摘要：为了理解具有单向离合器的带传动装置的性能动力学,把一标准的三个带轮的蛇形带传动和带弯曲刚度延伸到包含一单向离合器,该离合器的模拟是以从动带轮和其附件的相对速度为基础。该离合器锁上(接合)带轮和其附件零相对速度产生正的内离合器转矩,离合器脱开离合器转矩为零,允许两部件速度不均匀,该模型导出一分段线性系统。转换矩阵用来计算两线性结构在不连续时间序列内的系统响应,节约了大量的计算时间。对不同的激振频率带轮和附件的惯量比以及外部负载检查系统的动力学,其中包括响应和张力降低。因为离合器的单向传动,振动变化的研究在实际中提供了设计准则。

摘要：Catalytic hydrogenation is a vital industrial means to produce value-added fuels and fine chemicals,however, requiring highly efficient catalysts, especially the nonprecious ones. To date, the majority of high-performance industrial hydrogenation catalysts are made of precious metals-based materials, and any given catalyst could only be used to catalyze one or few specific reactions. Herein, we exemplify a crystal phase engineering approach to empower Ni nanoparticles(NPs) with superb intrinsic catalytic activities toward a wide spectrum of hydrogenation reactions. A facile pyrolysis approach is used to directly convert a Ni-imidazole MOF precursor into hexagonal close-packed(hcp)-phased Ni NPs on carbon support. The as-synthesized hcp-phased Ni NPs exhibit unprecedented hydrogenation catalytic activities in pure water towards nitro-, aldehyde-, ketone-, alkene-and N heterocyclic-compounds, outperforming the face-centered cubic(fcc)-Ni counterpart and the reported transition metalsbased catalysts. The density functional theory calculations unveil that the presence of hcp-Ni boosts the intrinsic catalytic hydrogenation activity by coherently enhancing the substrate adsorption strength and lowering the reaction barrier energy of the rate-determining step. We anticipate that the crystal phase engineering design approach unveiled in this work would be adoptable to other types of reactions.

摘要：在工程界现在普遍的趋势是要求重新研究各不同的标准以确是其在工业内最好的实践。本文介绍采用在ISO和AGMA标准对齿根强度估算方法的比较分析,并用开发的有限元和模型仿真进行证实。本分析(1)介绍了采用齿条和齿轮刀具制造的广大范围的直齿和斜齿轮,而(2)是齿轮主要几何学(齿轮设计),制造(齿条和齿轮刀具)和性能参数的不同组合,以及对每个齿轮进行齿根强度分析的有限元方法(FEM)。FEM的结果与用ISO和AGMA标准计算的相比较。对不同的设计、制造和性能参数组合的比较分析用图解说明和简要讨论。该结果将许可在现代工程实际中应用标准所存在的限制有一个很好的了解,并为改进和统一标准提供一个基础。

摘要：Molecular dynamics(MD) simulations were carried out to study the fracture behaviors of several symmetric tilt grain boundaries in γ-Ti Al bicrystals with misorientation axes. Tensile deformation along direction perpendicular to grain boundary was simulated under various strain rates and temperatures. The results indicate that the relative orientation of the grains and the presence of certain atom units are two critical factors of the interface structure affecting the stress required for dislocation nucleation. Dislocations nucleate and extend at or near the symmetric tilt grain boundaries during the tensile deformation of Σ3(111) 109.5°, Σ9(221) 141.1° and Σ27(552) 148.4° interfaces. For Σ27(115) 31.6° and Σ11(113) 50.5° interfaces, the interfaces fractured directly in a cleavage manner due to no dislocation emitted from the boundary. The tensile fracture mechanisms of the bicrystals are that micro-cracks nucleate at the grain boundary and propagate along the interface. The variance of crack propagation is whether there is accommodation of plastic region at the crack tips.

摘要：本文阐述侧面转矩定向差速器用速度图解的分类和分析,它常用于分析汽车变速器的换档侧面转矩定向差速器是由车辆右轮至左轮的转矩定向机构和同样的左轮至右轮的转矩定向机构组成。分析可见,当仅研究单向转矩定向机构部件时,那么该单向转矩定向机构至少由四个转动部件组成一个最简单的机构。该机构分为7种机构,即6个离合型机构和一个制动型机构。这些机构,对于转矩定向由离合器产生的离合滑动速度和能量损失表示离合转矩。作为结果,假定忽略其齿轮传动效率,搅拌损失等,则该7种机构能量损失的理论值在理想状态完全相同,最后,从实际机构的设计观点出发评估最好的机构。

