A commercial AA2618 alloy was treated through melt spinning at rotating speeds of 20 and 40 m·s^-1. The as-melt spun ribbons were characterized by a combination of optical microscopy (OPM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The microstructural evolution of the ribbons in a continuous heating process was investigated, and the microhardness was also measured under different conditions. It was found that Al_xFeNi is prone to precipitate in AA2618 alloy due to the minimal solubility of iron and nickel. Fine Al_xFeNi particles appeared along the grain boundaries at the chilling sides of as-melt spun ribbons, and at both the grain boundaries and in the interior of grains at the free sides. On continuous heating Al_xFeNi precipitated steadily and uniformly throughout the matrix until melting. The microhardness of as-melt spun ribbons decreased significantly from the chilling surfaces to free surfaces. Precipitation of Al_xFeNi lowered the hardness of the alloy.

Pneumatic driven system has been widely used in industrial automation mainly for relatively simply tasks with open-loop control. With regard to closed-loop controlled axes in robotics, servo-electric driven systems have been dominant up to now. This paper introduces a new closed-loop control servo-pneumatic system that can do continuous positioning. The mathematical model of the servo-pneumatic system was developed accurately through analysis of the flow characteristics of the proportional flow valve and the friction of the cylinder. The optimum control strategy with friction compensation is presented in this paper. Experiments demonstrate that the servo-pneumatic system has excellent tracking characteristics and can rival the expensive servo-electric system in many areas of industrial control.

Our analysis of the KQML(Knowledge Query and Manipulation Language) model yielded some conclusions on the knowledge level of communication in agent-oriented program. First, the agent state and transition model were given for analyzing the necessary conditions for interaction with the synchronal and asynchronous KQML model respectively. Second, we analyzed the deadlock and starvation problems in the KQML communication, and gave the solution. At last, the advantages and disadvantages of the synchronal and asynchronous KQML model were listed respectively, and the choosing principle was given.

Robust tracking controller for a class of uncertain nonlinear dynamical systems, which are linearizable by input-output feedback with matching uncertainties, was investigated. In this study, uniform ultimate bound or uniformly asymptotic stability of tracking errors were obtained by different choice of the control gain. A simulation to determine the effectiveness of the proposed approach showed that the control performance was better than that of VSC (Variable Structure Control).

This paper presents the topology optimization design of structures composed of plane stress elements. The authors\' proposed method of topology optimization by virtual laminated element is based on the Evolutionary Structural Optimization (ESO) method of linear elasticity, but dose not require formation of as many elements as the conventional ESO method. The presented method has the important feature of reforming the stiffness matrix in generating optimum topology. Calculation results showed that this algorithm is simple and effective and can be applied for topology optimization of structures.

In this study, Fabrikant (1989, 1991)\'s new results in potential theory were used to obtain the exact and complete solution for the problem of a penny-shaped crack in an infinite transversely isotropic piezoelectric body subjected to antisymmetric point loads (point charges and normal point forces); then the complete solution for the problem of one-sided loading of a penny-shaped crack was obtained by the superposition of the symmetric loading solution in Chen and Shioya (1999) and the antisymmetric one presented here; and then the reciprocity theorem of piezoelectric media was used to deal with the problem of interaction between arbitrarily located point forces and a point charge with a penny-shaped crack and obtained the exact expressions of the crack faces\' normal displacement in terms of elementary functions and some non-singular integrals; and finally obtained the normal displacement of the positive and negative faces of the crack under many loading cases as shown in figures for an infinite PZT-4 piezoelectric ceramic body weakened by a penny-shaped crack.

As Huston\'s form of Kane\'s equation cannot be easily applied to large deployable structures, what is needed is further development of Kane\'s equation as described in this paper. Fully-Cartesian-coordinate (FCC) method uses Cartesian coordinates of points and Cartesian components of unitary vectors as generalized coordinates to describe three-dimension mechanisms. This FCC method avoids the need to consider angular coordinates and the resulting solution is just the space position of the structures. The FCC form of Kane\'s equation derived in this study is suitable for solution by computer method and is a good base for further simulation research. A numerical example showed that it is effective.

In piezoelectric problems, the form of the general solution is dependent on the eigenvalues of the material. The singular stress field and electrical displacement field near the interface edge were deduced in this study. The results showed that the stress field and the electrical displacement field have the same singularity; and that the singularity depends not only on the mechanical properties and shape of the interface edge, but also on the piezoelectric properties of the composite material.

