OH…O Out-of-Plane Bending Band [γ(OH)] and Its Overtone Band of Dimethylol Propionic Acid(DMPA)

In the present paper are reported the OH…O out-of-plane bending band[γ(OH)] between 900—950 cm -1 of dimethylol propionic acid(DMPA), its dependence upon temperature and its overtone band investigated via FTIR spectroscopy. It has been found based on the crystal structure that the band [γ(OH)] may not certainly be the characteristic band of carboxylic dimers, it can also result from another H-bond formed between carboxylic carbonyl and the primary hydroxyl. In addition, the band [γ(OH)] is very sensitive to temperature change but its overtone band can only appear at a low temperature.

Analysis of plane strain bending of a strain hardening curved beam based on unified yield criterion

The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. The solutions for the mechanical properties of plane strain bending are derived, which are adapted for various kinds of non-strength differential materials and can be degenerated to those based on the Tresca, von Mises, and twin-shear yield criteria. The dependences of the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane on different yield criteria and Poisson’s ratios are discussed. The results show that the influences of different yield criteria and Poisson’s ratio on the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane of the curved beam are significant. Once the value of bis obtained by experiments, the yield criterion and the corresponding solution for the materials of interest are then determined.

Multi-scaled simulation of latticed frames considering bending collapse of pipes

To consider the bending collapse of the pipes in the latticed frames, based on the multi-scale simulation, the collapsed parts of the pipe are meshed by the shell elements as micro-scaled models, and the other parts are meshed by beam elements macro-models. The incremental displacement constraint equations for the nodes on the section between the two models are established based on the plane section premise of classical beam theory. The method to introduce the constraint equations is derived based on the Updated Largrangian method. The location of the micro-model is predicted by the stress field of the beam element, and the length of the collapsed part is adjusted by the plastic energy in the micro model. Several examples are included to illustrate the efficiency and accuracy of this method.

Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

预应力UHPC-RC无腹筋组合梁足尺模型抗弯试验及极限弯矩计算研究

为了解预应力UHPC-RC无腹筋组合梁(简称组合梁)的抗弯性能,以2座组合梁桥实际工程为背景,分别制作25 m长工字形组合梁及30 m长箱形组合梁足尺模型进行抗弯试验,研究组合梁在弯曲荷载下的裂缝发展形态、荷载~挠度曲线及不同截面高度应变等。结果表明:2种组合梁最终受弯破坏时,1条主裂缝快速发展为贯穿弯曲裂缝,组合梁裂缝细密;荷载~挠度曲线较为饱满,刚度折减较普通预应力混凝土梁明显推迟,结构性能更为优良;开裂前组合梁截面受力发展满足平截面假定,出现主裂缝后逐渐不满足平截面假定。为考虑组合梁截面在极限状态不满足平截面假定的情形,基于UHPC材料本构关系,提出采用体外预应力筋极限理论推导组合梁极限弯矩计算方法,并将该方法与平截面假定理论计算结果及试验结果进行对比。结果表明:提出的组合梁极限弯矩计算方法较平截面假定理论计算方法能更好地反映结构受力。

Experimental and Numerical Study of Dilute Gas-Solid Flow inside a 90°Horizontal Square Pipe Bend

A pneumatic test rig is built to test a curved 90° square bend in an open-circuit horizontal-to-horizontal suction wind tunnel system. Sand particles are used to represent the solid phase with a wide range of particle diameters. Velocity profiles are constructed by measuring the gas velocity using a 3-hole probe. Flow patterns inside the bend duct are introduced using sparks caused by burning sticks of incense with the air flow inside the piping system for flow visualization purpose. Numerical calculations are performed by Lagrangian-particle tracking model for predicting particle trajectories of dispersed phase, and standard k-ε model for predicting the turbulent gas-solid flows in bends. Comparisons made between the theoretical results and experimental data for the velocity vectors and particle trajectories show good agreement.

On plane Λ-fractional linear elasticity theory

Non-local plane elasticity problems are discussed in the context of Λ-fractional linear elasticity theory. Adapting the Λ-fractional derivative along with the Λ-fractional space, where geometry and mechanics are valid in the conventional way, non-local plane elasticity problems are solved with the help of biharmonic functions. Then, the results are transferred into the initial plane.Applications are presented to homogeneous and the fractional beam bending problem.

