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51.
Anuar Mat Safar Syed Alwee Aljunid Amir Razif Arief Junita Nordin Naufal Saad 《Optical Review》2012,19(1):20-24
The use of minimal multiple access interference (MAI) in code design is investigated. Applying a projection and mapping techniques,
a code that has a zero cross correlation (ZCC) between users in optical code division multiple access (OCDMA) is presented
in this paper. The system is based on an incoherent light source—LED, spectral amplitude coding (SAC), and direct detection
techniques at the receiver. Using power spectral density (PSD) function and Gaussian approximation, we obtain the signal-to-noise
ratio (SNR) and the bit-error rate (BER) to measure the code performance. Making a comparison with other existing codes, e.g.,
Hadamard, MFH and MDW codes, we show that our code performs better at BER 10−9 in terms of number of simultaneous users. We also demonstrate the comparison between the theoretical and simulation analyses,
where the results are close to one another. 相似文献
52.
The solution to the unsteady mixed convection boundary layer flow and heat transfer problem due to a stretching vertical surface
is presented in this paper. The unsteadiness in the flow and temperature fields is caused by the time-dependent of the stretching
velocity and the surface temperature. The governing partial differential equations with three independent variables are first
transformed into ordinary differential equations, before they are solved numerically by a finite-difference scheme. The effects
of the unsteadiness parameter, buoyancy parameter and Prandtl number on the flow and heat transfer characteristics are thoroughly
examined. Both assisting and opposing buoyant flows are considered. It is observed that for assisting flow, the solutions
exist for all values of buoyancy parameter, whereas for opposing flow, they exist only if the magnitude of the buoyancy parameter
is small. Comparison with known results for steady-state flow is excellent. 相似文献
53.
The steady magnetohydrodynamic (MHD) mixed convection flow towards a vertical permeable surface with prescribed heat flux is investigated. The governing partial differential equations are transformed into a system of ordinary differential equations, which is then solved numerically by a finite-difference method. The features of the flow and heat transfer characteristics for different values of the governing parameters are analysed and discussed. Both assisting and opposing flows are considered. It is found that dual solutions exist for the assisting flow, besides the solutions usually reported in the literature for the opposing flow. 相似文献
54.
The mixed convection boundary layer flow through a stable stratified porous medium bounded by a vertical surface is investigated. The external velocity and the surface temperature are assumed to vary as xm, where x is measured from the leading edge of the vertical surface and m is a constant. Numerical solutions for the governing Darcy and energy equations are obtained. The results indicate that the thermal stratification significantly affects the surface shear stress as well as the surface heat transfer, besides delays the boundary layer separation. 相似文献
55.
E. P. Zhil’tsova M. R. Ibatullina S. S. Lukashenko M. P. Kutyreva M. M. Anuar V. I. Kovalenko L. Ya. Zakharova 《Russian Journal of General Chemistry》2017,87(11):2620-2626
Novel organometallic surfactants were synthesized from monoquaternized 1,4-diazabicyclo[2.2.2]-octanes of varied hydrophobicity [Alk = C n H2n+1, n = 14, 18] and lanthanum nitrates. The spectral, micelleforming, and adsorption properties of the synthesized compounds were studied by IR, 1Н NMR and electronic spectroscopy, tensiometry, conductometry, and potentiometry. The critical micelle concentrations, counterionic micellar binding constants, and adsorption parameters at the water–air interface were determined and compared with the respective characteristics of the ligands and conventional amphiphiles. 相似文献
56.
The complexation reactions between the macrocyclic ionophore, p-isopropylcalix[6]arene and Cs+ cation were studied in dimethylsulfoxide-acetonitrile (DMSO-AN) binary non-aqueous solvents at different temperatures using a conductometry method. The conductance data show that the stoichiometry of the (p-isopropylcalix[6]-arene·Cs)+ complex in all binary mixed solvents is 1:1. The stability of the complexes is affected by the composition of the binary solvent media and a non-linear behavior was observed for changes of log K(f) of the complex versus the composition of the binary mixed solvents. The thermodynamic parameters (DH°(c) and DS°(c)) for formation of (p-isopropyl-calix[6]arene·Cs)+ complex were obtained from temperature dependence of the stability constant and the obtained results show that the (p-isopropylcalix[6]arene·Cs)+ complex is enthalpy destabilized, but entropy stabilized, and the values of the mentioned parameters are affected strongly by the nature and composition of the binary mixed solvents. 相似文献
57.
Radiation effects on the thermal boundary layer flow over a moving plate with convective boundary condition 总被引:2,自引:0,他引:2
The steady laminar boundary layer flow over a moving plate in a moving fluid with convective surface boundary condition and
in the presence of thermal radiation is investigated in this paper. Under certain conditions, the present problem reduces
to the classical Blasius and Sakiadis problems. The effects of radiation and convective parameters on the thermal field are
thoroughly examined and discussed. Dual solutions are found to exist when the plate and the fluid move in the opposite directions. 相似文献
58.
Masoumi HR Kassim A Basri M Abdullah DK Haron MJ 《Molecules (Basel, Switzerland)》2011,16(7):5538-5549
An Artificial Neural Network (ANN) based on the Quick Propagation (QP) algorithm was used in conjunction with an experimental design to optimize the lipase-catalyzed reaction conditions for the preparation of a triethanolamine (TEA)-based esterquat cationic surfactant. Using the best performing ANN, the optimum conditions predicted were an enzyme amount of 4.77 w/w%, reaction time of 24 h, reaction temperature of 61.9 °C, substrate (oleic acid: triethanolamine) molar ratio of 1:1 mole and agitation speed of 480 r.p.m. The relative deviation percentage under these conditions was less than 4%. The optimized method was successfully applied to the synthesis of the TEA-based esterquat cationic surfactant at a 2,000 mL scale. This method represents a more flexible and convenient means for optimizing enzymatic reaction using ANN than has been previously reported by conventional methods. 相似文献
59.
A Taguchi robust design method with an L? orthogonal array was implemented to optimize experimental conditions for the biosynthesis of triethanolamine (TEA)-based esterquat cationic surfactants using an enzymatic reaction method. The esterification reaction conversion% was considered as the response. Enzyme amount, reaction time, reaction temperature and molar ratio of substrates, [oleic acid: triethanolamine (OA:TEA)] were chosen as main parameters. As a result of the Taguchi analysis in this study, the molar ratio of substrates was found to be the most influential parameter on the esterification reaction conversion%. The amount of enzyme in the reaction had also a significant effect on reaction conversion%. 相似文献
60.