Influence of layer orientation and interlayer bonding force on the mechanical behavior of shale under Brazilian test conditions

The mechanical behavior of inherently anisotropic shale rocks under Brazilian test conditions are investigated in this study based on experimental studies and numerical simulations. The effects of the weak lamination planes and interlayer bonding force of these layers on the failure strength and fracture patterns are studied systematically. Numerical simulations using particle flow code in two dimensions based on the discrete element method showed a good agreement with the experimental results in the failure strength and fracture patterns. The shale revealed strong anisotropic behavior with the failure strength perpendicular to the lamination plane greater than failure strength parallel to lamination plane. The failure strength of the different interlayer bonding force against the layer orientations changed significantly. Four types of fracture patterns were observed: curved fracture, broken-linear fracture, layeractivated fracture, and central-linear fracture. The observed fracture patterns are either or a combination of tensile and/or shear fractures. Increase in interlayer bonding strength decreased the quantity of micro cracks and this directly led to reduction in the anisotropic behavior. Overall the layer orientation and interlayer bonding force of the shale thus play a very important role in the anisotropic behavior of the shale.

Cast-rolling force model in solid-liquid cast-rolling bonding(SLCRB) process for fabricating bimetal clad strips

Based on twin-roll casting, a cast-rolling force model was proposed to predict the rolling force in the bimetal solid-liquid cast-rolling bonding(SLCRB) process. The solid-liquid bonding zone was assumed to be below the kiss point(KP). The deformation resistance of the liquid zone was ignored. Then, the calculation model was derived. A 2D thermal-flow coupled simulation was established to provide a basis for the parameters in the model, and then the rolling forces of the Cu/Al clad strip at different rolling speeds were calculated. Meanwhile, through measurement experiments, the accuracy of the model was verified. The influence of the rolling speed, the substrate strip thickness, and the material on the rolling force was obtained. The results indicate that the rolling force decreases with the increase of the rolling speed and increases with the increase of the thickness and thermal conductivity of the substrate strip. The rolling force is closely related to the KP height. Therefore, the formulation of reasonable process parameters to control the KP height is of great significance to the stability of cast-rolling forming.

Effect of ultrasonic power and bonding force on the bonding strength of copper ball bonds

Copper wire, serving as a cost-saving alternative to gold wire, has been used in many high-end thermosonic ball bonding applications. In this paper, the bond shear force, bond shear strength, and the ball bond diameter are adopted to evaluate the bonding quality. It is concluded that the ef/~cient ultrasonic power is needed to soften the ball to form the copper bonds with high bonding strength. However, excessive ultrasonic power would serve as a fatigue loading to weaken the bonding. Excessive or less bonding force would cause cratering in the silicon.

Effects of combination modes of favorable growth unit of Al(OH)_3 crystals precipitating on Van der Waals and chemical bond force

The dipole moment, total energy, atomic charge, orbital population and orbital energy of four representative combination models of the favorable growth unit Al6（OH）18（H2O）6 of Al（OH）3 crystals precipitating are calculated by ab initio at RHF/STO-3G, RHF/3-21G, RHF/6-31G levels and DFT at RB3LYP/STO-3G, RB3LYP/3-21G, RB3LYP/6-31G levels with Dipole & Sphere solvent model. The effect of various combination models on Van der Waals force is analyzed using dipole moment and molecular radius, and that on chemical bond force is analyzed using total energy, orbital population and orbital energy.

Calculation of Bond-length, Bond-energy and Force Constant of Hydrogen Molecule by Classical Mechanics

Until recently the hydrogen molecule structural parameters are calculated with the methods of quantum mechanics. To achieve results close to experimental values, the wave function used is complicated and has no clear physical meaning. Because the distribution of the electron probability density is a statistical rule, the macro time has actually been used in the concept on a electron cloud graph. Here are obtained three formulas with a classical mechanics method on the bond length r e , bond energy D e and force constant k of the ground state hydrogen molecule, which have a clear physical meaning but no artificial parameters, and compared with experimental values, the relative errors are respectively less than 1%, 2% and 4%.

Stability of focal adhesion enhanced by its inner force fluctuation

Cells actively sense and respond to mechanical signals from the extracellular matrix through focal adhesions. By representing a single focal adhesion as a cluster of slip bonds, it has been demonstrated that the cluster often became unstable under fluctuated forces. However, an unusual case was also reported, where the stability of the cluster might be substantially enhanced by a fluctuated force with a relatively low fluctuation frequency and high fluctuation amplitude.Such an observation cannot be explained by the conventional fracture theory of fatigue. Here, we intensively investigate this intriguing observation by carrying out systematic parametric studies. Our intensive simulation results indicate that stability enhancement of this kind is in fact quite robust, which can be affected by the stochastic features of a single bond and the profile of the fluctuated forces such as the average value of bond force. We then suggest that the fluctuation of traction force within a focal adhesion might enhance its stability in a certain way.

