不同品种黄芪中的氨基酸和微量元素含量的比较

目的：为合理开发利用黄芪的植物资源提供参考。方法：各品种黄芪经适当提取分离后，采用6300氨基酸自动分析仪测定游离氨基酸的含量和采用原子吸收光谱来测定微量元素。结果：游离氨基酸总含量云南栽培黄芪为1．7373％，梭果黄芪为0．5608％，金翼黄芪为0．3741％；不同品种黄芪中含Cu，Fe，Zn，Mg，CO，Al等元素。结论：游离氨基酸含量云南栽培黄芪为最高，金翼黄芪为最低；不同品种黄芪中微量元素含量有差异。     

Finite element analysis and fatigue of stents

Understanding the behaviour of implantable medical devices is of obvious importance. The potential for failure of a medical device can often be associated with issues related to cyclic loading of the device, and material fatigue. Detailed finite element simulations to evaluate the fatigue of stents allow the engineer to assess potential failures. The engineer can then use the analysis results to modify the design and prevent failure, without making and testing numerous physical devices. Complete understanding of the mechanical behaviour of a stent provided by finite element analysis has the benefits of facilitating effective design, helping to reduce time to market and minimising the potential for unwanted failures.     

Transformation of standardized clinical models based on OWL technologies: from CEM to OpenEHR archetypes

Introduction The semantic interoperability of electronic healthcare records (EHRs) systems is a major challenge in the medical informatics area. International initiatives pursue the use of semantically interoperable clinical models, and ontologies have frequently been used in semantic interoperability efforts. The objective of this paper is to propose a generic, ontology-based, flexible approach for supporting the automatic transformation of clinical models, which is illustrated for the transformation of Clinical Element Models (CEMs) into openEHR archetypes.Methods Our transformation method exploits the fact that the information models of the most relevant EHR specifications are available in the Web Ontology Language (OWL). The transformation approach is based on defining mappings between those ontological structures. We propose a way in which CEM entities can be transformed into openEHR by using transformation templates and OWL as common representation formalism. The transformation architecture exploits the reasoning and inferencing capabilities of OWL technologies.Results We have devised a generic, flexible approach for the transformation of clinical models, implemented for the unidirectional transformation from CEM to openEHR, a series of reusable transformation templates, a proof-of-concept implementation, and a set of openEHR archetypes that validate the methodological approach.Conclusions We have been able to transform CEM into archetypes in an automatic, flexible, reusable transformation approach that could be extended to other clinical model specifications. We exploit the potential of OWL technologies for supporting the transformation process. We believe that our approach could be useful for international efforts in the area of semantic interoperability of EHR systems.     

Simulation of Waveforms of a Ferrite Inductor with Saturation and Power Losses

We propose a model of an equivalent electrical circuit specifically designed for a ferrite indAuctor excited by a sinusoidal waveform. The purpose of this model is its use in a circuit simulator. We calculate the model parameters by means of Finite Elements in 2D which leads to significant computational advantages over the 3D model. We carry out the validation for a toroidal ferrite inductor by comparing the experimental results and computed ones. We consider the saturation and power losses in the core. In addition, we have tested the model for the case of square waveform in order to generalize the results. We find excellent agreement between the experimental data and the results obtained by numerical calculations.     

Fracture risk of lithium-disilicate ceramic inlays: A finite element analysis

Objectives

In the present study, lithium-disilicate ceramic inlays should be analyzed biomechanically according to their thickness and dimension, and it should be clarified as to whether there is a significant relationship between the inlay volume and the induced tensile stress level.

Methods

Using a new parametric CAD modeling procedure, 27 lithium-disilicate ceramic inlays with various parameters of “depth”, “width”, “angle” and restoration volume were generated. These inlays were integrated into the CAD model of a lower molar created from the CT data of an anatomical preparation. The resulting CAD models were, finally, three-dimensionally cross-linked to FEM models. After applying a compressive force of 200 N, Principal Tensile Stresses (PTSs) could be measured in the inlay. The values were subject to statistical analysis afterwards.

Results

The volume of the inlay restorations varied between 35.7 mm³ and 82.5 mm³. The maximum PTS values (n = 10) only showed a slight negative correlation with the inlay volume. The correlation coefficient according to Spearman was −0.082 (p ≤ 0.001). If the highest 1000 PTS values of each inlay were considered (n = 1000), the correlation coefficient was further reduced to +0.068 (p ≤ 0.001). No significant correlation between the inlay volume and the induced PTS level could be detected.

Significance

Under the conditions and limitations of the present FEM study, the inlay volume did not significantly influence the tensile stress level of ceramic inlays. The results may support the thesis that volume-reduced all-ceramic inlays might not have an increased fracture risk. Further studies are needed to confirm this.     

不同根管预备方法对根管壁应力分布的影响

目的:研究不同根管预备方法对根管应力大小和分布的影响,从生物力学角度探讨不同根管预备方法对根管抗性的影响。方法:选取30颗离体下颌单根管第一前磨牙,随机分成三组,每组10个牙:G1组(标准法)用旋转镍钛器械Mtwo预备;G2组(冠向下法)用旋转镍钛器械Protaper预备;G3组(逐步后退法)用不锈钢K锉预备。各组按相应方法预备后,进行根管充填,复合树脂修复。运用技术和abqus有限元分析软件结合,分别建立各组实验牙齿三维有限元模型,采用中央垂直加载,计算三种不同根管预备方法预备后根管壁的应力大小及分布状况。结果:各实验组预备后剩余根管壁牙本质上平均应力水平略有差异,G1组与G3组、G2组与G3组间差异具有统计学意义(P<0.05),G1组与G2组间差异无统计学意义(P>0.05)。结论:各实验组平均Von mises应力峰值均远小于牙本质的极限压缩强度,这三种常用的根管预备方法都是安全可行的。镍钛Protaper和Mtwo使根管应力分布更加均衡,明显减小了应力集中,推荐使用Protaper和Mtwo来进行根管预备来预防牙根纵裂的发生。     

Reports

Abstract

In the past, vertical intrusive movement of teeth has been considered difficult and most routine clinical vertical movement of teeth has been confined to extrusion. It has been suggested that attempts at intrusion may result in an increased incidence of root resorption and also in occasional devitalization.

