An effective coding approach for multiobjective integrated resource selection and operation sequences problem

In this paper, we consider an integrated Resource Selection and Operation Sequences (iRS/OS) problem in Intelligent Manufacturing System (IMS). Several kinds of objectives are taken into account, in which the makespan for orders should be minimized; workloads among machine tools should be balanced; the total transition times between machines in a local plant should also be minimized. To solve this multiobjective iRS/OS model, a new two vectors-based coding approach has been proposed to improve the efficiency by designing a chromosome containing two kinds of information, i.e., operation sequences and machine selection. Using such kind of chromosome, we adapt multistage operation-based Genetic Algorithm (moGA) to find the Pareto optimal solutions. Moreover a special technique called left-shift hillclimber has been used as one kind of local search to improve the efficiency of our algorithm. Finally, the experimental results of several iRS/OS problems indicate that our proposed approach can obtain best solutions. Further more comparing with previous approaches, moGA performs better for finding Pareto solutions. Received: May 2005/Accepted: December 2005     

Multistage Zeolite Drying for Energy-Efficient Drying

This work discusses the potential of three multistage zeolite drying systems (counter-, co-, and cross-current) with a varying number of stages. The evaluation showed that for 2-4 stages with heat recovery the efficiency of the systems ranges between 80 and 90%. Additionally, by introducing a compressor, the latent heat in the exhaust air from the regenerator is recovered and used to heat the inlet air for an additional drying stage. As a result, for the counter-current drying system and compressor pressure 1.5-2 bar, a maximum energy efficiency of 120% is achieved, which results in halving the energy consumption compared to conventional drying systems.     

Helicoseir as Shape of a Rotating String (I): 2D Theory and Simulation Using ANCF

A physically simple but mathematically cumbersome problem of rotating heavy string with one fixed top point was studied. A nonlinear equation of its two-dimensional shapes of relative equilibrium was obtained and solved numerically. A linear case of small displacements was analyzed in terms of Bessel functions. The qualitative and quantitative behavior of the problem is discussed with the help of a bifurcation diagram. Dynamics of the two-dimensional model near the equilibrium positions were studied with the help of a simulation using the absolute nodal coordinate formulation (ANCF); the equilibriums were found to be instable. The reason for instability is explained using a variational principle. The outlines for further full three-dimensional analysis are briefly proposed in this paper, and the full derivation will be explained in the next paper.     

On the non-blocking conditions of self-routeing multistage interconnection networks

This paper studies the non-blocking conditions of a generic N × N multistage interconnection network, such as an omega network or an n-cube network, in which only one path connects any inlet to each outlet and different I/O paths can share interstage links. It is widely known that any of these networks is non-blocking for a compact and monotone pattern of k ≤ N I/O paths. Recently it has become very important to show the network non-blocking property for permutation sets, wider than the compact and monotone, which are usually encountered in broadband ATM networks. By using a new approach based on the concept of distance between I/O paths, we show here that these networks are non-blocking for a set of I/O paths obtained by shifting cyclically the inlets of a compact and monotone pattern of I/O paths by an arbitrary number of steps.     

Symmetry properties and bifurcation analysis of a class of periodically forced chemical reactors

In this work, we discuss how periodic forcing may induce symmetry properties into mathematical models of chemical reactors. We define a class of reactors subjected to discontinuous periodic forcing, and show that all the reactors belonging to this class have spatio-temporal symmetry. This symmetry and its influence on the possible bifurcation scenarios are discussed. The bifurcation analysis is carried out with suitable discrete systems that exploit a property of the Poincaré map. In fact, it is shown that the spatio-temporal symmetry induced by the forcing makes the Poincaré map of the continuous system an iterate of another map. On this basis, a technique to implement parameter continuation methods is proposed. With such a technique, it is also possible to characterize symmetric and nonsymmetric regimes and unstable limit sets otherwise undetected with “bruteforce” approaches. Examples for reverseflow reactors and networks of n-reactors with periodically switched feed and discharge positions are presented.     

GRAPHICAL SOLUTION OF MULTISTAGE FLUIDIZED BED HEAT EXCHANGER

The design of multistage fluidized beds for heat exchange necessitates the solution of the mass and energy balance equations combined with the equilibrium relations for each stage. This paper presents a novel way of applying well known methodology to a different technology, one where it has not been widely applied.

In the present work a McCabe-Thiele type of graphical approach is presented for both counter-current and cross-current contacting multiple fluidized beds. The necessary equations for a multistage calciner are developed and the application of the proposed method is demonstrated. Generalized fluidized bed efficiency for counter-current and cross-current multiple fluidized bed is presented.     

三自由度模型覆冰输电导线舞动的数值仿真分析

基于考虑输电导线垂直、水平和扭转振动耦合的3自由度模型,利用数值方法,针对系统参数和环境参数对临界风速的影响以及可能的复杂舞动模式进行了分析.给出了覆冰厚度、初始覆冰角度、来流密度、导线初始张力、单位长度质量和横向阻尼比对临界风速的影响曲线.在讨论舞动可能出现的复杂运动时,发现随风速的变化,由于周期运动的分岔可导致概周期运动和混沌等复杂运动形式.     

医院内抗生素耐药性传染的稳定性与Hopf分支

研究了医院内感染的带有非线性发生率的抗生素耐药性的时滞传染病模型的稳定性.确定了疾病暴发的阈值R0,运用Lasalle-Liapunov不变集原理和Routh-Hurwitz判据得到了,当R01时无病平衡点是全局稳定的;当R01时,地方病平衡点存在且唯一,对于任意的τ≠0,总能得到在地方病平衡点处的Hopf分支存在的条件.最后通过数值模拟验证了结论的正确性.     

Dynamical responses for a vertical vibration model of a four-roller cold rolling mill under combined stochastic and harmonic excitations

Considering that random fluctuations can affect the rolling process of cold rolling mills, leading to abnormal cold mill performance and defects in the rolled product. Therefore, it is crucial to study the influence of random fluctuations on the system of cold rolling mills. In this paper, taking a model of the vertical vibration of a four-roller cold rolling mill under harmonic excitation as a prototype class for a real system, the effects of random fluctuations on the system response are analyzed. Firstly, based on the deterministic vertical vibration model of a four-roller cold rolling mill under harmonic excitation, a stochastic vertical vibration model of a four-roller cold rolling mill with random fluctuation as Gaussian white noise is introduced. Subsequently, the vertical vibration model of a four-roller rolling mill is theoretically analyzed by the averaging method and the stochastic averaging method, respectively. The effectiveness of the proposed theoretical method is verified by numerical simulation results, and the influences of harmonic excitation and random excitation on the system response are also investigated in detail. Finally, the results show that the noise induces the occurrence of stochastic transitions and bifurcations, and the steady-state probability density function and time history diagrams are given to further explain the existence of these dynamic phenomena. The related research can provide theoretical guidance for the realization of vibration control and reliability design in the four-roller cold rolling mill system.     

Integration of a three-stage expander into a CO2 refrigeration system

The inclusion of an expander with work recovery provides two advantages for transcritical CO₂ refrigeration cycles: the COP is improved and the exhaust pressure of the main compressor is lowered. Several designs of expanders have been proposed for this application and some prototypes have been tested already. In our laboratory a three-stage expander has been developed, which replaces the throttle valve of the normal refrigeration cycle and expands into the two-phase region. For optimum integration into the overall system it is proposed to install a vapour-liquid separator between the second and third stage of expansion. The vapour is guided back to the third expander stage whereas the liquid is supplied to the cooling stations via thermostatic or electronic expansion valves.