A genetic algorithm for the optimal sequential partitioning problem

The optimal sequential problem is defined as the problem of finding the minimum cost partition of the nodes of a directed acyclic graph into subsets of a given size, subject to the constraint that the precedence relationships among the elements are satisfied. A heuristic algorithm based on tabu search has been proposed for this problem [2]. However, there is a tendency for the solutions obtained by tabu search to become trapped in bad local optima in parallel graphs with random edge costs. In this paper we present a genetic algorithm for the optimal sequential partitioning problem. We develop an effective two‐point partial order crossover satisfying sequential conditions, which preserve better blocks that have a larger sum of edge costs. In this crossover we introduce the roulette selection method to escape local optima. We also assess the effectiveness of the algorithm. The results show that this proposed algorithm outperforms any other algorithm using tabu search in terms of solution quality. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 43–51, 2001     

Solute atmosphere around an edge dislocation in Al-based ternary alloys

We evaluated the solute atmosphere around a moving dislocation and the dragging stress due to the atmosphere in binary and ternary Al-based alloys in terms of a chemical potential gradient by modifying the method proposed by Yoshinaga et al. In ternary alloys, we analyzed formation of the complex solute atmosphere around a straight edge dislocation and the dragging stress in terms of a misfit parameter of a solute element (positive or negative) and an interaction parameter between solute elements (attractive or repulsive).     

Thermal decomposition of aluminium hydroxycarboxylates—lactate,citrate and tartrate

The thermal transformation of anhydrous alumina obtained by the decomposition of the lactate, citrate and tartrate of aluminium has been examined by thermal analysis(TGA and DTA), infrared spectrophotometry and X-ray diffraction study. It is found that under an atmosphere of air the thermal decomposition of aluminium hydroxycarboxylates to anhydrous amorphous alumina, which transforms to α-alumina via γ-, δ- and θ-aluminas, proceeds as follows for Al[CH₃CH(OH)COO]₃, the decomposition of skeleton and the combustion of its decomposition products; for Al[CH₂C(OH)CH₂(COO)₃] and Al₂{[CH(OH)COO]₂}₃, dehydroxylation, decomposition of skeleton and the combustion of its decomposition products.     

Extraction of uranium (VI) and thorium from hydrochloric acid solutions by tri-n-butyl phosphate

The partitions of uranium (vi) and thorium between hydrochloric acid solutions and solutions of tri-n-butyl phosphate (TBP) in benzene or kerosene have been investigated at different concentrations of hydrochloric acid and solvent, and at different temperatures. An infra-red spectral study has also been made of the organic solutions obtained in the extraction of uranium. The effect of organic solvent on the extractions has also been examined.     

Thermal decomposition of nickel hydroxide

The thermal decomposition of nickel hydroxides prepared from aqueous nickel chloride solution on addition of alkali under various conditions has been examined by thermogravimetry, differential thermal analysis, X-ray diffraction study, visible and infrared spectrophotometry, magnetic susceptibility measurement and electron spin resonance spectroscopy. As a result, it is concluded that the thermal decomposition of nickel hydroxide proceeds in the following sequence:      

Control of biped walking robot for human living environment

This paper introduces biped robot adaptation to human living environment from viewpoints of battery operation time extension and environmental recognition. These issues are important when robots actually work at home. First, in order to extend battery operation time, we propose energy-saving bipedal locomotion gait. The problem is formulated as an optimal control problem, which is conventionally hard to solve when a target system is complicated. In this paper, partial derivatives appeared in optimal control problem are implicitly represented by using automatic differentiation technique. This approach enables complicated optimal control problem solvable. In combination with receding horizon control, its computation cost is also reduced. Second, we introduce the biped walk tracking based on the camera image mounted on the walking robot, and the visual servoing by the posture change for the purpose of the target image tracking in the camera frame. We propose a new control law to track the rotated target object using the characteristic of the walking, which considered the interference between translational motion and rotational motion. The decoupling is realized by simulations and experiments. As a result, the walking robot tracked the translated and rotated target object without a practical issue. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Formation of hexachlorobenzene from dusts of an electric arc furnace used in steelmaking: effect of temperature and dust composition

A certain amount of hexachlorobenzene (HCB), designated a persistent organic pollutant (POP) by the Stockholm Convention, is emitted from an electric arc furnace (EAF) used in the steelmaking process. To understand the formation and decomposition behaviors of HCB during the treatment of waste gases from an EAF, characterization of dust samples from EAFs in different plants was conducted. Dusts 1 and 2 were bag filter dusts collected from a common steel plant and a special steel plant, respectively. The initial concentrations of HCB in dusts 1 and 2 were 62 and < 0.1 ng/g of dust, respectively. Then a series of heating experiments was carried out with these dust samples under various conditions. The formation of HCB from both dusts was not significant under an Ar atmosphere, although the amount of formation from dust 1 slightly increased with an increase in the holding temperature. Under an Ar--20% O2 atmosphere, however, a remarkable amount of HCB formed from dust 1 above 573 K. A certain amount of HCB was also formed from dust 2, even though the initial concentration of HCB was very low. Moreover, the coexistence of metallic compounds such as CuCl2 had a significant accelerating effect on the formation of HCB.     

Reduced‐order method for mathematical modeling of multiphase dc‐dc converter

A multiphase dc‐dc converter is effective for miniaturization and achieving high‐power density in a switching power supply. However, its mathematical modeling becomes complex as the phase number of the circuit increases. This study proposes a new modeling method to derive a reduced‐order method in a simple manner. The frequency characteristics of the reduced‐order model are fit to those of the original mathematical model of the multiphase dc‐dc converter. Therefore, the efficacy of the proposed method is validated.