How commercial involvement affects open source projects: three case studies on issue reporting

Whereas most research on Internetware has focused on new technologies for keeping track of a changing Internet,little attention has been paid to the software development process.A large portion of the software running the Internet is open source software.Open source software is developed both by volunteers and commercial companies,often jointly.Companies get involved in open source projects for commercial reasons,and bring with them a commercial software development process.Thus,it is important to understand how commercial involvement affects the software development process of open source projects.This article presents case studies of three open source application servers that are being developed jointly by a volunteer community and one primary software company.We are interested in better understanding developer behavior,specifically task distribution and performance,based on whether the developer is an external contributor,e.g.,a volunteer working in their spare time,or a commercial developer from inside the primary backing company who is being paid for their time.To achieve this,we look at issue reporting as an example of commercial involvement in open source projects.In particular,we investigate the distribution of tasks among volunteers and commercial developers by studying the source of reported issues and quantify the task performance on user experience via the issue resolution speed.We construct measures based on historical records in issue tracking repositories.Our results show that,with intensified commercial involvement,the majority of issue reporting tasks would be undertaken by commercial developers,and issue resolution time would be reduced,implying a better user experience.We hope our methods and results provide practical insights for designing an efficient hybrid development process in the Internetware environment.     

Study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam

In this paper, a simplified model of the bistable piezoelectric cantilever beam with magnets is established, and the potential energy of the bistable system is analyzed. We have proposed the bistable L-shaped beam structure, which has the same geometry dimensions of the bistable straight beam in the first time. The comparative study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam plays an important role in exploring excellent piezoelectric generator.The experiment structure includes the base layer and the piezoelectric layer. The harmonic excitation is given to the system.Theoretical analysis results show that the potential energy function of the system has two obvious steady potential wells. In addition, the depth of the upper potential well is different from that of the lower potential well when the gravity potential energy is considered. Experimental results demonstrate that the power generation for the straight beam is better than that of the horizontally placed L-shaped beam when the excitation amplitude is 450 m V. There is the existence that the energy harvesting capacity of the bistable L-shaped beam is better than that of the bistable straight beam when the excitation amplitude is 400 m V.Furthermore, the power generation of the bistable L-shaped beam with the upper potential well is obviously better than that of the bistable L-shaped beam with the lower potential well. In addition, comparing with the straight beam, the dynamic response of the bistable L-shaped beam is more complex when the external excitation frequency is changed. It is also observed that the distance between the magnets has the obvious influence on the dynamic response of the bistable system. It is very effective to select the appropriate distance between the magnets to improve the power generation of the bistable energy harvester under the fixed excitation conditions.     

我国能源管理体制与能源产业发展的理性思考

从能源与国民经济的关系入手,回顾了我国能源管理体制的变迁,通过与其他国家的能源管理体制的对比,分析了我国现行能源管理体制对能源生产和消费的影响,提出了完善我国能源管理体制的建议.通过进一步完善能源管理体制,使能源的生产和消费具有系统的管理和监督部门,促进能源产业的健康发展.     

Nonlinear transient responses of rotating twisted FGM cylindrical panels

This paper develops a new structure dynamic model to investigate nonlinear transient responses of the rotating blade made of functionally graded material(FGM). The rotating blade is simplified as a rotating FGM cylindrical panel with a presetting angle and a twist angle. The geometric nonlinearity effects are taken into account in the strain-displacement relationships, which are derived by Green strain tensor. Based on the first-order piston theory and the first-order shear deformation theory, the equations of motion for the rotating twisted FGM cylindrical panel are acquired by means of Hamilton principle and Galerkin method.Backward Differentiation Formula(BDF) and Runge-Kutta Algorithm are used to solve the nonlinear equations of motion for the system. The effects of four pulse load conditions on the system subjected to the internal pulse load or the external pulse load are fully discussed. A detailed parametric analysis is performed by considering the effects of the rotating speed, volume fraction index and temperature.     

