基于性能的相邻结构间Maxwell阻尼器优化布置研究

对连接Maxwell模型的两相邻钢筋混凝土框架结构进行了基于性能的阻尼器优化布置研究。以使两相邻结构总超越概率最小为优化目标,对确定阻尼器数目下的相邻结构进行了阻尼器优化布置位置的研究,得出了相邻结构间Maxwell阻尼器的优化位置的一般布置规律。通过连接不同优化布置位置的Maxwell阻尼器的相邻结构地震易损性分析,得出了相邻结构间连接Maxwell阻尼器的优化数目。所得相邻结构间阻尼器的优化布置,可以使相邻结构在不同性能目标的地震作用下均能得到较优的控制效果,为实际工程的应用作出了有益探讨。

基于排队论的站台售票窗口仿真与优化

为了分析某车站旅客到达情况和窗口服务时间,通过排队论发现该车站旅客到达服从泊松分布,人工售票窗口服务时间服从负指数分布,是一个多服务台等待的排队模型系统。通过计算旅客的平均到达率,可以得出系统在各个时间段内的服务强度,从而得出大多数时间段售票系统过于拥挤,而有些时候过于空闲,所以需要对各个时间段开放售票窗口的数目进行优化,从而得出各个时间段最佳的开放窗口数目。最后通过FlexSim软件对改善前后的系统进行仿真并对比,结果表明改善后系统的服务强度为0.8~1,系统空闲率低且基本不会出现排队系统过于拥挤的状况,可见相对于改善前的服务系统更加合理。

自适应H-minima的改进分水岭堆叠细胞分割方法

针对传统分水岭方法初始分割结果存在过分割问题,提出自适应H-minima的改进堆叠细胞分割方法。该方法利用不同h值H-minima变换抑制种子噪声,并以对应候选种子为中心,分别采用改进K-均值算法合并初始分割区域,产生候选分割结果;然后,基于形状先验定义圆度指标FuzzyR,并将堆叠细胞平均圆度作为评价函数,自适应提取各堆叠区域最优h值,实现正确分割。实验结果证明,针对于人工合成和真实堆叠细胞图像,算法均能有效抑制过分割、减少欠分割,分割性能显著提高。

Pseudo-static analysis of cantilever retaining walls using upper bound limit analysis approach

Given the extensive utilization of cantilever retaining walls in construction and development projects,their optimal design and analysis with proper attention to seismic loads is a typical engineering problem.This research presents a new algorithm for pseudo-static analysis of retaining walls employing upper bound method.The algorithm can be utilized to design and check the external and internal stability of the wall based on the proposed mechanism.One of the main features of this algorithm is its ability to determine the critical condition of failure wedges,the minimum safety factor and maximum force acting on the wall,as well as the minimum weight of the wall,simultaneously,by effectively using the multi-objective optimization.The results obtained by the proposed failure mechanisms show that,while using the upper bound limit analysis approach,the active force should be maximized concurrent with optimizing the direction of the plane passing through the back of the heel.The present study also applies the proposed algorithm to determine the critical direction of the earthquake acceleration coefficient.The critical direction of earthquake acceleration coefficient is defined as the direction that maximizes the active force exerted on the wall and minimizes the safety factor for wall stability.The results obtained in this study are in good agreement with those of similar studies carried out based on the limit equilibrium method and finite element analysis.The critical failure mechanisms were determined via optimization with genetic algorithm.

基于WBLDA的学术文献摘要主题聚类

为使科研人员节省时间,高效阅读学术文献信息,提出一种学术文献摘要的主题聚类模型——优化主题数目作者层主题聚类模型(WBLDA)。首先在预处理阶段,自定义符合学术文献摘要特点的分词词典和停用词词典,解决学术文献摘要分词不准确的问题;在特征提取阶段,提出增大词频特征提取方法(ITF-IDF),使用词频放大法来增大词频,弱化文本长度对特征权重的影响,提取出更加符合学术文献摘要方向的特征词;最后,针对传统主题模型忽略作者这一重要属性的缺点,在主题聚类模型中引入学术文献摘要的作者信息,构建文档—主题+作者—词的WBLDA模型,同时使用贝叶斯准则优化主题聚类模型的主题数。通过对学术文献摘要数据集仿真实验结果表明,与TF-IDF相比,ITF-IDF方法的特征提取准确率更高;与LDA相比,WBLDA模型的聚类纯度和F-score值也更高,选择出的主题更加准确,更能代表摘要的学术方向。

