Fiber Bragg grating distributed strain sensing: an adaptive simulated annealing algorithm approach

We demonstrate the use of adaptive simulated annealing (ASA) algorithm for determining the strain profile along a fiber Bragg grating (FBG) from its amplitude reflection spectrum. By combining the ASA algorithm and the matrix method for calculating the reflection spectrum of a FBG, the FBG sensor can be used for the distributed strain sensing. Experiments showed that the strain detection accuracy could be in the order of a few microstrains.     

垂直天线阵观测信息反演大气折射率廓线

利用垂直天线阵观测得到的电磁场信息建立目标泛函,从电磁波抛物方程传播模式出发,利用偏微分方程最优控制中的伴随方法研究大气折射率廓线反演问题. 针对反演的不适定性,采用正则化思想对目标泛函进行改造,并根据变分同化思想构建反演迭代格式. 数值模拟试验验证了理论算法的可行性. 由于采用分步Fourier算法求解电磁波抛物方程传播模式和伴随模式过程中产生的固有误差随着传播距离的增加累积增大,反演廓线在传播距离较远时不能收敛于观测廓线. 在这种情况下,引入较好的初猜廓线和背景场可以有效地改进反演结果. 关键词： 大气折射率 电磁波抛物方程 变分伴随 正则化     

用模拟退火法进行纯永磁波荡器磁块组合优化

纯永磁波荡器由多个磁块组成,磁块的剩磁离散性会引起波荡器磁场误差,从而影响储存环工作状态和自发辐射谱质量。在波荡器磁块安装之前,使用模拟退火法对磁块进行组合排序优化,可以使峰值场强误差降低到10-4量级以下,磁场一次积分降低到10-6 T·m量级,二次积分降低到10-6 T·m2量级,优化结果不依赖于初始状态的选择。给出优化的详细过程,提出了根据磁块剩磁快速计算波荡器峰值场强误差和积分场的方法。     

Sequence alignment using simulated annealing

We apply simulated annealing to amino acid sequence alignment, a fundamental problem in bioinformatics, particularly relevant to evolution. Our goal was obtaining results comparable to those reached through dynamic programming algorithms, like the Needleman-Wunsch algorithm, as well as making a connection between physics and bioinformatics through a representative example.     

利用激光诱导荧光来探测远程宽带太赫兹波

远程太赫兹光谱分析在国土安全和环境监测方面的应用有着巨大的潜力.然而由于大气中的水气在太赫兹频率范围内的强吸收,远程宽带太赫兹探测一直以来都是一个挑战.文章介绍了一种通过相干控制非对称电离气体荧光来实现远程宽带探测太赫兹波的全光学技术.由于荧光在大气中的高透过率以及全方位辐射特性,该技术可用于太赫兹波的远程探测,具有最小水气吸收以及不受光信号收集方向限制两个优点.实验上已经获得了距离为10m量级的太赫兹波相干探测.     

Memoryless cooperative graph search based on the simulated annealing algorithm

We have studied the problem of reaching a globally optimal segment for a graph-like environment with a single or a group of autonomous mobile agents. Firstly, two efficient simulated-annealing-like algorithms are given for a single agent to solve the problem in a partially known environment and an unknown environment, respectively. It shows that under both proposed control strategies, the agent will eventually converge to a globally optimal segment with probability 1. Secondly, we use multi-agent searching to simultaneously reduce the computation complexity and accelerate convergence based on the algorithms we have given for a single agent. By exploiting graph partition, a gossip-consensus method based scheme is presented to update the key parameter--radius of the graph, ensuring that the agents spend much less time finding a globally optimal segment.     

Numerical and experimental study on coherent beam combining of fibre amplifiers using simulated annealing algorithm

We present the numerical and experimental study on the coherent beam combining of fibre amplifiers by means of simulated annealing (SA) algorithm. The feasibility is validated by the Monte Carlo simulation of correcting static phase distortion using SA algorithm. The performance of SA algorithm under time-varying phase noise is numerically studied by dynamic simulation. It is revealed that the influence of phase noise on the performance of SA algorithm gets stronger with an increase in amplitude or frequency of phase noise; and the laser array that contains more lasers will be more affected from phase noise. The performance of SA algorithm for coherent beam combining is also compared with a widely used stochastic optimization algorithm, i.e., the stochastic parallel gradient descent (SPGD) algorithm. In a proof-of-concept experiment we demonstrate the coherent beam combining of two 1083~nm fibre amplifiers with a total output power of 12~W and 93% combining efficiency. The contrast of the far-field coherently combined beam profiles is calculated to be as high as 95%.     