斜倾厚层山体弯曲-侧滑机理分析——以重庆武隆庆口滑坡为例

重庆武隆庆口滑坡发育在斜倾厚层陡崖带上,下方数百年的煤矿开采形成了大面积的采空区。基于对地质条件、采空区现状和山体变形特征的分析,发现该滑坡既有弯曲张拉变形又有侧向滑移变形,提出了弯曲-侧滑破坏模式。根据山体变形历史,分弯曲变形和滑移变形两个阶段,分析了滑坡变形特征,研究了岩层面产状变化。并根据层面与临空面组合关系,将山体破坏分为弯曲张拉破坏、楔形体破坏和平面滑动破坏3个阶段,建立了各破坏阶段的判据,揭示了弯曲-侧滑型滑坡演变规律和形成机理,为该类滑坡防灾减灾提供了科学依据。

SNP-9对Aβ_(25-35)导致bEnd.3细胞损伤的作用及其机制

为了研究来源于丝素蛋白水解物的神经保护活性多肽SNP-9对于阿尔茨海默病(Alzheimer′s disease,AD)中血脑屏障损伤的作用,使用Aβ_(25-35)损伤脑微血管内皮细胞bEnd.3建立AD损伤模型,并给药干预。通过MTT实验检测SNP-9和Aβ_(25-35)对细胞活力的影响;RT-qPCR法检测SNP-9和Aβ_(25-35)对细胞紧密连接(tightjunctions,TJs)相关的ZO-1、occludin和claudin-5 mRNA水平的影响;Westernblot检测SNP-9和Aβ_(25-35)对细胞TNF-α、磷酸化NF-κB、NF-κB、IκBα和RAGE蛋白水平的影响。实验结果显示,SNP-9给药减少了Aβ_(25-35)诱导的bEnd.3细胞损伤,改善了模型细胞中ZO-1、occludin和claudin-5 mRNA水平的异常情况,缓解了Aβ_(25-35)导致的TNF-α、磷酸化NF-κB、IκBα和RAGE蛋白水平异常。研究结果表明,SNP-9可能通过影响RAGE/NF-κB通路,调控模型细胞炎症因子TNF-α水平,改善TJs相关指标异常,缓解Aβ_(25-35)诱导的bEnd.3细胞损伤。

Investigation on Porosity and In-plane Water Permeability of Nonwoven Geotextiles

Nonwoven geotextiles have been widely used as drains orfilters in many civil engineerings.The hydraulic charac-teristics of geotextiles are the basic function in these ap-plications.The in-plane permeability of nonwoven geo-textiles was discussed in this paper.The results of in-plane permeability coefficient of nonwoven geotextilesfrom measurement were analyzed.

基于平面弹性-板弯曲模拟关系的薄板有限元列式——从膜单元到薄板单元

本文全面讨论了基于平面弹性 -板弯曲模拟关系的薄板有限单元的理论和方法。由于直接对弯矩函数进行插值 ,c1连续性的要求得以自然避免。薄板单元可以直接在 c0 连续的层面上加以构造 ,无需借用 Reissner- Mindlin的中厚板理论 ,由之引发的闭锁问题也得以避免。本文系统地阐明了平面弹性膜单元与薄板弯曲单元的对应关系 ,及由平面弹性膜单元向薄板弯曲单元转换的一整套方法 ,为薄板单元的构造提供了一条新的有效的途径。文中给出了对应于平面弹性膜单元CST、LST、Q4、Q8的薄板单元 ,我们称之为 MPS板单元。MPS板元以挠度和转角为自由度 ,便于实际应用 ,和其它板单元相比具有非常高的精度。

压-弯-扭共同作用下闭口截面钢构件弯矩作用平面内极限承载力

利用Umansky闭口截面扭转理论,在现行GB 50017—2003"建筑钢结构规范"的基础上,得到适用于压-弯-扭共同作用下闭口截面构件弯矩作用平面内极限承载力的计算方法;采用数值分析方法对提出的设计公式进行验证,在建模时引入初始几何缺陷和残余应力,在分析时考虑几何非线性和物理非线性的影响;最后针对扭矩作用下矩形截面压弯构件截面塑性发展规律进行分析。研究结果表明:本文所提出计算公式能够真实反映构件的受力状态,使用便捷;在压力、弯矩和扭矩共同作用时可能存在的7种荷载路径对矩形截面钢管的极限承载力几乎没有影响;构件的抗弯和抗压极限承载力随着扭矩的增大而降低,且降低的程度越来越大;约束扭转的存在只会使截面最危险点更早地进入塑性状态,而对截面最终承载能力的影响不大,因此,根据自由扭转理论提出的设计公式对于存在约束扭转的矩形截面构件依然适用。

