Genetic algorithm approach to a production ordering problem in an assembly process with constant use of parts

An optimal production scheduling problem for an assembly process with buffers at the input and output sides of a machine is dealt with. The problem has two kinds of constraints. One constraint is that the buffers' capacity is limited. The other constraint is that the cycle time of the worker is constant without waiting time. An optimal production ordering is determined, subject to these constraints, in such a way that the rate of use of parts to produce each product should be as constant as possible. A procedure to apply the genetic algorithm to this problem is shown. The operations of reproduction, crossover and mutation are presented. It is observed from numerical results that the genetic algorithm gives a better suboptimal solution than the greedy method.     

A simulation study on autonomous decentralized mechanism in fish behaviour model

The behaviour of a fish school is considered an interesting phenomenon because a fish school behaves differently in various situations. The paper considers a fish school as an autonomous decentralized system and constructs a mathematical model for the autonomous decentralized mechanism. Simulation results show that, by varying the quantity of information exchange among members in school, the present model describes fish behaviour not only for a school with fixed configuration but also for that with variable form. Furthermore, a remarkable difference in fish trajectory is found between the two schools.     

Historical Factors and Recent Developments in Wastewater Treatment Management in Japan

Japan has experienced serious water pollution problems, such as Minamata Disease (mercury poisoning) in the 1960s. Since then, comprehensive countermeasures have been implemented including establishment of a legislative framework and environmental water quality (EWQ) standards, enforcement of EWQ standards on dischargers, encouragement in the development of sewerage systems, research and technology development, and wastewater reclamation and reuse. This paper reviews the recent developments in wastewater management in this social context in Japan.     

Determination of eigenvalues in Marshall's model reduction

This paper is concerned with the problem of determining eigenvalues, retained in Marshall's reduced order model, which have the largest effect on the retaining state vector or give the best approximate reduced system in the sense of ISE criterion. The main objective is to show that the usual choice of eigenvalues in Marshall's model reduction technique (decomposition of eigenvalues into fast modes and slow modes) does not necessarily give a well approximated reduced order model. Here the measure of approximation is defined and calculated by means of ISE criterion. The effectiveness of this method is explained by two illustrative examples.     

A method for decomposing mixed-integer linear programs with staircase structure

An algorithm is presented for solving mixed-integer linear programs with a staircase structure. The basic idea of the algorithm is to decompose the original problem into a series form of small-scale mixed-integer problems. For each problem decomposed, the solution is obtained by the conventional branch-and-bound method. In this algorithm the feasibility of the solution is always assured, but in order to save computation time the optimality condition is checked restrictedly for the solution obtained. The difference between the optimal objective value and the objective value obtained can be estimated. By examining numerical results, it is observed that the algorithm is efficient, requiring less computation time than other methods.     

Fatigue life prediction of composites under two-stage loading

In order to predict the fatigue life under two-stage loading by formulating a cumulative fatigue damage rule for composite materials, the fatigue process in SiC–Al and glass-fibre reinforced plastics were investigated. A microcrack occurred within the composites which resulted in cumulative fatigue damage that increased linearly with the number of cycles. The mechanical conditions of damage growth and failure were determined by characterizing the microdamage governing the fatigue. The ultimate failure is shown to occur when the product of the stress amplitude ratio and microdamage density is beyond a critical value and an expression for the remaining fatigue life is derived. This revised version was published online in November 2006 with corrections to the Cover Date.     

Gel Forming Characteristics of Frozen Surimi from Chum Salmon in the Presence of Protease Inhibitors

When salted surimi paste of chum salmon was incubated at 20–60°C, a marked loss of the breaking strength of heat-induced gel occurred simultaneously with breakdown of myosin heavy chain, but this was effectively suppressed by addition of cysteine protease inhibitors or bovine plasma powder. In the presence of protease inhibitor, the surimi gels were formed at relatively low temperatures showing highest gel strength at incubations of 50 and 60°C. Chum salmon surimi showed no evidence of suwari and no myosin heavy chain cross-linking.     

Electron Paramagnetic Resonance in R2O-Al2O3−SiO2 Glass Systems

Systematic detection of an EPR signal was conducted for three alkali oxide-Al₂O₃−SiO₂ glass systems. Observed EPR spectra, having a main line with g=2.03 and a broad and anisotropic shape, are attributed to the unsaturated bridging oxygen bond resulting from the breakup of the SiO₂ random network. This signal appears in the area AValkali atom ratio >1 for the Na₂0 and K₂O systems, indicating that the collapse of the Al 4-coordinated structure begins at an equimolar ratio when alumina is substituted for the alkali oxide, whereas somewhat different behavior was observed for the Li₂O system.     

High Density Plasma Heating by EC-Waves Injected from the High-Field Side for Mode Conversion to Electron Bernstein Waves in LHD

To realize an excitation of electron Bernstein waves (EBW) via mode conversion from X-mode waves injected from the high magnetic field side (HFS), new inner-vessel mirrors were installed close to a helical coil in the large helical device (LHD). 77 GHz electron cyclotron (EC) wave beams injected from an existing EC-wave injection system toward the new mirror are reflected on the mirror so that the beams are injected to plasmas from HFS. Evident increases in the electron temperature at the plasma core region and the plasma stored energy were observed by the HFS beam injection to the plasmas with the line-average electron density of 7.5×10 19 m 3 , which is slightly higher than the plasma cut-off density of 77 GHz EC-waves, 7.35×10 19 m 3 . The heating efficiency evaluated from the changes in the time derivative of the plasma stored energy reached ～70%. Although so far it is not clear which is the main cause of the heating effect, the mode-converted EBW or the X-mode wave itself injected from the HFS, an effective heating of high-density plasma over the plasma cut-off of EC-wave was successfully demonstrated.     

Measurement of the Electron Bernstein Wave Emission with One of the Power Transmission Lines for ECH in LHD

Possibility of the measurement of radiated waves derived from the thermally emitted electron Bernstein wave （EBW） is numerically investigated based on the assum...