Solution to the topology optimization problem using a time-evolution equation

This article describes a numerical solution to the topology optimization problem using a time-evolution equation. The design variables of the topology optimization problem are defined as a mathematical scalar function in a given design domain. The scalar function is projected to the normalized density function. The adjoint variable method is used to determine the gradient defined as the ratio of the variation of the objective function or constraint function to the variation of the design variable. The variation of design variables is obtained using the solution of the time-evolution equation in which the source term and Neumann boundary condition are given as a negative gradient. The distribution of design variables yielding an optimal solution is obtained by time integration of the solution of the time-evolution equation. By solving the topology optimization problem using the proposed method, it is shown that the objective function decreases when the constraints are satisfied. Furthermore, we apply the proposed method to the thermal resistance minimization problem under the total volume constraint and the mean compliance minimization problem under the total volume constraint.     

Cooperative control of multiple neural networks for an indoor blimp robot

We report on the cooperative control of multiple neural networks for an indoor blimp robot. In our research group, the indoor blimp robot has been studied to achieve various flying robot applications. The objective of this article is to propose a robust controller that can adapt to mechanical accidents such as the breakdown of propellers. In our proposed method, each propeller thrust is independently calculated by a small neural network. We confirm the advantage of the proposed method against the control by a single large neural network. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

波导全息存储器的多层读出特性

研究了多层波导全息存储器的读出特性和读出层的选择方法。通过读出光的位置重合,可读出各个记录层所记录的信息,而不受其他层的影响。而且,通过分析波导射出端的强度图形,可判断读出光和光波导的耦合状态。还研究了利用射出光强度的耦合状态判定法。     

Producing titanium by reducing TiCl<Subscript>2</Subscript>-MgCl<Subscript>2</Subscript> mixed salt with magnesium in the molten state

In the Kroll process for titanium sponge metal production, TiCl₄ gas is introduced and reacted with molten magnesium metal via a gas-liquid reduction reaction. The magnesium reduction reaction of the mixed salt of TiCl₂-MgCl₂ via a liquid-liquid reaction has been investigated and the results are reported in this article. First, the molten mixed salt was synthesized through chlorination reaction of solid titanium sponge placed in molten MgCl₂ salt, while TiCl₄ gas was bubbled at around 1,173K. Then, the TiCl₂-MgCl₂ was reacted with molten magnesium at similar temperatures. This proposed magnesium reduction reaction of the TiCl₂-MgCl₂ in the molten state may be more efficient, easier to control, and suitable for realizing continuous titanium production. For more information, contact Akio Fuwa, Waseda University, Department of Materials Science and Engineering, Faculty of Science and Engineering, Okubo 3-4-1, Shinjuku-ku, Tokyo, Japan 169-8555; +81-3-5286-3313; fax +81-3-5286-3488; e-mail akiofuwa@waseda.jp.     

High Speed 3D Milling by Dry EDM

This paper describes the high speed EDM milling of 3D cavities using gas as the working fluid. In this new process, the molten workpiece material is removed and flushed out of the working gap with the help of high-pressure gas flow. The advantages or this technique are the remarkably small tool electrode wear and the significantly high material removal rate especially when oxygen gas is used due to the extremely strong oxidation of steel workpieces. Experiments showed that the material removal rate increases dramatically when the discharge power density on the wonting surface exceeds a certain threshold due to thermally activated chemical reaction between the gas and workpiece material. The maximum removal rate obtained was almost equal to that of high speed milling of quenched steel by a milling machine. The machining accuracy was considerably better when the gas was sucked through the pipe electrode than Jetted.     

Low-valent ruthenium and iridium hydride complexes as alternatives to Lewis acid and base catalysts

The discovery of a new chemical reaction often leads to new applications and new chemical principles. Low-valent ruthenium and iridium hydride complexes are highly useful redox Lewis acid and base catalysts. Nitriles are activated by these catalysts and undergo reactions with either nucleophiles or electrophiles under neutral conditions. Hydration of nitriles, esterification of nitriles with alcohols, and amidation of nitriles with amines can be performed catalytically together with formation of ammonia. The catalytic reactions of pronucleophiles such as nitriles and carbonyl compounds with electrophiles such as alkenes, alkynes, carbonyl compounds, imines, and nitriles take place generally.     

Orientation of bacteriorhodopsin in non-aqueous polymer membrane

Summary Electric field orientation of bacteriorhodopsin (BRp) in the form of purple membrane (PM) in synthetic polymer membranes made from poly(hydroxy-methyl methacrylate) or photo-crosslinkable propyleneoxide-based prepolymer was achieved by combining once-desalted and liophilized PM sample and ethylene glycol as a dilutant, which was detected by an increase in photoelectric current or membrane potential, respectively.We gratefully acknowledge the kind advice and helpful discussion of Professor Fumio Tokunaga and Dr. Tatsuro Iwasa (Tohoku University).     

Inter-laboratory validation studies of analytical method for determination of chloramphenicol in royal jelly

Inter-laboratory validation studies were conducted in 6 laboratories to validate the analytical method for determination of chloramphenicol in royal jelly. Chloramphenicol spiked at the levels of 0.1 and 0.5 ppm was analyzed. Mean recoveries were 89 and 89%, reproducibility relative standard deviations (RSD(R)) were 10.5 and 6.8%, HORRAT(R) values were 0.5 and 0.4. Samples containing residues at the levels of 0.25 and 0.80 ppm were analyzed. Mean recoveries were 89 and 84%, RSD(R) were 9.8 and 12.3%, and HORRAT(R) values were 0.5 and 0.7. The determination limit was 0.05 ppm. These results show that this method has good performance.     

A study on phenoxy-resin esters of cinnamylideneacetic acid and its derivatives

Photocrosslinkable polymers were prepared from phenoxy resin which was photoactivated by esterifying cinnamylideneacetic acid, α-cyanocinnamylideneacetic acid or cinnamylidenepyruvic acid. Relative sensitivities and spectral sensitivities of these polymers were determined by comparing with the phenoxy resin ester of cinnamic acid. It was found that the polymer which was photo-activated with cinnamylidenepyruvic acid had the highest photosensitivity and its spectral sensitivity extended up to 500 nm without the aid of any additional sensitizing dye. The mechanism of the photocrosslinking of these polymers was also considered.