Structural load alleviation using distributed delay shaper: Application to flexible aircraft

Lightweight flexible aircraft suffers from unwanted oscillatory vibrations during aircraft manoeuvres. A recently developed distributed-delay signal (DZV) shaper is therefore proposed to be applied as a feedforward controller to alleviate the manoeuvre loads, as an alternative to traditional structural filters used routinely in this context. Structural filters are essentially linear low-pass filters with bandwidth below the significant flexible modes, applied to control signals generated either by the pilot’s direct input or by the flight control system. It has been showed that if instead a properly tuned signal shaper is used, better performance can be achieved: first, the target modes are significantly attenuated while the responsiveness of the aircraft is less compromised and secondly, the oscillatory nature of the vibrations are reduced. The high fidelity simulation results on a full scaled dynamic model of a highly flexible blended wing–body (BWB) aircraft show that in comparison to traditional structural filters, signal shapers significantly reduce the wing root loading (forces and moments) which provides potential structural benefits.     

Making urban real estate markets work for the poor: Theory, policy and practice

This paper explores the relationship between theory, policy and practice, linking urban real estate markets and poverty alleviation. The paper argues that the contribution of urban real estate markets to poverty alleviation has not been optimised due, in part, to inadequate or inappropriate policy. The article attributes this to conceptual and methodological problems arising from the traditional neoclassical analysis of urban real estate markets, ambivalence to the idea that freer markets in real estate are a good thing for the urban poor and insufficient regard to lessons of experience from years of implementing urban anti-poverty land projects. Based on new analytical perspectives provided by institutional economics, this paper proposes specific policy interventions more likely to facilitate pro-poor outcomes in urban real estate markets.     

近地边界层台风观测及湍流特征参数分析

通过近海岸测风塔获取了台风达维(0518)、珍珠(0601)、派比安(0606)登陆过程中10m高度三维脉动风速数据,对近地10m高度平均风特性和湍流特性进行了分析和研究。基于台风观测结果,分析了不同来流方向和地貌状况下,风剖面指数值、摩擦速度、湍流度和阵风因子等湍流参数及其相关性。分析结果表明: 摩擦速度与平均风速呈正相关,摩擦速度随平均风速增大而增大;风剖面指数值随平均风速增大而减小;各方向湍流度随平均风速增大而减小;阵风因子与湍流度呈线性关系。通过拟合实测湍流参数相关性,提出了10m标准高度台风湍流度、阵风因子的计算式,可为台风多发区域低矮房屋的抗风设计提供参考.     

大跨屋盖结构下压风荷载确定方法与实例分析

介绍了几种大跨度屋盖结构下压风荷载的计算方法,并以某大型体育场屋盖为例,通过引入峰值因子和位移匹配度判据,分析了等效荷载作用下位移响应值和空间分布的合理性。研究结果表明,按比例放大的阵风荷载因子法和动力放大系数法,当计算基准值较小时,得出的放大倍数过高,将导致除等效目标之外的响应值被高估。采用准静态荷载与均匀分布附加风振力的线性叠加方法得出的等效荷载将给出较为合理的位移响应值,其中又以结合LRC方法的等效荷载位移匹配度最高。此外,研究表明若不考虑风洞试验结果,按体型系数+0.2在半跨屋盖上作用均匀风荷载,也能给出基本合理、工程上可用的下压风荷载。     

含扶贫式光伏农村配电网电能质量综合控制技术研究

针对含扶贫式光伏的农村配电网运行特点,提出在逆变器功率控制的基础上,光储联合发电分时协调控制技术。分析了扶贫式光伏电源接入农网后逆变器电压/无功控制原理,在某低压台区建立了光储联合发电系统。其中对逆变器设置死区控制环节保证无功调节优先性,同时分时对光伏电源和储能进行协调控制,平滑功率输出。最后结合Opendss软件对某低压台区进行验证,仿真结果表明所提控制策略能够有效提升农网电能质量运行水平。     

大缩尺比气弹模型风洞试验紊流积分尺度修正

风洞试验气弹模型缩尺比常选为1/300~1/800以满足紊流积分尺度相似要求,但一些复杂结构气弹模型实际缩尺比为1/40~1/100以减少模型加工难度及提高模型精度。这类大几何缩尺比造成紊流积分尺度的相似性严重偏离,必须对紊流积分尺度不相似时的风洞试验结果偏差进行修正。基于随机振动理论,推导了考虑1阶基本振型的顺风向风振响应及风振系数计算表达式。通过对一格构式输电塔风振响应分析,研究了顺风向紊流积分尺度Lxu对该结构风振响应的影响。研究结果表明：紊流积分尺度对结构抖振响应有显著影响,对峰值响应及风振系数影响也较大。对于该塔1/40大缩尺气弹模型风洞试验,由紊流积分尺度不相似带来的风振系数试验值的最大偏差可达27%,风振系数平均偏差也接近14%,试验结果偏保守。为便于应用,建议了较为通用的、由紊流积分尺度不相似引起的修正系数,这一修正系数随着结构阻尼比、结构频率与风谱卓越频率的比值（频率比）的增加而减小。     

Fenay Beck Flood-Alleviation Scheme

The paper describes flood detention and channel improvement schemes which have been designed to alleviate the flooding of domestic and industrial properties to a 50-year standard of protection. Landscape architects were incorporated into the design teams to cover environmental aspects.
The flood-detention dam would have been constructed mainly of colliery waste, and the design of the concrete horseshoe spillway and stilling basin was checked using a 1 : 40 physical model. River regulation would be by an automatic vertical gate activated by downstream water levels.
Following planning refusal, a channel-improvement scheme was adopted, which is presently under construction. Reduction in valley storage increased downstream flows, necessitating the enlargement of an old brick and concrete culvert within the ICI works to ensure that there were no detrimental effects within their boundary. An increased benefit/cost ratio of 3.46, as compared with 2.55 obtained for the detention scheme, was partly due to the application of new standards.     

冷链仓储创新装备在河南鲁山精准扶贫中的应用分析

文章对鲁山县董周乡酥梨冷箱仓储扶贫试点应用项目的实施情况开展了专题调研,现将多功能模块化组合冷箱配套农产品市场经营策略精准促进鲁山县董周乡农村产业扶贫的实施情况做系统阐述。