Showing papers by "Azli Yahya published in 2014"
TL;DR: This study suggests direct tyrosinase inhibition by chloroform extracts of Phaleria macrocarpa is suggested, which is antioxidant independent.
Abstract: Background: The ethyl acetate and chloroform extracts of stems, leaves and fruits of Phaleria macrocarpa were screened for their antioxidant capacity and tyrosinase inhibition properties.
Material and Method: The total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric-ion reducing power (FRAP) were used to evaluate their antioxidant capacity. Tyrosinase inhibition effect was measured using mushroom tyrosinase inhibition assay.
Result: Ethyl acetate extract of P. macrocarpa’s stem exhibited highest total phenolic content, DPPH free radical scavenging and ferric reducing power. Meanwhile, chloroform extracts of leaves and fruits demonstrated potent anti-tyrosinase activities as compared to a well-known tyrosinase inhibitor, kojic acid.
Conclusion: Since chloroform extracts of leaves and fruits have low antioxidant capacities, the tyrosinase inhibition effect observed are antioxidant independent. This study suggests direct tyrosinase inhibition by chloroform extracts of Phaleria macrocarpa.
10 citations
TL;DR: In this article, a transistor type pulse power generator circuit is used to generate sparks through the gap between the electrode and the workpiece to obtain the output waveform similar to the ideal EDM waveform.
Abstract: 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.
8 citations
TL;DR: In this paper, a model of pulsed electrical discharge machining using RL circuit is presented, where the circuit schematic of transistor pulse power generator has been designed using electrical model in Matlab Simulink software to identify the profile of voltage and current.
Abstract: This article presents a model of pulsed Electrical Discharge Machining (EDM) using RL circuit. There are several mathematical models have been successfully developed based on the initial, ignition and discharge phase of current and voltage gap. According to these models, the circuit schematic of transistor pulse power generator has been designed using electrical model in Matlab Simulink software to identify the profile of voltage and current during machining process. Then, the simulation results are compared with the experimental results.
7 citations
15 Jul 2014
TL;DR: Investigation have been conducted using electrical discharge process (die-sinker) to obtain new surface in metal hip implant, which place pit on the surface of curvature cup, which will prolong the life span of the implant due to lubrication activities in hip tribology.
Abstract: In this study, investigations have been conducted using electrical discharge process (die-sinker) to obtain new surface in metal hip implant, which place pit on the surface of curvature cup. A circular array of pit in circle shape was successfully created on the surface of acetabular. There are 8 pits that have been embedded on the surface area of the acetabular by each diameter machine and the depths are 1.1 mm and 0.5 mm respectively. This new surface improvement will prolong the life span of the implant due to lubrication activities in hip tribology.
7 citations
01 Dec 2014
TL;DR: The development of this prototype is the first for thalassemia and the finding of this study will assist future developers embarking on designing blood related disease management applications which share a similar process flow and data requirements.
Abstract: Thalassemia is an inherited blood disorder that requires lifelong disease management and therefore poses a pecuniary challenge in public health management in Malaysia. Constant monitoring of patients throughout their life requires novel adaptation of new technologies to enhance the effectiveness and success of the complex disease treatment regimen. In this paper we present a prototype mobile health (mHealth) application that will assist patients, care workers and medical practitioners in administering thalassemia disease management. The ubiquity and proximity of smartphones as a personal device will allow it to take up an assistive role in the management process. The user requirement analysis revealed that not all of the disease's information is available for stakeholders are suitable for the application and the alert function that works both ways between the patient and doctor is desirable. Operational limitations such as patient confidentiality, minor (underage) patients and analogous legacy registry has to be taken into account. The development of this prototype is the first for thalassemia and the finding of this study will assist future developers embarking on designing blood related disease management applications which share a similar process flow and data requirements.
6 citations
TL;DR: In this article, the authors reviewed and summarized some previous development of EDM power generator and their effectiveness and showed that the power supply and pulse generator are two important parts in EDM Power Generator.
Abstract: Electrical Discharge Machining (EDM) is a non-conventional manufacturing process of removing materials. The uniqueness of EDM process is the removal of the unwanted materials without direct contact between the electrode and workpiece. EDM power generator provides power source of EDM system. It supplies voltage and current to produce spark erosion. Power supply and pulse generator are two important parts in EDM power generator. By choosing the proper power supply and pulse generator to the application, a great result for Material Removal Rate (MRR) can be achieved. Efficiency of EDM power generator depends on the configurations of power supply used. This study reviews and summarizes some previous development of EDM power generator and their effectiveness.
5 citations
TL;DR: In this article, different rain attenuation prediction models were investigated and their performances compared and validation results clearly suggested that the Breakpoint attenuation model produced better results when compared with other models of interest.
