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51.
52.
Tetsuo Oka Tomoki Muraya Nobutaka Kawasaki Satoshi Fukui Jun Ogawa Takao Sato Toshihisa Terasawa 《低温学》2012,52(1):27-31
A demagnetized Nd–Fe–B permanent magnet was scanned just above the magnetic pole which contains the HTS bulk magnet generating a magnetic field of 3.27 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. We examined the magnetic field distributions when the magnetic poles were scanned twice to activate the magnet plate inversely with various overlap distances between the tracks of the bulk magnet. The magnetic field of the “rewritten” magnet reached the values of the magnetically saturated region of the material, showing steep gradients at the border of each magnetic pole. As a replacement for conventional pulse field magnetizing methods, this technique is proposed to expand the degree of freedom in the design of electromagnetic devices, and is proposed as a novel practical method for magnetizing rare-earth magnets, which have excellent magnetic performance and require intense fields of more than 3 T to be activated. 相似文献
53.
Naoki Satoh Hideki Tomiyama Toshihisa Kajiwara 《Polymer Engineering and Science》2001,41(9):1564-1579
Numerical simulations of the film casting process were performed using a finite element method for Newtonian and viscoelasttc fluids. We simplified the governing equations by the assumption that the stress and velocity gradients in the thickness direction were negligible, and obtained the film thickness and mean value of stress and velocity components in the thickness direction as variables. Viscoelasticity was described by the Larson model with multiple relaxation times. Non‐isothermal conditions were considered by applying the time‐temperature superposition law. The simulation results for the several kinds of commercial low‐density polyethylenes wore compared to the experimental data for a laboratory‐scale process at l90°C and a commercial‐scale process at 310°C. The film width and film thickness distribution at chill roll, and the change of film width were in good agreement for the laboratory‐scale process, but the agreement for the commercial‐scale process was; not as good. In the simulation of the commercial‐scale process at high temperature, the value predicted by the use of the Viscoelasticity for the original pellet showed poor agreement owing to the change of Viscoelasticity in the process. The agreement was improved by the use of the Viscoelasticity for the processed resin, which was changed from the original one. Next, viscoelastic effects on neck‐in and edge bead phenomena were investigated. The neck‐in and edge bead phenomena were considered to be affected by both the uniaxial elongational viscosity and planar elongational viscosity. 相似文献
54.
Reactive miscible viscous fingering occurs when a reactive and miscible less-viscous liquid displaces a more-viscous liquid. Effects of bulk finger-growth velocity on reaction characteristics of miscible viscous fingering with a chemical reaction were studied analytically by using a convection-diffusion-reaction model. The model assumes the existence of a distinct interface between both liquids, assumes the existence of a two-dimensional, steady, stagnated flow field in the less-viscous liquid, and assumes an infinite chemical reaction rate. The model was then used to determine the reaction characteristics, such as the location of the reaction surface and the profile of the product, as functions of the velocity and initial reactant concentrations. The results reveal that the effects of the velocity on the reaction characteristics can be divided into low-, intermediate-, and high-velocity regions. In the low-velocity region, the reaction characteristics strongly depend on the reactant concentrations. In the intermediate-velocity region, the dependence of the reaction characteristics on the reactant concentrations decreases with increasing velocity. In the high-velocity region, the reaction characteristics are nearly independent of the reactant concentrations. Experiments confirm the existence of these three velocity regions predicted by the model. 相似文献
55.
