Control of discrete time nonlinear systems with a time-varying structure

In this paper, we present a control methodology for a class of discrete time nonlinear systems that depend on a possibly exogenous scheduling variable. This class of systems consists of an interpolation of nonlinear dynamic equations in strict feedback form, and it may represent systems with a time-varying nonlinear structure. Moreover, this class of systems is able to represent some cases of gain scheduling control, Takagi-Sugeno fuzzy systems, as well as input-output realizations of nonlinear systems which are approximated via localized linearizations. We present two control theorems, one using what we call a “global” approach (akin to traditional backstepping), and a “local” approach, our main result, where backstepping is again used but the control law is an interpolation of local control terms. An aircraft wing rock regulation problem with varying angle of attack is used to illustrate and compare the two approaches.     

Effect of temperature on the development of the yam moth, Dasyses rugosella Stainton (Lepidoptera: Tineidae)

Studies on the effect of temperature on the development of the yam moth, Dasyses rugosella Stainton were carried out in the laboratory at four different temperatures, 20°C, 24°C, 29°C and 33°C. The mean fecundity per female at 20°C, 24°C, 29°C and 33°C was 37.6±1.9, 84.2±2.7, 112.3±3.9 and 109.3±3.9 eggs, respectively. Oviposition period ranged from 4.7 days at 20°C to 2.9 days at 33°C. Hatchability of eggs was highest at 29°C with 70.0% and lowest at 20°C with 15.0%. The developmental time decreased with increase in temperature. The mean developmental time at 20°C, 24°C, 29°C and 33°C was 13.8±0.3, 7.8±0.2, 5.1±0.2 and 3.9±0.2 days for the egg, 90.0±0.7, 50.1±0.7, 36.1±0.8 and 23.6±0.8 days for the larval stages, 22.3±2.6, 12.2±0.2, 10.1±0.1, and 7.8±0.2 days for the pupa and 126.1±0.8, 70.1±0.8, 51.3±0.9, and 35.1±0.8 days for the period from egg hatching to adult emergence, respectively. Since fecundity, oviposition and development of the moth were impaired at 20°C, storage of yam tubers at low temperatures (well below 20°C but not lower than 12°C to avoid chilling injury) will significantly retard the development of D. rugosella and help in its control. Unmated individuals lived longer than their mated counterparts. Adult females were always larger than the males. The wing span of the female ranges from 16.9-18.5 and in males from 13.0-15.0 mm. The body length for males ranged from 5.0-6.5 and was 6.5-9.0 mm for females.     

SolidWorks在扑翼微型飞行器设计制造中的应用

扑翼微型飞行器是一种模仿鸟类或昆虫飞行的新概念飞行器。介绍SolidWorks设计软件在驱动机构运动仿真、翅翼频率分析和参数化设计中的应用。结果表明,SolidWorks应用于扑翼微型飞行器设计制造可以简化设计流程,提高设计效率。     

Vortical flows over a delta wing at high angles of attack

The vortex flow characteristics of a sharp-edged delta wing at high angles of attack were studied using a computational technique. Three dimensional, compressible Reynolds-averaged Navier-Stokes equations were solved to understand the effects of the angle of yaw, angle of attack, and free stream velocity on the development and interaction of vortices and the relationship between suction pressure distributions and vortex flow characteristics. The present computations gave qualitatively reasonable predictions of vortical flows over a delta wing, compared with past wind tunnel measurements. With an increase in the angle of yaw, the symmetry of the pair of leading edge vortices was broken and the vortex strength was decreased on both windward and leeward sides. An increase in the free stream velocity resulted in stronger leading edge vortices with an outboard movement.     

从汶川地震认识结构抗震设计中填充墙的作用

本文主要从汶川大地震对房屋建筑结构的破坏形态出发,结合抗震规范分析了填充墙布置及其在框架结构抗震中的作用。提出了设置框架柱构造翼墙的设计思路及设置方法,简要介绍了在结构细部构造设计和建筑物使用管理方面的一点建议。     

Activity of a melimine derived peptide Mel4 against Stenotrophomonas,Delftia, Elizabethkingia,Burkholderia and biocompatibility as a contact lens coating

Purpose

To determine the antimicrobial activity of the melimine derived peptide Mel4 against Delftia, Stenotrophomonas, Elizabethkingia, Burkholderia and to investigate biocompatibility of Mel4 as an antimicrobial coating on contact lenses in animals and humans.

