广义神经传播方程非协调类Wilson元的超收敛分析及外推

在半离散格式下研究了广义神经传播方程的非协调类Wilson有限元方法．利用该单元相容误差比协调误差高一阶的特殊性质和双线性元的高精度分析技巧,得到了相应的超逼近性质和超收敛结果．进一步地,构造了一个新的外推格式,并借助于该单元相容误差比协调误差高两阶的特殊性质,由此导出了能量模意义下具有O（h3）阶的外推效果．     

一类神经传播方程的特征差分方法与分析

首先对给定的方程进行恒等变换,再把MMOCAA差分方法与UNO插值相结合,提出了方程的MMOCAA-UNO差分方法,避免了基于k次Lagrange插值的MMOCAA差分方法在方程的解的陡峭前沿附近产生振荡．通过引入插值算子等方法给出了格式的误差估计．数值实验说明理论分析的正确性和格式的有效性．     

一类神经传播方程的特征差分方法和最佳阶l^2误差估计

给出矩形域上一类神经传播方程的特征差分,利用沿特征线方向构造差分逼近格式的方法和技巧．对给定的模型进行离散数值逼近和数值分析．特别是在沿特征线方向构造离散差分格式的过程中,可能会出现离散点在定义域之外的问题．本文提供了一个新的有效的差分逼近的处理方法,得到了该方法的三。一模误差估计．     

一类神经传导方程的变网格有限元方法及数值分析

研究在神经传播过程中的一类非线性拟双曲方程的初边值问题,对二维情形应用常规变换,提出了两种变网格有限元格式,最后通过细致的分析和估计得到了最佳阶的H1和L2 模误差估计结果,并且第二种格式使时间精度提高一阶,最后对第一种格式作了数值实验,指明方法是高效可行的．     

我国非肠道传播非甲非乙型肝炎(丙型)病毒NS3蛋白的部份cDNA克隆及序列分析

用15ml非肠道传播非甲非乙型肝炎病人的混合血清提取病毒RNA,经逆转录和聚合酶链反应(PCR)扩增,获得583个核苷酸的非肠道传播非甲非乙型肝炎病毒(HCV)NS3蛋白的cDNA片段.该片段与美国报道的同片段HCV cDNA原型比较,核酸序列同源性为80.9％,氨基酸序列同源性为93.2％。与日本报道的同片段J1 HCV cDNA相比较,核酸序列和氨基酸序列的同源性分别为92.6％和95.2％。用α-~(32)P同位素标记该片段,与HCV病人血清出现杂交反应。     

B超引导下臂丛神经阻滞麻醉对老年桡骨远端粉碎性骨折患者的麻醉效果分析

摘要 目的：研究B超引导下臂丛神经阻滞麻醉对老年桡骨远端粉碎性骨折患者的麻醉效果。方法：选择2018年12月～2020年6月我院的80例老年桡骨远端粉碎性骨折患者,采用随机数字表法,将患者均分为两组。两组均实施臂丛神经阻滞麻醉,其中对照组使用传统的解剖定位法,观察组使用B超引导法。比较两组的麻醉效果、麻醉用药剂量、阻滞起效时间、麻醉完成时间、镇痛维持时间;不同时间的平均动脉压、心率;且记录两组的脊髓麻痹、气胸、呼吸困难、局麻药物中毒发生率。结果：观察组老年桡骨远端粉碎性骨折病人的麻醉效果优良率（95.00 %）明显高于对照组（77.50 %,P<0.05);观察组的麻醉用药剂量、阻滞起效时间、麻醉完成时间均显著低于对照组,镇痛维持时间长于对照组(P<0.05);两组T2和T3时间点的平均动脉压和心率明显高于T1(P<0.05),且观察组的平均动脉压和心率明显更低(P<0.05);观察组的脊髓麻痹、气胸、呼吸困难、局麻药物中毒发生率明显更低(P<0.05)。结论：B超引导臂丛神经阻滞麻醉能提高老年桡骨远端粉碎性骨折患者的麻醉效果。     

南亚热带河流底栖硅藻β多样性及其对空间距离与环境梯度的响应——基于广义非相似性模拟的分析

β多样性指不同生境间群落物种组成的差异,其空间格局及影响因素是生物多样性维持研究的重要内容。以典型的南亚热带中小型河流—广州流溪河为对象,在对底栖硅藻进行季节调查的基础上,采用Baselga对β多样性的分解框架,基于S?rensen相异性系数将底栖硅藻的β多样性分解为周转和嵌套两个组分,运用广义非相似性模拟(Generalized Dissimilarity Modelling, GDM)分析了空间与环境因子对β多样性及其组分的影响。结果表明：底栖硅藻β多样性、物种周转和嵌套组分无明显季节差异,物种周转是流溪河底栖硅藻β多样性的主要组分(>75%);环境与空间过程共同影响流溪河底栖硅藻β多样性和物种周转组分格局,但环境选择是主要的驱动因子;与枯水期相比,丰水期的空间因素对β多样性和物种周转组分的影响程度降低。作为一种非线性距离回归方法,GDM能较好地识别底栖硅藻β多样性及其组分对环境梯度和空间距离的响应。     

