Skip Navigation LinksVolume : Volume 12 No.2 2003

  
  
  
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short_communication_the_use_of_a_4-stub-tuner_for_impedance_matching_of_highly_reactive_loads.pdfSHORT COMMUNICATION THE USE OF A 4-STUB-TUNER FOR IMPEDANCE MATCHING OF HIGHLY REACTIVE LOADS
  
ABSTRACT:
This paper reports the usefulness of a 4-stub-tuner in a highly   reactive load system and involves a model that demonstrates the operation of the stub-tuner. A 4-stub~tuner was also used in a microwave plasma system   that was constructed in the laboratory. It was observed that in spite of its load, which comprises the cavity (plasma container) and the plasma, being highly inductive and the Q (quality factor) over 2-3 orders of magnitude, the  tuner managed to match the line (waveguide) to the load.       

KEYWORDS: Microwave plasma, 4-stub tuner, materials processing , quality factor           

Author: Chandan Kumar Chakrabarty
Year: 2003
short_communication_modelling_of_electrical_energy_consumption_a_case_study.pdfSHORT COMMUNICATION MODELLING OF ELECTRICAL ENERGY CONSUMPTION: A CASE STUDY
  
ABSTRACT:
Electrical energy is considered one of the most important energy sectors  of a country. This paper presents a computer model for prediction of total electrical energy consumption of a country using regression analysis. Bangladesh, a developing   country, was taken as a case study. Graphical representation of the proposed model  can give a vivid picture of the status of the electrical energy consumption for the past   and future years to the policy makers of a country. This therefo re helps in taking  necessary measures to meet the future demands of energy efficiently and effectively.  The technique is applicable to other sectors of energy consumption of a country. 

KEYWORDS: Electrical energy, modeling, regression 

Author: Md. Liakot Ali, Shahidul Islam Khan, Mohd. Alauddin Mohd. Ali and Mohibullah
Year: 2003
effect_of_vibration_and_gas_velocity_on_umf_and_elutriation_rate_constant_of_starch_powders.pdfEFFECT OF VIBRATION AND GAS VELOCITY ON UMF AND ELUTRIATION RATE CONSTANT OF STARCH POWDERS
  
ABSTRACT:
Batch experimental work on fluidisation hydrodynamic and entrainment   phenomena of Group C starch powders was studied. Using a vibrated fluidised bed,   it was estimated that the effective mean particle size, dagg , in the bed at minimum fluidisation velocity, Umf  , was 2 or 3 times larger than the actual mean particle size of   each feed material. The formation of agglomerates in the bed has reduced material loss by entrainment. It was found that for all the powder used, entrainment was only  in the range of 0.5-1 .7% of the total fines that should be entrained from the bed. The  elutriation rate constants of the powders decreased as particle size decreased. By   adapting the criterion proposed by Ma and Kato (1998), it was found in this case that the critical cohesion number, Ncoh * is 19. 

KEYWORDS: Fluidisation, group C, vibration, entrainment, elutriation rate constant  
          
Author: Siti Masrinda Tasirin and Nornizar Anuar
Year: 2003
effect_of_lubricant_on_strength_of_alumina_particulate_reinforced_aluminium_composites_produced_by_hot_pressing_technique.pdfEFFECT OF LUBRICANT ON STRENGTH OF ALUMINA PARTICULATE REINFORCED ALUMINIUM COMPOSITES PRODUCED BY HOT PRESSING TECHNIQUE
  
ABSTRACT:
Metal matrix composites (MMCs) are advanced materials that have been developed for aerospace and automotive applications. Properties of MMCs very much   depend on the particle size distribution, particle shape, volume fraction of reinforcement in the matrix, distribution of reinforcement in the matrix and the fabrication technique   involved. In Powder Metallurgy (PM) technology, a lubricant is used to decrease a   friction force, which occur between the powders and the die wall. At the same time, with lubricant, it is possible to achieve a homogeneous distribution of some elements in a metal powder and also to increase the mechanical properties of the sintered   product. In this study, effect of lubricant on the strength of the MMCs was investigated.   Zinc stearate (ZnS) was chosen as the lubricant. 10 volume fraction (vol.%) of Al2O3  particulate reinforced aluminium alloy      (Al 6061) MMCs were produced using different   weight percent (wt.%) of ZnS, which were 0 wt. %, 0.1 wt.% , 0 .5 wt. %, 1.0 wt.% and   1.5 wt. %. A12O3, Al 6061 and ZnS were mixed by ball milling process according to the   required formulation. For this investigation, the MMCs were produced by hot pressing technique. The hot pressed samples were sectioned to the required shape for threepoint bending test. The fracture surface of the samples was observed under scanning   electron microscope (SEM) for surface evaluation . Results show that an addition of   ZnS improve the bending strength of the MMCs. 

