bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress and Thermal Analysis of CubeSat Structure
Authors: Athirah Nur , Afendi Mohd , Hafizan Ku , Amin N.A.M. , Majid M.S. Abdul
Published: June 2014

This paper presents the stress and thermal analysis on the CubeSat structure to study the survivability of the CubeSat during the launching process or operating condition at the orbit is presented. Various design of mechanical structures were analyzed to determine the best design for different mission requirements. Analysis on the temperature of the batteries will be conducted as it is one of the most critical components that must operate in the required temperature to avoid failure of the CubeSat. ANSYS 13.0 was used to simulate both the structural and thermal analysis. Static structural was used to study the impact of G-force on the CubeSat during the launching process and Icepak was used to study the internal temperature. All of the result will be compiled in the table and comparisons were made among different designs to determine the advantages and disadvantages of each design. Results from simulation such as: safety factor, weight, internal available space and battery discharge rate were analyzed. From the findings, there is no best design in the CubeSat structure but only the most suitable design for the mission purposes. Battery discharge rate will play an important role to determine the requirement of heater in CubeSat.
Predicting Surface Roughness in Turning Operation Using Extreme Learning Machine
Authors: Nooraziah Ahmad , Tiagrajah V. Janahiraman
Published: June 2014

Prediction model allows the machinist to determine the values of the cutting performance before machining. According to literature, various modeling techniques have been investigated and applied to predict the cutting parameters. Recently, Extreme Learning Machine (ELM) has been introduced as the alternative to overcome the limitation from the previous methods. ELM has similar structure as single hidden layer feedforward neural network with analytically to determine output weight. By comparing to Response Surface Methodology, Support Vector Machine and Neural Network, this paper proposed the prediction of surface roughness using ELM method. The result indicates that ELM can yield satisfactory solution for predicting surface roughness in term of training speed and parameter selection.
Estimation of Threshold Fluence, Absorption Coefficient and Thermal Loading of Car Coated Substrate in Laser Paint Removal
Authors: Abdul Razab Mohammad Khairul Azhar , Jaafar Mohamad Suhaimi , Rahman Azhar Abdul , Saidi Syahrul Affandi
Published: June 2014

Threshold fluence (FT), absorption coefficient (α) and thermal loading (γ) were estimated on three types of car coated substrate by applying Beer-Lambert law. Cynosure Cynergy Pulse Nd:YAG was using to irradiate 54 substrate samples and the depth of coating removed (d) was obtained by using Alicona IFM G4. Depth of coating removed (d) versus laser fluence (F) graphs was plotted for each pulse width (PW), repetition rate (RR) and beam size (BS) considered by measuring the average of coating removal efficiency (ε). The best interceptions of certains ε with their X-axis were selected for each sample A, B and C, representing their generalFT, α and γ respectively.
The Effects of Alkaline Catalysts in Used Frying Oil Biodiesel on the Diesel Engine Performances
Authors: Zamberi Mahanum , Ani Farid Nasir , Herawan Safaruddin Gazali
Published: June 2014

The biodiesel, defined as monoalkyl esters from waste vegetable oils are being produced widely as a viable alternative diesel fuels due to its lower cost, largest producer and reduces the disposal problem. In this study, the effects of catalyst formulation on biodiesel yield are evaluated by using three different alkaline catalyst; sodium hydroxide (NaOH), potassium hydroxide (KOH) and sodium methoxide (NaOCH3) with methanol via transesterification process and are tested in a four cylinder Mitsubishi Pajero 2.5cc Intercooler Turbo Diesel Engine. The engine emissions and performance were recorded under partial load within the range of 1000 to 3500 rpm of the biodiesel (B100) fuels compared with the diesel fuel. The best yield percentage was obtained using NaOCH3 as catalyst whilst KOH is the most convenient and simpler in process. NaOH was found to be more superior than the other two catalysts in terms of lower cost production and low engine emission.
Performance Study of Electric Compressor in Non-Electric Vehicle
Authors: Afiq Aiman Dahlan , Haziqah Zulkifli Amirah , Henry Nasution , Azhar Abdul Aziz , Perang Mohd Rozi Mohd , Mohd Jamil Hishammudin
Published: June 2014

The usage of electric compressor inside conventional non-electric vehicle is a new shifts in current vehicle air conditioning system which currently using belt-driven compressor to operate. The usage of belt-driven compressor causes the compressor speed to vary with engine speed rotation, which we cannot control. The usage of electric compressor to replace the belt-driven compressor makes the speed to be according to the cooling load and thus reducing engine load. The current research activity focuses on the development of electric compressor using direct current (DC) from vehicles battery to replace current belt-driven in vehicle air conditioning system. Performance study is focusing on temperature inside cabin, cooling capacity, compressor power consumption and coefficient of performance (COP). The DC compressor speed is varying at 1800, 2000, 2200, 2400, 2500 and 3000 rpm at internal heat load of 1000W with temperature set-point of 20°C. The system uses On/Off controller and compared to belt-driven compressor. The overall experimental results in better energy efficiency at the expense of lower cooling capacity.
The Effects of Nickel Underlayer and Solder Dipping as Tin Whisker Mitigations in Tin Surface Finishes
Authors: Lim Hooi Peng , Ourdjini Ali , Abu Bakar Tuty Asma
Published: June 2014

