The control of the Casimir force between two parallel plates can be achieved through inducing the optical Kerr effect of a nonlinear material. By considering a two-plate system which consists of a dispersive metamaterial and a nonlinear material, we show that the Casimir force between the plates can be switched between attractive and repulsive Casimir force by varying the intensity of a laser pulse. The switching sensitivity increases as the separation between plate decreases, thus providing new possibilities of controlling Casimir force for nanoelectromechanical systems.
Two new records of moray eels (Muraenidae), Gymnothorax margaritophorus Bleeker, 1864 and Strophidon sathete (Hamilton 1822), are reported for Malaysia. They are represented by two specimens each, all collected from Sabah waters. The present study also provides the current taxonomic and distributional information of the Malaysian moray eels. To date, there are 33 species belonging to six genera of the Muraenidae in Malaysian waters based on the published records.
Stochastic differential equations play a prominent role in many application areas including finance, biology and epidemiology. By incorporating random elements to ordinary differential equation system, a system of stochastic differential equations (SDEs) arises. This leads to a more complex insight of the physical phenomena than their deterministic counterpart. However, most of the SDEs do not have an analytical solution where numerical method is the best way to resolve this problem. Recently, much work had been done in applying numerical methods for solving SDEs. A very general class of Stochastic Runge-Kutta, (SRK) had been studied and 2-stage SRK with order convergence of 1.0 and 4-stage SRK with order convergence of 1.5 were discussed. In this study, we compared the performance of Euler-Maruyama, 2-stage SRK and 4-stage SRK in approximating the strong solutions of stochastic logistic model which describe the cell growth of C. acetobutylicum P262. The MS-stability functions of these schemes were calculated and regions of MS-stability are given. We also perform the comparison for the performance of these methods based on their global errors.
A steady two-dimensional magnetohydrodynamic (MHD) stagnation-point flow of a viscous and electrically conducting fluid over a permeable shrinking sheet has been studied. The governing partial differential equations are reduced to the nonlinear ordinary differential equations by a similarity transformation. The resulting differential equations are then solved numerically using an implicit finite difference method. It is found that the solutions are non-unique for weak magnetic field, strong suction and large velocity ratio between free stream velocity and wall shrinking velocity.
We give details about how a surface plasmons with phase singularities can be produced when a Bessel beam light is totally reflected internally at the planar surface of a dielectric on which an infinitesimally thin film has been deposited. The characteristic property of such a light is the exponential decay with distance in a vacuum which can basically provide a two-dimensional surface plasmons with phase singularities with attractive enhancements. Such a phenomenon is governable by altering the incident angle and the order of the Bessel beam.
The historical and future storm surge climate over the South China Sea Sunda Shelf was derived using a barotropic two dimensional model. The atmospheric forcings were obtained from the UKMO regional climate modeling system, PRECIS (Providing Regional Climates for Impacts Studies), forced at the boundary by the ECHAM4 simulation output under the SRES A2 emission experiment. In general, the model simulates historical sea surface elevation characteristics satisfactory although there is a substantial underestimation for the sea level elevation at local scales. The climate change analysis suggests that the storm surge extreme over the Sunda Shelf is expected to increase along the coastal area of the Gulf of Thailand and east coast of Peninsular Malaysia in the future (2071-2100). The projected increment is averagely ~9% over the Sunda Shelf region by the end of the 21st century corresponding to about 5% stronger wind speed as compare to the baseline period of 1961-1990.
The paper reconsiders the problem of the mixed convection boundary layer flow near the lower stagnation point of a horizontal circular cylinder with a second order slip velocity model and a constant surface heat flux studied recently by RoKa et al. (2013). The ordinary (similarity) differential equations are solved numerically using the function bvp4c from Matlab for different values of the governing parameters. It is found that the similarity equations have two branches, upper and lower branch solutions, in a certain range of the mixed convection parameters. A stability analysis has been performed to show that the upper branch solutions are stable and physically realizable, while the lower branch solutions are not stable and therefore, not physically possible. This stability analysis is different by that presented by RoKa et al. (2013), who have presented a time-dependent analysis to determine the stability of the solution branches.
