Recently, plastic products have been increasing. However, the final disposal sites of garbage are insufficient. Therefore, the material has to be developing that solves the problems. This paper describes the mechanical properties of press-molded products using short bamboo fiber bundles. Bamboo fibers can be molded such as plastic by hot pressing. In other words, it will reduce the effects of the environment that bamboo products replace the some plastic products. The tensile strength of the short bamboo fiber products increased with increasing molding temperature up to 140°C and decreased thereafter. The composites possessed tensile strength and Vickers hardness of 39 MPa and HV45, respectively.

View full abstract

A parametric transformer using the parametric oscillation phenomena offers numerous attractive features which are not found in conventional transformer,such as overload protection,noise filtering function, constant voltage regulation,and so on. However,the complex operating mechanism of the transformer has not been solved yet because of the nonlinearity of magnetization characteristics. The basic operating equation for the transformer can be represented using a Mathieu differential equation. In our study,we noticed a solution of the Mathieu equation represented stable state or unstable state of the parametric oscillation. If this equation can be solved, the optimum design of the planar parametric transformer can be easier than before. In this paper, the Mathieu equation is analyzed by using MATLAB of numerical analysis software (The MathWorks, Inc. Software).

View full abstract

It has been suggested that the pathogenesis of aneurysm in the thoracic aorta may be related to the shape of the aortic arch. In this study,we parametrically constructed computational models of human thoracic aortas based on the geometrical parameters which has been measured from normal subjects and aneurysm patients, and carried out computational fluid dynamics for the blood flow in those models. Our results demonstrate that general wall shear stress (WSS)distributes in a way that regions with relatively high WSS are localized at similar locations consistently among all the models,regardless of whether they are from normal or aneurysm subjects. However, it was found that the peak WSS values within such localized regions tended to be higher in the models from aneurysm subjects. These results imply that such localized regions with relatively high WSS may be candidate sites susceptible to aneurysms because of the focal nature of the aneurysm. Furthermore,it was suggested that the higher WSS at the sites in the aneurysm cases may enhance the possibility for aneurysms.

View full abstract

The transesterification reactions of olive oil with methanol in supercritical water were conducted by means of batch type bomb reactor to produce fatty acid methyl ester as a biodiesel fuel. In the present study, we determined the optimum operation parameter such as reaction pressure, temperature, time and the methanol/olive oil molar ratio. The increase of the yield of fatty acid methyl ester at higher density(pressure) conditions revealed the transesterification reaction occurred by ionic reaction mechanism. The most important variables affecting methyl ester yield during the transesterification reaction are the molar ratio of methanol to olive oil, reaction temperature and reaction time. At a low temperature conditions, the transesterification reactions were less slower than that in the supercritical conditions. The time evaluation of the transesterificationreaction at the optimum operation condition (400°C,40 MPa,and the methanol/oil ratio is 3.)indicates the preferable operation time is 20 min to obtain the maximum yield of fatty acid methyl ester. The longer reaction time induces thermal decomposition of fatty acid methyl ester.

View full abstract

Synthesis of hyper branched polymer was studied by two step living radical polymerization to attain the high refractive index and low birefringence of polymer for optical use. At first step,polystyrene endcapped with 2,2,6,6-tetramethyl piperidinyl-1-oxy(PS-TEMPO)was prepared using azobisisobutyronitrile as initiator in the presence of TEMPO at 80℃ in bulk. At second step, styrene was copolymerized with divinylbenzene as branching agent using above obtained PS-TEMPO as the initiator at 120℃. It was suggested that the gelation was retarded using PS-TEMPO with narrow molecular weight distribution. High molecular weight and highly branched polymer structure was supposed by GPC and NMR analysis.

View full abstract