The Effect of Inlet Angle Structure of Concave and Convex Plate on Internal Flow Characteristics of Alkaline Electrolyzer

The structure of the concave-convex plates has proven to be crucial in optimizing the internal flow characteristics of the electrolyzer for hydrogen production.This paper investigates the impact of the gradual expansion angle of the inlet channel on the internal flow field of alkaline electrolyzers.The flow distribution characteristics of concave-convex plates with different inlet angle structures in the electrolytic cell is discussed.Besides,the system with internal heat source is studied.The results indicate that a moderate gradual expansion angle is beneficial for enhancing fluid uniformity.However,an excessively large gradual expansion angle may lead to adverse reflux phenomena,reducing the overall performance of the electrolytic cell.

Analysis of Influence on Aerodynamic Noise of Wind Turbine Blades under Different Pitch Angles

Aiming at the influence of blade pitch Angle on aerodynamic noise of wind turbines, the sound field and flow field distribution at 0˚, 5˚, 10˚ and 15˚ are calculated by numerical simulation. Then, through the distribution of pressure field and velocity field calculated by flow field, the influence of different pitch angles on wind turbine blade aerodynamic noise and the reasons for its influence are analyzed. The results show that when the pitch Angle increases within 0˚ - 10˚, the aerodynamic noise pressure level of the blade decreases. However, the sound pressure level of aerodynamic noise increases in the range of 10˚ - 15˚. The changes of static pressure gradient and pressure pulsation on the blade surface make the aerodynamic noise change, and the changes of the two are positively correlated. At the same time, the fluid velocity and fluid motion state on the blade surface are closely related to the aerodynamic noise of the blade. The greater the fluid velocity, the more complex the fluid motion state and the greater the turbulent kinetic energy of the wind turbine blade, and the aerodynamic noise of the wind turbine blade will also increase.

A Study of Motion Perception in Primary Open Angle Glaucoma

Purpose: To study the features of the motion perception (MP) and explore the worth of the clinical application of MP test in primary open angle glaucoma (POAG).Methods: MPs were recorded from 41 patients (67 eyes) with POAG ang 56 normal subjects (112 eyes) by the MP software in PC compatible computer. Meanwhile , the MP ways and MP sites were analyzed and MP abnormal rate was compared to the clinical parameters and the visual function indices related to glaucoma. . Results: The results showed that the total abnormal rate of MP was 89. 5% in POAG, and the abnormal rate was 81. 6% in early stage of POAG, and MP abnormal degree had positive correlation with C/D, ocular tension and corrected loss variance (CLV), and negative correlation with visual acuity and mean sensitivity (MS), and no correlation with age and short-term fluctuation (SF) in the patients with POAG.Concusion: These results suggest that the MP test provides a newly effctive examination method in diagnosing the early POAG. Eye Science 1996;

The Characteristics of Interaction between Color and Motion Perception in PrimaryOpen Angle Glaucoma

Purpose: To investigate the characteristics of interaction between color and motion perception in primary open angle glaucoma (POAG) and measure motion perception of B,G and R cones, thus find a more sensitive method to diagnose the visual nerve damage in POAG. Methods : Motion perceptions of B,G and R cones were isolated by blue , green and red vertical line stimulus displayed on the yellow , purple and blue background respectively, then measured the displacement threshold and flicking threshold of motion perception from each cones in POAG, and compared it with the age-match normals.Results:The displacement threshold and flicking threshold of motion perception from B,G and R cones were all damaged in POAG compared with the normals, and the motion perception of G and B cones was deficits more obviously than the R cones.Conclusion: These findings support the suggestion that color provides an input to human motion perception. Magnocellular and parvocellular pathway may be significandy damaged in POAG,

Three-dimensional cooperative guidance law for multiple missiles with impact angle constraint

This paper proposes a cooperative guidance law for attacking a ground target with the impact angle constraint based on the motion camouflage strategy in the line-of-sight(LOS)frame.A dynamic model with the impact angle constraint is established according to the relative motion between multiple missiles and the target.The process of cooperative guidance law design is divided into two stages.Firstly,based on the undirected graph theory,a new finite-time consensus protocol on the LOS direction is derived to guarantee relative distances reach consensus.And the value of acceleration command is positive,which is beneficial for engineering realization.Secondly,the acceleration command on the normal direction of the LOS is designed based on motion camouflage and finite-time convergence,which can ensure the missiles reach the target with the desired angle and satisfy the motion camouflage state.The finitetime stability analysis is proved by the Lyapunov theory.Numerical simulations for stationary and maneuver targets have demonstrated the effectiveness of the cooperative guidance law proposed.

