A choice relation framework for supporting category-partition test case generation

We describe in this paper a choice relation framework for supporting category-partition test case generation. We capture the constraints among various values (or ranges of values) of the parameters and environment conditions identified from the specification, known formally as choices. We express these constraints in terms of relations among choices and combinations of choices, known formally as test frames. We propose a theoretical backbone and techniques for consistency checks and automatic deductions of relations. Based on the theory, algorithms have been developed for generating test frames from the relations. These test frames can then be used as the basis for generating test cases. Our algorithms take into consideration the resource constraints specified by software testers, thus maintaining the effectiveness of the test frames (and hence test cases) generated.published_or_final_versio

Hydrostatic pressure induced Dirac semimetal in black phosphorus

Motivated by recent experimental observation of an hydrostatic pressure induced transition from semiconductor to semimetal in black phosphorus [Chen et al. in arXiv:1504.00125], we present the first principles calculation on the pressure effect of the electronic structures of black phosphorus. It is found that the band crossover and reversal at the Z point occur around the critical pressure Pc1=1.23 Gpa, and the band inversion evolves into 4 twofold-degenerate Dirac cones around the Z point, suggesting a 3D Dirac semimetal. With further increasing pressure the Dirac cones in the Gamma-Z line move toward the Gamma point and evolve into two hole-type Fermi pockets, and those in the Z-M lines move toward the M point and evolve into 2 hole-type Fermi pockets up to P=4.0 Gpa. It demonstrates clearly that the Lifshitz transition occurs at $P_{c1}$ from semiconductor to 3D Dirac semimetal protected by the nonsymmorphic space symmetry of bulk. This suggests the bright perspective of black phosphorus for optoelectronic and electronic devices due to its easy modulation by pressure.Comment: 7 pages, 9 figures, and 2 table

A new restructuring algorithm for the classification-tree method

The classification-tree method developed by Grochtmann and Grimm facilitates the identification of test cases from functional specifications via the construction of classification trees. Their method has been enhanced by Chen and Poon through the classification-tree construction and restructuring methodologies. We find, however that the restructuring algorithm by Chen and Poon is applicable only to certain types of classification trees. We introduce a new tree-restructuring algorithm to supplement their work.published_or_final_versio

A flexible AC distribution system device for a microgrid

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How can non-technical end users effectively test their spreadsheets?

Purpose – An alarming number of spreadsheet faults have been reported in the literature, indicating that effective and easy-to-apply spreadsheet testing techniques are not available for “non-technical,” end-user programmers. The purpose of this paper is to alleviate the problem by introducing a metamorphic testing (MT) technique for spreadsheets. Design/methodology/approach – The paper discussed four common challenges encountered by end-user programmers when testing a spreadsheet. The MT technique was then discussed and how it could be used to solve the common challenges was explained. An experiment involving several “real-world” spreadsheets was performed to determine the viability and effectiveness of MT. Findings – The experiment confirmed that MT is highly effective in spreadsheet fault detection, and yet MT is a general technique that can be easily used by end-user programmers to test a large variety of spreadsheet applications. Originality/value – The paper provides a detailed discussion of some common challenges of spreadsheet testing encountered by end-user programmers. To the best of the authors knowledge, the paper is the first that includes an empirical study of how effective MT is in spreadsheet fault detection from an end-user programmer's perspective

On the identification of categories and choices for specification-based test case generation

HKU CS Tech Report TR 2004-02The category-partition method and the classification-tree method help construct test cases from specifications. In both methods, an early step is to identify a set of categories (or classifications) and choices (or classes). This is often performed in an ad hoc manner due to the absence of systematic techniques. In this paper, we report and discuss three empirical studies to investigate the common mistakes made by software testers in such an ad hoc approach. The empirical studies serve three purposes: (a) to make the knowledge of common mistakes known to other testers so that they can avoid repeating the same mistakes, (b) to facilitate researchers and practitioners develop systematic identification techniques, and (c) to provide a means of measuring the effectiveness of newly developed identification techniques. Based on the results of our studies, we also formulate a checklist to help testers detect such mistakes. © 2004 Elsevier B.V. All rights reserved.postprin

Smart distribution network device for microgrid applications

This paper focuses on the design of a smart distribution network device for improving the power quality and reliability of the overall power distribution system that the microgrid is connected to. The control design employs a newly developed Model Predictive Control algorithm which optimizes the steady-state and the transient control problems separately to achieve a faster computational time for large power systems. Kalman filters are also employed as state observers to identify the required signals needed for monitoring purposes as well as to extract the harmonic spectra of the grid voltage and the load currents. The design concept is verified through different test case scenarios to demonstrate the capability of the proposed device and the results obtained are discussed. © 2012 IEEE.published_or_final_versio

Coordinated control and energy management of distributed generation inverters in a microgrid

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Evolutionary game of coalition building under external pressure

We study the fragmentation-coagulation (or merging and splitting) evolutionary control model as introduced recently by one of the authors, where $N$ small players can form coalitions to resist to the pressure exerted by the principal. It is a Markov chain in continuous time and the players have a common reward to optimize. We study the behavior as $N$ grows and show that the problem converges to a (one player) deterministic optimization problem in continuous time, in the infinite dimensional state space