The displacement and resulting stress fields associated with such treatment can be successfully studied using the finite element method. In the case being considered initial movements are known to be small; therefore, the assumption in the study that the material behaves linear-elastically is considered to be reasonable.

This study of vertical tooth movement demonstrated that the maximum cervical margin stress in the periodontal ligament was 0·0046 N/mm², whilst the highest apical stress was 0·00205 N/mm² when intrusive and extrusive forces of 1 Newton were applied to the buccal surface of the crown of a tooth model. These stresses were evaluated in the light of previous studies and found to be within the suggested clinical optimum level. However, the periodontal stress distribution following orthodontic loading within this three-dimensional finite element model was found to be highly complex.     

压水堆核电站燃料元件包壳破损监测通道报警阈值研究

目的 建立压水堆核电站不同运行工况下燃料元件包壳破损监测通道测量值的计算方法,计算在三种一回路冷却剂浓度条件下监测通道的剂量率,指导该监测通道报警阈值的设置。方法 分析了压水堆核电站各种工况情况下一回路冷却剂中的放射性核素,根据燃料元件包壳破损监测通道的实际设计情况,采用MCAM建模软件建立了可用于MCNP软件计算的模型,计算了三种不同工况情况下元件包壳破损监测通道的测量值。结果 三种工况条件下,该监测通道的计算值分别为8.0×10^-6、5.3×10^-4、1.6×10^-3Gy/h。结论 建议将5.3×10^-4、1.6×10^-3Gy/h分别设置为一级和二级报警阈值,该两级报警阈值的设置均与现役电站运行阈值相当。     

三种骨水泥弥散类型对胸腰段椎体强化术后术椎应力影响的三维有限元分析

目的 :利用三维有限元分析胸腰段椎体强化术后三种骨水泥弥散类型在不同载荷下术椎的应力分布变化。方法:通过1例L1椎体压缩性骨折患者和3例L1椎体强化术后骨水泥分别呈弥散型、团块型、混合型患者的原始CT资料,通过Mimics 19.0、Geomagic Studio 2013及Solid Works 2017等软件处理,建立T11～L2椎体功能单元压缩性骨折及三种骨水泥弥散类型的有限元模型,运用有限元分析方法,约束L2椎体下表面所有节点的各向活动,于T11椎体上表面施加均匀分布的400N面载荷,压力方向垂直向下,模拟正常人体上半身重量;同时在T11椎体上表面于不同方向施加10N·m力矩,模拟正常人体前屈、后伸、左侧屈、右侧屈、左旋转、右旋转6种运动状态。并在T11表面分别施加0.3MPa(低压力)、1MPa(中压力)、4MPa(高压力)分别模拟日常生活活动,比较4种模型在不同载荷情况下应力分布情况。结果:骨水泥注入后,在各级压力下,骨水泥呈团块型分布对术椎应力明显高于弥散型与混合型,4种模型术椎的应力与压力增加呈正相关,在6种载荷下,骨水泥呈团块型分布对术椎的应力均明显高于混合型与弥散型,混合型对术椎的应力较低,且在施加0.3、1、4MPa压力下,术椎在前屈载荷下所受应力最大,团块型应力最高,分别为63.295MPa、84.419MPa、174.96MPa;弥散型为62.348MPa、80.974MPa、160.95MPa、混合型为47.667MPa、62.171MPa、124.35MPa。结论:胸腰段椎体强化术后术椎应力与其所受压力及载荷方向相关,团块型骨水泥是导致术椎应力增高的重要因素,骨水泥呈混合型分布可能是理想的弥散类型。     

An accurate,convective energy equation based automated meshing technique for analysis of blood vessels and tissues

An automated three-element meshing method for generating finite element based models for the accurate thermal analysis of blood vessels imbedded in tissue has been developed and evaluated. The meshing method places eight noded hexahedral elements inside the vessels where advective flows exist, and four noded tetrahedral elements in the surrounding tissue. The higher order hexahedrals are used where advective flow fields occur, since high accuracy is required and effective upwinding algorithms exist. Tetrahedral elements are placed in the remaining tissue region, since they are computationally more efficient and existing automatic tetrahedral mesh generators can be used. Five noded pyramid elements connect the hexahedrals and tetrahedrals. A convective energy equation (CEE) based finite element algorithm solves for the temperature distributions in the flowing blood, while a finite element formulation of a generalized conduction equation is used in the surrounding tissue. Use of the CEE allows accurate solutions to be obtained without the necessity of assuming ad hoc values for heat transfer coefficients. Comparisons of the predictions of the three-element model to analytical solutions show that the three-element model accurately simulates temperature fields. Energy balance checks show that the three-element model has small, acceptable errors. In summary, this method provides an accurate, automatic finite element gridding procedure for thermal analysis of irregularly shaped tissue regions that contain important blood vessels. At present, the models so generated are relatively large (in order to obtain accurate results) and are, thus, best used for providing accurate reference values for checking other approximate formulations to complicated, conjugated blood heat transfer problems.