Design and optimization in multiphase homing trajectory of parafoil system

In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scenario,on the basis of geometric relationship of each phase trajectory,the problem of trajectory planning is transformed to parameter optimizing,and then auxiliary population-based quantum differential evolution algorithm(AP-QDEA)is applied as a tool to optimize the objective function,and the design parameters of the whole homing trajectory are obtained.The proposed AP-QDEA combines the strengths of differential evolution algorithm(DEA)and quantum evolution algorithm(QEA),and the notion of auxiliary population is introduced into the proposed algorithm to improve the searching precision and speed.The simulation results show that the proposed AP-QDEA is proven its superior in both effectiveness and efficiency by solving a set of benchmark problems,and the multiphase homing scheme can fulfill the requirement of fixed-points and upwind landing in the process of homing which is simple in control and facile in practice as well.

An adaptive waveform-detection threshold joint optimization method for target tracking

The joint optimization of detection threshold and waveform parameters for target tracking which comes from the idea of cognitive radar is investigated for the modified probabilistic data association(MPDA)filter.The transmitted waveforms and detection threshold are adaptively selected to enhance the tracking performance.The modified Riccati equation is adopted to predict the error covariance which is used as the criterion function,while the optimization problem is solved through the genetic algorithm(GA).The detection probability,false alarm probability and measurement noise covariance are all considered together,which significantly improves the tracking performance of the joint detection and tracking system.Simulation results show that the proposed adaptive waveform-detection threshold joint optimization method outperforms the adaptive threshold method and the fixed parameters method,which will reduce the tracking error.The average reduction of range error between the adaptive joint method and the fixed parameters method is about 0.6 m,while that between the adaptive joint method and the adaptive threshold only method is about 0.3 m.Similar error reduction occurs for the velocity error and acceleration error.

Composite multiobjective optimization beamforming based on genetic algorithms

All the parameters of beamforming are usually optimized simultaneously in implementing the optimization of antenna array pattern with multiple objectives and parameters by genetic algorithms （GAs）. Firstly, this paper analyzes the performance of fitness functions of previous algorithms. It shows that original algorithms make the fitness functions too complex leading to large amount of calculation, and also the selection of the weight of parameters very sensitive due to many parameters optimized simultaneously. This paper proposes a kind of algorithm of composite beamforming, which detaches the antenna array into two parts corresponding to optimization of different objective parameters respectively. New algorithm substitutes the previous complex fitness function with two simpler functions. Both theoretical analysis and simulation results show that this method simplifies the selection of weighting parameters and reduces the complexity of calculation. Furthermore, the algorithm has better performance in lowering side lobe and interferences in comparison with conventional algorithms of beamforming in the case of slightly widening the main lobe.

NSGA Ⅱ based multi-objective homing trajectory planning of parafoil system

Homing trajectory planning is a core task of autonomous homing of parafoil system.This work analyzes and establishes a simplified kinematic mathematical model,and regards the homing trajectory planning problem as a kind of multi-objective optimization problem.Being different from traditional ways of transforming the multi-objective optimization into a single objective optimization by weighting factors,this work applies an improved non-dominated sorting genetic algorithm Ⅱ(NSGA Ⅱ) to solve it directly by means of optimizing multi-objective functions simultaneously.In the improved NSGA Ⅱ,the chaos initialization and a crowding distance based population trimming method were introduced to overcome the prematurity of population,the penalty function was used in handling constraints,and the optimal solution was selected according to the method of fuzzy set theory.Simulation results of three different schemes designed according to various practical engineering requirements show that the improved NSGA Ⅱ can effectively obtain the Pareto optimal solution set under different weighting with outstanding convergence and stability,and provide a new train of thoughts to design homing trajectory of parafoil system.

Calculation of slope-cover height under price fluctuation in open-pit mines

Leaving ditches between adjacent mining areas can effectively reduce re-stripping in the latter mining area and simultaneously lead to an increment in internal dumping costs in the former mining area. This paper establishes calculation models for these two marginal costs. The optimizing model for slope cover height can be determined by including marginal cost models in the objective function. The paper has two main contributions:(a) it fully considers redistribution of dumping space in the model;(b) it introduces price fluctuations and cash discounts in the model. We use the typical open-pit mine as an example to test and prove the model. We conclude that a completely covered slope is reasonable in Haerwusu open pit mine; in addition to an increasing price index, the slope cover height can be reduced; and that price changes are one of the most important influencing factors of slope cover height optimization in an open-pit mine.

