流体润滑用压力敏感量子点传感器材料研究进展

流体润滑广泛存在于工程领域,润滑接触区各点局部压力的测量对研究机械润滑状态、保证系统平稳运行具有重要作用.量子点具有优异的化学和光致发光稳定性以及优异的光学性能,其对压力的敏感性使其应用于流体润滑领域监测压力成为可能.为此,本文中总结了研究常用的压力敏感量子点材料以及常用的制备方法,介绍了量子点的压力依赖性原理,并分别从原位压力试验和第一性原理计算两方面对量子点压力依赖性常用的研究方法进行了总结,最后,从工程应用角度对量子点的应用潜力以及目前仍存在的问题和挑战进行了介绍.     

超晶格材料光电性能及其相关力学问题研究进展

超晶格材料是由两种或两种以上性质不同的薄膜交替生长而形成的人工周期性结构材料.超晶格材料中具有连续介质力学``小尺度效应'和量子力学``大尺寸量子效应'并存的现象.阐述了超晶格材料周期结构特征和制备技术,介绍了超晶格材料量子化能带结构及其奇异的光电特性.探讨了超晶格材料微观结构及其变形机理,归纳了超晶格材料量子化电子结构的几种常用计算方法,如紧束缚方法、赝势方法和k$ \cdot $p微扰方法等.重点介绍了外力场和应变对超晶格材料量子化电子结构及其光电性质影响,包括作者所在研究小组近期在端部摩擦、点载荷、有限界面和各向异性等对超晶格微观变形及其量子化电子结构影响的跨尺度一体化研究方面的最新工作进展.      

典型纳尺度结构的热振动

热振动是一定温度下纳尺度结构的固有运动,对其动力学行为有着重要的影响.当空间进入纳米尺度,结构呈现离散性,量子效应、边界效应、范德华力等变得不可忽略,纳尺度结构在热噪声随机激励下的动力学行为表现出众多异乎寻常的特性.以碳纳米管和石墨烯为代表的纳尺度碳材料具有优良的力学、电学和化学性质.在此介绍多种针对纳尺度结构热振动问题的研究方法、及碳纳米管和石墨烯的低温热振动、碳纳米管的非线性热振动研究进展.     

凝聚态炸药爆轰测试技术研究进展

爆轰物理学科仍然是以实验为主的一门科学,爆轰测试技术的不断进步仍然是爆轰物理学科发展的主要推动力.本文在阐述凝聚态炸药爆轰性能主要几个研究方面的基础上,从光学测试技术和电学测试技术两个方面系统介绍了凝聚态炸药爆轰测试技术及其应用.通过对现代爆轰测试技术进展的阐述,分析了凝聚态炸药爆轰测试研究面临的问题,展望了爆轰测试技术的发展前景.      

超轻多孔金属材料的多功能特性及应用

超轻多孔金属是近年来随着多样化需求的材料制备以及机械加工技术的迅速发展而出现的一类新颖多功能材料, 是材料的选择及其性能研究的新课题. 本文介绍有关多孔金属材料与结构基础研究的国内外研究现状和发展趋势, 涉及材料制备、性能表征等方面, 着重于探讨多孔金属的多功能复合特性及其在国民经济和高技术中的应用.      

等离子体电化学法制备金、银纳米颗粒与碳量子点的研究进展及关键问题

通过高电压击穿气体可产生大量的自由电子和离子,形成对外大致呈电中性的气体放电等离子体,同时荷能粒子引发的各种过程会在等离子体中产生种类丰富的反应性物质.大气压低温等离子体具有非平衡特性,因此在低气体温度下可保持高反应活性.当大气压低温等离子体与溶液接触时,可形成等离子体电化学系统.在等离子体-液体界面存在电荷和物质转移,可引发一系列物理化学及电化学过程,从而使得等离子体电化学系统可广泛应用于多种领域,纳米材料合成即是其众多应用之一.当前,已有大量的研究利用等离子体电化学法合成纳米材料,也存在相关的综述文章,但缺乏聚焦于金、银纳米颗粒与碳量子点相关的综述,因此我们在此综述了近年来采用等离子体电化学方法制备金、银纳米颗粒与碳量子点的研究成果.首先介绍了等离子体电化学方法,接着考察了制备金、银纳米颗粒与碳量子点的实验结果及其应用的进展,最后讨论了当前研究中遇到的问题与挑战,并提出了解决方案.     

