基于双极偏好控制的多目标粒子群优化算法

考虑双极偏好信息对粒子群的控制作用,提出一种使用双极偏好——正偏好和负偏好引导粒子群向 Pareto 前沿偏好区域进化的方法．根据TOPSIS 决策法思想,将外部种群粒子与正负偏好点的相对贴近度排序作为 外部种群管理和全局最优解更新策略;根据贴近度值确定解集的分布度;选取6 种不同类型的多目标测试函数进行 算法模拟,从世代距离、空间测度和超体积测度3 个指标与基于单极偏好的多目标粒子算法进行性能比较．结果显 示,基于双极偏好控制的多目标粒子群算法的收敛性和综合性能更优秀．     

Cryo-EM image alignment based on nonuniform fast Fourier transform

In single particle analysis, two-dimensional (2-D) alignment is a fundamental step intended to put into register various particle projections of biological macromolecules collected at the electron microscope. The efficiency and quality of three-dimensional (3-D) structure reconstruction largely depends on the computational speed and alignment accuracy of this crucial step. In order to improve the performance of alignment, we introduce a new method that takes advantage of the highly accurate interpolation scheme based on the gridding method, a version of the nonuniform fast Fourier transform, and utilizes a multi-dimensional optimization algorithm for the refinement of the orientation parameters. Using simulated data, we demonstrate that by using less than half of the sample points and taking twice the runtime, our new 2-D alignment method achieves dramatically better alignment accuracy than that based on quadratic interpolation. We also apply our method to image to volume registration, the key step in the single particle EM structure refinement protocol. We find that in this case the accuracy of the method not only surpasses the accuracy of the commonly used real-space implementation, but results are achieved in much shorter time, making gridding-based alignment a perfect candidate for efficient structure determination in single particle analysis.     

Safety assessment of the NET Predesign

Work carried out by European Associations on Safety and Environment inside the EC Fusion Technology Programme and by NET has been concentrated on safety-related guidance and on safety assessment of the NET Predesign. Emphasis has been put on analysis of accident sequences of regulatory concern up to worst case accidents, including quantification of consequences to components, systems, and plant, and of doses to the public. Probabilistic safety studies for the most important systems and broadly for the entire plant have been performed to supplement the calculated accidental doses by expectation values for their occurrence rate, and to check the relevance of the reference accident sequences selected initially by judgment. Waste masses per year of operation and for decommissioning have been quantified. For two countries and according to the practices and regulations of these countries, volumes of radioactive waste packaged for final disposal have been determined.Presented at the IAEA Technical Committee Meeting on Developments in Fusion Safety, Toronto, June 7–11, 1993.     

Recent development and applications of an optical method for measurements of thermophysical properties

The experimental determination of thermophysical properties has been greatly improved by the introduction of laser technology. The laser beam is used for sensing and also for heating (or exciting) the specimen. The advantage of using a laser beam is most strongly felt in the measurement of the thermal conductivity or the thermal diffusivity, which are some of the most difficult properties to measure. Interesting features of new techniques for investigating various aspects of thermal conductivity in fluids and solids are reviewed. An optical method, the so-called forced Rayleigh scattering method, or the laser-induced optical-grating method, has been developed and used extensively by the present author's group. The method is a high-speed remote-sensing method which can also quantitatively detect anisotropy, namely, direction dependence of heat conduction in the material. It was used for determination of the thermal diffusivity and its anisotropic behavior for high-temperature materials such as molten salts, liquid crystals, extended polymer samples, and flowing polymer melts under shear. Interesting applications of the method were demonstrated also for thermal diffusivity mapping and microscale measurement.Invited paper presented at the Twelfth symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

考虑电-氢-热多能互补的微网多目标优化配置研究

氢储能具有储能容量大、储存时间长、清洁无污染、实现多种能源网络互联互补和协同优化等诸多优点,有望成为推动分布式能源发展和提升终端能源利用效率的重要支撑技术。为了提高独立型微网供电可靠性及可再生能源利用率,本文建立了考虑电-氢-热多能互补的独立微网多目标优化配置模型,并基于模拟退火的粒子群算法对目标问题进行求解。最后,通过东北某地独立微网优化配置算例,基于MATLAB平台验证了所提多能互补配置方案较传统电储能配置方案负荷失电率降低了3.18%,可再生能源利用率提高了8.37%,所提配置方案可有效促进可再生能源消纳,保证独立微网的供电可靠性。     

Simulation analysis and experimental verification of coal suction characteristics of the new railway tunnel fallen coal dust collection device北大核心CSCD