A STUDY OF HIGH LOFT NONWOVEN FABRICS USING POWDER BONDING TECHNOLOGY

In this paper, two types of high loft nonwoven fabrics have been constructed in the laboratory apparatus made by ourselves with different binders (polyamide and polyethylene powder) and varying binder contents (10%, 20%, 30% and 40%). The tensile and compression properties of these nonwoven fabrics were tested. It was found that one can reduce powder binder content to increase loft and softness of nonwoven fabrics, but it has to sacrifice its tensile strength. Adhesion force between binder and single fibre was also explored. The experiments showed that the adhesion force at the interface between binder and fibre depends on the fibre variety, the fibre surface morphology, heating temperature and heating time etc..

Study on Infrared Spectra and Chemical Bonding of the Cluster Anion[Cl_2FeS_2MoS_2Cu(PPh_3)_2]￣-

The Fourier transform infrared spectra of the cluster anion[Cl2Fe2S2MoS2Cu(PPh3)2]- are measured between 550 and 90 cm(-1).The empirical assignments have been made for the vibration bands of main valence bonds.In order to verify the assignments of the bands and obtain the force constants the approximate normal coordinate analysis for the title anion has been carried out.It is found that the calculated frequencies are in good agreement with the observed ones.While Quantum-Chemical calculation is used to elucidate the chemical bonding characteristics for the title anion.

Cast-rolling force model of multi-roll solid–liquid cast-rolling bonding process for fabricating metal cladding materials

Based on twin-roll casting technology and multi-roll groove rolling technology,a Multi-Roll Solid-Liquid Cast-Rolling Bonding(MRSLCRB)process was proposed to fabricate Cu/steel cladding bars,which processes the advantages of short flow and high-efficiency.However,it is a typical 3-D thermal-fluid-mechanics coupled problem,and determining cast-rolling force is difficult during the equipment design.Therefore,the geometrical evolution of the cast-rolling area was studied,laying the foundation to establish contact boundary equations and analyze mechanical schematics and metal flow.Then,a 3-D steady-state thermal-fluid coupled simulation model,including casting roll,substrate bar,and cladding metal,was established.The Kissing Point(KP)height,average outlet temperature,and process window were predicted,and simulation results of the three-roll layout indicate that the KP distribution along the circumferential direction can be considered uniform.Hence,the engineering cast-rolling force model was derived based on the differential element method and plane deformation hypothesis.The accuracy was verified by the 3-D finite element model,and the influences of process layouts and technological parameters on the castrolling force were analyzed.Through the indirect multi-field coupled analysis method,the temperature–pressure evolution and reasonable process window can be predicted,which provides a significant basis for guiding equipment design and improving product quality.

Seepage Mitigation in Hydropower Dams by Optimization in Roller Compacted Concrete Interlayer (Monoliths) Joint Bonding Technology

Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.

锚杆岩体界面载荷传递规律及锚固长度设计

为揭示巷道围岩锚固界面脱粘失效机理,量化锚杆支护设计参数,采用三线性粘结滑移模型进行理论分析,对轴向载荷作用下锚固脱粘失效全过程中,锚固段界面剪应力、锚杆轴力分布演化规律以及界面极限锚固力进行研究,根据锚固段长度不同,得到两种界面剪应力分布演化类型。研究结果表明:当锚固长度较短时,界面剪应力存在全长软化阶段;当锚固长度较长时,界面剪应力存在弹性-软化-滑移三段共存阶段。锚固粘结界面弹性段、软化段、摩擦段内的剪应力分别呈现双曲余弦函数衰减分布、余弦函数上升分布、均匀分布规律,锚杆轴力随界面剪应力分布演化呈现多种形态的衰减分布规律。根据锚固界面模型解析计算获得极限锚固力,当不考虑脱粘摩擦力时,极限锚固力随锚固长度的增加趋近于某一固定值;当考虑脱粘摩擦力时,增加锚固长度能够持续提高锚固界面安全系数。研究成果可为锚固机制分析、锚杆支护参数设计提供理论参考。

半导体晶圆键合加压精确控制方法

晶圆键合质量受键合压力控制精度显著影响。对于本身有一定翘曲度的晶圆,容易在键合过程中产生非预期位移,造成键合工艺偏差,甚至碎片。因此,提出了一种基于模糊PID(比例-积分-微分)和RBF(Radial Basis Function)径向基函数神经网络算法的半导体晶圆键合压力控制方法。由于加入了模糊PID和深度学习算法控制,使得键合工艺过程响应更迅速,控制更精准,且安全性更高。采用铝样片进行加压试验,结果表明RBF神经网络模糊PID控制算法能够满足压力精度为±1%的控制需求。

