming, difficult to apply in larger scale, and not applicable to limbs under development with more anthropomorphic motion and actuation. The field of neural prosthetics is in need of more systematic methods, including tools that will allow users to develop accurate models of neural prostheses and simulate their behavior under various conditions before actual manufacturing or clinical application. Such virtual prototyping would provide an efficient and safe test-bed for narrowing the design choices and tuning the control parameters before actual clinical application. We describe a software environment that we have developed to facilitate the construction and modification of accurate mathematical models of paralyzed and prosthetic limbs and simulate their movement under various neural control strategies. These simulations can be run in real time with a stereoscopic display to enable design engineers and prospective users to evaluate a candidate neural prosthetic system and learn to operate it before actually receiving it.     

Investigation on hydrodynamics and mass transfer characteristics of a gas-liquid ejector using three-dimensional CFD modeling

An investigation of the gas-liquid ejector has been carried out to study the influence of operating conditions and ejector geometries on the hydrodynamics and mass transfer characteristics of the ejector by using three-dimensional CFD modeling. The CFD results were validated with experimental data. Flow field analysis and prediction of ejector performance were also conducted. Variations of the operating conditions were made by changing the gas-liquid flow rates ratio in the range of 0.2 to 1.2. The length to diameter ratio of mixing tube (L _M/D _M) was also varied from 4 to 10. CFD studies show that at L _M/D _M=5.5, the volumetric mass transfer coefficient increases with respect to gas flow rate. Meanwhile, at L _M/D _M=4, the plot of volumetric mass transfer coefficient to gas-liquid flow rate ratio reaches the maximum at gas-liquid flow rate ratio of 0.6. This study also shows that volumetric mass transfer coefficient decreases with the increase of mixing tube length.     

A comparative study of mechanical behavior of ABS material based on UVC sterilization for medical usage

This study aims to examine the mechanical properties of acrylonitrile butadiene styrene specimens using ASTM 638, 695, and 790. UVC radiation was also used as a sterilizing method. The fused deposition modeling of 3D-printed polymerize with 30% filling was used to manufacture 30 specimens for tensile, compression, and bending. Half of the specimens were treated with UVC, whereas the other half were not. The chosen dosage of 13.5 J/cm² with an exposure time of 48 min corresponds to 3650 sterilization treatments or 10 years of sterilization. The average ultimate stress in the tensile test, compression test, and bending test was 34.5 ± 7.4, 25.4 ± 0.5, and 24.5 ± 2.1 Mpa, respectively. The analysis of variance test shows that UVC radiation has a demonstrable influence on tensile specimens, with a P-value of 0.012, which is less than the significance threshold of 0.05. Thus, the null hypothesis is rejected.