Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixtur...Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixture.How to reduce the position and orientation deviation of workpiece has become a technical problem of improving the processing quality of workpiece.In order to increase machining accuracy,an implementation scheme of fixture system comprehensive errors（FSCE） compensation is proposed.A FSCE parameter model is established by analyzing the influence of contact points on the position and orientation of workpiece.Meanwhile,a parameter identification method for FSCE parameter model is presented by using the 3-2-1 deterministic positioning fixture,which determines the model parameters.Moreover,a FSCE compensation model is formulated to study the compensation value of the cutting position.By using RenishawOMP60 Probe and combining vertical machining centre（SKVH850） equipment with SKY2001 Open CNC System,on-machine verification system（OMVS） is built to measure FSCE successfully.The processing error can be reduced by analyzing the cutting position of the tool with the homogeneous transformation of space coordinate system.Finally,the compensation experiment of real time errors is conducted,and the cylindricality and perpendicularity errors of hole surface are reduced by 30.77% and 28.57%,respectively.This paper provides a new way of realizing the compensation of FCSE,which can improve the machining accuracy of workpiece largely.展开更多
Position-spoofing-based attacks seriously threaten the security of Vehicular Ad Hoc Network(VANET).An effective solution to detect position spoofing is location verification.However,since vehicles move fast and the to...Position-spoofing-based attacks seriously threaten the security of Vehicular Ad Hoc Network(VANET).An effective solution to detect position spoofing is location verification.However,since vehicles move fast and the topology changes quickly in VANET,the static location verification method in Wireless Sensor Network(WSN) is not suitable for VANET.Taking into account the dynamic changing topology of VANET and collusion,we propose a Time-Slice-based Location Verification scheme,named TSLV,to resist position spoofing in VANET.Specifically,TSLV transforms the dynamic topology into static topology by time slice and each time slice corresponds to a verification process.The verifier can implement location verification for the corresponding prover.During the verification process,the verifier first filters out vehicles which provide unreasonably claimed locations,and then uses the Mean Square Error(MSE)-based cluster approach to separate the consistent vehicles by time slice,and uses the consistent set for its verification.In addition,security analysis and simulation show that TSLV can defend against the collusion attack effectively.展开更多
目的利用模拟机验证膀胱充盈与否对于宫颈癌患者体位验证的影响。方法选择经病理证实的宫颈癌患者50例,年龄38~60岁,平均年龄46岁。在其定位时提前40 min喝水憋尿,待到模拟验证时采集3组数据,分别为膀胱排空1次和膀胱充盈2次时X轴(Lat,...目的利用模拟机验证膀胱充盈与否对于宫颈癌患者体位验证的影响。方法选择经病理证实的宫颈癌患者50例,年龄38~60岁,平均年龄46岁。在其定位时提前40 min喝水憋尿,待到模拟验证时采集3组数据,分别为膀胱排空1次和膀胱充盈2次时X轴(Lat,即左右方向)、Y轴(Lng,即头脚方向)、Z轴(Vrt,即高度方向)三个方向上的位移值,并对3组数据进行统计分析。结果试验共获得150组数据,膀胱充盈后两次比较左右(Lat)、头脚(Lng)、高度(Vrt)三个方向上,差异无统计学意义(P均>0.05);比较膀胱排空和充盈的两组数据得出,左右(Lat)和头脚(Lng)方向上差异均有统计学意义(0.168 cm±0.021 cm vs 0.026 cm±0.010 cm,0.464 cm±0.024 cm vs 0.066 cm±0.012 cm;t=5.965、14.51,P<0.05),高度(Vrt)方向上差异无统计学意义(P>0.05)。结论宫颈癌患者放射治疗前模拟机位置验证时膀胱需要充盈。利用模拟机能够准确分析宫颈癌患者膀胱充盈对于调强放射治疗中射野中心的移位影响,减少定位、摆位中误差,是一种可靠的、便捷的位置验证方法。展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50975200)National Key Technologies R & D Programmer of China (Grant No. 2009ZX04014-021)
文摘Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixture.How to reduce the position and orientation deviation of workpiece has become a technical problem of improving the processing quality of workpiece.In order to increase machining accuracy,an implementation scheme of fixture system comprehensive errors（FSCE） compensation is proposed.A FSCE parameter model is established by analyzing the influence of contact points on the position and orientation of workpiece.Meanwhile,a parameter identification method for FSCE parameter model is presented by using the 3-2-1 deterministic positioning fixture,which determines the model parameters.Moreover,a FSCE compensation model is formulated to study the compensation value of the cutting position.By using RenishawOMP60 Probe and combining vertical machining centre（SKVH850） equipment with SKY2001 Open CNC System,on-machine verification system（OMVS） is built to measure FSCE successfully.The processing error can be reduced by analyzing the cutting position of the tool with the homogeneous transformation of space coordinate system.Finally,the compensation experiment of real time errors is conducted,and the cylindricality and perpendicularity errors of hole surface are reduced by 30.77% and 28.57%,respectively.This paper provides a new way of realizing the compensation of FCSE,which can improve the machining accuracy of workpiece largely.
基金supported by National Natural Science Foundation of China under Grant No.60972036
文摘Position-spoofing-based attacks seriously threaten the security of Vehicular Ad Hoc Network(VANET).An effective solution to detect position spoofing is location verification.However,since vehicles move fast and the topology changes quickly in VANET,the static location verification method in Wireless Sensor Network(WSN) is not suitable for VANET.Taking into account the dynamic changing topology of VANET and collusion,we propose a Time-Slice-based Location Verification scheme,named TSLV,to resist position spoofing in VANET.Specifically,TSLV transforms the dynamic topology into static topology by time slice and each time slice corresponds to a verification process.The verifier can implement location verification for the corresponding prover.During the verification process,the verifier first filters out vehicles which provide unreasonably claimed locations,and then uses the Mean Square Error(MSE)-based cluster approach to separate the consistent vehicles by time slice,and uses the consistent set for its verification.In addition,security analysis and simulation show that TSLV can defend against the collusion attack effectively.
文摘目的利用模拟机验证膀胱充盈与否对于宫颈癌患者体位验证的影响。方法选择经病理证实的宫颈癌患者50例,年龄38~60岁,平均年龄46岁。在其定位时提前40 min喝水憋尿,待到模拟验证时采集3组数据,分别为膀胱排空1次和膀胱充盈2次时X轴(Lat,即左右方向)、Y轴(Lng,即头脚方向)、Z轴(Vrt,即高度方向)三个方向上的位移值,并对3组数据进行统计分析。结果试验共获得150组数据,膀胱充盈后两次比较左右(Lat)、头脚(Lng)、高度(Vrt)三个方向上,差异无统计学意义(P均>0.05);比较膀胱排空和充盈的两组数据得出,左右(Lat)和头脚(Lng)方向上差异均有统计学意义(0.168 cm±0.021 cm vs 0.026 cm±0.010 cm,0.464 cm±0.024 cm vs 0.066 cm±0.012 cm;t=5.965、14.51,P<0.05),高度(Vrt)方向上差异无统计学意义(P>0.05)。结论宫颈癌患者放射治疗前模拟机位置验证时膀胱需要充盈。利用模拟机能够准确分析宫颈癌患者膀胱充盈对于调强放射治疗中射野中心的移位影响,减少定位、摆位中误差,是一种可靠的、便捷的位置验证方法。
