The Squeezing Effect in a Mesoscopic RLC Circuit

Using the path integral method we derive quantum wave function and quantum fluctuations of charge andcurrent in the mesoscopic RLC circuit. We find that the quantum fluctuation of charge decreases with time, oppositely,the quantum fluctuation of current increases with time monotonously. Therefore there is a squeezing effect in the circuit.If some more charge devices are used in the mesoscopic-damped circuit, the quantum noise can be reduced. We also findthat uncertainty relation of charge and current periodically varies with the period π/2 in the under-damped case.

Quantum Effect in the Mesoscopic RLC Circuits with a Source

The research work on the quantum effects in mesoscopic circuits has undergone a rapid development recently, however the whole quantum theory of the mesoscopic circuits should consider the discreteness of the electric charge. In this paper, based on the fundamental fact that the electric charge takes discrete values, the finite-difference Schrodinger equation of the mesoscopic RLC circuit with a source is achieved. With a unitary transformation, the Schrodinger equation becomes the standard Mathieu equation, then the energy spectrum and the wave functions of the system are obtained. Using the WKBJ method, the average of durrents and square of the current are calculated. The results show the existence of the current fluctuation, which causes noise in the circuits. This paper is an application of the whole quantum mesoscopic circuits theory to the fundamental circuits, and the results will shed light on the design of the miniation circuits, especially on the purpose of reducing quantum noise coherent controlling of the mesoscopic quantum states.

Mesoscopic modelling of UHPCC material under dynamic tensile loadings

This paper presents a new 3D mesoscopic model of ultra-high performance cement-based composite(UHPCC)to investigate its dynamic tensile behavior.In this model,the UHPCC is regarded as a two-phase material composed of cementitious matrix and randomly distributed fibers.The model is established using the commercial software LS-DYNA and involves generating the randomly distributed fiber elements with considerations of diameter,length,orientation and volume fraction,and then fully constraining them with the matrix.In particular,to capture the slipping effect between fibers and matrix that has a strong influence on the dynamic tensile behavior,the fibers are modelled by a fictitious material represented by the load-slip relation.The strain-rate effect of slipping force neglected in most of previous studies is considered by calibrating constitutive parameters of the fictitious material under different strain-rates based on the single fiber pullout tests.Finally,the 3D mesoscopic model is validated against three sets of tension-dominated experiments covered a wide range of loading intensity.Numerical predictions demonstrate that strain-rate effect of slipping force must be considered,and the neglect of it may lead to a great underestimation of the dynamic tensile strength of UHPCC material and would unavoidably underestimate the blast resistance of UHPCC components.

Quantum Effects of Mesoscopic Inductance and Capacity Coupling Circuits

Using the quantum theory for a mesoscopic circuit based on the discretenes of electric charges, the finitedifference Schrodinger equation of the non-dlssipative mesoscopic inductance and capacity coupling circuit is achieved. The Coulomb blockade effect, which is caused by the discreteness of electric charges, is studied. Appropriately choose the components in the circuits, the finlte-dlfference Schrodinger equation can be divided into two Mathieu equations in representation.＂ With the WKBJ method, the currents quantum fluctuations in the ground states of the two circuits are calculated. The results show that the currents quantum zero-point fluctuations of the two circuits are exist and correlated.

Quantum Effect in Mesoscopic Open Electron Resonator

The open electron resonator is a mesoscopic device that has attracted considerable attention due to its remarkable behavior： conductance oscillations. In this paper, using an improved quantum theory to mesoscopic circuits developed recently by Li and Chen, the mesoscopic electron resonator is quantized based on the fundamental fact that the electric charge takes discrete value. With presentation transformation and unitary transformation, the SchrSdinger equation becomes an standard Mathieu equation. Then, the detailed energy spectrum and wave functions in the system axe obtained, which will be helpful to the observation of other characters of electron resonator. The average of currents and square of the current are calculated, the results show the existence of the current fluctuation, which causes the noise in the circuits, the influence of inductance to the noise is discussed. With the results achieved, the stability characters of mesoscopic electron resonator are studied firstly, these works would be benefit to the design and control of integrate circuit.

