Kinematic and Dynamic Characteristics Analysis of Bennett's Linkage

Bennett's linkage is a spatial fourlink linkage,and has an extensive application prospect in the deployable linkages.Its kinematic and dynamic characteristics analysis has a great significance in its synthesis and application. According to the geometrical conditions of Bennett 's linkage,the motion equations are established,and the expressions of angular displacement,angular velocity and angular acceleration of the followers and the displacement,velocity and acceleration of mass center of link are shown. Based on Lagrange's equation,the multi-rigid-body dynamic model of Bennett's linkage is established. In order to solve the reaction forces and moments of joint,screw theory and reciprocal screw method are combined to establish the computing method.The number of equations and unknown reaction forces and moments of joint are equal through adding link deformation equations. The influence of the included angle of adjacent axes on Bennett 's linkage 's kinematic characteristics,the dynamic characteristics and the reaction forces and moments of joint are analyzed.Results show that the included angle of adjacent axes has a great effect on velocity,acceleration,the reaction forces and moments of Bennett's linkage. The change of reaction forces and moments of joint are apparent near the singularity configuration.

General Order Principle for Multi-Bennett Linkages

Order analysis for multi-Bennett linkages is a difficult topic in kinematics. Traditional methods fail to obtain the order of multi-Bennett linkages due to considering the special geometric distributions among joint axes. An order principle for multi-Bennett linkages is presented. For a summated multi-Bennett linkage, three procedures are included in the order principle. Firstly, a homogeneous screw equation is obtained by taking linear superposition operations and then the maximum order is determined according to linear dependency of all screws. Secondly, two theorems are employed to determine the maximum order, where the first is used to judge the linear independency of four-system screws and the second is fit for identifying the linear independency of five-system screws. Lastly, all possible cases in the order range are considered until the valid order is screened out. For a syncopated multi-Bennett linkage, an equivalent summated model is built and then the order analysis is the same as that of summated linkages. In order to verify the effectiveness of the presented order principle, the orders of summated 5R and 6R linkages as well as a syncopated 6R linkage are analyzed. The computed orders of the former two summated linkages are both 4 and the computed order of the last syncopated 6R linkage is 5. The results coincide with the prototype data. The advantage of the proposed principle is that it can get the correct order of a multi-Bennett linkage without solving the geometric conditions of joint axes and has wide application in variety of multi-Bennett linkages.

基于Bennett机构的环形可展开桁架设计与分析

针对环形天线桁架在面对大口径卫星天线时存在柔性较大、容易引起卫星天线形变的问题,提出一种基于Bennett机构的环形可展桁架。首先,介绍空间过约束Bennett机构,通过改变Bennett机构的转动副与连杆关系,得到稳定的Bennett机构替代构型;其次,以替代构型为基本单元,构建基本单元之间的过渡机构,实现单元之间的衔接和力矩的传递,从而构建出环形可展桁架;最后,通过结构优化和仿真实验,验证了该桁架的可靠性,并与现有的三种环形桁架进行对比。结果表明,该桁架的比刚度与比模态频率均大于其它三种环形可展天线桁架,具备良好的稳定性。

Hospitalized prevalence and 5-year mortality for IBD:Record linkage study

AIM:To establish the hospitalized prevalence of severe Crohn's disease(CD) and ulcerative colitis(UC) in Wales from 1999 to 2007;and to investigate long-term mortality after hospitalization and associations with social deprivation and other socio-demographic factors.METHODS:Record linkage of administrative inpatient and mortality data for 1467 and 1482 people hospitalised as emergencies for ≥ 3d for CD and UC,respectively.The main outcome measures were hospitalized prevalence,mortality rates and standardized mortality ratios for up to 5 years follow-up after hospitalization.RESULTS:Hospitalized prevalence was 50.1 per 100 000 population for CD and 50.6 for UC.The hospitalized prevalence of CD was significantly higher(P < 0.05) in females(57.4) than in males(42.2),and was highest in people aged 16-29 years,but the prevalence of UC was similar in males(51.0) and females(50.1),and increased continuously with age.The hospital-ized prevalence of CD was slightly higher in the most deprived areas,but there was no association between social deprivation and hospitalized prevalence of UC.Mortality was 6.8% and 14.6% after 1 and 5 years follow-up for CD,and 9.2% and 20.8% after 1 and 5 years for UC.For both CD and UC,there was little discernible association between mortality and social deprivation,distance from hospital,urban/rural residence and geography.CONCLUSION:CD and UC have distinct demographic profiles.The higher prevalence of hospitalized CD in more deprived areas may reflect higher prevalence and higher hospital dependency.

