基于有限元法的人体座椅系统随机响应分析

基于人体解剖测量学和人体运动学建立了包括人体骨骼、肌肉、皮肤、坐垫、靠背和头枕的驾驶姿势的人体座椅系统三维有限元模型.通过人体座椅系统在重力作用下的静态分析,提供动态分析的人体驾驶姿势初始边界条件.通过频率提取分析确保随机响应分析所需足够数量的模态.通过计算腰椎到坐垫表面在垂直方向的传递函数验证了模型.最后分析了在座椅底部垂直方向0~20 Hz的白噪声激励下人体腰椎间盘的加速度和应力响应,得出由于座椅的耦合作用使得腰椎间盘响应峰值频率低于其固有频率.该方法可以代替实验研究其他方案的人体座椅系统动态响应问题.     

A non-linear finite element model of human L4-L5 lumbar spinal segment with three-dimensional solid element ligaments

This paper establishes a non-linear finite element model (NFEM) of L4-L5 lumbar spinal segment with accurate three-dimensional solid ligaments and intervertebral disc. For the purpose, the intervertebral disc and surrounding ligaments are modeled with four-nodal three-dimensional tetrahedral elements with hyper-elastic material properties. Pure moment of 10 N·m without preload is applied to the upper vertebral body under the loading conditions of lateral bending, backward extension, torsion, and forward flexion, respectively. The simulate relationship curves between generalized forces and generalized displacement of the NFEM are compared with the in vitro experimental result curves to verify NFEM. The verified results show that: (1) The range of simulated motion is a good agreement with the in vitro experimental data; (2) The NFEM can more effectively reflect the actual mechanical properties than the FE model using cable and spring elements ligaments; (3) The NFEM can be used as the basis for further research on lumbar degenerative diseases.     

Computing Matveev’s Complexity via Crystallization Theory: The Orientable Case

By means of a slight modification of the notion of GM-complexity introduced in [Casali, M.R., Topol. Its Appl., 144: 201–209, 2004], the present paper performs a graph-theoretical approach to the computation of (Matveev’s) complexity for closed orientable 3-manifolds. In particular, the existing crystallization catalogue available in [Lins, S., Knots and Everything 5, World Scientific, Singapore, 1995] is used to obtain upper bounds for the complexity of closed orientable 3-manifolds triangulated by at most 28 tetrahedra. The experimental results actually coincide with the exact values of complexity, for all but three elements. Moreover, in the case of at most 26 tetrahedra, the exact value of the complexity is shown to be always directly computable via crystallization theory.     

腰上三角的临床应用解剖

目的：为肾脏疾病及腰疝的手术操作提供解剖学依据．方法：观察腰上三角的形态及构成，观察经过该三角前方的肋下神经、髂腹下神经和髂腹股沟神经的组合形式及走行．结果：腰上三角的形态可为四边形、三角形和不规则形；肋下神经、髂腹下神经和髂腹股沟神经在腰上三角前方有4种不同的组合形式．结论：熟悉腰上三角前方肋下神经、髂腹下神经和髂腹股沟神经的走行及与第12肋的位置关系，对于避免手术中损伤这3条神经具有重要的实际意义．     

人体完整腰椎骨三维运动的测量研究

为了进行人体完整腰椎骨运动的研究，设计并制造了平行光三维运动测量和分析系统．通过平行光测量系统，将每个椎体上三个标志点的运动投影到光屏上，以摄象机动态记录并输入计算机图象处理系统进行数据处理，同时运用刚体运动学原理进行计算，获得人体完整腰椎骨三维运动的运动特征．     

关于K~2×I的几类塌缩问题

本文考虑当K为粘合一些由字表示的圆盘到对应圆周上所得可缩多面体时,K×1的塌缩问题。我们证明了当圆盘只有一个时,K×1可塌缩;进一步地,我们得到当圆盘有n+1时,其中n个是边界上同胚粘合时,K×1可塌缩。     

The 6-property for simplicial complexes and a combinatorial Cartan-Hadamard theorem for manifolds

The 6-property for 2-dimensional simplicial complexes is the condition that every nontrivial circuit in the link of a vertex has length greater than or equal to six. If a compact -manifold has a 2-dimensional spine with the 6-property, then we show that the interior of is covered by euclidean -space. In dimension , we show further that such a 3-manifold is Haken.

