Search

The magnesium alloy has advantage in strength per mass and it has been widely used on airplane, aerospace, computer, cellphone and automobile industries. However, forming of magnesium alloy plate at the room temperature is very difficult, because it has a dense hexagonal and the basal sliding is easy to happen conspicuously in comparison with other sliding system. We considered that those weak characteristics are reduced by high strain rate forming. Therefore, magnesium alloy forming using shock wave by metal wire electric discharge has been carried out. Thin aluminum alloy was used as the metal wire. Electricity is supplied to this wire from power supply with Cockcroft-Walton circuit. The aluminum wire set underwater and it has instantly molten vaporization, then, the underwater shock wave was generated. The shock loading by the underwater shock wave acts to the magnesium alloy plate. The magnesium alloy plate was AZ31(Al 3%, Zn 1%). In this study, the target is bulge forming of the magnesium alloy plate. Then, some numerical simulations were carried out. These results will be discussed in this paper. [ABSTRACT FROM AUTHOR]

Okinawa National College of Technology has developed a food processing machine using underwater shock waves. Several prototype machines were developed, and experimental results (sterilization, improvement of juice extraction, milling flour, emulsification etc.) were obtained. After deciding food materials to be processed and the desired processing results, we designed and manufactured a pressure vessel for experiments. In this report, the process flow for designing and manufacturing a pressure vessel for softening meat using underwater shock and its concept design are described. The relationships among the number of shock waves, the distance between the shock wave generation point and the meat, the backing material, and the amount of softening ware experimentally compared. We measured the velocity of the shock wave penetrating to the inside of the meat, from which we estimated the particle velocity. We developed computer simulation model using the estimated particle velocity in the meat. Using the results of the analysis obtained from the computer simulation model, we designed and fabricated the pressure vessel. [ABSTRACT FROM AUTHOR]

We perform herein a direct observation of shockwave propagation using a high-speed camera and estimate properties, such as acoustic velocity and Hugoniot parameter, using the impedance matching scheme to reveal the dynamic characteristics of Okinawa's unique soil "Shimajiri Mahji." A computational simulation corresponding to the experimental setup is then conducted. A comparison of the numerical and experimental results demonstrates their fairly good agreement, which suggests that the experimentally estimated dynamic characteristics of "Shimajiri Mahji" are valid. In addition, a computational simulation based on the smoothed particle hydrodynamics is also modeled and performed to elucidate the fragment behavior when the unexploded bomb explosive is at the soil surface. From a series of computational results, we have confirmed and clarified that the fragment behavior is significantly dependent on the amount of explosive charge and soil characteristics. [ABSTRACT FROM AUTHOR]

To clarify the shock characteristics of Okinawa's unique soils "Jahgaru" that is widely distributed in southern part of Okinawa Main Island, an experimental investigation of dynamics properties such as shockwave propagation, pressure and particle velocity have been performed using impedance matching method. Therefore, we have also obtained the Hugoniot date of "Jahgaru". And then, to reveal a validity of the material characteristics, a computational model for the experimental procedure using ALE simulation have been developed. A comparison between numerical results and experimental ones, the capability of proposed method through the numerical simulations have been confirmed. [ABSTRACT FROM AUTHOR]

The explosive forming is a characteristic method. An underwater shock wave is generated by underwater explosion of an explosive. A metal plate is affected high strain rate by the shock loading and is formed along a metal die. Although this method has the advantage of mirroring the shape of the die, a free forming was used in this paper. An expensive metal die is not necessary for this free forming. It is possible that a metal plate is formed with simple supporting parts. However, the forming shape depends on the shock pressure distribution act on the metal plate. This pressure distribution is able to change by the shape of explosive, a mass of explosive and a shape of pressure vessel. On the other hand, we need the pressure vessel for food processing by the underwater shock wave. Therefore, we propose making the pressure vessel by this explosive forming. One design suggestion of pressure vessel made of stainless steel was considered. However, we cannot decide suitable conditions, the mass of the explosive and the distance between the explosive and the metal plate to make the pressure vessel. In order to decide these conditions, we have tried the numerical simulation on this explosive forming. The basic simulation method was ALE (Arbitrary Lagrangian-Eulerian) method including with Mie-Grüneisen EOS (equation of state), JWL EOS, Johnson-Cook constitutive equation for a material model. In this paper, the underwater pressure contours to clear the propagations of the underwater shock wave, forming processes and deformation velocity of the metal plate is shown and it will be discussed about those results. [ABSTRACT FROM AUTHOR]

