一种新型共轴式直升机操纵机构运动学分析

提出一种新型共轴式少自由度混联机构,可以模拟三桨叶共轴式直升机操纵机构的运动,由下操纵3-SPS+PS+RRS并联机构和上操纵混联机构串联而成,整体机构结构简单紧凑,所以可应用于三桨叶共轴式无人机。机构对旋转盘的约束等效为一个PS约束支链,上操纵混联机构等效为几个并联机构后,运用螺旋理论分析上操纵机构的自由度,证明上下倾斜盘运动姿态一致,结合下操纵机构得出整个机构满足三桨叶共轴直升机操纵机构所需的自由度。对上操纵机构中的倾斜盘的姿态角和运动支链的位置进行分析,并得出了在下操纵机构一定倾斜姿态下变距转动角的变化规律。通过PRO/E仿真查看整体机构的运行情况。     

两种针对小信号的脉压优化算法及实现

结合某雷达项目,针对项目LFM和Taylor编码两种小时宽带宽积(TB)信号脉冲压缩效果不理想的问题,通过对两种不同小TB信号的实际回波波形和特性进行了分析,针对性地使用了倒推法和循环迭代法,获得了优化的脉压系数。试验得出结论,较之传统的匹配滤波脉冲压缩系数,采用优化脉压系数的LFM和Taylor编码小TB信号脉冲压缩主副瓣比均能提高十几dB。     

An improved monkey algorithm for a 0-1 knapsack problem

The 0-1 knapsack problem is a classic combinational optimization problem. However, many exiting algorithms have low precision and easily fall into local optimal solutions to solve the 0-1 knapsack problem. In order to overcome these problems, this paper proposes a binary version of the monkey algorithm where the greedy algorithm is used to strengthen the local search ability, the somersault process is modified to avoid falling into local optimal solutions, and the cooperation process is adopted to speed up the convergence rate of the algorithm. To validate the efficiency of the proposed algorithm, experiments are carried out with various data instances of 0-1 knapsack problems and the results are compared with those of five metaheuristic algorithms.     

Synthesis and properties of sulfonated poly(arylene ether ketone sulfone) containing amino groups/functional titania inorganic particles hybrid membranes for fuel cells

In this work, the organic-inorganic hybrid membranes were prepared. The synthesis and properties of the hybrid membranes were investigated. The sulfonated poly(arylene ether ketone sulfone) containing amino groups (Am-SPAEKS) was synthesized by nucleophilic polycondensation. The sol-gel method was used to prepared functional titania inorganic particles (L-TiO₂). The ¹H NMR and FT-IR were performed to verified the structure of Am-SPAEKS and L-TiO₂. The organic-inorganic hybrid membranes showed both good thermal stabilities and mechanical properties than that of Am-SPAEKS. The L-Am-15% membrane exhibited the highest Young's modulus (2262.71 MPa) and Yield stress (62.09 MPa). The distribution of L-TiO₂ particles was revealed by SEM. Compared to Am-SPAEKS, the hybrid membranes showed higher proton conductivities. The L-Am-15% exhibited the highest proton conductivity of 0.0879 S cm⁻¹ at 90 °C. The results indicate that the organic-inorganic hybrid membranes have potential for application in proton exchange membrane fuel cells.     

Heat transfer in dusty fluid with suspended hybrid nanoparticles over a melting surface

The melting effect with the magnetic field performs a significant role in various manufacturing and industrial applications, such as welding, casting, magma-solidification, nuclear engineering, and so forth. The present study focuses on the impact of the melting effect and magnetic field with inhomogeneous heat origination and sink. The formulation of the mathematical model is done by considering fluid with hybrid nanoparticles and dust particles in two different phases. We have considered Fe₂SO₄ and Cu as nanoparticles dispersed in the base fluid water along with suspended dust particles. The set of partial differential equations is reduced by using apt similarity variables and boundary conditions to obtain ordinary differential equations. The numerical solution is approximated using MATLAB-bvp4c adopting the shooting technique. The impact of numerous pertinent physical parameters on the velocity and thermal profiles is plotted and deliberated. Furthermore, the rate of heat flow and friction factor is also tabulated and visualized through the graphs. Streamlines are also drawn to know the behavior of the fluid flow. The rise in values of M_E quickly increases the velocity of the fluid motion but declines the thermal gradient and thickness of its related boundary layer. Also, inclining values of Pr enhance the thermal profile due to the impact of melting.     