In this paper, we consider the Timoshenko equation of a nonuniform beam,with clamped boundary condition at one end and with feedback controls at the other end. It is proved that the system is backward wellposedness when the feedback controls are weak enough.

The author provides a new discretization method-the finite volume method(FVM). For the Stokes equation the velocity space is approximated by the nonconforming linear element based on the dual partition and the pressure by the piecewise constant based on the primal triangulation. Under the suitable smoothness of the solution, the optimal convergence rate O(h) is obtained, where h denotes the parameter of the space discretization.

A novel topology for ripple-free input current circuit is put forward in the paper. Compared to traditional EMI(electromagnetic interference) filter consisting of choke and capacitor, the ripple-free topology can reduce the converter\'s ripple current with the use of smaller component. The new ripple-free topology proposed in this paper does not need elaborate adjustment of the coupling coefficient as required by conventional ripple-free techniques, and is ripple voltage cancellation or isolation mode, which can attenuate the ripple further if the line impedance is considered. The theoretical prediction is confirmed by experimental results.

A new type microgap surge absorber fabricated by only semiconductor technique has in it a special structure silicon chip which forms microgaps for gas discharge with electrodes, and has advantages such as small size, low cost, suitability for mass production besides the desirable characteristics that common microgap surge absorbers have. Applications of this absorber in communication facilities are discussed.

This paper presents a method to determine driving resistance with rebound of pile-top during pile driving. The soil around the pile shaft is assumed to be rigid-plastic, while that under the pile-tip is assumed to be ideally elastoplastic. The driving force acting on the pile-top is simplified to a triangular impact force. The kinematic equation of the pile-tip is established. From the one-dimensional wave equation, the movements of the pile-tip and pile-top are determined. The rebound at the pile-top can be written in a very concise form. It is shown that the shaft resistance makes the rebound at the pile-top decrease. In particular, when the pile is very long or the soil around the pile is very stiff, the decrease is very obvious.

This paper presents a theoretical model and new idea for designing granular fill oil-tanks foundation. The finite difference method was used to analyze the influence of the oil-tanks radius, the modulus, and thickness of the granular fill on the maximum and differential settlement of a granular fill foundation of oil-tanks. Comparison of the modelled results with those of traditional method and observation showed that the new method could be used efficiently in practice.

A Model S195 (8.8 kW) single cylinder was used in this study to determine the effect of four operational parameters, i.e. intake valve close angle, exhaust valve open angle, fuel delivery angle and fuel injection pressure on noise. Single factor and multi-factor quadratic regressive orthogonal methods were adopted in the experiments to find the relationship between the four parameters and noise. By means of optimization technique, the optimum operational parameters for two working conditions of the engine were selected and the test results showed that optimum adjustment could reduce noise by 2-4 dB.

A new site-specific nutrient management approach was developed to break the apparent attainable yield barrier of 6 t·ha^-1 in the double rice cropping system of Zhejiang. On-farm experiments involving 21 rice-growing farmer families and NPK long-term experiments commenced in 1997 in the central part of Zhejiang Province to assess the status of soil fertility and productivity under intensive rice-rice cropping. A new site-specific nutrient management (SSNM) approach has been developed for this studied area. Field-specific fertilizer recommendations are calculated considering indigenous nutrient supply, reasonable grain yield targets and corresponding nutrient demand, nutrient balance and nutrient use efficiency, as well as socio-economic factors. The agronomic performance of SSNM was tested against the farmer\'s fertilizer practice (FFP) in four 1998-1999 cropping seasons. Across seasons and years, SSNM consistently increased plant nutrient uptake, grain yield and profit by about 10%-15% compared to the FFP. Yield levels of 7.5 t·ha^-1 or more seem achievable and sustainable through introduction of SSNM and improved extension services in Zhejiang Province.