Driven by environmental concerns and the enforcement of Restriction of Hazardous Substances Directive (RoHS) to ban the use of lead in electronics, the global electronics industry has migrated toward lead-free electronics. However, the adoption of lead-free tin (Sn) surface finish is known to form whiskers. These whiskers grow spontaneously from the Sn finish layer as a stress-relief over time causing device failures. In the present research, whisker growth is investigated via immersion Sn finishes on Cu substrate. The effects of Sn layer thickness, addition of Ni under-layer and solder dipping on whisker growth are investigated by storing the samples under ambient temperature for up to 24 weeks. The effects of external stresses were also studied using bending test. The results showed that whisker length on immersion Sn increases with time for all the samples either with or without Ni under-layer. Thicker Sn coating showed more whisker growth compared with thinner Sn coating. The longest whisker length of 23μm was observed for Sn coating with 2μm thickness. The addition of Ni as under-layer was found to be more effective in mitigating the whisker growth by extending the incubation time for whisker formation. Compared to immersion Sn, solder dipping in pure Sn showed no whisker growth. However, alloying Sn with 0.4%wtCu resulted in whisker growth indicating the role of Cu in promoting whiskers formation.
Effects of Storage Duration on Biodiesel Properties Derived from Waste Cooking Oil
Authors: Khalid Amir , Azman Norazwan , Zakaria Hanis , Manshoor Bukhari , Zaman Izzuddin , Sapit Azwan , Leman Abdul Mutalib
Published: June 2014

The reduction of world oil reserves fossil fuels and increasing environmental concerns significantly influences the popularity of biodiesel as an alternative diesel. This research investigates the effects of storage duration of variant blending waste cooking oil ratio under different storage temperature on fuel properties.
The biodiesel samples were stored at different temperatures and were monitored at regular interval over a period of 70 days. Blending of biodiesel was varied from 5vol % (WCO5) ~15vol% (WCO15) and storage temperature from 24°C~35°C. These samples were monitored on a weekly and the effects of storage conditions on properties of biodiesel such as density, kinematics viscosity, acid value, water content and flash point of biodiesel were discussed in detail. The observation of biodiesel shows that the increasing of storage duration of biodiesel derived from waste cocking oil influences to the increasing of density, kinematics viscosity, acid value and water content.
Performance Comparison between Diesel Fuel and Biodiesel Using a Low Cost Single Cylinder Diesel Engine Dynamometer
Authors: Jamaludin Mohd Zaini , Herawan Safaruddin Gazali , Yusmady Mohamed Arifin , Fauzi Ahmad
Published: June 2014

Nowadays, biodiesel from non-edible feedstock is gaining more concern than edible oil to substitute diesel fuel. The purpose of this study is to investigate the performance of low cost single cylinder diesel engine fuelled by regular diesel and B5 biodiesel of castor and jatropha. The experiments were conducted to identify the performance of a low cost single cylinder diesel engine dynamometer, in terms of engine torque, engine power, and brake specific fuel consumption. It was found that these biodiesel can be used as the alternative fuel based on the performance of engine dynamometer, where the results show nearly similar with regular diesel.
Screening Efficiency and Entrepreneurship Potential in Automotive Suppliers Using DEA
Authors: Moradi Deluyi Amir Hosein , Sofian Saudah , Abdul Hamid Abu Bakar , Kazemi Mostafa
Published: June 2014

This study aims to screen entrepreneurial potentials of automotive manufacturing and performance criteria. Supplier selection as a key part of supply chain management (SCM) facilitates the creation of sustainable competitive advantage that can cause new ventures and business growth development. Efficient supplier selection method is a main part in SCM for outsourcing in businesses. The character of supplier selection is a multi-criteria decision making (MCDM) problem and multiple criteria should be respected in the selection procedure. This study assessed the suppliers’ efficiency through Data Envelopments Analysis (DEA). Keyword: Supply chain management, supplier selection, multi-criteria decision making, DEA
Fabrication and Characterization of Polycaprolactone (PCL)/Gelatin Electrospun Fibers
Authors: Lim Mim Mim , Sultana Naznin , Bin Yahya Azli
Published: June 2014

Over the past few decades, there has been considerable interest in developing electrospun fibers by using electrospinning technique for various applications. Polymer blending is one of the most effective methods in providing desired properties. In this study, synthetic polymer polycaprolactone (PCL) was blended together with natural polymer gelatin where both of them have different properties. It is done by using electrospinning technique. 10 %w/v and 14 %w/v PCL/gelatin electrospun fibers were successfully electrospun with different weight ratio. Processing parameters were set constant in this study and only solution parameters were altered. The optimized electrospun fiber formed was 14 %w/v PCL/gelatin 70:30 with average fiber diameter of 246.30 nm. No beaded fiber was formed in this scanning electron microscope (SEM) image. The result obtained also showed that by increasing the overall polymeric concentration of PCL/gelatin, average fiber diameter decreases. Fiber diameter was also found decreasing with the increase of the concentration of gelatin in the same concentratoin of PCL/gelatin blended electrospun fiber. Blending of PCL and gelatin in different weight ratio had provided different properties of electrospun fibers. It is believed that blended electrospun fibers can be used for biomedical applications.
Optimal Composite Nonlinear Feedback Controller for an Active Front Steering System
Authors: Ramli Liyana , Sam Yahya M. , Mohamed Zaharuddin , Aripin Muhamad Khairi , Ismail Muhamad Fahezal
Published: June 2014

