虚拟网格服务工作流的调度算法研究

对虚拟网格服务工作流的调度算法进行了研究,提出了最小计算时间(MCT)、最小传输时间(MTT)、最小执行时间(MET)3种虚拟网格服务工作流的调度算法.在满足给定假设的情况下,MCT、MTT、MET的调度分别能保证目标工作流获得最小计算时间、最小传输时间、最小执行时间.在描述了调度算法之后,证明了算法调度的正确性.对几种算法的调度性能进行实验模拟,并分析和比较了它们的实现代价和时间、空间复杂度,从而给出各算法的适用情况.     

A methodology for developing service in virtual manufacturing environment

Developing product related services in the context of virtual manufacturing environment to support manufacturing industry is considered as one of the main challenges for industrialised countries to improve their competiveness in the years to come. This is a complex servitization process that needs supports of appropriate models, methods and tools. This paper presents a methodological approach for the creation of the manufacturing service and service system along the engineering phases of a service life cycle. The proposed approach is developed under the frame of a FP7 European Integrated Project MSEE (Manufacturing Service Ecosystem). The methodology relates and federates a set of models, methods and tools through a structured approach. The experimentations of the methodology in industrial pilots showed that it allows the gain of time and consistency in a complex manufacturing servitization project.     

Towards the development of a framework to create a virtual organisation breeding environment in the mould and die sector

The effective creation of Virtual Enterprises emerges after the development of: (i) a new working culture and (ii) a computer-enabled infrastructure supporting inter-operation of companies. These developments are facilitated if the potential partners belong to a Virtual Organisation Breeding Environment (VBE). This paper describes a framework to create and support the life cycle of Virtual Enterprises operating (relying on a VBE) in the mould and die sector. The proposed framework is called AmbianCE and it is the result of a 5-year research project in the field of Collaborative Network Organisations. The AmbianCE framework has been validated in a Brazilian VBE called Virfebras. A peculiar characteristic of Virfebras is that many of its members are competitors.     

Implementing the CORBA GIOP in a high-performance object request broker environment

The success of the Object Management Group's General Inter-ORB Protocol (GIOP) is leading to the desire to deploy GIOP in an ever-wider range of application areas, many of which are significantly more demanding than traditional areas in terms of performance. The well-known performance limitations of present day GIOP-based object request brokers (ORBs) are therefore increasingly being seen as a problem. To help address this problem, this paper discusses a GIOP implementation which has high performance and quality of service support as explicit goals. The implementation, which is embedded in a research ORB called Gopi, is modular and extensible in nature and includes novel optimization techniques which should be separately portable to other ORB environments. This paper focuses on the message protocol aspects of Gopi's GIOP implementation; higher layer issues such as marshalling and operation demultiplexing are not covered in detail. Figures are provided which position Gopi's GIOP performance against comparable ORBs. The paper also discusses some of the design decisions that have been made in the development of the GIOP protocol in the light of our implementation experience. Received: May 2000 / Accepted: December 2000     

普适计算环境下的设备请求代理模型*

为了给普适计算环境提供一个统一的应用架构和模式,本文从普适计算研究现状出发,通过借鉴对象请求代理技术,提出了设备请求代理模型,建立了设备基件的远程映射管理和统一调度机制,有效降低了普适计算环境下应用程序的开发难度和兼容传统应用程序。     

Dynamic forecast scheduling algorithm for virtual machine placement in cloud computing environment

In most cloud computing platforms, the virtual machine quotas are seldom changed once initialized, although the current allocated resources are not efficiently utilized. The average utilization of cloud servers in most datacenters can be improved through virtual machine placement optimization. How to dynamically forecast the resource usage becomes a key problem. This paper proposes a scheduling algorithm called virtual machine dynamic forecast scheduling (VM-DFS) to deploy virtual machines in a cloud computing environment. In this algorithm, through analysis of historical memory consumption, the most suitable physical machine can be selected to place a virtual machine according to future consumption forecast. This paper formalizes the virtual machine placement problem as a bin-packing problem, which can be solved by the first-fit decreasing scheme. Through this method, for specific virtual machine requirements of applications, we can minimize the number of physical machines. The VM-DFS algorithm is verified through the CloudSim simulator. Our experiments are carried out on different numbers of virtual machine requests. Through analysis of the experimental results, we find that VM-DFS can save 17.08 % physical machines on the average, which outperforms most of the state-of-the-art systems.     