Complete Real Solution of the Five-orientation Motion Generation Problem for a Spherical Four-bar Linkage

For a spherical four-bar linkage,the maximum number of the spherical RR dyad（R：revolute joint）of five-orientation motion generation can be at most 6.However,complete real solution of this problem has seldom been studied.In order to obtain six real RR dyads,based on Strum＇s theorem,the relationships between the design parameters are derived from a 6th-degree univariate polynomial equation that is deduced from the constraint equations of the spherical RR dyad by using Dixon resultant method.Moreover,the Grashof condition and the circuit defect condition are taken into account.Given the relationships between the design parameters and the aforementioned two conditions,two objective functions are constructed and optimized by the adaptive genetic algorithm（AGA）.Two examples with six real spherical RR dyads are obtained by optimization,and the results verify the feasibility of the proposed method.The paper provides a method to synthesize the complete real solution of the five-orientation motion generation,which is also applicable to the problem that deduces to a univariate polynomial equation and requires the generation of as many as real roots.

On China's Foreign Trade Development and Linkage with the Customary Rules of International Trade

Although great differences exist between the trade systems of different countries,internationaltrade must go on in line with the customary international trade rules.As China’s economy developsand the socialist market economic system emerges,China is basically qualified to link up withcustomary international trade rules.In the Ninth Five-Year Plan period,China’s reform of its foreigntrade system aims at setting up a trade system that conforms with international trade practice.Forthe purpose,the author of this article suggests that a neutral trade policy should be adopted inaccordance with the international practice since it does not hinder exports,nor restrict imports toan excessive degree.

切开复位内固定治疗Bennett’s骨折

目的观察切开复位内固定方法治疗Bennett’s骨折的临床疗效。方法自1994年1月以来采用切开复位内固定方法治疗Bennett’s骨折46例。男37例,女9例;年龄18-72岁,平均22．8 岁。新鲜骨折37例;陈旧性骨折9例。结果定期X片复查,骨折临床愈合时间平均2．5个月,术后4 -6个月取出内固定物。根据拇掌腕关节的局部症状、体征,拇对掌、外展、内收等活动、X线表现及TAM 系统评定:优:34例,为73．91％;良:10例,为21．74％;差:2例,为4．35％。优良率为95．65％。结论采用切开复位内固定方法治疗Bennett’s骨折,复位、固定可靠,治愈率高,并发症少,疗效满意。

Bennett's fracture associated with fracture of Trapezium——A rare injury of first carpo-metacarpal joint

Association of fracture of trapezium with Bennett'sfracture is very rare and makes reduction and stabilisation more difficult. We are reporting a rare case of Bennett's fracture with fracture of the trapezium and subluxation of the carpo-metacarpal joint(CMC) joint. The patient was a 47-year-old school teacher who fell from his motorbike on his outstretched right dominant hand. Radiographs and computed tomography showed fracture of the trapezium with subluxation of the CMC joint, associated with Bennett's fracture. Open reduction and internal fixation was carried out. Trapezium was reduced first and secured with a 2 mm diameter screw. Bennett's fracture was then reduced and fixed with two per-cutaneously placed Kirchner's wires. CMC was stabilised with percutaneous Kirchner's wires. Latest follow up at 12 mo showed a healed fracture with good reduction of the CMC joint. Clinically patient had no pain and normal extension, abduction and opposition of the thumb. QuickD ASH score was 3.9/100. Thus, fracture of trapezium associated with a Bennett's fracture is a rare injury and if ignored it may lead to poor results. This injury is more challenging to manage than an isolated Bennett's fracture as anatomical reduction of the trapezium with reduction of the first CMC is needed. Fracture of the trapezium should be fixed first as this will provide a stable base for reduction of the Bennett's fracture.

