Voigt–Reuss topology optimization for structures with linear elastic material behaviours

The desired results of variable topology material layout computations are stable and discrete material distributions that optimize the performance of structural systems. To achieve such material layout designs a continuous topology design framework based on hybrid combinations of classical Reuss (compliant) and Voigt (stiff) mixing rules is investigated. To avoid checkerboarding instabilities, the continuous topology optimization formulation is coupled with a novel spatial filtering procedure. The issue of obtaining globally optimal discrete layout designs with the proposed formulation is investigated using a continuation method which gradually transitions from the stiff Voigt formulation to the compliant Reuss formulation. The very good performance of the proposed methods is demonstrated on four structural topology design optimization problems from the literature. © 1997 John Wiley & sons, Ltd.     

挠性结构主动减振中传感器和激振器的优化布置

本文提出了从有效衰减振动能量的角度，通过最小化Ｌｙａｐｕｎｏｖ第二方法中的优化性能指标，对挠性结构振动的主动控制进行优化的方法。研究了在以位移传感器或速度传感器作为检测元件进行部分状态变量反馈的约束条件下，传感器、激振器的最优位置以及最优反馈增益的确定，讨论了在包括截尾残余模态的情况下系统的稳定性。本文还对在两邻边固定、另两邻边自由的边界条件下矩形薄板振动的主动控制进行了优化计算和数字仿真。结果表明，优化的控制系统能够有效地衰减结构的振动。本方法具有明显的物理意义和较高的计算速度，并且通过选取不同的权系数，能够协调控制能量和振动的衰减效果，从而得到合理的位置和增益。     

Determination of the optimal regularization parameters in hyperspectral tomography

In a previous paper, we described a novel technique to exploit hyperspectral absorption spectroscopy to retrieve tomographic imaging of temperature and species concentration simultaneously. This technique casts the tomographic inversion into a nonlinear minimization problem with regularizations. Here a simple and effective method is developed to determine the optimal regularization parameters in the nonlinear optimization problem. This method, combined with the minimization method described previously, provides a robust algorithm for hyperspectral tomography. This method takes advantage of an inherent feature of absorption and is therefore expected to be useful for other sensing techniques based on absorption spectroscopy.     

Infrared photoluminescence of composite films containing quasi-isolated multiwalled carbon nanotubes and carbon nanoshells

Films of small irregular-shaped aggregates composed by several layers of turbostratic graphite encapsulating iron nanoparticles, like carbon nanoshells, and quasi-isolated multi-walled carbon nanotubes (MWCNTs), were synthesized by the chemical vapor deposition method on glass substrates. Quasi-isolated MWCNTs were found emerging in different directions on the agglomerates composed of carbon nanoshells. The morphological properties of the films were characterized using scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy, whereas their optical properties were investigated using optical absorption and photoluminescence (PL) spectroscopy. The studies show a high-intensity PL signal in the infrared at room temperature. This PL signal shows several peaks, which cannot be explained by a blackbody emission. However, the overall PL signal could be a combination of the black emission and electronic transitions. Furthermore, the observed infrared PL emission could be ideal for potential applications such as in gas sensors, infrared detectors and so on.     

基于统计能量理论的飞行器壁板高频声振疲劳寿命预报及参数设计

为研究高速飞行器受高频脉动噪声载荷激励下的结构声疲劳问题,讨论了基于应力谱的频域疲劳损伤计算方法。该文提出了一种基于统计能量理论（SEA）的结构高频随机振动疲劳寿命计算方法。在该方法中,首先采用SEA计算子系统的均方应力,然后引入模态间隔的Rayleigh和Poisson分布假设,生成飞行器壁板的随机模态空间并构建危险点的应力谱曲线,进而结合频域疲劳寿命分析方法,采用Monte Carlo模拟求解壁板的疲劳寿命。验证分析表明,基于SEA和Monte Carlo模拟的结构高频声振疲劳寿命分析方法计算精度高,是高速飞行器强度设计的一种可靠方法。在此基础上,考察了壁板厚度和结构阻尼参数对壁板声振疲劳寿命的影响,计算结果表明,当输入声压谱一定时,存在局部最优解,采用该局部最优解作为壁板的设计参数可明显降低结构质量。     

