Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC相似文献   

基于最小编码长度的基因数据聚类(英文)

[目的]分析基于最小编码长度的基因数据聚类算法的聚类效果,以期为基因数据聚类提供新的方法。[方法]将基因数据的聚类看成是高维混合数据的聚类,通过对基因数据进行预处理后,再利用主成分分析将基因数据降维,降维后基因数据呈类高斯分布,这样分布的基因数据能够被一个简单的基于有损数据压缩的聚类算法进行有效的聚类,而该基于有损数据压缩的聚类算法是根据聚类后使基因的总体编码长度最小原则对基因进行聚类的。试验中分别利用该新算法与传统聚类算法对酵母和拟南芥基因数据进行聚类,并通过基因聚类内部评价和功能评价来验证该新算法的有效性。[结果]通过利用酵母和拟南芥基因数据对新算法的验证试验表明,该研究中的新算法得到的聚类效果优于传统聚类算法,且避免了聚类数需要主观确定和对初始聚类中心敏感等问题。[结论]该研究结果为基因数据聚类提供了一种全新的聚类方法。     

聚氨酯注模成型技术在家具生产中的应用

利用聚氨酯(PU)注模成型技术,可高效生产性能优良、造型美观、成本低廉的仿木材料,近几年被广泛应用于中国家具行业。本文从PU原材料选用及配比,模具设计及制作,注模工艺条件控制,以及PU生产工艺流程等方面,系统阐述PU注模成型的关键技术。     

人工林落羽杉力学性能研究

对江汉平原人工林落羽杉物理力学性能进行了研究,结果表明:落羽杉的气干密度为0.413 g/cm3,气干密度等级为轻;综合强度为74 MPa,强度等级为Ⅰ级;径向横纹抗压强度略大于弦向横纹抗压强度;端面硬度最高,弦面硬度与径面硬度差别不大。落羽杉南北面近树皮处木材的密度、抗弯强度、弹性模量、顺纹抗压强度均大于近髓心处,南北方向对落羽杉的密度、顺纹抗压强度在5%水平上差异均不显著,而对其抗弯强度、弹性模量在1%水平上差异显著。     

Microcracking and Chloride Penetration of Concrete under Uniaxial Compression

A non-destructive method of evaluation of specific crack area was used to characterise microcracking in concrete prisms during uniaxial compression loading and unloading. Chloride profiles were also measured after the same concretes were exposed to chloride environment. The relation among microcracking, stress-strength ratio and chloride penetration of concrete were analysed based on the experimental results. Under compressive load, the apparent chloride diffusion coefficient decreases until about one third of the ultimate load. Further increase of compressive load improves the chloride diffusion coefficient again. There is a close link between microcracking and stress-strength ratio. The index of specific crack area can be used to indicate the microcracking and study chloride transport behaviour into concrete under the influence of microcracking.     

Experiments on heat loss characteristics in a fully opened cylindrical cavity receiver

The climate has a great impact on highway bridge rubber bearings than on building rubber bearings. In order to study the change of the mechanical properties during the life of the plain chloroprene rubber bearings of highway bridge under freeze-thaw cycle condition, the plain chloroprene rubber bearings were processed 25, 50, 75, 100 times by freeze-thaw cycle in the standard freeze-thaw chamber, then the axial compression tests were carried. The changes of the performance indicators in the bearing capacity , the ultimate compressive strength, vertical stiffness, elastic modulus under different freeze-thaw cycles were analyzed comparatively. The results show that the plain chloroprene rubber bearings are more prone to brittle failure after the freeze-thaw cycle, and the failure phenomena of steel plate exposing or cracks is more serious than the phenomena of the standard specimen. With the increase of the number of freeze-thaw cycle, the ultimate bearing capacity, ultimate compressive strength and compressive elastic modulus of the plain chloroprene rubber bearings decrease. The attenuation formula and decay curve in 50 years of ultimate compressive strength and elastic modulus of compression are analyzed by least square method, the trends of change are both in line with the exponential function. The mechanical properties of plain chloroprene rubber bearings of highway bridge significantly decreased under freeze-thaw cycle condition. therefore, the temperature ranges of plain chloroprene rubber bearings of highway bridge should be strictly controlled, and some suggestions, such as increasing its minimum applicable temperature, usng the natural rubber bearings as much as possible in cold regions, have been given.     

GSR800型固化生物质燃料成型机设计制造技术

采用创新理念设计制造出GSR800型固化生物质燃料成型机。该机结构设计合理,能耗低,使用寿命长,更新维修简便,生产的固化生物质燃料质量优异。在借鉴传统环模结构的基础上,该机采用了行星轮系结构、迷宫结构等创新性设计,其与国内外同类机型相比具有许多优势。     

方捆打捆机连杆断裂问题改进探讨

指出了活塞部件是打捆机中的重要组成部分,其故障率一直处于一个相对较高的水平。结合市场上打捆机活塞的主要故障形式,从打捆机活塞故障的主要来源、活塞质量改进的角度进行了分析和研究。通过对活塞运动轨迹、阻力、焊合件材料的选用的分析,确定了活塞适用焊合材料、轴承要求、秸杆作业湿度等条件,提出了"选用新焊合材料、活塞轴承、增加活塞刮板,对打捆机连杆断裂故障率大幅度降低"的解决方案,并且通过试验验证了方案的可行性。     

饲用甜高粱秸秆应力松弛特性及参数优化的试验研究

为研究甜高粱秸秆压缩过程中的流变特性,利用多功能电子蠕变松弛试验机及自制压缩装置进行甜高粱压缩过程的应力松弛试验研究。选取压缩密度、切碎段长度、含水率为试验因素,选取应力迅速衰减时间和平衡弹性模量作为应力松弛特性评价指标,利用Box-Behnken试验方案进行三因素三水平响应面试验分析。结果表明:甜高粱秸秆压缩过程的应力松弛模型可用广义Maxwell模型中的五元件方程表示,其拟合系数0.99;各因素影响应力迅速衰减时间的主次顺序为:切碎段长度含水率压缩密度;对平衡弹性模量影响的主次顺序为:切碎段长度压缩密度含水率;甜高粱应力松弛最佳优化参数组合:当压缩密度为647.38kg/m3,切碎段长度为20～30mm,含水率为57%时,应力迅速衰减时间为4.693s,平衡弹性模量89.957kPa。试验确定了出捆后最佳捆绳及缠膜时间,为甜高粱压缩、打捆收获机的开发提供了技术依据。     

农田残膜压缩成型的参数优化

针对机械回收后农田残膜集条(堆)质地松散、储运本成本高,为残膜二次回收利用带来巨大困难的问题,采用多因素正交试验方法,以残膜成型块松弛比和比能耗为试验指标,压缩力、保压时间、含土率和含水率为影响因子,对影响残膜压缩成型各因素及其影响规律进行研究,建立并分析了各影响因素与残膜成型块松弛比和比能耗的回归模型。试验结果表明:影响残膜成型块松弛比的主次参数依次为:压缩力含土率保压时间含水率;影响残膜压缩过程比能耗的主次参数依次为:压缩力保压时间,含土率和含水率对残膜压缩比能耗影响不显著。残膜压缩成型作业最优参数取值为:压缩力13.3 MPa、保压时间25 s、含土率53.9%、含水率16.7%,可得到残膜成型块松弛比为1.321,比能耗为26.92 J/g。研究结果可对后续农田残膜压包成型机具的设计及作业参数优化提供理论依据。