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排序方式: 共有1017条查询结果,搜索用时 15 毫秒
71.
Masaaki Takehisa Hiromasa Watanabe Hirondo Kurihara Kouichi Yamaguchi Hayato Nakajima Toshiaki Yagi Terutaka Watanabe Takanobu Sugo Takeshi Suwa Shinsaku Maruyama Atsuro Kodama Takeo Shimada Yoshio Maruyama Masamichi Tohei Takeshi Wada Sueo Machi 《应用聚合物科学杂志》1979,24(8):1831-1844
Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm2, temperature of 30° to 80°C, mean dose rate of 4.5 × 104 to 1.9 × 105 rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 104 to 8.9 × 104, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 105 rads/hr was obtained with a 60Co source of ca. 12 kCi. 相似文献
72.
Hachijojima is a gourd-shaped volcanic island in the Pacific Ocean. Nishiyama and Higashiyama volcanoes consist of basalt lava and associated pyroclastic rocks. A promising geothermal resource was found in south Higashiyama, associated with an uplift of Tertiary rocks consisting of mainly andesite lava and related pyroclastic rocks, overlain by Quaternary volcanic rocks. Steep high-temperature (over 250°C) and high-pressure gradients occur in the deeper portion of the system near the Tertiary–Quaternary contact, indicating the presence of a cap rock. The cap rock formed by deposition of hydrothermal minerals. Geothermal fluid ascends from the deeper portions to shallow depths along vertical fractures through the cap rock. These vertical fractures form the geothermal reservoir in the Tertiary formation. Three wells were drilled into these vertical fractures, and approximately 30 t/h of superheated steam was obtained from each well during flow tests. The geothermal fluid is mainly a mixture of seawater and meteoric water in an approximate ratio of 1 to 2, based on chemical analyses, with a portion of volcanic gas included. At present a 3.3 MWe, geothermal power plant is being constructed here. 相似文献
73.
Toshiaki Kikuma Tadao Ishikawa Masahiro Takasaki Hiroshi Mochikawa Atsuhiko Kuzumaki Kazuya Kodani Takeru Murao 《Electrical Engineering in Japan》2015,192(3):54-64
The recent years have seen an increasing trend in the cumulative installed capacity of distributed generators. As a result, voltage management may become difficult in existing power distribution systems in the future. A STATCOM (STAtic synchronous COMpensator) is a promising option for solving this problem because it can control reactive power rapidly and continuously. For a distribution system, STATCOM needs to be pole‐mounted to realize its low cost. However, a transformer for a STATCOM is large and heavy, and hence it is difficult to install a STATCOM on a distribution pole. We adopt a transformerless STATCOM to reduce STATCOM size and use SiC devices with low‐loss performance to obtain a more compact and efficient STATCOM. There are a large number of circuits available for a STATCOM, and there has been considerable research on performance comparisons among these circuits. However, these comparisons were drawn under different conditions, including switching frequency and level number for the circuits. In addition, these comparisons do not include the use of SiC devices. We made an equitable comparison for a 100 kVa pole‐mounted STATCOM using SiC devices. We discuss the performance and characteristics of each circuit in terms of efficiency and volume. 相似文献
74.
Toshiaki Sakurai Ryogo Kubo Masami Watanabe Hiromi Ogi 《IEEJ Transactions on Electrical and Electronic Engineering》2008,3(1):1-4
The concept of ‘recycling’ was adopted to solve the overuse of resources by mass production and mass consumption of products in the 20th century. In the latter half of the 20th century, all companies started recycling activities slowly but positively, and some of them established their own recycling plants. This article introduces the processes through which used home appliances are made into materials (for reuse), and the machines, facilities, and methods for such reuse, as well as the results of their actual application by the study of a recycling plant. It is expected that this article would motivate the readers for recycling and to consider and feel what we, consumers, should do. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
75.
Fukai Y.K. Sugitani S. Enoki T. Yamane Y. 《Device and Materials Reliability, IEEE Transactions on》2008,8(2):289-296
We examined the issue of reliability of InP-based high-electron mobility transistors (HEMTs), focusing on the increase of drain resistance Rd. In investigations of the mechanism of Rd increase, we took note of contaminant incorporation and of the relations between the device lifetime and the strength of the channel electric field. In the fabrication process, reducing contaminants, especially fluorine, significantly suppressed the increase of source and drain resistances. Cross-sectional views of the gate of improved devices, which had a long lifetime, confirmed an almost contaminant-free surface around the gate. In acceleration tests, the most negative impact on drain resistance stability among several bias conditions was found when the current density was high and the channel electric field was large at the same time. The dependence of drain-gate electric field strength E showed that the device lifetimes of HEMTs determined from Rd increase obeyed exp(1/E), which means that impact ionization was the main cause of degradation. We elucidate that the interactions of hot carriers with contaminants around the gate are the main causes of the Rd increase in HEMTs. Suppression of device degradation was achieved by optimizing the fabrication process around the gate. In this way, device lifetime was remarkably enhanced. 相似文献
76.
