Criteria for improving the properties of ZnGeAs2 solar cells

We explore the potential utility of the II‐IV‐V semiconductor ZnGeAs₂ as the absorber material in solar cells. As‐deposited ZnGeAs₂ films prepared by pulsed laser deposition are amorphous because of the limited substrate temperature that can be used without the rapid loss of volatile Zn and As. Thermal processing above 450 °C results in crystallization and improved electrical properties with hole mobilities as high as 58 cm²/V s. The annealed films were used to fabricate p‐type ZnGeAs₂: n‐type CdS cells on SnO₂‐buffered borosilicate glass substrates in the so‐called superstrate geometry. Light‐induced currents of up to ~2 mA/cm² and open‐circuit voltages of up to 470 mV were observed using backside illumination, indicating that these nascent devices hold potential for realizing high performance solar cells from earth‐abundant elements. The performance of the devices fabricated to‐date is degraded by conduction through shorts resulting from the presence of micron‐sized pinholes in the absorber layer. Copyright © 2012 John Wiley & Sons, Ltd.     

一类变换半群的若干结果

对保两个等价关系变换半群的某些性质进行了研究,利用格林关系及幂等元正则性,讨论了这类半群的某些性质,得出了保两个等价关系变换半群是左零半群、右零半群的充要条件。     

正则语言的一个特征

Myhill-Nerode定理利用等价关系描述了正则语言的一个重要特征,它是有限自动机理论中的一个经典、优美的结果。为了将Myhill-Nerode定理推广到更一般的情形,引入了有限自动机M上的状态转移半群和Σ*上的M-半群,讨论了其若干性质。在此基础上,将Myhill-Nerode定理中的等价关系一般化,给出了正则语言的一个新的特征定理,Myhill-Nerode定理成为该定理的一个推论。讨论了正则语言的最一般的特征,提出了有待进一步研究的问题。     

弱富水软岩水-沙混合型突水机制与防治技术——以上海庙矿区为例

近年来我国西北侏罗纪煤田弱富水软岩水-沙混合型间歇式突水事故多发,短时水(沙)量大,缺少有效的防范技术措施,严重威胁矿井安全生产。为揭示其形成机制以便于制定相应的防范措施,以内蒙古上海庙矿业新上海一号煤矿为研究对象,室内测试了岩石力学强度、软化系数等参数,井下实测了围岩松动圈,综合判定为典型的软岩地层;正交偏光镜下显示砂岩成熟度低,黏土质矿物胶结;水理性试验表明砂岩颗粒间泥质胶结物易产生溶蚀现象,能够形成固-液双相混合物,在水动力下具有流沙属性;泥岩极易吸水膨胀、泥化。根据含水层水位和地表岩移长期观测结果,推定低位覆岩内和高位覆岩内均可以产生离层裂隙,且离层裂隙具有汇集水源功能。将111084工作面突水溃沙过程中含水层水位历时曲线与水量历时曲线叠合考察,突水量与突水含水层水位升降变化之间有明显的相关性。初时突水量大、水位下降幅度也大;水量在趋于衰减过程中出现几次跃升,含水层水位在趋于回升过程中出现几次相应的跃降;跃升(跃降)的幅度梯次减小;两次跳跃时间间隔梯次延长。综合以上信息,提出离层裂隙的汇水作用可以强化弱含水层短时突水强度观点,弱胶结砂岩提供了混合突水的沙源;离层水体释放过程中水动力发生强弱变化,随着离层水体释放水动力减弱,大量泥沙封堵突水通道,表现出泥沙自封堵效应。覆岩持续压缩,离层裂隙储水能力逐渐弱化,表现为突水量梯次减小;离层水补给路径逐渐扩展,表现为突水休止期梯次延长。汇水—突水—封堵—再汇水—再突水—再封堵的过程交替进行,揭示了间歇性水-沙混合型突水模式的突水机制。离层水害发生需要具备水源(富水性)、时间、空间、通道、压力等5个必要条件,强调导水裂隙突水通道的重要性。工程应用表明,顶板水预疏干可以改变含水层的富水性条件,预置导流管改变离层空间封闭性和汇水时间条件,突水通道和压力条件,可以有效避免此类事故发生,保障矿井安全生产;同时可实现无顶板淋水、采空区无涌水状态下开采,优化采场作业环境、弱化软岩劣化效应,促进矿井高效生产。     