径向脉冲力下薄壁内衬再生复合管层间应力分析

为深入研究径向脉冲力对薄壁内衬复合管层间应力的影响,基于以建立的层间相互作用本构关系,对X52N钢板和玻璃钢板通过黏结而成的复合板进行模态试验,并与有限元模拟结果进行对比,验证了胶层本构在有限元模拟中的可行性。通过建立薄壁内衬复合管有限元分析模型,研究径向脉冲力作用下,外基层管厚度与衬层厚度的比值及黏结强度对层间应力状态的影响。研究结果表明,随着层厚比的增加,层间应力的改变较为显著,而黏结强度的影响相对较小。在一定层厚比范围内,外基层管的支持效应能有效降低层间应力,但外基层管厚度也不宜过厚,过厚的外基层管会增加其质量和刚度,进而加大对内衬层的约束作用,从而导致层间应力增加。

红外探测器芯片高可靠性键合工艺研究

金丝键合工艺广泛应用于红外探测器的封装环节。实验选用25μm金丝,基于正交试验法,根据键合拉力值确定键合的最佳工艺参数。通过优化超声压力、超声功率、超声时间及接触力等工艺参数组合,改善了键合引线的电气连接性能和连接强度,从而提高芯片系统的信号传输质量。提出的引线键合工艺参数组合适用于红外探测芯片的键合。

含Benzo[a]azulene单元的锯齿状梯形共轭聚合物的表面在位合成

梯形共轭聚合物(CLPs)因其独特的光电性质而受到广泛关注。绝大多数CLPs是通过溶液方法合成的,但近年来,在超高真空环境中进行的表面原位合成策略逐渐崭露头角,成为CPL合成的新方法。表面原位合成方法能够克服传统溶液合成的限制,如随着聚合度增加而受限的溶解度和结构稳定性,从而实现复杂共轭结构的精确合成。Azulene衍生物是在表面合成非苯型CLPs的有吸引力的前体。与传统的只含六元环的CLPs相比,使用烷基取代的azulene作为前体分子,有望获得具有复杂骨架结构的CLPs,从而调控其电子性质,但目前很少有人探索这种策略。本文报道了3,3'-二溴-2,2’-二甲基-1,1’-联薁(DBMA)在Au(111)表面上的热化学反应。在室温的Au(111)衬底上,我们发现沉积的分子在重构表面的fcc(面心立方堆积)区域形成无定型的聚集体,并在100℃以下保持形貌不变。当退火温度高于150℃后,DBMA发生脱溴反应并与金原子络合形成具有复杂空间立体结构的2,2’-二甲基-1,1’-联薁有机金属聚合物,并展现出迥异的图像特征。随后在更高温度下退火,有机金属聚合物脱去金属原子并经历碳碳偶联反应。该过程伴随着甲基与相邻薁单元之间的分子内环化反应,形成了含有benzo[a]azulene单元的梯形共轭聚合物。有趣的是,我们发现当一侧甲基参与反应并在聚合物中形成六元环时,会显著地弯折聚合物链,使得另一侧甲基与薁单元之间的距离增加,并抑制预期的环化过程。我们通过键分辨扫描探针显微镜对反应过程中的相关结构进行了研究,发现反应结果与反应中间结构的应力关联紧密。我们的结果表明,烷基取代的azulene前体可应用于非苯型碳纳米结构的表面合成,并有望实现扩展的非苯型二维碳纳米结构。

基于离散元法的耕层残膜拉伸性能研究

由于耕层残膜回收机关键农机部件设计优化过程中缺乏准确的残膜离散元模型参数,在一定程度上制约了耕层残膜回收机残膜受力机理分析与机构优化改进。本文以棉田耕层残膜为研究对象,对耕层残膜含量和极限拉伸力进行测定,得到不同耕层深度、不同厚度的残膜含量和极限拉伸力。根据测定结果,利用EDEM软件选用Hertz-Mindlin with Bonding接触模型对耕层残膜进行离散元模型参数标定,选用单位面积法向刚度、单位面积切向刚度、临界法向应力、临界切向应力、粘结半径、接触半径为试验因素。通过Plackett-Burman试验,确定影响Bond键的主要参数有单位面积法向刚度、临界法向应力和粘结半径。通过最陡爬坡试验和Box-Behnken试验,最终确定最优的Bonding模型显著参数单位面积法向刚度、临界法向应力、粘结半径分别为2.36×10^(5) N/m^(3)、6.47×10^(4) Pa、0.004 mm,对参数进行了仿真试验验证,误差为5.88%,满足要求。通过对比物理试验与仿真试验的拉伸过程耕层残膜状态与拉伸曲线,表明了耕层残膜模型合理性,为后期耕层残膜回收机仿真与膜土分离机理研究提供了理论支撑。