The Squeezing Effect in a Mesoscopic RLC Circuit

Using the path integral method we derive quantum wave function and quantum fluctuations of charge andcurrent in the mesoscopic RLC circuit. We find that the quantum fluctuation of charge decreases with time, oppositely,the quantum fluctuation of current increases with time monotonously. Therefore there is a squeezing effect in the circuit.If some more charge devices are used in the mesoscopic-damped circuit, the quantum noise can be reduced. We also findthat uncertainty relation of charge and current periodically varies with the period π/2 in the under-damped case.

Quantum Effect in a Diode Included Nonlinear Inductance-Capacitance Mesoscopic Circuit

The mesoscopic nonlinear inductance-capacitance circuit is a typical anharmonie oscillator, due to diodes included in the circuit. In this paper, using the advanced quantum theory of mesoseopie circuits, which based on the fundamental fact that the electric charge takes discrete value, the diode included mesoscopic circuit is firstly studied. Schrodinger equation of the system is a four-order difference equation in p rep asentation. Using the extended perturbative method, the detail energy spectrum and wave functions axe obtained and verified, as an application of the results, the current quantum fluctuation in the ground state is calculated. Diode is a basis component in a circuit, its quantization would popularize the quantum theory of mesoscopie circuits. The methods to solve the high order difference equation are helpful to the application of mesoscopic quantum theory.

Quantum Fluctuation of a Mesoscopic Inductance Coupling Circuit at Finite Temperature

We study the quantization of mesoscopic inductance coupling circuit and discuss its time evolution. Bymeans of the thermal field dynamics theory we study the quantum fluctuation of the system at finite temperature.

Persistent Current in Two Connected Mesoscopic Rings with Reservoirs

The persistent current and transmission of two connected Aharonov-Bohm rings coupled to external leads are solved analytically. The conditions on which we may observe persistent current, zero or perfect transmission as well as Fano resonance are studied.

骨料含量和试件尺寸对混凝土单轴受压细观性能影响

为了研究粗骨料含量对混凝土单轴受压性能及尺寸效应的影响,通过编写Python脚本在Abaqus中建立二维混凝土随机骨料模型.该模型涵盖了骨料、砂浆和界面过渡区三相混凝土细观结构,使得模型更加接近真实混凝土结构;通过设置骨料含量和模型尺寸这两个变量,研究了其对模型力学性能的影响.研究结果表明,在同一试件尺寸下,随着骨料含量的增加,混凝土损伤破坏渐趋严重,弹性模量略有增大,抗压强度呈下降趋势;相同骨料含量下混凝土的尺寸效应明显,随着试件尺寸的增加,细观非均质性增强,导致混凝土抗压强度降低,损伤破坏现象更趋明显.分析尺寸效应对模型的影响规律,为实际情况下缩尺模型的性能预测提供参考.

考虑尺寸效应的再生混凝土受压破坏细观模拟研究

再生粗骨料取代率、粗骨料粒径及截面尺寸对再生混凝土单轴压缩破坏行为产生影响。文章采用细观尺度数值模拟方法,建立了再生混凝土二维细观模型,模拟分析了再生混凝土单轴压缩破坏的应力-应变曲线、损伤拓展以及破坏的全过程。结果表明:静态加载下,再生混凝土的损伤由内向外拓展,先出现在最薄弱的界面过渡区,再发展到砂浆基质;截面尺寸、粗骨料粒径和再生粗骨料取代率的改变会影响到再生混凝土的破坏模式和力学性能;再生混凝土存在明显的尺寸效应,不同截面尺寸下,再生粗骨料的粒径和取代率的增大都会在一定程度上削弱尺寸效应行为,而当再生粗骨料取代率为100%时,尺寸效应得到有效抑制。

