Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consider...Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.展开更多
Detecting feature points on the human body in video frames is a key step for tracking human movements. There have been methods developed that leverage models of human pose and classification of pixels of the body imag...Detecting feature points on the human body in video frames is a key step for tracking human movements. There have been methods developed that leverage models of human pose and classification of pixels of the body image. Yet, occlusion and robustness are still open challenges. In this paper, we present an automatic, model-free feature point detection and action tracking method using a time-of-flight camera. Our method automatically detects feature points for movement abstraction. To overcome errors caused by miss-detection and occlusion, a refinement method is devised that uses the trajectory of the feature points to correct the erroneous detections. Experiments were conducted using videos acquired with a Microsoft Kinect camera and a publicly available video set and comparisons were conducted with the state-of-the-art methods. The results demonstrated that our proposed method delivered improved and reliable performance with an average accuracy in the range of 90 %.The trajectorybased refinement also demonstrated satisfactory effectiveness that recovers the detection with a success rate of 93.7 %. Our method processed a frame in an average time of 71.1 ms.展开更多
针对形状不规则复杂面目标多弹瞄准点优化算法计算效率低、稳定性差、优化能力不足的问题,提出一种基于弹药圆概率偏差(Circular Error Probable,CEP)的毁伤概率矩阵库(Damage Probability Matrix Library,DPML)和改进启发式退火优化机...针对形状不规则复杂面目标多弹瞄准点优化算法计算效率低、稳定性差、优化能力不足的问题,提出一种基于弹药圆概率偏差(Circular Error Probable,CEP)的毁伤概率矩阵库(Damage Probability Matrix Library,DPML)和改进启发式退火优化机制的高效瞄准点优化算法(Efficient Aiming Point Optimization Algorithm,EAPOA)。构建多弹瞄准点优化模型时,除考虑目标形状、导弹毁伤能力外,还考虑导弹直接毁伤、间接毁伤和多弹种联合毁伤等复杂因素对目标毁伤效果的影响。提出一种基于DPML的毁伤概率快速估计算法,提升算法优化效率和鲁棒性;设计一种基于候选瞄准点序列化的优化算法框架,并提出基于全局搜索和改进退火机制的启发式优化算法,降低瞄准点组合求解空间大小并提升算法优化能力。通过6个复杂面目标测试用例验证算法性能。研究结果表明,所提的EAPOA相比于增强精英保留策略遗传算法具有更强的优化能力,且平均优化时间仅为其1/5~1/3,在优化收益和计算效率上具有明显优势。展开更多
目的观察火针联合董氏奇穴针刺治疗肩袖损伤的临床疗效及对关节功能及血清前列腺素E_(2)(prostaglandin E_(2),PGE_(2))和转化生长因子-β1(transforming growth factor-β1,TGF-β1)的影响。方法将100例肩袖损伤患者随机分为对照组(50...目的观察火针联合董氏奇穴针刺治疗肩袖损伤的临床疗效及对关节功能及血清前列腺素E_(2)(prostaglandin E_(2),PGE_(2))和转化生长因子-β1(transforming growth factor-β1,TGF-β1)的影响。方法将100例肩袖损伤患者随机分为对照组(50例)和观察组(50例)。对照组予以电针联合董氏奇穴针刺治疗,观察组予以火针联合董氏奇穴针刺治疗。检测视觉模拟量表(visual analog scale,VAS)和美国加利福尼亚大学洛杉矶分校(University of California,Los Angeles,UCLA)肩关节评分、肩关节活动度(range of motion,ROM)及血清PGE_(2)和TGF-β1水平。结果观察组总有效率高于对照组(P<0.05)。治疗后及4周随访时,两组VAS评分及血清PGE_(2)和TGF-β1水平均低于治疗前(P<0.05),且观察组均低于对照组(P<0.05);两组UCLA肩关节评分和肩关节ROM均高于治疗前(P<0.05),且观察组均高于对照组(P<0.05)。4周随访时,两组VAS评分、UCLA肩关节评分、肩关节ROM及血清PGE_(2)和TGF-β1水平与治疗后比较差异无统计系意义(P>0.05)。治疗后血清PGE_(2)、TGF-β1水平与VAS评分呈正相关,与UCLA肩关节评分呈负相关。结论火针和电针联合董氏奇穴针刺治疗肩袖损伤均可缓解疼痛、改善肩关节功能,但火针优于电针,其机制可能与降低血清PGE_(2)和TGF-β1水平有关。展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51635002(Key Program),51605011,51275015)
文摘Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.
