A new verification technique for large processes based on identification of relevant tasks

Verification recently has become a challenging topic for business process languages. Verification techniques like model checking allow to ensure that a process complies with domain-specific requirements, prior to the execution. To execute full-state verification techniques like model checking, the state space of the process needs to be constructed. This tends to increase exponentially with the size of the process schema, or it can even be infinite. We address this issue by means of requirements-specific reduction techniques, i.e., reducing the size of the state space without changing the result of the verification. We present an approach that, for a given requirement the system must fulfill, identifies the tasks relevant for the verification. Our approach then uses these relevant tasks for a reduction that confines the process to regions of interest for the verification. To evaluate our new technique, we use real-world industrial processes and requirements. Mainly because these processes make heavy use of parallelization, full-state-search verification algorithms are not able to verify them. With our reduction in turn, even complex processes with many parallel branches can be verified in less than 10 s.     

Model checking temporal knowledge and commitments in multi-agent systems using reduction

Though modeling and verifying Multi-Agent Systems (MASs) have long been under study, there are still challenges when many different aspects need to be considered simultaneously. In fact, various frameworks have been carried out for modeling and verifying MASs with respect to knowledge and social commitments independently. However, considering them under the same framework still needs further investigation, particularly from the verification perspective. In this article, we present a new technique for model checking the logic of knowledge and commitments (CTLKC⁺). The proposed technique is fully-automatic and reduction-based in which we transform the problem of model checking CTLKC⁺ into the problem of model checking an existing logic of action called ARCTL. Concretely, we construct a set of transformation rules to formally reduce the CTLKC⁺ model into an ARCTL model and CTLKC⁺ formulae into ARCTL formulae to get benefit from the extended version of NuSMV symbolic model checker of ARCTL. Compared to a recent approach that reduces the problem of model checking CTLKC⁺ to another logic of action called GCTL¹, our technique has better scalability and efficiency. We also analyze the complexity of the proposed model checking technique. The results of this analysis reveal that the complexity of our reduction-based procedure is PSPACE-complete for local concurrent programs with respect to the size of these programs and the length of the formula being checked. From the time perspective, we prove that the complexity of the proposed approach is P-complete with regard to the size of the model and length of the formula, which makes it efficient. Finally, we implement our model checking approach on top of extended NuSMV and report verification results for the verification of the NetBill protocol, taken from business domain, against some desirable properties. The obtained results show the effectiveness of our model checking approach when the system scales up.     

Blockchain verification and validation: Techniques,challenges, and research directions

As blockchain technology is gaining popularity in industry and society, solutions for Verification and Validation (V&V) of blockchain-based software applications (BC-Apps) have started gaining equal attention. To ensure that BC-Apps are properly developed before deployment, it is paramount to apply systematic V&V to verify their functional and non-functional requirements. While existing research aims at addressing the challenges of engineering BC-Apps by providing testing techniques and tools, blockchain-based software development is still an emerging research discipline, and therefore, best practices and tools for the V&V of BC-Apps are not yet sufficiently developed. In this paper, we provide a comprehensive survey on V&V solutions for BC-Apps. Specifically, using a layered approach, we synthesize V&V tools and techniques addressing different components at various layers of the BC-App stack, as well as across the whole stack. Next, we provide a discussion on the challenges associated with BC-App V&V, and summarize a set of future research directions based on the challenges and gaps identified in existing research work. Our study aims to highlight the importance of BC-App V&V and pave the way for a disciplined, testable, and verifiable BC development.     

斜轧穿孔法制备Ti80合金无缝管工艺分析

运用有限元技术模拟了两辊斜轧穿孔法制备Ti80合金无缝管坯的三维热力耦合过程。仿真结果能动态显示坯料从咬入到稳定穿孔再到穿出3个阶段复杂的塑性成形过程,并能辅助分析中心孔腔的形成机理以及坯料在穿孔阶段各物理场量的分布。结果表明:坯料刚接触顶头时,中心金属存在明显塑性变形,结合轧制中心线上不同方向的正应力状态为(+,-,+),判断中心孔腔的形成为拉应力作用下的塑性开裂。在穿孔过程中,坯料的应变分布沿轴向呈U1+W+2U2形态,沿径向为片层状,最终穿制毛管等效应变可达5～11;坯料的外表面与导盘接触区应变速率为0.71～3.6s~(-1),而与轧辊接触区高达4.6～26s~(-1),大的应变速率有助于毛管的塑性成形过程;顶头前坯料的温度最高,与穿孔工具接触的区域温度略有降低,但绝大部分变形区温度都处于单相区。模拟所得全流程顶头轴向力与轧制力的变化呈现典型的3阶段分布,其中稳定穿孔阶段力能参数的均值接近试验所得,从而验证了模型的准确性。基于有限元模拟的工艺条件,在实验轧机上一火次顺利穿制出Ti80合金无缝管坯,其显微组织展现为单一的魏氏组织形态,且由于变形剧烈,从外表面到中间层再到内表面均为等轴细小的β动态再结晶晶粒;力学性能测试表明该组织状态下的毛管的强度和塑性均满足指标要求。     

The VALU3S ECSEL project: Verification and validation of automated systems safety and security

