Effect of Perylene as Electron Acceptor and poly(tetrabromo-p-phenylene Diselenide) as “Buffer Layer” on Heterojunction Solar Cells Performances

Summary : Perylene derivatives, that behave as liquid crystal and might be used as electron acceptors, and poly(tetrabromo-p-phenylenediselenide) (PTBrPDSe) were synthesized with the purpose of using the polymer as buffer layer in solar cells. It was demonstrated that perylene compounds of N,N′-diheptyl-3,4,9,10-perylentetracarboxyldiimide (PTCDI-C7) and N,N′-diundecyl-3,4,9,10-perylentetracarboxyldiimide (PTCDI-C11) enabled obtaining photovoltaic effect when coupled with copper phthalocyanine (CuPc). The power conversion efficiency of the cells prepared from these perylenes is similar, whatever the x value. However this efficiency is smaller than the one achieved when the couple CuPc/C₆₀ (fullerene) is used. More precisely, the best efficiency was obtained when a PTBrPDSe/Au buffer layer is introduced between the ITO anode and the CuPc. It was established that the presence of the thin PTBrPDSe layer allows improving the shunt resistance and consequently the cells performance.     

Study of free convective boundary layer of isothermal lateral surface of axisymmetrical horizontal body

Approximate analytical solution of simplified Navier–Stokes and Fourier–Kirchhoff equations describing free convective heat transfer from isothermal surface has been presented. It is supposed that the surface has the horizontal axis of symmetry and its axial cross-section lateral boundary is a concave function. The equation for the boundary layer thickness is derived for typical for natural convection assumptions. The most important are that the convective fluid flow is stationary and the normal to the surface component of velocity is negligibly small in comparison with the tangential one. The theoretical results are verified by two characteristic cases of the revolution surfaces namely for horizontal conic and vertical round plate. Both limits of presented solution coincide with known formulas.     

Existence of nonlinear boundary layer to the Boltzmann equation with reverse reflection boundary condition

Many physical models have boundaries. When the Boltzmann equation is used to study a physical problem with boundary, there usually exists a layer of width of the order of the Knudsen number along the boundary. Hence, the research on the boundary layer problem is important both in mathematics and physics. Based on the previous work, in this paper, we consider the existence of boundary layer solution to the Boltzmann equation for hard sphere model with positive Mach number. The boundary condition is imposed on incoming particles of reverse reflection type, and the solution is assumed to approach to a global Maxwellian in the far field. Similar to the problem with Dirichlet boundary condition studied in [S. Ukai, T. Yang, S.H. Yu, Nonlinear boundary layers of the Boltzmann equation: I. Existence, Comm. Math. Phys. 3 (2003) 373-393], the existence of a solution is shown to depend on the Mach number of the far field Maxwellian. Moreover, there is an implicit solvability condition on the boundary data. According to the solvability condition, the co-dimension of the boundary data related to the number of the positive characteristic speeds is obtained.     

Robust semiglobally practical stabilization for nonlinear singularly perturbed systems

In this work, the problem of semiglobally practical stabilization is considered for nonlinear singularly perturbed systems with unknown parameters. The composite Lyapunov function for the full systems is established by both that of the slow subsystem and the boundary layer system. A state feedback control law for the linear part of the slow subsystem and boundary layer system is proposed which renders the whole closed-loop system semiglobally stable. The upper bound expression of ε$\epsilon$ is given to obtain the condition of asymptotic stability for the system. A simulation example is given to demonstrate the effectiveness and feasibility of the controller.     

Influence of temperature-dependent viscosity and thermal radiation on MHD forced convection over a non-isothermal wedge

An analysis has been carried out to study heat transfer characteristics of an incompressible Newtonian electrically conducting and heat generating/absorbing fluid having temperature-dependent viscosity over a non-isothermal wedge in the presence of thermal radiation. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The wedge surface is assumed to be permeable so as to allow for possible wall suction or injection. The effects of viscous dissipation, Joule heating, stress work and thermal radiation are included in the model. The governing differential equations are derived and transformed using a non-similarity transformation. The transformed equations are solved numerically by applying a fifth-order Runge-Kutta-Fehlberg scheme with shooting technique. Favorable comparisons with previously published work on various special cases of the problem are obtained. Numerical results for the velocity and temperature profiles for a prescribed magnetic field parameter as well as the development of the local skin-friction coefficient and local Nusselt number with the magnetic field and radiation parameters are presented graphically and in tabulated form to elucidate the influence of the various physical parameters.     