Yaw stability control is the most popular topics in the automotive field. Several studies have been done in searching the effective method in controlling yaw moment. Hence, an integration of the active front steering system (AFS) with Composite Nonlinear Feedback controller is presented in this paper. Recently, this controller has been used by a lot of researchers in controlling their system performance due to its main advantage that can be seen in transient response which demonstrate super fast tracking. An optimal CNF feedback control problem is formulated as a parameter optimization problem with performance index and restrictions on stability. To handle such restrictions and constraint, the particle swarm optimization algorithm is applied to solve parameter optimization problems.
Hybrid Model for Evaluation of Manufacturing Sustainability Using Axiomatic Design Principles: A Case of Machining Processes
Authors: Beng Lee Guang , Omar Badrul
Published: June 2014

Despite being a manufacturing technique that consumes energy and material, machining is often regarded as an important process due to the fact that it is flexible and is able to produce economic parts. However, to gain more cost-saving and enhanced environmental performance, sustainability principles have to be incorporated into machining technologies. This paper presents a case study that applies both crisp and fuzzy axiomatic design approach to construct a hybrid model with the purpose of facilitating the selection of sustainable manufacturing process. By converting numerical terms and linguistic factors into quantifiable score (in the form of information content), the proposed approach is able to produce indicative results and is capable of identifying the most sustainable process among three alternatives. Potentially, such information can be helpful for product development companies which strive to achieve sustainable product realization.
Implementation of Wheelchair Motion Control Based on Electrooculography Using Simulation and Experimental Performance Testing
Authors: Mohd Noor Nurul Muthmainnah , Ahmad Salmiah , Sidek Sharul Naim
Published: June 2014

The aim of this study is to perform the experimental verification on the fuzzy-based control designed for wheelchair motion. This motion control based on the eye movement signals using electrooculograhphy (EOG) technique. The EOG is a technique to acquire the eye movement data from a person, i.e tetraplegia, which the data obtained, can be used as a main communication tool. This study is about the implementation of the designed controller using PD-type fuzzy controller and tested on the hardware of the wheelchair system using the eye movement signal obtained through EOG technique as the motion input references. The results obtained show that the PD-type fuzzy logic controller designed has successfully managed to track the input reference for linear motion set (forward and backward direction) by the EOG signal.
Polycaprolactone(PCL)/Gelati(Ge)-Based Electrospun Nanofibers for Tissue Engineering and Drug Delivery Application
Authors: Chong Lor Huai , Lim Mim Mim , Sultana Naznin
Published: June 2014

Recent development of tissue engineering has been emphasized on tissue regeneration and repairing in order to solve the limitation of organ and tissue transplantation issues. Biomaterial scaffold, which plays an important role in this development, not only provides a promising alternative in order to improve the efficiency of cell transplantation in tissue engineering but also to deliver cells with growth factors and drugs into injured tissue to increase the survival of cell via drug delivery system. In this study, nanofibers were fabricated through blending of a synthetic polymer polycaprolactone (PCL) and a natural polymer Gelatin (Ge) using electrospinning technique. Processing parameters were optimized to determine the most suitable properties of PCL/Ge nanofibers. The surface morphology of PCL/Ge nanofibers were then characterized using Scanning Electron Microscopy (SEM). Six samples of nanofibers from different amount of gelatin mixed with 10% PCL (w/v) were successfully fabricated. Experimental results showed that 18kV of high voltage provided more homogenous and less beaded nanofibers. Meanwhile, the 0.8g of Ge in 10% PCL (w/v) was set as the maximum concentration while 0.2g of Ge in 10% PCL (w/v) was set as the minimum concentration to reduce the bead formation.
Correlation between Third Harmonic Leakage Current and Thermography Image of Zinc Oxide Surge Arrester for Fault Monitoring Using Artificial Neural Network
Authors: Novizon Yusuf , Zulkurnain Abdul Malek , Zulkurnain Abdul Malek
Published: June 2014

The ageing level of ZnO materials in gapless surge arresters can be determined by using either the traditional leakage current measurements or recently introduced thermal images of the arrester. However, a direct correlation between arrester thermal images and its leakage current (and hence the ageing level) is yet to be established. This paper attempts to find such a correlation using an artificial neural network (ANN). Experimental work was carried out to capture both the thermal images and leakage current of 120kV rated polymeric housed gapless arresters. Critical parameters were then extracted from both the thermal image and the leakage current, before being exported into the artificial neural network tool. Using the leakage current level, the conditions of the arrester are classified as normal, caution, and faulty. The ANN correctly classifies the ageing level using only the thermal image information with an accuracy of 97%, which is highly encouraging.
Model of Pulse Power Generator in Electrical Discharge Machining (EDM) System
Authors: Erawan Minhat Ade , Yahya Azli , Nor Hisham Khamis , Samosir Ahmad Saudi , Rahim Muhammad Arif Abdul , Trias Andromeda , Kartiko Juli Purwanto Nugroho
Published: June 2014

