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PublicationCylindrical shape slug heat conduction numerical analysis using copper material( 2013)High power light emitting diodes have the edge over the conventional lighting system in terms of efficiency, low energy consumption and long operational lifetime. Nevertheless, the heat dissipation issue of the high power LED bottlenecks the fulfilment of the potential possessed by the LED. The heat dissipation of LED is evaluated in terms of junction temperature. In this work, simulation was carried out to evaluate the heat dissipation of a single chip LED attached to a copper based cylindrical heat slug. The junction temperature and the stress of the LED chip were scrutinized under natural convection condition with applied input power of 0.1 W and 1 W. Ansys version 11 was utilized for the simulation. For input power of 1 W, the maximum junction temperature and Von Mises of 117.44°C and 229.21MPa was exhibited by the GaN based chip.
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PublicationCross-Talk in Mechanomyographic Signals from the Forearm Muscles during Sub-Maximal to Maximal Isometric Grip Force( 2014)Purpose This study aimed: i) to examine the relationship between the magnitude of cross-talk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles with the sub-maximal to maximal isometric grip force, and with the anthropometric parameters of the forearm, and ii) to quantify the distribution of the cross-talk in the MMG signal to determine if it appears due to the signal component of intramuscular pressure waves produced by the muscle fibers geometrical changes or due to the limb tremor. Methods Twenty, right-handed healthy men (mean ± SD: age = 26.7±3.83 y; height = 174.47±6.3 cm; mass = 72.79±14.36 kg) performed isometric muscle actions in 20% increment from 20% to 100% of the maximum voluntary isometric contraction (MVIC). During each muscle action, MMG signals generated by each muscle were detected using three separate accelerometers. The peak cross-correlations were used to quantify the cross-talk between two muscles. Results The magnitude of cross-talk in the MMG signals among the muscle groups ranged from, R2(x, y) = 2.45-62.28%. Linear regression analysis showed that the magnitude of cross-talk increased linearly (r2 = 0.857-0.90) with the levels of grip force for all the muscle groups. The amount of cross-talk showed weak positive and negative correlations (r2 = 0.016-0.216) with the circumference and length of the forearm respectively, between the muscles at 100% MVIC. The cross-talk values significantly differed among the MMG signals due to: limb tremor (MMGTF), slow firing motor unit fibers (MMGSF) and fast firing motor unit fibers (MMGFF) between the muscles at 100% MVIC (p<0.05, η2 = 0.47-0.80). Significance The results of this study may be used to improve our understanding of the mechanics of the forearm muscles during different levels of the grip force.
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PublicationEffects of pH and concentration on the capability of E. coli and S. epidermidis with bentonite clay as biosorbent for the removal of Copper, Nickel and Lead from polluted water( 2017)This paper discusses the effects of pH and concentration on the capability of E. coli ATCC29522 and S. epidermidis RP62A biofilm with bentonite in removing divalent copper, nickel and lead from wastewater. Batch adsorption study at laboratory scale was utilized to evaluate the potential use of bacterial biomass (E. coli ATCC29522 and S. epidermidis RP62A) aided with geosynthetic clay (bentonite) for the removal of Cu2+, Ni2+and Pb2+. Results revealed that removal of Cu2+, Ni2+and Pb2+ by both types of organisms supported with bentonite were high in the first 4 hours of the experiment. This illustrates that the binding site on that particular time was abundant. Hence, the removal rate was evident at high concentration depicting the line adsorption equilibrium. It also revealed that S. epidermidis RP62A supported with bentonite had the highest affinity to Copper and Lead with Qm = 277.7 mg/g and 5.0075 mg/g, respectively. While E. coli ATCC 29522 had the highest affinity to Nickel (Qm= 58.82 mg/g). Hence, the sorption of Cu2+, Ni2+and Pb2+ onto E. coli ATCC29522 and S. epidermidis RP62A biofilm supported with bentonite clay occurred through monolayer chemisorption on the homogeneous surface of E. coli ATCC29522 and S. epidermidis RP62A biofilm with bentonite clay. Batch kinetics studies revealed that the sorption of Cu2+, Ni2+and Pb2+ onto E. coli ATCC29522 and S. epidermidis RP62A biofilm supported with bentonite clay was well described by a pseudo-second-order equation model of type 1 (R2 = 0.9999), which implies that chemisorption is the rate limiting step.
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PublicationDetermination of drying kinetics and sorption isotherm of black pepper (Piper Nigrum)( 2017)In the present study of food products, determination of the drying characteristics of black pepper using an oven is not yet completely established. This study aimed to determine the drying kinetics and sorption isotherm of black pepper using a convective oven at 30°C, 40°C and 50°C. The data gathered in this study were used to fit in selected mathematical models for drying kinetics and sorption isotherm. Among these models, the Midilli model (MR=0.5338exp(0.7273t-0.0551)+-0.0005t for 30°C, MR=0.5814exp(0.6293t-0.0764)+ -0.0008t for 40°C and MR=0.3187exp(1.1777t-0.0466)+ -0.0011t for 50°C) was the best fit to explain the moisture transfer in black pepper, while the GAB Model (m/0.1302=((0.1906)( 0.7811)aw)/(1-(0.7811)aw)[1-(0.7811)aw+(0.1906)( 0.7811)aw])) was for the equilibrium moisture content and water activity relationship. After evaluating the data, the drying characteristics of black pepper at 40°C yielded better results than 30°C and 50°C. XLSTAT and ANOVA Add-in of Microsoft Excel was the software used to compute for the necessary values in the assessment of the mathematical models for this study.
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PublicationMechanomyogram for Muscle Function Assessment: A Review( 2013)Background: Mechanomyography (MMG) has been extensively applied in clinical and experimental practice to examine muscle characteristics including muscle function (MF), prosthesis and/or switch control, signal processing, physiological exercise, and medical rehabilitation. Despite several existing MMG studies of MF, there has not yet been a review of these. This study aimed to determine the current status on the use of MMG in measuring the conditions of MFs. Methodology/Principal Findings: Five electronic databases were extensively searched for potentially eligible studies published between 2003 and 2012. Two authors independently assessed selected articles using an MS-Word based form created for this review. Several domains (name of muscle, study type, sensor type, subject’s types, muscle contraction, measured parameters, frequency range, hardware and software, signal processing and statistical analysis, results, applications, authors’ conclusions and recommendations for future work) were extracted for further analysis. From a total of 2184 citations 119 were selected for full-text evaluation and 36 studies of MFs were identified. The systematic results find sufficient evidence that MMG may be used for assessing muscle fatigue, strength, and balance. This review also provides reason to believe that MMG may be used to examine muscle actions during movements and for monitoring muscle activities under various types of exercise paradigms. Conclusions/Significance: Overall judging from the increasing number of articles in recent years, this review reports sufficient evidence that MMG is increasingly being used in different aspects of MF. Thus, MMG may be applied as a useful tool to examine diverse conditions of muscle activity. However, the existing studies which examined MMG for MFs were confined to a small sample size of healthy population. Therefore, future work is needed to investigate MMG, in examining MFs between a sufficient number of healthy subjects and neuromuscular patients.