A New Adaptive Near Field Isolation Method Based on Controllable Metamaterial

天线之间的隔离度在许多无线通讯系统中都有要求。在诸如多天线的MIMO 系统、同频双工等等众多实际工程中，天线的隔离度直接决定了工作设备的性能。 而这些天线往往处于彼此的近场，而近场隔离相对于远场有更高的难度。现有的 提高隔离度的方法普遍只能达到30dB到50dB左右的隔离度，并且均是静态方 法。这在实际应用中往往无法满足越来越高的性能和功能要求。 本文提出了一种基于可控超材料和人工智能算法的自适应近场隔离方法。首 先给出了基本的数学模型，并证明该方法的合理性。为了检验理论的正确性，根 据理论模型加工了相应的超材料和天线系统并在暗室中搭建了相应的实验环境、 编写了基于遗传算法的人...The isolation between antennas is required in many wireless communication systems. In many practical projects, such as the MIMO system with multiple antennas, the same frequency duplex and so on, the isolation of the antenna directly determines the performance of the equipment. These are often in the near field antenna near-field isolation of each other, with respect to the far field has a...学位：工程硕士院系专业：物理科学与技术学院_工程硕士(电子与通信工程)学号：3312013115285

An Integrated Testing Technique for Determining the Elastic-plastic Parameters of Metals by Instrumented Spherical Indentation

金属材料作为经典工程材料广泛应用，其弹塑性参数是材料力学性能中的重要指标，是进行结构设计与计算的重要依据。仪器化压入技术由于其微区、微损和原位的特点，已成为微/纳米尺度材料力学性能测试的主要工作方式。本论文的主要目的是基于仪器化球形压入方法发展一种金属材料弹塑性参数的一体化测试技术。具体工作如下： 建立一体化识别弹塑性参数的分析方法。基于孔洞扩张模型和经典Lamé解，针对三种本构关系，推导球形压入问题中压入总功和卸载功的解析表达式。拓展Meyer系数的使用范围，拟合线弹-线硬化本构和线弹-幂硬化本构下Meyer系数与塑性参量之间的关系式。联立压入总功、卸载功和Meyer系数关系式，建立三种本构下的一体化识别弹塑性参数的分析方法。采用数值方法评价本分析方法的准确性和稳定性。 建立金属材料本构的预判方法。研究与变形路径相关的分析参量半压深能量累积率和Meyer系数，发现两者之间存在近似线性减函数关系，不同本构线性拟合的截距差异明显。基于拟合的分界线建立材料本构预判方法，并提出本构预判参数 的概念。 确定测试控制条件。系统论证测试控制条件的影响因素及其程度，提出实用化的压头半径和压入零点确定方法以及压入深度控制方法。结合目前纳米压入和宏观压入两类典型仪器，明确分析方法向测试方法转化的可行性。 评估弹塑性参数识别分析方法及其本构预判方法的可靠性。选取LY12、Al7075、TC4和T2四种典型金属材料，以传统超声法和单轴拉伸法测定的弹塑性参数为名义参考值，对比纳米压入和宏观压入测试结果，证实本文方法能够基于“线弹-硬化”模型预测材料本构类型，提高识别弹塑性参数的准确度。基于识别弹塑性参数预测应力-应变曲线能够较好地吻合单轴拉伸试验结果。 本文系统地研究基于仪器化球形压入方法的金属材料弹塑性参数的一体化测试技术。从分析方法、力学测量和可靠性验证三个层面的依次研究，提升本测试技术的物理内涵和实用性

线弹-幂硬化材料参数的球形压入一体化识别方法

仪器化压入是一种微区、微损的测试技术,制样和操作简便快捷,已成为测定微/纳米尺度力学参数的通用方法。常用的压头可分为锥形(三棱锥和四棱锥)和球形两类。锥形压头识别塑性参数时,由于自相似性,必须使用不同锥角的压头多次测试,过程复杂;球形压头识别弹性模量的Oliver-Pharr方法以接触面积和卸载刚度作为分析参量,精度有限。本课题组姜鹏和张泰华等人发展的塑性参数识别方法(简称加载功方法)基于加载功方程和Meyer关系,实现一次加载识别塑性参数(屈服应力和硬化指数),测试简便。本文在此基础上发展基于球形压入测试的弹性参数识别方法,从而实现弹塑性参数一体化识别。经过加载功方法的误差分析认为:(1)压..