基于同步辐射白光形貌术和X射线迹线法的6H-SiC单晶结构缺陷研究

[目的]SiC材料结构缺陷的检测和控制是实现材料应用的关键环节,因此本文对6H-SiC单晶中的结构缺陷进行研究。[方法]采用同步辐射白光形貌术观察6H-SiC单晶中的基本螺位错和基平面弯曲,并利用X射线迹线法模拟基本螺位错的形貌和基平面弯曲后衍射斑点的形状。[结果]6H-SiC单晶中的典型结构缺陷之一为基本螺位错,它的形貌特征为白色的圆斑;由于热弹应力的存在,6H-SiC单晶在生长过程中容易发生基平面弯曲,结果导致衍射斑点的形状发生改变。[结论]同步辐射白光形貌术和X射线迹线法可以用于检测6H-SiC单晶结构缺陷;样品的基本螺位错密度为1.56×10~4/cm^2,基平面弯曲半径近似为1m。

双钢板-混凝土组合结构在沉管隧道中的发展与应用

沉管隧道在近年来修建的大型水下隧道工程中越来越多地得到运用,尤其是大型海底隧道。为研究沉管隧道的发展趋势,为工程设计提供参考,文中综述了沉管隧道的历史,总结出其结构形式经历了钢壳-钢筋混凝土结构、钢筋混凝土结构、双钢板-混凝土组合结构3个发展阶段。研究发现以配置横纵向隔板与加劲肋为特征的隔舱式双钢板-混凝土组合结构优点突出,是未来大型沉管隧道的发展方向,值得深化研究与探讨。目前双钢板-混凝土组合结构的相关研究较多,但针对隔舱式双钢板-混凝土组合结构面外性能的研究还比较欠缺,已有设计方法应用了混凝土规范但较为保守。在已有研究的基础上,该文进行3个抗弯梁式试验与3个抗剪梁式试验。试验研究发现已有抗弯设计方法与试验结果符合较好,但其考虑受压翼缘局部屈曲的构造要求可进一步放宽;已有抗剪设计方法低于试验值较多,偏于保守。基于理论分析,文中进一步提出考虑钢-混凝土组合抗剪机制与工字钢腹板抗剪机制两种机制相结合的抗剪设计方法,与试验结果符合较好且有一定富余。

硫酸盐-冻融循环下自感应水泥砂浆的耐久及压敏性能

为提升寒冷地区建筑结构的实时损伤监测效果,研究了硫酸盐-冻融循环作用下采用短切碳纤维与铁尾矿作为导电材料制备的自感应水泥砂浆的耐久与压敏性能。利用质量损失、相对动弹性模量及抗压强度损失为依据探讨耐久性能变化规律,以电阻率变化率-压应力的相关关系反映硫酸盐-冻融循环作用下压敏性能发展规律并解释其导电机理,并采用平均应力敏感系数评价硫酸盐-冻融循环作用下压敏性能稳定性。结果表明,碳纤维体积掺量为0.4%、铁尾矿替代率为30%(质量分数)组合掺入水泥砂浆时,其耐久性能与压敏性能均达到较高水平,但硫酸盐-冻融循环造成的孔洞与裂缝会导致铁尾矿碳纤维水泥砂浆电阻率变化率-压应力呈一阶指数衰减关系,可采用Plane模型来反映平均应力敏感系数衰减程度与冻融循环次数、铁尾矿替代率之间良好的相关关系。

Hyperoside protects the blood-brain barrier from neurotoxicity of amyloid beta 1–42