准静态侵入颗粒介质的底边界效应仿真分析

论文基于球形离散元方法研究颗粒介质的底边界效应,仿真刚体圆柱准静态侵入有限厚度颗粒介质直至底边界的过程,探究侵入物所受阻力与侵入深度间关系.结果表明,圆柱准静态侵入颗粒层至池底的阻力-深度曲线,前段呈类静水压力线性,接近底边界的后段呈类指数增长形式;在距底数个粒径范围内阻力存在波动,波长近似颗粒直径.与圆柱底固连的倒锥形固化区颗粒存在动态更新,侵入接近底边界时固化区瓦解,局部颗粒阻塞与疏通决定阻力增长趋势;圆柱底面以下的颗粒力链在接近底边界时转化为圆柱底与颗粒池底之间的“底-底”力链,力链受挤压后平均颗粒数的递减很好地解释了阻力振荡的波动性.

升温路径对花岗岩超声波传播特性影响的试验研究

地热能开发以及核废料处置等深部高温岩体工程中,岩石破裂行为和损伤特征受升温路径影响显著.超声波传播速度和振幅等参数可以综合反映岩体破裂和损伤状态,具有重要的工程价值.为探究升温路径对岩石超声波传播特性的影响,开展了600℃下不同加热速率和恒温时间热处理后花岗岩的超声波透射和SEM扫描试验.研究结果表明:岩石超声波波速、幅值和频谱振幅等特征参数在不同升温路径下有较大差异.岩石超声波传播特性与加热速率具有明显的阶段依赖性,当加热速率低于9℃/min时,岩石超声波传播特征参数随加热速率增加显著降低;当加热速率高于9℃/min时,其降低幅度减缓.恒温时间对岩石超声波特性的影响存在阈值,当恒温时间小于3 h时,超声波传播特征参数随着恒温时间增加而减小,当恒温时间大于3 h时,其变化不明显.不同升温路径下岩石热裂纹扩展模式的差异是影响热处理岩石超声波传播特性的主要原因.超声波传播特征参数中首波幅值对升温路径变化的敏感性最高,适宜作为评价花岗岩体破裂行为和损伤程度的最优指标参数.研究结果对高温岩体工程损伤程度和稳定性评价具有一定的指导意义.

基于CT的干湿循环-动荷载贯序耦合作用下压实粉质黏土细观结构特征研究

为进一步揭示多因素耦合作用下服役期路基土体性能劣化机制,在前期工作基础上,采用CT扫描技术对经历不同干湿循环、动荷载条件的压实粉质黏土试样细观结构特征开展研究,分析干湿循环-动荷载贯序耦合作用对试样孔隙三维空间分布、孔隙体积统计分布、图像灰度统计指标的影响规律,分析试样宏观性能与细观结构特征的关系。试验结果表明:干湿循环作用会导致试样产生更多大孔隙和贯通裂隙,动荷载作用可以使因干湿循环产生的部分孔隙或裂隙闭合;随着干湿循环和动荷载的贯序耦合作用,试样中的小孔隙数量呈增多趋势;干湿循环作用均会导致孔隙总体积增加,动荷载作用则会使孔隙总体积减小;试样细观结构特征参数可以用于解释试样宏观性能演化规律。

Squeezing effect in the coupled mesoscopic electric circuits

The rapid development of nanotechnology and nanoelectronics has made it possible to minimize the integrated circuits and components towards atomic-scale dimensions. Clearly, when the transport dimension reaches a characteristic dimension, namely the

Quantum pump effect in a four-terminal mesoscopic structure

Quantum pump effect in a four-terminal mesoscopic structure constructed from a homogeneous two- dimensional electron gas is investigated. Oscillating electric potentials are applied to the two opposite terminals of the four-terminal mesoscopic structure. In both the remaining two opposite terminals and in the central region there are constant potentials that do not change with time. The oscillating potentials change slowly in comparison with all of the internal time scales of the structure and the amplitude of the oscillating potentials is small in comparison with the Fermi energy. The current of each lead and the transmission coefficients from one lead to another are calculated by using the non-equilibrium Green＇s function approach under the adiabatic approximation. In the remaining two opposite terminals of the four-terminal structure, the quantum pump effect can produce an electric current whose magnitude and direction depends on the Fermi energy. The pumped currents are ascribed to the asymmetry of transmission coefficients with respect to the Fermi energy.