Electrical discharge machining (EDM) is a non-traditional manufacturing process of removing material. EDM system consists of a shaped tool and the work piece, which are connected to a power supply and placed in a dielectric fluid. EDM pulse power generator applies voltage pulses between the electrode and workpiece to generate sparks through the gap. The essential requirement for EDM system is to obtain the output waveform similar to the ideal EDM waveform. The design is based on transistor type pulse power generator circuit. This paper discuss in modeling of current and voltage gap waveform for EDM system.
Return Strokes Measurements of Electric Field Produced by Lightning Discharges in Malaysia
Authors: Mehranzamir Kamyar , Abdul-Malek Zulkurnain , Salimi Behnam , Ahmad Noor Azlinda
Published: June 2014

The physics of cloud discharges have not been known completely yet. The cloud to ground discharges is divided by researchers into several stages to make the analyses of lightning flash easier. The first step is preliminary breakdown which is called to pre-starting process prior to leader initiation within the clouds. The leader initiation precedes return strokes in continuing the cloud discharges. The time and amplitude of lightning waveforms differs in each flash with the other ones due to the stochastic characteristics of lightning flashes. This research tries to add more analyses to few previous researches done in tropical regions. On the other hand, observations of this study is compared with those obtained in Sweden to show the differences between statistics of return strokes in Malaysia and Sweden as a temperate region. A broadband antenna and a buffer system for amplifying input signal and also impedance matching is used in this study for capturing electric field of lightning waveforms to carry out statistical analyses on them in Johor, Malaysia. The percentage of single stroke flashes was 18% in Sweden and 12.1% in this study which shows single strokes happens more in temperate regions rather than tropical regions. Total number of 568 subsequent return strokes out of 271 flashes shows a Mean number of 3.4 strokes per flash in Sweden compared with 184 subsequent strokes out of 58 flashes in this study which presents 4.1 strokes per flash in average.
Mechanical Properties of Polyamide 6 (Pa6) / Ethylene Vinyl Acetate (Eva) / Sepiolite Composite
Authors: Fauzi Noora Tiqah Mohamad , Mohamad Zurina
Published: June 2014

The objective of this study is to investigate the effect of sepiolite concentration (2-10 phr) on the mechanical properties of polyamide 6 (PA6) / ethylene vinyl acetate (EVA) blend at the ratio 80/20. Twin screw extruder and injection moulding machine were used to prepare the samples. The strength and modulus of flexural was increased until 6 phr of sepiolite content. On the other hand, the impact strength of PA6/EVA/sepiolite composite was decreased gradually as sepiolite content increased.
Supply Chain Performance in Electronics Manufacturing Industry
Authors: Balfaqih Hasan , Yunus Bahisham
Published: June 2014

It is still not clear how supply chain management can be applied to enhance and improve the performance of the supply chain. Consequently, the purpose of this research is to investigate the effect of five different factors in supply chain on its performance. This research studies the relationship between the selected variables (i.e. quality, time, information, flexibility, and integration) and supply chain management performance. This research takes a step forward to better understand the relationship between supply chain management factors and supply chain performance by incorporating these variables into the industrial landscape of electronics manufacturing in Malaysia. Specifically by using a combination model of a unified framework combining SCOR Model (Supply Chain Council, 1997) and system approach model (Min &Mentzer, 2004). As such, the analysis in this study contributes to the empirical literature of supply chain management, policy progress, as well as managerial implications. The outcome of this study also signifies the contribution it has given towards a new shift in upgrading the manufacturing best practices in developing countries through effective supply chain management practices.
Gap Response of Linear and Non-Linear Discharge Model in Electrical Discharge Machining System
Authors: Trias Andromeda , Yahya Azli , Nor Hisham Khamis
Published: June 2014

In recent years, simulation-based research is highly appreciated. So many researchers use this way to investigate and solve some problems. Empirical model or behavioral model is used to bring the problems into computer or other computing devices. Selection and determination of the model is very important on the outcome of research. In Electrical Discharge Machining system, servo control system uses voltage drop between electrode and workpiece as a feedback signal. Discharge phenomenon convert gap or distance between electrode and workpiece to voltage. In this paper, two discharge models are simulated and compared. Simulation results show that there are behavior’s differences between these models.
The Study of Morphological Structure and Raman Spectra of 3C-SiC Membranes
Authors: Nasir Fazli Mohd Nashrul , Leech Patrick W. , Reeves Geoff K. , Johnson Brett C. , Tanner Philip , Holland Anthony S.
Published: June 2014

In this paper, membranes of 3C-SiC with dimensions up to 10 mm x 15 mm2 have been fabricated in epitaxial 3C-SiC/ Si wafers by the means of photolithography, reactive ion etching of 3C-SiC and wet etching of Si. Scanning electron microscope (SEM) micrographs were used to observe the structure of the membrane and the wall formed by the Si wet etching. The quality of the 3C-SiC membranes were observed using Raman Spectroscopy. The remains of <111> Si substrate which was unetched during the Si wet etching were presented with the formation of microstructure defects which showed distinct peaks in comparison to the high quality 3C-SiC membranes at different position. Here, the effect of the membrane fabrication procedures to the 3C-SiC membrane properties especially the morphological structure and its Raman characteristics is discussed in detail.
Two-Sided Lid-Driven Cavity Flow at Different Speed Ratio by Lattice Boltzmann Method
Authors: Che Sidik Nor Azwadi , Razali Siti Aisyah
Published: June 2014

