Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduc...Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.展开更多
This paper discusses the problem that constructing a curve to satisfy the given endpoint constraints and chord-length parameters. Based on the research of Lu, the curve construction method for the entire tangent angle...This paper discusses the problem that constructing a curve to satisfy the given endpoint constraints and chord-length parameters. Based on the research of Lu, the curve construction method for the entire tangent angles region （α0, α1）∈（-r, r）×（-r, r） is given. Firstly, to ensure the weights are always positive, the three characteristics of cubic rational Bezier curve is proved, then the segment construction idea for the other tangent angles are presented in view of the three characteristics. The curve constructed with the new method satisfies the endpoint constraint and chord-length parameters, it＇s G1 continuous in every segment curve, and the shapes of the curve are well.展开更多
目的系统评价多区正向离焦镜片(DIMS)与角膜塑形镜(Ortho-K)控制近视的效果。方法计算机检索PubMed、Embase、Cochrane Library、Web of Science、CBM、WanFang Data和CNKI数据库,搜集与研究目的相关的临床研究,检索时限均为2000年1月至...目的系统评价多区正向离焦镜片(DIMS)与角膜塑形镜(Ortho-K)控制近视的效果。方法计算机检索PubMed、Embase、Cochrane Library、Web of Science、CBM、WanFang Data和CNKI数据库,搜集与研究目的相关的临床研究,检索时限均为2000年1月至2024年6月。由2名研究者独立筛选文献、提取资料并评价纳入研究的偏倚风险后,采用RevMan 5.3软件进行Meta分析。结果共纳入8个随机对照试验(RCT)和7个队列研究。Meta分析结果显示,Ortho-K和DIMS眼轴控制效果[MD=-0.18,95%CI(-0.21,-0.15),P<0.01;MD=-0.21,95%CI(-0.27,-0.15),P<0.01]优于单光镜片;Ortho-K组眼轴一年增长量低于DIMS组[MD=-0.06,95%CI(-0.08,-0.04),P<0.01]。结论当前证据表明,Ortho-K和DIMS的近视控制效果优于单光镜片,OrthoK的近视控制效果优于DIMS,但优势不明显。受纳入研究数量和质量的限制,上述结论尚待更多高质量研究予以验证。展开更多
基金This work was financially supported by National Hi-Tech R&D Program of China (863 Program)( Grant No2006AA04Z127)New Century Excellent Talents (NCET) of Tianjin University,2005
文摘Towed cable systems are frequently used in marine measurements where the length of the towed cable varies during launch and recovery. In this paper a novel method for modeling variable length cable systems is introduced based on the finite segment formulation. The variable length of the towed cable is described by changing the length of the segment near the towing point and by increasing or decreasing the number of the discrete segments of the cable. In this way, the elastic effects of the cable can be easily handled since geometry and material properties of each segment are kept constant. Experimental results show that the dynamic behavior of the towed cable is consistent between the model and the physical cable. Results show that the model provides numerical efficiency and simulation accuracy for the variable length towed system.
基金Supported by Shandong Province Higher Educational Science and Technology Program(No.J12LN34)Shandong Ji'nan College and Institute Independent Innovation Project(No.201303011,No.201303021,No.201303016)
文摘This paper discusses the problem that constructing a curve to satisfy the given endpoint constraints and chord-length parameters. Based on the research of Lu, the curve construction method for the entire tangent angles region （α0, α1）∈（-r, r）×（-r, r） is given. Firstly, to ensure the weights are always positive, the three characteristics of cubic rational Bezier curve is proved, then the segment construction idea for the other tangent angles are presented in view of the three characteristics. The curve constructed with the new method satisfies the endpoint constraint and chord-length parameters, it＇s G1 continuous in every segment curve, and the shapes of the curve are well.