The statistical characteristics of wind direction that was recorded at maximum wind speed in Peninsular Malaysia for two monsoons from 1999 to 2008 for seven stations were analyzed in this study. Modeled by von Mises distribution, the change in parameters values namely mean direction and concentration parameter was measured. Statistical summary, graphical representations, Watson-William Test and linear-circular correlation are used in the analysis. It is found that there is a significant change in the mean direction of wind over the period of ten years for most stations in Peninsular Malaysia. However, there is a weak relationship between wind direction and wind speed. This study suggested the presence of prominent direction of wind that blows in Peninsular Malaysia by monsoon. This finding may provide useful information on giving a better understanding of the behavior of the wind in Peninsular Malaysia and the potential use of wind as an alternative source of energy.
Topological defect nucleation and boundary branching in crystal growth on a curved surface are two typical elastic instabilities driven by curvature induced stress, and have usually been discussed separately in the past. In this work they are simultaneously considered during crystal growth on a sphere. Phase diagrams with respect to sphere radius, size, edge energy and stiffness of the crystal for the equilibrium crystal morphologies are achieved by theoretical analysis and validated by Brownian dynamics simulations. The simulation results further demonstrate the detail of morphological evolution governed by these two different stress relaxation modes. Topological defect nucleation and boundary branching not only compete with each other but also coexist in a range of combinations of factors. Clarification of the interaction mechanism provides a better understanding of various curved crystal morphologies for their potential applications.
We have designed new derivatives of naphtha [2 ,1-b:6 ,5-13V difuran as DPNDF-CN1 and DPNDF-CN2. The molecular structures of DPNDF, its derivatives DPNDF-CN1 and DPNDF-CN2 have been optimized at the ground (So) and first excited (S1) states using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), respectively. Then the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (Lumos), photoluminescence properties, electron affinities (EELS), reorganization energies (.1.$) and ionization potentials (iPs) have been investigated. The balanced A(h) and A(e) showed that DPNDF, DPNDF-CN1 and DPNDF-CN2 would be better charge transport materials for both hole and electron. The effect of attached acceptors on the geometrical parameters, electronic, optical and charge transfer properties have also been investigated.
IAEA in its publication year 2000 has recommended a worksheet for the determination of absorbed dose to water in an electron beam. We evaluated the worksheet via an absorbed dose to water determination work at a local radiotherapy center using a 12 MeV electron beam. We found that if several modifications are made, this IAEA worksheet will become more user-friendly and could facilitate and fasten the process of quality assurance audit. The modifications are given and discussed.
[IAEA dalam penerbitannya tahun 2000 telah mengesyorkan satu helaian kerja untuk menentukan dos terserap kepada air dalam alur electron. Helaian kerja ini dinilai melalui satu kerja penentuan dos terserap kepada air di satu Pusat radioterapi tempatan menggunakan satu alur electron 12 MeV. Sekiranya beberapa pengubahsuai dibuat, helaian kerja IAEA ini akan menjadi lebih mesra pengguna dan dapat mempermudahkan dan mempercepatkan lagi proses audit jaminan kualiti. Pengubahsuaian ini diberikan dan dibincangkan].
The magnetohydrodynamic (MHD) boundary-layer flow and heat transfer due to a shrinking sheet in a porous medium is considered for the first time. The Navier-Stokes equations and the heat equation are reduced to two nonlinear ordinary differential equations via similarity transformations. The transformed equations are solved by a semi-analytic method. The effects of the suction and porosity parameters, the Prandtl and Hartmann numbers on the skin friction, heat transfer rate, velocity and temperature profiles are discussed and presented, respectively.
The paper is aimed at studying fluid flow heat transfer in the axisymmetric boundary layer flow of a viscous incompressible fluid, along the axial direction of a vertical stationary isothermal cylinder in presence of uniform free stream with momentum slip. The equations governing the flow i.e. continuity, momentum and energy equation are transformed into non-similar boundary layer equations and are solved numerically employing asymptotic series method with Shanks transformation. The numerical scheme involves the Runge-Kutta fourth order scheme along with the shooting technique. The flow is analyzed for both assisting and opposing buoyancy and the effect of different parameters on fluid velocity, temperature distribution, heat transfer and shear stress parameters is presented graphically.
This paper investigates the application of visco-hyperelastic model to soft rubberlike material, that is gluten. Gluten is a major protein in wheat flour dough (a mixture of flour and water) which exists as long network fibers and undergo large deformation under uniaxial tension and compression. The visco-hyperelastic model is represented by a combination of the viscoelastic Prony series and the hyperelastic extended tube model. Calibration of the visco-hyperelastic model to gluten tests result suggests that gluten can be modelled as a finite viscoelastic material.
