Modeling of Cross-Spring Pivots Subjected to Generalized Planar Loads

Cross-spring pivots, formed by crossing two identical flexural beams at their midpoint, have been broadly used in precision engineering and aerospace fields. Many researches have been conducted on modeling and analysis of cross-spring pivots. However the influence of application position and magnitude of the external loads on the load-rotation and parasitic motion characteristics has not yet been discussed. In order to reveal the effect of the external loads, this paper develops the accurate load-rotation and center shift models of cross-spring pivots, with generalized planar loads applied including bending moment, horizontal and vertical forces. Firstly, by using the energy method, the load-displacement models of the pivot are derived with the assumption of small rotational angles. Based on the models, the influence of generalized planar loads on the load-rotation relationship is discussed, which shows that both application position and magnitude of the vertical and horizontal forces influence the load-rotation behaviors. Then the accurate center shift expressions of the pivot with generalized planar loads are developed, which shows that the rotational angle is the dominant term for both components of the center shift while the vertical and horizontal forces are small. Finally, the accuracy of the proposed model is validated by finite element analysis（FEA）. Comparing the model data with the results obtained from FEA, the relative error of the load-rotation is less than 6% even if the rotational angle reaches 20°; the relative errors of the two components of center shift are less than 5% and 10% respectively when the rotational angle reaches 10°. The proposed model and analytical conclusions can be used to analyze and preliminarily design the compliant mechanisms containing cross-spring pivots.

Power Pivot技术在工程建设信息化中的应用

为了工程项目和合同明细的管理,跟踪合同的执行情况,及时分析合同工期和费用的偏差,采用Power Pivot技术应用于工程建设信息化。通过建立数据表、关联关系,运用Power Pivot内置的度量值,分别建立查询相关度量值;最后通过Power Pivot内置的度量值,分别建立统计分析相关度量值。该方法实现了单人工程信息的合同管理,为工程建设信息化提供了可靠的技术支持。

理路与支点:论新闻表征理论的符号学建构

新闻表征理论是关于新闻文本如何表现新闻真实问题的理论,它涉及新闻发布者、新闻接收者、新闻解释等多项元素。符号学与新闻表征理论关系密切,是后者构建的学理基础。依靠符号真实、流动呈现、框架博弈等支点,新闻表征理论可对新闻内容生产、传递、解释和接受等进行比较有效的符号学说明。作为新闻学理论的一种,对它的研究不仅对推进新闻学理论的探索具有现实意义,而且对于构建新闻学的自主知识体系具有理论意义。

尹锡悦政府的“全球枢纽国家”战略构想与实践评析

“全球枢纽国家”是尹锡悦政府的外交总目标,也是其外交话语的总括。尹锡悦政府的外交战略可以概括为“全球枢纽国家”战略。《尹锡悦政府120大国政课题》凸显了该战略的内涵。考察尹锡悦政府外交话语和外交实践,可分析“全球枢纽国家”战略的实施特点并对该战略进行评估。“全球枢纽国家”战略的实施推进集中表现出韩国价值观外交和经济外交两大特点。该战略表面上取得了包括美日韩戴维营峰会的举办、韩国总统受邀参加北约峰会等成果,但实际上在地缘政治、地缘安全、经济和文化等领域存在透支韩国战略力量的问题。“全球枢纽国家”战略导致东北亚乃至亚太地区的对立,进而恶化地区安全局势,并加剧了世界局势的动荡。

《伤寒论》桂枝汤方证再识

桂枝汤是《伤寒论》太阳病篇的重要方剂之一,而历代对于桂枝汤证的解读可谓众说纷纭,诸家讨论的重点主要集中于以下3个方面:(1)桂枝汤脉证中的“脉浮缓”指病机还是脉象?方证中的“阳浮而阴弱”中的“阴阳”所代为何?(2)桂枝汤究竟是发汗剂还是止汗剂?其又是通过何种机理发挥“解肌”作用?(3)在临床实践中,如何抓住桂枝汤的方证本质以扩充桂枝汤及其合方与加减方的临床应用范围?本文通过梳理分析《伤寒论》与《黄帝内经》的相关理论,并结合临证实践对以上3个问题进行深入剖析,进而得出结论,桂枝汤作为治疗机体“太阳为开”功能失常的代表性方剂,是张仲景对《黄帝内经》中“渍形以为汗”这一治疗手段的具体实践。桂枝汤所治乃荣弱卫强之证,桂枝汤通过其酸甘化阴充养营气及辛甘化阳鼓振卫阳的作用,达到浸渍肌腠而取汗的目的,因此桂枝汤外可祛肌腠之风邪,内能滋阴和阳,燮理气血,调和脾胃而治疗内伤杂病。

