Controller design for nonlinear systems using the Contoured Robust Controller Bode plot

In this paper, we develop the Contoured Robust Controller Bode (CRCBode) plot and demonstrate its use in the design of robust controllers for nonlinear single‐input single‐output (SISO) systems. The CRCBode plot shows contours (level sets) of a robust performance quantity on the Bode magnitude and phase plots of the controller. An iterative frequency domain loop‐shaping design approach is employed to eliminate all intersections of the controller frequency response with certain ‘forbidden regions,’ indicating that a standard SISO robust stability and performance criterion is satisfied. Nonlinearities are accounted for by avoiding the maximum forbidden regions over a structured uncertainty set consisting of linearizations of the system dynamics about several operating points. We demonstrate this technique by designing and experimentally verifying a flow‐rate controller for a butterfly‐valve based liquid cooling system, which is robust to valve nonlinearities and flow disturbances. Finally, we compare this compensator with one generated using an automated H _∞ synthesis algorithm and discuss the advantages of the CRCBode approach. Copyright © 2013 John Wiley & Sons, Ltd.     

乙烯分离技术分析

从技术先进性、能耗、流程复杂性和运行稳定性等诸多方面对占据乙烯市场的三大分离技术进行了分析。并认为用户在选择分离技术时应综合考虑各方面因素，把握重点，选择出适合的技术。     

塑料旋转成型的特点与研究

介绍了塑料旋转成型的原理和主要特点，对旋转成型制品中易出现的气泡和弯曲，收缩现象，以及冲击强度低的原因进行了分析研究，相应地提出了减少或消除旋转成型制品中的气泡，减少或消除制品收缩和弯曲，以及提高制品冲击强度的主要途径。     

基于Moldflow CAE和UG/CAD的进气罩模具设计

运用CAE分析和CAD设计相结合的方法,设计了某塑件的四面抽芯直接浇口两板模注塑模具。针对塑件浇注困难的问题,在4种潜在浇注方案的基础上,优先选用直浇方案。运用CAE辅助分析找出最佳浇口位置,然后,针对该方案的流动,做了充填、保压、冷却及翘曲方面的优化,经调整后获得了较优的浇注方案。CAE分析结果表明,运用CAD获得了模腔的分型设计及侧抽芯成型件设计。模具结构为单次分型,开模时,四面滑块同步抽芯,塑件的脱模采用顶针+顶块共同顶出方式,有利于型芯水路的开设,减少塑件的顶出变形,保证塑件的成型质量。综合运用CAE/CAD进行模具结构设计,能够缩短新塑件与模具的开发周期与费用,带来了良好的经济效益,提高企业的市场竞争力。     

螺杆分配机头内部压力场分布的CAE分析

用ANSYS有限元软件对生产宽幅橡胶板材的螺杆分配机头流道内部的压力场进行三维模拟与分析，选择Fluid 142三维六面体单元划分网格，建立螺杆分配机头内部流道的三维有限元模型，得到在一定工艺条件下机头流道内部的压力分布。分析了阻尼块几何形状对压力分布的影响，指出阻尼块可以增加流道内原来速度和压力较高部位的流动阻力，选择合适的阻尼块高度可以使胶料的压力值逐渐趋于横向均匀。     

Hydrodynamics and steel tube wastage in a fluidized bed at elevated temperature

Hydrodynamic measurements were made in a bubbling fluidized bed operated at 550°C at three different excess gas velocities (0.15, 0.40 and ). The bed has a cross-sectional area of with an immersed tube bank consisting of 59 horizontal stainless steel tubes (AISI 304L), 21 of which are exchangeable, thus allowing erosion studies. Capacitance probe analysis was used to determine the mean bubble rise velocity, the mean bubble frequency, the mean pierced bubble length, the mean bubble volume fraction and the mean visible bubble flow rate. Tube wastage was calculated from roundness profiles obtained by stylus profilometry.A redistribution of the bubble flow towards the center of the bed occurs when the excess gas velocity is increased. Measurements along a target tube, situated next to the capacitance probe, usually show greater material wastage at the central part of the tube, since the mean bubble rise velocity and the mean visible bubble flow rate are higher there. It is suggested that the greater material degradation is also an effect of the through-flow of a particle-transporting gas stream in the bubbles. With increasing height above the distributor plate the circumferential wastage profiles for the lowest excess gas velocity show a gradual change from an erosion pattern with one maximum (Type B behavior) to a pattern with two maxima (Type A behavior). Power spectral density distributions of the fluctuating pressure signals show that this is a result of the formation of larger bubbles, when the fluidization regime is changed in the upper part of the bed. At the highest excess gas velocity the bubble flow becomes more constrained due to a more rapid coalescence of the bubbles and the tubes show Type A wastage profiles throughout the bed.     

基于神经网络的城市轨道交通短期客流预测研究

该文结合神经网络来研究城市轨道交通中短期客流预测问题。设计出了基于自回归神经网络的轨道交通客流预测模型、模型描述及其模型训练算法。通过matlab仿真实验来验证预测模型的性能,优于将最小二乘支持向量机与离散一维Daub4小波分析结合起来预测效果。     

Modelling water flow,nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential

A model is presented for the simulation of water flow, heat flow, and nitrate and ammonium transport. Two approaches are used for modelling plant water uptake as well as for plant nitrogen uptake. Nitrogen transformations are accounted for in a very simple way. This paper focuses mainly on water flow modelling, solute transport, and water uptake. Richards' equation is used to model water flow in layered soil profiles with a great variety of boundary conditions. Solute transport is simulated with either a simple convection dispersion equation or with a two-region physical non-equilibrium model to distinguish between mobile and immobile water and solute exchange between these two regions. A macroscopic sink term is added to Richards' equation to account for plant water uptake. This term can be calculated along two different approaches, one of which is based on the concept of root water potential. The root water potential is then continuously optimized to minimize the difference between the climatic demand and the uptake rate.Simulation results are compared with field data from the Netherlands to illustrate the degree to which the model is able to predict water flow, solute transport and plant water uptake. The root water potential optimization model seems to provide the best prediction of water distribution. In particular the shape of the profile, revealing uptake patterns, is quite well reproduced with this model. Comparison of simulated and observed water content profiles seems also to reveal the presence of preferential pathways. The comparisons show also how predicted solute distributions can be improved by using a two-region approach rather than a simple convection-dispersion model.     

流速对投加生物促生剂修复水质效果的影响

为研究水流流速对投加生物促生剂修复水质效果的影响，进行了实验室小试。试验中投加生物促生剂BE10mL／m^3。底泥3000mL，分别考察了水流流速为0、0．050、0．065、0．091m／s时污水中总磷、磷酸盐和总氮的去除情况。试验结果显示，在相同的污泥负荷和BE投加量情况下，流速对污染物去除效果的影响较明显；其中影响最明显的是磷酸盐，去除率高迭99％；得出最佳流速为0．050m／s。