Objective To study three - dimensional finite element analysis for external midface distraction after different osteotomy in patients with cleft lip and palate ( Clp) . Methods Three - dimensional Fem models of Le Fo...Objective To study three - dimensional finite element analysis for external midface distraction after different osteotomy in patients with cleft lip and palate ( Clp) . Methods Three - dimensional Fem models of Le Fort Ⅰ,Ⅱand Ⅲ,osteotomy in Clp patients were estabolished. External midface distraction were simulated. An anteriorly and inferiorly directed 900 g force was展开更多
Focusing on the non-concave trajectory constraint,a sliding-mode-based nonsingular feedback fast fixed-time three-dimensional terminal guidance of rotor unmanned aerial vehicle landing,planetary landing and spacecraft...Focusing on the non-concave trajectory constraint,a sliding-mode-based nonsingular feedback fast fixed-time three-dimensional terminal guidance of rotor unmanned aerial vehicle landing,planetary landing and spacecraft rendezvous and docking terminal phase with external disturbance is investigated in this paper.Firstly,a fixed-time observer based on real-time differentiator is developed to compensate for the external disturbance,whose estimation error can converge to zero after a time independent of the initial state.Then,a sliding surface ensuring fixed-time convergence is presented.This sliding surface can guarantee that the vehicle achieves a non-concave trajectory,which is better for avoiding collision and maintaining the visibility of the landing site or docking port.Next,the nonsingular guidance ensuring the fixed-time convergence of the sliding surface is proposed,which is continuous and chatter free.At last,three numerical simulations of Mars landing are performed to validate the effectiveness and correctness of the designed scheme.展开更多
Background Nasal alarplasty is an important component of esthetic rhinoplasty in Asians.The two main surgical techniques that correct alar hypertrophy by reducing the height or length often leave external scars and ar...Background Nasal alarplasty is an important component of esthetic rhinoplasty in Asians.The two main surgical techniques that correct alar hypertrophy by reducing the height or length often leave external scars and are associated with a high relapse rate.Methods We developed a new technique,called three-dimensional(3D)M-shaped resection,which corrects both the nasal alar height and length and simultaneously minimizes external scarring.We performed this procedure from January 2013 to September 2016 in 49 consecutive female patients diagnosed with saddle nose and nasal alar hypertrophy.Their mean age was 28.6(range,18–40)years.All patients had previously undergone simple rhinoplasty.Nasal alar length and height,nostril length and width,and maximal nose width were analyzed preoperatively and postoperatively from photographs.Results After a mean of 9(range,3–24)months of follow-up,surgery was considered successful in 46 women(94%)with good cosmetic effects.In three patients,nasal alar hypertrophy recurred(6 months postoperatively).There were no early complications such as hematomas,infections,skin or mucosal necrosis,or wound dehiscence.The mean reductions postoperatively were 1.7 mm and 0.9 mm for nasal alar length and height,respectively,1.6 mm for both nostril length and width,and 3.5 mm for nose width.Conclusion The 3D M-shaped resection for nasal alar hypertrophy effectively reduced hypertrophy in 94%of patients for up to 24 months,producing minimal external scars and good cosmetic effects.It is a simple and convenient technique that is an effective and safe option for nasal alarplasty.展开更多
The conventional re-entry guidance method considerably limits the maneuverability of hypersonic glide vehicles under pre-given angle-of-attack profiles.To address this issue,based on a previous three-dimensional(3D)pr...The conventional re-entry guidance method considerably limits the maneuverability of hypersonic glide vehicles under pre-given angle-of-attack profiles.To address this issue,based on a previous three-dimensional(3D)profile guidance method,we propose a lateral-profile-first 3D profile optimization design strategy to solve the trajectory generation problem under complex conditions involving multiple constraints.Unlike the traditional method,which prioritizes the design of the longitudinal drag acceleration profiles,our method first converted the re-entry flight constraints into a lateral flight corridor,generated the initial lateral profile via parameterization,and solved the 3D profile using the coupling relationship between the longitudinal and lateral motions.The design of the 3D profile requires simultaneous consideration of waypoints,no-fly zones,and altitude profiles;hence,a new 3D profile optimization design model was constructed,and a customized sequential quadratic programming algorithm was employed to solve it.The advantages of the proposed method were demonstrated based on landing footprint results obtained using the lateral profile-first strategy.Finally,simulation results based on the common aero vehicle-high-performance model verified the feasibility and effectiveness of the strategy.展开更多
