Background In virtual environments(VEs),users can explore a large virtual scene through the viewpoint operation of a head-mounted display(HMD)and movement gains combined with redirected walking technology.The existing...Background In virtual environments(VEs),users can explore a large virtual scene through the viewpoint operation of a head-mounted display(HMD)and movement gains combined with redirected walking technology.The existing redirection methods and viewpoint operations are effective in the horizontal direction;however,they cannot help participants experience immersion in the vertical direction.To improve the immersion of upslope walking,this study presents a virtual climbing system based on passive haptics.Methods This virtual climbing system uses the tactile feedback provided by sponges,a commonly used flexible material,to simulate the tactile sense of a user's soles.In addition,the visual stimulus of the HMD,the tactile feedback of the flexible material,and the operation of the user's walking in a VE combined with redirection technology are all adopted to enhance the user's perception in a VE.In the experiments,a physical space with a hard-flat floor and three types of sponges with thicknesses of 3,5,and 8cm were utilized.Results We recruited 40 volunteers to conduct these experiments,and the results showed that a thicker flexible material increases the difficulty for users to roam and walk within a certain range.Conclusion The virtual climbing system can enhance users'perception of upslope walking in a VE.展开更多
Simulating the softness property of object is quite a challenge in virtual reality system. A novel softness display system was developed based on the principle of deformable length of elastic element control （DLEEC）...Simulating the softness property of object is quite a challenge in virtual reality system. A novel softness display system was developed based on the principle of deformable length of elastic element control （DLEEC）. In the system, the equivalent stiffness of the device is adjustable, and is inversely proportional to the third power of the deformable length of elastic beam. PD position control is employed to guarantee the accurate softness display. The softness of the virtual objects in large scale can be felt with the softness display device. Compared with other haptic devices, the device is passive and exert the react force only when the operator ＂actively touch＂ the virtual objects. The stability of the softness display system was analyzed. It was theoretical proved that the system satisfied the criteria of wide impedance range ＂Z-width＂, and the performance was superior to an active system. The experimental results were presented.展开更多
This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency sh...This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency shift and path difference,the virtual path difference is calculated from the measured value of Doppler frequency shift by means of mean value correction.Then,under the assumption that the target is moving at a constant speed along a straight line,two coaxial virtual double base arrays are constructed by using the moving track of the moving target based on the method of fixed period time difference.On this basis,the moving distance of the moving target can be calculated by using the ratio relationship between the frequency difference and the radial distance between the two adjacent detection points in the middle of the array,and the linear solution of the two double base path difference positioning equations.At this point,the relative coordinate position of the moving target can be obtained by directly using the linear solution of the double base path difference positioning equation again.展开更多
该文将Energy Plus建筑能耗仿真与实际被动式建筑现场调研、能耗监测相结合,以青岛地区某被动房为案例,开展了包括现场调研、仿真结果验证、节能潜力分析和敏感性分析等内容的实验项目。实验结果表明,该实验方法可操作性强,仿真结果与...该文将Energy Plus建筑能耗仿真与实际被动式建筑现场调研、能耗监测相结合,以青岛地区某被动房为案例,开展了包括现场调研、仿真结果验证、节能潜力分析和敏感性分析等内容的实验项目。实验结果表明,该实验方法可操作性强,仿真结果与实测数据吻合度高,被动式建筑的节能效果得到有效验证。案例被动式建筑全供暖及供冷能耗指标分别为14.08 k Wh/m^(2)·a和8.37 k Wh/m^(2)·a,相比传统建筑全年节能55.26%,其中空调节能率高达56.95%;外墙、外窗保温、遮阳系统等被动措施是主要节能来源,节能占比分别为26.54%、23.58%和23.97%;灰色关联分析显示,外墙传热系数对全年能耗的敏感度最高。展开更多
基金the National Key R&D Program of China(2018YFB1404100)National Natural Science Foundation of China(62072405)Zhejiang Provincial Natural Science Foundation of China(LGF20F020017).
文摘Background In virtual environments(VEs),users can explore a large virtual scene through the viewpoint operation of a head-mounted display(HMD)and movement gains combined with redirected walking technology.The existing redirection methods and viewpoint operations are effective in the horizontal direction;however,they cannot help participants experience immersion in the vertical direction.To improve the immersion of upslope walking,this study presents a virtual climbing system based on passive haptics.Methods This virtual climbing system uses the tactile feedback provided by sponges,a commonly used flexible material,to simulate the tactile sense of a user's soles.In addition,the visual stimulus of the HMD,the tactile feedback of the flexible material,and the operation of the user's walking in a VE combined with redirection technology are all adopted to enhance the user's perception in a VE.In the experiments,a physical space with a hard-flat floor and three types of sponges with thicknesses of 3,5,and 8cm were utilized.Results We recruited 40 volunteers to conduct these experiments,and the results showed that a thicker flexible material increases the difficulty for users to roam and walk within a certain range.Conclusion The virtual climbing system can enhance users'perception of upslope walking in a VE.
基金Supported by the National Basic Research and Development Program （No. 2002CB312102） and the National Natural Science Foundation of China （No. 60643007, 60475034）.
文摘Simulating the softness property of object is quite a challenge in virtual reality system. A novel softness display system was developed based on the principle of deformable length of elastic element control （DLEEC）. In the system, the equivalent stiffness of the device is adjustable, and is inversely proportional to the third power of the deformable length of elastic beam. PD position control is employed to guarantee the accurate softness display. The softness of the virtual objects in large scale can be felt with the softness display device. Compared with other haptic devices, the device is passive and exert the react force only when the operator ＂actively touch＂ the virtual objects. The stability of the softness display system was analyzed. It was theoretical proved that the system satisfied the criteria of wide impedance range ＂Z-width＂, and the performance was superior to an active system. The experimental results were presented.
文摘This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency shift and path difference,the virtual path difference is calculated from the measured value of Doppler frequency shift by means of mean value correction.Then,under the assumption that the target is moving at a constant speed along a straight line,two coaxial virtual double base arrays are constructed by using the moving track of the moving target based on the method of fixed period time difference.On this basis,the moving distance of the moving target can be calculated by using the ratio relationship between the frequency difference and the radial distance between the two adjacent detection points in the middle of the array,and the linear solution of the two double base path difference positioning equations.At this point,the relative coordinate position of the moving target can be obtained by directly using the linear solution of the double base path difference positioning equation again.
文摘该文将Energy Plus建筑能耗仿真与实际被动式建筑现场调研、能耗监测相结合,以青岛地区某被动房为案例,开展了包括现场调研、仿真结果验证、节能潜力分析和敏感性分析等内容的实验项目。实验结果表明,该实验方法可操作性强,仿真结果与实测数据吻合度高,被动式建筑的节能效果得到有效验证。案例被动式建筑全供暖及供冷能耗指标分别为14.08 k Wh/m^(2)·a和8.37 k Wh/m^(2)·a,相比传统建筑全年节能55.26%,其中空调节能率高达56.95%;外墙、外窗保温、遮阳系统等被动措施是主要节能来源,节能占比分别为26.54%、23.58%和23.97%;灰色关联分析显示,外墙传热系数对全年能耗的敏感度最高。