Model-based optimal design of polymer-coated chemical sensors

A model-based methodology for optimal design of polymer-coated chemical sensors is developed and is illustrated for the example of infrared evanescent field chemical sensors. The methodology is based on rigorous and computationally efficient modeling of combined fluid mechanics and mass transfer, including transport of multiple analytes. A simple algebraic equation for the optimal size of the sensor flow cell is developed to guide sensor design and validated by extensive CFD simulations. Based upon these calculations, optimized geometries of the sensor flow cell are proposed to further improve the response time of chemical sensors.     

气体中痕量水蒸气测量技术进展

气体中水蒸气含量测量在工业生产和科研领域发挥至关重要的作用。随着许多工业生产和科研领域对气体水分含量更加严格的测试要求,对于气体中水蒸气含量测量灵敏度的要求也越来越高。目前测量nmol/mol痕量水分的仪器方法有可调谐二极管激光吸收光谱法、光腔衰荡光谱法、大气压离子质谱仪法;达到这个痕量水平的传感器类测量技术有石英晶体微天平法、冷镜露点法、阻容法、电解法。针对这些测量方法的优缺点以及今后的发展趋势进行了论述分析,通过克服测量过程中的干扰因素,可在一定的程度上提高痕量水含量的测量准确性,对促进痕量水含量准确测量技术的发展有所裨益。     

Vibronic properties of organic semiconductors based on zirconium monophthalocyanine

Vibronic states of organic semiconductors based on zirconium monophthalocyanine molecules have been studied. Vibrational and rotational transitions in the organic semiconductor containing zirconium atoms are precisely described based on data of infrared absorption and Raman spectroscopy.     

过程激励的定性模拟方法及原型系统

为了给企业选择激励措施时提供一种虚拟实验工具,基于物理系统定性模拟及其它多种思想,设计了过程激励的定性模拟方法,开发了原型系统.其中,借鉴模糊数学和QSIM（Qualitative Simulation）算法的思路表述定性状态变量;利用改进的因果关系图表述激励措施与人群激励效果之间、以及与激励成本之间的定性关系;采用IF-THEN方式设计了状态变量的转换规则;借鉴纳什均衡的思想,提出激励-满意均衡概念,用于过滤各模拟阶段的不合理的转换;链接前述各方法,设计了模拟步骤;为实现上述方法,用VB 6.0和Matlab 6.10开发了原型系统.实验表明,通过本文的方法,系统所得的结果是符合常理的.     

Product platform design through clustering analysis and information theoretical approach

An effectively designed product platform is vital to the final product family derived from it. A product platform design consists of platform configuration to decide which variables to make common across the product family and to determining the optimal values for platform and scaling variables for all product variants. Many existing product family design methods assume a given platform configuration, i.e. the platform variables are specified a priori by designers. However, selecting the right combination of common and scaling variables is not trivial. Most approaches are single-platform methods, in which design variables are either shared across all product variants or not at all. While in multiple-platform design, platform variables can have special value with regard to a subset of product variants within the product family, offering opportunities for superior overall design. This paper proposes a quantitative method for scale-based multiple-platform design using clustering analysis and Shannon's Entropy theory. Optimization methods are used to design the product family by holding the values of platform variables constant and to find the best values of the scaling variables. An information theoretical approach is used to help select platform variables based on the clustering analysis of individually designed products. Validity analysis is performed to determine the optimal settings for platform variables. Local clustering is further performed on each platform variable, to establish subsets of variants such that variants within a subset are more similar to each other than they are to variants in other subsets and a common value is used to represent the various values of variants in each subset. A case study is used to illustrate the process of the proposed method, and the design solutions are compared with that found by other methods given in previous literature. The comparison results verified that the multiple-platform design can lead to superior solutions of product family.     