新能源电源提供的短路电流幅值受限,故障特征弱化,影响母线故障的快速准确识别。该文利用三相电流同一采样值突变量快速提取电流突变特征,将母线各支路电流进行分组,分别构造了两种启动元件,根据启动元件的动作时序,快速识别母线区内、...新能源电源提供的短路电流幅值受限,故障特征弱化,影响母线故障的快速准确识别。该文利用三相电流同一采样值突变量快速提取电流突变特征,将母线各支路电流进行分组,分别构造了两种启动元件,根据启动元件的动作时序,快速识别母线区内、外部故障和区外转区内故障。建立了母线多支路分组电流突变量采样值的分析平面,经过极性转换与采样值积分,直观反映母线区内外故障时电流突变采样值的运动轨迹,在此基础上,建立了识别母线区内外故障的保护动作区。利用实时数字仿真平台(real time digital system,RTDS)建立仿真系统,仿真结果表明,母线故障时,启动元件动作时间小于1ms,利用电流突变采样值轨迹可以快速识别区内外故障及转换性故障。展开更多
文摘Objective To study three - dimensional finite element analysis for external midface distraction after different osteotomy in patients with cleft lip and palate ( Clp) . Methods Three - dimensional Fem models of Le Fort Ⅰ,Ⅱand Ⅲ,osteotomy in Clp patients were estabolished. External midface distraction were simulated. An anteriorly and inferiorly directed 900 g force was
基金co-supported by the National Defense Basic Scientific Research Project,China(No.JCKY2020903B002)the National Natural Science Foundation of China(Nos.61973100,62273118 and 12150008)。
文摘Focusing on the non-concave trajectory constraint,a sliding-mode-based nonsingular feedback fast fixed-time three-dimensional terminal guidance of rotor unmanned aerial vehicle landing,planetary landing and spacecraft rendezvous and docking terminal phase with external disturbance is investigated in this paper.Firstly,a fixed-time observer based on real-time differentiator is developed to compensate for the external disturbance,whose estimation error can converge to zero after a time independent of the initial state.Then,a sliding surface ensuring fixed-time convergence is presented.This sliding surface can guarantee that the vehicle achieves a non-concave trajectory,which is better for avoiding collision and maintaining the visibility of the landing site or docking port.Next,the nonsingular guidance ensuring the fixed-time convergence of the sliding surface is proposed,which is continuous and chatter free.At last,three numerical simulations of Mars landing are performed to validate the effectiveness and correctness of the designed scheme.
文摘Background Nasal alarplasty is an important component of esthetic rhinoplasty in Asians.The two main surgical techniques that correct alar hypertrophy by reducing the height or length often leave external scars and are associated with a high relapse rate.Methods We developed a new technique,called three-dimensional(3D)M-shaped resection,which corrects both the nasal alar height and length and simultaneously minimizes external scarring.We performed this procedure from January 2013 to September 2016 in 49 consecutive female patients diagnosed with saddle nose and nasal alar hypertrophy.Their mean age was 28.6(range,18–40)years.All patients had previously undergone simple rhinoplasty.Nasal alar length and height,nostril length and width,and maximal nose width were analyzed preoperatively and postoperatively from photographs.Results After a mean of 9(range,3–24)months of follow-up,surgery was considered successful in 46 women(94%)with good cosmetic effects.In three patients,nasal alar hypertrophy recurred(6 months postoperatively).There were no early complications such as hematomas,infections,skin or mucosal necrosis,or wound dehiscence.The mean reductions postoperatively were 1.7 mm and 0.9 mm for nasal alar length and height,respectively,1.6 mm for both nostril length and width,and 3.5 mm for nose width.Conclusion The 3D M-shaped resection for nasal alar hypertrophy effectively reduced hypertrophy in 94%of patients for up to 24 months,producing minimal external scars and good cosmetic effects.It is a simple and convenient technique that is an effective and safe option for nasal alarplasty.
基金supported by the National Natural Science Foundation of China(Grant Nos.11902346,11502289,and 62173336)。
文摘The conventional re-entry guidance method considerably limits the maneuverability of hypersonic glide vehicles under pre-given angle-of-attack profiles.To address this issue,based on a previous three-dimensional(3D)profile guidance method,we propose a lateral-profile-first 3D profile optimization design strategy to solve the trajectory generation problem under complex conditions involving multiple constraints.Unlike the traditional method,which prioritizes the design of the longitudinal drag acceleration profiles,our method first converted the re-entry flight constraints into a lateral flight corridor,generated the initial lateral profile via parameterization,and solved the 3D profile using the coupling relationship between the longitudinal and lateral motions.The design of the 3D profile requires simultaneous consideration of waypoints,no-fly zones,and altitude profiles;hence,a new 3D profile optimization design model was constructed,and a customized sequential quadratic programming algorithm was employed to solve it.The advantages of the proposed method were demonstrated based on landing footprint results obtained using the lateral profile-first strategy.Finally,simulation results based on the common aero vehicle-high-performance model verified the feasibility and effectiveness of the strategy.
文摘新能源电源提供的短路电流幅值受限,故障特征弱化,影响母线故障的快速准确识别。该文利用三相电流同一采样值突变量快速提取电流突变特征,将母线各支路电流进行分组,分别构造了两种启动元件,根据启动元件的动作时序,快速识别母线区内、外部故障和区外转区内故障。建立了母线多支路分组电流突变量采样值的分析平面,经过极性转换与采样值积分,直观反映母线区内外故障时电流突变采样值的运动轨迹,在此基础上,建立了识别母线区内外故障的保护动作区。利用实时数字仿真平台(real time digital system,RTDS)建立仿真系统,仿真结果表明,母线故障时,启动元件动作时间小于1ms,利用电流突变采样值轨迹可以快速识别区内外故障及转换性故障。
