Computer simulation of a-Si : H/mu c-Si : H diphasic silicon solar cells

Based on our experimental research on diphasic silicon films, the parameters such as absorption coefficient, mobility lifetime product and bandgap were estimated by means of effective-medium theory. And then computer simulation of a-Si: H/mu c-Si: H diphasic thin film solar cells was performed. It was shown that the more crystalline fraction in the diphasic silicon films, the higher short circuit density, the lower open-circuit voltage and the lower efficiency. From the spectral response, we can see that the response in long wave region was improved significantly with increasing crystalline fraction in the silicon films. Taking Lambertian back refraction into account, the diphasic silicon films with 40%-50% crystalline fraction was considered to be the best intrinsic layer for the bottom solar cell in micromorph tandem.

Computer-aided design of PV/wind hybrid system

A complete set of match calculation methods for optimum sizing of PV/wind hybrid system is presented. In this method, the more accurate and practical mathematic models for characterizing PV module, wind generator and battery are adopted; combining with hourly measured meteorologic data and load data, the performance of a PV/wind hybrid system is determined on a hourly basis; by fixing the capacity of wind generators, the whole year's LPSP (loss of power supply probability) values of PV/wind hybrid systems with different capacity of PV array and battery bank are calculated, then the trade-off curve between battery bank and PV array capacity is drawn for the given LPSP value; the optimum configuration which can meet the energy demand with the minimum cost can be found by drawing a tangent to the trade-off curve with the slope representing the relationship between cost of PV module and that of the battery. According to this match calculation method, a set of match calculation programs for optimum sizing of PV/wind hybrid systems have been developed. Applying these match calculation programs to an assumed PV/wind hybrid system to be installed at Waglan island of Hong Kong, the optimum configuration and its hourly, daily, monthly and yearly performances are given. (C) 2003 Elsevier Science Ltd. All rights reserved.

basic research in computer science and software engineering at sklcs

The State Key Laboratory of Computer Science (SKLCS) is committed to basic research in computer science and software engineering. The research topics of the laboratory include: concurrency theory, theory and algorithms for real-time systems, formal specifications based on context-free grammars, semantics of programming languages, model checking, automated reasoning, logic programming, software testing, software process improvement, middleware technology, parallel algorithms and parallel software, computer graphics and human-computer interaction. This paper describes these topics in some detail and summarizes some results obtained in recent years.

THE STUDY OF MICROSTRUCTURE IN IRON-DOPED AND SULFUR-DOPED INP CRYSTALS BY MEANS OF HREM AND COMPUTER-SIMULATION

The microstructures in iron- and sulphur-doped InP crystals were studied using both electron microscopy and electron diffraction. A modulated structure has been found in S-doped InP crystal, where the commensurate modulations corresponded to periodicities of 0.68 nm and 0.7 nm in real space and were related to the reflections of the cubic lattice in [111] and [113BAR] directions; they were indexed as q111* = 1/2(a* + b* + c*) and q113BAR* = 1/4(-a* - b* + 3c*), respectively. Single atomic layers of iron precipitate were observed, with preferred orientations along which precipitates are formed. Simulated calculations by means of the dynamical theory of electron diffraction using models for the precipitate structure were in good agreement with our experimental results. The relation between the modulated structure and the precipitates is also discussed.

基于文件规范描述的文件模糊测试

针对传统文件测试效率不高、存在功能遗漏的缺点,提出一种基于文件规范描述的文件模糊测试方法。给出基于文件规范的文件推导规则,用于描述文件中结构的组织形式、结构与结构之间的依赖关系,生成同一格式下不同类型的文件并对每类文件进行模糊测试。实验结果表明,该方法能有效找到文件处理软件的脆弱点。

基于事件的文件系统恢复技术

在现代文件系统中，用户只能访问文件和目录的当前版本，而无法查看文件和目录的改变过程。用户可能无意地或错误地对文件执行了删除或修改操作，或者执行了一段恶意脚本，导致一系列文件遭到破坏。如果能够记录文件和目录的修改过程，并且可以方便地恢复某次操作破坏的一系列文件，这对用户是相当有帮助的。本文把一个进程在其执行过程中对文件的一系列修改称为一个事件。 文件系统可以通过文件版本化技术来记录文件的修改过程。文件版本化技术包括两种：快照技术和单文件版本化技术。这两种技术都没有提供用户一种方便有效的方法来撤销一个进程对多个文件的一系列修改，无法撤消一个事件对文件的改变。所以，本文在单文件版本化技术的基础上提出了基于事件的文件系统恢复技术，并设计实现了一个具有事件恢复功能的文件系统GobackFS（Go back file system，简称GobackFS）。本文的主要贡献体现在以下几点： (1) 针对如何恢复一个进程在其运行过程中改变的一系列文件这一问题，本文提出了基于事件的文件系统恢复技术，并通过一个实例——GobackFS文件系统，给出了基于事件的文件系统恢复技术的一种设计与实现。 (2) 对用户完全透明的系统设计和实现。GobackFS文件系统透明地创建文件版本，记录文件的改变过程。在GobackFS文件系统中，如果文件以写标志打开时，创建一个新的文件版本，在文件每一次打开和关闭期间最多创建一个新版本。文件的访问权限和所有权发生变化时，创建新的文件子版本。GobackFS文件系统透明地记录改变文件的事件信息。在创建文件版本和子版本时，记录触发文件版本创建的事件信息。 (3) 提供了简单易用的使用接口。在GobackFS文件系统中，用户可以通过一条简单的命令来查看某段时间内哪些事件对文件做了更改，某个事件对哪些文件做了更改，并且通过一条命令就可以撤销某个事件对一系列文件的更改。另外，用户还可以方便的查看单个文件的所有保留版本，并可以恢复到任意版本。 (4) 方便移植的系统架构。GobackFS文件系统基于FUSE框架实现，是一个用户空间文件系统，可以方便地移植到多个Unix/Linux系统中使用，而不需要对内核做任何修改，也不需要复杂的配置。