含时变滞后的不确定系统的时滞相关型鲁棒控制设计

研究含时变滞后的不确定系统的控制综合问题. 基于Lyapunov方法提出了一种含滞后补偿的鲁棒控制设计方法. 闭环稳定性条件由一组线性矩阵不等式表示. 在这些条件中给出了稳定性和滞后以及其导数之间的关系. 实例显示, 利用提供的方法所给出的结果比以往文献给出的结果保守性小.     

Performance improvement using time delays in multivariable controller design

A new controller for linear multivariable ordinary systems is suggested in which distributed delays are included in the feedback loop. A general design approach to obtain this type of controller is suggested. It is shown that the resulting closed-loop system is asymptotically stable under some sufficient conditions. Sufficient conditions are derived under which the disturbance attenuation, the robustness against parameter variations, and the time-delay stability margins are improved by the proposed controller. The state feedback tracking controller and the dual-state observer are obtained by modification of the proposed controller.     

Surimi-Starch Interactions Based on Mixture Design and Regression Models

Interaction effects of starch mixtures within surimi gels were investigated by modified distance-based design and analyzed by linear and nonlinear backward regression models. Nonlinear regression model showed highly significant interaction terms of starch-surimi, starch-water, and starchstarch. The response trace plot revealed that shear stress and shear strain were quite sensitive to changes in amounts of starch components. Optimum solution with combinations of various starches, surimi, and water was provided using linear and nonlinear programming.     

亚临界和超临界状态下甲苯-多环芳香烃体系的气液相平衡

The phase behaviors of toluene/polycyclic aromatic hydrocarbon mixture systems were investigated with a continuous-flow type apparatus at 573.2,598.2.623.2 and 648.2K,while the pressure changed from 1 tp 5 MPa,The pseudo-binary phase behaviors were predicted with the Peng-Robinson equation of state with interaction parameters between toluene and pseudo-components considered.The phase diagrams of the system have been classified following the category of phase boundary diagram models.The extraction selectivity and efficiency of toluene as a solvent was discussed by comparing with that of hexane .The prediction model for selectivity was also suggested.     

UPGRADING SPENT LAYER MEAT BY MECHANICAL DEBONING AND FURTHER PROCESSING

Spent layer chickens, an underutilized, inexpensive source of animal protein in the United States, were used to produce an acceptable all chicken frank following mechanical deboning of the chicken parts without pregrinding. The franks were subjected to shear tests and compared to two well-known commercial brands of chicken franks for overall acceptability by an untrained 59 member panel. The franks produced from mechanically deboned spent layer chickens (Lab franks) had greater resistance to shear than the two commercial brands and the panelists showed significantly greater preference for one of the commercial brands. Comments of the panelists indicated the texture of the lab-prepared franks was tougher than the two commercial brands. However, 12 members of the panel stated the lab-frank texture was tender. Collagen content of the spent layer franks was no higher than for the commercial brands. It is therefore concluded that the toughness could have been due to the nature of the myofibrillar proteins. Such toughness could be modified by tenderizing enzyme treatment of the raw material to produce varying degrees of frank softness or firmness depending on consumer preference.     

Soft-switched,high frequency resonant AC-to-DC rectifier with high power factor

A high frequency and soft-switched AC-to-DC rectifier employing a series-type resonant circuit is proposed to overcome the disadvantages of the conventional peak-rectifying circuit. Using the proposed rectifier, a high power factor and low harmonic currents are obtained in the AC line. Furthermore, several advantages such as high power density and wide output voltage range can also be available. Through simulation and experimental results, the usefulness of the proposed rectifier is verified.     

Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction

In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial‐free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material.     

Effect of preheating on the mechanical properties of tough pitch copper made from copper scraps

When hot rolled tough pitch copper is made from copper scraps, lead is intentionally or unintentionally added to the melt. The major role of this lead seems to be the removal of metallic tin by the formation of PbO–SnO₂. A continuously cast and hot rolled copper rod was preheated at temperatures between 673–1173 K for 1 h prior to cold drawing. The maximum diameter of the PbO–SnO₂, of 1–2 μm, was obtained by preheating at 873 K. This preheating temperature also produced the maximum decrease in the recrystallization temperature and the maximum electrical conductivity of the 89.4% cold drawn wire within the investigated experimental range. This can be attributed to a decrease in the dissolved impurity concentration due to the growth of PbO–SnO₂ particles at that temperature. The decrease in recrystallization temperature enhanced the room temperature multiple upset weldability. When preheated at 1173 K, Zn₂SnO₄ particles were formed, but the recrystallization temperature increased and the electrical conductivity decreased due to the dissolution of PbO–SnO₂. This revised version was published online in November 2006 with corrections to the Cover Date.