Ranking important nodes in complex networks by simulated annealing

In this paper, based on simulated annealing a new method to rank important nodes in complex networks is presented.First, the concept of an importance sequence(IS) to describe the relative importance of nodes in complex networks is defined. Then, a measure used to evaluate the reasonability of an IS is designed. By comparing an IS and the measure of its reasonability to a state of complex networks and the energy of the state, respectively, the method finds the ground state of complex networks by simulated annealing. In other words, the method can construct a most reasonable IS. The results of experiments on real and artificial networks show that this ranking method not only is effective but also can be applied to different kinds of complex networks.     

Non-minimum phase reconstruction from amplitude data in fiber Bragg gratings using an adaptive simulated annealing algorithm

Adaptive simulated annealing algorithm used for phase reconstruction in fiber Bragg grating (FBG) is presented. Theory and numerical simulations show that the non-minimum phase of the FBG can be reconstructed by using this method.     

雷达回波资料反演海洋波导的算法和抗噪能力研究

利用海洋环境中大气波导的参数化模型及电磁波传播的地型抛物方程,建立电磁波传播正问题,获得电磁波传播功率损耗.结合正演模式,通过遗传算法反演出大气波导参数,并对遗传算法参数的设置进行了讨论,对反演系统进行了抗噪能力的分析.发现当误差小于10%时,遗传算法仍能保持较高的反演精度;当误差大于10%时,该算法的精度开始受到显著的影响.研究结果可能会对雷达仪器设计和应用提供参考. 关键词： 波导 电磁波传播方程 遗传算法 反演     

基于退火遗传算法的少数投影CT图像重建

不完全投影重建算法研究是当今图像重建算法中的一个难点问题，近年来，遗传算法在其中有一定的应用，但还存在一些问题。针对遗传算法在优化中的不足(如早熟收敛及易陷入局部最小等)，将模拟退火机制引入到遗传算子中，提出一种新的算法；并通过选择测试函数，建立将该算法应用于不完全投影图像重建的优化模型，进行计算机模拟。通过对从投影角间距为15°的12个不同投影视角方向获取的投影数据进行分析，结果表明，该算法的重建图像具有较高的精度。     

Femtosecond filamentation induced fluorescence technique for atmospheric sensing

Recent progress in filament-induced atmospheric sensing is reviewed.Self-guided propagation of ultrashort laser pulses in air induces laser filamentation.All molecules in the path of a filament can be dissociated into highly excited fragments,resulting in emission of characteristic fluorescence spectra.The fluorescence spectra provide information about the various molecules in the filaments.By using a filament-induced"fingerprinting"fluorescence technique,molecules in the atmosphere can be identified.     

Noise barrier optimization using a simulated annealing algorithm

This paper presents a novel method to design a desired noise barrier using the global optimization of a simulated annealing (SA) algorithm. This method focuses on minimizing the barrier dimensions, which are related to material and construction costs, as well as satisfying the target sound pressure levels at receiver points on the condition of traffic noise. Various examples are presented to evaluate the optimized barrier dimensions according to given traffic noise sources, ground topography, surface conditions, and the influence of different receiver positions. As a result, a robust method is found that can determine optimized barrier configurations and dimensions that yield cost reductions.     

Inversion for atmosphere duct parameters using real radar sea clutter

This paper addresses the problem of estimating the lower atmospheric refractivity (M profile) under nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled using five parameters and the horizontal structure is modeled using five parameters. The refractivity model is implemented with and without a priori constraint on the duct strength as might be derived from soundings or numerical weather-prediction models. An electromagnetic propagation model maps the refractivity structure into a replica field. Replica fields are compared with the observed clutter using a squared-error objective function. A global search for the 10 environmental parameters is performed using genetic algorithms. The inversion algorithm is implemented on the basis of S-band radar sea-clutter data from Wallops Island, Virginia (SPANDAR). Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (ⅰ) by comparing the propagation predicted from the radar-inferred refractivity profiles with that from the helicopter profiles, (ⅱ) by comparing the refractivity parameters from the helicopter soundings with those estimated. This technique could provide near-real-time estimation of ducting effects.     