Parameter identification of proton exchange membrane fuel cell via Levenberg-Marquardt backpropagation algorithm

It is essential to develop an accurate model of proton exchange membrane fuel cell (PEMFC) for a reliable operation and analysis, in which unknown parameters usually need to be determined. The inherent nonlinear, strong coupling, and diversification of PEMFC model seriously hinder traditional methods to identify the parameters. For the sake of overcoming these thorny obstacles, Levenberg-Marquardt backpropagation (LMBP) algorithm based on artificial neural networks (ANNs) is proposed for PEMFC parameter identification. Furthermore, the performance of LMBP is thoroughly evaluated and compared with four typical meta-heuristic algorithms under three cases. Simulation results indicate that LMBP performs a higher accuracy and faster speed for parameter identification. In particular, accuracy and convergence speed can achieve as much as 99.8% and 95.9% growth via LMBP, respectively.     

Modeling of compressive strength of cemented sandy soil

This paper attempted to show the application of particle swarm optimization in the prediction of the compressive strength of cement sandy soil from the curing period, porosity of sample and percentage of cement. The results of the study show that the unconfined compressive strength of the cement stabilized sandy soil increases with an increasing cement content curing time period. Moreover the compressive strength decreases with an increasing porosity. The compressive strength improvement due to cement treatment has a larger increase in samples with less porosity. In addition, particle swarm optimization algorithm is and accurate technique in estimation of compressive strength of cement stabilized sandy soil. In order to compare of existing correlations, a total number of 100 unconfined compressive tests and 15 scanning electron microscope tests have been conducted on cemented Babolsar sand. It can be concluded that compared to existing correlations models, particle swarm optimization algorithm models give more reliable prediction about compressive strength of cement satblized sandy soil. Moreover, the sensitivity analysis of the polynomial model shows that cement content and porosity have significant impact on predicting unconfined compressive strength.     

Integrated standalone hybrid solar PV,fuel cell and diesel generator power system for battery or supercapacitor storage systems in Khorfakkan,United Arab Emirates

Renewable energy resources play a very important rule these days to assist the conventional energy systems for doing its function in the UAE due to high greenhouse gas (GHG) emissions and energy demand. In this paper, the analysis and performance of integrated standalone hybrid solar PV, fuel cell and diesel generator power system with battery energy storage system (BESS) or supercapacitor energy storage system (SCESS) in Khorfakkan city, Sharjah were presented. HOMER Pro software was used to model and simulate the hybrid energy system (HES) based on the daily energy consumption for Khorfakkan city. The simulation results show that using SCESS as an energy storage system will help the performance of HES based on the Levelized cost of energy (LCOE) and greenhouse gas (GHG) emissions. The HES with SCESS has renewable fraction (68.1%) and 0.346 $/kWh LCOE. The HES meets the annual AC primary load of the city (13.6 GWh) with negligible electricity excess and with an unmet electrical load of 1.38%. The reduction in GHG emissions for HES with SCESS was 83.2%, equivalent to saving 814,428 gallons of diesel.     

基于改进牛顿法的燃-燃联合动力装置建模方法研究

燃-燃联合动力装置(COGAG)以其功率密度大、机动性好等优势，在船舶动力领域展现了很好的发展前景。对燃-燃联合动力装置的部件进行了模块化建模，为提高模型的计算效率和收敛性，对传统的牛顿拉普森（Newton Rapson）迭代法进行改进，建立了COGAG稳态模型。利用四阶龙格库塔法建立动态模型，在python仿真环境下对建模方法进行了仿真验证。仿真结果表明：提出的基于改进牛顿法的燃-燃联合动力装置的建模方法可以实现系统的稳态和动态运行过程，提高了模型稳态计算的收敛速度，为联合动力装置的响应特性研究和控制器的设计提供了模型基础。