Displaying publications 1 - 20 of 477 in total

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  1. Lee HW, Azid IH
    Sensors (Basel), 2009;9(9):7481-97.
    PMID: 22400004 DOI: 10.3390/s90907481
    In this study, a hybridized neuro-genetic optimization methodology realized by embedding numerical simulations trained artificial neural networks (ANN) into a genetic algorithm (GA) is used to optimize the flow rectification efficiency of the diffuser element for a valveless diaphragm micropump application. A higher efficiency ratio of the diffuser element consequently yields a higher flow rate for the micropump. For that purpose, optimization of the diffuser element is essential to determine the maximum pumping rate that the micropump is able to generate. Numerical simulations are initially carried out using CoventorWare® to analyze the effects of varying parameters such as diffuser angle, Reynolds number and aspect ratio on the volumetric flow rate of the micropump. A limited range of simulation results will then be used to train the neural network via back-propagation algorithm and optimization process commence subsequently by embedding the trained ANN results as a fitness function into GA. The objective of the optimization is to maximize the efficiency ratio of the diffuser element for the range of parameters investigated. The optimized efficiency ratio obtained from the neuro-genetic optimization is 1.38, which is higher than any of the maximum efficiency ratio attained from the overall parametric studies, establishing the superiority of the optimization method.
    Matched MeSH terms: Physical Phenomena
  2. Lum CY, Ong LH, ÄŒepic M
    Sains Malaysiana, 2011;40:1123-1127.
    The transition of orthogonal smectic A (SmA) phase to the tilted phases, upon lowering the temperature, is explored with a discrete phenomenological model and the phase diagrams are presented. The results show that the transition of SmA to uniplanar structures can be affected by the effect of chirality. The areas showing the uniplanar phase in the phase diagrams diminish with the increase in effect of chirality.
    Matched MeSH terms: Physical Phenomena
  3. Agus Kartono, Mustafa Mamat
    Sains Malaysiana, 2013;42:333-340.
    Differential cross sections for excitation to the n=2 states of atomic helium by electrons were computed for incident energies in the range from 30 to 50 eV. The n=2 states excitation cross sections are calculated with the use of closecoupling expansion with a non-orthogonal Laguerre-L2 basis function. The present status of agreement between theory and experiment for excitation of the ground-state was quite satisfactory.
    Matched MeSH terms: Physical Phenomena
  4. Soon, C.K., Zaini, Z., Mohd Ujang, A., Nagapan, S., Abdullah, A.H., Hasmori, M.F., et al.
    MyJurnal
    The building sector consumes about forty percent of world energy, making energy efficiency in existing buildings an important issue. This study has been undertaken to investigate energy consumption of a building that has been redesigned to incorporate energy efficient features. It was found that the introduction of energy efficient features has helped to achieve savings up to 46% of the total spent on energy particularly based on electricity bills.
    Matched MeSH terms: Physical Phenomena
  5. Wu Diyi, Zulaiha Ali Othman, Suhaila Zainudin, Ayman Srour
    MyJurnal
    The water flow-like algorithm (WFA) is a relatively new metaheuristic algorithm, which has shown good solution for the Travelling Salesman Problem (TSP) and is comparable to state of the art results. The basic WFA for TSP uses a 2-opt searching method to decide a water flow splitting decision. Previous algorithms, such as the Ant Colony System for the TSP, has shown that using k-opt (k>2) improves the solution, but increases its complexity exponentially. Therefore, this paper aims to present the performance of the WFA-TSP using 3-opt and 4-opt, respectively, compare them with the basic WFA-TSP using 2-opt and the state of the art algorithms. The algorithms are evaluated using 16 benchmarks TSP datasets. The experimental results show that the proposed WFA-TSP-4opt outperforms in solution quality compare with others, due to its capacity of more exploration and less convergence.
    Matched MeSH terms: Physical Phenomena
  6. Guan Y, Vossen A, Adachi I, Adamczyk K, Ahn JK, Aihara H, et al.
    Phys Rev Lett, 2019 Feb 01;122(4):042001.
    PMID: 30768311 DOI: 10.1103/PhysRevLett.122.042001
    We report the first observation of the spontaneous polarization of Λ and Λ[over ¯] hyperons transverse to the production plane in e^{+}e^{-} annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive Λ/Λ[over ¯] production, we also report results with subtracted feed-down contributions from Σ^{0} and charm. This measurement uses a dataset of 800.4  fb^{-1} collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the Λ/Λ[over ¯] hyperon.