Due to air turbulence, large areas of coal will fall when the special coal-transportation trains pass the tunnel exits and entrances. Aiming at the problems of low efficiency and high cost of manual cleaning for long distance coal cleaning in the tunnel, a new railway tunnel fallen coal dust collection device which was composed of a main conveying coal feeding pipe and multiple branch pipes of coal suction was designed. It was used to clean the small particles and lightweight railway tunnel fallen coal. Firstly, the gas-solid two-phase flow model based on the Euler-Lagrange approach for the design of the main conveying coal feeding pipe was established in the coal conveying pipelines. Secondly, the effect of the coal particles' incident angle and multiple branch pipe spacing on the main coal conveying pipe flow field, which was based on Fluent finite element simulation software, was studied. What was more, the optimal angle of incidence and the optimal value of the number of branch coal suction pipe, which was installed on the main conveying pipe, were analyzed. Finally, the finite element simulation was verified by field test. Simulation and experimental results showed that it was more conducive to the railway tunnel fallen coal transportation when coal particles' incident angle was less than 45° and the branch pipe spacing was in the vicinity of 750 mm. For that when incident angle was less than 45°, the main conveying coal pipe pressure-drop became weaker and particle flow could obtain large horizontal transport velocity. And when the branch pipe spacing was in the vicinity of 750 mm, the horizontal transport velocity had a smaller fluctuation range and the transportation of coal was larger than that of the other groups. The research results are of great significance to improve the structure of the main conveying coal pipe, increase the efficiency of tunnel coal conveying and optimize the railway tunnel coal dust collection device.     

Dynamic response of Kevlar®29/epoxy laminates under projectile impact-experimental investigation

This authors of this article investigated the dynamic response of woven Kevlar®29/epoxy laminates subjected to the impact loading. The cylindrical aluminum foam projectile and steel projectile were used to exert the impulse on the laminates. Deformation/failure modes, deflections, strain histories, and failure mechanisms were obtained and discussed. The results showed that with the high toughness of Kevlar fiber, the deformation modes of the laminates exhibited some characteristics similar to the metal panel, such as large global deformation. The failure mechanisms like matrix failure, fiber splitting, and fibrillation were observed. These micron failures led to the macroscopic delamination and fracture of the laminates.     

Reconstructing design parameters of a rectangular resonator via peak signal-to-noise ratio and global optimization algorithms

This article proposes an approach for reconstructing physical parameters of a sample in a rectangular resonator during microwave radiation, knowing a priori, its electric field distribution. The inverse problem was solved using two global optimization algorithms and the peak signal-to-noise ratio (PSNR) criterion. First, the Self-regulated Fretwidth Harmony Search algorithm (SFHS) identified suitable resonant frequencies for a given configuration. Next, the unified Particle Swarm Optimization (UPSO) optimized said configuration. Together, they became a maximization strategy of the PSNR through a dual optimization process. Results showed the ability of the approach for estimating the height of each sample block and the resonating frequency of the cavity. This process takes longer to finish as a higher PSNR is demanded (mainly due to the aforementioned dual optimization). Even so, it allows for more similar electric field distributions between both, the direct and inverse problems.     

Erosion coupled dynamic mesh analysis for location of maximum erosion in 90-degree bends for gas-solid flows

The progressive change in the surface geometry of the component due to erosive wear affects the correct estimation of erosive wear performance and service life of the components handling particulate flows. The current study focuses on determining the change in the location of higher erosion on the bend surface during the pneumatic conveying of solids with continuous geometric modification due to erosive wear. Computational fluid dynamics (CFD) based erosion-coupled dynamic mesh methodology is adopted to simulate the time-dependent surface modification of the 90° bend geometry due to erosive wear. Available experimental data are used to validate the numerical results. Further, the erosion distribution and the location of the maximum erosion for different flow velocities, particle sizes, and bend radius ratios with the increase in solid throughput are investigated. It has been found that the modification in the bend geometry due to erosion influences the location of the maximum erosion. The increase in thickness loss due to erosion increases the variation in the location of the maximum erosion. Furthermore, an equation for predicting the location of maximum erosion of bend geometry is obtained based on the bend radius ratio and the thickness loss.     

Direct numerical simulations for assessment of gas-solid drag models in two-dimensional random arrays of particles

The momentum exchange between the phases plays a vital role in modelling of gas–solid flows and it is mathematically described by drag models. However, no consensus exists on which drag model gives the most accurate prediction of the drag force, and, despite the increase in available computing power, the same drag models are used in two-dimensional and three-dimensional simulations. In this study, direct numerical simulations of gas flow through multiple random configurations of static monodisperse particles are performed. The variations of solid volume fraction and particle Reynolds number are in the ranges of 0.05–0.4 and 13.7–136.9, respectively. The drag force exerted on particles is calculated and properly averaged. Based on the simulation results, thirteen drag models are compared and correction factors are introduced using the stochastic gradient descent algorithm. The correction factors provide a simple adjustment for the models to be used in 2D modelling.