V掺杂ZnO透明导电薄膜研究

本文分别采用磁控溅射技术与基于密度泛函理论的平面波赝势方法两种方式, 对高价态差元素V掺杂ZnO薄膜进行研究. 实验研究结果表明: V的掺入并未改变ZnO的生长方式, 所制备的薄膜都呈(002)择优生长; 随着衬底温度增加, VZO薄膜的结晶质量逐步改善, 当衬底温度超过280 ℃时薄膜的结晶质量恶化; 在280 ℃时获得的VZO薄膜电阻率最低3.8×10^-3 Ω·m, 500-2000 nm平均透过率高于85%. 理论模拟结果表明: V以替位形式掺入ZnO六角纤锌矿晶格结构中, 费米能级进入导带, 材料表现出n 型半导体的特性, 导电电子主要由V 3d及O 2p电子轨道提供. 理论计算结果与实验结果的一致性, 表明VZO薄膜具有作为高效Si基薄膜太阳电池透明导电薄膜的应用潜力.     

On the existence of solutions for the Schrödinger-Poisson equations

In this paper, we are concerned with the system of Schrödinger-Poisson equations

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Maximum principle and existence of solutions for non necessarily cooperative systems involving Schrödinger operators

In this paper, we obtain the necessary and sufficient conditions for having the maximum principle and existence of positive solutions for some cooperative systems involving Schrödinger operators defined on unbounded domains. Then, we deduce the existence of solutions for semi-linear systems. Finally we discuss the generalized maximum principle (gf _q -positivity) for non cooperative systems.     

Large Deviations of Queues Sharing a Randomly Time-Varying Server

We consider a discrete-time model where multiple queues, each with its own exogenous arrival process, are served by a server whose capacity varies randomly and asynchronously with respect to different queues. This model is primarily motivated by the problem of efficient scheduling of transmissions of multiple data flows sharing a wireless channel. We address the following problem of controlling large deviations of the queues: find a scheduling rule, which is optimal in the sense of maximizing

Global convergence toward traveling fronts in nonlinear parabolic systems with a gradient structure

We consider nonlinear parabolic systems of the form ut=−∇V(u)+u_xx$u_t=-\mathrm{\nabla }V(u)+u_{xx}$, where u∈Rn$u\in {\mathbb{R}}^n$, n?1$n?1$, x∈R$x\in \mathbb{R}$, and the potential V   is coercive at infinity. For such systems, we prove a result of global convergence toward bistable fronts which states that invasion of a stable homogeneous equilibrium (a local minimum of the potential) necessarily occurs via a traveling front connecting to another (lower) equilibrium. This provides, for instance, a generalization of the global convergence result obtained by Fife and McLeod [P. Fife, J.B. McLeod, The approach of solutions of nonlinear diffusion equations to traveling front solutions, Arch. Rat. Mech. Anal. 65 (1977) 335–361] in the case n=1$n=1$. The proof is based purely on energy methods, it does not make use of comparison principles, which do not hold any more when n>1$n>1$.     

No Lacuna and No Vicious Regress: A Reply to Le Poidevin

In his “Space, supervenience and substantivalism”, Le Poidevin proposes a substantivalism in which space is discrete, implying that there are unmediated spatial relations between neighboring primitive points. This proposition is motivated by his concern that relationism suffers from an explanatory lacuna and that substantivalism gives rise to a vicious regress. Le Poidevin implicitly requires that the relationist be committed to the “only x and y” principle regarding spatial relations. It is not obvious that the relationist is committed to this principle in such a context. An additional motivation for Le Poidevin's argument, that space should be considered to be discrete, is that he believes that substantivalists are committed to a vicious regress. I show that the regress is in fact not of the vicious variety. These two main arguments show that Le Poidevin's suggestion that we drop the density postulate for space is unnecessary.

Free-solvent model shows osmotic pressure is the dominant factor in limiting flux during protein ultrafiltration

In protein ultrafiltration (UF), the limiting flux phenomenon has been generally considered a consequence of the presence of membrane fouling or the perceived formation of a cake/gel layer that develops at high operating pressures. Subsequently, numerous theoretical models on gel/cake physics have been made to address how these factors can result in limiting flux. In a paradigm shift, the present article reestablishes the significance of osmotic pressure by examining its contribution to limiting flux in the framework of the recently developed free solvent osmotic pressure model. The resulting free-solvent-based flux model (FSB) uses the Kedem–Katchalsky model, film theory and the free solvent representation for osmotic pressure in its development. Single protein tangential-flow diafiltration experiments (30 kDa MWCO CRC membranes) were also conducted using ovalbumin (OVA, 45 kDa), bovine serum albumin (BSA, 69 kDa), and immuno-gamma globulin (IgG, 155 kDa) in moderate NaCl buffered solutions at pH 4.5, 5.4, 7 and 7.4. The membrane was preconditioned to minimize membrane fouling development during the experimental procedure. The pressure was randomly selected and flux and sieving were determined. The experimental results clearly demonstrated that the limiting flux phenomenon is not dominated by membrane fouling and the FSB model theoretically illustrates that osmotic pressure is the primary factor in limiting flux during UF. The FSB model provides excellent agreement with the experimental results while producing realistic protein wall concentrations. In addition, the pH dependence of the limiting flux is shown to correlate to the pH dependency of the specific protein diffusion coefficient.     

First principle MD study on the structural and electronic properties of liquid and amorphous NI81B19 and NI80P20 alloy

Atomic and electronic structures of liquid and amorphous Ni₈₁B₁₉ and Ni₈₀P₂₀ alloys were simulated by ab initio molecular dynamics. Pair correlation function, bond pair analysis, electronic population analysis, and density of states were calculated. It was found that amorphous Ni₈₁B₁₉ and Ni₈₀P₂₀ alloys can be prepared by rapid quenching, and their structures are similar to those of liquid alloys. Bond pair analysis indicated that the environment of each atom in Ni₈₁B₁₉ system is dominated by icosahedral and distorted icosahedral inherent structures; however, in Ni₈₀P₂₀ system, the tetrahedral order is preponderant. Strong interactions occur between the d‐electrons of Ni and the p‐electrons of B (or P), which leads to the covalent interactions between Ni and B (or P) atoms. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008