Angle of Attack between Blood Flow and Mitral Valve Leaflets in Hypertrophic Obstructive Cardiomyopathy: An In Vivo Multipatient CT-based FSI Study

The mechanisms of systolic anterior motion(SAM)of the mitral valve in hypertrophic obstructive cardiomyopathy(HOCM)remain unclear.To investigate the angle of attack between blood flow and mitral valve leaflets at pre-SAM time point,patient-specific CT-based computational models were constructed for 5 patients receiving septal myectomy surgery to obtain pre-and post-operative 2D vector flow mapping.The comparisons between pre-and post-operative angles of attack based on 2D vector flow mapping of 5 patients were performed.It was found that there was no statistically significant difference between pre-and post-operative angles of attack(61.1±t wa o vs.56.2±56.o,p=0.306,n=5).Therefore,we propose that the angle of attack might not play an important role in the initiation of SAM.

Camber Angle Control Method Corresponding to the Electric Vehicle Age

In recent years, the conversion of vehicles to electric power has been accelerating, and if a full conversion to electric power is achieved, further advancements in vehicle kinematic control technology are expected. Therefore, it is thought that kinematic performance in the critical cornering range could be further improved by significantly controlling not only the steering angle but also the camber angle of the tires through the use of electromagnetic actuators. This research focused on a method of ground negative camber angle control that is proportional to the steering angle as a technique to improve maneuverability and stability to support the new era of electric vehicles, and the effectiveness thereof was clarified. As a result, it was found that in the critical cornering range as well, camber angle control can control both the yaw moment and lateral acceleration at the turning limit. It was also confirmed that both stability and the steering effect in the critical cornering range are improved by implementing ground negative camber angle control that is proportional to the steering angle using actuators. Dramatic improvements in cornering limit performance can be achieved by implementing ground negative camber angle control that is proportional to the steering angle.

Regional Finite-Fault Source Model for Development of Ground Motion Attenuation Relationship in Sichuan, China

The attenuation relationship of ground motion based on seismology has always been a front subject of engineering earthquake.Among them,the regional finite-fault source model is very important.In view of this point,the general characteristics of regional seism-tectonics,including the dip and depth of the fault plane,are emphasized.According to the statistics of regional seism-tectonics and focal mechanisms in Sichuan,China,and the sensitivity of estimated peak ground acceleration(PGA)attenuation is analyzed,and the dip angle is taken as an average of 70°.Based the statistics of the upper crustal structure and the focal depth of regional earthquakes,the bottom boundary of the sedimentary cover can be used as the upper limit for estimating the depth of upper-edge.The analysis shows that this value is sensitive to PGA.Based on the analysis of geometric relations,the corresponding calculation formula is used,and a set of concepts and steps for building the regional finite-fault source model is proposed.The estimation of source parameters takes into account the uncertainty,the geometric relationship among parameters and the total energy conservation.Meanwhile,a set of reasonable models is developed,which lay a foundation for the further study of regional ground motion attenuation based on seismology.

