In cyberspace security,the privacy in location-based services(LBSs) becomes more critical. In previous solutions,a trusted third party(TTP) was usually employed to provide disturbance or obfuscation,but it may become ...In cyberspace security,the privacy in location-based services(LBSs) becomes more critical. In previous solutions,a trusted third party(TTP) was usually employed to provide disturbance or obfuscation,but it may become the single point of failure or service bottleneck. In order to cope with this drawback,we focus on another important class,establishing anonymous group through short-range communication to achieve k-anonymity with collaborative users. Along with the analysis of existing algorithms,we found users in the group must share the same maximum anonymity degree,and they could not ease the process of preservation in a lower one. To cope with this problem,we proposed a random-QBE algorithm to put up with personalized anonymity in user collaboration algorithms,and this algorithm could preserve both query privacy and location privacy. Then we studied the attacks from passive and active adversaries and used entropy to measure user's privacy level. Finally,experimental evaluations further verify its effectiveness and efficiency.展开更多
A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative ...A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative entries that can occur in A whenever Ak≤0. Finally, we give a necessity and sufficiency condition for A2≤0.展开更多
Objective： To study the influences of head/neck ratio and femoral antetorsion on the safe-zone of operative acetabular orientations, which meets the criteria for desired range of motion （ROM） for activities of dail...Objective： To study the influences of head/neck ratio and femoral antetorsion on the safe-zone of operative acetabular orientations, which meets the criteria for desired range of motion （ROM） for activities of daily living in total hip arthroplasty （THA）. Methods： A three-dimensional generic, parametric and kinematic simulation module of THA was developed to analyze the cup safe-zone and the optimum combination of cup and neck antetorsion. A ROM of flexion ≥ 120°, internal rotation ≥ 45° at 90° flexion, extension ≥ 30° and external rotation ≥ 40° was defined as the criteria for desired ROM for activities of daily living. The cup safe-zone was defined as the area that fulfills all the criteria of desired ROM before the neck impinged on the liner of the cup. For a fixed stemneck （CCD）-angle of 130°, theoretical safe-zones fulfilling the desired ROM were investigated at different general headneck ratios （GR=2, 2.17, 2.37, 2.61 and 2.92） and femoral anteversions （FA=0°, 10°, 20° and 30°）. Results： Large GRs greatly increased the size of safezones and when the CCD-angle was 130°, a GR〉2.37 could further increase the size of safe-zones. There was a complexinterplay between the orientation angles of the femoral and acetabular components. When the CCD-angle was 130°, the optimum relationship between operative acetabular anteversion （OA） and femoral antetorsion （FA） could be estimated by the formula： OA=-0.80×FA＋47.06, and the minimum allowable operative acetabular inclination （OImin） would be more than 2 10.5 ×GR^-2255. Conclusions： Large GRs greatly increase the size of safe-zones and it is recommended that the GR be more than 2.37 so as to extend the acceptable range of error that surgeons cannot avoid completely during operation. As to the optimum operative acetabular inclination （OI）, surgeons need to make a decision combining with other factors, including stress distribution, soft tissue and cup wear conditions, as well as patients＇ individual situations and demands. The data obtained from this study and the module of THA can be used to assist surgeons to choose and implant appropriate implants.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.61472097)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20132304110017)+1 种基金the Natural Science Foundation of Heilongjiang Province of China (Grant No.F2015022)the Fujian Provincial Key Laboratory of Network Security and Cryptology Research Fund (Fujian Normal University) (No.15003)
文摘In cyberspace security,the privacy in location-based services(LBSs) becomes more critical. In previous solutions,a trusted third party(TTP) was usually employed to provide disturbance or obfuscation,but it may become the single point of failure or service bottleneck. In order to cope with this drawback,we focus on another important class,establishing anonymous group through short-range communication to achieve k-anonymity with collaborative users. Along with the analysis of existing algorithms,we found users in the group must share the same maximum anonymity degree,and they could not ease the process of preservation in a lower one. To cope with this problem,we proposed a random-QBE algorithm to put up with personalized anonymity in user collaboration algorithms,and this algorithm could preserve both query privacy and location privacy. Then we studied the attacks from passive and active adversaries and used entropy to measure user's privacy level. Finally,experimental evaluations further verify its effectiveness and efficiency.
基金Supported by Shanxi Natural Science Foundation(20011006)
文摘A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative entries that can occur in A whenever Ak≤0. Finally, we give a necessity and sufficiency condition for A2≤0.
基金This work was supported by grants from Science Foundation from Sci-Tech Committee of Zhejiang Province （No. 2009C33144）, Science Foundation from Sci-Tech Committee of Wenzhou City （No. Y20070043） and Science Foundation from Sci-Tech Committee of Rui＇an City （No. 20082088）.
文摘Objective： To study the influences of head/neck ratio and femoral antetorsion on the safe-zone of operative acetabular orientations, which meets the criteria for desired range of motion （ROM） for activities of daily living in total hip arthroplasty （THA）. Methods： A three-dimensional generic, parametric and kinematic simulation module of THA was developed to analyze the cup safe-zone and the optimum combination of cup and neck antetorsion. A ROM of flexion ≥ 120°, internal rotation ≥ 45° at 90° flexion, extension ≥ 30° and external rotation ≥ 40° was defined as the criteria for desired ROM for activities of daily living. The cup safe-zone was defined as the area that fulfills all the criteria of desired ROM before the neck impinged on the liner of the cup. For a fixed stemneck （CCD）-angle of 130°, theoretical safe-zones fulfilling the desired ROM were investigated at different general headneck ratios （GR=2, 2.17, 2.37, 2.61 and 2.92） and femoral anteversions （FA=0°, 10°, 20° and 30°）. Results： Large GRs greatly increased the size of safezones and when the CCD-angle was 130°, a GR〉2.37 could further increase the size of safe-zones. There was a complexinterplay between the orientation angles of the femoral and acetabular components. When the CCD-angle was 130°, the optimum relationship between operative acetabular anteversion （OA） and femoral antetorsion （FA） could be estimated by the formula： OA=-0.80×FA＋47.06, and the minimum allowable operative acetabular inclination （OImin） would be more than 2 10.5 ×GR^-2255. Conclusions： Large GRs greatly increase the size of safe-zones and it is recommended that the GR be more than 2.37 so as to extend the acceptable range of error that surgeons cannot avoid completely during operation. As to the optimum operative acetabular inclination （OI）, surgeons need to make a decision combining with other factors, including stress distribution, soft tissue and cup wear conditions, as well as patients＇ individual situations and demands. The data obtained from this study and the module of THA can be used to assist surgeons to choose and implant appropriate implants.