KEYWORDS: Metal matrix composites, aluminium alloy, alumina, hot pressing, bending strength, porosity       

Author: Junaidah Jai
Year: 2003
development_of_acoustic_materials_using_coia_fibre_and_natural_fibre_composite_panels.pdfDEVELOPMENT OF ACOUSTIC MATERIALS USING COIA FIBRE AND NATURAL FIBRE COMPOSITE PANELS
  
ABSTRACT:
This paper presents the development of novel sound absorbing materials   based on natural indigenous resources particularly that of fibrous nature. The raw material used as the main absorbing component was coir mat backed by natural fibre composite   panels. The panels were made from oil palm frond fibre (OPF) and rice husk (RH) bounded   in either unsaturated polyester (UP) or polypropylene (PP) matrix. The acoustical properties   of the composite structures were determined in an impedance tube based on the twomicrophone  transfer function method in the frequency range of 125Hz to 4000Hz. Overall  results indicate that the coir mat-composite panel structure is a potential absorbent-barrier with not less than 50% of sound absorption . General improvements were achieved in the absorption properties over the entire frequency range using the more flexible RH-PP  panel while superior low frequency absorption was attained using panel made of 50% volume fraction of OPF/RH mixture in UP. The experimental results were analysed based   on the variation of two essential acoustical properties i.e. the normal specific surface impedance and normal surface admittance values. The product of this research offers  exceptional cost-performance balance to the existing, relatively expensive noise control  industry while reducing waste disposal problems in the plantation industry.       

KEYWORDS: Acoustic materials, sound absorption, natural fibre, acoustic impedance,  acoustic admittance.           

Author: Mohd Jailani Mohd Nor and Valliyappan D. Natarajan
Year: 2003
analysis_of_lead_count_effect_on_gap_formation_in_the_seal_used_for_lead_frame_electroplating_process.pdfANALYSIS OF LEAD COUNT EFFECT ON GAP FORMATION IN THE SEAL USED FOR LEAD FRAME ELECTROPLATING PROCESS
  
ABSTRACT:
Lead frame is intricately designed and engineered to form the basic metal base network  of an integrated circuit. Desired geometry and size of plated spots are deposited onto the lead frame  through the electroplating process. An intermittent seal carries out the task of defining the plated   geometry by limiting the flow of electrolyte within the plated area. The seal is made of two parts, the top seal is made from silicone base elastomer while the bottom seal is made from a layer of thin elastomer on a sponge-like material. Leakage that causes product reject still occurs under certain conditions. This is believed to be caused by the gap existing between the lead and the seal. The gap   that exists under actual operating condition will allow the electrolyte to seep through and deposit excess metal outside the specified geometry. Thus, it is important to understand the formation of gaps   to fully control the plating process. One of the parameters which influence the gap formation is the   lead count on the lead frame. A two-dimensional finite element analysis was carried out using Mooney-Rivlin  material model for the elastomer and Blatz-Ko material model for the sponge material. The   contact analysis is used to determine areas of contact with the non-contact area identified as the gap between the lead and the seal. Several load steps were used in the analysis to monitor the gap size reduction with the applied load. Different numbers of leads were used in the analysis to determine the   effect of lead count on the gap formation. The results showed that gap area becomes smaller as the   applied load increase, with the tendency to decrease more rapidly for the lower lead count. The   maximum gap size consistently occurs at the first and last inner gap. The maximum gap size was  used as the performance measure of the seal and when plotted against the load step showed a trend of decreasing gap area as the load increase. The results indicated that lead count is an important parameter affecting the gap area. 

KEYWORDS: Electroplating, intermittent seal, finite element method, gap

Author: Zaidi Mohd Ripin, Tee Boon Hoo and Ahmad Baharuddin Abdullah
Year: 2003