基于西门子Trace Service数控机床五轴联动精度评估模块二次开发

以西门子840D sl SINUMERIK Operate为系统应用框架,基于Trace Service数据采集功能,开发了一种以空走S试件轨迹为对象的数控机床五轴联动精度评估模块。针对Trace Service数据采集机制进行核心原理分析,通过S试件轨迹运行过程的数据需求,梳理数据采集流程并设计坐标轴数据采集子模块,再将数据采集结果进行分析提取进行坐标轴向刀尖点的转换,结合图形数字化手段完成轮廓误差图形与指标展示,综合实现数控机床五轴联动精度的评估。该模块利用S试件优秀的联动精度评估性能,集成高效数据采集与轮廓评估展示,避免了传统模式下采集和评估过程的繁琐性,有效提升了评估过程的经济性与效率。

逆顺法克氏针内固定治疗Bennett's骨折

第1掌骨基底骨折脱位,复位后不稳定,外固定难保持正确对位,切开复位顺行克氏针内固定也有误差,可造成稳位愈合,遗留疼痛和拇掌腕关节不同程度功能障碍。我们于1985～1991年用改进逆顺法两根克氏针内固定治疗Bennett’s骨折12例,效果满意,报告如下。1 临床资料本组12例,年龄19～38岁,多为年青战士。左侧3例,右侧9例。训练摔伤6例,重物砸压伤3例,暴力击伤3例。

Wilson病与微卫星DNA的连锁分析

目的探索国人Ｗｉｌｓｏｎ病（ＷＤ）基因位点（ＷＮＤ）与ＡＦＭ２３８ｖｃ３、Ｄ１３Ｓ３０１、Ｄ１３Ｓ３１６、Ｄ１３Ｓ２９６、及ＡＦＭ０８４ｘｃ５等５个微卫星ＤＮＡ（ＳＴＲ）之连锁关系，对ＷＮＤ进行精确定位。为ＷＤ基因克隆奠定基础。方法对２０个ＷＤ家系１１３名成员及１００名正常对照组成员的ＤＮＡ进行５个ＳＴＲ的聚合酶链反应（ＰＣＲ）扩增片段长度多态性分析；对ＷＮＤ及５个ＳＴＲ进行二点配对及多点连锁分析。结果ＷＮＤ与Ｄ１３Ｓ３０１、Ｄ１３Ｓ３１６、Ｄ１３Ｓ２９６呈紧密连锁，与ＡＦＭ２３８ｖｃ３及ＡＦＭ０８４ｘｃ５呈中度连锁。

Bennett单元阵列可展机构的动力学分析

为分析Bennett单元阵列可展机构的几何特性、运动学特性和动力学特性,建立通用的Bennett单元阵列可展机构的运动学和动力学分析模型.采用拆解法将Bennett单元阵列可展机构中的单元机构分成4个空间串联开链机构;根据开链机构的特性,引入坐标变换法结合螺旋理论建立Bennett单元阵列可展机构的运动学分析模型,用虚功原理法将各空间串联开链机构组装在一起,构建动力学分析模型和动力学分析方法;以4×4 Bennett单元阵列可展机构为例分析其运动学和动力学,并用仿真和实验来验证所建立的动力学分析模型和动力学分析方法.结果表明:算例中的Bennett单元阵列可展机构在其运动范围内运动平稳,对角线上的单元机构距离驱动单元愈远,其驱动角的角速度和角加速度变化范围越大.广义力矩的变化比较平缓,在其运动范围内不会引起较大冲击.仿真结果、实验结果与运动学和动力分析模型计算结果吻合较好,说明该运动学和动力学分析模型和方法是准确的,可以用来指导Bennett单元阵列可展机构的构型设计、轨迹规划和动力系统参数的选定等.

