Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-sl...Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can＇t satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm（GA） and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device.展开更多
The investments of the electro-hydraulic servo system of the mold non-sinusoidal oscillator are great, the modification ratio of the mechanical type is unable to be adjusted online, and some continuous casters suffer ...The investments of the electro-hydraulic servo system of the mold non-sinusoidal oscillator are great, the modification ratio of the mechanical type is unable to be adjusted online, and some continuous casters suffer from server resonance during the casting. A mold non-sinusoidal oscillation mechanism driven by servomotor is proposed and the prototype is produced in the lab, the investment is low and the modification ratio is can be adjusted online, and the stability problem is studied. At first the dynamics model of the servomotor non-sinusoidal oscillation is established, and the kinematics differential function is deduced. Furthermore, based on the harmonic balance method, the eigenvalues of the system are solved; the criterion of the stability of the system is put forward. In addition, the eigenvalues and harmonic with different oscillating parameters are analyzed. Analytical results show that the real parts of the eigenvalues are positive, the system will be unstable, and the resonance will occur when the positive real parts of the eigenvalues are extremum. A foundation is established for solving the running smooth problem and next application of this mechanism.展开更多
目的通过Meta分析,综合分析运动后心率恢复(HRR)与心源性猝死(SCD)之间的关系。方法基于PubMed、Embase和Web of Science数据库,进行截至2024年1月2日的文献检索。队列研究关注于HRR和SCD间的风险关系,通过风险比(HR)及95%可信区间(CI)...目的通过Meta分析,综合分析运动后心率恢复(HRR)与心源性猝死(SCD)之间的关系。方法基于PubMed、Embase和Web of Science数据库,进行截至2024年1月2日的文献检索。队列研究关注于HRR和SCD间的风险关系,通过风险比(HR)及95%可信区间(CI)进行评估。统计学分析采用Stata 12.0软件。结果纳入6项研究。固定效应模型(I^(2)=41.8%,P=0.112)的汇总结果显示:与心率恢复慢相比,心率恢复快人群发生SCD风险更低(HR=0.74,95%CI:0.64~0.86,P<0.001)。大多数亚组分析中都观察到了持续结果。排除一项研究并不影响总体结果[HR(95%CI):0.66(0.55,0.79)~0.76(0.65,0.88)]。Egger检验未发现明显的发表偏倚(P=0.059)。结论心率恢复较慢会增加普通人群发生SCD的风险。因此,HRR可能是临床实践中预防SCD的一个潜在靶点。展开更多
随着智能信息社会的不断演进以及智慧城市建设的推进,电子设备的定位准确性和可靠性需求日益突显,特别是在万物互联的背景下,对定位精度和定位质量的要求变得更加迫切。无源定位技术因隐蔽性强、功耗低、不易被感知与干扰等诸多优点被...随着智能信息社会的不断演进以及智慧城市建设的推进,电子设备的定位准确性和可靠性需求日益突显,特别是在万物互联的背景下,对定位精度和定位质量的要求变得更加迫切。无源定位技术因隐蔽性强、功耗低、不易被感知与干扰等诸多优点被广泛应用于各个领域,尤其近年来,通感一体化(Integrated Sensing and Communication, ISAC)、机器学习、环境反向散射以及智能反射面的引入与发展,为无源定位在6G中的应用提供了新的契机。基于此,阐述了无源定位技术特点及分类;按照参数化的分类方式总结梳理无源定位方法及误差影响因素;讨论了多参数融合无源定位方案与优势;展望了无源定位技术在6G新愿景下典型的应用场景、潜在技术、挑战及未来研究方向。展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51475139)
文摘Dynamical Joining of the solid-state metal is the key technology to realize endless hot rolling. The heating and laser welding method both require long joining time. Based on super deformation method, a 7-bar and 2-slider mechanism was developed in Japan, and the joining time is less than 0.5 s, however the length of each bar are not reported and this mechanism is complex. A relatively simple 6-bar and 1-slider mechanism is put forward, which can realize the shearing and extrusion motion of the top and bottom blades with a speed approximately equal to the speed of the metal plates. In order to study the kinematics property of the double blades, based on complex vector method, the multi-rigid-body model is built, and the displacement and speed functions of the double blades, the joining time and joining thickness are deduced, the kinematics analysis shows that the initial parameters can＇t satisfy the joining process. Hence, optimization of this mechanism is employed using genetic algorithm（GA） and the optimization parameters of this mechanism are obtained, the kinematics analysis show that the joining time is less than 0.1 s, the joining thickness is more than 80% of the thickness of the solid-state metal, and the horizontal speeds of the blades are improved. A new mechanism is provided for the joining of the solid-state metal and a foundation is laid for the design of the device.