    Matched MeSH terms: Physical Phenomena
  7. Liang SN, Lan BL
    PLoS One, 2012;7(5):e36430.
    PMID: 22606259 DOI: 10.1371/journal.pone.0036430
    The newtonian and special-relativistic statistical predictions for the mean, standard deviation and probability density function of the position and momentum are compared for the periodically-delta-kicked particle at low speed. Contrary to expectation, we find that the statistical predictions, which are calculated from the same parameters and initial gaussian ensemble of trajectories, do not always agree if the initial ensemble is sufficiently well-localized in phase space. Moreover, the breakdown of agreement is very fast if the trajectories in the ensemble are chaotic, but very slow if the trajectories in the ensemble are non-chaotic. The breakdown of agreement implies that special-relativistic mechanics must be used, instead of the standard practice of using newtonian mechanics, to correctly calculate the statistical predictions for the dynamics of a low-speed system.
    Matched MeSH terms: Physical Phenomena*
  8. Yeo CI, Halim SN, Ng SW, Tan SL, Zukerman-Schpector J, Ferreira MA, et al.
    Chem Commun (Camb), 2014 Jun 7;50(45):5984-6.
    PMID: 24763907 DOI: 10.1039/c4cc02040e
    Evidence for C-H···π(CuCl···HNCS) interactions, i.e. C-H···π(quasi-chelate ring) where a six-membered quasi-chelate ring is closed by an N-H···Cl hydrogen bond, is presented based on crystal structure analyses of (Ph3P)2Cu[ROC(=S)N(H)Ph]Cl. Similar intramolecular interactions are identified in related literature structures. Calculations suggest that the energy of attraction provided by such interactions approximates 3.5 kcal mol(-1).
    Matched MeSH terms: Physical Phenomena
  9. Najib N, Bachok N, Arifin NM, Ishak A
    Sci Rep, 2014;4:4178.
    PMID: 24569547 DOI: 10.1038/srep04178
    This paper is about the stagnation point flow and mass transfer with chemical reaction past a stretching/shrinking cylinder. The governing partial differential equations in cylindrical form are transformed into ordinary differential equations by a similarity transformation. The transformed equations are solved numerically using a shooting method. Results for the skin friction coefficient, Schmidt number, velocity profiles as well as concentration profiles are presented for different values of the governing parameters. Effects of the curvature parameter, stretching/shrinking parameter and Schmidt number on the flow and mass transfer characteristics are examined. The study indicates that dual solutions exist for the shrinking cylinder but for the stretching cylinder, the solution is unique. It is observed that the surface shear stress and the mass transfer rate at the surface increase as the curvature parameter increases.
    Matched MeSH terms: Physical Phenomena
  10. Marufuzzaman M, Reaz MB, Rahman LF, Chang TG
    ScientificWorldJournal, 2014;2014:709635.
    PMID: 24574913 DOI: 10.1155/2014/709635
    High-speed current controller for vector controlled permanent magnet synchronous motor (PMSM) is presented. The controller is developed based on modular design for faster calculation and uses fixed-point proportional-integral (PI) method for improved accuracy. Current dq controller is usually implemented in digital signal processor (DSP) based computer. However, DSP based solutions are reaching their physical limits, which are few microseconds. Besides, digital solutions suffer from high implementation cost. In this research, the overall controller is realizing in field programmable gate array (FPGA). FPGA implementation of the overall controlling algorithm will certainly trim down the execution time significantly to guarantee the steadiness of the motor. Agilent 16821A Logic Analyzer is employed to validate the result of the implemented design in FPGA. Experimental results indicate that the proposed current dq PI controller needs only 50 ns of execution time in 40 MHz clock, which is the lowest computational cycle for the era.
    Matched MeSH terms: Physical Phenomena
  11. Khorramian K, Maleki S, Shariati M, Ramli Sulong NH
    PLoS One, 2015;10(12):e0144288.
    PMID: 26642193 DOI: 10.1371/journal.pone.0144288
    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.
    Matched MeSH terms: Physical Phenomena
  12. Shukri AA, Visintin P, Oehlers DJ, Jumaat MZ
    Materials (Basel), 2016 Apr 22;9(4).
    PMID: 28773430 DOI: 10.3390/ma9040305
