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A study on the changes of dynamic feature code when fixing bugs: towards the benefits and costs of Python dynamic features

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Science China(Information Sciences) 2018年第1期61卷 169-186页

作者： Zhifei CHEN Wanwangying MA Wei LIN Lin CHEN Yanhui LI Baowen XU State Key Laboratory for Novel Software Technology Nanjing University

dynamic features in programming languages support the modification of the execution status at runtime, which is often considered helpful in rapid development and prototyping. However, it was also reported that some dynamic feature code tends to be change-prone or error-prone. We present the first study that analyzes the changes of dynamic feature code and the roles of dynamic features in bug-fix activities for the Python language. We used an AST-based differencing tool to capture fine-grained source code changes from 17926 bug-fix commits in 17 Python projects. Using this data, we conducted an empirical study on the changes of dynamic feature code when fixing bugs in Python. First, we investigated the characteristics of dynamic feature code changes, by comparing the changes between dynamic feature code and non-dynamic feature code when fixing bugs, and comparing dynamic feature changes between bug-fix and non-bugfix activities. Second, we explored 226 bug-fix commits to investigate the motivation and behaviors of dynamic feature changes when fixing bugs. The study results reveal that(1) the changes of dynamic feature code are significantly related to bug-fix activities rather than non-bugfix activities;(2) compared with non-dynamic feature code, dynamic feature code is inserted or updated more frequently when fixing bugs;(3) developers often insert dynamic feature code as type checks or attribute checks to fix type errors and attribute errors;(4) the misuse of dynamic features introduces bugs in dynamic feature code, and the bugs are often fixed by adding a check or adding an exception handling. As a benefit of this paper, we gain insights into the manner in which developers and researchers handle the changes of dynamic feature code when fixing bugs.

关键词： Python fine-grained code changes change behaviors dynamic features bug fixing

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dynamic feature of flavonoids content in different organs of larch （Larix gmelinii）

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Journal of Forestry Research 2005年第2期16卷 89-92页

作者： WANGWen-jie LIXue-ying ZUYuan-gang KeyLaboratoryofForestPlantEcology NortheastForestryUniversityHarbin150040P.R.China

Flavonoids in plants is very important in its ecological role and economicvalue. The dynamic features of flavonoids content in different organs of larch (Larix gmelinii) atdifferent light and temperature conditions were investigated in this study. Results showed that theorder of flavonoids content in different organs from high to low was 7.78% (stem bark) > 2.79%(leaves) > 1.72% (branches) > 1.19% (stem xylem)and different organs had a great seasonal variationin flavonoids content, but the change of flavonoids content at different temperature was not obviousin different organs., The content of flavonoids in barck had, a positive correlation withtemperature (R^2=0.75), but that in other organs had slight variation with the change oftemperatures. For all the tested organs, the flavonoids content in summer and autumn wasapproximately 3-4 times higher than in spring and winter. This is attributed to the great stressfrom environmental physical variables such as UV radiation, high temperature that induce theaccumulation of flavonoids. The flavonoid content of sun leaves was evidently higher than that ofshade leaves, and leaves at upper part of canopy had a higher flavonoids content compared with thatat other parts. This result indicates that sun radiation could improve flavonoids production inleaves (R^2=0.76). The flavonoids may actively evolve in plant defenses to environmental stress,protecting larch from the damage of high temperature and radiation, and its main function isdifferent in different organs.

关键词： larix gmelinii flavonoids dynamic features environmental stress

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超空泡射弹的结构优化与稳定性分析

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哈尔滨工程大学学报（英文版） 2023年第3期22卷 527-544页

作者：王康健伍友利郝双鹏荣光 Aviation Engineering College Air Force Engineering UniversityXian 710038China National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyNanjing 210094China

Stability is the key issue for kinetic-energy supercavitating *** previous work established a six degrees of freedom(DOF)dynamic model for supercavitating ***,the projectile’s structure did not meet our current design specifications(its sailing distance could reach 100 m at an initial speed of 500 m/s).The emphasis of this study lies in optimizing the projectile’s ***,a program was developed to optimize the projectile’s structure to achieve an optimal design or the largest sailing *** program is a working optimal method based on the genetic algorithm(GA).Additionally,the convergence standard and population producing strategy were improved,which greatly elevated the calculation speed and *** meet design specifications,the improved GA was combined with the 6DOF model,which establishes a dynamic optimization *** new projectile’s structure was obtained by solving this ***,the new structures’dynamic features were compared with the ideals proposed in this *** criterion of stability,which is called weakened self-stability,was redefined based on the *** weakened self-stability is the optimal stability for an actual kinetic projectile motion,and it is instructive for the design of supercavitating projectiles in the future.

关键词： Structural optimization Self-stability tendency Supercavitating projectile dynamic features Projectile stability

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Numerical study on the flow features of U-beam inertial separator

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2002年第4期3卷 8-11页

作者：陈丽华樊建人岑可法 College of Mechanical and Energy Engineering Zhejiang UniversityHangzhouChina

Detailed parametric study of three-dimensional gas-particle multiphase flow characteristics in U-beam tube bundle inertial separators was conducted by numerical simulation. The carrier phase was treated in the Eulerian frame, the particles were tracked in the Lagrangian frame, and particle-wall collision was considered. Simulation carried out at different inflow rate and mass loading ratios revealed the pressure losses in the separators, velocity field of the gas phase, and the trajectories of particles. The study results revealed the multiphase flow-dynamic features of the separators, and the relationship between separator pressure losses and different inlet velocity. The numerical simulation can provide basis both for optimal design of impacting-inertial separator used in circulating fluidized bed boiler; and for study of gas-particle multiphase circumfluence flow.

关键词： U-beam inertial separator Numerical simulation dynamic features

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