Modelling Chinese Smart Grid: A Stochastic Model Checking Case Study

Cyber-physical systems integrate information and communication technology functions to the physical elements of a system for monitoring and controlling purposes. The conversion of traditional power grid into a smart grid, a fundamental example of a cyber-physical system, raises a number of issues that require novel methods and applications. In this context, an important issue is the verification of certain quantitative properties of the system. In this technical report, we consider a specific Chinese Smart Grid implementation and try to address the verification problem for certain quantitative properties including performance and battery consumption. We employ stochastic model checking approach and present our modelling and analysis study using PRISM model checker

An SMT-Based Approach to the Formal Analysis of MARTE/CCSL

International audienceMARTE (abbreviated for Modeling and Analysis of Real-Time and Embedded systems) is a UML profile which provides a generalmodeling framework to design and analyze real-time embedded systems. CCSL (abbreviated for Clock Constraint Specification Language) is aformal language companion to MARTE, used to specify the constraints between the occurrences of events in real-time embedded systems. Many approaches have been proposed to the formal analysis of CCSL such as simulation and model checking. We propose in this paper an SMT-based approach to the formal analysis of CCSL. It is well-known that the SMT-based approach can effectively overcome the state-explosion problem for model checking, and can also be used for theorem proving. The latter feature allows us to prove the invalidity of CCSL constraints, which most of the existing approaches lack. We implement the proposed approach in a prototype tool clyzer on top of K framework and use Z3 as theunderlying SMT solver

Formal analysis of a calculus for WSNs from quality perspective

In viewing the common unreliability problem in wireless communications, the CWQ calculus (a Calculus for Wireless sensor networks from Quality perspective) was recently proposed for modeling and reasoning about WSNs (Wireless Sensor Networks) and their applications from a quality perspective. The CWQ calculus ensures that sensor nodes, even though in an unreliable communication network, can still behave in a reasonable manner using default values. Nevertheless, the topological structure in CWQ calculus is considered at the network level and it is tightly coupled with the processes and other configurations; this may limit its flexibility. In this paper, we extend our previous CWQ calculus to be a parametric framework to make it more flexible to be able to model and reason about networks of different topological structures. In the parametric framework, we extract the topological structure of a network and make it to be a configuration so that all topological structure changes can be captured by this framework

Language evolution and healthiness for critical cyber‐physical systems

From Wiley via Jisc Publications RouterHistory: received 2020-04-13, rev-recd 2020-05-13, accepted 2020-06-25, pub-electronic 2020-09-16, pub-print 2021-09Article version: VoRPublication status: PublishedFunder: National Natural Science Foundation of China; Id: http://dx.doi.org/10.13039/501100001809; Grant(s): 61872145Funder: National Key Research and Development Program of China; Id: http://dx.doi.org/10.13039/501100012166; Grant(s): 2018YFB2101300Funder: Shanghai Collaborative Innovation Center of Trustworthy Software for Internet of Things; Grant(s): ZF1213Abstract: In the effort to develop critical cyber‐physical systems, it is tempting to extend existing computing formalisms to include continuous behaviour. This may happen in a way that neglects elements necessary for correctly expressing continuous properties of the mathematics and correct physical properties of the real‐world physical system. A simple language is taken to illustrate these possibilities. Issues and risks latent in this kind of approach are identified and discussed under the umbrella of ‘healthiness conditions’. Modifications to the language in the light of the conditions discussed are elaborated, resulting in the language Combined Discrete and Physical Programmes in Parallel (CDPPP). An example air conditioning system is used to illustrate the concepts presented, and it is developed both in the original ‘unhealthy’ language and in the modified ‘healthier’ CDPPP. The formal semantics of the improved language is explored

Formalising the Continuous/Discrete Modeling Step

Formally capturing the transition from a continuous model to a discrete model is investigated using model based refinement techniques. A very simple model for stopping (eg. of a train) is developed in both the continuous and discrete domains. The difference between the two is quantified using generic results from ODE theory, and these estimates can be compared with the exact solutions. Such results do not fit well into a conventional model based refinement framework; however they can be accommodated into a model based retrenchment. The retrenchment is described, and the way it can interface to refinement development on both the continuous and discrete sides is outlined. The approach is compared to what can be achieved using hybrid systems techniques.Comment: In Proceedings Refine 2011, arXiv:1106.348

Field Emission Properties and Fabrication of CdS Nanotube Arrays

A large area arrays (ca. 40 cm2) of CdS nanotube on silicon wafer are successfully fabricated by the method of layer-by-layer deposition cycle. The wall thicknesses of CdS nanotubes are tuned by controlling the times of layer-by-layer deposition cycle. The field emission (FE) properties of CdS nanotube arrays are investigated for the first time. The arrays of CdS nanotube with thin wall exhibit better FE properties, a lower turn-on field, and a higher field enhancement factor than that of the arrays of CdS nanotube with thick wall, for which the ratio of length to the wall thickness of the CdS nanotubes have played an important role. With increasing the wall thickness of CdS nanotube, the enhancement factorβdecreases and the values of turn-on field and threshold field increase

Core Hybrid Event-B I: Single Hybrid Event-B machines

Faced with the increasing need for correctly designed hybrid and cyber-physical systems today, the problem of including provision for continuously varying behaviour as well as the usual discrete changes of state is considered in the context of Event-B. An extension of Event-B called Hybrid Event-B is presented, that accommodates continuous behaviours (called pliant events) in between familiar discrete transitions (called mode events in this context). The continuous state change can be specified by a combination of indirect specification via ordinary differential equations, or direct specification via assignment of variables to values that depend on time, or indirect specification by demanding that behaviour obeys a time dependent predicate. The syntactic elements of the extension are discussed, and the semantics is described in terms of the properties of time dependent valuations of variables. Refinement is examined in detail, with reference to the notion of refinement inherited from discrete Event-B. A full suite of proof obligations is presented, covering all aspects of the new framework. A selection of examples and case studies is presented. A particular challenge - bearing in mind the desirability of conforming to existing intuitions about discrete Event-B, and the impact on tool support (as embodied in tools for discrete Event-B like Rodin) - is to design the whole framework so as to disturb as little as possible the existing structures for handling discrete Event-B

Ultra-Sensitivity Glucose Sensor Based on Field Emitters

A new glucose sensor based on field emitter of ZnO nanorod arrays (ZNA) was fabricated. This new type of ZNA field emitter-based sensor shows high sensitivity with experimental limit of detection of 1 nM glucose solution and a detection range from 1 nM to 50 μM in air at room temperature, which is lower than that of glucose sensors based on surface plasmon resonance spectroscopy, fluorescence signal transmission, and electrochemical signal transduction. The new glucose sensor provides a key technique for promising consuming application in biological system for detecting low levels of glucose on single cells or bacterial cultures