Empirical pseudopotential band structure parameters of 4H-SiC using a genetic algorithm fitting routine

In this paper, the viability of using a genetic algorithm to find band structure parameters for empirical pseudopotential method (EPM) calculations is demonstrated by applying a genetic algorithm to find the EPM parameters for 4H-SiC. The form of the pseudopotential for 4H-SiC and the 19 form factors found by the genetic algorithm to fit the band structure to experimentally measured indirect energy gap and direct optical gaps are given. In addition, the effective masses for the conduction band minimum are extracted from the calculated band structure. It is shown that the genetic algorithm provides an effective, automated way to find parameters that give reasonably good fits to both the band gaps and the effective masses simultaneously.     

Design optimization of porous fibrous material for maximizing absorption of sounds under set frequency bands

In this paper, a methodology is proposed for designing porous fibrous material with optimal sound absorption under set frequency bands. The material is assumed to have a rigid frame and a hexagonal arrangement of fibers, and the analytical model derived by Johnson, Champoux and Allard (“JCA model”) is used to investigate the influences of the micro-structural parameters (fiber radius r and gap w) on sound absorption performance, and the macro-acoustic parameters used in JCA model is determined via finite element analysis for the hexagonal micro-structure. Moreover, a mathematical model is constructed to obtain the optimized micro-structure design, with fiber radius and gap as design parameters and average absorption performance of the porous fibrous material under set frequency band as target. Utilizing the constructed optimization model, the microstructure parameters are derived with optimal sound absorption under low frequency (20 ⩽ f < 500 Hz), medium frequency (500 ⩽ f < 2000 Hz) and high frequency (2000 ⩽ f < 15,000 Hz), respectively. On top of that, for a given thickness of porous fibrous material layer, the analytical relationship between fiber radius and optimal porosity under set frequency bands is constructed.     

基于遗传算法的同步感应线圈发射装置参数优化

发射速度和能量转换效率是同步感应线圈型电磁发射装置（SICEML）最重要的两项指标。驱动线圈和电枢的结构参数、驱动线圈匝数以及电枢初始触发位置都会对这两项指标产生影响。以上述参数为变量,以发射速度和能量转换效率之积为目标函数,引入遗传算法对单级SICEML参数进行了优化设计,并利用有限元软件进行了仿真验证。结果表明：在储能与发射装置总体体积不变的前提下,优化后的系统效率由5.38%提高到13.6%,出口速度由38 m/s提高到61 m/s,系统性能得到明显改善。利用单级SICEML样机进行了堵驻试验,结果与仿真结果吻合较好,验证了本文提出的遗传算法的可行性。     

Simulations on the wide bandgap characteristics of a two-dimensional tapered scatterer phononic crystal slab at low frequency

Aiming at the problem of low-frequency vibration and noise reduction in the engineering field, a new two-dimensional tapered scatterer phononic crystals slab is designed and the bandgap characteristics and displacement vector field of the model are simulated by means of finite element method. The numerical simulations show that an extremely wide complete bandgap can be achieved at low frequency. Compared with the reference model [Acoust. Phys. 65 (2019) 322], the first complete bandgap of the designed model has a lower starting frequency and a wider bandgap which is expanded by nearly 15 times. Moreover, the mechanism of bandgap generation is analyzed, the influences of geometric parameters and structure symmetry on the band structure are also investigated.     

基于遗传算法的光学膜系初始结构优化设计

膜系初始结构优化设计是膜系优化设计的关键。针对多膜料设计 ,提出了一种新的膜系初始结构优化设计算法 ,将膜系的初始设计视为组合优化问题 ,采用遗传算法 ,求得组合的最优解。给出了算法的原理 ,并给出了相应的设计实例。结果表明 ,本算法是一种简单、有效、通用性强的膜系初始化设计方法     

基于遗传算法的五模材料分层优化*

由于超材料的微结构尺度不能忽略,利用超材料微结构所集成的器件等效参数不是连续分布的,而是呈离散分布的。因此在利用超材料设计声学器件的过程中,需要对器件进行分层离散化,而分层方案的选取往往会影响器件的工作效果。该文基于五模材料水下隐身衣的设计理论,提出了一种基于遗传算法的五模材料隐身衣分层优化策略,并分别对优化前和优化后的分层隐身衣做了声学仿真。仿真结果表明采用优化策略后,隐身衣背景声场的散射能量和反射能量均有大幅度降低,并且对窄带探测信号和宽带探测信号均有较好的隐身效果,因此该分层优化策略能够显著提升隐身衣的隐身效果。该文所提出的分层优化策略为提升五模材料隐身衣性能提供了理论支持,并可以进一步推广至其他超材料器件的微结构设计中。     

Multi parameter optimization of Raman Fiber Amplifier using genetic algorithm for S band dense wavelength division multiplexed system

A simple genetic algorithm is implemented to perform multi parameter optimization of Raman Fiber Amplifier for 100 channel S band dense wavelength division multiplexed system at 25 GHz interval. A cost effective system using single Raman pump is investigated aiming at maximum average gain. The single counter propagating pump is optimized to frequency of 211.528 THz and 652.93 mW power level with optimum Raman fiber length of 44.064 Km. There is evidence to show that the optimum solution presents a small gain variation (less than 3 dB) over an effective bandwidth covering 197–199.475 THz. The optimized configuration enabled an adequate system performance in terms of acceptable Q-factor (19.52 dB) and BER (1.46 × 10⁻²¹).     

