The numbers of beam positions(BPs)and time slots for beam hopping(BH)dominate the latency of LEO satellite communications.Aiming at minimizing the number of BPs subject to a predefined requirement on the radius of BP,...The numbers of beam positions(BPs)and time slots for beam hopping(BH)dominate the latency of LEO satellite communications.Aiming at minimizing the number of BPs subject to a predefined requirement on the radius of BP,a low-complexity user density-based BP design scheme is proposed,where the original problem is decomposed into two subproblems,with the first one to find the sparsest user and the second one to determine the corresponding best BP.In particular,for the second subproblem,a user selection and smallest BP radius algorithm is proposed,where the nearby users are sequentially selected until the constraint of the given BP radius is no longer satisfied.These two subproblems are iteratively solved until all the users are selected.To further reduce the BP radius,a duplicated user removal algorithm is proposed to decrease the number of the users covered by two or more BPs.Aiming at minimizing the number of time slots subject to the no co-channel interference(CCI)constraint and the traffic demand constraint,a low-complexity CCI-free BH design scheme is proposed,where the BPs having difficulty in satisfying the constraints are considered to be illuminated in priory.Simulation results verify the effectiveness of the proposed schemes.展开更多
BACKGROUND Neuroendoscopy is a very useful technique to Chronic Subdural Hematoma(CSH).But how to achieve the goal of treatment more minimally invasive?AIM To develop a simple,fast and accurate preoperative planning m...BACKGROUND Neuroendoscopy is a very useful technique to Chronic Subdural Hematoma(CSH).But how to achieve the goal of treatment more minimally invasive?AIM To develop a simple,fast and accurate preoperative planning method in our way for endoscopic surgery of patients with CSH.METHODS From June 2018 to May 2020,forty-two patients with CSH,admitted to our hospital,were performed endoscopic minimally invasive surgery;computed tomography(CT)imaging was employed to locate the intracerebral hematoma and select the appropriate endoscopic approach before the endoscopic surgery.The clinical data and treatment efficacy were analyzed.RESULTS According to the learning of CT scanning images,the surgeon can accurately design the best minimally invasive neuroendoscopic surgical approach and realize the precise positioning and design of the drilling site of the skull and the size of the bone window,so as to provide the most effective operation space with the smallest bone window.In this group,the average operation time was only about 1 h,and the clearance rate of hematoma was about 95%.CONCLUSION Patients with CSH can achieve good therapeutic effect by using our way to positioning and design to assist the operation of CSH according to CT scan and image,and our way is very useful and necessary.展开更多
基金supported in part by National Key Research and Development Program of China under Grant 2021YFB2900404。
文摘The numbers of beam positions(BPs)and time slots for beam hopping(BH)dominate the latency of LEO satellite communications.Aiming at minimizing the number of BPs subject to a predefined requirement on the radius of BP,a low-complexity user density-based BP design scheme is proposed,where the original problem is decomposed into two subproblems,with the first one to find the sparsest user and the second one to determine the corresponding best BP.In particular,for the second subproblem,a user selection and smallest BP radius algorithm is proposed,where the nearby users are sequentially selected until the constraint of the given BP radius is no longer satisfied.These two subproblems are iteratively solved until all the users are selected.To further reduce the BP radius,a duplicated user removal algorithm is proposed to decrease the number of the users covered by two or more BPs.Aiming at minimizing the number of time slots subject to the no co-channel interference(CCI)constraint and the traffic demand constraint,a low-complexity CCI-free BH design scheme is proposed,where the BPs having difficulty in satisfying the constraints are considered to be illuminated in priory.Simulation results verify the effectiveness of the proposed schemes.
文摘BACKGROUND Neuroendoscopy is a very useful technique to Chronic Subdural Hematoma(CSH).But how to achieve the goal of treatment more minimally invasive?AIM To develop a simple,fast and accurate preoperative planning method in our way for endoscopic surgery of patients with CSH.METHODS From June 2018 to May 2020,forty-two patients with CSH,admitted to our hospital,were performed endoscopic minimally invasive surgery;computed tomography(CT)imaging was employed to locate the intracerebral hematoma and select the appropriate endoscopic approach before the endoscopic surgery.The clinical data and treatment efficacy were analyzed.RESULTS According to the learning of CT scanning images,the surgeon can accurately design the best minimally invasive neuroendoscopic surgical approach and realize the precise positioning and design of the drilling site of the skull and the size of the bone window,so as to provide the most effective operation space with the smallest bone window.In this group,the average operation time was only about 1 h,and the clearance rate of hematoma was about 95%.CONCLUSION Patients with CSH can achieve good therapeutic effect by using our way to positioning and design to assist the operation of CSH according to CT scan and image,and our way is very useful and necessary.
文摘为解决恶劣工况下全断面硬岩隧道掘进机(tunnel boring machine,TBM)关键主承力结构应变监测难、监测不准的难题,提出了一种基于BP神经网络和有限元分析的TBM刀盘关键位置应变重构方法.首先,通过静、动力学有限元分析确定了TBM刀盘关键位置,并提取了刀盘典型易损特征子结构.其次,基于有限元技术和实验设计(design of experiments,DOE)方法,分别进行了标准件和特征子结构多载荷下静力学有限元分析,并构建了载荷-应变数据库.最后,运用BP神经网络建立了标准样件和刀盘特征子结构的应变重构模型,并进行了标准样件的实验验证.结果表明,重构应变的平均误差为10%,验证了方法的可行性,为TBM刀盘复杂结构的应变重构提供了一种可行的方法.
