Structural soundness of workflow nets is decidable

The problem of deciding whether a given workflow net is k-sound for some k?1 is known as structural soundness. We prove that structural soundness of workflow nets is decidable.     

基于Petri网的工作流模型简化

计算状态空间可达图是验证工作流正确性的主要方法,状态空间爆炸是这类方法的主要困难.文章对线性时态逻辑LTL-x描述的正确性提出了一种基于Petri网图形化简的验证方法,证明了所提出化简规则的完备性,并以实例说明了所提方法的有效性.     

关于水泥中方镁石危害性及其检测方法的研究现状与问题

简要地归纳了当前世界各国标准对水泥中氧化镁的规定,以方镁石危害性实质出发对压蒸安定性试验方法的影响因素和缺点进行了分析,提出了完善压蒸试验方法的工作方向。在综合现有氧化镁研究资料的基础上,为了保证混凝土工程质量和充分利用石灰石资源,水泥标准中应该用压蒸法检验安定性合格来代替当前化学成分MgO的限制。     

Empirical evidence for the usefulness of Armstrong relations in the acquisition of meaningful functional dependencies

Armstrong relations satisfy precisely those data dependencies that are implied by a given set of data dependencies. A common perception is that Armstrong relations are useful in the acquisition of data semantics, in particular since errors during the requirements elicitation have the most expensive consequences.     

Soundness in verification of algebraic specifications with OBJ

The algebraic specification tools of the OBJ family have no notion of open terms or quantifiers. Nonetheless there are methods of proving universally quantified statements about specifications. These methods are examined and found to be unsound.     

Unauthorized inferences in semistructured databases

In this paper we study the problem of providing controlled access to confidential data stored in semistructured databases. More specifically, we focus on privacy violations via data inferences that occur when domain knowledge is combined with non-private data. We propose a formal model, called Privacy Information Flow Model, to represent the information flow and the privacy requirements. These privacy requirements are enforced by the Privacy Mediator. Privacy Mediator guarantees that users are not be able to logically entail information that violates the privacy requirements. We present an inference algorithm that is sound and complete. The inference algorithm is developed for a tree-like, semistructured data model, selection-projection queries, and domain knowledge, represented as Horn-clause constraints.     

Petrographic, mechanical and chemical properties of major coarse aggregate resources in Lebanon, eastern Mediterranean

 In a previous study to locate the major coarse aggregate resources currently being exploited in the Lebanon, 20 major operating quarrying sites were located, described and sampled. This paper reports the evaluation of these samples, based on petrographic analysis and mechanical and chemical acceptance tests as well as the results of tests conducted on fresh and hardened concrete samples made with various types of coarse aggregate. In general, the samples were of good quality and suitable for use in concrete although the grading of the aggregates varied widely between quarries and some samples were found to be gap graded. Only the material from Berquayel failed the soundness test. Cherts were identified in some of the samples, leading to the conclusion that alkali-aggregate reactions might occur in these rocks. The results of the concrete tests showed that the measured concrete stiffness was in many cases slightly lower than the anticipated theoretical value. It is hoped that the results of the study will provide valuable assistance to all those involved in the construction industry, including engineers, contractors, ready-mix plant operators and government officials. Received: 21 September 1999 · Accepted: 10 December 1999     

Reasoning about dynamically evolving process structures

We develop a Hoare-style proof system for reasoning about the behaviour of processes that interact via a dynamically evolving communication structure.     

高钙粉煤灰与矿渣的复合及大掺量用于高性能混凝土的研究

根据对上海三家电厂排放的高钙灰的活性和安定性的试验结果，提出了对含有较高游离氧化钙含量的高钙灰的改性工艺及其可行性，并将改性后的高钙灰大掺量用于高性能混凝土。结果显示：经改性处理后的高钙灰不仅能提高混凝土的耐久性，而且能获得显著的经济和社会效益。     

About thaumasite formation in Portland-limestone cement pastes and mortars––effect of heat treatment at 95 °C and storage at 5 °C

Owing to the presence of finely divided calcite, mortars and concretes made with Portland-limestone cements are particularly susceptible to damaging thaumasite formation during sulfate attack at lower temperatures. This work reports the results of investigations on mortars made according to DIN/EN 196 and pastes (w/c ratio of 0.5) with CEM I 42,5 R, as well as with mixtures of cement with limestone filler. Some of the samples were heat-treated at 95 °C. The length changes and resonant frequencies of the samples were measured during long-term water-storage at 20 and 5 °C. There was no evidence from X-ray diffraction data of thaumasite formation in the samples. Only for pastes containing 30 wt.% limestone filler were small areas found by SEM and X-ray microanalysis whose chemical analysis matched thaumasite or a thaumasite–ettringite solid solution.