Design of URAs by DIRECT global optimization algorithm

Coded aperture imaging (CAI) has evolved as a standard technique for imaging high-energy photon sources and has found numerous applications. Coded aperture arrays (CAAs) are the most important devices in the applications of CAI. In recent years, many approaches were presented to design optimum or near-optimum CAAs. Uniformly redundant arrays (URAs) are the most successful CAAs for their cyclic autocorrelation consisting of a sequence of delta functions on a flat sidelobe, which can easily be subtracted when the object has been reconstructed. Unfortunately, the existing methods can only be used to design URAs with limited number of array sizes and fixed autocorrelative sidelobe-to-peak ratio. In this paper, we presented a method to design more flexible URAs by means of a global optimization algorithm named DIRECT. By our approaches, we obtain various types of URAs including the filled URAs which can be constructed by existing methods and the sparse URAs which have never been constructed and mentioned by existing papers as far as we know.     

遗传算法在二维声子晶体带隙优化中的应用

运用自适应遗传算法对二维声子晶体的带隙宽度进行优化设计，并与平面波展开法相结合，研究了由正方形排列的铅-环氧树脂构成的声子晶体的带隙宽度优化问题，发现自适应遗传算法可以有效地搜索到具有较宽完全声子带隙的优化单胞形式. 关键词： 声子晶体 声子带隙 遗传算法     

Design of a single layer micro-perforated sound absorber by finite element analysis

Micro-perforated sound absorbers with sub-millimeter size holes can provide high absorption coefficients. This paper presents results of work on the development of an effective single layer micro-perforated sound absorber from the commercial composite material Parabeam^® with micro diameter holes drilled on one side. Parabeam^® is used as a structural material made from a fabric woven out of a E-glass yarn and consists of two decklayers bonded together by vertical piles in a sandwich structure with piles (thick fibers) woven into the decklayers. The paper includes, the analytical model developed for prediction of absorption coefficients, finite element solution using commercial software MSC.ACTRAN and experimental results obtained from impedance tube measurements. A simple optimization is performed based on the developed models to obtain an efficient absorber configuration. It has been anticipated that several different and interesting applications can be deduced by combining structural and sound absorption properties of this new micro-perforated absorber.     

ZnO thin film characterization by X-ray reflectivity optimization using genetic algorithm and Fourier transformation

Zinc oxide (ZnO) thin film was fabricated by sol-gel spin coating method on glass substrate. X-ray reflectivity (XRR) and its optimization have been used for characterization and extracting physical parameters of the film. Genetic algorithm (GA) has been applied for this optimization process. The model independent information was needed to establish data analyzing process for X-ray reflectivity before optimization process. Independent information was exploited from Fourier transform of Fresnel reflectivity normalized X-ray reflectivity. This Fourier transformation (Auto Correlation Function) yields thickness of each coated layer on substrate. This information is a keynote for constructing optimization process. Specular X-ray reflectivity optimization yields structural parameters such as thickness, roughness of surface and interface and electron density profile of the film. Acceptable agreement exists between results obtained from Fourier transformation and X-ray reflectivity fitting.     

LCC谐振变换器的优化设计与实现

LCC谐振变换器是电除尘高频高压电源的核心器件,十分适用于高压大功率场合,针对连续模式应用于电除尘高频高压电源的不足,采用LCC谐振变换器断续模式进行优化设计。分析了带RC负载的LCC谐振变换器断续模式(简称DCM)的工作原理及拓扑结构,采用状态空间法推导了其数学模型,研究并建立了新颖的LCC谐振变换器断续模式下的损耗模型。在此基础上提出了一种基于遗传粒子群算法的LCC谐振变换器优化设计方法,该方法直观并且准确,实现了软开关技术,提高了电源的工作效率。并在现场通过一台72KV/85KW的电除尘高频高压电源样机验证了本文的正确性。     

Ultrawide low frequency band gap of phononic crystal in nacreous composite material

The band structure of a nacreous composite material is studied by two proposed models, where an ultrawide low frequency band gap is observed. The first model (tension-shear chain model) with two phases including brick and mortar is investigated to describe the wave propagation in the nacreous composite material, and the dispersion relation is calculated by transfer matrix method and Bloch theorem. The results show that the frequency ranges of the pass bands are quite narrow, because a special tension-shear chain motion in the nacreous composite material is formed by some very slow modes. Furthermore, the second model (two-dimensional finite element model) is presented to investigate its band gap by a multi-level substructure scheme. Our findings will be of great value to the design and synthesis of vibration isolation materials in a wide and low frequency range. Finally, the transmission characteristics are calculated to verify the results.     