Optimization of constrained composite absorbers using simulated annealing

Sound reverberation is an important problem in some industrial environments. As indicated by the Occupational Safety and Health Act of 1970, noise is responsible for the psychological and physiological ills of workers. Therefore reduction of reverberation becomes essential. For maintenance and other reasons, the thickness of sound absorbers used for reverberation control may be constrained. Consequently there is interest in minimizing noise using sound absorbers with constrained thickness. Optimization of a composite absorber using a simulated annealing algorithm is presented. Simulated annealing is a stochastic relaxation technique based on analogy with the physical process of annealing metal. The algorithm requires a mathematical model for the acoustical properties of the absorber. Before optimization, the accuracy of the mathematical model was checked against experimental data. A program for optimizing in respect of broad band noise at a specified receiver has been created and run. Results prove that SA optimization provides a quick and efficient approach in designing constrained thickness composite sound absorbers.     

退火温度对纳米氧化铜湿敏性能的影响

湿度传感器在生产和生活中扮演着不容小觑的角色,越来越受到人们的广泛关注.本文利用低温液相法以氢氧化钠、过硫酸铵和铜粉为原料,成功制备出氧化铜纳米结构.运用扫描电子显微镜(SEM)、X-射线衍射仪(XRD)等技术对材料的结构与形貌进行表征,发现可以通过退火温度来调控氧化铜纳米结构的表面形貌,进一步比较研究了不同退火温度下制备的纳米氧化铜的湿敏性能.并将CuO纳米材料涂敷在电极表面制成了湿敏元件.研究结果表明,元件的湿敏特性明显与材料的退火温度密切相关,在500℃退火获得的氧化铜纳米线灵敏度最高,达到1.93×10~5;湿滞最小,几乎为零;感湿频率特性曲线的线性度好.分析认为这主要是由于,退火温度500℃时,氧化铜呈现纳米线状结构,具有更大的表面积,增加了与水分子的接触面积,进而具有更佳的湿敏特性.     

模拟退火算法与遗传算法在光谱椭偏数据处理中的应用比较

分别利用模拟退火算法和遗传算法在MATLAB 6.5中编写了一个数据处理程序,用来处理VASE椭偏仪在光谱范围为500nm～900nm所测得的椭偏数据。根据VASE椭偏仪的光度法原理,对评价函数方程进行了改进,并选择合适的退火参数和遗传参数进行计算,得到的数据处理结果与仪器处理结果基本一致。最后对两种算法在解决该类问题上的优劣进行了比较。     

Design of phase plates for shaping partially coherent beams by simulated annealing

Taking the Gaussian Schell-model beam as a typical example of partially coherent beams, this paper applies the simulated annealing （SA） algorithm to the design of phase plates for shaping partially coherent beams. A flow diagram is presented to illustrate the procedure of phase optimization by the SA algorithm. Numerical examples demonstrate the advantages of the SA algorithm in shaping partially coherent beams. An uniform flat-topped beam profile with maximum reconstruction error RE 〈 1.74% is achieved. A further extension of the approach is discussed.     

Structural optimization and segregation behavior of quaternary alloy nanoparticles based on simulated annealing algorithm

Alloy nanoparticles exhibit higher catalytic activity than monometallic nanoparticles, and their stable structures are of importance to their applications. We employ the simulated annealing algorithm to systematically explore the stable structure and segregation behavior of tetrahexahedral Pt–Pd–Cu–Au quaternary alloy nanoparticles. Three alloy nanoparticles consisting of 443 atoms, 1417 atoms, and 3285 atoms are considered and compared. The preferred positions of atoms in the nanoparticles are analyzed. The simulation results reveal that Cu and Au atoms tend to occupy the surface, Pt atoms preferentially occupy the middle layers, and Pd atoms tend to segregate to the inner layers. Furthermore, Au atoms present stronger surface segregation than Cu ones. This study provides a fundamental understanding on the structural features and segregation phenomena of multi-metallic nanoparticles.