摘要：Objective： To evaluate the effects of repairing rabbit radial defects with polyester/tricalcium phosphate scaffolds prepared by rapid prototyping technology loaded with bovine bone morphogenetic protein （ bBMP）, and find new carriers for growth factors. Methods： Polyester/tricalcium phosphate scaffolds prepared by rapid prototyping technology loaded with and without bovine BMP were used to repair the 15 mm radial defect in rabbit. Then the results of radiography, histology, scaffolds degrade rates and bone mineral density （BMD） were appraised to examine the effects at the 12th week. Results ： At the 12th week postoperatively, all defects treated with bBMP were radiographically repaired. No radius implanted polyester/tricalcium phosphate scaffolds without bBMP showed radiographic and histological union. At experimental groups, longitudinal alignment of lamellar structure was observed histologically at the 12th week,indicating that remodeling of regenerated bone was complete in different degree. Of the three experimental groups, the bony regeneration and remodeling of callus in poly lactide-co-glycolide/tricalcium phosphate （PLGA/ TCP） group was the best. The BMD values were beyond 70% of normal value at the 12th week while the PLGA/ TCP scaffolds group was the highest, and no abnormalities were observed in the surrounding soft tissue in all groups. Conclusions - Polyester/tricalcium phosphate scaffolds prepared by rapid prototyping technology loaded with bovine BMP can repair a 15 mm radial defect of rabbit. As for the results, the PLGA/TCP scaffold is ideal and better than poly L-lactide-co-D, L-lactide （ PDLLA/TCP ） scaffold, but the ploy L-lactic acid （PLLA/TCP） is not so good for its low degradation rates.

摘要：汽车轮胎胎面由许多花纹块和沟槽构成复杂图案,以提供轮胎的各项行驶性能,如牵引性能、制动性能、乘坐舒适性及排水性。轮胎与地面直接接触的面积有明信片大小,造成胎面磨耗的原因是轮胎与地面不可避免的滑动摩擦。轮胎磨耗不仅降低了行驶性能以及缩短轮胎寿命,

摘要：超临界二氧化碳(sCO_(2))Brayton循环作为下一代能量转换技术近年来得到了广泛的关注。为了综合优化设计Brayton循环轴系的支承和冷却系统参数,基于Riccati传递矩阵,综合考虑了转子的不平衡响应,临界转速和不平衡响应在工作转速点处的导数,建立了高速轴系多目标优化模型。针对轴系的sCO_(2)气体冷却装置的刚度非线性,利用混沌映射引入了混沌区间概念,提出了一种混沌区间多目标粒子群优化算法(CIMPSO),用于解决多目标下二维非线性变量的优化问题。应用CIMPSO算法对微型超临界二氧化碳透平机转子的轴承间距,轴承座的刚度、阻尼和参振质量,和sCO_(2)气体冷却装置的刚度进行了多次综合优化计算,结果表明:优化后的模型共振幅值得到有效抑制,且临界转速点远离工作转速,体现了优化算法的鲁棒性。最后基于任意一组优化解和经验解,建立轴系的有限元模型进行仿真计算,结果表明优化解对于转子系统的设计、控制转子的振动具有一定的指导意义。

摘要：预制节段拼装桥墩存在施工周期短,对交通和环境影响小等优势。随着经济的快速发展和城市化进程的加快,车辆撞击桥墩的事件增加,在极端情况下可能还会导致桥梁整体倒塌。然而,关于这种结构形式的抗车辆撞击性能研究仍较为匮乏,因此,非常有必要开展这方面的研究。该文基于显式动力分析软件ANSYS/LS-DYNA对车辆撞击预制混凝土节段拼装桥墩开展数值模拟工作,在保证数值模型合理性与准确性的基础上,探究几何与构造等因素对节段拼装桥墩抗车辆撞击性能的影响,具体包括截面类型、预应力筋以及剪力键布置等。结果表明:圆形截面相比于方形截面具有更好的抗车辆撞击性能;周边布置预应力筋相较于中心布置能够给节段拼装桥墩提供更好的抗车辆撞击性能;圆柱形混凝土剪力键能够通过提高节段拼装桥墩的整体性来提升节段拼装桥墩的抗车辆撞击性能。基于研究结果的综合考虑,对于实际工程应用问题,应将预制拼装桥墩按圆形截面设计,并采用周边布置预应力筋及节段中心布置剪力键的形式。

摘要：当今轮胎行业在设计新轮胎时普遍采用虚拟试验,因其能在节省大量开发时间的同时降低成本。虚拟试验除了模拟轮胎静态响应,还可以同时研究轮胎在道路上行驶的动态状况。这项工作可以进行不同条件下的轮胎试验,获取模型参数所需要的摩擦特征。其缺点就是无法控制的环境条件和轮胎结构会影响到试验结果。因此，在更多可控制条件下进行的小型试验更具有优势。胶料摩擦性能的试验特征因综合测量系统的必然性而有局限性。LATl00型实验室磨耗和滑动性能试验机（如图1所示，下称试验机）是针对轮胎行业的胶料测试而设计开发的，其利用特制摩擦盘模拟路况，测量直径为80mm小型滚动轮胎的湿滑、牵引力和磨耗，从而将结构复杂的轮胎简化为由一种胶料制造的实心轮胎，以研究滚动轮胎与道路之间的相互作用。