溶液酸碱性对氧化石墨烯自组装成膜结构与性能的影响

相比石墨烯,氧化石墨烯(GO)在稳定性、可溶性、功能化修饰和作为载体的应用等方面颇有优势,使得其在催化、分离过滤、传感、储能等领域中更具实际可行性和应用价值。在GO的宏观组装过程中,溶液酸碱性强烈地影响GO自组装过程,但其中的影响规律尚不明晰。因此,通过调控高浓GO溶液的pH值制备GO厚膜,研究了GO与分散介质之间的相互作用力变化对GO组装及宏观组装材料性能的影响。研究结果显示,厚GO膜的各项性能随着溶液pH值的变化而有显著差异。当GO溶液的pH值为弱碱性(pH值为9)时成膜,GO膜的拉伸强度达到229.29 MPa,是pH值为4时GO膜强度的7倍以上,同时,当GO溶液的pH值为9时成膜,GO膜的电导率为27800 S/m,是pH值为4的1.7倍以上。一系列分析结果表明,当溶液pH值为弱碱性时,GO表面的部分羟基和羧基被还原,使得片层上同时存在氧化区域和sp^(2)碳区域,氢键作用力和静电排斥作用力诱导片层的面面排列,而π-π作用力驱动片层的紧密堆积,当sp^(2)碳区域的比例接近氧化区域时,其组装驱动力从氢键相互作用力主导转变为由氢键和π-π相互作用共同诱导。最终发现,当两种作用力的比例相差较大时,会导致片层堆积间距较大(氢键作用力更大)或堆积排列有序性降低(π-π相互作用更大)。因此,在以GO为主要成分制备宏观材料时,溶液的酸碱环境将极大影响组装结构的有序性和应用性能,本研究对石墨烯基宏观材料的结构设计和性能提升具有一定的启发意义,石墨烯薄膜具有优异的导热性和导电性、柔韧性和坚固性,可以作为电子产品的候选者。

连续性与间歇性降雨下土壤结皮与入渗的关系模拟

[目的]为探究连续性和间歇性降雨条件下土壤结皮与入渗性能间的变化关系。[方法]选取3种典型耕作层黄土,通过室内模拟降雨试验,分析不同降雨条件下土壤结皮强度和黏结力与入渗性能的关系。[结果](1)入渗性能随连续性降雨历时及间歇性降雨场次的增加而减小;同等降雨历时和降雨强度下,间歇性降雨的减渗效应高于连续性降雨。(2)土壤结皮强度和黏结力随连续性降雨历时和间歇性降雨场次的增加而增加;褐土和黑垆土的入渗性能与结皮强度和黏结力呈显著线性相关(p<0.05),连续性降雨历时越长、间歇性降雨场次的越多,土壤结皮强度、黏结力以及减渗效应越大;沙壤土的入渗性能与结皮强度和黏结力则呈显著的非线性相关(p<0.05)。(3)结皮的MWD和GMD越小,入渗性能越差,减渗效应越大;关联度分析结果显示,间歇性降雨对入渗性能的影响较高。[结论]相同雨强条件下,间歇性降雨下能形成更坚实的结皮,对土壤入渗性能的削弱能力更强。研究结果可为黄土高原防治水土流失、有效利用水资源提供参考依据。

T细胞力学免疫学研究进展

T细胞是获得性免疫的核心之一,T细胞受体(T cell receptor,TCR)对抗原的特异性识别是启动抗肿瘤、抗病毒免疫应答的关键过程。近年来的研究表明力在T细胞免疫反应中起着重要的调控作用,为力学免疫学这一新兴领域奠定了基础。本文重点讨论力协助TCR区分特异性抗原和自身非特异性抗原的机制,以及力在启动TCR跨细胞膜信号传导及触发T细胞激活过程中发挥的关键作用。总结了力学免疫学研究中新的生物物理单分子工具和先进的成像技术,这些工具的能够在分子和细胞尺度上深入揭示力作用的重要性。本文基于国内外专家团队的研究成果,并结合本团队研究工作,对力在T细胞功能中的作用进行总结探讨,为深入理解力学免疫学领域的前沿热点和探索新的研究方向提供系统框架。

小口径自动炮 FORC 原理

武装直升机的出现和发展给自动炮后坐力提出了更高的要求，如何进一步降低小口径自动炮的后坐力是现代火炮技术研究中的一项重要课题。最佳后坐力控制原理（ＦＯＲＣ）是小口径自动炮减小后坐力的一种新的理论和方法。该文在理论研究的基础上，分析了ＦＯＲＣ原理的特性，并以一种ＦＯＲＣ装置为例，利用系统动力学键合图理论建立了ＦＯＲＣ装置的动力学模型，进行计算机仿真，得到了其动力学过程的特性曲线，验证了ＦＯＲＣ原理的可行性。