基于贝叶斯网络理论与仿生技术的翼形量水槽优化

翼形量水槽的工作原理决定其工作必然导致一定的水头损失,保证量水槽自由出流的渠道比降随水头损失增大而增大,本文希望通过仿生优化减小翼形量水槽工作水头损失,扩大其在平原灌区渠道的适用范围。本文探索性的利用鸟类翅膀飞行减阻特性选取3种鸟翼作为仿生原型,截取仿生翼形曲线10条,按10个攻角水平应用处理得到78条仿生翼形量水槽外轮廓线,选取3个收缩比开展3种流量工况的仿真试验,采用极差分析法评价仿生翼形量水槽外轮廓线二因素的显著性水平和优水平,较新颖的运用贝叶斯网络图模型推理分析方法解决仿生翼形曲线和攻角优组合的不确定性问题,通过模型试验验证应用可行性。结果表明：翼形曲线是影响优化的主要因素,赛鸽翼（1）为优曲线、－10°为优攻角;攻角－5°与翼形曲线赛鸽翼（1）联合作用效果最佳,将翼形曲线赛鸽翼（1）按攻角－5°应用处理的仿赛鸽翼截面曲线作为优选仿生翼形量水槽外轮廓线;新型仿赛鸽翼截面曲线型量水槽各工况临界淹没出流状态：测流精度很高（测流平均误差约1.28%）、壅水高度平均降低7.46%、水头损失平均降低5.81%、最大临界淹没度可达0.933、上游佛汝德数均小于0.4（可形成平稳缓流）、最小工作比降可达1/4960。综上,利用仿生技术优化翼形量水槽可行,新型仿赛鸽翼截面曲线型量水槽综合量水性能很好,可用于灌区小比降渠道精细量水。     

Experimental investigation of the effects of contraction on tsunami-induced forces and pressures on a box section bridge

Many bridges that lie within possible tsunami inundation zones are critical links in transport networks. Some efforts have been made to determine the effects of tsunamis on bridges, but only a limited range of published design guidelines are available. Therefore, it is necessary to further investigate the effects of tsunamis on bridges. In the current study, physical modeling experiments were carried out to measure bore impact forces and pressures for various tsunami bore strengths on a bridge deck with different abutment types (wing wall and spill-through) and different opening and submergence ratios. The experiments were conducted in a wave flume with dimensions of 14 × 1.2 × 0.8 m (length × width × height), equipped with an automatic gate designed to generate a tsunami bore. The horizontal and vertical forces showed an increasing trend with increasing submergence ratio for both types of abutment. However, the horizontal force showed a decreasing trend as the opening ratio decreased, while the vertical force initially increased as the opening ratio decreased, until it reached a peak value, and then it started to decrease. The overall shapes of the results for both types of abutment are similar, with higher values for spill-through abutments due to their lower energy dissipation rates. Based on the experimental data, empirical equations are proposed for estimation of tsunami loads as a function of opening and submergence ratios.     

基于虚拟技术的飞机机翼结构健康监控技术研究

飞机机翼结构健康收态的好坏直接影响到飞机各阶段的飞行品质。为了对机翼结构的健康状况进行监控，必须进行大量的实验验证，而虚拟仪器技术使传统仪器的某些硬件乃至整个仪器都能被计算机软件所代替。针对上述趋势，以飞机机翼结构为例，借助于虚拟仪器技术，利用LABVIEW构建的飞机机翼结构健康监控系统，具有实时性和报警能力，基本实现了检测功能。     

翼片的数控加工工艺研究

通过对翼片类零件的结构分析,指出了装夹定位方式、加工方法及切削参数是影响其加工质量的主要因素,并结合实例,提出了3种因素的选择方法,为翼片的加工提供了质量保证。在翼片的数控加工工艺研究过程中,涉及到零件加工过程建模技术、基于正交试验法的切削参数优化技术以及淬硬钢的高速切削技术,这些技术的应用分析对装夹定位方式、加工方法及切削参数的选择效果明显,所得结论与实际加工检验数据基本一致,对翼片的加工具有实际指导意义。