云制造环境下面向多目标优化的虚拟资源调度研究

为解决云制造环境下虚拟资源调度存在的算法求解效率不高、模型建立缺乏考虑任务间关系约束和任务间及子任务间的物流时间及成本因素等不足,构建了兼顾交货期时间最小化、服务成本最低化、服务质量最优化为目标的多目标虚拟资源调度模型;采用一种基于项目阶段的双链编码方式进行编码,并提出自适应交叉与变异概率公式,以避免交叉、变异概率始终不变导致算法效率下降与过早收敛的问题;在此基础上利用基于项目阶段的多种交叉变异策略相结合的改进遗传算法进行求解,保证了算法的全局与局部搜索性能。实例结果表明,相比于传统的模型与算法,该模型适用性更强,改进的遗传算法在求解效率、准确度与稳定性方面均有较大提高。     

Single machine due date assignment scheduling problem with customer service level in fuzzy environment

Due date assignment scheduling problems with deterministic and stochastic parameters have been studied extensively in recent years. In this paper, we consider a single machine due date assignment scheduling problem with uncertain processing times and general precedence constraint among the jobs. The processing times of the jobs are assumed to be fuzzy numbers. We first propose an optimal polynomial time algorithm for the problem without precedence constraints among jobs. Then, we show that if general precedence constraint is involved, the problem is NP-hard. Finally, we show that if the precedence constraint is a tree or a collection of trees, the problem is still polynomially solvable.     

Interactive scheduling for mobile multimedia service in M2M environment

Computational load of motion estimation in advanced video coding (AVC) standard is significantly high and its more true for HDTV sequences. In this paper, video processing algorithm is mapped onto a learning method to improve machine to machine (M2M) architecture, namely, the parallel reconfigurable computing (PRC) architecture, which consists of multiple units, First, we construct a directed acyclic graph (DAG) to represent the video coding algorithms comprising motion estimation. In the future trillions of devices are connected (M2M) together to provide services and that time power management would be a challenge. Computation aware scheme for different machine is reduced by dynamically scheduling usage of multi-core processing environment for video sequence depending up complexity of the video. And different video coding algorithm is selected depending upon the nature of the video. Simulation results show the effectiveness of the proposed method.     

Cloud broker proposal based on multicriteria decision-making and virtual infrastructure migration

The adoption of infrastructure as a Service (IaaS) is a reality for academic, industrial, and governmental institutions. Cloud tenants request dynamically provisioned virtual infrastructures (VIs) tailored to their application requirements, detailing not only the virtual compute/storage resources but also the network components, topology, and services. The creation of a large number of cloud providers came along with the widespread use of VIs. The selection of an appropriate provider is a challenging task due to the diversity of the IaaS market and formally is a multicriteria analysis (NP-hard). Notwithstanding the provider selection complexity, the mobility of VI-hosted applications is limited due to the optimization anchors introduced by providers. Although the existing IaaS cloud brokers can indicate a hosting provider, they lack on conceptual and technical skills to migrate a VI and all its internal components between providers. This work enhances the state-of-the-art on IaaS cloud brokerage by proposing virtual infrastructure multicriteria allocation and migration–based broker (VIMAM), which performs a multicriteria analysis of providers and VI migration. VIMAM is driven by an analytic hierarchy process (AHP) to select an IaaS provider, offering a set of predefined weighting schemas to represent distinct tenant perspectives. Moreover, to migrate a VI, VIMAM takes into account the virtual machines, containers, switches, and other topology elements. In addition to discussing the AHP ranking weights and frequency of providers selection, the experimental analysis details the implementation of an OpenStack and Docker–based prototype for VI migration.     

E-commerce transactions in a virtual environment: virtual transactions

E-commerce is a fundamental method of doing business, such that for a firm to say it is trading at all in the modern market-place it must have some element of on-line presence. Coupled with this is the explosion of the “population” of Massively Multiplayer On-line Role Playing Games and other shared virtual environments. Many suggest this will lead to a further dimension of commerce: virtual commerce. We discuss here the issues, current roadblocks and present state of an e-commerce transaction carried out completely within a virtual environment; a virtual transaction. Although technically such transactions are in a sense trivial, they raise many other issues in complex ways thus making V-transactions a highly interesting cross-disciplinary issue. We also discuss the social, ethical and regulatory implications for the virtual communities in these environments of such v-transactions, how their implementation affects the nature and management of a virtual environment, and how they represent a fundamental merging of the real and virtual worlds for the purpose of commerce. We highlight the minimal set of features a v-transaction capable virtual environment requires and suggest a model of how in the medium term they could be carried out via a methodology we call click-through, and that the developers of such environments will need to take on the multi-modal behavior of their users, as well as elements of the economic and political sciences in order to fully realize the commercial potential of the v-transaction.     

On scheduling in a GT environment

Traditional research in scheduling has concentrated on developing optimal and optional tending heuristic algorithms for n x m job shop and flow shop problems. Relatively no work has been conducted in the area of scheduling within a GT cell. This paper examines the GT cell environment from a scheduling perspective in relation to a job and flow shop, and presents a modified approach to scheduling within a GT cell that implicitly takes advantage of common setups and part family coding structures.     