甘肃北山地区深部花岗岩的热开裂试验研究

通过岛津SEM全数字液压高温疲劳试验系统,实时观察不同温度下北山花岗岩的热开裂过程,获得北山花岗岩的热开裂临界温度为68℃～88℃。在较低温度时,北山花岗岩热开裂以沿颗粒热开裂为主;在较高温度时,热开裂以穿颗粒热开裂及沿颗粒穿颗粒混合热开裂为主。热开裂不仅受到矿物颗粒的热膨胀性质不匹配及热膨胀各向异性的影响,还受到矿物颗粒的物理、力学、热学性质及矿物颗粒形状结构的影响。而花岗岩内流体包裹体也可能是影响北山花岗岩热开裂的一种重要因素,这是种新的影响机制。在微细观层次对热开裂模式进行分类,并由热开裂的分形模型定量解释沿颗粒和穿颗粒热开裂等发生的难易程度。当温度升高超过250℃时,北山花岗岩有可能存在热熔效应,这导致热开裂裂纹数有减少趋势,并且温度与其对应的热裂纹数量的统计关系符合Gauss曲线关系。

岩石材料微、细、宏观断裂机理尺度效应的分形研究

基于同一现场不同尺度的岩石材料,从大量三轴MTS试验岩石断口边痕、试样切割面或磨光面的节理痕迹和现场断裂迹线3个尺度层次,进行了岩石材料微、细、宏观断裂机理尺度效应的分形研究。提出圆与正方形相耦合的分形维数算法,探讨了其优越性并应用于岩石断裂的分形特征研究,得到岩石材料的微、细、宏观断裂机理存在无标度区域。在无标度区0.002mm～4000mm内,岩石断裂构造的分布规律具有自相似性,是岩石材料的微、细、宏观断裂机理内在联系的外在反映,为跨越尺度界限研究岩石节理裂隙的破坏机理提供了可行途径。

弹体侵彻混凝土靶体的尺寸效应分析

由于混凝土靶体抗刚性弹侵彻实验大多基于缩比弹体展开,侵彻深度相似律是否成立显得尤为重要。在侵彻相似模型基础上,综合分析已有侵彻实验数据及经验公式,发现侵彻深度在通常情况下存在尺寸效应,且无量纲侵彻深度随弹体尺寸变大而增大。但如果模型以及原型实验中弹体与混凝土靶体(包括粗骨料)严格等比例设计,侵彻深度相似律是成立的。不变的骨料特征(粗骨料未随弹体尺寸缩放)是引起侵彻实验以及侵彻经验公式中尺寸效应的主要原因。为研究由粗骨料引起的侵彻尺寸效应,开发了混凝土二维细观有限元建模程序,细观数值实验成功地反映出了侵彻尺寸效应,考虑模拟尺寸效应后的侵彻公式能较好地预测不同尺寸侵彻实验。

静动荷载下桩网结构路基土拱效应细观分析

研究目的:为研究列车荷载下桩网结构路基中土拱效应的形成机理和受力特性,本文通过建立桩网结构路基简化离散元模型,利用PFC^(3D)软件对土拱效应机理进行细观研究,分析颗粒间的接触力链、颗粒的横向及竖向位移以及路基中的颗粒应力竖向分布。研究结论:(1)动荷载作用后,桩间土应力增加,土拱效应被削弱;(2)动荷载作用下,路基中会形成动力土拱,大部分动力会沿动力拱传递至桩顶上方;(3)等沉面的形成与位移拱有关,位移拱范围内桩顶上方颗粒挤入桩间土区域,从而导致位移拱范围外桩顶颗粒竖向位移增大,而桩间土颗粒竖向位移减小;(4)路基中设置土工格栅会降低土拱高度,削弱应力拱内多个虚拟土拱的作用,但比土拱更能提高桩土应力比;(5)本研究结果可为铁路路基结构工作机理分析提供思路和方法。