Monte Carlo simulation of boundary layer transition

A statistical method for simulating a boundary layer transition flow is proposed as based on experimental data on the kinematics and dynamics of turbulent spots (Emmons spots) on a flat plate placed in an incompressible fluid. The method determines intermittency with allowance for overlapping spots, which makes it possible to determine the forces on the plate surface and the flow field near the transition region if the mean streamwise velocity field in a developed turbulent boundary layer is known as a function of the Reynolds number. In contrast to multiparameter transition models, this approach avoids the use of nonphysical parameter values.     

使用PML技术求解Helmholtz方程的几种区域分解算法

1引言 在科学与工程计算中,时谐声波和电磁波散射现象的模拟常归结为Helmholtz方程的数值求解,这是一个重要而具有挑战性的问题.     

A PML Method for Electromagnetic Scattering from Two-dimensional Overfilled Cavities

In this paper, we consider electromagnetic scattering problems for two-dimensional overfilled cavities. A half ringy absorbing perfectly matched layer （PML） is introduced to enclose the cavity, and the PML formulations for both TM and TE polarizations are presented. Existence, uniqueness and convergence of the PML solutions are considered. Numerical experiments demonstrate that the PML method is efficient and accurate for solving cavity scattering problems.     

Assembly-controlled biocompatible interface on a microchip: strategy to highly efficient proteolysis

A biocompatible interface was constructed on a microchip by using the layer-by-layer (LBL) assembly of charged polysaccharides incorporating proteases for highly efficient proteolysis. The controlled assembly of natural polyelectrolytes and the enzyme-adsorption step were monitored by using a quartz-crystal microbalance and atomic force microscopy (AFM). Such a multilayer-assembled membrane provides a biocompatible interconnected network with high enzyme-loading capacity. The maximum digestion rate of the adsorbed trypsin in a microchannel was significantly accelerated to 1600 mM min(-1) microg(-1), compared with the tryptic digestion in solution. Based on the Langmuir isotherm model, the thermodynamic constant of adsorption K was calculated to be 1.6 x 10(5) M(-1) and the maximum adsorption loading Gammamax was 3.6 x 10(-6) mol m(-2), 30 times more than a monolayer of trypsin on the native surface. The tunable interface containing trypsin was employed to construct a microchip reactor for digestion of femtomoles of proteins and the produced peptides were analyzed by MALDI-TOF mass spectroscopy. The efficient on-chip proteolysis was obtained within a few seconds, and the identification of biological samples was feasible.     

Synthesis of size-controlled acid-resistant hybrid calcium carbonate microparticles as templates for fabricating "micelles-enhanced" polyelectrolyte capsules by the LBL technique

Size-controlled, low-dispersed calcium carbonate microparticles were synthesized in the presence of the amphiphilic block copolymer polystyrene-b-poly(acrylic acid) (PS-b-PAA) by modulating the concentration of block copolymer in the reactive system. This type of hybrid microparticles have acid-resistant properties. By investigating the aggregation behaviors of PS-b-PAA micelles by transmission electron microscopy (TEM), the mechanism of hybrid calcium carbonate formation illustrated that the block copolymer served not only as "pseudonuclei" for the growth of calcium carbonate nanocrystals, but also forms the supramicelle congeries, a spherical framework, as templates for calcium carbonate nanocrystal growth into hybrid CaCO(3) particles. Moreover, this pilot study shows that the hybrid microparticle is a novel candidate as a template for fabricating multilayer polyelectrolyte capsules, in which the block copolymer is retained within the capsule interior after core removal under soft conditions. This not only facilitates the encapsulation of special materials, but also provides "micelles-enhanced" polyelectrolyte capsules.