基于B/S模式的高职毕业生就业数据管理系统的设计与实现

为了实现对高职毕业生就业数据的信息化管理,为班主任方便、准确、快捷地录入就业数据提供服务,特别是为各职能部门及时、方便地了解学校就业情况,提出构建基于Web的高职毕业生就业数据管理系统。基于三层的B/S体系结构,采用ASP.NET(C#)+SQL Server 2000等网站开发技术,设计系统总体架构、功能模块和后台数据库,给出安全访问控制、DropDownList无刷新三级联动显示数据、导入导出数据、自动统计就业率等关键问题解决方案,实现集班主任就业数据录入和各类就业率查询统计为一体的网络应用平台。

GSTM1基因编码区SNP位点T1270533G与鼻咽癌的相关性

目的通过筛查GSTM1基因SNPs位点,研究该基因编码区单核苷酸多态位点T1270533G与鼻咽癌易感性和临床表型的关系。方法用PCR方法对中国人群27个个体DNA标本进行扩增、纯化及测序,从中获得GSTM1编码区、调控区和侧翼区及部分内含子区SNP位点,所获数据进行LD分析。选择编码区多态性位点T1270533G(该位点在中国人群罕见等位基因频率为22.2%),用tetra-Primer ARMS-PCR结合测序方法对鼻咽癌患者和对照人群进行相关性分析。结果通过测序共获取29个SNPs;其中13个SNPs位点之间均呈高度连锁不平衡;编码区多态性位点T1270533G的变异与鼻咽癌临床表型之间无明显关联(RR=0.170,95%CI=0.95-0.306 for homozygoteTT)。结论编码区多态位点T1270533G虽然发生了碱基顛换,产生了错义突变,导致了氨基酸的改变,但并没有影响其解毒功能。该位点在鼻咽癌患者和对照人群中等位基因型频率差别很小,与中国广东地区鼻咽癌易感性无明显关联。

共生理论视角下全日制教育硕士“U-S双实基地”双边联动培养模式建构

全日制教育硕士"U-S双实基地"双边联动培养模式是指大学(University)和中小学(School)通过合作,分别在其内部设置教育教学实验基地和教育教学实践基地,以此联动培养教育硕士的一种教育模式。在共生理论视角下,该模式实为大学与中小学以培养全日制教育硕士为中介而形成的一种共生结构,其共生单元为大学和中小学;共生模式为"U-S双实基地"双边联动;共生环境为当前的教育政策与信息技术条件。在该培养模式运行过程中,大学与中小学这两个共生单元的质参量相容构成该模式动力机制;"U-S双实基地"为该模式提供联动共生运作平台;约束条件下的连续共生性协议制度与信息技术条件为该模式提供共生环境保障。

多位点连锁分析检测Wilson病基因携带者及症状前患者

应用Ｓｏｕｔｈｅｍ余交技术，以ＷＮＤ位点两侧的四个ＤＮＡ多态标记一Ｄ１３Ｓ１（ｐ７Ｆ１２／ＴａｑＩ）、Ｄ１３Ｓ３１（ｐＣＲ１３２４／Ｔａｑ１和ｐＣＲＩ３２４／ＰｖｕⅡ）、Ｄ１３Ｓ２６（ｐＨ２１０／ＥｃｏＲＩ）对１０个Ｗｉｌｓｏｎ病家系的５４名个体进行多位点限制性片晰长度多态性（ＲＦＬＰ）连锁分析，检出２例症状前患者，１１例肯定携带者及５名正常纯合子，证实它们用于Ｗｉｌｓｏｎ病的症状前诊断及杂合子筛选是有效可靠的。