We have been investigating underwater-explosion-induced shockwave-propagation phenomena for use in a robust food-processing system. This system comprises a high-voltage capacitor bank with a gap switch, water tank, and wire explosive. We performed an optical examination of the shockwave generated by a wire explosion using an electrical discharge in the water tank. Simultaneously, we measured the shock pressure and investigated the effects of various electrical characteristics upon the shockwave propagation phenomena. To obtain various strengths of the underwater shockwave, 0.6-, 1.0-, and 1.4-mm width wires made from 1.0-mm-thick aluminum plates were used at various voltages. As an example, a shockwave with a propagation velocity of 1,600 m/s was observed from an explosion generated using a 1.0-mm-width aluminum wire. We found that the strength of the shockwave could be controlled by the applied discharge voltage and wire size. [ABSTRACT FROM AUTHOR]

Self-sufficiency in food is very low (about 40%) in Japan. Therefore, the rice powder is paid to attention because it can be processed to the udon (noodle) and bread etc. We has already developed the rice-powder disintegrator using the underwater shock wave by the electrode. But it has not been cleared what is the most suitable pressure vessel. The purpose of this study is to investigate the most suitable configuration of the pressure vessels for manufacturing the rice-powder using the underwater shock wave. Experimental conditions to manufacture the rice-powder (particle size is 100 μm) is clarified using this device. Moreover, the manufacturing efficiency of the rice-powder, the relation between the number of the shock wave generation and the grain degree of rice-powder is clarified. [ABSTRACT FROM AUTHOR]

We asked whether climate change might affect the geographic distributions of Aedes aegypti (L.) and Aedes albopictus (Skuse) (Diptera: Culicidae). We tested the effects of temperature, diet and the presence of congeneric species on the performance of immature stages of these two aedine species in the laboratory. Mosquitoes in three different species-density combinations were reared at four constant temperatures (20 °C, 25 °C, 30 °C, 35 °C) on low- or high-level diets. Of the four temperatures tested, mortality increased only at 35 °C in both species. Mortality was higher on the high-level diet than on the low-level diet at 35 °C, but not at other temperatures. The presence of congeneric species had a significant positive effect on mortality in Ae. albopictus, but not in Ae. aegypti. Both species developed more quickly at higher temperatures within the range of 20-30 °C; development was not enhanced at 35 °C. Population growth of Ae. albopictus was more stable, regardless of diet and temperature; that of Ae. aegypti varied more according to these two factors. These species-specific attributes may help to explain the latitudinal distribution of the mosquitoes and degree of species dominance where they are sympatric. [ABSTRACT FROM AUTHOR]

A numerical model and computational procedure for static recrystallization are developed using a phase-field method coupled with crystal-plasticity theory. In this model, first, the microstructure and dislocation density during the deformation process of a polycrystalline metal are simulated using a finite element method based on strain-gradient crystal-plasticity theory. Second, the calculated data are mapped onto the regular grids used in the phase-field simulation. The stored energy is calculated from the dislocation density and is smoothed to avoid computational difficulty. Furthermore, the misorientation required for nucleation criteria is calculated at all grid points. Finally, phase-field simulation of the nucleation and growth of recrystallization is performed using the mapped data. By performing a series of numerical simulations based on the proposed numerical procedure, it has been confirmed that the recrystallization microstructure can be reproduced from the deformation microstructure. [ABSTRACT FROM AUTHOR]

A numerical model and computational procedure for static recrystallization are developed using a phase-field method coupled with crystal-plasticity theory. In this model, first, the microstructure and dislocation density during the deformation process of a polycrystalline metal are simulated using a finite element method based on strain-gradient crystal-plasticity theory. Second, the calculated data are mapped onto the regular grids used in the phase-field simulation. The stored energy is calculated from the dislocation density and is smoothed to avoid computational difficulty. Furthermore, the misorientation required for nucleation criteria is calculated at all grid points. Finally, phase-field simulation of the nucleation and growth of recrystallization is performed using the mapped data. By performing a series of numerical simulations based on the proposed numerical procedure, it has been confirmed that the recrystallization microstructure can be reproduced from the deformation microstructure. [ABSTRACT FROM AUTHOR]

A 7-year and 11 month-old girl with cerebellar astrocytoma linked to familial ataxia-telangiectasia (AT) is presented. She was born as the 7th girl of a woman with aortic arch syndrome. Two elder sisters of the patient have ataxia telangiectasia. She had immunodeficiency, and cerebellar ataxia, but had no oculocutaneous telangiectasia. The risk of cancer developing in AT patients is about 1,200 times greater than that in age-matched controls. With regard to central nervous system tumours, seven primary tumours have been reported, such as 3 cases of medulloblastoma and 4 cases of glioma. Members of AT families who were under the age of 45 had a risk of dying of a malignant neoplasm five times greater than in the general population. However, there were no reports of glioma in AT families. In this case, it is suggested that IgA deficiency linked to familial AT may have contributed to the development of astrocytoma. [ABSTRACT FROM AUTHOR]