Mounting evidence indicates that amyloid β protein（Aβ） exerts neurotoxicity by disrupting the blood-brain barrier（BBB） in Alzheimer＇s disease. Hyperoside has neuroprotective effects both in vitro and in vivo against Aβ. Our previous study found that hyperoside suppressed Aβ1-42-induced leakage of the BBB, however, the mechanism remains unclear. In this study, bEnd.3 cells were pretreated with 50, 200, or 500 μM hyperoside for 2 hours, and then exposed to Aβ1-42 for 24 hours. Cell viability was determined using 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay. Flow cytometry and terminal deoxynucleotidyl transferase-mediated d UTP nick-end labeling assay were used to analyze cell apoptosis. Western blot assay was carried out to analyze expression levels of Bax, Bcl-2, cytochrome c, caspase-3, caspse-8, caspase-9, caspase-12, occludin, claudin-5, zonula occludens-1, matrix metalloproteinase-2（MMP-2）, and MMP-9. Exposure to Aβ1-42 alone remarkably induced bEnd.3 cell apoptosis; increased ratios of cleaved caspase-9/caspase-9, Bax/Bcl-2, cleav ed caspase-8/caspase-8, and cleaved caspase-12/caspase-12; increased expression of cytochrome c and activity of caspase-3; diminished levels of zonula occludens-1, claudin-5, and occludin; and increased levels of MMP-2 and MMP-9. However, hyperoside pretreatment reversed these changes in a dose-dependent manner. Our findings confirm that hyperoside alleviates fibrillar Aβ1-42-induced BBB disruption, thus offering a feasible therapeutic application in Alzheimer＇s disease.

Development of a Roebel structure transposed cable with in-plane bending of REBCO tapes

A compact High Temperature Superconductor(HTS)cable that can carry large current is crucial for developing high field superconducting accelerator magnets.Herein,we are reporting a high current and low AC loss REBCO cable that adopts the Roebel structure,but it is implemented by in‐plane bending stacked REBCO tapes directly to realize the transposition,instead of by punching REBCO tapes to the desired shape.The cable maximizes the utilization of the original REBCO tapes,so that the material cost is significantly reduced comparing with the present“Roebel”REBCO cable.Recently,a prototype cable has been successfully fabricated.The critical current of each REBCO tape after cabling shows no degradation,and the cable’s measured critical current is 1939.8 A at 77 K and self‐field,which is very close to the predicted critical current by simulation.Calculations also show that the AC loss of the cable is lower compared with that of a simple REBCO stack with the same cross‐section and current‐carrying capacity.In this paper,we first introduce the fabrication process of the cable.What follows is the measurement of the in‐plane bending performance of REBCO tapes.Then,we present the design and fabrication of the prototype cable together with current‐carrying performance tests.Finally,the AC loss calculation and analysis of the cable are reported.

Study on Support Vector Machine Based on 1-Norm

The model of optimization problem for Support Vector Machine(SVM) is provided, which based on the definitions of the dual norm and the distance between a point and its projection onto a given plane. The model of improved Support Vector Machine based on 1-norm(1-SVM) is provided from the optimization problem, yet it is a discrete programming. With the smoothing technique and optimality knowledge, the discrete programming is changed into a continuous programming. Experimental results show that the algorithm is easy to implement and this method can select and suppress the problem features more efficiently. Illustrative examples show that the 1-SVM deal with the linear or nonlinear classification well.

Oxidation of Al_2O_3-30%TiCN-0.2%Y_2O_3 Composite

The oxidation behavior of Al2O3-30%TiCN-0.2%Y2O3 composite and its effect on high temperature bending strength was studied. The result indicates that the mass gain during static oxidation of the material under normal atmosphere follows the parabolic law. Oxide increases with increasing temperature and prolonging time. It has good oxidation resistance. The product of oxidation of the material is TiO2. Therefore, the volume of the material expands. The oxide film is destroyed because residual stress inside the oxide film is released. Proper oxidation is beneficial to the improvement of bending strength of Al2O3-30%TiCN-0.2%Y2O3 composite. The strength increase is up to 4.5%.

缆线在铅垂面内弯曲的大变形曲线微分方程及其数值解法

针对民用与工业应用中经常用到的自然弯曲的软管和柔缆,归纳出5个共同特点,作为本文研究缆线的基本假设。从这些假设出发,根据受力和应力分析,首次推导了缆线在铅垂面内弯曲的大变形曲线方程。列出了多种端部约束条件下相对应的求解大变形曲线的方程组。证明了悬链线与纯弯曲线都是本文的特例。提出了获得数值解的递进法,并针对两端夹持约束的情形给出了具体算例。说明了存在多解的原因以及比较不同解稳定性的方法。