轻质多孔材料研究进展

高超声速武器是军事装备的发展方向,在未来战争中起着重要作用.轻质材料是高超声速飞行器设计与制造的关键技术之一,它是实现高超声速飞行器高超声速、高机动性、远程打击等性能的基础和保障.高超声速飞行器轻质材料主要有蜂窝材料、泡沫金属材料、点阵材料.这些材料具有超轻、高比强、高比刚度、高强韧、高能量吸收等优良机械性能,以及减震、散热、吸声、电磁屏蔽等特殊性质,它兼具功能和结构双重作用,是一种性能优异的多功能材料.本文从材料制备、结构设计、力学与物理性能表征等方面综述了高超声速飞行器轻质材料的研究与应用现状,比较了三种轻质材料的机械和物理性能,重点评述了新型点阵材料的制备工艺、结构构型、力学及其他性能,指出了其发展趋势.     

恒磁场作用下压磁/压电半导体复合圆柱壳的耦合响应分析

本文针对由压磁材料和压电半导体材料组成的无限长复合圆柱壳结构,理论研究了其在径向恒磁场作用下结构内的多场耦合力学响应问题。为解析求解方便,文中分别采用单向耦合法和线性全耦合法,导出复合圆柱壳内位移场、电场、载流子等物理量的解析表达式。利用导出的解析表达式,数值分析了磁场大小和半导体层厚度比对结构内电势、电场和载流子的影响。计算结果表明：磁场和厚度比均可用来有效调控半导体层内的电学量,复合圆柱壳结构的厚度比有一个最优区间。     

恒磁场作用下压磁/压电半导体复合圆柱壳的耦合响应分析

本文针对由压磁材料和压电半导体材料组成的无限长复合圆柱壳结构,理论研究了其在径向恒磁场作用下结构内的多场耦合力学响应问题。为解析求解方便,文中分别采用单向耦合法和线性全耦合法,导出复合圆柱壳内位移场、电场、载流子等物理量的解析表达式。利用导出的解析表达式,数值分析了磁场大小和半导体层厚度比对结构内电势、电场和载流子的影响。计算结果表明：磁场和厚度比均可用来有效调控半导体层内的电学量,复合圆柱壳结构的厚度比有一个最优区间。     

多孔金属及其夹芯结构力学性能的研究进展

高孔隙率多孔金属及其夹芯复合结构是一种物理功能与结构一体化的新型、轻质高强材料/结构,具有高比强度、高比刚度和优良的吸能和缓冲性能等多种功能,引起了学术界和工程界众多研究者的极大关注. 本文概述了轻质多孔金属及其夹芯结构的制备方法、多功能特性及其应用,介绍了多孔金属夹芯结构元件(梁、板、壳)遭受准静态和动态冲击载荷下的理论、实验和模拟方面的国内外研究现状,分析和讨论了多孔金属及其夹芯结构力学行为研究中的研究手段和基本问题,重点关注了多孔金属夹芯结构的变形/失效、动态响应和能量吸收.     

Analysis of quantum-dot-induced strain and electric fields in piezoelectric semiconductors of general anisotropy

Characteristics of the self-organized quantum dots (QDs) such as electron and hole energy levels and wave functions are dependent to the state of strain and electric field produced during the growing process of QDs in a semiconductor substrate. The calculation of the strain and electric field is one of the most challenging components in the QDs simulation process. It involves material anisotropy induced coupling between the elastic and electric fields and it must include the full three-dimensional and usually intricate shapes of the QDs. Numerical simulations are often performed by finite difference, finite element, or atomistic techniques, all require substantial computational time and memory. In this paper, we present a new Green’s function approach which takes into account QDs of arbitrary shape and semiconductor substrates with the most general class of anisotropy and piezoelectricity. Following the literature of micromechanics, the problem is formulated as an Eshelby inclusion problem of which the solution can be expressed by a volume-integral equation that involves the Green’s functions and the equivalent body-force of eiegenstrain. The volume integral is subsequently reduced to a line integral based on exploiting a unique structure of the Green’s functions. The final equations are cast in a form that most of the computational results can be repeatedly used for QDs at different locations—a very attractive feature for simulating large systems of QD arrays. The proposed algorithm has been implemented and validated by comparison with analytical solutions. Numerical simulations are presented for pyramidal QDs in the substrates of gallium arsenide (GaAs) (0 0 1).     

Thermomagnetic effect with microtemperature in a semiconducting photothermal excitation medium

The main goal of this paper is to focus on the investigation of interaction between a magnetic field and elastic materials with microstructure, whose microelements possess microtemperatures with photothermal excitation. The elastic-photothermal problem in one-dimension is solved by introducing photothermal excitation at the free surface of a semi-infinite semiconducting medium (semiconductor rod). The integral transform technique is used to solve the governing equations of the problem under the effect of the microtemperature field. The analytical expressions for some physical quantities in the physical domain are obtained with the heating boundary surface and free traction. The numerical inversion technique is used to obtain the resulting quantities in the physical domain. The obtained numerical results with some comparisons are discussed and shown graphically.     