文摘Detecting feature points on the human body in video frames is a key step for tracking human movements. There have been methods developed that leverage models of human pose and classification of pixels of the body image. Yet, occlusion and robustness are still open challenges. In this paper, we present an automatic, model-free feature point detection and action tracking method using a time-of-flight camera. Our method automatically detects feature points for movement abstraction. To overcome errors caused by miss-detection and occlusion, a refinement method is devised that uses the trajectory of the feature points to correct the erroneous detections. Experiments were conducted using videos acquired with a Microsoft Kinect camera and a publicly available video set and comparisons were conducted with the state-of-the-art methods. The results demonstrated that our proposed method delivered improved and reliable performance with an average accuracy in the range of 90 %.The trajectorybased refinement also demonstrated satisfactory effectiveness that recovers the detection with a success rate of 93.7 %. Our method processed a frame in an average time of 71.1 ms.
文摘针对形状不规则复杂面目标多弹瞄准点优化算法计算效率低、稳定性差、优化能力不足的问题,提出一种基于弹药圆概率偏差(Circular Error Probable,CEP)的毁伤概率矩阵库(Damage Probability Matrix Library,DPML)和改进启发式退火优化机制的高效瞄准点优化算法(Efficient Aiming Point Optimization Algorithm,EAPOA)。构建多弹瞄准点优化模型时,除考虑目标形状、导弹毁伤能力外,还考虑导弹直接毁伤、间接毁伤和多弹种联合毁伤等复杂因素对目标毁伤效果的影响。提出一种基于DPML的毁伤概率快速估计算法,提升算法优化效率和鲁棒性;设计一种基于候选瞄准点序列化的优化算法框架,并提出基于全局搜索和改进退火机制的启发式优化算法,降低瞄准点组合求解空间大小并提升算法优化能力。通过6个复杂面目标测试用例验证算法性能。研究结果表明,所提的EAPOA相比于增强精英保留策略遗传算法具有更强的优化能力,且平均优化时间仅为其1/5~1/3,在优化收益和计算效率上具有明显优势。
文摘目的观察火针联合董氏奇穴针刺治疗肩袖损伤的临床疗效及对关节功能及血清前列腺素E_(2)(prostaglandin E_(2),PGE_(2))和转化生长因子-β1(transforming growth factor-β1,TGF-β1)的影响。方法将100例肩袖损伤患者随机分为对照组(50例)和观察组(50例)。对照组予以电针联合董氏奇穴针刺治疗,观察组予以火针联合董氏奇穴针刺治疗。检测视觉模拟量表(visual analog scale,VAS)和美国加利福尼亚大学洛杉矶分校(University of California,Los Angeles,UCLA)肩关节评分、肩关节活动度(range of motion,ROM)及血清PGE_(2)和TGF-β1水平。结果观察组总有效率高于对照组(P<0.05)。治疗后及4周随访时,两组VAS评分及血清PGE_(2)和TGF-β1水平均低于治疗前(P<0.05),且观察组均低于对照组(P<0.05);两组UCLA肩关节评分和肩关节ROM均高于治疗前(P<0.05),且观察组均高于对照组(P<0.05)。4周随访时,两组VAS评分、UCLA肩关节评分、肩关节ROM及血清PGE_(2)和TGF-β1水平与治疗后比较差异无统计系意义(P>0.05)。治疗后血清PGE_(2)、TGF-β1水平与VAS评分呈正相关,与UCLA肩关节评分呈负相关。结论火针和电针联合董氏奇穴针刺治疗肩袖损伤均可缓解疼痛、改善肩关节功能,但火针优于电针,其机制可能与降低血清PGE_(2)和TGF-β1水平有关。