多轴机床几何误差建模与补偿技术的研究

基于多体系统运动学理论,分析了多轴机床的拓扑结构关系及各个运动轴的误差项元素,建立了多轴机床运动空间的几何误差模型。基于Labview开发了误差补偿平台,进行了误差补偿试验。通过对比补偿前后各轴线性定位误差和补偿前后的数控加工代码,验证了所建立的误差模型的正确性,且该补偿方法是可行的。     

Multi-pulse orbits dynamics of composite laminated piezoelectric rectangular plate

The multi-pulse orbits and chaotic dynamics of a simply supported laminated composite piezoelectric rectangular plate under combined parametric excitation and transverse excitation are studied in detail. It is assumed that different layers are perfectly bonded to each other with piezoelectric actuator patches embedded. The nonlinear equations of motion for the laminated composite piezoelectric rectangular plate are derived from von Karman-type equation and third-order shear deformation plate theory of Reddy...     

Precision forming machine with rolling plate cross wedge rolling

Roller cross wedge rolling (CWR) machines have high rigidity, but sector dies are difficult to process. Plate CWR machines have low rigidity and need large floor space, but plate dies are easy to process. Neither roller CWR machine nor plate CWR machine can produce larger workpieces. Based on the above conclusions, this paper presents the mechanical principle of the precision forming machine with rolling plate CWR. Then, its design principle and machine construction are presented. There are a top press roller above the upper sliding plate and a bottom press roller under the lower sliding plate. The press rollers make rolling contact with the sliding plates. The plate dies are mounted on the upper and lower sliding plates, respectively. Furthermore, the axes of both press rollers and centerline of workpiece always keep in the identical vertical plane during forming process. These make the machine retain advantages of high rigidity for roller CWR machine and simpleness of manufacturing dies for plate CWR machine, and abandon defects of poor rigidity for plate CWR machine and difficulty of manufacturing dies for roller CWR machine. Moreover, the machine can produce larger workpieces.     

Development of self-adjusting hydraulic machine for combination forming of upsetting and extruding

In the paper a self-adjusting hydraulic machine for combination forming of upsetting and extruding is systematacially presented in terms of mechanical principle, design principle, machine construction, design of the key components and working routine. The machine is designed with the following features: The lower movable beam is adjusted by the ejecting cylinder, the upper upsetting beam is reset by the backstroke slide rods, and the upsetting cylinders communicate with the gas-liquid accumulators. These fe...     

一种动态的客户端负载均衡机制

互联网应用的并发用户数量不仅多变并且这种变化常常不可预测.将系统容量配置为固定值的惯用做法在面临多变的请求时常常会导致两种结果,一种是因为配置过低而引起用户的不满,另一种则因为配置过高而造成计算资源的浪费.而通过运用云架构按需提供、按使用收费的能力,系统具有了实时地按需配置计算资源的能力.然而静态的客户端负载均衡方法作为一种主要的负载均衡技术很难适应云架构条件下更加易变的集群结构.本文提出了一种动态的客户端负载均衡机制.通过引入分布式的集群视图更新、控制流等技术,该机制在保持客户端负载均衡机制分布式、可伸缩性强的基础上,又为集群节点的动态加入与退出和负载均衡策略的动态调整提供了有效的支持.同时,本文分析了该机制在一个开源JEE应用服务器PKUAS中的关键实现问题,并通过实验从多方面验证了该机制的有效性.     

机械制造业信息化的回顾与探讨

机械制造业是为国民经济、国家安全提供装备,为人民物质文化生活提供丰富产品的制造业。它在国民经济中无论GDP所占的比例还是对其他产业的感应系数都是很大的。机械制造业是国民经济持续发展的基础,是工业化、现代化建设的发动机和动力源,是在国际竞争中取胜的法宝,是技术进步的主要舞台,是提高人均收入的财源,是国家安全的保障,是发展现代文明的物质基础。没有先进的机械制造业不断、持续地武装和提升各产业部门的装备和生产运行水平,实现对环境友好的可持续发展就谈不上什么现代化。所以人们对机械制造业的关注是不言而喻的。机械制造…