关键词： dissolution   ESPI   benzoic acid   mass transfer   mathematical modeling  

摘要： In many cases, classic in vitro tests are used to investigate dissolution from powders and solids. A problem with these kinds of tests is the frequent use of agitation, leading to a lumped description of the properties at the solid-liquid intetface. The hydrodynamic forces arising from agitation might have a nontrivial impact on the dissolution properties, thus calling for a comparison of results with those stemming from stagnant dissolution with the aim to increase the understanding of the dissolution process. Stagnant dissolution of compressed solid benzoic acid was examined using the noninvasive electronic speckle pattern interferometry technique in this study. The diffusion coefficient for benzoic acid in 37 degrees C water was measured using the same technique, and, by combining the results, the surface kinetics at the solid-liquid intetface were calculated. A comparison with previous dissolution data from a rotating disk suggests that the presence of convection can increase the observed surface kinetics. (C) 2010 American Institute of Chemical Engineers AlChE J, 57: 2610-2617, 2011

关键词： finite element   stress   flow regime   shell morphology   trade-off  

摘要： Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low-drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade-offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments;however, this flatter shape may also make the shells less capable of resisting predator-induced loads. We tested the idea that "lotic" shell shapes are weaker than "lentic" shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. "Lotic" shell shapes produced significantly higher stresses than "lentic" shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many-to-one mapping of shell shape onto strength, P. concinna experiences a trade-off in shell shape between hydrodynamic and mechanical performance. This trade-off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade-off in some cases, as changes in size

关键词： Receptor of advanced glycation end products   Surfactant-protein-type-B   Vascular surgery   Mechanical ventilation  

摘要： Receptor-of-Advanced-Glycation-End-products (RAGE) and Surfactant-Protein-type-B (SPB) are reported as lung injury markers. Unlike SPB, RAGE is secreted by several tissues, so that RAGE specificity as lung injury marker is questionable. We measured SPB and RAGE in 19 patients undergoing major vascular abdominal surgery. SPB and RAGE were measured before mechanical ventilation (T(0)), at 1st (T(1)), 2nd (T(2)) and, when present, 3rd (T(3)) hour of mechanical ventilation, and 1 h after extubation (T(POST)). Last data during mechanical ventilation, either T(2) or T(3), are reported as T(END). SPB and RAGE values were normalized for total protein (SPB(N) and RAGE(N)). SPB(N) and RAGE(N) increments from To to T(END) Were 56.2 [39.1] ng/mg (mean [75-25 percentile]) and 10.6[7.1] pg/mg, respectively. SPB values increased progressively during mechanical ventilation, whereas RAGE values increased at T(1) but not thereafter. SPB(N) increase (T(END) - T(0)), but not RAGE(N), was related to Delta PaO(2)/FiO(2) changes during mechanical ventilation (r=0.575, p = 0.01). Plasma RAGE(N) and SPB(N) kinetics in patients undergoing major vascular surgery are different. (C) 2011 Elsevier B.V. All rights reserved.

关键词： 工程机械行业   东方红柴油机   动力元件   上海新国际博览中心   宝马   展放   品牌   亚太地区  

摘要： 1展会情况 ＂上海宝马工程机械展＂是世界最大的工程机械展bauma在中国的延伸,同时也是2010年亚太地区最具影响力的国际性行业博览会。bauma China2010暨第5届中国国际工程机械、建材机械、工程车辆及设备博览会于2010年11月23—26日在上海新国际博览中心召开。

关键词： 最优激励轨迹   参数辨识   RRR机械臂   条件数  

摘要： 机器人动力学参数的精确辨识是对机器人进行精确控制的前提,参数辨识的精度与所采用的标定轨迹直接相关.以RRR机械臂为研究对象,建立该机械臂的动力学模型.在动力学参数辨识时,选择有穷傅里叶级数做为最优激励轨迹的表达式,通过最小化退化矩阵的条件数来获得最优激励轨迹中的参数,同时把各关节位置、速度和加速度的物理约束与激励轨迹结合起来,使获得的最优激励轨迹在物理意义上是可行的.通过在激励轨迹中指定频率范围来避免激励机器人的柔性特性,利用最小二乘法来辨识动力学参数.最后仿真验证了该辨识方法的有效性.

