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排序方式: 共有925条查询结果,搜索用时 15 毫秒
101.
Hiroyuki Sato Shinji KuboXing L. Yan Yukio TachibanaYukitaka Kato 《Progress in Nuclear Energy》2011,53(7):1009-1016
Operability of Very High Temperature Reactor (VHTR) hydrogen cogeneration systems in response to abnormal transients initiated by the hydrogen production plant is one of the important concerns from economical and safety points of views. The abnormal events in the hydrogen production plant could initiate load changes and induce temperature variations in a primary cooling system. Excessive temperature increase in the primary cooling system would cause reactor scrams since the temperature increase in the primary cooling system is restricted in order to prevent undue thermal stresses from reactor structures. Also, temperature decrease has a potential propagation path for reactor scrams by reactivity insertions as a consequence of the reactivity feedbacks. Since suspensions of reactor operation and electricity generation should be avoided even in case of abnormal events in the hydrogen production plant from an economical point of view, an establishment of a control scheme against abnormal transients of hydrogen production plant is required for plant system design.In the present study, basic controls and their integration for the GTHTR300C, a VHTR cogeneration system designed by JAEA with a direct Brayton cycle power conversion unit and thermochemical Iodine-Sulfur process hydrogen production plant (IS hydrogen production plant), against abnormal transients of IS hydrogen production plant are presented. Transient simulations for selected load change events in the IS hydrogen production plants are performed by an original system analysis code which enables to evaluate major phenomena assumed in process heat exchangers of the IS hydrogen production plant.It is shown that abnormal load change events are successfully simulated by the system analysis code developed. The results demonstrated the technical feasibility of proposed controls for continuous operation of the reactor and power conversion unit against load change events in the IS hydrogen production plant. 相似文献
102.
Kiyoung Lee Yukio Yanagisawa John D. Spengler Halûk
zkaynak Irwin H. Billick 《Indoor air》1993,3(2):124-130
The sampling rate of a nitrogen dioxide (NO2) passive sampling badge was evaluated in indoor environments including an unoccupied research house, residential houses, and an office. Measurements from the NO2 badges were compared with those of a chemiluminescent analyzer the EPA reference method, by placing them near to the sample inlet of the chemiluminescent analyzer In this study, we used a new sampling rate for the NO2 badge placed in indoor environments (an overall mass transfer coefficient of 0.10 cm/s) smaller than the rate previously reported for the badge when used outdoors. The new rate provides more accurate measurements of NO, concentrations in indoor environments. Indoor NO2 concentrations were also measured with the NO2 badges exposed to a constant wind velocity provided by a wind tunnel. Since the measurements of the badge with a constant wind velocity agreed well with the reference method, the badges could be assumed to be a secondary reference measurement. With the badges used as the secondary reference measurement, we developed a portable wind tunnel to evaluate a personal exposure measurement by the badge. The results are presented in Environment International (Lee et al., 1993). Precision of the badge measurements was as good as an intraclass correlation coefficient of 0.9779. It was determined that placement of the badge should be at least 10 cm out from an indoor wall surface to avoid undersampling due to NO2 gradients near the surface. 相似文献
103.
Manabu Iguchi Yukio Terauchi Shin-Ichiro Yokoya 《Metallurgical and Materials Transactions B》1998,29(6):1219-1225
Bubble formation from a single-hole nozzle placed vertically upward in a rotating water bath was investigated using a high-speed
video camera. Air was used as the working gas. The measured values of the frequency of bubble formation, f
B, were compared with those observed in a stationary bath, f
B0. The velocity of cross-flow, νθ, affected the bubble formation significantly when it exceeded a critical value, νθc
. The ratio of f
B to f
B0 was unity for νθ≦νθc
, but it changed in a complex manner for νθ>νθc
. In the latter case, when the air flow rate Q
g was relatively low, f
B/f
B0 became larger than unity irrespective of Q
g, and an empirical correlation of f
B/f
B0 was proposed as a function of νθ and the inner diameter of the nozzle, d
ni. As the gas flow rate increased, f
B/f
B0 decreased monotonically and became smaller than unity, and an empirical correlation of f
B/f
B0 was derived as a function of Q
g, νθ, and d
ni. These empirical correlations could approximate the measured values of f
B/f
B0 within a scatter of −15 to +20 pct. 相似文献
104.