An orbital instability of the unsteady flame tip motion with burner rotation and the possibility of the prediction of the flame tip motion are investigated from the viewpoint of nonlinear dynamics. A rich methane–air mixture of equivalence ratio 1.43 is used. The mean exit velocity from the burner tube, U, is varied from 0.6 to 1.3 m/s, keeping the swirl number S=1.14 constant. The variation in the flame tip motion is quantitatively evaluated by calculating the mean value of a parallel trajectory value Γ. At U0.7 m/s, the value of Γ is estimated to be approximately zero, indicating that periodic motion occurs. As U increases, the trajectory of the attractor becomes complicated and Γ gradually increases. The value of Γ approaches the value of the Fourier-transformed surrogate data with further increase in U. This suggests that the flame tip motion varies from periodic to chaotic due to the influence of phase randomness with increasing U. The short-term forward prediction method, that is based on the orbit of the attractor, first was used. Then the short-term forward prediction method was modified to successfully extend the prediction term. The results suggest that the modified short-term forward prediction method proposed in the present study provides a valid method for predicting the motion of unsteady flames. 相似文献
56.
Shigeyuki Imura Toshihisa Watabe Kazunori Miyakawa Kei Hagiwara Hiroshi Ohtake Misao Kubota 《Journal of Materials Science: Materials in Electronics》2017,28(10):7064-7069
In this study, the surface enhancement of thin-film crystalline selenium (c-Se) is successfully demonstrated through grain refinement using chlorine (Cl) doping. We fabricated c-Se films via doping with various halogens, such as Cl, bromine (Br), and iodine (I). In particular, for Cl, we prepared c-Se films with different doping concentrations of 0, 50, and 500 ppm on glass substrates to investigate the details of concentration effects on surface enhancement. The long helical chains of Se atoms that comprise a large molecule in hexagonal Se, which is the most stable form of Se, are terminated via halogen doping into Se, leading to a marked reduction in the size of polycrystalline grains. In addition, the grain size of c-Se sharply decreases as the Cl doping concentration is increased. The mean surface roughness of a 500-ppm-Cl-doped c-Se film measured via atomic force microscopy decreased to approximately one-fourth that of the equivalent undoped c-Se film. This is a promising technology that could bring great benefits to c-Se-based imaging devices. 相似文献
57.
58.
Toshihisa Masuda Akira Negishi Kotaro Tanaka Takeo Honda Takahiro Fujii 《Electrical Engineering in Japan》1993,113(3):46-55
The alkali metal thermoelectric converter (AMTEC) utilizing the sodium ion conducting β-alumina is a device to convert heat energy to electric energy directly. It is characterized by high conversion efficiencies, high power densities, no moving parts and low maintenance requirements. Because of these merits, AMTEC is one of the most promising candidates for aerospace power systems, remote power stations and dispersed small-scale power stations. In this paper, the experimental results of the series-connected cells and the theoretical considerations about internal resistances have been reported. For the single cell, the open voltage of 1.37 V and the maximum power of 7.89 W and maximum power density of 0.40 W/cm2 at the sodium temperature of 1077 K have been obtained. For the two series-connected cells, the open voltage of 2.60 V and the maximum power of 12.3 W at the sodium temperature of 1016 K have been obtained. This power was about 90 percent of the sum power of two cells. This power decrease is due to the resistance of the current-collecting busbar. It is necessary to optimize the current-collecting busbar considering the electrical resistance and heat conductance. 相似文献
59.
Sunho You Naotaka Higuchi Toshihisa Ueda 《Korean Journal of Chemical Engineering》2009,26(6):1497-1503
We investigated the mixing process of the Kenics type static mixer, in which the mixing is enhanced by both advective mixing
and mixing due to molecular diffusion in order to propose an estimation method of the mixedness. The results show that the
element divides, folds and stretches the mixing fluids and forms a lamellar structure with striation width l
a
. The value of l
a
decreases with an increase in the number of elements by l
a
-(2
n−1)−1, which represents the characteristics length of advective mixing. The characteristic length of mixing due to molecular diffusion
l
d
can be estimated by solving the one-dimensional unsteady species conservation equation analytically. The macroscopic estimation
and prediction method of mixedness is proposed as function of l
a
and l
d
. When l
a
>l
d
, the advective mixing is dominant, while, when l
a
<l
d
, the mixing due to molecular diffusion plays an important role. 相似文献
60.