Nature inspired 21 branches sneezewort/Achillea ptarmica plant growth pattern–shaped antenna for Ku‐band applications

This reported paper presents the design and analysis of wideband nature inspired planar antenna of 46 × 18 × 1.6 mm³ size, designed using FR4 (Flame Retardant) substrate. The antenna patch is delineated from the growth pattern of sneezewort plant with supplementary notion of golden ratio in branching and branch width. The total number of branches in each stage follows the Fibonacci series and the branch width is calculated from the golden ratio concept. Starting from one feed line and two branches, the maximum numbers of branches are increased to 20. There has been significant enhancement in the radiation performance of proposed geometry by increasing the number of branches to 21 and by modifying ground with T‐shaped slot. The antenna covers wide impedance bandwidth of 8.2 to 16.5 GHz by possessing stable radiation characteristics.     

柜式空调机在矩形空间使用效果的实验研究

实验研究结果表明,送风方向和送风速度挡的合理设置能使空调器达到良好的使用效果,柜式空调机组合工作时,两台空调机的相对位置、导风板的旋转角和出口风速对室内平均温度的影响较大。在合理的风速和机组组合下,送风方向与垂直面成90°以上角时,空调房间的温度分布更趋均匀。     

扁球壳结构的塑性极限分析

本文在文献基础上,分析了矩形底扁壳结构的塑性极限状态.利用机动法分别求出了等矢高方形底、不等矢高矩形底扁球壳的内力和极限荷载,并给出了计算实例.     

弹性地基上的框架计算

重点介绍在力法的基础上所建立的“弯矩分配法”和“角变分配法”的计算方法,以烟台市城市主干道新建工程为例进行了计算,并将计算值同有限元法计算所得值作了比较。     

透水坝渗流流量计算模型的选择

透水坝是针对平原河网地区的地形特点以及农业非点源污染的时空不均匀性而开发的面源污染控制新技术,它既可以拦蓄径流,也具有一定的净化效果.透水坝的过水能力与其几何参数及渗透系数密切相关,可以通过联立渗流方程和达西定律进行计算.一般来说,在渗流量不是很大的情况下,可用矩形模型进行计算,而在贴坡流不可忽略的情况下则应采用梯形模型精确计算渗流量.通过现场试验,实测渗流量与理论值符合较好.     

异步电机效率优化控制及动态响应研究

针对异步电机效率优化问题,在黄金分割法和模糊搜索控制法的基础上,提出了一种新型混合控制方法。该方法在模糊控制中设计了合理的比例因子和隶属度函数,保证了在初始阶段搜索步长,根据电机工况进行在线调整,减小了电磁转矩的波动。在优化的后半段中接入黄金分割法,有效解决了模糊控制在最优点附近振荡和收敛速度慢的问题,保证了系统的稳定性。同时针对弱磁情况,给出了一种动态电流分配策略以提高系统动态响应速度。仿真结果验证了新型混合搜索法和动态电流分配法的有效性。     

不同矩形截面的两个平行永磁体磁力解析模型

为了解决不同矩形截面的两个平行永磁体磁力数值计算复杂、缺乏易于计算的磁力解析模型问题,基于磁荷法和虚位移法得到两细长永磁体磁力公式,采用四重积分法建立了新的不同矩形截面永磁体磁力解析模型,分析了磁力与永磁体结构参数的关系,ANSYS仿真验证了模型的正确性。结果表明:该解析模型计算值和ANSYS仿真值吻合,采用该解析模型进行磁力计算相对简单快速,当用第1级别细分网格时,ANSYS仿真与解析模型计算的平均误差为6.17%,误差满足工程要求。该解析模型为Halbach永磁导轨设计及其结构优化提供支持。     

嗜铁钩端螺旋菌氧化难处理金矿的研究

采用改良双层板方法从酸性矿坑水(AMD)中筛选、鉴定并命名为氧化效果最佳的分离株—嗜铁钩端螺旋菌(Leptospirillum ferriphilum)LJ-02。当温度在36~46℃范围内,矿石氧化率呈现出先升后降的趋势;降低pH对提高细菌氧化能力有着显著影响;在接种量不超过10%(v/v)的条件下,接种量的提高有利于矿石的生物氧化。该菌株对难处理金矿的吸附属于Langmuir等温吸附,其吸附平衡常数为8.72"10-10 mL/cells,单位质量矿物颗粒的最大吸收能力为1.99"109 cells/g。     

Multiple characteristic model‐based golden‐section adaptive control: Stability and optimization

The characteristic model‐based golden‐section adaptive control (CM‐GSAC) law has been developed for over 20 years in China with a broad range of applications in various fields. However, quite a few theoretical problems remain open despite its satisfying performance in practice. This paper revisits the stability of the CM‐GSAC from its very beginning and explores the underlying implications of the so‐called golden‐section parameter l₂≈0.618. The closed‐loop system, which consists of the CM and the GSAC, is a discrete time‐varying system, and its stability is discussed from three perspectives. First, attentions have been paid to select the optimal controller coefficients such that the closed‐loop system exhibits the best transient performance in the worst case. Second, efforts are made to improve the robustness in the presence of parameter estimation errors, which provide another choice when designing the adaptive controller. Finally, by measuring the slowly time‐varying nature in an explicit inequality form, a bridge is built between the instantaneous stability and the time‐varying stability. In order to relax the constraints on the parameter bounds of the CM, the GSAC is further extended to multiple CMs, which shows more satisfying tracking performance than that of the traditional multiple model adaptive control method. Copyright © 2014 John Wiley & Sons, Ltd.     

Use of multiple modes of flight subsidy by a soaring terrestrial bird,the golden eagle Aquila chrysaetos,when on migration

Large birds regularly use updrafts to subsidize flight. Although most research on soaring bird flight has focused on use of thermal updrafts, there is evidence suggesting that many species are likely to use multiple modes of subsidy. We tested the degree to which a large soaring species uses multiple modes of subsidy to provide insights into the decision-making that underlies flight behaviour. We statistically classified more than 22 000 global positioning satellite–global system for mobile communications telemetry points collected at 30-s intervals to identify the type of subsidized flight used by 32 migrating golden eagles during spring in eastern North America. Eagles used subsidized flight on 87% of their journey. They spent 41.9% ± 1.5 (, range: 18–56%) of their subsidized northbound migration using thermal soaring, 45.2% ± 2.1 (12–65%) of time gliding between thermals, and 12.9% ± 2.2 (1–55%) of time using orographic updrafts. Golden eagles responded to the variable local-scale meteorological events they encountered by switching flight behaviour to take advantage of multiple modes of subsidy. Orographic soaring occurred more frequently in morning and evening, earlier in the migration season, and when crosswinds and tail winds were greatest. Switching between flight modes allowed migration for relatively longer periods each day and frequent switching behaviour has implications for a better understanding of avian flight behaviour and of the evolution of use of subsidy in flight.