Xiaocheng Ge

Pressure vessels, widely used in industries, are safety-critical equipments. Non-intrusive pressure measurement is aimed to monitor the pressure without destroying the vessel's integrity. Due to the acoustoelastic effect of ultrasonic waves, travel-time change of the critically refracted longitudinal wave (LCR wave) and reflected longitudinal waves can reflect the inner pressure of pressure vessel. Nevertheless, it has been identified that many factors, including coupling agent, exciting and receiving circuit of ultrasound, ultrasonic probes and their mounting characteristics, have notable impact on travel-time measurement accuracy. In this paper, a pressure sensor based on TDC-GP22 is designed. Additionally, a new method, adopting time-interval between neighboring longitudinal waves and multiple time-intervals fusion, is proposed, which can reduce the interference of factors mentioned above. Experiments are carried out to validate the method, and results show that the proposed method can achieve relatively accurate pressure measurement with mean relative error reduced to 3.61%. Furthermore model based on multiple time-intervals fusion without temperature compensation can also achieve relatively accurate pressure measurement (with mean relative error of 5.22%), which can greatly simplify the measurement system.

Measuring the pressure of a pressure vessel accurately is one of fundamental requirements of the operation of many complex engineering systems. Ultrasonic technique has been proposed to be a good alteration of non‐intrusive measurement. Based on the study of acoustoelastic effect and thin‐shell theory, it has been identified that the travel‐time changes of the critically refracted longitudinal wave (L _CR wave) and other reflected longitudinal waves are all proportional to the inner pressure. Considering the information redundancy in these waves, the authors proposed an approach for pressure measurement by using the information fusion algorithm on multiple reflected longitudinal waves. In this study, the authors discussed the fusion algorithm in details and proposed a pressure measurement model, which represents an accurate relationship between the pressure and the travel‐time changes of multiple waves. Through the experiment, the analysis of data collected from experiment system showed that the pressure measurement based on the multi‐wave model is notably more accurate than the one based on the single‐wave model (the average relative error can be <7.24% and the root‐mean‐square error can be lower than 0.3MPa).

Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system—for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (L_CR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave.

Safety-critical systems must be shown to be acceptably safe to deploy and use in their operational environment. One of the key concerns of developing safety-critical systems is to understand how the system behaves in the presence of failures, regardless of whether that failure is triggered by the external environment or caused by internal errors. Safety assessment at the early stages of system development involves analysis of potential failures and their consequences. Increasingly, for complex systems, model-based safety assessment is becoming more widely used. In this paper we propose an approach for safety analysis based on system interface models. By extending interaction models on the system interface level with failure modes as well as relevant portions of the physical system to be controlled, automated support could be provided for much of the failure analysis. We focus on fault modeling and on how to compute minimal cut sets. Particularly, we explore state space reconstruction strategy and bounded searching technique to reduce the number of states that need to be analyzed, which remarkably improves the efficiency of cut sets searching algorithm.

The effective provision of security in an agile development requires a new approach: traditional security practices are bound to equally traditional development methods. However, there are concerns that security is difficult to build incrementally, and can prove prohibitively expensive to refactor. This chapter describes how to grow security, organically, within an agile project, by using an incremental security architecture that evolves with the code. The architecture provides an essential bridge between system-wide security properties and implementation mechanisms, a focus for understanding security in the project, and a trigger for security refactoring. The chapter also describes criteria that allow implementers to recognize when refactoring is needed, and a concrete example that contrasts incremental and “top-down” architectures.

Oscillations usually propagate to other loops with the delivery of mass and energy, then cause plant-wide oscillation and affect the performance of whole control system in complex chemical process. DTF (Directed Transfer Function) method, which has been widely used to analyze information flow in the brain structures in biomedical area, is applied to the disturbance propagation analysis of complex chemical process in this paper. Based on MVAR (Multivariate Autoregressive) model, DTF can analyze the multivariate causality simultaneously and calculate the causality quantitatively. Based on the DTF value, one can draw the causality graph, get the disturbance propagation path and finally locate fault sources. The results of simulation on TEP (Tennessee Eastman Process) are presented to illustrate the effectiveness of the proposed approach.

Multiple Approaches to the Diagnosis of Attention Deficit Hyperactivity Disorder: 10.4018/ijhisi.2013100104: Studies indicate that about 3-7% of school-age children have attention deficit hyperactivity disorder (ADHD). If these disorders are not diagnosed and treated

Typically, safety critical software systems are developed using plan-driven development processes. Agile processes have evolved to help reduce costs of software development and seek to minimise documentation overheads. For safety critical systems that must undergo certification, documentation is essential. The question this paper addresses is: can a process based on agile principles be used to deliver a safety critical software product, but also the evidence needed to satisfy assurance objectives? The paper makes three contributions. Firstly, it presents an analysis of agile processes and their applicability in this domain. It reviews positive indicators for their use, outlines challenges associated with their deployment and proposes strategies for addressing these challenges. Secondly, it makes a number of recommendations for adapting an agile process to the domain. Finally, the paper reports on an experiment to demonstrate the plausibility of using of an adapted agile process for building a safety critical software system.