按条件更新参数的自校正控制器

本文对具有有界扰动的线性时不变系统提出了一种新的按条件更新参数的自校正控制算 法.算法的特点是它的计算量与典型的自校正调节器不相上下,但却具有跟随的能力,同时还 能保证闭环系统的稳定.文章对采用此法后的系统稳定性、跟随误差的上限和参数估计的 有界性等问题作了详细的理论分析,最后给出了与其它几种方法对比的仿真结果.     

棉花滩水电站施工期洪水预报

棉花滩水电站施工期洪水预报方案，因施工期短，采用了常规方法，而对于支流永定河顶托问题则突破常规，将流域外的永定河水位引入预报体系，建立多元回归预报方程。从还原结果看，解决了顶托影响，还原精度得到了提高。为满足施工要求，洪水预报密切配合施工，针对不同施工阶段，调整预报方案，抓住重点，确保了施工期防洪安全。     

日本新旧文化女装衣身原型样板的结构对比分析

原型是指结构最简单，但能从本质上反映人体重要特征信息，且力求最大覆盖面的基础图形，是服装制作的基础型。以日本成年女子新旧文化衣身原型样板为研究对象，采用定量、定性分析相结合的方法，对两种衣身原型样板的结构要素，即胸围松量、袖窿深、胸宽、背宽、袖窿宽、省位、省量、前后领围线、肩斜度及前后腰节差，进行探讨分析，指出了新、旧衣身原型的优势和劣势，论证了新原型将取代旧原型而被广泛推广的客观事实。     

Optimization of connecting two communication networks subject to a reliability constraint

This paper considers optimization of two networks with a reliability constraint. The objective is to find some links to connect two networks, at a minimal cost, under the constraint that the system reliability of the resultant network is not less than a given level. A decomposition method based on branch and bound is used for solving the problem. In order to speed up the solution procedure, an upper bound on system reliability in terms of node degrees is applied. In particular, when the threshold P_o is large enough, a new algorithm, the cut tree algorithm, can more effectively give an optimal solution.     

The flowability of fine powders in reduced gravity conditions

The extrapolation of Qian’s semi-theoretical relationship for the transition between cohesive and non-cohesive powder fluidization behavior into regions of low gravity is studied and a validation experiment employing fluidization is discussed. The fluidization experiment utilized fine glass and alumina powders in a fluidized bed and was flown onboard NASA’s reduced gravity aircraft. The transition region between cohesive and non-cohesive behavior is determined for the glass and alumina powders at gravity levels of 1.8, 1.0, 0.38, and 0.16 g. The results are compared to Qian’s model and show fair agreement. The fluidization experiment limitations are discussed and a rotating drum experiment that will reduce the experiment uncertainty, provide quantifiable results, and is suitable for flight onboard NASA’s reduced gravity aircraft is proposed. The rotating drum technique determines the characteristic frequency of the powder’s center of area to detect avalanching. The concept is validated by comparing the characteristic frequency obtained from analyzing a cohesive powder to the characteristic frequency obtained from analyzing a flowable powder.     

压电涡流流量计用传感器材料的研制

重点对压电涡流流量用传感器材料的基本组成与性能关系、外加剂的种类与数量、制备工艺等进行了研究 ,现已研制成功性能优良的涡流流量计用传感器材料(ε=2502,d33=560,Kp>65%,Qm<100,精度 :模拟输出信号≤±1.0%指示值)     

Synthesized sliding mode and time-delay control for a class of uncertain systems

In this note, the sliding mode control (SMC) is incorporated with time-delay control (TDC) during the sliding phase to reduce the switching gain. TDC identifies the unknown system dynamics and disturbance directly for every time-delay. For a system with a lumped perturbation which is relatively slow varying with respect to the sampling interval, a much low switching gain can be used if a reasonably good estimate of the derivative of system state can be obtained using the past information, hence chattering can be reduced or eliminated while retaining the tracking accuracy.     

Surface modification of DF-2 tool steel under the scan of a YAG laser in continuously moving mode

Pulsed Nd:YAG laser with focus diameter of 1.06 μm was used to treat successively and continuously the surface of DF-2 cold work tool steel plate. Surfaces irradiated under a large range of laser setting parameters resulted in very different morphologies and microstructures. Roughness of the treated surface was measured by Talysurf profilometer, whilst surface morphologies and microstructures were investigated by scanning electron microscopy (SEM). Change of crystalline structure and composition of the treated surface layers before and after treatments were studied by energy dispersion spectroscopy (EDX). Cross-sectional micro-hardness of the treated layers was also analyzed. Measured micro-hardness values clearly indicated the performance improvement of the treated surface owing to the formation of martensite. Penetration depth of the micro-hardness varied greatly with the laser irradiating parameters that recursively results in different microstructures. Suitable control of the laser irradiation parameters allowed the accomplishment of highest micro-hardness at the outermost surface.     

Rapid chemical synthesis and optical properties of ZnO ellipsoidal nanostructures

ZnO ellipsoidal nanostructures were rapidly synthesized using a chemical synthesis method at 90 °C without the assistance of aging procedure, calcination, sonication, microwave, laser or any organic additives. The effects of pH values and Zn²⁺ concentration on the morphologies of ZnO nanostructures were investigated. The instantaneous underdeveloped ZnO nanostructures were successfully obtained by using the electrophoretic deposition (EPD). Based on the experimental results, growth mechanism of ellipsoidal ZnO nanostructures was proposed. The ellipsoidal nanostructures are self-assembled by the oriented-attachment growth of primary nanoparticles, involving the end-to-end oriented-attachment along the major axis and the side-by-side oriented-attachment along the minor axis. Two half-ellipsoids of the ZnO nanostructures germinate in sequence. The UV–vis absorption and photoluminescence of the ellipsoidal nanostructures was also studied. This work presents a simple and ultra-fast route for large-scale fabrication of ZnO ellipsoidal nanostructures.     

A double-layer composite electrode based on SrSc0.2Co0.8O3−δ perovskite with improved performance in intermediate temperature solid oxide fuel cells

Dual-layer composite electrodes consisting of a layer adjoining to an Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte composed of 70 wt.% SrSc_0.2Co_0.8O_3−δ + 30 wt.% Sm_0.2Ce_0.8O_1.9 (SScC + SDC composite) and a second layer composed of 70 wt.% SrSc_0.2Co_0.8O_3−δ + 30 wt.% Sm_0.5Sr_0.5CoO_3−δ (SScC + SmSC composite) were fabricated and investigated as potential cathodes in intermediate temperature solid-oxide fuel cells. Thermo-mechanical compatibility between the two electrode layers and between the electrode and the electrolyte were examined by SEM, XRD and EIS. After sintering, no clear boundary between SScC + SDC and SScC + SmSC layers was observable by SEM. The repeated thermal cycling didn’t induce the delamination of the electrode from the electrolyte nor the formation of cracks within the electrode. As a result, stable electrode performance was achieved during thermal cycling and long-term operation. Symmetric cell tests demonstrated that the dual-layer electrode with a ∼10-μm SScC + SDC layer and a ∼50-μm SScC + SmSC layer (SScC + SDC/SScC + SmSC (1:5)) had the lowest electrode-polarization resistance among those tested. Anode-supported fuel cells with an SDC electrolyte and SScC + SDC/SScC + SmSC (1:5) cathode were fabricated. Peak power density as high as 1326 mW cm⁻² was achieved at 650 °C, which was higher than for similar fuel cells with a single-layer SScC + SDC or an SScC + SmSC composite electrode.