Gradient projection for reliability-based design optimization using evidence theory

Uncertainty quantification and risk assessment in the optimal design of structural systems has always been a critical consideration for engineers. When new technologies are developed or implemented and budgets are limited for full-scale testing, the result is insufficient datasets for construction of probability distributions. Making assumptions about these probability distributions can potentially introduce more uncertainty to the system than it quantifies. Evidence theory represents a method to handle epistemic uncertainty that represents a lack of knowledge or information in the numerical optimization process. Therefore, it is a natural tool to use for uncertainty quantification and risk assessment especially in the optimization design cycle for future aerospace structures where new technologies are being applied. For evidence theory to be recognized as a useful tool, it must be efficiently applied in a robust design optimization scheme. This article demonstrates a new method for projecting the reliability gradient, based on the measures of belief and plausibility, without gathering any excess information other than what is required to determine these measures. This represents a huge saving in computational time over other methods available in the current literature. The technique developed in this article is demonstrated with three optimization examples.     

基于Herriott吸收池的固定源二氧化碳浓度测量研究

准确的碳排放计量是实现“碳峰化、碳中和”目标的重要一步。在所有碳排放源中,固定排放源排放的CO2是温室效应的主要因素。因此,精确测量固定排放源CO2的浓度尤为重要。基于近红外分子吸收光谱原理并结合多次反射直接吸收光谱技术,利用35% CO2/N;2混合物,建立了精确测量CO2浓度的方法,测量了293K和0,4.1,8.1,13.3kPa下,CO2在6359.97cm-1的(30012)←(00001)R16e和6361.25cm-1的(30012)←(00001)R18e跃迁谱线,计算了R18e的谱线强度,通过比较35% CO2/N2混合物和其它CO2/N;2混合物的吸收面积,可以得到15%,10%,5%的CO2/N;2混合物的浓度。结果表明所建立的理论方法和实验结果能够较好地表征待测气体的浓度,测量不确定度与基于天平的称重法相当。     

进化论自适应滤波算法及降噪特性研究

基于生物进化论策略的自适应滤波算法，利用其有性繁殖和无性繁殖的随机搜索能力实现全局最优搜索，可克服最小均方法（Least Mean Square，简称：LMS）对于多峰特性问题有可能收敛于某一局部最小值，无法实现全局最优的缺点。提出峰值系数指标PR（Peak Ratio）概念解决进化论自适应滤波器的性能评估问题，提出收敛速度CS（Converge Speed）指标和峰值系数指标PR高度的方法解决最优滤波参数的选取问题，并列进化论自适应滤波器的降噪进行模拟仿真，讨论了滤波长度和进化系数对进化论自适应算法消噪效果的影响及最优滤波参数。     

Optimal experimental design in stochastic structural dynamics

This paper provides a methodology for optimal prediction of the response of randomly vibrating structures using information from a limited number of measurements. The objective is to optimize the locations of sensors for the purpose of making the most accurate predictions of the response at unmeasured locations in structural systems. The kriging method is used to find the response predictions and the corresponding mean-square errors at unmeasured locations. The mean-square errors in the predictions depend on the locations of sensors and the correlation characteristics of the response evaluated from the model of dynamics and the characteristics of the excitation. The response predictions depend also on the information contained in measurements. The optimal sensor locations are selected to minimize the total mean-square error of the response predictions at unmeasured points. This leads to a complicated non-convex optimization problem in which multiple local and global optima may exist. A hybrid optimization method based on evolution strategies is used to determine a global minimum. The optimal experimental design method presented in the paper is illustrated by designing the optimal sensor locations for an elastic beam and a plate subjected to a class of random stationary loads.     