     

Eclipse治疗计划系统NTO优化工具在脊柱转移瘤立体定向放疗靶区外剂量跌落研究

为研究Eclipse治疗计划系统中正常组织目标(Normal Tissue Objective,NTO)优化工具参数,对脊柱转移瘤立体定向放射治疗计划靶区覆盖剂量和靶区外剂量跌落梯度指数(Gradiet Index,GI)的影响,本研究对10例脊柱转移瘤立体定向放射治疗患者设计两种类型计划。第1种添加NTO优化工具但不添加环优化条件,共得到360个计划,为参考计划;第2种添加环优化条件但不添加NTO优化条件,总共10个计划,为标准计划。所有计划最后剂量归一为100%处方剂量覆盖90%靶区体积。比较两种类型计划的靶区剂量适形度指数(Conformity Index,CI)、靶区外剂量跌落梯度指数、靶区最大剂量(D_max)、实际治疗时间和计划临床合格率。结果表明,当NTO优化工具参数Fall-off为0.5或者1,Priority为500、700和999时,计划的GI值相似(P>0.05),但是小于其他Fall-off和Priority的GI值(P<0.05);Fall-off和Priority对CI值大小和实际治疗时间没有影响(P>0.05);随着Priority增加,计划靶区体积(Planning Target Volume,PTV) D_max增加(P<0.05)。参考计划的临床合格率最高为70%。与标准计划相比,最合适NTO优化工具参数计划(Priority、Fall-off分别为500和0.5)的GI值更低(3.449 vs 3.655,P=0.000,Z=-5.534),实际治疗时间没有差异(2.65 min vs 2.32 min,P=0.063,Z=0.832),PTV D_max偏大(132.1% vs 128.8%,P=0.002,Z=4.214),CI偏大(0.911 vs 0.879,P=0.151,Z=0.984)。综上所述,在计划可通过情况下,当NTO优化工具中参数Distance from Target Border设置为0.2 cm,Start Dose设置为91%处方剂量,End Dose设置为49.4%处方剂量,Fall-off和Priority分别设置为0.5和500时,脊柱转移瘤立体定向放疗计划能够实现较好的靶区剂量适形度、更低的剂量梯度指数以及合适的治疗时间。     

Postural Sway during Local Vibratory Stimulation for Proprioception in Elderly Individuals with Pre-Sarcopenia

Objective: Many studies have demonstrated that the loss of muscle mass (LMM) poses a risk of postural instability in the elderly; however, few studies have shown how LMM decreases proprioception. In this study, we investigated the changes in postural sway among older individuals with LMM induced by application of a local vibratory stimulus. Method: We enrolled 64 older adults (mean age). Postural sway was measured while applying vibration stimuli of 30, 60, and 240 Hz to both the gastrocnemius and lumbar multifidus muscles. We also measured the relative proprioceptive weighting ratio (RPW) of postural sway. The patients were divided into LMM and non-LMM (NLMM) groups. The study subjects were compared in terms of their age, height, weight, body mass index (BMI), lower leg skeletal muscle mass index (LSMI), L4/5 lumbar multifidus cross-sectional area ratio, and RPW at 30, 60, and 240 Hz. Results: Subjects in the LMM group showed a significantly lower RPW at 60 Hz, LSMI, and BMI than did those in the NLMM group. Conclusions: Decrease in RPW with 60-Hz stimulation concerning the lower leg proprioception is a risk factor for LMM-associated postural instability in the elderly. Consequently, with respect to the gastrocnemius muscles proprioception in LMM, it is necessary to perform assessments using muscle spindle stimuli.     

右手持拍男性乒乓球运动员脊柱形态特征的研究

旨在研究比较右手持拍男性乒乓球运动员与普通男性大学生的脊柱形态差异. 利用DIERS光学三维脊柱分析仪各测量了40名男性大学生的脊柱参数. 研究发现右手持拍男性乒乓球运动员的骨盆倾斜距离、脊柱冠状面偏移距离、躯干倾角、脊柱偏移距离、脊柱矢状面偏移距离以及脊柱矢状面偏移角度与普通男性大学生相关指标表现出显著性差异(P<0.05); 右手持拍男性乒乓球运动员胸曲后凸角和腰曲前凸角均值低于普通男性大学生, 但无显著性差异(P>0.05). 结果表明, 乒乓球运动员的脊柱形态产生一定程度的变化可能与其长时间进行单侧的大强度训练有关.