基于Pivots选择的有效图像块描述子

设计图像块特征表示是计算机视觉领域内的基本研究内容,优秀的图像块特征表示能够有效地提高图像分类、对象识别等相关算法的性能.SIFT(scale-invariant feature transform)和HOG(histogram of oriented gradient)是人为设计图像块特征表示的优秀代表,然而,人为设计图像块特征间的差异往往不能足够理想地反映图像块间的相似性.核描述子(kernel descriptor,简称KD)方法提供了一种新的方式生成图像块特征,在图像块间匹配核函数基础上,应用核主成分分析(kernel principal component analysis,简称KPCA)方法进行特征表示,且在图像分类应用上获得不错的性能.但是,该方法需要利用所有联合基向量去生成核描述子特征,导致算法时间复杂度较高.为了解决这个问题,提出了一种算法生成图像块特征表示,称为有效图像块描述子(efficient patch-level descriptor,简称EPLd).算法建立在不完整Cholesky分解基础上,自动选择少量的标志性图像块以提高算法效率,且利用MMD(maximum mean discrepancy)距离计算图像间的相似性.实验结果表明,该算法在图像/场景分类应用中获得了优秀的性能.

面向Web服务组合的pivot事务嵌套模型

Web服务组合中的事务具有执行周期长的特性,一个全局事务会被划分为多个分布的子事务。各个子事务对全局事务而言具有不同的重要程度,关键子事务执行的成功与否,直接影响到全局事务执行的成败。另一方面,对某些出现故障的事务需要进行补偿,而执行过多的补偿事务会带来巨大的补偿开销。针对这些问题,提出了一个基于pivot事务的嵌套事务模型,模型中的事务分为pivot事务和非pivot事务,且含有至少一个pivot事务。同时基于该模型,给出了一个pivot事务优先调度(pivot transaction priority scheduling,PTPS)算法,通过优先执行pivot事务,来减少在pivot事务失败时执行的补偿事务数目,降低补偿开销。

龙砂开阖六气针法结合24 h眼压曲线探析青风内障证治

龙砂开阖六气针法是在顾植山教授三阴三阳开阖枢理论指导下,结合六经辨证、六脉辨证、脏腑辨证、经络辨证、象态辨证、运气辨证等多种辨证方式进行针刺的一种方法。开阖枢理论是对人体三阴三阳之气升降出入状态的概括,从开阖枢角度,青风内障的病机可概括为开机不利、阖机不利、枢机不利。开机不利,当辨太阳或太阴开机不利;阖机不利,当辨厥阴阖之太过、厥阴阖之不足或阳明阖之太过、阳明阖之不足;枢机不利,当辨少阴枢机不利或少阳枢机不利。此外,导师解晓斌主任医师将24 h眼压曲线与“六经病欲解时”相结合,以眼压峰值的时间节点对应“六经病欲解时”的病变之经来辨时定经。临证以开阖枢理论结合24 h眼压曲线为指导,采用龙砂开阖六气针法,通过辨时定经、辨证定经来明确青风内障所主之经,指导青风内障的临床诊治。

一种改进Ball Pivoting的散乱点云数据重建算法

Ball Pivoting算法主要是用来对点云数据进行表面重建,算法是从一个种子三角形开始的,球沿着这个种子三角形的一个边进行旋转,直到这个球接触到下一个点,该边与该点组成一个三角形。该算法主要的缺点是当点云数据不均匀的时候球在滚动的过程当中不会接触到点,因此会产生洞。提出了一种对散乱点云数据进行重建的改进的Ball Pivoting算法;对初始点云数据构建k-d树,使得搜索区域算法时间效率提高;使用可变半径搜索改进算法,使得算法能够处理不均匀的点云数据而不会产生洞;优化了网格的拓扑结构。实验结果证明该算法相对于Ball Pivoting算法效率高,且不会生成洞,三角网格的拓扑结构好。