Approximate controllability of semilinear partial functional differential systems

In this paper, we study the approximate controllability of semilinear neutral functional-differential systems and impulsive functional-differential systems with finite delay. Since the considered equations admit nonlinear terms involving spatial derivatives, the fraction power theory and α-norm is used to discuss the problem so that the established results can be applied to them. An example is provided to illustrate the application of the obtained results. This work is supported by NNSF of China (No. 10671069) and Shanghai Leading Academic Discipline Project (No. B407).     

构建多元化控制体系防治巢湖水污染

在分析巢湖水污染控制的研究现状与存在问题的基础上,指出在现有的巢湖水环境污染问题研究中基础性与系统性研究不足,科技成果转化率低,关键理论与技术问题亟待解决。提出从技术基础研究、应用技术开发和建立示范工程三个层面开展研究,构建“污染源头控制、本体释磷控制、过程削减控制、末端强化控制、管理系统控制”的巢湖水污染多元控制防治体系的建议。     

The exponential stability region of Timoshenko beam with interior delays and boundary damping

In this paper, we investigate the exponential stability of a Timoshenko beam with interior time delays and boundary damping. At first, we show that the system is well posed by the semigroup method. Next, we construct an appropriate functional to study the exponential stability. We transform the exponential stability into the solvability of inequality equations, and then by analysing the relationship between delays parameters α₁, α₂ and damping parameters β₁, β₂, we describe the (α₁, α₂)-region for which the system is exponentially stable.     

一种泛逻辑代数系统

文[3]给出了理想状态(广义相关系数h=0.5,广义自相关系数k=0.5)下泛逻辑的形式演绎系统B,证明了此系统是可靠的。该文提出理想状态下(h=k=0.5)泛逻辑学对应的代数系统-UB代数,给出它的一系列性质。证明了UB代数是一个交换剩余半群;进一步证明了U B代数与M V代数、正规FI代数是等价的。     

Optimal Control for Pennes' Bioheat Equation

The problem of Pennes' bioheat boundary control through a skin with its inner medium kept at a constant steady‐state temperature where the outer surface subjected to conductive condition is solved by different methods. Analytical and mild solutions of Pennes' boundary control problem yield a discrete optimization problem for temperature profile at the specific depth point as well as temperature profile at all points of the skin in the final time. The pointwise optimal control problem has been solved by discretized form of the unconstrained optimization problem using analytical solution for Pennes' boundary control problem. The analytical solution has been used to solve the optimal control problems via an unconstrained/constrained optimization in Methods I and II. In Method III first, Pennes' boundary control problem is solved using mild solution by strongly continuous semigroup theory. Then, nonlinear optimization problem with linear constraints is proposed to calculate the corresponding piecewise optimal control function. All methods, have been applied to a homogeneous tissue. Mathematical simulation is done to show the optimal controls for the related states when minimum effort is used.     

Approximate controllability results for non-densely defined fractional neutral differential inclusions with Hille–Yosida operators

In this paper, we mainly focused the approximate controllability results for a class of non-densely defined fractional neutral differential control systems. First, we establish a set of sufficient conditions for the approximate controllability for a class of fractional differential inclusions with infinite delay where the linear part is non-densely defined and satisfies the Hille–Yosida condition. The main techniques rely on Bohnenblust– Karlin's fixed point theorem, operator semigroups and fractional calculus. Further, we extend the result to study the approximate controllability concept with nonlocal conditions. Finally, an example is also given for the illustration of the obtained theoretical results.