Manufacturers of automated systems and their components have been allocating an enormous amount of time and effort in R&D activities, which led to the availability of prototypes demonstrating new capabilities as well as the introduction of such systems to the market within different domains. Manufacturers need to make sure that the systems function in the intended way and according to specifications. This is not a trivial task as system complexity rises dramatically the more integrated and interconnected these systems become with the addition of automated functionality and features to them. This effort translates into an overhead on the V&V (verification and validation) process making it time-consuming and costly. In this paper, we present VALU3S, an ECSEL JU (joint undertaking) project that aims to evaluate the state-of-the-art V&V methods and tools, and design a multi-domain framework to create a clear structure around the components and elements needed to conduct the V&V process. The main expected benefit of the framework is to reduce time and cost needed to verify and validate automated systems with respect to safety, cyber-security, and privacy requirements. This is done through identification and classification of evaluation methods, tools, environments and concepts for V&V of automated systems with respect to the mentioned requirements. VALU3S will provide guidelines to the V&V community including engineers and researchers on how the V&V of automated systems could be improved considering the cost, time and effort of conducting V&V processes. To this end, VALU3S brings together a consortium with partners from 10 different countries, amounting to a mix of 25 industrial partners, 6 leading research institutes, and 10 universities to reach the project goal.     

散体连续流动特殊方程及放矿理论的检验

对散体只按一般连续性方程进行流动检验是不够的，通过对单位时间、单位高度散体移动范围内应遵守质量守恒定律的研究，建立了散体连续流动的特殊方程(特殊连续性方程)；提出对于散体应该进行2个内容的连续流动检验：一般连续性方程检验和特殊连续性方程检验，并对主要放矿理论进行了特殊连续性方程检验。结果表明：类椭球体放矿理论能通过特殊连续性方程检验。     

BIM技术在兰州西客站站房工程中的典型应用

文章以兰州西客站项目中BIM技术的应用为例,探索施工企业在火车站站房类工程中施工流程、工程难点、解决方案、专业化应用等BIM技术的典型应用,为类似工程提供参照意义。通过集中解决土建工程量计算、钢结构屋面网架的二次深化设计和吊装施工模拟等重点难点,进而提高了专业化应用的质量,充分发挥了BIM技术在提高施工企业＂三控三管及协调＂、绿色施工等方面的作用。     

The shear strength of nano-Ag sintered joints and the use of Ag interconnects in the design and manufacture of SiGe-based thermo-electric modules

Thermo-electric modules (TEMs) can be used to convert heat into electricity by utilizing the Seeback effect. It is now possible to buy BiTe thermo-electric modules that can operate up to temperatures of around 300 °C. However, many applications, such as the harvesting of excess gas turbine heat, may occur at higher temperatures. Therefore, new materials and manufacturing processes need to be developed to produce packaged TEMs that can operate at a maximum operating temperature of 650 °C. Two critical areas in the manufacture of a SiGe TEM are the choice and strength of materials used to both sintered joint the TE material to the rest of the module and the metal used for the interconnects. The interconnection material needs to be sufficiently strong to withstand large temperature fluctuations while maintaining a low contact resistance, as well as being compatible with the nano-Ag sintered joint. Shear force tests of the sintered thermo electrical leg material showed that the joints are brittle when sintered to W metallized AlN substrates are used and ductile fracture behavior when sintered to Cu metallized AlN substrates using the NanoTach K nano silver paste. Almost all of the joints were found to be brittle when using the NachTach X nano silver paste. Shear testing of the sintered joints showed that the X paste joints were variable in strength and stiffness, having a typical Young’s modulus between 10 and 100 MPa at room temperature. The K paste joints were stiffer, but had a similar strength as compared to the X paste joints.     

Metacarpophalangeal joint patterns based personal identification system

This paper introduces a novel approach for identity authentication system based on metacarpophalangeal joint patterns (MJPs). A discriminative common vector (DCV) based method is utilized for feature selection. In the literature, there is no study using whole MJP for identity authentication, exceptionally a work (Ferrer et al., 2005) using the hand knuckle pattern which is some part of the MJP draws the attention as a similar study. The originality of this approach is that: whole MJP is firstly used as a biometric identifier and DCV method is firstly applied for extracting the feature set of MJP. The developed system performs some basic tasks like image acquisition, image pre-processing, feature extraction, matching, and performance evaluation. The feasibility and effectiveness of this approach is rigorously evaluated using the k-fold cross validation technique on two different databases: a publicly available database and a specially established database. The experimental results indicate that the MJPs are very distinctive biometric identifiers and can be securely used in biometric identification and verification systems, DCV method is successfully employed for obtaining the feature set of MJPs and proposed MJP based authentication approach is very successful according to state of the art techniques with a recognition rate of between 95.33% and 100.00%.     

Indices for the evaluation of wildfire spread simulations using contemporaneous predictions and observations of burnt area

Methods to objectively evaluate performance are critical for model development. In contrast to recent advances in wildfire simulation, there has been limited attention to evaluating fire model performance. Information to validate fire models is typically limited, commonly to a few perimeter observations at a small number of points in time. We review metrics for comparing two burnt areas at a point in time: observed and predicted. These are compared in an idealised landscape and with a case study evaluating the performance of simulations of an Australian wildfire. We assessed: Shape Deviation Index (SDI), Jaccard's coefficient, F1, Sørensen's Similarity and Area Difference Index (ADI). For decomposing fit into error components (overprediction and underprediction) we assessed the partial indices of SDI and ADI, Precision and Recall. The various metrics were evaluated for their ability to represent error and their suitability for use in model improvement frameworks.