Thomson and rotation effects during photothermal excitation process in magnetic semiconductor medium using variable thermal conductivity

This study investigates a strong magnetic field acting over an elastic rotator semiconductor medium. The Thomson effect due to the magnetic field during the photothermal transport process is studied, and the thermoelectricity theory is used to explain the behavior of waves in the homogenous and isotropic medium under the effect of variable thermal conductivity. The variable thermal conductivity is considered as a linear function of the temperature. The two-dimensional deformation equations are used to describe the overlaps among plasma, electrical, thermal, and magneto-elastic waves.The charge density of inertia-particles is considered as a function of time for studying the induced electric current. The normal mode analysis is used to obtain the exact solutions of the physical field distributions as part of this phenomenon. To obtain the complete solutions of the physical field quantities, the certain mechanical loads, electromagnetic effects, thermal effects, and plasma recombination process are applied herein. The results of the physical distributions are graphically depicted and discussed in consideration of the internal heat source, rotation, and Peltier coefficient.     

方形固-液声子晶体的全反射隧穿及其多通道滤波

为了研究一维固-液结构方形声子晶体中弹性波的全反射隧穿效应,利用传输矩阵法计算了弹性波在大于全反射角入射一维固-液结构方形声子晶体的透射率。在透射波中发现了全反射隧穿效应,并且全反射隧穿峰具有优良的多通道滤波特性。得出了一维固-液结构声子晶体的全反射隧穿的滤波特性随周期数、模式量子数、边长的变化规律。为设计性能优良的多通道声子晶体滤波器提供了理论依据。     

Statistical particle tracking velocimetry using molecular and quantum dot tracer particles

We present a statistical approach to particle tracking velocimetry developed to treat the issues associated with nanometer-sized tracer particles such as fluorescent molecules and quantum dots (QDs) along with theory and experimental results. Extremely small tracers pose problems to traditional tracking methods due to high levels of thermal motion, high levels of intensified camera noise, high drop-in/drop-out rates and, in the case of QDs, fluorescence intermittency (“blinking”). The algorithm presented here compensates for these problems in a statistical manner and determines the physical velocity distributions from measured particle displacement distributions by statistically removing randomly distributed, non-physical tracking events. The algorithm is verified with both numerically simulated particle trackings and experiments using 54 nm diameter fluorescent dextran molecules and 6 and 16 nm diameter QDs.     

分数阶理论下实心球体受热冲击作用的渐进分析

基于分数阶广义热弹性理论,针对实心球体在外表面受均匀热冲击作用下的一维广义热弹性问题进行研究分析. 利用热冲击的瞬时特征,借助于Laplace 正、反变换技术及柱函数的渐进性质,推导了热冲击作用周期内位移场、温度场和应力场的渐进表达式. 通过计算,得到了不同传热能力下受热冲击作用时热波、热弹性的传播规律以及位移场、温度场及应力场的分布规律. 结果表明:分数阶参数取值的不同,热波、热弹性波的传播以及各物理场的分布均有所不同,分数阶参数可视为延迟时间的影响因子,通过改变延迟效应对热弹性行为的影响来改变热冲击的作用效果.      

Single quantum dot (QD) imaging of fluid flow near surfaces

We introduce the use of quantum dot (QD) nanoparticles for near-surface velocimetry and provide preliminary data to demonstrate its feasibility. Evanescent wave illumination is used to image the motion of water-soluble (CdSe)ZnS QDs with a core size of 6 nm within a region of order 100 nm of a surface . Results are presented for the two in-plane components of the velocity field.     

Eshelby problem of polygonal inclusions in anisotropic piezoelectric full- and half-planes

This paper presents an exact closed-form solution for the Eshelby problem of polygonal inclusion in anisotropic piezoelectric full- and half-planes. Based on the equivalent body-force concept of eigenstrain, the induced elastic and piezoelectric fields are first expressed in terms of line integral on the boundary of the inclusion with the integrand being the Green's function. Using the recently derived exact closed-form line-source Green's function, the line integral is then carried out analytically, with the final expression involving only elementary functions. The exact closed-form solution is applied to a square-shaped quantum wire within semiconductor GaAs full- and half-planes, with results clearly showing the importance of material orientation and piezoelectric coupling. While the elastic and piezoelectric fields within the square-shaped quantum wire could serve as benchmarks to other numerical methods, the exact closed-form solution should be useful to the analysis of nanoscale quantum-wire structures where large strain and electric fields could be induced by the misfit strain.