基于Twin-Bennett机构固面可展开天线的优化设计

为了解决Twin-Bennett(TB)机构控制固面可展开天线展开过程的干涉问题从而提高收拢能力,对传统太阳花式天线分割方案进行了改进。通过指数积公式建立了该固面可展开天线设计参数与收拢率之间的数学模型,并以收拢率为目标函数对盘面分割方案进行了优化分析,通过多初值点序列二次规划算法得到了最优设计参数。针对收拢的同步性问题进行了伞状同步展开机构的设计,该同步机构能将直线运动转化为固面可展开天线的展开运动,同时能保证整体固面可展开天线的单自由度和同步性。最后进行了软件仿真和实物模型的制作。整体设计可提高传统太阳花式固面可展开天线的收拢能力,将收拢率从44%降低至37%,同时保证了驱动机构的简易性。仿真分析和3D打印模型结果证明了该方法的可行性和合理性。

毛白杨S-腺苷高半胱氨酸水解酶基因PtSAHHA的克隆、表达及SNP关联分析

组合运用分子生物学及生物信息学方法,首次从毛白杨成熟木质部中分离出编码S-腺苷高半胱氨酸水解酶基因PtSAHHA的cDNA克隆。序列分析表明,毛白杨PtSAHHA cDNA片段全长为1 935 bp,其内部含有大小为1 458 bp的完整开放阅读框架,可编码含有485个氨基酸残基的蛋白质。组织特异性Realtime-PCR结果显示,PtSAHHA在木质部中表达丰度最高,在形成层和老叶中表达丰度中等,在嫩叶中表达丰度最低。在此基础上,组合利用MAGE5.0和DnaSP5软件对毛白杨自然群体中45株基因型个体的PtSAHHA序列进行对比和分析,共检测到166个单核苷酸多态性(SNP)位点,SNP频率为1/15 bp,多样性指数πT为0.010 58。在外显子区域共检测到88个SNP位点,其中同义突变位点34个,错义突变位点53个及1个无义突变位点;同义突变的核苷酸多样性πSynonymous=0.024 91,是非同义突变核苷酸多样性πNonsynonymous=0.002 33的10倍,推测毛白杨PtSAHHA基因编码区在毛白杨物种演化过程中受到较强的纯化选择压力。对PtSAHHA基因内的SNPs连锁不平衡分析结果表明,随着核苷酸序列长度增加至800 bp,即r2<0.1,SNPs的连锁不平衡水平已衰退至不明显。在此基础上,在由426株毛白杨基因型个体组成的关联作图群体内,对频率大于10%的42个常见SNP标记位点与6个木材品质性状进行关联分析,检测到3个SNP标记与3个表型性状显著关联。研究结果为基于分子标记的毛白杨优良木材品质性状定向辅助育种提供理论依据。

“U-G-S”教师教育模式下顶岗实习的协调联动机制探析--基于肇庆学院(D县)教师教育改革创新试验区的调查

加强师范类高校、地方政府与实习学校之间的协调联动机制,提升师范生的顶岗实习效果,是推动教师教育改革的有效措施。基于肇庆学院(D县)教师教育改革创新试验区的调查,该文研究分析了“U-G-S”教师教育模式背景下实施顶岗实习过程的协调联动机制,提出了进一步完善“U-G-S”模式下顶岗实习的对策建议。

基于Bennett机构的柱面拟合可展机构设计及分析

可展机构既可展开至指定构型用于工作,也可收拢以便于运输,在航天和建筑等领域具有广阔的应用前景。本文提出并设计了一种以Bennett过约束机构为基本组成单元的可展机构,该机构的工作形面可拟合柱面,且具有全部杆件可紧凑折叠成一束的收拢构型。对Bennett机构进行了几何描述,并分析其运动学特性;利用剪式机构实现了单元机构的组合连接,保证了设计关键点准确位于目标参数曲面上,计算了所设计的可展机构的展收比;对机构的运动学及动力学性能进行了仿真分析,验证了所提出的设计,为后续的样机研制提供了理论依据。验证结果表明:本文提出的Bennett过约束机构单元组合简单、形面拟合精度高、刚度大,能够很好地应用于该圆柱面天线的设计。该研究对航天可展机构的设计分析具有参考价值。