基于“开阖枢”理论探讨厥阴下利病机证治

开阖枢理论是中医基础理论的重要组成部分之一,是对六经气化升降出入与三阴三阳胜复进退的高度概括,在指导六经病辨治中具有重要意义。文章基于“开阖枢”中“厥阴为阖”理论内涵的解读分析,依据气血阴阳在厥阴阶段中“阖”的特性,归纳厥阴下利之病机,从气厥下利、血虚厥利、阴极寒厥下利、阳郁热厥下利与寒热错杂厥利等角度阐发厥阴下利病机证治,以期为临床提供理论参考。

PIVOT TABLE在监测数据统计中的应用

汇总环境数据,进行数据分析,编制环境监测报表是环境监测部门的例行工作之一。PIVOT TABLE可以快速编制各类统计报表。以云南省环境空气质量报表为例,叙述了PIVOT TABLE的使用方法和优点。

枢椎支点螺钉在寰枢椎钉棒固定中复位能力的生物力学测试

背景:目前,寰枢椎脱位的手术治疗主要采取后路寰枢椎钉棒内固定系统进行提拉复位,术中常通过增大连接棒的弯曲度进而增加寰椎和枢椎间的落差来提升复位效果,但增加了手术难度及风险。枢椎支点螺钉直接增加了寰椎和枢椎间的复位落差,但其增加复位能力的程度尚不清楚。目的:测试枢椎支点螺钉的复位能力,并与普通螺钉进行对比。方法:选取6具新鲜人体颅颈标本,切除双侧侧块关节囊、寰齿关节囊及横韧带制成寰枢椎失稳模型,每具标本枢椎双侧均依次进行3种内固定:植入单轴枢椎支点螺钉(A组)、多轴枢椎支点螺钉(B组)及普通螺钉(C组),将柔性超薄式薄膜压力传感器置于寰齿前间隙,置入2根相同曲度连接棒,模拟提拉复位,获取寰齿前间隙压力,3组间进行对比分析。结果与结论:①A-C组标本寰齿前间隙压力分别为(97.59±8.58),(60.43±5.09),(22.74±0.81)N,3组间寰齿前间隙压力比较差异有显著性意义(F=251.603,P=0.000),3组间两两比较差异有显著性意义(P=0.000);②结果显示相较于普通颈椎后路螺钉,枢椎支点螺钉应用于后路寰枢椎钉棒内固定系统可提升复位能力,且单轴枢椎支点螺钉相较于多轴枢椎支点螺钉提升后路寰枢椎钉棒内固定系统的复位能力更佳。

基于Pivot Table处理配送业务中的客户优先权分析教学方法研究

在对物流企业的调研过程中,发现数据透视表(Pivot Table)在企业中运用相当广泛,因此,在教学设计中有必要引入关于数据透视表分析物流数据的教学内容,运用这种计算机技术可以让学生快速地分析计算合并数据形成新的数据表,提高了工作效率,文中的目的在于探讨物流专业课程教学中关于客户优先权分析部分所运用的计算机数据分析和处理技术。

基于Pivot模型的无比钢结构体系地震反应简化分析

无比钢结构体系是一种新型的钢结构体系,该结构体系主要由小型桁架等基本单元组成,构造复杂。其墙体由于构件繁多,在有限元分析时十分不便。在借鉴等代拉杆简化模型的基础上,用SAP2000中的Pivot连接单元代替拉杆,进行墙体的简化分析,用一个无比钢结构实例进行对比,表明该简化方法在无比刚结构体系的弹性和弹塑性地震反应分析中的可行性。

谭华儒基于枢轴运动理论治疗小儿厌食经验

厌食为儿童常见疾病,谭华儒经长期临床观察及实践认为,枢轴运动失常、升降失常、四维旋转不利会引发小儿厌食,临床以顾护中气、斡旋中土、升降复序、四维运转、调和肝脾、木火升发、心肾相济、脾升胃降为主要治法,标本兼治,能有效改善儿童食欲和消化吸收能力,常用方为加味四君子汤。本文总结谭华儒基于枢轴运动理论治疗小儿厌食经验,附验案1则。

