Cloud computing represents a novel computing model in the contemporary technology world. In a cloud system, the com- puting power of virtual machines （VMs） and network status can greatly affect the completion time o...Cloud computing represents a novel computing model in the contemporary technology world. In a cloud system, the com- puting power of virtual machines （VMs） and network status can greatly affect the completion time of data intensive tasks. How- ever, most of the current resource allocation policies focus only on network conditions and physical hosts. And the computing power of VMs is largely ignored. This paper proposes a comprehensive resource allocation policy which consists of a data intensive task scheduling algorithm that takes account of computing power of VMs and a VM allocation policy that considers bandwidth between storage nodes and hosts. The VM allocation policy includes VM placement and VM migration algorithms. Related simulations show that the proposed algorithms can greatly reduce the task comple- tion time and keep good load balance of physical hosts at the same time.展开更多
In order to improve efficiency of virtual enterprise, a manufacturing grid and multilevel manufacturing system of virtual enterprise is built up. When selecting member enterprises and task assignment based on the manu...In order to improve efficiency of virtual enterprise, a manufacturing grid and multilevel manufacturing system of virtual enterprise is built up. When selecting member enterprises and task assignment based on the manufacturing grid, key activities are assigned to the suitable critical member enterprises by task decomposition, enterprise node searching and characteristic matching of manufacturing resources according to the characteristic matching strategy. By task merger, some ordinary activities are merged with corresponding key activities and assigned to corresponding critical member enterprises. However, the other ordinary activities are assigned to the related ordinary member enterprises with enterprise node searching and characteristic matching of manufacturing resources. Finally, an example of developing the artificial hip joint in the virtual enterprise is used to demonstrate that efficiency of the virtual enterprise is improved by using the manufacturing grid and the proposed strategies for member enterprise selection and task assignment.展开更多
We developed a Virtual Shopping Test with three different task levels for assessment of daily cognitive function using virtual reality technology. The objective of present study was to investigate the difference on ta...We developed a Virtual Shopping Test with three different task levels for assessment of daily cognitive function using virtual reality technology. The objective of present study was to investigate the difference on task performance, brain activation and subjective assessment in relation to the difficulty levels of the tasks. Subjects were asked to buy specific 2 items in Task 1, 4 items in Task 2, and 6 items in Task 3 at a virtual mall. The tasks and questionnaires were conducted on 10 convalescent brain-damaged patients and 6 healthy young adults. Hemodynamic changes in the prefrontal cortex (PFC) during activation due to the tasks were examined using functional near-infrared spectroscopy. As the result, the mean total time was significantly longer for the patients than for healthy subjects. PFC showed a greater response for related Task 2 than Task 1 in shopping and moving phase in patient group. The patients evaluated Tasks 1 and 2 are more difficult and bring more psychological load than healthy adults subjectively. That is, although the healthy adults did not show large difference in their task performances as well as PFC responses, they can evaluate the differences between three task levels, subjectively, while which could not be for the patients means that patients could not distinguish the difference of the tasks, subjectively. The results suggest that 4-item shopping task might be enough difficulty level that causes brain activation for the brain-damaged patients.展开更多
The key realization techniques of virtual assembly process planning （VAPP） system are analyzed, including virtual assembly model, real-time collision detection, automatic constraint recognition algorithm, cable harn...The key realization techniques of virtual assembly process planning （VAPP） system are analyzed, including virtual assembly model, real-time collision detection, automatic constraint recognition algorithm, cable harness assembly process planning and visual assembly process plan at the workshop. A virtual assembly model based on hierarchical assembly task list （HATL） is put forward, in which assembly tasks are defined to express component assembling operations and are sequentially and hierarchically organized according to different subassemblies, which can perfectly model the construction process of product, And a multi-layer automatic geometry constraint recognition algorithm of how to identify assmbly constraint relations in the virtual environment is proposed, then a four-layer collision detection algorithm is discussed. A VAPP system is built and some simple mechanical assemblies are used to illustrate the feasibility of the proposed method and algorithms.展开更多