Performance-based passive control analysis of adjacent structures:Optimization of Maxwell dampers

The performance-based passive control analysis of the Maxwell dampers between one 10-story and one 6-story adjacent RC frames is conducted in this work.Not only the optimal parameters but also the optimal arrangements of the Maxwell dampers are proposed based on the optimal target of making the total exceeding probability of the adjacent structures to be minimal.The applicability of the analytical expressions of the Maxwell damper damping parameters under different seismic performance targets are firstly examined and then the preferable damping parameters of the Maxwell dampers are proposed through the extensive parametric studies.Furthermore,the optimal arranging positions and optimal arranging numbers of the Maxwell dampers between the adjacent buildings are derived based on a large number of seismic fragility analyses,as well.The general arranging laws of the Maxwell dampers between the adjacent buildings are generated based on the discussion of the theoretical method through the simplified plane model.The optimal parameters and optimal arrangement of the Maxwell dampers presented make both the adjacent structures have preferable controlled effects under each seismic performance target which can satisfy the requirements of multi-performance seismic resistance of the modern seismic codes.

Optimization of Operational Parameters in a Three Phase AC / DC Reactive Power Compensator

AC / DC converter is a kind of devices applicable to reactive power compensation. Three parameters including losses, Total Harmonic Distortion （THD） and compensation capacity have important role in designing procedure that these parameters are affected by the firing angle. Consideration trade of between these parameters can cause be selected suitable firing angle for optimal working of the compensator. In this paper is defined an objective function which includes the above parameters. This objective function is optimized through appropriate weighting factor for any parameters and the optimal firing angle will be obtained. So, the mention parameters can be selected optimally.

Optimization of Wigley Hull Form in order to Ensure the Objective Functions of the Seakeeping Performance

The research performed in this paper was carried out to investigate the computational procedure to design seakeeping optimized ship hull form. To reach the optimized hull form, four stages should be done, which consists of： generate alternative hull form, seakeeping calculations, objective functions and optimization techniques. There are many parameters that may be determined in ship hull form optimization. This paper deals with developed strip theory for determining the seakeeping performance, genetic algorithm （GA） as optimization method, high order equations for curve fitting of the hull form and finally reaching to the minimum bow vertical motion in regular head waves. The Wigley hull is selected as an initial hull and carried to be optimized. Two cases are considered. For the first case, the only form coefficients of the hull （CB, CM, Cw, Cp） are changed and main dimensions （L, B, 7） are fixed. In the second case both hull form and main dimensions are varied simultaneously. Finally, optimized hull form and its seakeeping performances are presented. The results of optimization procedure demonstrate that the optimized hull forms yield a reduction in vertical motion and acceleration.

An Objective-Based Gradient Method for Locating the Pareto Domain

In this paper, an objective-based gradient multi-objective optimization （MOO） technique, the Objective-Based Gradient Algorithm （OBGA）, is proposed with the goal of defining the Pareto domain more precisely and efficiently than current MOO techniques. The performance of the OBGA in locating the Pareto domain was evaluated in terms of precision, computation time and number of objective function calls, and compared to two current MOO algorithms： Dual Population Evolutionary Algorithm （DPEA） and Non-Dominated Sorting Genetic Algorithm I1 （NSGA-II）, using four test problems. For all test problems, the OBGA systematically produced a more precise Pareto domain than DPEA and NSGA-II. With the adequate selection of the OBGA parameters, computation time required for the OBGA can be lower than that required for DPEA and NSGA-II. Results clearly show that the OBGA is a very effective and efficient algorithm for locating the Pareto domain.

Optimum Determination of Partial Transmission Ratios of Three-Step Helical Gearboxes for Getting Minimum Cross Section Dimension

This paper presents a new study on optimum calculation of partial ratios of three-step helical gearboxes. The chosen objective function is the cross section dimension of the gearbox. In solving the optimization problem, the design equation for pitting resistance of a gear set was investigated and equations on moment equilibrium condition of a mechanic system including three gear units and their regular resistance condition are analyses. From the results of the study, effective formula for determination of the partial ratios of three-step helical gearboxes is introduced. As the formulas are explicit, the partial ratios can be calculated accurately and simply.

The optimal power distribution in cooperative communication relay system

In order to optimize power utilization of relay nodes in cooperative communication,a power allocation algorithm with objective function to maximize system capacity is proposed.Based on the convex optimization theory,an ellipsoid algorithm is used to solve this problem,which could simplify the subgradient choosing steps and improve convergence stability,so that an optimized power allocation algorithm is presented.Theoretical analysis and simulation results show that the algorithm can effectively distribute the power of each node with lower complexity,and ensure the transmission capability of relay nodes in cooperative communication.

