facilitating formal specification acquisition by using recursive functions on context-free languages

Although formal specification techniques are very useful in software development, the acquisition of formal specifications is a difficult task. This paper presents the formal specification language LFC, which is designed to facilitate the acquisition and validation of formal specifications. LFC uses context-free languages for syntactic aspect and relies on a new kind of recursive functions, i.e. recursive functions on context-free languages, for semantic aspect of specifications. Construction and validation of LFC specifications are machine-aided. The basic ideas behind LFC, the main aspects of LFC, and the use of LFC and illustrative examples are described.

基于最终用户开发的表格数据分析关键技术研究

“最终用户开发（End-User Development，EUD）”研究如何使作为非专业软件开发者的软件系统用户，在一定程度上开发或修改软件。EUD的研究主要有三类，即EUD的理论研究、通用的EUD技术研究和面向领域的EUD技术研究。作为一个面向领域的EUD研究，本文以电子政务中常见的表格数据分析问题为背景，研究表格数据分析的EUD方法和技术。 表格数据分析是一种广泛存在的日常应用问题，除了各种业务系统中的表格分析系统，工业界也引入了EUD，比如“电子表格（Spreadsheet）”，但无论专用分析系统，还是Spreadsheet，都不足以应对表格数据分析问题在规模和复杂度方面的迅速增长。 本文在对表格数据分析问题进行建模的基础上，提出一种基于EUD的表格数据分析方法（Methodology of EUD-Enabled Tabular-data Analysis，META），并就META方法的应用和所需的关键支撑技术开展了研究，其贡献包括以下七个方面： 1）在Spreadsheet模型的基础上，对大规模表格数据分析问题进行了建模，该模型以数据层、逻辑层和表示层的分离为特征，对表格数据、表格展示和表格数据分析计算的表达能力，都超过已有的各种模型。 2）提出一种以EUD为核心的表格数据分析方法（META），该方法有三种应用模式，分别适用于不同的用户熟练程度和需求复杂度，既适用于简单的表格数据生成问题，也能支持复杂的EUD生命周期过程。 3）在对表格数据分析问题进行建模的基础上，通过扩展传统Spreadsheet语言，设计了一种支持最终用户开发的表格数据分析语言ESL（EUD-Enabled Spreadsheet Language），该语言继承了Spreadsheet语言的最终用户可编程性，同时，在表格数据分析方面的表达能力优于已有的其他语言。 4）在将ESL公式依赖关系建模的基础上，深入研究了影响Spreadsheet计算性能的各种因素。提出了基于拓扑排序的重算消减算法，解决了传统算法中存在的重算问题；以拓扑排序算法为基础，提出了ESL语言的并行计算方法；针对大规模表格数据访问，实现了能够显著降低SQL数据访问代价的缓存机制。这些研究，经实验验证，提高了ESL语言的执行效率。 5）为降低EUD中SQL编程的复杂度，通过引入领域语义和上下文（Context）配置的方法，解决了SQL自动生成中连接选择的二义性问题，实现了精确查询的SQL自动生成。其结果也可用于其他访问关系数据库的EUD系统。 6）有效性是ESL编程中的重要问题，由于缺乏合适的研究对象和用户群体，EUD有效性研究受到限制。在社会关系网络上开发Web插件，是一种典型的EUD活动，其中的“发行前错误”问题是一种重要的风险来源。本文提出的Release-Waiting Farm（RWF）技术，能够有效地引导最终用户对Web插件进行测试，并规范最终用户的开发过程。 7）本文总结了RWF技术在社会关系网络中得以成功的关键因素，基于RWF技术，为META方法设计了支持最终用户开发的协作环境和测试环境，并在全国组织系统软件框架开发项目中进行了实现和验证。

海量层次信息的Focus+Context交互式可视化技术

综述了海量层次信息可视化与Focus+Context技术的相关工作,针对海量层次信息可视化的交互问题,在嵌套圆可视化技术的基础上提出了基于上下文感知的Focus+Context交互式可视化技术.首先,基于外切圆排列方法提出对圆心进行三角网格剖分的方法,为变形计算建立上下文;然后,针对变形计算前后上下文一致性问题,在三角网格邻居跟踪方法的基础上,提出了用于同层兄弟节点上下文感知的外切圆变形排列方法,以及用于父子节点上下文感知的嵌套圆迭代排列方法.实验结果表明。上述方法在实现焦点突出的鱼眼视图的同时,能够有效地解决Focus+Context交互式可视化的上下文感知问题.上述方法应用于文件系统海量层次信息的交互式可视化问题,提供了交互式可视化工具.

Visual-Context Boosting for Eye Detection

Eye detection plays an important role in many practical applications. This paper presents a novel two-step scheme for eye detection. The first step models an eye by a newly defined visual-context pattern (VCP), and the second step applies semisupervised boosting for precise detection. VCP describes both the space and appearance relations between an eye region (region of eye) and a reference region (region of reference). The context feature of a VCP is extracted by using the integral image. Aiming to reduce the human labeling efforts, we apply semisupervised boosting, which integrates the context feature and the Haar-like features for precise eye detection. Experimental results on several standard face data sets demonstrate that the proposed approach is effective, robust, and efficient. We finally show that this approach is ready for practical applications.