遗传算法在变焦曲线优化中的应用

由于变焦系统的凸轮曲线对变焦过程中像面的稳定、操作的灵活性都有重要影响,因此变焦曲线的优化设计有着重要的意义。首次采用遗传算法对机械补偿类型的变焦曲线进行了优化设计,并给出了实例。这样得到的曲线比传统的让变倍组作线性移动得到的曲线要明显平滑,证明了遗传算法用于变焦曲线优化设计的可行性和有效性。     

具有特定频段的左手材料构造与设计优化

为研究具有特定频段的左手材料设计方法. 首先基于传输线理论构造了一种左手材料微观构型, 采用S参数反演法进行数值仿真和等效传输线模型分析, 说明了该构型在特定的尺寸条件下具有左手特性, 并分析了尺寸参数对左手性能的影响. 进而给出了在给定频率附近具有最大带宽、较小损耗的左手材料设计优化问题的数学模型, 并给出了设计实例. 数值设计结果验证了优化模型的适用性和正确性.     

基于遗传算法参数优化的PCNN红外图像分割

构造一种基于遗传算法参数优化的脉冲耦合神经网络(PCNN)红外图像分割算法。该算法首先利用PCNN的全局耦合性和脉冲同步性对输入图像进行点火处理,根据PCNN的输出结果计算熵作为遗传算法的适应度函数,并利用熵的变化量作为遗传算法的收敛依据,对PCNN模型中影响图像分割的参数进行组合优化,结合PCNN生物视觉特性和遗传算法解空间随机搜索能力来寻找关键参数的最优值。将遗传算法和PCNN进行结合可充分发挥二者优势,将本文方法与最大类间方差法（OTSU）、最大熵直方图分割算法和PCNN分割方法进行对比,通过交叉熵、区域对比度等客观指标对分割后的图像进行定量分析,结果表明无论从主观视觉还是客观指标,本文方法分割效果优于其他对比方法。     

基于克隆选择的混合遗传算法在碳纳米管结构优化中的研究

针对分子动力学模拟中碳纳米管的结构优化问题，提出了一种新的优化算法.新的优化算法在遗传算法的基础上，引入了克隆选择机理和模拟退火技术.对五个典型函数的优化测试结果表明，该算法搜索过程稳定性好，可较好地实现全局最优.将其应用于碳纳米管原子结构优化，加快了能量优化速度，提高了优化质量.模拟结果说明，混合遗传算法的优化时间随原子数增加而呈线性增长.在碳纳米管原子数较多时，结构优化时间比共轭梯度法降低一个数量级左右，大大降低了系统的模拟时间. 关键词： 分子动力学 碳纳米管 能量优化 遗传算法 克隆选择算法     

Optimization of a sealed-off CO2 laser resonator by utilizing a genetic algorithm

A genetic algorithm is used to optimize a CO₂ laser resonator. Three optimal parameters of a CO₂ laser resonator (the diameter of the laser discharge tube, the curvature radius of the concave reflector and the transmissivity of the output-mirror) are obtained with the maximum output of the laser power as the objective function in the genetic algorithm. After the optimization, the calculated laser power with the fundamental mode increases by 62% and the measured value increases by 35% in an experiment as compared to a non-optimized case.     

Experimental and calculated research on a large band gap constituting of tubes with periodic narrow slits

A new band gap structure composed of a square array of parallel steel tubes with narrow slits is presented. The propagation of acoustic waves in a two-dimensional composite medium constituted of slit tubes in air is investigated both theoretically and experimentally. The band gap is calculated with the finite element method in which the acoustic-solid coupling is taken into account. The transmissions of the band system with both different single-width narrow slits and multi-width narrow slits are analyzed. Experimental measurements show that the transmission through an array of slit tubes with periodic narrow slits drops to noise level throughout frequency interval in good agreement with the calculated forbidden band. The large band gap and low starting frequency is obtained by arranging different width of slits embedded in the tubes. The experiments and theoretical results show that this new band gap structure has an especial character based on the resonant cavity playing an important role on the band gap besides the traditional Bragg interference.     

Multi-objective optimisation of lidar parameters for forest-fire detection on the basis of a genetic algorithm

A numerical model for the estimation of the laser pulse energy required for forest-fire detection with a predefined signal-to-noise ratio by an eyesafe lidar operating at wavelength of 1.54 μm is developed. This model is coupled with a genetic algorithm, which is used for multi-objective optimisation of the fitness function (weighted sum of laser price, telescope price, and surveillance time) using telescope diameter and laser beam divergence as independent variables.