In this study, the Lattice Boltzmann method has been used to investigate flow configuration of the two-sided lid driven cavity. The top and bottom lid were moved at the same direction but with different speed ratio which varies from 0 to 1. The range of Reynolds number is 100,400 and 1000. The results show that the increase in both speed ratio and Reynolds number give an effect on flow configuration of the cavity.
Numerical Prediction of Thermal Effect on Flow Field around a High-Rise Building Model
Authors: Behrouzi Fatemeh , Malik Adi Maimun Abdul , Che Sidik Nor Azwadi , Nakisa Mehdi , Witri Afiq Muhammad Yazid
Published: June 2014

Recently, CFD (Computational Fluid Dynamics) is being more and more used in the investigation of the flow and thermal around high-rise buildings. In this study, prediction of thermal effect on flow pattern around high-rise buildings model located in the surface boundary layer was carried out using k-e turbulence model. Investigation of thermal effect on flow pattern behind the building and comparison between isothermal and non-isothermal building using standard k-e showed that the surface temperature of building wall led to a strong upward motion close to heating wall and decreased the reattachment length behind it. The model sittings of validation study was accomplished by comparing the simulation of wind flow around building models with the experimental data of Architectural Institute of Japan (AIJ) that results showed in weak wind region, standard k-e has good agreement with experimental.
Measurement of Thermophoretic Velocity in Surrounding Gas of Nitrogen or Carbon Dioxide
Authors: Azahari Mohd , Sapit Azwan , Fawzi Mas , Khalid Amir , Mohammed Akmal
Published: June 2014

Several experiments are conducted under the microgravity condition, which is achieved by a free-fall, for measuring the thermophoretic velocity in surrounding gas of nitrogen and carbon dioxide. PMMA spheres are used as measured particles, which are 2.91μm in mean diameter. The temperature gradient is 10 K/mm and the pressure is the range between 20 kPa and 100 kPa. Velocities of particles are individually measured during 0.25 s of the microgravity condition and the measurements are repeated in order to attain the accuracy by accumulating data. Comparison between obtained experimental results and theoretical predictions are done; the result for nitrogen is consistent with prediction, while a notable discrepancy is found for carbon dioxide. The disagreement is fixed by modifying the tangential momentum accommodation coefficient.
Comparison of Dry and Cryogenic Machining on Chip Formation and Coefficient of Friction in Turning AISI 4340 Alloy Steel
Authors: Raof Natasha A. , Ghani Jaharah A. , Syarif Junaidi , Che Haron Che Hassan , Hadi Musfirah Abdul
Published: June 2014

Application of cutting fluid that provides both coolant and lubrication properties in manufacturing operations such as turning, milling, grinding and other processes has been proven to improve the machining output in many aspects. In cryogenic machining, liquid nitrogen (LN2) is used as cutting fluid to reduce the temperature generated at the cutting zone. However, there is still an issue being raised on whether LN2 also functions as a good lubricant as it does as an excellent coolant. Therefore, an intensive study on the chip formation during dry and cryogenic turning of AISI 4340 alloy steel has been conducted to examine the effect of LN2 cutting fluid on the reduction of friction between the chip and the tool. Results from calculation of coefficient of friction indicate that application of LN2 during turning is able to help the friction reduction up to 73%. Smaller value of coefficient of friction indicates that the shear angle is larger which results in smaller shear plane area that provides benefits of lower cutting force needed to shear off the chips and lower cutting temperature being generated during the machining process.
Derivation of Effective Ratio of Acoustic Impedance for Impacting Viscoelastic Slug (Standard Linear Solid Model) and Elastic Rod
Authors: Musa Abu Bakar
Published: June 2014

The study is about impact of a short viscoelastic slug on a stationary semi-infinite viscoelastic rod. The viscoelastic materials are modeled as standard linear solid which involve three material parameters and the motion is treated as one-dimensional. We first establish the governing equations pertaining to the impact of viscoelastic materials subject to certain boundary conditions for the case when a viscoelastic slug moving at a speed impacts a semi-infinite stationary viscoelastic rod. In order to validate the numerical results, we derive the effective ratio of acoustic impedance for impacting rods which will be used in the viscoelastic discontinuity analysis.
The objective of this study is to investigate how the viscosity time constants in the slug and in the rod give rise to different interface stresses and interface velocities following wave transmission in the slug. After modeling the impact and solving the governing system of partial differential equations in the Laplace transform domain, we invert the Laplace transformed solution numerically to obtain the stresses and velocities. In inverting the Laplace transformed equations we used the complex inversion formula (Bromwich contour). In validating the numerical results, the method of viscoelastic discontinuity analysis is engaged to determine the first discontinuity jump at the interface. Finally, we discussed the relationship between the viscosity time constants, ratios of acoustic impedances and the results of the viscoelastic impacts obtained numerically and the predictions acquired using the multiple scales in perturbation.
Preliminary Study on Bamboo as Sound Absorber
Authors: Khair Fazlin A. , Putra Azma , Mohd Nor Mohd Jailani , Atiqah Nurul , Selamat M.Z.
Published: June 2014