The unsteady mixed convection boundary layer flow near the forward stagnation point of a two-dimensional symmetric body prescribed by a uniform heat flux rate is studied in this paper. The main aim of the investigation is to identify situations in which dual solutions for the steady-state flow can be determined when the flow is opposing. It is also shown that there is a smooth transition from the unsteady initial flow (short time) to the final steady state flow (large time).
In this study, the numerical solution of stagnation point flow over a stretching surface, generated by Newtonian heating in which the heat transfer from the surface is proportional to the local surface temperature is considered. The transformed boundary layer equations are solved numerically using the shooting method. Numerical solutions are obtained for the local heat transfer coefficient, the surface temperature and the temperature profiles. The features of the flow and heat transfer characteristics for various values of the Prandtl number, stretching parameter and conjugate parameter are analyzed and discussed.
Groundwater irrigation is one of the alternative methods to irrigate the paddy crops beside surface water. The use of shallow tube well for paddy irrigation is able to overcome water scarcity especially during dry season and off planting season in Malaysia. The performance of a shallow tube well was evaluated based on well efficiency and pump efficiency. The study was conducted at Seberang Perak Integrated Agricultural Development Area (Seberang Perak IADA). In this study, on-off automatic water controller was installed in the field and connected to the pump system which gave the command to the pump to irrigate the field during pre-saturation and normal growth plantation period. Water level inside the pumping well and cultivation plot was observed and recorded by the water level transducers. The result of the study showed that the pumping well is moderately productive with the well efficiency between 91 and 94%. The submersible pump efficiency was 87.5%. The potential yield of the pumping well was 450 m3day-1 and it was enough and sufficient to irrigate 1 ha of paddy field.
The extinction of Br2 molecules in gas state is measured for different wavelengths of incident light in interval of 370 - 570 nm by method of gas spectroscopy. The measurement is made on the basis of Franck-Condon's principle, under which a transition to a more excited state is done without changing the intercore distance (in further text, R). The graph of energy dependence on extinction is drawn. On the graph are recognized two Gausses slopes and their separation (deconvolution) is done. The complete Gausses functions are determined on graph. The method of mirror symmetry is applied on Gausses slopes of extinction and symmetrical extinction values (Es) are obtained. Borders of Franck-Condon's area are determined from ground state of Linear Harmonic Oscillator (LH0). Tables of dependence on R and the excitation energy are given. On the basis of these tables are drawn potential curves of electron energy E(R) in excited electronic states of Br2 molecules as functions of R in Franck-Condon's area.
This note describes a method for the determination of the peak-to-total ratio, P/T versus gamma-ray energy of range 59.54-1836.03 keV of a HPGe detector. Results show that this ratio decreases with energy. To check the validity of these results, two approaches of results comparison, namely with the ratio reported by Cesana and Terrani in year 1989 and with the shape of total efficiency reported by Debertin and Helmer in year 1988 were taken. lt is shown that this method gives satisfactory results since the obtained values of P/T and the shape of the total efficiency curve were in good agreement with the reported works. The precautional step that need to be taken when dealing with energy 59.54 keV 241Am source and the reason for taking the total efficiency as the evaluation tool are given.
The effects of HVA-2 on radiation-induced cross-linkings in 60/40 natural rubber/ linear low density polyethylene (NR/LLDPE) blends was studied. NR/LLDPE was irradiated by using a 3.0 MeV electron beam machine with doses ranging from 0 to 250 kGy. Results showed that under the irradiation employed, the blends NR/LLDPE were cross-linked by the electron beam irradiation. The presence of HVA-2 in the blends caused the optimum dose to decrease and the blends to exhibit higher tensile properties. Further, within the dose range studied, the degradation caused by electron beam irradiation was found to be minimal. The optimized processing conditions were 120oC, 50 rpm rotor speed and 13 min processing time. The gel content, tensile strength, elongation at break, hardness and impact test studies were used to follow the irradiation-induced cross-linkings in the blend. For blends of 60/40 NR/LLDPE with 2.0 phr HVA-2, the optimum tensile strength and dose, were 19 MPa and 100 kGy, respectively. Blends of 60/40 NR/LLDPE without HVA-2, the optimum tensile strength and dose were 17.2 MPa and 200 kGy, respectively.