Fabrication and Characterization of Single-Layer Textile-Based Flexible Pressure Sensors for Smart Wearable Electronics Applications

Textile-based sensors have been widely studied for wearable monitoring. The sensor systems demand a large sensing area, flexibility, and scalable fabrication method. Herein, single-layer piezoresistive sensors are developed by a machine stitching technique using metallic and graphene nanoplatelets-coated conductive threads and fabrics. The pressure-sensing mechanism is based on measuring the electrical resistance due to the change in the contact area between the conductive thread and fabric as pressure on the sensor varies. The single-layer sensor design provides flexibility and overcomes the physical drift of the sensor during human activities, which enhances wearability and performance. The coated textiles are characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. Physical and electromechanical tests are performed on the sensors to evaluate their wearability and sensing performance. The sensors exhibit a wide working range of up to 100 kPa and good sensitivity with excellent durability against repeated mechanical deformations. The application potential of the sensors in real-time monitoring is demonstrated by embedding them into clothing as a wearable device. Moreover, the effectiveness of the sensors is tested for posture correction. This article suggests a novel technique to fabricate durable, flexible, and highly efficient pressure sensors for smart wearable applications.     

振动主动控制中传感器与作动器参数的优化设计

本文分析了文献[5]中方法的不足,提出了梁式结构振动主动控制中同时优化系统极点和传感器/作动器位置的联合优化设计法,指出传感器/作动器最优位置不仅与受控结构的模态频率和振型有关,还与系统的极点位置有关.对于最低阶模态频率较低(小于1.0 rad/s)的受控结构的主动控制系统不宜采用加速度传感器.     

路标定位中的优化选择策略

基于合作路标的三角定位是自主式移动机器人的主要定位方法。路标的优化选择是提高定位算法精度的关键。本文在给出该算法原理的基础上,通过理论分析和实验证明了路标优化选择对提高定位算法精度的作用,并介绍了路标优化选择的准则。     

On approximate stochastic control in genetic regulatory networks

The control of probabilistic Boolean networks as a model of genetic regulatory networks is formulated as an optimal stochastic control problem and has been solved using dynamic programming; however, the proposed methods fail when the number of genes in the network goes beyond a small number. There are two dimensionality problems. First, the complexity of optimal stochastic control exponentially increases with the number of genes. Second, the complexity of estimating the probability distributions specifying the model increases exponentially with the number of genes. We propose an approximate stochastic control method based on reinforcement learning that mitigates the curses of dimensionality and provides polynomial time complexity. Using a simulator, the proposed method eliminates the complexity of estimating the probability distributions and, because the method is a model-free method, it eliminates the impediment of model estimation. The method can be applied on networks for which dynamic programming cannot be used owing to computational limitations. Experimental results demonstrate that the performance of the method is close to optimal stochastic control.     

Direct and chemically-mediated absorption spectroscopy usingoptical fiber instrumentation

This paper shows various applications of optical fiber sensors to absorption spectroscopy. Sensors for the monitoring of chromium in sewage water and for the colorimetry of gasoline samples are presented together with sensors for radiation dosimetry in radiotherapy and for lighting control in museum environments. In all these sensors, a combination of broadband and multi-band spectral measurements are collected using the same custom instrumentation unit consisting of LED light sources and an optical fiber microspectrometer. Extensions of the unit to implement other sensors making use of visible spectral range are discussed. The custom instrumentation implemented to address these sensors is their key unifying feature. It opens the possibility of addressing other sensors making use of absorption-based optrodes which present an analyte-modulated absorption spectrum in the visible spectral range     

Robustness of asymptotic accelerated life test plans to small‐sample settings

Much of the statistical literature on optimal test planning for accelerated life testing utilize asymptotic methods to derive optimal test plans. While sufficient effort is made to assess the robustness of these test plans to the choice of design parameters and distribution assumptions, there is very little literature on the performance of asymptotic test plans relative to small samples (on the order of 10‐15 samples). An alternative concern is that the asymptotic test plans may not necessarily be the true “optimal” test plan for a given sample size. The purpose of this research is to present exact or “near‐exact” methods for developing test plans and compare the performance of these test plans with corresponding asymptotic test plans in small‐sample settings. The optimal location of design points and sample allocation is determined using each method for lognormal and Weibull lifetime distributions with both complete and Type 1 right‐censored data under two selected acceleration factor models. The investigations reveal that asymptotic test plans tend to corroborate quite well with exact test plans and thus are suitably robust to small‐sample settings in terms of optimal variance.