The multi-modal information presentation, integrated into the virtual environment （VE）, has potential for stimulating different senses, improving the user＇s impression of immersion, and increasing the amount of inf...The multi-modal information presentation, integrated into the virtual environment （VE）, has potential for stimulating different senses, improving the user＇s impression of immersion, and increasing the amount of information that is accepted and processed by the user＇s perception system. The increase of the useful feedback information may reduce the user＇s cognitive load, thus enhancing the user＇s efficiency and performance while interacting with VEs. This paper presents our creation of a multi-sensory virtual assembly environment （VAE） and the evaluation of the effects of multi-sensory feedback on the usability. The VAE brings together complex technologies such as constraint-based assembly simulation, optical motion tracking technology, and real-time 3D sound generation technology around a virtual reality workbench and a common software platform. The usability evaluation is in terms of its three attributes： efficiency of use, user satisfaction, and reliability. These are addressed by using task completion times （TCTs）, questionnaires, and human performance error rates （HPERs）, respectively. Two assembly tasks have been used to perform the experiments, using sixteen participants. The outcomes showed that the multi-sensory feedback could improve the usability. They also indicated that the integrated feedback offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback （visual or auditory） or no feedback. The participants＇ comments demonstrated that nonrealistic or inappropriate feedback had negative effects on the usability, and easily made them feel frustrated. The possible reasons behind the outcomes are also analysed by using a unifying human computer interaction framework. The implications, concluded from the outcomes of this work, can serve as useful guidelines for improving VE system design and implementation.展开更多
提出了一种基于M u lti-A gen t的虚拟维修训练系统(VM TS)结构框架,整个系统分别由主控A gen t、仿真A gen t、和接口A gen t3个具有交互作用的A gen t组成,从而将虚拟维修训练系统的开发转化为一个多A gen t系统的设计与开发。基于多A...提出了一种基于M u lti-A gen t的虚拟维修训练系统(VM TS)结构框架,整个系统分别由主控A gen t、仿真A gen t、和接口A gen t3个具有交互作用的A gen t组成,从而将虚拟维修训练系统的开发转化为一个多A gen t系统的设计与开发。基于多A gen t的框架结构可实现受训者的智能模型及虚拟训练场景中虚拟物体的行为模型,从而可以提高VM TS的健壮性和可重用性。基于A gen t的概念模型实现了A gen t之间的交互和协作,并介绍了主控A gen t和仿真A gen t的具体实现方法。展开更多
基金supported by the National Natural Science Foundation of China(6120235461272422)the Scientific and Technological Support Project(Industry)of Jiangsu Province(BE2011189)
文摘Cloud computing represents a novel computing model in the contemporary technology world. In a cloud system, the com- puting power of virtual machines （VMs） and network status can greatly affect the completion time of data intensive tasks. How- ever, most of the current resource allocation policies focus only on network conditions and physical hosts. And the computing power of VMs is largely ignored. This paper proposes a comprehensive resource allocation policy which consists of a data intensive task scheduling algorithm that takes account of computing power of VMs and a VM allocation policy that considers bandwidth between storage nodes and hosts. The VM allocation policy includes VM placement and VM migration algorithms. Related simulations show that the proposed algorithms can greatly reduce the task comple- tion time and keep good load balance of physical hosts at the same time.
文摘In order to improve efficiency of virtual enterprise, a manufacturing grid and multilevel manufacturing system of virtual enterprise is built up. When selecting member enterprises and task assignment based on the manufacturing grid, key activities are assigned to the suitable critical member enterprises by task decomposition, enterprise node searching and characteristic matching of manufacturing resources according to the characteristic matching strategy. By task merger, some ordinary activities are merged with corresponding key activities and assigned to corresponding critical member enterprises. However, the other ordinary activities are assigned to the related ordinary member enterprises with enterprise node searching and characteristic matching of manufacturing resources. Finally, an example of developing the artificial hip joint in the virtual enterprise is used to demonstrate that efficiency of the virtual enterprise is improved by using the manufacturing grid and the proposed strategies for member enterprise selection and task assignment.