全膝关节置换中BrainlabKnee3导航辅助间隙平衡技术的应用优势

背景:近年来,计算机导航技术辅助关节置换逐渐受到医疗领域的关注。文献报道计算机导航在全膝关节置换中的应用临床效果不一。为了探索新一代Brainlab Knee 3导航系统的临床效果,进行了此项研究。目的:分析计算机导航系统(Brainlab Knee 3)结合间隙平衡技术在全膝关节置换中的应用效果。方法:2020年11月至2021年5月大连市第二人民医院关节外科收治71例行全膝关节置换患者,导航组35例,术中采用计算机导航结合间隙平衡技术行全膝关节置换;传统组36例,术中采用传统手术器械定位截骨。比较两组患者术中内、外侧关节间隙差;膝关节活动度、KSS评分;髋膝踝角;冠状面股骨组件角、冠状面胫骨组件角和矢状面胫骨组件角偏差值。结果与结论:①导航组伸直位内外侧间隙差0,1,2 mm的患者分别为19,14,2例;屈膝90°位内外侧间隙差0,1,2 mm的患者分别为18,15,2例。传统组伸直位内外侧间隙差0,1,2 mm的患者分别为10,20,6例;屈膝90°位内外侧间隙差0,1,2 mm的患者分别为10,15,8例。②导航组手术时间长于传统组(P<0.05),导航组有2例患者术后形成下肢肌间静脉血栓,传统组患者均无并发症。③置换后6,12个月两组患者膝关节活动度均明显增加,导航组膝关节活动度高于传统组(P<0.05)。④置换后12个月两组患者KSS评分均明显增加,导航组KSS评分高于传统组(P<0.05)。⑤置换后6个月髋膝踝角、冠状面股骨组件角、冠状面胫骨组件角、矢状面胫骨组件角偏差值均显著小于传统组(P<0.05)。⑥结果表明,采用计算机导航结合间隙平衡技术辅助全膝关节置换对关节活动度、下肢力线、胫骨假体组件位置的准确性方面具有优势,置换后关节功能恢复良好。

一种联合TDCM和PFA的空间目标大转角ISAR成像方法

空间目标态势感知是当前航天技术领域的研究热点,逆合成孔径雷达(Inverse Synthetic Aperture Radar, ISAR)是空间目标感知的一种有效手段。为了得到利于目标鉴别的高分辨二维ISAR图像,需要通过增大积累转角来提高方位向分辨率。但是,随着转角的增大,平动与转动之间的耦合增大,使得传统的先平动补偿、后利用转动成像的两步式成像方法不再适用。本文提出了一种结合时域信号共轭相乘(Time Domain Conjugate Multiplication, TDCM)处理与极坐标格式算法(Polar Format Algorithm, PFA)的成像算法,首先利用雷达回波的二维相干性,通过TDCM处理进行平动粗补偿,然后借助PFA的插值操作校正大转角引起的散射点越分辨单元走动(Motion Through Resolution Cell, MTRC)并估计目标相对转动参数。通过迭代处理,持续对平动和转动参数进行优化,提升运动补偿效果。仿真验证了所提成像算法的有效性,与传统算法相比,成像聚焦性更好。

星载迈克尔逊干涉仪扫描角镜装调工艺研究

针对星载迈克尔逊干涉仪悬臂式扫描角镜组件装调维度多、装调精度高、检测困难等技术难点,提出了一种“向量解析+精密微动调整”方法,通过建立装调及检测基准、将角镜组件简化为空间点向量、采用“先法向后平面”的调整顺序、利用专用精密微动装置等措施,实现了空间多自由度角镜组件的高精度调整,角镜顶点位置对称度装调后达到8μm,优于0.01 mm的设计指标要求,有效提高了装调精度,缩短了装调周期。

硬质颗粒参数对列车增黏撒砂喷射行为的影响

为研究颗粒参数对列车增黏撒砂喷射行为的影响,利用可视化检测技术开展不同颗粒粒径、形状和密度下喷射行为试验,分析各因素对喷射速度、扩散角度的影响权重,探究不同颗粒在撒砂装置内部运动特征及影响机理。研究结果表明:随着颗粒粒径、密度的增大,颗粒喷射速度和扩散角度均逐渐减小,不规则颗粒的扩散角度普遍大于近圆形颗粒的扩散角度;喷射速度显著影响因素权重(从大至小)为:粒径、密度;扩散角度显著影响因素权重(从大至小)为:形状、粒径;颗粒粒径和密度与所受气固耦合力成正比,与初始时刻颗粒加速度成反比,不规则颗粒的碰撞次数高于近圆形颗粒的碰撞次数;根据耦合力和动能的变化规律将颗粒运动特征分为加速和稳定两个阶段,初始时刻颗粒加速决定颗粒在稳定阶段所获动能大小。

铁路自复位桥墩地震动最不利输入方向研究

为探究地震动输入角度对铁路自复位桥墩地震反应的影响,以一座简支梁桥为工程背景,建立空间自复位桥墩地震反应分析模型,并对模型进行验证。选择22组强震记录作为地震动输入,以屈服面函数Ψ作为判别最不利输入角度的标准,从0°开始顺时针旋转,每次增加5°,进行铁路自复位桥墩地震反应分析。结果表明:145°输入时,Ψ值最大,145°为桥墩最不利输入角度;在最不利方向下桥墩的地震反应大于顺桥向和横桥向。自复位桥墩设计时若不考虑地震动最不利输入方向,则偏于不安全。