Adaptive Finite Element Analysis of the Anisotropic Biphasic Theory of Tissue-Equivalent Mechanics

The nonlinear partial differential equations of the anisotropic biphasic theory of tissue-equivalent mechanics are solved with axial symmetry by an adaptive finite element system. The adaptive procedure operates within a method-of-lines framework using finite elements in space and backward difference software in time. Spatial meshes are automatically refined, coarsened, and relocated in response to error indications and material deformation. Problems with arbitrarily complex two-dimensional regions may be addressed. With meshes graded in high-error regions, the adaptive solutions have fewer degrees of freedom than solutions with comparable accuracy obtained on fixed quasi-uniform meshes. The adaptive software is used to address problems involving an isometric cell traction assay, where a cylindrical tissue equivalent is adhered at its end to fixed circular platens; a prototypical bioartificial artery; and a novel configuration that is intended as an initial step in a study to determine bioartificial arteries having optimal collagen and cell concentrations.     

Adaptive Finite Element Analysis of the Anisotropic Biphasic Theory of Tissue-Equivalent Mechanics

Abstract

The nonlinear partial differential equations of the anisotropic biphasic theory of tissue-equivalent mechanics are solved with axial symmetry by an adaptive finite element system. The adaptive procedure operates within a method-of-lines framework using finite elements in space and backward difference software in time. Spatial meshes are automatically refined, coarsened, and relocated in response to error indications and material deformation. Problems with arbitrarily complex two-dimensional regions may be addressed. With meshes graded in high-error regions, the adaptive solutions have fewer degrees of freedom than solutions with comparable accuracy obtained on fixed quasi-uniform meshes. The adaptive software is used to address problems involving an isometric cell traction assay, where a cylindrical tissue equivalent is adhered at its end to fixed circular platens; a prototypical bioartificial artery; and a novel configuration that is intended as an initial step in a study to determine bioartificial arteries having optimal collagen and cell concentrations.     

有限元法计算各向异性介质球头模型电位分布

在脑电正问题研究中,脑神经元所产生的电活动可用电流偶极子来模拟.本文提出把大脑看作各向异性介质球,即同时考虑电容效应、电导效应对脑内电流偶极子产生的电位的影响,并用有限元法推导出偶极子在各向异性介质球模型中的电位分布计算公式.结果表明介质的电容效应对电位分布是有影响的,反映了大脑活组织电特性,对外来不同频率的信号刺激有不同的响应.同时有限元法对大脑内某一区域内电位分布求解表明,测量较深层组织的电特性变化敏感的特点,可获得更多的测量信息.     

Thermo-Mechanical Analysis of Restored Molar Tooth using Finite Element Analysis

The aim of the study is to find most optimum combination of crown material and adhesive to avoid loosening and thereby failure of restored tooth. This study describes the Thermo-Mechanical analysis of restored molar tooth crown for determination of the stress levels due to thermal and mechanical loads on restored molar tooth. The potential use of the 3-D model was demonstrated and analyzed using different materials for crown. Thermal strain, stress and deformation were measured at hot and cold conditions in ANSYS and correlated with analytical calculation and existing experimental data for model validation and optimization. It is concluded that amongst various material porcelain crown with composite resin adhesive cement closely simulates the behavior of natural crown and should ideally result into long lasting restoration.     

Finite Element Analysis of Simulations of Cancellous Bone Resorption

A stochastic simulation of the resorption of cancellous bone has been developed and integrated with a finite element model to predict the resultant change in structural properties of bone as bone density decreases. The resorption represents the net imbalance of osteoclast and osteoblast activity that occurs in osteoporosis. A simple lattice structure of trabecular bone is considered, with an examination of the lattice geometry and discretization indicating that just five trabeculae need to be modelled. The results from the analysis show how the mechanical properties of the cancellous bone degrade with osteoporosis and demonstrate how the method can be used to predict the relationships between stiffness and density or porosity.     

A Three-Dimensional Finite Element Model for Biomechanical Analysis of the Hip

The objective of this study was to construct a three-dimensional (3D) finite element model of the hip. The images of the hip were obtained from Chinese visible human dataset. The hip model includes acetabular bone, cartilage, labrum, and bone. The cartilage of femoral head was constructed using the AutoCAD and Solidworks software. The hip model was imported into ABAQUS analysis system. The contact surface of the hip joint was meshed. To verify the model, the single leg peak force was loaded, and contact area of the cartilage and labrum of the hip and pressure distribution in these structures were observed. The constructed 3D hip model reflected the real hip anatomy. Further, this model reflected biomechanical behavior similar to previous studies. In conclusion, this 3D finite element hip model avoids the disadvantages of other construction methods, such as imprecision of cartilage construction and the absence of labrum. Further, it provides basic data critical for accurately modeling normal and abnormal loads, and the effects of abnormal loads on the hip.