文摘We developed a Virtual Shopping Test with three different task levels for assessment of daily cognitive function using virtual reality technology. The objective of present study was to investigate the difference on task performance, brain activation and subjective assessment in relation to the difficulty levels of the tasks. Subjects were asked to buy specific 2 items in Task 1, 4 items in Task 2, and 6 items in Task 3 at a virtual mall. The tasks and questionnaires were conducted on 10 convalescent brain-damaged patients and 6 healthy young adults. Hemodynamic changes in the prefrontal cortex (PFC) during activation due to the tasks were examined using functional near-infrared spectroscopy. As the result, the mean total time was significantly longer for the patients than for healthy subjects. PFC showed a greater response for related Task 2 than Task 1 in shopping and moving phase in patient group. The patients evaluated Tasks 1 and 2 are more difficult and bring more psychological load than healthy adults subjectively. That is, although the healthy adults did not show large difference in their task performances as well as PFC responses, they can evaluate the differences between three task levels, subjectively, while which could not be for the patients means that patients could not distinguish the difference of the tasks, subjectively. The results suggest that 4-item shopping task might be enough difficulty level that causes brain activation for the brain-damaged patients.
文摘The key realization techniques of virtual assembly process planning （VAPP） system are analyzed, including virtual assembly model, real-time collision detection, automatic constraint recognition algorithm, cable harness assembly process planning and visual assembly process plan at the workshop. A virtual assembly model based on hierarchical assembly task list （HATL） is put forward, in which assembly tasks are defined to express component assembling operations and are sequentially and hierarchically organized according to different subassemblies, which can perfectly model the construction process of product, And a multi-layer automatic geometry constraint recognition algorithm of how to identify assmbly constraint relations in the virtual environment is proposed, then a four-layer collision detection algorithm is discussed. A VAPP system is built and some simple mechanical assemblies are used to illustrate the feasibility of the proposed method and algorithms.
基金This work was supported in part by EPSRC(No.GR/M69333/01(P)).
文摘The multi-modal information presentation, integrated into the virtual environment （VE）, has potential for stimulating different senses, improving the user＇s impression of immersion, and increasing the amount of information that is accepted and processed by the user＇s perception system. The increase of the useful feedback information may reduce the user＇s cognitive load, thus enhancing the user＇s efficiency and performance while interacting with VEs. This paper presents our creation of a multi-sensory virtual assembly environment （VAE） and the evaluation of the effects of multi-sensory feedback on the usability. The VAE brings together complex technologies such as constraint-based assembly simulation, optical motion tracking technology, and real-time 3D sound generation technology around a virtual reality workbench and a common software platform. The usability evaluation is in terms of its three attributes： efficiency of use, user satisfaction, and reliability. These are addressed by using task completion times （TCTs）, questionnaires, and human performance error rates （HPERs）, respectively. Two assembly tasks have been used to perform the experiments, using sixteen participants. The outcomes showed that the multi-sensory feedback could improve the usability. They also indicated that the integrated feedback offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback （visual or auditory） or no feedback. The participants＇ comments demonstrated that nonrealistic or inappropriate feedback had negative effects on the usability, and easily made them feel frustrated. The possible reasons behind the outcomes are also analysed by using a unifying human computer interaction framework. The implications, concluded from the outcomes of this work, can serve as useful guidelines for improving VE system design and implementation.
文摘提出了一种基于M u lti-A gen t的虚拟维修训练系统(VM TS)结构框架,整个系统分别由主控A gen t、仿真A gen t、和接口A gen t3个具有交互作用的A gen t组成,从而将虚拟维修训练系统的开发转化为一个多A gen t系统的设计与开发。基于多A gen t的框架结构可实现受训者的智能模型及虚拟训练场景中虚拟物体的行为模型,从而可以提高VM TS的健壮性和可重用性。基于A gen t的概念模型实现了A gen t之间的交互和协作,并介绍了主控A gen t和仿真A gen t的具体实现方法。