Supported Co3O4 catalysts were prepared via the calcination of Co-containing hydrogarnet, (Ca3-x
Co
x
)Al2(SiO4)3- y
(OH)4y
, at 400 °C. Such precursors with various extents of substitution were synthesized from the hydrothermal reaction of a stoichiometric mixture of calcium oxide, amorphous silica, alumina sol, and cobalt hydroxide at 200 °C. It was found that the catalyst consisted of Co3O4, CaO, and mayenite and exhibited a high activity for the combustion of propylene, benzene, and toluene at temperatures below 300 °C. 相似文献
77.
Masazumi Godo Masatsune Umemura Atsushi Ishihara Toshiaki Kabe 《American Institute of Chemical Engineers》1997,43(11):3105-3110
To determine the behavior of hydrogen in tetralin, the reaction of tetralin with tritiated gaseous hydrogen was studied in a flow reactor at 400–450°C, 2.5–9.8 MPa for various residence times. The amount of hydrogen exchange between tetralin and tritiated hydrogen was estimated from the balance of hydrogen and tritium. Although yields of methylindan and naphthalene, and the hydrogen-exchange ratio (HER) of tetralin increased monotonously with residence time, these values were scarcely influenced by the reaction pressure at every temperature. It was thought that the formation of tetralyl radicals in this system would be the rate-determining step for both the conversions of tetralin into methylindan and naphthalene, and the hydrogen exchange of tetralin. Conversions of tetralin into methylindan and naphthalene, and the hydrogen-exchange reaction using the autoclave were very close to those using the flow reactor. 相似文献
78.
Hirotoshi Miyazaki Kazutoshi Terada Toshiaki Sato Hitoshi Maruyama Takuji Okaya 《应用聚合物科学杂志》1996,60(12):2149-2157
In dispersion polymerization of styrene in ethanol, effects of a reactive steric stabilizer, poly(vinyl acetate/vinyl alcohol) copolymer with a thiol end group (P(VAc/VA)-SH), were investigated. In the absence of the thiol end group, the dispersion coagulated at the middle stage of the polymerization, while in the presence of the thiol end group, the polymerization proceeded successfully to result in close to monodisperse particles. The reactive thiol group acts as a site of formation of the block copolymer, that is, polystyrene-b-P(VAc/VA), which is utilized as an effective dispersant. From the measurement on molecular weights during the course of polymerization, two polymerization loci were realized. Addition of butyl methacrylate to styrene affected markedly not only rate of polymerization but also particle size. © 1996 John Wiley & Sons, Inc. 相似文献
79.
Ken Shimomai Noboru Higashida Toshiaki Ougizawa Takashi Inoue Bernd Rudolf Jörg Kressler 《Polymer》1996,37(26):5877-5882
The miscibility of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymers (SAN) blends was investigated on the basis of the Flory—Orwoll—Vrij equation of state theory. To obtain the equation of state parameters (P*, V*sp, T*: characteristic parameters), the pressure—volume—temperature (PVT) behaviour was measured for PMMA and a series of SANs with various acrylonitrile contents. The exchange energy parameter Xij was also calculated by fitting the theory to some phase diagrams of PMMA/SAN blends. The Flory—Huggins interaction parameter χ was separated into two contributions based on the equation of state theory for mixtures: the exchange energy term χinter and the free volume term χfree. Both the temperature and copolymer composition dependences of χinter and χfree were estimated by calculations using the equation of state parameters. There exists a region in which χinter is negative, leading to a miscibility window in PMMA/SAN blends. However, the immiscibility at high temperatures in the blends cannot be explained only by χinter; it is caused by the free volume contribution, χfree. The miscibility window behaviour in PMMA/SAN blends may be explained within the framework of the equation of state theory. 相似文献
80.
We propose a new geometric method of IR factorization in sector decomposition. The problem is converted into a set of problems in convex geometry. The latter problems are solved using algorithms in combinatorial geometry. This method provides a deterministic algorithm and never falls into an infinite loop. The number of resulting sectors depends on the algorithm of triangulation. Our test implementation shows smaller number of sectors comparing with other existing methods with iterations. 相似文献