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3 results on '"Nana Chang"'

1. Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with High Proportion of Distributed Generations

Author

Nana Chang, Guobing Song, Zhongxue Chang, Yuping Zheng, and Xingang Yang

Subjects
Inverse-time backup protection (ITBP), distributed generation (DG), positive sequence fault component (PS-FC) voltage, unified characteristic equation, adaptive coordination, Production of electric energy or power. Powerplants. Central stations, TK1001-1841, Renewable energy sources, TJ807-830
Abstract

The setting work of backup protection using steady-state current is tedious, and mismatches occasionally occur due to the increased proportion of distributed generations (DGs) connected to the power grid. Thus, there is a practical need to study a backup protection technology that does not require step-by-step setting and can be adaptively coordinated. This paper proposes an action sequence adaptive to fault positions that uses only positive sequence fault component (PSFC) voltage. Considering the influence of DGs, the unified time dial setting can be obtained by selecting specific points. The protection performance is improved by using the adjacent upstream and down-stream protections to meet the coordination time interval in the case of metallic faults at the near- and far-ends of the line. Finally, the expression and implementation scheme for inverse-time backup protection (ITBP) based on the unified characteristic equation is given. Simulation results show that this scheme can adapt to DG penetration scenarios and can realize the adaptive coordination of multi-level relays.

Published
2024
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2. Change-Based Test Script Maintenance for Android Apps

Author

Yu Pei, Linzhang Wang, Subrota K. Mondal, Nana Chang, and Xuandong Li

Subjects
Test script, business.industry, Computer science, Maintenance actions, False positive paradox, Graphical user interface testing, Android (operating system), Software engineering, business, Maintenance engineering, Humanoid robot, Graphical user interface
Abstract

In regression GUI testing for Android apps, test scripts often fail due to changes to, rather than faults in, those apps. To avoid such false positives while still retaining the value of the old test scripts as much as possible, programmers need an automatic way to maintain the tests after the corresponding GUI has evolved. In this paper, we propose the CHATEM approach to automate GUI test script maintenance for Android apps. Taking as input the models for the GUIs of the base and updated version app and the original test scripts, CHATEM automatically extracts the changes between the two GUIs and generates maintenance actions for each change, which are then combined to form the maintenance actions for affected test scripts. In an experimental evaluation on 16 Android apps, CHATEM was able to automatically maintain the test scripts so that overall more than 95% of the remaining behaviors tested before are still tested, and almost 80% of the reusable test actions are retained in the result tests.

Published
2018

3. ATOM: Automatic Maintenance of GUI Test Scripts for Evolving Mobile Applications

Author

Linzhang Wang, Yu Pei, Nana Chang, Wang Yan, Li Xiao, Xuandong Li, and Haohua Huang

Subjects
Programming language, Computer science, business.industry, 020207 software engineering, 02 engineering and technology, computer.software_genre, Maintenance engineering, Test script, Scripting language, 020204 information systems, Regression testing, 0202 electrical engineering, electronic engineering, information engineering, Mobile telephony, Android (operating system), Software engineering, business, computer, Humanoid robot, Graphical user interface
Abstract

The importance of regression testing in assuring the integrity of a program after changes is well recognized. One major obstacle in practicing regression testing is in maintaining tests that become obsolete due to evolved program behavior or specification. For mobile apps, the problem of maintaining obsolete GUI test scripts for regression testing is even more pressing. Mobile apps rely heavily on the correct functioning of their GUIs to compete on the market and provide good user experiences. But on the one hand, GUI tests break easily when changes happen to the GUI, On the other hand, mobile app developers often need to fight for a tight feedback loop and are left with limited time for test maintenance. In this paper, we propose a novel approach, called ATOM, to automatically maintain GUI test scripts of mobile apps for regression testing. ATOM uses an event sequence model to abstract possible event sequences on a GUI and a delta ESM to abstract the changes made to the GUI. Given both models as input, ATOM automatically updates the test scripts written for a base version app to reflect the changes. In an experiment with 22 versions from 11 production Android apps, ATOM updated all the test scripts affected by the version change, the updated scripts achieve over 80% of the coverage by the original scripts on the base version app, all except one set of updated scripts preserve over 60% of the actions in the original test scripts.

Published
2017

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