Context and conformation dictate function of a transcription antitermination switch

In bacteriophage, transcription elongation is regulated by the N protein, which binds a nascent mRNA hairpin ( termed boxB) and enables RNA polymerase to read through distal terminators. We have examined the structure, energetics and in vivo function of a number of N boxB complexes derived from in vitro protein selection. Trp18 fully stacks on the RNA loop in the wild-type structure, and can become partially or completely unstacked when the sequence context is changed three or four residues away, resulting in a recognition interface in which the best binding residues depend on the sequence context. Notably, in vivo antitermination activity correlates with the presence of a stacked aromatic residue at position 18, but not with N boxB binding affinity. Our work demonstrates that RNA polymerase responds to subtle conformational changes in cis-acting regulatory complexes and that approximation of components is not sufficient to generate a fully functional transcription switch.

Crystal structure of a noval poly(aryl ether ketone) containing meta-phenyl linkage

Crystal structure of a novel aryl ether ketone polymer poly(aryl ether ketone ether ketone ketone containing meta-phenyl linkage)(PEKEKmK) was determined by means of WAXD and ED. An orthorhombic unit cell is proposed containing two chains with a=0.772 nm, b=0.604 nm and c=2.572 nm. According to the orthorhombic system, the 10 reflections of this polymer were indexed.

Crystal structure and variation in unit cell parameters with crystallization temperatures of poly (ether ketone ether ketone ketone)s containing meta-phenyl links (PEKEKmK)

The X-ray diffraction patterns of the crystalline aromatic ketone polymer PEKEKmK (aryl ether ketone ether ketone ketone polymer containing meta-phenyl links) have been investigated (for the chemical structure, see Formula). An orthorhombic unit cell is proposed to contain two chains with a = 0.772 nm, b = 0.604 nm and c = 2.572 nm. According to the orthorhombic system, the 11 reflections of this polymer were indexed. Meanwhile, variation in unit cell parameters with crystallization temperatures of PEKEKmK was also investigated. [GRAPHICS]

Synthesis and crystallization of a novel poly(ether ketone ether ketone ketone) containing meta-phenylene linkage: PEKEKK(T/I)

Poly(ether ketone ether ketone ketone) containing meta-phenylene linkage (PEKEKK(T/I)) was synthesized by electrophilic Friedel-Crafts acylation condensation of 1, 4-diphenoxybenzophenone with terephthaloyl chloride (T) and isophthaloyl chloride (I) with a T/I ratio of 1 and characterized by LR,DSC,TGA and WAXD. PEKEKK(T/I) has two different crystal structures: a conventional Farm I structure, the same as that observed in PEEK and PEK, wich is usually developed from melt crystallization, and a new Form II structure which can be developed from cold crystallization or solvent induced crystallization (by exposing the glassy sample to methylene chloride).

Crystallization behavior of a novel ether ketone polymer containing meta-phenylene linkage: PEKEKK (T/I)

Nonisothermal and isothermal melt crystallization kinetics of a novel aryl ether ketone polymer containing meta-phenylene linkages, PEKEKK (T/I), were studied by differential scanning calorimetry (DSC). The Avrami equation modified by Jeziorny and a new approach by combining the Avrami equation with the Ozawa equation could describe the nonisothermal crystallization. Isothermal crystallization could also be described by the Avrami equation. The activation energies were 187 and 159 kJ/mol for nonisothermal and isothermal crystallization, respectively. Using the Hoffman-Weeks method, the equilibrium melting point T-m(o) was estimated as 353 degrees C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter K-g of the isothermal melt crystallization was estimated as 5.49 x 10(5) K-2. The crystallization characteristics of PEKEKK (T/I) were compared with those of all-para PEKEKK. The differences were explained by differences in the chain flexibility of the two polymers.

Crystallization process and morphology structure of poly(aryl ether ether ketone ketone) containing meta-phenyl links

The crystallization process and morphology of poly(aryl ether ether ketone ketone) containing meta-phenyl links (PEEKmK) have been investigated by transmission electron microscopy and electron diffraction. The results indicate that the thin films of PEEKmK isothermally crystallized from both the glassy state and the melt at the temperature range of 180 similar to 250 degrees C consist of two kinds of morphological forms, i. e. large (order of mu m), flat-on single crystals and narrow, lath-like, edge-on lamellae, The latter consists of the spherulites. Meanwhile, the growing process of the two kinds of morphological forms has been discussed.

X-ray crystallographic structure of meta- and para-dimethyl ester of pyromellitic acid

The polycrystalline powder of para- and meta-dimethyl ester of pyromellitic acid (PMDE) have been prepared by fractional crystallization, and their crystal structures have been determined by Wide-Angle X-ray Diffraction (WAXD). Both p-PMDE and m-PMDE was found to be orthorhombic crystal system, and their unit cell parameters a = 0.840 nm, b = 0.707 nm, c = 1.136 nm and a = 1.032 nm; b = 0.835 nm, c = 0.714 nm, respectively. Space group all belongs to P-mmm. p-PMDE has two molecules per unit cell with crystal density 1.388 g . cm(-3), while m-PMDE has two molecules per unit cell with crystal density 1.522 g . cm(-3). Indices of crystal diffraction peaks are also detailed in the present work. The difference in crystal structures between p-PMDE and m-PMDE has thus been used to explain the curing behavior of isomerically pyromellitic dianhydride-based poly(amic ester)s.

Synthesis and properties of poly(aryl ether ether ketone ketone) containing meta-phenyl links

A Series of poly(aryl ether ether ketone ketone) containing meta-phenyl link were synthesized, the general properties were studied by DSC, stretch, impact, etc.. The results indicated that with the raising of meta linkage monomer fractions, the glass transition point decreased, the melting temperature decreased at first, and then disappeared, but for all-meta-linked polymer, T-m appeared once more. And this kind of polymer had good stretch and impact resistance performance.