    Describing the moment rotation (M/θ) behavior of reinforced concrete (RC) hinges is essential in predicting the behavior of RC structures under severe loadings, such as under cyclic earthquake motions and blast loading. The behavior of RC hinges is defined by localized slip or partial interaction (PI) behaviors in both the tension and compression region. In the tension region, slip between the reinforcement and the concrete defines crack spacing, crack opening and closing, and tension stiffening. While in the compression region, slip along concrete to concrete interfaces defines the formation and failure of concrete softening wedges. Being strain-based, commonly-applied analysis techniques, such as the moment curvature approach, cannot directly simulate these PI behaviors because they are localized and displacement based. Therefore, strain-based approaches must resort to empirical factors to define behaviors, such as tension stiffening and concrete softening hinge lengths. In this paper, a displacement-based segmental moment rotation approach, which directly simulates the partial interaction behaviors in both compression and tension, is developed for predicting the M/θ response of an RC beam hinge under cyclic loading. Significantly, in order to develop the segmental approach, a partial interaction model to predict the tension stiffening load slip relationship between the reinforcement and the concrete is developed.
    Matched MeSH terms: Physical Phenomena
  13. Nazatulsyima Mohd Yazid, Kim, Gaik Tay, Wei, King Tiong, Yaan, Yee Choy, Azila Md Sudin, Chee, Tiong Ong
    MATEMATIKA, 2017;33(1):35-41.
    MyJurnal
    In this paper, the application of the method of lines (MOL) to the Forced
    Korteweg-de Vries-Burgers equation with variable coefficient (FKdVB) is presented.
    The MOL is a powerful technique for solving partial differential equations by typically
    using finite-difference approximations for the spatial derivatives and ordinary differential
    equations (ODEs) for the time derivative. The MOL approach of the FKdVB
    equation leads to a system of ODEs. The solution of the system of ODEs is obtained
    by applying the Fourth-Order Runge-Kutta (RK4) method. The numerical solution
    obtained is then compared with its progressive wave solution in order to show the
    accuracy of the MOL method.
    Matched MeSH terms: Physical Phenomena
  14. Shaker M. Khudher, Ishak Aris, Nashiren F. Mailah, Sahbudin, R.K.Z.
    MyJurnal
    This paper discusses the harmonic analysis of the AC-to-DC uncontrolled converters commonly used in electric vehicles charging station. The aim of this paper is to model and simulate different rectifier models in addition to explaining the differences in input current harmonics, the total Harmonic Distortion (THD) as well as the power factor (pf). The converter configurations include single-phase bridge, 6-pulse and 12-pulse rectifier circuits. The single phase is normally used for electric scooter charging, while three-phase converters can be used for both electric bus and car charging. The circuit configurations of the rectifiers were modelled and simulated using Matlab R2014a to achieve the objective of the study. The results revealed that the THD levels were extremely high which is unacceptable if the system is connected to the utility grid.
    Matched MeSH terms: Physical Phenomena
  15. Belousov R, Cohen EGD, Rondoni L
    Phys Rev E, 2017 Aug;96(2-1):022125.
    PMID: 28950465 DOI: 10.1103/PhysRevE.96.022125
    The present paper is based on a recent success of the second-order stochastic fluctuation theory in describing time autocorrelations of equilibrium and nonequilibrium physical systems. In particular, it was shown to yield values of the related deterministic parameters of the Langevin equation for a Couette flow in a microscopic molecular dynamics model of a simple fluid. In this paper we find all the remaining constants of the stochastic dynamics, which then is simulated numerically and compared directly with the original physical system. By using these data, we study in detail the accuracy and precision of a second-order Langevin model for nonequilibrium physical systems theoretically and computationally. We find an intriguing relation between an applied external force and cumulants of the resulting flow fluctuations. This is characterized by a linear dependence of an athermal cumulant ratio, an apposite quantity introduced here. In addition, we discuss how the order of a given Langevin dynamics can be raised systematically by introducing colored noise.
    Matched MeSH terms: Physical Phenomena
  16. Sarker MR, Mohamed A, Mohamed R
    Micromachines, 2016 Sep 23;7(10).
    PMID: 30404344 DOI: 10.3390/mi7100171