冗余驱动变后掠机翼驱动机构优化设计与分析

为满足对宽速域变后掠飞行器的迫切需求,设计了一种适用于分布式驱动的局部旋转变后掠机翼的过约束冗余驱动机构。以传动性能为指标对单元驱动机构进行尺度初步设计,后结合SQP(sequence quadratic program)算法以机构变形全过程的能量转化率为优化目标对机构尺度进行了优化,优化后的驱动机构在恒定作用力下的输出功提高了44.3%,能量转化率提高了37.5%,驱动距离缩短了9.7%。为解决多个驱动支链驱动力如何分配的问题,将分析超静定结构内力的力法与传统机构受力分析方法结合提出一种准静态驱动力的求解方法,对一定负载及构件材料条件下的四翼梁模型进行了驱动力计算并基于ADAMS(automatic dynamic analysis of mechanical system)在相同负载及构件材料条件下做了动力学仿真实验验证驱动力分配模型的精确度,误差分析显示该模型对于准静态驱动过程驱动力计算误差小于5.5%。最后综合仿真结果及驱动机构的质量对驱动链数目进行优化,确定了最佳驱动链数目为3个。

基于动力学分析的发动机测振截面选取

研究了发动机测振截面选择的建模方法和优化算法。确定测振截面选择思路,建立转子-支承-机匣整机模型,计算正常和故障条件下转子动力学特性,并依据总体方案规定的传感器数目,确定测振物理量较大的转子截面或支承位置,完成振动传感器布置方案的初步确定。进一步提出测振方案优化方法,通过对实测数据进行分析,考虑实测信号的信噪比和信息冗余性,确定各测点振动数据有效信息量,判定测振方案是否合理,并选择机载测点。以某型发动机为例,设计监测点布置方案。结果表明:机载测点与该型发动机实际机载传感器测点位置相同,验证了测振方案的建立方法、优化方法和机载传感器选择方法正确可靠。单元敏感度越高,反映转子振动越明显。振动相似度越低,反映发动机整机振动特性越全面。研究结果为航空发动机测振截面布置提供重要依据。

Enhancement of Performance by Blade Optimization in Two-Stage Ring Blower

This paper describes the shape optimization of an impeller used for two-stage high pressure ring blower.Two shape variables,which are used to define an impeller shape,are introduced to increase the blower performance.The pressure of a blower is selected as an object function,and the blade optimization is performed by a response surface method.Three-dimensional Navier-Stokes equations are introduced to analyze the internal flow of the blower and to find the value of object function for the training data.Relatively good agreement between experimental measurements and numerical simulation is obtained in the present study.Throughout the shape optimization,it is found that a hub height is effective to increase pressure in the ring blower.The pressure rise for the optimal two-stage ring blower is successfully increased up to 1.86% compared with that of reference at the design flow rate.Local recirculation flow having low velocity is formed in both sides of the impeller outlet by different flow direction of the inlet and outlet of the impeller.Detailed flow field inside the ring blower is also analyzed and discussed.

Multi-objective parameter optimization for a single-shaft series-parallel plug-in hybrid electric bus using genetic algorithm

Recently, the single-shaft series-parallel powertrain of Plug-in Hybrid Electric Bus （PHEB） has become one of the most popu- lar powertrains due to its alterable operating modes, excellent fuel economy and strong adaptability for driving cycles. Never- theless, for configuring the PHEB with single-shaft series-parallel powertrain in the development stage, it still faces greater challenge than other configurations when choosing and matching the main component parameters. Motivated by this issue, a comprehensive multi-objectives optimization strategy based on Genetic Algorithm （GA） is developed for the PHEB with the typical powertrain. First, considering repeatability and regularity of bus route, the methods of off-line data processing and mathematical statistics are adopted, to obtain a representative driving cycle, which could well reflect the general characteristic of the real-world bus route. Then, the economical optimization objective is defined, which is consist of manufacturing costs of the key components and energy consumption, and combined with the dynamical optimization objective, a multi-objective op- timization function is put forward. Meanwhile, GA algorithm is used to optimize the parameters, for the optimal components combination of the novel series-parallel powertrain. Finally, a comparison with the prototype is carried out to verify the per- formance of the optimized powertrain along driving cycles. Simulation results indicate that the parameters of powertrain com- ponents obtained by the proposed comprehensive multi-objectives optimization strategy might get better fuel economy, meanwhile ensure the dynamic performance of PHEB. In contrast to the original, the costs declined by 18%. Hence, the strat- egy would provide a theoretical guidance on parameter selection for PHEB manufacturers.