Estimating the feasibility of transition paths in extended finite state machines

There has been significant interest in automating testing on the basis of an extended finite state machine (EFSM) model of the required behaviour of the implementation under test (IUT). Many test criteria require that certain parts of the EFSM are executed. For example, we may want to execute every transition of the EFSM. In order to find a test suite (set of input sequences) that achieves this we might first derive a set of paths through the EFSM that satisfy the criterion using, for example, algorithms from graph theory. We then attempt to produce input sequences that trigger these paths. Unfortunately, however, the EFSM might have infeasible paths and the problem of determining whether a path is feasible is generally undecidable. This paper describes an approach in which a fitness function is used to estimate how easy it is to find an input sequence to trigger a given path through an EFSM. Such a fitness function could be used in a search-based approach in which we search for a path with good fitness that achieves a test objective, such as executing a particular transition, and then search for an input sequence that triggers the path. If this second search fails then we search for another path with good fitness and repeat the process. We give a computationally inexpensive approach (fitness function) that estimates the feasibility of a path. In order to evaluate this fitness function we compared the fitness of a path with the ease with which an input sequence can be produced using search to trigger the path and we used random sampling in order to estimate this. The empirical evidence suggests that a reasonably good correlation (0.72 and 0.62) exists between the fitness of a path, produced using the proposed fitness function, and an estimate of the ease with which we can randomly generate an input sequence to trigger the path

Generating a checking sequence with a minimum number of reset transitions

Given a finite state machine M, a checking sequence is an input sequence that is guaranteed to lead to a failure if the implementation under test is faulty and has no more states than M. There has been much interest in the automated generation of a short checking sequence from a finite state machine. However, such sequences can contain reset transitions whose use can adversely affect both the cost of applying the checking sequence and the effectiveness of the checking sequence. Thus, we sometimes want a checking sequence with a minimum number of reset transitions rather than a shortest checking sequence. This paper describes a new algorithm for generating a checking sequence, based on a distinguishing sequence, that minimises the number of reset transitions used.This work was supported in part by Leverhulme Trust grant number F/00275/D, Testing State Based Systems, Natural Sciences and Engineering Research Council (NSERC) of Canada grant number RGPIN 976, and Engineering and Physical Sciences Research Council grant number GR/R43150, Formal Methods and Testing (FORTEST)

Spin relaxation in (110) and (001) InAs/GaSb superlattices

We report an enhancement of the electron spin relaxation time (T1) in a (110) InAs/GaSb superlattice by more than an order of magnitude (25 times) relative to the corresponding (001) structure. The spin dynamics were measured using polarization sensitive pump probe techniques and a mid-infrared, subpicosecond PPLN OPO. Longer T1 times in (110) superlattices are attributed to the suppression of the native interface asymmetry and bulk inversion asymmetry contributions to the precessional D'yakonov Perel spin relaxation process. Calculations using a nonperturbative 14-band nanostructure model give good agreement with experiment and indicate that possible structural inversion asymmetry contributions to T1 associated with compositional mixing at the superlattice interfaces may limit the observed spin lifetime in (110) superlattices. Our findings have implications for potential spintronics applications using InAs/GaSb heterostructures.Comment: 4 pages, 2 figure

Community business resilience: Adaptation practice of micro-and small enterprises around the Pearl River Estuary

Small community businesses bear the brunt of climate change impacts. Studies of the vulnerability and resilience of such businesses predominantly focus on firm-level characteristics and organizational issues. This paper addresses the lack of individual-level considerations. It explores an analytical approach that draws upon the concepts of social capital and sense of place for understanding community businesses’ resilience to extreme weather. An empirical study was conducted to investigate whether and how the attributes of these concepts are related to adaptation practice. This study is based on a structured questionnaire survey of community businesses at various locations around the Pearl River Estuary that are exposed to storm surges. The findings partially support the hypothesis that action is more likely to be taken when social capital is strong. Community businesses are more likely to adopt adaptation strategies when their owners or operators perceive a higher level of social expectation, but are less likely to do so when they have better relationships with the people around them. This study indicated the potential for moral hazard driven by good social relationships and supported the understanding of small community businesses as firms and social agents in responding to climate change impacts. There is a need for recognizing the social dimensions of small businesses’ rationality in their adaptation and hazard adjustment, and strengthening their engagement with community-based adaptation through social institutions

Business vulnerability assessment: a firm-level analysis of micro-and small businesses in China

Micro- and small businesses are more vulnerable to natural hazards than the larger ones. However, there are few attempts to systematically assess their vulnerabilities. Existing business vulnerability assessments use aggregate-level data, which poorly account for the prevalence of micro- and informal businesses in some areas. Also, they focus on business sensitivity and have not incorporated key elements of adaptive capacity into analysis. This study explores a firm-level assessment approach that would work better under resource and data constraints, which are common challenges to developing-country researchers. Surveys were conducted in four jurisdictions of China: Sanya, Zhuhai, Macao and Hong Kong. A total of 596 urban and rural businesses were involved. Indicators of business sensitivity, exposure and adaptive capacity were built into a structured questionnaire. The results were turned into a set of metrics for cross-location comparison. Aggregated scores suggest that business vulnerabilities increase from Sanya, Zhuhai, Hong Kong to Macao. Additional tests show that the integrated vulnerability scores are geographically differentiated and demonstrate compatibility with theoretical expectations. The value of this approach lies in its appropriate and realistic requirements for conducting business vulnerability assessments in small, isolated or less developed communities. Future applications need to overcome some uncertainties in the assessment

In government we trust? Micro-business adaptation to climate change in four post-colonial and transitional economies of China

Public expectations of government influence private action for managing climate change risks. Institutional neglect or incompetence result in a loss of trust in public institutions, consequently discouraging the public from taking added responsibility for risk management. This has been explained in terms of social contract, but evidence suggests that a politics of distrust can reinforce alternative social drivers of action, rather than displacing action. This is empirically confirmed by the present study, which examines the tendencies for adopting private protective measures across a gradient of institutional trust. Surveys were conducted in four jurisdictions within China that operate under two different political-economic systems, namely, Hong Kong and Macao (liberal market economy), and Zhuhai and Sanya (socialist market economy). Structured interviews were conducted with 569 business operators to explore how their stated adaptation practice is related to institutional trust and social capital. We found that trust predicted action only in Sanya, which is characterized by a high level of public confidence in authorities. In places of lower institutional trust, social capital became a salient and powerful driver of action. The weakening of the social contracts in Hong Kong and Macao turned their people to alternative social mechanisms. We explain the results in terms of the development trajectories, socio-political norms and institutional settings of these jurisdictions. This study provides insights into how adaptation practice can be mediated by the consequences of a change in political leadership, policy, or governance arrangements that alters the relationship of trust

The transcriptomic G1-G6 signature of hepatocellular carcinoma in an Asian population Association of G3 with microvascular invasion

10.1097/MD.0000000000005263Medicine (United States)9547e526