Synthetic acoustic materials are known for their poisonous chemical substance to the environment and also the particles which are harmful to human health. Research is now directed towards finding an alternative acoustic absorber made from natural materials. This paper presents the utilization of bamboo, a natural material having hollow structure to act as sound absorber. In an impedance tube test, the hollow path is arranged to face the sound incidence. The result reveals that bamboo having length of 2 cm has average absorption coefficient of 0.95 at frequency above 3 kHz. Performance at lower frequencies can be controlled by adding the air gap behind the system. Introduction of microholes along the body shows no significant effect to increase the sound absorption.
Influence of Compatibilizer on Mechanical Properties of Polylactic Acid/Natural Rubber Blends
Authors: Mohammad Nor Nisa Balqis , Arsad Agus , Rahmat Abdul Razak , Talib Mohammad Shukor , Mat Desa Mohd Shaiful Zaidi
Published: June 2014

Derived from renewable resources, Poly (lactic) acid (PLA) exhibits good mechanical properties comparable with conventional polyolefins. However, major obstacle in PLA which may limit its application is due to brittleness. Thus, PLA requires toughening to overcome the weakness. In this study, PLA was blended with different ratio of natural rubber (0 to 20 wt.%) through melt blending in a twin screw extruder. The results of tensile strength and Young’s modulus of PLA/NR blends were decreased. In order to enhance the blend performance, PLA grafted maleic anhydride (PLA-g-MA) was used as compatibilizer. The preparation of PLA-g-MA was carried out using internal mixer by free radical melt grafting reaction followed by Fourier Transform Infrared Spectroscopy (FTIR) analysis to confirm the grafting reaction. To investigate the compatibilization effect on the mechanical properties of PLA/NR blends, PLA-g-MA was added to the blends at various compositions (1 – 10 phr). Mechanical properties increased markedly compared to the virgin PLA/NR blends and FTIR result confirmed grafting reaction occurred between MA and PLA.
Preparation and Characterization of Polyvinyl Alcohol/Starch Blend Film Composite
Authors: Lani Nurul Saadiah , Ngadi Norzita
Published: June 2014

Nowadays, the demands of plastics materials are increasing rapidly. Nevertheless, most of these products are non-environmentally friendly and non–biodegradable. Polyvinyl alcohol (PVA) is one of the polymers that have been investigated widely for the potential for use as biodegradable plastics. However, the applications of PVA materials are limited due to their high cost and slow degradation process especially under anaerobic condition. Therefore, this study was conducted to investigate the effect of varying the PVA and starch content on the composite properties. A series of blend films with different ratio of PVA and starch were prepared by solution casting method. The results of this study have revealed that the polyvinyl alcohol and starch at a weight ratio of 70:30 was selected as the best blending composition, whereby the 70:30 blend film have the best elongation at break at about 334.69%, with a tolerable tensile strength value and water absorption capacity of 3.830 MPa and 49.59%, respectively.
Cutting Edge: Dexamethasone Potentiates the Responses of Both Regulatory T Cells and B-1 Cells to Antigen Immunization in the ApoE−/− Mouse Model of Atherosclerosis
Authors: Chen Aoshuang , Geng Yajun , Ke Hanzhong , Constant Laura , Yan Zhaoqi , Pan Yue , Lee Patricia , Tan Isaiah , Williams Kurt , George Samantha , Munirathinam Gnanasekar , Reardon Catherine A. , Getz Godfrey S. , Wang Bin , Zheng Guoxing
Published: June 2014

The immunosuppressant dexamethasone was shown to preferentially deplete CD4+ effector T cells while sparing regulatory T cells (Tregs) in vivo. In the current study, we show that it also preferentially depletes B-2 cells while sparing B-1 cells. In the ApoE−/− mouse model of atherosclerosis, in which both Tregs and B-1 cells are thought to play an atheroprotective role, we show that HSP60-targeted immunization in the presence of dexamethasone raises Ag-reactive Tregs and B-1 cells concomitantly and reduces the severity of atherosclerosis. These results indicate that dexamethasone is an adjuvant that potentiates both the Treg and B-1 responses to immunogens. This study shows that B-1 cells with a specificity for a disease-relevant Ag can be raised in vivo by immunization.
Inhibition of Bone Remodeling in Young Mice by Bisphosphonate Displaces the Plasma Cell Niche into the Spleen
Authors: Teufel Stefan , Grötsch Bettina , Luther Julia , Derer Anja , Schinke Thorsten , Amling Michael , Schett Georg , Mielenz Dirk , David Jean-Pierre
Published: June 2014