基金Supported by National Natural Science Foundation of China and Baosteel Group Co.Ltd.(Grant No.U1260203)Natural Science Foundation Steel and Iron Foundation of Hebei Province,China(Grant No.F2013203291)+1 种基金Doctor Startup Foundation of Hebei University of Science and Technology,China(Grant No.QD201247)Foundation of Hebei University of Science and Technology,China(Grant No.XL201004)
文摘The investments of the electro-hydraulic servo system of the mold non-sinusoidal oscillator are great, the modification ratio of the mechanical type is unable to be adjusted online, and some continuous casters suffer from server resonance during the casting. A mold non-sinusoidal oscillation mechanism driven by servomotor is proposed and the prototype is produced in the lab, the investment is low and the modification ratio is can be adjusted online, and the stability problem is studied. At first the dynamics model of the servomotor non-sinusoidal oscillation is established, and the kinematics differential function is deduced. Furthermore, based on the harmonic balance method, the eigenvalues of the system are solved; the criterion of the stability of the system is put forward. In addition, the eigenvalues and harmonic with different oscillating parameters are analyzed. Analytical results show that the real parts of the eigenvalues are positive, the system will be unstable, and the resonance will occur when the positive real parts of the eigenvalues are extremum. A foundation is established for solving the running smooth problem and next application of this mechanism.
文摘目的通过Meta分析,综合分析运动后心率恢复(HRR)与心源性猝死(SCD)之间的关系。方法基于PubMed、Embase和Web of Science数据库,进行截至2024年1月2日的文献检索。队列研究关注于HRR和SCD间的风险关系,通过风险比(HR)及95%可信区间(CI)进行评估。统计学分析采用Stata 12.0软件。结果纳入6项研究。固定效应模型(I^(2)=41.8%,P=0.112)的汇总结果显示:与心率恢复慢相比,心率恢复快人群发生SCD风险更低(HR=0.74,95%CI:0.64~0.86,P<0.001)。大多数亚组分析中都观察到了持续结果。排除一项研究并不影响总体结果[HR(95%CI):0.66(0.55,0.79)~0.76(0.65,0.88)]。Egger检验未发现明显的发表偏倚(P=0.059)。结论心率恢复较慢会增加普通人群发生SCD的风险。因此,HRR可能是临床实践中预防SCD的一个潜在靶点。
文摘随着智能信息社会的不断演进以及智慧城市建设的推进,电子设备的定位准确性和可靠性需求日益突显,特别是在万物互联的背景下,对定位精度和定位质量的要求变得更加迫切。无源定位技术因隐蔽性强、功耗低、不易被感知与干扰等诸多优点被广泛应用于各个领域,尤其近年来,通感一体化(Integrated Sensing and Communication, ISAC)、机器学习、环境反向散射以及智能反射面的引入与发展,为无源定位在6G中的应用提供了新的契机。基于此,阐述了无源定位技术特点及分类;按照参数化的分类方式总结梳理无源定位方法及误差影响因素;讨论了多参数融合无源定位方案与优势;展望了无源定位技术在6G新愿景下典型的应用场景、潜在技术、挑战及未来研究方向。
