SMT production scheduling: a generalized transportation approach

A generalized transportation model is first formulated for the scheduling of Surface Mount Technology (SMT) production. Its dual form is next discussed. By specially coding the SMT scheduling problem, it is unnecessary to develop the constraint matrix for the dual. The simplex method is not applicable for this problem due to its sparse data structure. An efficient algorithm for the dual model is then developed from the idea of the revised simplex method. To illustrate the algorithm, a numeric example is presented.     

Continuous-time optimal robust servo-controller design with internal model principle

The linear quadratic design of an optimal robust servo–controller for a continuous–time control system is described. It introduces a servo–control performance measure which accommodates the internal model principle. The measure selectively discounts penalties on control effort of desirable frequencies and provides complete flexibility in the selection of weighting matrices. The proposed servo–controller uses plant state feedback, signal state feedforward and a servo–compensator for ensuring robust asymptotic command tracking and disturbance rejection. An informal alternate proof of the internal model principle in the state variable domain is presented using an operator-transformation technique. Where necessary, observers are used to complement the servo-controller. The proposed optimal robust servo–controller yields the expected superior performance in terms of response and error minimization. An illustrative example is given.     

Observer design for time-varying systems

The state estimation problem is considered for linear time–varying continuous systems with non–lexicographic–fixed observability basis. A two–stage design strategy is presented for constructing observers for this class of systems. At the first stage, by augmenting the given system with an auxiliary system, the original system is transformed to a new augmented model whose observability indices are lexicographic–fixed. A specific augmentation scheme is proposed in order to find this auxiliary system. At the second stage, a design procedure is given to construct minimum–order observers for the augmented system by utilizing the new input and output information. The canonical transformation technique is also employed to simplify the design procedure. Finally, with the help of a simple reverse transformation, solutions to the original problem arc obtained. An example is also given to illustrate the design techniques.     

Representation of dynamic output feedback control system variables via orthogonal functions

A general basis for using orthogonal functions to approximate the variables of a dynamic output feedback control system is presented. The use of an operational matrix of integration reduces the problem to a set of linear algebraic equations. The result is also useful for implementing open-loop approximation of derived closed-loop control. The flexible controller structure provides easy adaptation to feedback configurations using state, output, dynamic output or observer output, and feedback compensator. As an example, an approximation analysis of dynamic output feedback control via Fourier series is investigated.     

春之路

这个纪念方案拟建一条道路,以表达对2008年5·12四川大地震遇难者的沉痛哀悼.这条路毗邻四川省的某一河边,那里有一大片可循环利用的建筑废墟地,零星分布着小麦田.独特的场所体验由地下和地上两个项目组成.     

ECM-abrasive polishing of metals

The combined action of abrasives and electrochemical machining (ECM) results in a better surface finish than that could be achieved by using abrasives alone. From an initial roughness of R_tm 30 to 50 nm, flat carbon steel and stainless steel specimens could be finished to a roughness of R_tm 0-4 μm. The procedures in conducting the experiments and analysing the data are discussed in this paper.     

THE THERMAL FRACTURABILITY LOSS OF EDIBLE PLANT TISSUE: PATTERN AND WITHIN-SPECIES VARIATION1

The pattern of fracturability loss of 11 selected fruits and vegetables during thermal processing was studied. In general, the first-order kinetic model is adequate in describing such changes during heating of edible plant tissue before reaching equilibrium texture. However, textural changes are less predictable by the first-order kinetic model in tissues having thick cell walls (such as those derived from stems and roots) than in tissues having thin cell walls (such as those derived from fruits). For a given species (potato), the first-order model can be applied regardless of sample dimension, morphological origin of the sample, heating temperature, variety, prior storage conditions, maturity and minor agronomic variation.     

BETWEEN-SPECIES DIFFERENCES IN FRACTURABILITY LOSS: MICROSCOPIC AND CHEMICAL COMPARISON OF POTATO AND CHINESE WATERCHESTNUT1

Potato and waterchestnut tissue were used as experimental materials for comparing between-species differences in heat softening rate. Scanning electron microscope (SEM) techniques were employed to compare cellular and subcellular changes with corresponding fractur ability losses during cooking of potato and Chinese waterchestnut by four cooking methods. SEM observations strongly suggest that cell wall adhesion and its heat resistance play a major role in fracturability changes during heating. Intracellular substances such as starch and minerals may slightly alter the cell wall strength but do not substantially affect fracturability changes. In addition, differences in the gross chemical composition between species were inadequate for explaining fracturability changes of the two vegetable tissues during heating.     

BETWEEN-SPECIES DIFFERENCES IN FRACTURABILITY LOSS: COMPARISON OF THE THERMAL BEHAVIOR OF PECTIC AND CELL WALL SUBSTANCES IN POTATO AND CHINESE WATERCHESTNUT1

This study was undertaken to determine how the mode of chemical changes taking place during the cooking of two chemically similar vegetables (potato and waterchestnut) might explain the tremendous between-species differences in cooked tissue fractura bility as determined by Instron Texture Profile Analysis. Although pectin breakdown and depolymerization by heat weakens the cell wall structure, loss of cell wall physical strength does not necessarily coincide with pectin depolymerization. Potato phosphate-soluble pectin (PSP) showed a more rapid rate of depolymerization than waterchestnut PSP as proven by both chemical and gel chromatographic studies. The unique composition (e.g., neutral sugar content) of the cell wall microstructure of a given vegetable species is the major determinant of the resistance of that plant tissue to fracturability loss during cooking. Based on GLC analyses of cell wall components, cell wall models have been proposed to illustrate the possible structural differences between potato and waterchestnut tissue. It appears that the cell wall character of edible plant tissue for a given species is determined genetically.