The bone marrow provides niches for early B cell differentiation and long-lived plasma cells. Therefore, it has been hypothesized that perturbing bone homeostasis might impact B cell function and Ab production. This hypothesis is highly relevant for patients receiving long-term treatment with antiresorptive drugs. We therefore analyzed the humoral immune response of mice chronically treated with ibandronate, a commonly used bisphosphonate. We confirmed the increased bone mass caused by inhibition of osteoclast activity and also the strongly reduced bone formation because of decreased osteoblast numbers in response to ibandronate. Thus, bisphosphonate drastically inhibited bone remodeling. When ibandronate was injected into mice after a primary immunization to mimic common antiosteoporotic treatments, the generation of the various B cell populations, the response to booster immunization, and the generation of plasma cells were surprisingly normal. Mice also responded normally to immunization when ibandronate was applied to naive mice. However, there, ibandronate shunted the homing of bone marrow plasma cells. Interestingly, ibandronate reduced the numbers of megakaryocytes, a known component of the bone marrow plasma cell niche. In line with normal Ab responses, increased plasma cell populations associated with increased megakaryocyte numbers were then observed in the spleens of the ibandronate-treated mice. Thus, although inhibition of bone remodeling disturbed the bone marrow plasma cell niche, a compensatory niche may have been created by relocating the megakaryocytes into the spleen, thereby allowing normal B cell responses. Therefore, megakaryocytes may act as a key regulator of plasma cell niche plasticity.
Specific Microbiota-Induced Intestinal Th17 Differentiation Requires MHC Class II but Not GALT and Mesenteric Lymph Nodes
Authors: Geem Duke , Medina-Contreras Oscar , McBride Michelle , Newberry Rodney D. , Koni Pandelakis A. , Denning Timothy L.
Published: June 2014

IL-17–expressing CD4+ T lymphocytes (Th17 cells) naturally reside in the intestine where specific cytokines and microbiota, such as segmented filamentous bacteria (SFB), promote their differentiation. Intestinal Th17 cells are thought to initially differentiate in the GALT and/or mesenteric lymph nodes upon Ag encounter and subsequently home to the lamina propria (LP) where they mediate effector functions. However, whether GALT and/or mesenteric lymph nodes are required for intestinal Th17 differentiation as well as how microbiota containing SFB regulate Ag-specific intestinal Th17 cells remain poorly defined. In this study, we observed that naive CD4+ T cells were abundant in the intestinal LP prior to weaning and that the accumulation of Th17 cells in response to microbiota containing SFB occurred in the absence of lymphotoxin-dependent lymphoid structures and the spleen. Furthermore, the differentiation of intestinal Th17 cells in the presence of microbiota containing SFB was dependent on MHC class II expression by CD11c+ cells. Lastly, the differentiation of Ag-specific Th17 cells required both the presence of cognate Ag and microbiota containing SFB. These findings suggest that microbiota containing SFB create an intestinal milieu that may induce Ag-specific Th17 differentiation against food and/or bacterial Ags directly in the intestinal LP.
Membrane Association of the CD3ε Signaling Domain Is Required for Optimal T Cell Development and Function
Authors: Bettini Matthew L. , Guy Clifford , Dash Pradyot , Vignali Kate M. , Hamm David E. , Dobbins Jessica , Gagnon Etienne , Thomas Paul G. , Wucherpfennig Kai W. , Vignali Dario A. A.
Published: June 2014

The TCR:CD3 complex transduces signals that are critical for optimal T cell development and adaptive immunity. In resting T cells, the CD3ε cytoplasmic tail associates with the plasma membrane via a proximal basic-rich stretch (BRS). In this study, we show that mice lacking a functional CD3ε-BRS exhibited substantial reductions in thymic cellularity and limited CD4–CD8– double-negative (DN) 3 to DN4 thymocyte transition, because of enhanced DN4 TCR signaling resulting in increased cell death and TCR downregulation in all subsequent populations. Furthermore, positive, but not negative, T cell selection was affected in mice lacking a functional CD3ε-BRS, which led to limited peripheral T cell function and substantially reduced responsiveness to influenza infection. Collectively, these results indicate that membrane association of the CD3ε signaling domain is required for optimal thymocyte development and peripheral T cell function.
NK Cell Responses to Simian Immunodeficiency Virus Vaginal Exposure in Naive and Vaccinated Rhesus Macaques
Authors: Shang Liang , Smith Anthony J. , Duan Lijie , Perkey Katherine E. , Qu Lucy , Wietgrefe Stephen , Zupancic Mary , Southern Peter J. , Masek-Hammerman Katherine , Reeves R. Keith , Johnson R. Paul , Haase Ashley T.
Published: June 2014

NK cell responses to HIV/SIV infection have been well studied in acute and chronic infected patients/monkeys, but little is known about NK cells during viral transmission, particularly in mucosal tissues. In this article, we report a systematic study of NK cell responses to high-dose vaginal exposure to SIVmac251 in the rhesus macaque female reproductive tract (FRT). Small numbers of NK cells were recruited into the FRT mucosa following vaginal inoculation. The influx of mucosal NK cells preceded local virus replication and peaked at 1 wk and, thus, was in an appropriate time frame to control an expanding population of infected cells at the portal of entry. However, NK cells were greatly outnumbered by recruited target cells that fuel local virus expansion and were spatially dissociated from SIV RNA+ cells at the major site of expansion of infected founder populations in the transition zone and adjoining endocervix. The number of NK cells in the FRT mucosa decreased rapidly in the second week, while the number of SIV RNA+ cells in the FRT reached its peak. Mucosal NK cells produced IFN-γ and MIP-1α/CCL3 but lacked several markers of activation and cytotoxicity, and this was correlated with inoculum-induced upregulation of the inhibitory ligand HLA-E and downregulation of the activating receptor CD122/IL-2Rβ. Examination of SIVΔnef-vaccinated monkeys suggested that recruitment of NK cells to the genital mucosa was not involved in vaccine-induced protection from vaginal challenge. In summary, our results suggest that NK cells play, at most, a limited role in defenses in the FRT against vaginal challenge.
Cutting Edge: Vitamin D Regulates Lipid Metabolism in Mycobacterium tuberculosis Infection
Authors: Salamon Hugh , Bruiners Natalie , Lakehal Karim , Shi Lanbo , Ravi Janani , Yamaguchi Ken D. , Pine Richard , Gennaro Maria Laura
Published: June 2014