基于Motion/AMESim的某风洞迎角机构建模与仿真研究

通过研究仿真软件Motion和AMESim的接口技术,搭建机械、液压和控制系统有机集成的联合仿真平台。以某风洞迎角机构为例,进行机、电、液一体化建模与仿真研究。仿真结果表明:Motion/AMESim联合仿真平台能对机、电、液系统的设计和分析提供理论支持,有广阔的应用和发展前景。

基于Leap Motion和Unity3D的虚拟沙画手势识别及交互

虚拟仿真技术的快速发展及体感设备的不断更新为沙画动画这一全新的艺术创作形式带来新的灵感。针对沙画现场作画工序复杂的问题,结合Leap Motion设备和Unity3D开发环境完成手势识别并驱动虚拟手实现虚拟沙画效果。首先,依据Leap Motion捕捉到的手势坐标及方向信息提取手部关键点;然后提出角域划分的方法并引入新的特征向量,将其与提取信息串联作为手势分类依据;最后,根据自行定义的沙画手势语义驱动虚拟手完成虚拟沙画创作。实验证明,利用Leap Motion完成近距离手势识别效果较其他方法结果更加精准,实时性较高,手势跟踪稳定,虚拟沙画绘画过程沉浸感强。

基于SGGC-Net动作捕捉系统解析行走步态的信度与效度

目的以有标记点三维运动捕捉系统(Vicon)为参照标准,比较基于SGGC-Net的动作捕捉系统(SGGC-Net系统)和SIMI系统解析行走步态的信度和效度。方法招募30名健康大学生,分析其在跑步机行走时的步态特征。应用Vicon系统12台红外摄像头及4台摄像机同步采集运动学数据,获取右侧参与者肩、肘、髋、膝和踝关节三维空间角度。采用组内相关系数(intra-class correlation coefficient,ICC)及其95%置信区间和测量标准误差(standard errors of measurement,SEM)评估信度;采用多重相关系数(multiple correlation coefficients,CMC)和均方根误差(root mean square error,RMSE)评估效度。结果SGGC-Net系统解析上、下肢三维空间角度最大、最小值的ICC范围为0.798~0.990,SEM范围为0.04°~0.95°;SIMI系统的ICC范围为0.650~0.967,SEM范围为0.31°~1.24°。除髋关节最小角度和膝关节最大角度外,SGGC-Net系统解析所有角度的ICC均高于SIMI系统,且SEM均低于SIMI系统。与Vicon系统得出的上、下肢主要关节角度曲线相比,SGGC-Net系统得出的曲线CMC范围为0.945~0.996,RMSE为1.44°~4.65°;SIMI系统的CMC范围为0.815~0.986,RMSE为2.56°~9.99°。除踝关节外,SGGC-Net系统在所有角度上的CMC均大于SIMI系统,RMSE均小于SIMI系统。结论SGGC-Net系统在大多数指标中的信度和效度优于SIMI系统,其在解析行走步态时具有较好的可重复性和准确性,可适用于无标记点情境下的动作捕捉,如运动员动作技术分析与特殊人群的临床步态解析。

跨走滑断层大跨度桁架悬索桥地震响应分析

跨越断层的长大跨度桥梁难免会受到断层错动作用,为探究跨走滑断层地震动参数对大跨度悬索桥地震响应的影响,以某主跨为538 m的钢桁架悬索桥为例,利用ABAQUS建立考虑桩-土相互作用(“m”法)的全桥有限元模型。通过叠加人工低频地震成分和实际高频地震成分,合成了跨走滑断层地震动,采用非一致激励位移时程法,重点分析永久位移、脉冲周期和跨断层角度对大跨度悬索桥的动力响应影响。结果表明:随着永久位移增大,桥塔动力响应呈不同幅度的增长,特别是横桥向位移、剪力,以及顺桥向弯矩增幅比较明显,分别增大97%、88%和95%,且剪力的增大加剧了桥塔发生剪切破坏的风险;随着脉冲周期减小,桥塔沿顺桥向和横桥向的动力响应增幅差距较大,当脉冲周期小于4 s时,桥塔横桥向位移、剪力,以及顺桥向弯矩相较于另一方向增幅更为明显,其增幅分别为492.5%、170%和189.2%;跨断层角度对桥塔的动力响应影响较大,且沿顺桥向和横桥向的响应变化趋势相反,跨断层角度为90°时,桥塔横桥向位移、剪力取得最大值,而弯矩取得最小值,且桥塔动力响应均在合理范围内,为最佳跨越角度。