MEDTRONIC Open Pivot主动脉瓣机械瓣置换术后早中期临床结果

目的:回顾性分析MEDTRONIC Open Pivot主动脉瓣机械瓣置换术后早中期临床结果。方法:连续收集2016年1月至2019年12月在中国医学科学院阜外医院使用MEDTRONIC Open Pivot主动脉瓣机械瓣行瓣膜置换术的患者348例,回顾性分析患者的基线临床资料、手术结果、早中期生存率和并发症发生情况。结果:348例患者中,男性283例(81.3%),平均年龄(49.4±11.2)岁。围术期无患者死亡和二次手术。共333例(95.7%)患者完成随访,平均随访(1.9±0.8)年(最长3.36年,共计627人年)。随访期间,11例(3.3%)患者死亡,术后第1、2、3、4年分别死亡3例、2例、5例、1例;5例死于心力衰竭,1例死因为人工瓣膜功能障碍,1例因脑出血死亡,4例为其他非心脑血管原因死亡。术后1年、2年、3年累积生存率分别为99.0%、98.1%、93.5%。随访期间,14例(4.2%)患者出现人工瓣膜功能障碍,发生率为2.23%/人年;6例(1.8%)患者出现瓣周漏,发生率为0.96%/人年;2例(0.6%)患者因严重瓣周漏需二次接受手术。17例(5.1%)患者发生主要不良事件,其中心肌梗死1例(0.3%),脑出血2例(0.6%),脑栓塞1例(0.3%),其他严重出血事件13例(3.9%)。结论:MEDTRONIC Open Pivot主动脉瓣机械瓣有效、耐用,置换术后死亡率及并发症发生率低,是主动脉瓣膜置换的可靠选择之一。

大跨度连续梁0#段支架设计及反支点预压技术的创新与应用

本文探讨了新建铁路玛莫科2号特大桥主跨连续梁0#段支架设计及反支点预压技术的创新与应用。针对传统0#块支架设计复杂、成本高、不可重复利用的问题,本文提出了一种新型装配式托架方案,该方案通过模块化设计、灵活兼容的构造,实现了支架的快速安装与拆卸,显著降低了施工成本,提高了经济效益。同时,本文还介绍了反支点预压法的应用,过预埋的钢绞线和安装的千斤顶对托架实施反支点预压张拉,模拟实际施工荷载,验证了托架的稳定性、刚度和强度,确保了施工安全。研究结果表明,该新型托架方案及反支点预压技术在大跨度连续梁施工中具有显著优势,为类似工程提供了有益的参考。

Novel Annulus-shaped Flexure Pivot in Rotation Application and Dimensionless Design

Large-deflection flexure pivot is widely used in high precision rotation application, but there are less flexure configurations and simple and convenient design methods, This paper presents a novel large-deflection curved-compliant annulus-shaped flexure pivot composed of six curved beam flexure elements. It can offer more than lO^angular stroke theoretically. Firstly, main-motion pseudo-rigid-body method is introduced to establish the flexure pivot model. Although pseudo-rigid-body method can be used to analyze the large-deformation flexure pivot performance, the method is definitely a laborious and difficult task for designing this novel flexure pivot. In order to simply the designing process, dimension-design graphs based on the parametric models and finite element analysis is presented. Using the dimension-design method as a tool, the designers can determine the optimal geometry rapidly, based on the stiffness and rotation demands of an annulus-shaped flexure pivot. Finally, dimension-design graph examples are given whose primary design aims to achieve a rotation stroke of annulus-shaped flexure pivot. The finite element analysis results show that the relative designing error between anticipative rotation stroke and graph design result is less than 4%. The dimensionless method used in designing annulus-shaped flexure pivot can reduce design process in both time and complexity. The novel annulus-shaped flexure pivot and dimension-design method are helpful supplement to configuration and design method of large-deflection flexure pivot.

Direct linear discriminant analysis based on column pivoting QR decomposition and economic SVD

A direct linear discriminant analysis algorithm based on economic singular value decomposition （DLDA/ESVD） is proposed to address the computationally complex problem of the conventional DLDA algorithm, which directly uses ESVD to reduce dimension and extract eigenvectors corresponding to nonzero eigenvalues. Then a DLDA algorithm based on column pivoting orthogonal triangular （QR） decomposition and ESVD （DLDA/QR-ESVD） is proposed to improve the performance of the DLDA/ESVD algorithm by processing a high-dimensional low rank matrix, which uses column pivoting QR decomposition to reduce dimension and ESVD to extract eigenvectors corresponding to nonzero eigenvalues. The experimental results on ORL, FERET and YALE face databases show that the proposed two algorithms can achieve almost the same performance and outperform the conventional DLDA algorithm in terms of computational complexity and training time. In addition, the experimental results on random data matrices show that the DLDA/QR-ESVD algorithm achieves better performance than the DLDA/ESVD algorithm by processing high-dimensional low rank matrices.

Effects of water application uniformity using a center pivot on winter wheat yield, water and nitrogen use efficiency in the North China Plain

In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS;the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05);however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.