摘要：用有限元方法模拟了不同形状钻头的破岩效果,研究了地层应力分布及裂缝延伸模式。按照国际钻井商协会(IADC)分类标准设计了14种钻头形状。设计了地层模型,给出了钻头尺寸、地层性质、网格划分方法和边界条件等。采用拟静态条件和质量缩放法以减少模拟时间、提高模拟精度。模拟结果表明,对于9种常用钻头形状,增加锥体高度高应力区面积会增大,而保径高度与产生的应力之间没有明显关系。减小保径高度,高应力区从鼻端和中心部位转移到保径区。对于非常用钻头形状,凸形钻头产生的应力场较大,双心钻头导眼体底部应力较集中。裂缝主要产生在保径区和鼻端,锥体高度和保径高度较大的钻头产生的垂直裂缝较长。使用平形和凸形钻头时没有产生较长的垂直裂缝。双心钻头可抑制保径区的垂直裂缝,却使地层更易出现水平裂缝,有中间段扩眼器的钻头造成的井壁损伤更小。

摘要：Synthesis and characterization of enzyme mimics with characteristic stability and high catalytic efficiency is an interesting field for ***,with the development of nanoscience and introducing of Fe3O4 magnetic nanoparticles as peroxidase mimics in 2007,various nanomaterials such as noble metals,metal oxides,and carbon materials were introduced as enzyme mimics(nanozymes).Various nanomaterials exhibit peroxidaselike activity,hence,most of the nanozymes are peroxidase *** the nanozyme based sensors were previously classified,the classifications have been focused on the type of nanozyme ***,the nanozyme based sensors were classified as peroxidase,hydrolase,and urease mimic-based ***,heretofore,these sensors are not classified based on the detection mechanism and principles of system *** aim of this review is the focus on the peroxidase mimic based colorimetric sensors as the most common nanozyme-based sensors and their classification based on principles of sensor design and review of the detection mechanism of the current mimic peroxidase based ***,some current challenges and future developments in this field are discussed.

摘要：Symmetry and pattern are valuable forms of beauty that can be cherished on both the macroscopic and molecular levels. Scientists have always appreciated the intimate connections between symmetry and molecular structures, which is reflected in their design of highly symmetrical compounds.

摘要：Tremor is an involuntary and oscillatory movement disorder that makes daily activities difficult for affected patients. Hand tremor-suppression orthoses are noninvasive, wearable devices designed to mitigate tremors. Various studies have shown that these devices are effective, economical, and safe;however, they have drawbacks such as large weight, awkward shape, and rigid parts. This study investigates different types of tremor-suppression orthoses and discusses their efficiency, mechanism,benefits, and disadvantages. First, various orthoses(with passive, semi-active, and active mechanisms) are described in ***, we look at how additive manufacturing(AM) has progressed recently in making sensors and actuators for application in tremor orthoses. Then, the materials used in AM are further analyzed. It is found that traditional manufacturing problems can be solved with the help of AM techniques, like making orthoses that are affordable, lighter, and more customizable. Another concept being discussed is using smart materials and AM methods, such as four-dimensional(4D) printing, to make orthoses that are more comfortable and efficient.

摘要：Hydroplaning speed can be affected by pavement texture depth,thickness of water film,tire pressure and tread *** this study,to understand the influence of pavement texture on the hydroplaning speed,a new lab-scale apparatus has been designed and *** lack of proportion between linear movement of vehicle shaft and the wheel rotation was found to be a good index to determine hydroplaning threshold.A 5%drop in the ratio of wheel-to-axle rotation has been assumed as an index to determine hydroplaning *** on the measures,a simplified model was developed that is able to predict the hydroplaning speed depending on pavement's texture *** results indicated that a 77%increase in mean texture depth cause 9%increase in hydroplaning threshold speed.

摘要：黏土矿物对硫浮选有负面影响。在本研究中,研究了黏土矿物(高岭石-蒙脱石)对黄铜矿浮选的影响,旨在提出能够消除负面影响的解决方案。进行ζ-电位测量和浮选实验,采用中心复合设计方法,选取起泡剂浓度、分散剂浓度、泡沫高度、空气流速和黏土量为变量。在对测试结果的评估中,将这5个重要变量定为因变量。随着黏土量的增加,黄铜矿品位降低,而黄铜矿回收率、黄铁矿回收率和动态泡沫稳定性增加。黄铜矿浮选的负相互作用顺序为蒙脱石>高岭石,说明使用蒙脱石可获得较大的气泡直径。对矿石中的黏土类型(高岭石和蒙脱石)适用的浮选条件进行数学建模,该模型预测了与矿石的黏土比的相关条件随时间的变化,以及浮选获得的品位回收值。

摘要：This study aims to introduce a novel hybrid design with a combination of two more common mechanisms for improving the capacity of systems in absorbing the kinetic energy of moving vehicles or devices. This new model consists of two individual mechanisms, i.e., expansion of a circular tube accompanied by crushing of an inner tube, which dissipate the energy through friction, plastic deformations and failures of inner tube. This study comprises 24 case studies surveyed under two different design controls, constant mass and constant volume, for comparing purposes. Finite element simulations are utilized so as to investigate models’ deformations and to extract some crashworthiness parameters in aid of representing the efficiency of the mechanism as well as conducting a parametric study between three different profiles of inner tube. This study shows that models with inner circular and hexagonal tube profile absorb higher amount of energy due to experiencing three different modes of energy dissipation systems, including folding, shear and ductile damages.

摘要：宏观流动到微流动不单是“量”的变化，而且有“质”的不同。在微流动中，由于微尺度效应，主导流动的作用力发生变化，惯性力不再占主导地位；在宏观尺度流动中可以忽略的表面效应和壁面滑移等现象，开始凸现出来，这就导致了微流动中出现了与宏观流动不同的现象和规律。本文研究微流动问题中的若干微尺度效应：包括微喷管中气体流动的特性、微槽道中的稀薄气体效应和分子泵内的流动问题。这些研究对于设计和开发新的微机械机电设备是非常重要的。

摘要：In this paper, among other things, the author studies the weak^＊-closed left translation invariant complemented subspace of semigroup algebras and group algebras. Also, the author studies the relationships between projections and amenability.

摘要：The feasibility and kinetics of lead recovery from the slag of traditional lead melting furnace using chloride leaching were *** effects of operating parameters such as leaching time,NaCl concentration,FeCl3concentration,liquid/solid ratio,stirring rate,temperature,and particle size on recovery of lead were studied and the optimization was done through the response surface methodology(RSM)based on central composite design(CCD)*** optimum conditions were achieved as follows:leaching time60min,80°C,stirring rate800r/min,NaCl concentration200g/L,FeCl3concentration80g/L,liquid/solid ratio16,and particle size less than106μ*** than96%of lead was effectively recovered in optimum *** on analysis of variance,the reaction temperature,liquid/solid ratio,and NaCl concentration were determined as the most effective parameters on leaching process,*** study revealed that chloride leaching of galena is a first-order reaction and the diffusion through solid reaction product and chemical reaction control the *** activation energy of chloride leaching of galena was determined using Arrhenius model as27.9kJ/mol.