    This paper presents a new method for a vibration-based piezoelectric energy harvesting system using a backtracking search algorithm (BSA)-based proportional-integral (PI) voltage controller. This technique eliminates the exhaustive conventional trial-and-error procedure for obtaining optimized parameter values of proportional gain (Kp), and integral gain (Ki) for PI voltage controllers. The generated estimate values of Kp and Ki are executed in the PI voltage controller that is developed through the BSA optimization technique. In this study, mean absolute error (MAE) is used as an objective function to minimize output error for a piezoelectric energy harvesting system (PEHS). The model for the PEHS is designed and analyzed using the BSA optimization technique. The BSA-based PI voltage controller of the PEHS produces a significant improvement in minimizing the output error of the converter and a robust, regulated pulse-width modulation (PWM) signal to convert a MOSFET switch, with the best response in terms of rise time and settling time under various load conditions.
    Matched MeSH terms: Physical Phenomena
  17. Farooq J, Mushtaq M, Munir S, Ramzan M, Chung JD, Farooq U
    Sci Rep, 2018 Sep 03;8(1):13137.
    PMID: 30177724 DOI: 10.1038/s41598-018-31538-8
    This study deals with the steady laminar slip flow of an incompressible Newtonian fluid in a non-uniform permeable channel under the influence of transverse magnetic field. The reabsorption through the wall is accounted for by considering flux as a function of downstream distance. The non-linear coupled partial differential equations of motion are first transformed into a single fourth order partial differential equation and then solved analytically using Adomain decomposition method. Effects of pertinent parameters on different flow properties are discussed by plotting graphs. Results reveal that magnetic field considerably influences the behavior of flow.
    Matched MeSH terms: Physical Phenomena
  18. Belousov R, Cohen EG, Rondoni L
    Phys Rev E, 2016 Sep;94(3-1):032127.
    PMID: 27739763
    In this paper, we generalize the theory of Brownian motion and the Onsager-Machlup theory of fluctuations for spatially symmetric systems to equilibrium and nonequilibrium steady-state systems with a preferred spatial direction, due to an external force. To do this, we extend the Langevin equation to include a bias, which is introduced by an external force and alters the Gaussian structure of the system's fluctuations. In addition, by solving this extended equation, we provide a physical interpretation for the statistical properties of the fluctuations in these systems. Connections of the extended Langevin equation with the theory of active Brownian motion are discussed as well.
    Matched MeSH terms: Physical Phenomena
  19. Hooi, M.H., Tiong, W. K., Tay, K. G., Chiew,K. L., Sze, S. N.
    MATEMATIKA, 2018;34(2):333-350.
    MyJurnal
    In this paper, we look at the propagation of internal solitary waves over three
    different types of slowly varying region, i.e. a slowly increasing slope, a smooth bump and
    a parabolic mound in a two-layer fluid flow. The appropriate mathematical model for this
    problem is the variable-coefficient extended Korteweg-de Vries equation. The governing
    equation is then solved numerically using the method of lines. Our numerical simulations
    show that the internal solitary waves deforms adiabatically on the slowly increasing slope.
    At the same time, a trailing shelf is generated as the internal solitary wave propagates
    over the slope, which would then decompose into secondary solitary waves or a wavetrain.
    On the other hand, when internal solitary waves propagate over a smooth bump or a
    parabolic mound, a trailing shelf of negative polarity would be generated as the results of
    the interaction of the internal solitary wave with the decreasing slope of the bump or the
    parabolic mound. The secondary solitary waves is observed to be climbing the negative
    trailing shelf.
    Matched MeSH terms: Physical Phenomena
  20. Sirunyan AM, Tumasyan A, Adam W, Ambrogi F, Asilar E, Bergauer T, et al.
    Eur Phys J C Part Fields, 2018;78(2):140.
    PMID: 31265001 DOI: 10.1140/epjc/s10052-018-5607-5
    A search for standard model production of four top quarks (

    t

    t
    ¯

    t

    t
    ¯


    ) is reported using events containing at least three leptons (

    e
    ,
    μ

    ) or a same-sign lepton pair. The events are produced in proton-proton collisions at a center-of-mass energy of 13


    TeV

    at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9



    fb

    -
    1



    . Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the

    t

    t
    ¯

    t

    t
    ¯


    cross section is measured to be

    16
    .

    9

    -
    11.4


    +
    13.8






    fb

    , in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level.
    Matched MeSH terms: Physical Phenomena
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