应用托管环境下的虚拟机优化调度方法

在面对云服务中典型的应用托管需求时,现有的基础设施即服务IaaS大多采用应用无关的方式进行虚拟机调度,无法针对类型不同的应用托管需求调整调度策略,从而会产生虚拟机集群的负载倾斜及资源利用率不高的情况,甚至会影响所托管的应用。针对上述问题,提出了一种应用托管环境下的虚拟机优化调度方法,通过对所托管应用的分析和物理资源的监控,以贪心方式实现虚拟机周期性的调度策略。实际项目中的应用托管实例表明,该虚拟机调度方法可有效减少所使用的物理服务器数量,并提高物理服务器资源利用率。     

Experimenting with nonintrusive motion capture in a virtual environment

A growing number of promising applications requires recognizing human posture and motion. Conventional techniques require us to attach foreign objects to the body, which in some applications is disturbing or even impossible. New, nonintrusive motion capture approaches are called for. The well-known shape-from-silhouette technique for understanding 3D shapes could also be effective for human bodies. We present a novel technique for model-based motion capture that uses silhouettes extracted from multiple views. A 3D reconstruction of the performer can be computed from a silhouette with a technique known as volume intersection. We can recover the posture by fitting a model of the human body to the reconstructed volume. The purpose of this work is to test the effectiveness of this approach in a virtual environment by investigating the precision of the posture and motion obtained with various numbers and arrangements of stationary cameras. An average 1% position error has been obtained with five cameras.     

Controlling a camera in a virtual environment

image-based control or visual servoing approach. It consists of positioning a camera according to the information perceived in the image. This is thus a very intuitive approach of animation. To be able to react automatically to modifications of the environment, we also considered the introduction of constraints into the control. This approach is thus adapted to highly reactive contexts (virtual reality, video games). Numerous examples dealing with classic problems in animation are considered within this framework and presented in this paper. Published online: 19 July 2001     

Conditioned suppression in a virtual environment

Virtual environments (VEs) provide an inexpensive way of conducting ecologically valid psychological research. The present study used a VE to demonstrate conditioned suppression, a behavioral model of anxiety, in a first-person perspective video game. During operant training, participants learned to shoot crates to find gold bars and thus score points in the game. Next, during Pavlovian conditioning, a colored light (i.e., conditioned stimulus: CS+) was followed by a white noise unconditioned stimulus (US) while a different colored light (CS−) was not paired with the US. Probe trials in a final testing phase were then used to assess suppression. We found significant suppression of accurate responding (shots hitting the designated targets) during the presence of the CS+ relative to the CS−, both in terms of total hits and hits as a proportion of total shots. Importantly, this effect emerged despite the overall level of operant responding being undiminished during the CS+. Our findings are consistent with related studies examining human behavior in real environments, and demonstrate the potential of VEs in combination with a modestly aversive CS to allow a detailed behavioral profile of anxiety to emerge.     

A virtual reality keyboard with realistic haptic feedback in a fully immersive virtual environment

This study presents a 3D virtual reality (VR) keyboard system with realistic haptic feedback. The system uses two five-fingered data gloves to track finger positions and postures, uses micro-speakers to create simulated vibrations, and uses a head-mounted display (HMD) for 3D display. When users press a virtual key in the VR environment, the system can provide realistic simulated key click haptic feedback to users. The results of this study show that the advantages of the haptic VR keyboard are that users can use it when wearing HMDs (users do not need to remove HMDs to use the VR keyboard), the haptic VR keyboard can pop-up display at any location in the VR environments (users do not need to go to a specific location to use an actual physical keyboard), and the haptic VR keyboard can be used to provide realistic key click haptic feedback (which other studies have shown enhances user performance). The results also show that the haptic VR keyboard system can be used to create complex vibrations that simulate measured vibrations from a real keyboard and enhance keyboard interaction in a fully immersive VR environment.     

Aperiodic servers in a deadline scheduling environment

A real-time system may have tasks with soft deadlines, as well as hard deadlines. While earliest-deadline-first scheduling is effective for hard-deadline tasks, applying it to soft-deadline tasks may waste schedulable processor capacity or sacrifice average response time. Better average response time may be obtained, while still guaranteeing hard deadlines, with an aperiodic server. Three scheduling algorithms for aperiodic servers are described, and schedulability tests are derived for them. A simulation provides performance data for these three algorithms on random aperiodic tasks. The performances of the deadline aperiodic servers are compared with those of several alternatives, including background service, a deadline polling server, and rate-monotonic servers, and with estimates based on the M/M/1 queueing model. This adds to the evidence in support of deadline scheduling,versus fixed priority scheduling.     

Effectiveness of a multidevice 3D virtual environment application to train car service maintenance procedures

This paper reports a study which demonstrates the advantages of using virtual-reality-based systems for training automotive assembly tasks. Sixty participants were randomly assigned to one of the following three training experiences to learn a car service procedure: (1) observational training through video instruction; (2) an experiential virtual training and trial in a CAVE; and (3) an experiential virtual training and trial through a portable 3D interactive table. Results show that virtual trained participants, after the training, can remember significantly better (p < .05) the correct execution of the steps compared to video-trained trainees. No significant differences were identified between the experiential groups neither in terms of post-training performances nor in terms of proficiency, despite differences in the interaction devices. The relevance of the outcomes for the automotive fields and for the designers of virtual training applications are discussed in light of the outcomes, particularly that virtual training experienced through a portable device such as the interactive table can be effective, as can training performed in a CAVE. This suggests the possibility for automotive industries to invest in advanced portable hardware to deliver effectively long-distance programs of training for car service operators placed all over the world.