Cheese slurries,made from fresh Swiss cheese curd, were treated at 345 or 550 MPa for 10 or 30 minutes in an isostatic press at 25 °C. The slurries were ripened at 30 °C for 0, 3 and 5 days. The growths of coliforms, yeasts and molds, starter bacteria (Lactococci and Streptococci), non-starter lactic acid bacteria (Lactobacilli), and presumptive coagulase-positive Staphylococcus were determined. An electronic nose was used to evaluate aroma development of the cheese slurries. Commercial Swiss cheeses with different ages were used as aroma references.The degree of inactivation of organisms was found to be a function of pressure intensity, exposure time, type of organism, and cheese slurry pH. In general, slurries treated at a higher pressure and with a longer exposure time showed a greater reduction in numbers and had less out-growth of organisms during ripening. Coliforms, yeasts and molds were completely inactivated at the pressures and time used. Starter bacteria appeared to be more resistant to being inactivated by high pressure treatment and had a greater out-growth rate than Lactobacilli and Staphylococci.Based on canonical analysis, nineteen samples for each batch were assigned to three groups. In general, higher intensity of pressure or longer exposure time caused less aroma development in the cheese slurries. When the cheese curd was incubated overnight prior to making the cheese slurries, stronger slurries with stronger aroma were observed. This study provided an explanation of the relative importance of relationships among high pressure treatment, starter bacteria, and aroma development during accelerated ripening.

Water extraction of soybean oil was studied to find the optimal conditions for recovery of oil pre-enriched protein and for aqueous extraction of soybean oil. Orthogonal tests were employed in the procedures of oil pre-enrichment and aqueous extraction. Soybeans were crushed to pass a 40 mesh sieve, soaked under the optimum conditions (solid/water=1/5(w/v), 40 °C, pH 10, 3 h) and water-ground to 100 mesh, stirred in 65 °C water for 20 min, and centrifuged at 1400 g to separate oil pre-enriched protein. The protein yield was 17.8 g from 100 g soybeans, which contained 62.8% oil. The oil yield was 69.0%. Optimum conditions for the aqueous extraction procedure were: solid-to-water ratio 1:2, pH 9.0, time 30 min, stirring in boiling water bath, stationary time 10 min, centrifuge at 3600 g for 10 min. Experimental values showed that the oil yield after aqueous extraction from oil pre-enriched protein reached 88.3%, so the total oil extraction rate was 60.8%.

It is well known that the most prominent characteristic of emergency systems is the limit of time. A scheme must be made in much shorter time, and the retrieval vehicle should be able to reach the emergency site in the earliest time according to the proposed scheme so that the emergency event is dealt with as early as possible. This paper deals with multi-depot problems in two cases: (1) When the duration or time needed by the retrieval vehicle arriving at the emergency site from each depot is a non-negative real number, a single-objective (or min-max) and a two-phase problems on the earliest-emergency-activity-start-time (EEAST) are considered. (2) When the duration is regarded as an interval number, we consider the problem of finding an optimal scheme meeting a given deadline t with maximum possibility (or truth value).

This paper on the migration of the surplus farm labor during the economic transition of China, focuses on a case study of Zhejiang, China\'s eastern coastal province, with 45 million population and located in relatively developed area since the reform in 1978. The background and mechanism of Chinese surplus farm labor migration are discussed briefly in the first section. Detailed analysis and development of this topic are based on the Zhejiang case, and consists of two parts: a review of the migration history of surplus agricultural labor in Zhejiang since the 1978 reform; and further analysis and key points are given in the second part. The third sector focuses on challenges and recommendation of policies.

The current exchange rate regime of China is just like the US dollar-pegged exchange rate regime, which weakens the effectiveness of monetary policy but increases the effectiveness of fiscal policy. Since the scope of implementing the fiscal policy is quite narrow, it is necessary to promote the effectiveness of monetary policy by enlarging the elasticity of the RMB exchange rate regime so as to stimulate the rapid development of the Chinese economy effectively.

Three factors contributing to the increase of cocoon output are: the cocoon output per box, the area of mulberry field, and the egg amount raised per unit area of mulberry field. These three main factors were analyzed based on the statistical data on cocoon output collected in Zhejiang Province from 1963 to 1998, and the proportions of the contribution to the increase of cocoon output were calculated by the factorization method. The results showed that the importance of the factors in increasing cocoon output was in the order: egg amount raised per unit area of mulberry field > cocoon output per box > area of mulberry field.

Second language acquisition (SLA) has been one of the central topics in cognitive science. Various theories regarding the SLA process have evolved and have been a subject of debate over the years. With a critical review of the competing theories of cognition and language development, this paper examines the differences between L1 and L2 acquisitional processes and then proposes a model of SLA process from a cognitive information-processing perspective. The pedagogic implications of this model are also discussed.