关键词： 汽/气动力机械泵   凝结水回收装置   凝结水回收成套装置  

摘要： 阐述了在杠杆浮球式疏水阀基础上发展起来的汽/气动力机械泵以及以汽/气动力机械泵为主机的高温凝结水回收成套装置系统的特点和用途。分析了以汽/气动力机械泵为主机的开式(闭式)高温凝结水回收成套装置系统在设计或工程中应用选型。高温凝结水回收成套装置和大排量浮球式疏水阀等可配套使用,通过大量实际应用的效果表明,该成套装置系统既具有广泛的适应性,又需与现场情况紧密结合。

关键词： 擒纵机构   动力学分析   碰撞  

摘要： 擒纵机构是机械手表中的关键部件之一,由于受到周期性受迫振荡而使其运动十分复杂。基于此,研究了瑞士叉瓦式擒纵机构的动力学问题,将擒纵机构的半周期分成4个部分,采用冲击微分方程理论,建立动力学模型,并用Matlab软件对其进行了动力学仿真计算。以Seiko7009a为实例,根据摆轮与时间、摆角与摆幅等关系,揭示了瑞士叉瓦式擒纵机构动力学特性,并分析了影响走时准确性的关键因素。结论表明:提出的数学模型在描述和预测动力学上具有较高的精度。

关键词： SUGINO动力头   孔加工   速技能  

摘要： MC记者：您能给我们介绍一下速技能在海内外市场的发展情况吗？ 林总：速技能是一家日本本土企业,产品主要是自动加工的动力头,主要应用于汽车、摩托车零部件的孔加工生产。除了在日本本土的发展以外,20多年来速技能在海外市场发展很迅速,共有七个子公司。

关键词： GEODYNAMICS   ROCK deformation   STRUCTURAL geology   EARTH'S mantle  

摘要： Comprehensive analysis of the parameters characterizing contemporary and neotectonic deformations of the Earth's crust and upper mantle developed in the Mongolia-Siberia area is presented. The orientation of the axes of horizontal deformation in the geodetic network from the data of GPS geodesy is accepted as an indicator of current deformations at the Earth's surface. At the level of the middle crust, this is the orientation of the principal axes of the stress-tensors calculated from the mechanisms of earthquake sources. The orientation of the axes of stress-tensors reconstructed on the basis of structural data is accepted as an indicator of Late Cenozoic deformations in the upper crust. Data on seismic anisotropy of the upper mantle derived from published sources on the results of splitting of shear waves from remote earthquakes serve as indicators of deformation in the mantle. It is shown that the direction of extension (minimum compression) in the studied region coincides with the direction of anisotropy of the upper mantle, the median value of which is 310-320 degrees NW. Seismic anisotropy is interpreted as the ordered orientation of olivine crystals induced by strong deformation owing to the flow of mantle matter. The observed mechanical coupling of the crust and upper mantle of the Mongolia-Siberia mobile area shows that the lithospheric mantle participated in the formation of neotectonic structural elements and makes it possible to ascertain the main processes determining the Late Cenozoic tectogenesis in this territory. One of the main mechanisms driving neotectonic and contemporary deformations in the eastern part of the Mongolia-Siberia area is the long-living and large-scale flow of the upper mantle matter from the northwest to the southeast, which induces both the movement of the northern part of the continent as a whole and the divergence of North Eurasia and the Amur Plate with the formation of the Baikal Rift System. In the western part of the regio

关键词： Collagen   Steered molecular dynamics   Elastic modulus   Mechanical behavior   Size effect  

摘要： Collagen is a fibrous protein that is responsible for structural integrity of various connective tissues such as bone, tendon, and skin. The mechanical properties of these hierarchical tissue structures are greatly influenced by presence of long and slender (similar to 300 long and similar to 1.5 nm in diameter) collagen molecules that impart strength and elasticity. The current molecular dynamics studies of collagen are limited to the use of short collagen molecules that are approximately 8.5 nm in length. This study investigates the mechanical behavior of the full-length collagen molecule and the short collagen by using steered molecular dynamics. The simulations were carried out at various loading conditions corresponding to different rates of pulling and springs of different stiffness were used to pull collagen molecules. The underlying mechanisms with respect to unfolding of collagen molecules differ significantly between short and full-length molecules when stretched in molecular dynamics simulations. These differences affect the mechanical properties of the short and full-length collagen molecules. In addition, the elastic modulus values are also affected by the pulling rate and the stiffness of the spring used by varying amounts for small and full-length collagen molecules. From this study, one may decipher the nuances of mechanical response of collagen in greater detail and recognize the similarities and differences in deformation mechanism of short and long collagen. (C) 2011 American Society of Civil Engineers.