GA-ACO优化BP神经网络在行星齿轮箱故障诊断中的应用

针对目前利用优化算法改进的BP神经网络算法对行星齿轮箱进行故障诊断过程中存在的故障识别率低、收敛速度慢和参数选择困难等问题，提出了一种用GA-ACO算法对神经网络参数进行优化的算法。给出GA-ACO-BP算法的基本原理和主要步骤，并将此方法应用到行星齿轮箱的故障诊断中。比较了ACO-BP神经网络算法和GA-ACO-BP算法的性能。结果表明，ACO优化BP神经网络算法对行星齿轮箱的故障诊断收敛速度慢且识别精度不高，而GA-ACO-BP算法能够对行星齿轮箱故障进行准确、快速的诊断和识别

Response spectra for transient pore-pressure in a sandy seabed under random waves: Frequency-filtering effect

The real state of ocean waves is random in nature with various monochromatic components. Transient pore pressures in a sandy seabed under the action of the random-waves with JONSWAP spectrum and the regular -waves were physically modeled, respectively. The surface elevations and the corresponding transient pore pressures in the fine-sand were measured simultaneously in a wave flume. The frequency-filtering phenomenon was observed by Fourier analysis for random-wave induced pore pressure responses. In the Fourier energy spectra, both a primary-peak (high-frequency) and a secondary-peak (low-frequency) were identified within the relatively shallow soil layer. But the primary-peak kept declining rapidly, meanwhile the secondary-peak attenuated much more slowly with increasing soil depth, which can eventually lead to a shift between the high-frequency peak and the low-frequency one. As a consequence, the upgraded primary-peak frequencies of the dual-peaked spectra at the deeper soil layer would become smaller than the original significant frequencies, indicating that the pore pressure induced by long-wave components is of vital significance there. Furthermore, a filtering-depth parameter is introduced to characterize the frequency-filtering effect. Given the pore pressure at a certain soil depth, the quantitative relationship between the primary-peak and the secondary-peak can be pre-dicted for an arbitrary soil depth

Intelligent Supplying System of Self-calcinating Electrobath

介绍基于铝电解过程中热平衡和物料平衡原理而设计的一种自动下料系统。这个系统首先在现场总线控制系统上建立一个开放的平台,然后在平台之上建立专家系统,实现自动下料

Effect of childhood trauma on depressive mood: a regulated mediation model

目的 为明确童年期创伤经历对抑郁情绪的作用机制，本研究构建了一个有调节的中介模型，考察在新兵中愤怒表达在二者关系中的中介作用以及压力的调节作用。方法 418名男性新兵为被试，采用问卷法对童年期创伤经历、压力、愤怒表达及抑郁情绪进行调查。结果 (1)在控制年龄、学历、家庭所在地、是否独生和父母关系后，童年创伤对抑郁情绪具有显著的正向预测作用；(2)愤怒对内表达、愤怒对外表达和控制愤怒对外表达能够在童年创伤经历与抑郁情绪的关系中起中介作用；(3)童年创伤经历对抑郁情绪的直接预测作用受到压力的调节。结论 引导新兵合理地表达愤怒情绪，对其抑郁情绪及其心理社会适应服务具有意义。</p

Identification of the elastic-plastic constitutive model for measuring mechanical properties of metals by instrumented spherical indentation test

Several methods for determination of elastic-plastic parameters by instrumented spherical indentation tests have been presented in the past few years. Each method was established according to a specific constitutive model. Identification of the constitutive models of new materials has become an indispensable step in order to choose an appropriate indentation method to extract the elastic-plastic parameters. In the present work, the half depth energy accumulation rate and Meyer's index were related to the elastic-plastic constitutive models via qualitative and numerical analyses. A method for identification of the elastic-plastic constitutive models by instrumented spherical indentation test was proposed

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This paper aims to obtain an analytical expression for the ratio of unloading work of indentation (W-u) to total loading work of indentation (W-t) (work recovery ratio of indentation) in instrumented spherical indentation. The expanding cavity model and Lame solution are used. Three typical stress-strain relations (elastic-perfectly plastic, linear hardening, and power-law hardening) are analyzed. The results of finite-element method coincide with the expressions. The expressions show that the work recovery ratio of indentation is just related to plastic parameters. Furthermore, elastic work (W-e) are obtained, and it is proved that W-e should be distinguished from W-u in spherical indentation