Abstract: The non-uniformity of rainfall in both the horizontal and vertical directions makes the estimation of slant path attenuation complex. At frequencies above 10 GHz, the effects of attenuation and noise induced by rain are quite significant. One year satellite attenuation data were sourced from Malaysia East Asia Satellite at Ku frequency band; using ASTRO beacon signals to monitor and measure the slant path rain rate and attenuation at Universiti Teknologi Malaysia, Skudai. Four years’ one minute rain rate ground data at 0.01% of time exceeded were collected using rain gauge. The attenuation exceeded for other percentages of the time was obtained using statistical methods. Different rain attenuation prediction models were investigated and their performances compared. The validation results clearly suggested that the Breakpoint attenuation prediction model produced better results when compared with other models of interest. DOI: http://dx.doi.org/10.11591/ijece.v4i5.6583
5 citations
TL;DR: In this article, synthetic polymer polycaprolactone (PCL) was blended together with natural polymer gelatin where both of them have different properties and the result obtained also showed that by increasing the overall polymeric concentration of PCL/gelatin, average fiber diameter decreases.
Abstract: 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.
4 citations
TL;DR: In this paper, an ultracapacitor bank was added to the main power supply circuit for EDM machines to improve the gap voltage and gap current, and the control feedback of this research was designed to make sure that the current on DC bus is maintained at current setting during the machining processes.
Abstract: Electrical Discharge Machining (EDM) is a advanced machine that can control electrical spark to erode metal on the workpiece. In manufacturing, EDM is used on hard material parts that are extremely difficult to machine by conventional machining processes. 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 and current pulses between the electrode and workpiece to generate sparks through the gap. To obtain the optimum metarial removal rate (MRR), a good alternative is to improve the gap voltage and gap current. A proposed solution to these issue is combining ultracapacitor bank to the main power supply circuit for EDM machines. The control feedback of this research is designed to make sure that the current on DC bus is maintained at current setting during the machining processes.
3 citations
TL;DR: In this paper, a computer-aided workpiece positioning system for biomedical application was developed for machining micropits on spherical surface of hip implant using electrical discharge machining (EDM).
Abstract: This study aims to develop dedicated computer-aided workpiece positioning system for biomedical application. The application is for machining micropits on spherical surface of hip implant using electrical discharge machining (EDM). New spherical positioning system has been designed and realized for further development. A computer is used as a main control unit to control the positioning system and modular servo motors with tuneable PID controller are utilized by the system. This paper explains the configuration of the implemented system and tuning process to optimize the system performance.
3 citations
TL;DR: In this article, an indirect measurement of surface position is carried out by implementing voltage average gap model, and Simulink models have been done to simulate the dynamic behavior of EDM system.
Abstract: Electrical discharge machining (EDM) is a nonconventional milling in which holes or shape can be created without any contact between electrode and work piece during the material removal process. Throughout the machining process a series of stochastic sparks are produced when the gap between electrode and work piece is very narrow just about 10 to 50 microns. Controlling this gap in micro dimension not only depends on electrode position but also on work piece surface. So a combination of PID controller and EDM process is used to monitor the gap. In this study an indirect measurement of surface position is carried out by implementing voltage average gap model. And Simulink models have been done to simulate the dynamic behavior of EDM system.
TL;DR: In this article, two discharge models are simulated and compared, and the simulation results show that there are behavior differences between these models, which is very important on the outcome of research.
Abstract: 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.
20 Aug 2014
TL;DR: In this paper, a model of pulses in electrical discharge machining (EDM) system is presented, which is based on the initial, ignition and discharge phase of current and voltage gap.
Abstract: This article presents a model of pulses inElectrical Discharge Machining (EDM) system There areseveral mathematical models have been successfully developedbased on the initial, ignition and discharge phase of currentand voltage gap According to these models, the circuitschematic of transistor pulse power generator has beendesigned using electrical model in Matlab Simulink software toidentify the profile of voltage and current during machiningprocess Then, the simulation results are compared withexperimental results
TL;DR: In this paper, a flyback converter with a PWM controller is presented. Butt et al. presented a current mode Pulse Width Modulation (PWM) controlled Flyback converter using UC3842 for Electrical Discharge Machining current generator control circuit.
Abstract: This paper presents a current mode Pulse Width Modulation (PWM) controlled Flyback converter using UC3842 for Electrical Discharge Machining current generator control circuit. Circuit simplicity and high efficiency can be achieved by a Flyback converter with current mode PWM controller. The behaviors of the system's operation is analyzed and discussed by varying the load resistance. Matlab sofware is used to simulate the Flyback converter where a prototype has been built and tested to verify it's performance. DOI: http://dx.doi.org/10.11591/ijpeds.v5i2.6680
Journal Article•
TL;DR: In this paper, a feed-forward neural network is used to predict the material removal rate of an electrical discharge machine process, which is performed in order to obtain a lower variance between the actual and predicted material removal rates.
DOI•
20 Aug 2014TL;DR: This paper presents a current mode Pulse Width Modulation (PWM) controlled Flyback converter using UC3842 for Electrical Discharge Machining current generator control circuit.
Abstract: This paper presents a current mode Pulse Width Modulation (PWM) controlled Flyback converter using UC3842 for Electrical Discharge Machining current generator control circuit. Circuit simplicity and high efficiency can be achieved by a Flyback converter with current mode PWM controller. The behaviors of the system's operation is analyzed and discussed by varying the load resistance. Matlab software is used to simulate the Flyback converter where a prototype has been built and tested to verify it's performance.