Identifying Patch Correctness in Test-Based Program Repair

Test-based automatic program repair has attracted a lot of attention in recent years. However, the test suites in practice are often too weak to guarantee correctness and existing approaches often generate a large number of incorrect patches. To reduce the number of incorrect patches generated, we propose a novel approach that heuristically determines the correctness of the generated patches. The core idea is to exploit the behavior similarity of test case executions. The passing tests on original and patched programs are likely to behave similarly while the failing tests on original and patched programs are likely to behave differently. Also, if two tests exhibit similar runtime behavior, the two tests are likely to have the same test results. Based on these observations, we generate new test inputs to enhance the test suites and use their behavior similarity to determine patch correctness. Our approach is evaluated on a dataset consisting of 139 patches generated from existing program repair systems including jGenProg, Nopol, jKali, ACS and HDRepair. Our approach successfully prevented 56.3\% of the incorrect patches to be generated, without blocking any correct patches.Comment: ICSE 201

Distributed Contingency Analysis over Wide Area Network among Dispatch Centers

Traditionally, a regional dispatch center uses the equivalent method to deal with external grids, which fails to reflect the interactions among regions. This paper proposes a distributed N-1 contingency analysis (DCA) solution, where dispatch centers join a coordinated computation using their private data and computing resources. A distributed screening method is presented to determine the Critical Contingency Set (DCCS) in DCA. Then, the distributed power flow is formulated as a set of boundary equations, which is solved by a Jacobi-Free Newton-GMRES (JFNG) method. During solving the distributed power flow, only boundary conditions are exchanged. Acceleration techniques are also introduced, including reusing preconditioners and optimal resource scheduling during parallel processing of multiple contingencies. The proposed method is implemented on a real EMS platform, where tests using the Southwest Regional Grid of China are carried out to validate its feasibility.Comment: 5 pages, 6 figures, 2017 IEEE PES General Meetin

Providing Virtual Inertia Through Power Electronics

VSC-HVDC (voltage source converter based HVDC) system with its inherent merits for renewable energy integration has captured increasing research attentions. However, compared with AC systems dominated by synchronous generators (SGs), VSC-HVDC systems with general vector control cannot provide inertia for the grid due to lack of kinetic energy. This tends to degrade the safety and stability of the grid with the increasing penetration of renewable energy sources. To cope with this issue, virtual synchronous generator (VSG) has been proposed. In this thesis, firstly, a comprehensive introduction of various typologies of VSG schemes is made to illustrate their deficiencies and merits. The simulation results established in Simulink/Plecs show that VSG can not only participate into the regulation of frequency and voltage in case of power disturbances but guarantee the inertia provision for the grid. Although the integration of VSG control enhances the inertia and damping response of inverts, researches show that plenty of issues relative with VSG should be ameliorated. The fluctuation performances of SGs are introduced into the output active power and current of inverters when incorporates VSG control. This threatens the stability and safety of VSG operation, for power electronic based inverters are more vulnerable during the oscillations of current and frequency. Hence, to solve these issues, various enhanced VSG strategies have been constructed to improve its robustness and output performance. In this thesis, the structures and properties of enhanced VSG schemes are fully discussed. The results show that the dynamic properties of VSG during transient periods are enhanced in comparison of that of normal VSG. Modular multilevel converters (MMC) and alternate arm converters (AAC), as the representatives for enhanced topologies of VSC-HVDC system, have more complicated inner structures in comparison with 2/3 level converters. In this thesis, VSG control is applied into MMC/AAC models to strengthen their power and frequency regulation ability. In addition, a four-terminal multi terminal direct current (MTDC) system is incorporated with VSG control to provide primary frequency and voltage response for the grid. The results show that the integration of VSG improves the stability operation and inertia response of MMC/AAC/MTDC systems

Rapid activation of ERK1/2 and AKT in human breast cancer cells by cadmium

Cadmium (Cd), an endocrine disruptor, can induce a variety of signaling events including the activation of ERK1/2 and AKT. In this study, the involvement of estrogen receptors (ER) in these events was evaluated in three human breast caner cell lines, MCF-7, MDA-MB-231, and SK-BR-3. The Cd-induced signal activation patterns in the three cell lines mimicked those exhibited in response to 17β-estradiol. Specifically, treatment of MCF-7 cells, that express ERα, ERβ and GPR30, to 0.5–10 μM Cd for only 2.5 min resulted in transient phosphorylation of ERK1/2. Cd also triggered a gradual increase and sustained activation of AKT during the 60 min treatment period. In SK-BR-3 cells, that express only GPR30, Cd also caused a transient activation of ERK1/2, but not of AKT. In contrast, in MDA-MB-231 cells, that express only ERβ, Cd was unable to cause rapid activation of either ERK1/2 or AKT. A transient phosphorylation of ERα was also observed within 2.5 min of Cd exposure in the MCF-7 cells. While the estrogen receptor antagonist, ICI 182,780, did not prevent the effect of Cd on these signals, specific siRNA against hERα significantly reduced Cd-induced activation of ERK1/2 and completely blocked the activation of AKT. It is concluded that Cd, like estradiol, can cause rapid activation of ERK1/2 and AKT and that these signaling events are mediated by possible interaction with membrane ERα and GPR30, but not ERβ

Preliminary Functional-Structural Modeling on Poplar (Salicaceae)

Poplar is one of the best fast-growing trees in the world, widely used for windbreak and wood product. Although architecture of poplar has direct impact on its applications, it has not been descried in previous poplar models, probably because of the difficulties raised by measurement, data processing and parameterization. In this paper, the functional-structural model GreenLab is calibrated by using poplar data of 3, 4, 5, 6 years old. The data was acquired by simplifying measurement. The architecture was also simplified by classifying the branches into several types (physiological age) using clustering analysis, which decrease the number of parameters. By multi-fitting the sampled data of each tree, the model parameters were identified and the plant architectures at different tree ages were simulated

Analysis of Sediment Transport in the Middle Reach of the Yangtze River after Operation of the Three Gorges Project

Sediment Transport and Morphodynamic