Vitamin D has long been linked to resistance to tuberculosis, an infectious respiratory disease that is increasingly hard to treat because of multidrug resistance. Previous work established that vitamin D induces macrophage antimicrobial functions against Mycobacterium tuberculosis. In this article, we report a novel, metabolic role for vitamin D in tuberculosis identified through integrated transcriptome and mechanistic studies. Transcriptome analysis revealed an association between vitamin D receptor (VDR) and lipid metabolism in human tuberculosis and infected macrophages. Vitamin D treatment of infected macrophages abrogated infection-induced accumulation of lipid droplets, which are required for intracellular M. tuberculosis growth. Additional transcriptomics results showed that vitamin D downregulates the proadipogenic peroxisome proliferator–activated receptor γ (PPARγ) in infected macrophages. PPARγ agonists reversed the antiadipogenic and the antimicrobial effects of VDR, indicating a link between VDR and PPARγ signaling in regulating both vitamin D functions. These findings suggest the potential for host-based, adjunct antituberculosis therapy targeting lipid metabolism.
Assessing the contributions of private health facilities in a pioneer private-public partnership in childhood immunization in Nigeria
Authors: Oluoha Chukwuemeka , Umeh Chukwuemeka , Ahaneku Hycienth
Published: June 2014

The vision of Nigeria’s immunization program is to reach and sustain routine immunization coverage of greater than 90% for all vaccines by 2020. In order to achieve this, Abia state embarked on a unique private-public partnership (PPP) between private health facilities and the Abia state ministry of health. The aim of this partnership was to collaborate with private health facilities to provide free childhood immunization services in the state - the first of its kind in Nigeria. This is a retrospective study of the 2011 Abia state, Nigeria monthly immunization data. In the 4 local governments operating the PPP, 45% (79/175) of the health facilities that offered immunization services in 2011 were private health facilities and 55% (96/175) were public health facilities. However, 21% of the immunization services took place in private health facilities while 79% took place in public health facilities. Private health facilities were shown to have a modest contribution to immunization in the 4 local governments involved in the PPP. Efforts should be made to expand PPP in immunization nationally to improve immunization services in Nigeria.
Equipping lay facilitators to support emotionally wounded children in Africa by means of healing communities
Authors: Coetsee Dirk , Grobbelaar Jan
Published: June 2014

Many children in Africa are emotionally wounded by circumstances and experiences not supporting their overall well-being and healthy development, and are in need of effective support. It seems that the church’s educational ministry and pastoral care based on individualistic pastoral practices do not address this need effectively. Beginning with an orientation to the problem, the article then focused on the development of lay facilitators for healing communities as an alternative way of ministering to children who experience emotional suffering. With reference to an illustrative narrative of a camp with deprived children, some elements contributing to the success of the camp were highlighted and linked to the effective functioning of healing communities. Thereafter the process used to equip lay people to facilitate such healing communities was described. The article concluded with challenges to the church in Africa to develop a new ministry to serve emotionally wounded children. In Afrika is daar talle emosioneel gekweste kinders wie se omstandighede en ervarings nie tot hulle welsyn en gesonde ontwikkeling bydra nie. Hierdie kinders het ’n intense behoefte aan genesing. Dit wil egter voorkom of die kerk se opvoedkundig-georiënteerde bediening aan kinders en die individualistiese pastorale praktyk nie daarin slaag om effektief aan hierdie behoefte te voldoen nie. Nadat daar oorsigtelik na die probleem gekyk is, fokus die artikel op die ontwikkeling van ongekwalifiseerde lidmate as fasiliteerders in genesende gemeenskappe as ’n alternatiewe benadering om emosioneel gekweste kinders te bedien. Met verwysing na ’n illustratiewe uitbeelding van ’n kamp vir emosioneel gekweste kinders, word sommige elemente wat tot die sukses van die kamp bygedra het, uitgelig. Hierdie elemente word dan aan die effektiewe funksionering van genesende gemeenskappe verbind. Daarna word die opleidingsproses vir fasiliteerders van sulke groepe bespreek. Die artikel sluit af deur die kerk in Afrika tot ’n nuwe bedieningspraktyk uit te daag.
African Primary Care Research: Qualitative data analysis and writing results
Authors: Mabuza Langalibalele H. , Govender Indiran , Ogunbanjo Gboyega A. , Mash Bob
Published: June 2014

This article is part of a series on African primary care research and gives practical guidance on qualitative data analysis and the presentation of qualitative findings. After an overview of qualitative methods and analytical approaches, the article focuses particularly on content analysis, using the framework method as an example. The steps of familiarisation, creating a thematic index, indexing, charting, interpretation and confirmation are described. Key concepts with regard to establishing the quality and trustworthiness of data analysis are described. Finally, an approach to the presentation of qualitative findings is given.