波浪作用下平台吊放遥控水下机器人系统共振响应研究

针对平台吊放遥控水下机器人(Remotely operated underwater vehicle, ROV)过程中产生的复杂的共振现象会激发ROV剧烈的摆动和纵荡响应,从而影响下放安全的问题,本文基于Orcaflex软件建立了平台-吊缆-ROV耦合运动系统的数值仿真模型,采用时域分析方法,研究波浪作用下平台吊放ROV过程的空中下放阶段和水中下放阶段的共振响应特性。结果表明:空中下放阶段,单摆共振周期公式可以估算吊缆-ROV系统摆动周期,系统共振周期随缆长增加而不断增大;由于吊缆-ROV系统会同平台发生纵摇的谐振,下放过程中出现共振摆动和纵荡响应尤为剧烈的阶段。水中下放阶段,本文对单摆公式进行了修正,系统摆动周期估算误差低于4%;海水阻尼使系统共振摆角随缆长增加而减小,共振摆动得到明显抑制;流荷载导致吊缆-ROV系统共振周期的增大,且流速越大,共振周期增加越明显。在常见海况下放ROV时,下放过程存在共振区,可通过选择合适的下放速度以减小下放过程中的共振效应。

A Reverse Path Planning Approach for Enhanced Performance of Multi-Degree-of-Freedom Industrial Manipulators

In the domain of autonomous industrial manipulators,precise positioning and appropriate posture selection in path planning are pivotal for tasks involving obstacle avoidance,such as handling,heat sealing,and stacking.While Multi-Degree-of-Freedom(MDOF)manipulators offer kinematic redundancy,aiding in the derivation of optimal inverse kinematic solutions to meet position and posture requisites,their path planning entails intricate multiobjective optimization,encompassing path,posture,and joint motion optimization.Achieving satisfactory results in practical scenarios remains challenging.In response,this study introduces a novel Reverse Path Planning(RPP)methodology tailored for industrial manipulators.The approach commences by conceptualizing the manipulator’s end-effector as an agent within a reinforcement learning(RL)framework,wherein the state space,action set,and reward function are precisely defined to expedite the search for an initial collision-free path.To enhance convergence speed,the Q-learning algorithm in RL is augmented with Dyna-Q.Additionally,we formulate the cylindrical bounding box of the manipulator based on its Denavit-Hartenberg(DH)parameters and propose a swift collision detection technique.Furthermore,the motion performance of the end-effector is refined through a bidirectional search,and joint weighting coefficients are introduced to mitigate motion in high-power joints.The efficacy of the proposed RPP methodology is rigorously examined through extensive simulations conducted on a six-degree-of-freedom(6-DOF)manipulator encountering two distinct obstacle configurations and target positions.Experimental results substantiate that the RPP method adeptly orchestrates the computation of the shortest collision-free path while adhering to specific posture constraints at the target point.Moreover,itminimizes both posture angle deviations and joint motion,showcasing its prowess in enhancing the operational performance of MDOF industrial manipulators.

用于超声散斑跟踪血流测速的多角度平面波局部运动补偿

血流速度剖面用于计算壁面剪切率等血流动力学指标,与动脉粥样硬化病程发展密切相关。超快超声散斑跟踪广泛用于血流速度剖面估计,然而多角度平面波复合成像存在血流散射体的运动伪影,不利于流速估计。提出了一种多角度平面波复合成像的局部运动补偿法,对射频信号时间序列的相邻帧进行局部运动补偿来消除不同径向位置的运动伪影,从而提高流速测量准确性。相比直接相干复合,B-MoCo法将仿真、仿体实验中流速测量结果的归一化均方根误差平均减小了10.37%、37.82%,说明了B-MoCo法的有效性。基于兔骼动脉的实测实验进一步证明了B-MoCo法的临床可行性。综上,B-MoCo法能够有效提高血流速度剖面的测量精度,有助于相关心血管疾病的早期诊断与病程监测。