105.
The diversity of human immunodeficiency virus (HIV) in vivo has been reported. In this article, we propose a cellular automata
(CA) model describing the interactions between the immune system and HIV, and examine the effect of the diversity of these
interactions. The novel aspects of our CA model are that it not only considers four states (HIV, virgin, dead, infect) but
also the diversity exhibited by both HIV and T cells. We simulated maximum diversities for these states by simulating CA on
a computer. The model revealed that increased diversity had the effect of increasing the HIV population and simulation steps.
In addition, we observed that the CA model accurately reflects the occurrence of infection, incubation period, and the development
of AIDS. The CA model demonstrated that the diversity of the virus is the major factor affecting the success rate of the escape
of HIV from the immune response.
This work was presented in part at the 10th International Symposium on Artificial Life and Robotics, Oita, Japan, February
4–6, 2005 相似文献
106.
A method of numerical calculation for radiation heat transfer in a three‐dimensional closed space including diffuse and specular surfaces was developed. To enable an analysis of the radiation heat exchange on each surface considering multiple specular reflections and obstacles to radiation in the space, an improved heat ray‐tracing method was presented to calculate view factors accurately. The method was determined to be applicable to complicated problems in test calculations using models with specular surfaces and obstacles. Continuing efforts are being applied to more realistic problems. The example examined in this paper is an infrared emitter with a parabolic specular reflector, which is a conventional electric heating apparatus. The measured result for radiant power distribution agrees well with the calculated one. The practical validity of our method was verified. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(2): 108–129, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10074 相似文献
107.
Yukio Yasukawa 《亚洲传热研究》2006,35(2):165-177
An experimental study was performed on the nucleate boiling of water in the narrow space formed between an interference piece and the heating surface of heat‐proof glass. A past study analyzed the bubble growth due to the conduction of heat through the thinner liquid layer under a growing bubble; however, the thickness of the liquid layer was not shown experimentally. This study investigates the thickness of this thinner layer by the interference method. Almost no change was found on the thickness of the liquid layer under both the interference‐piece and on the heating surface. The experimental results indicate the great contribution of superheating of the test liquid to bubble growth. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 165–177, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/htj.20100 相似文献
108.
Routing design of tree‐shaped local public communication networks with high reliability and low cost
This paper discusses reliability problems for local public communication networks such as cable television networks and the
subscriber‐loops of telecommunication networks. They have tree‐shapes and expand continuously as new customers join. By introducing
a simple model, it is shown that most principal reliability measures and cost measures for such networks can be described
through the networks' graphical characteristic quantities. Extensive simulations show that the prior provision of trunk pipes
and a suitable choice of the route selecting rule for new customers are effective in constructing a highly reliable network
with low cost.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
109.
To induce degradabilities in polymers in response to environmental conditions, the end-modification reactions of poly(α-methylstyrene) derivatives were carried out. When diphenylphosphine chloride was used as a modifier for the living end of para-substituted PMS, the coupling efficiency was ca. 50%. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-(4-tolyl)allyl bromide, and α-trifluoromethylstyrene were found to be suitable end-modification agents. For example, ω-2-phenylallyl PMS was prepared with almost quantitative functionality by the reaction of the living PMS with 2-phenylallyl bromide. In a similar way, ω-3,3-difluoro-2-phenylallyl and ω-2-(4-tolyl)allyl PMS derivatives were synthesized. Based on thermogravimetric analysis, onset of the degradation temperature of the end-modified PMS derivatives decreased in the following order: ω-hydrogen- > ω-3,3-difluoro-2-phenylallyl- > ω-2-phenylallyl- > ω-2-(4-tolyl)allyl-PMS. Actually, the onset temperature of ω-2-(4-tolyl)allyl-PMS derivatives was 50°C lower than that of ω-H-PMS derivatives. These results indicate that the active species is produced effectively at the end unsaturated bond, which initiates the depolymerization of the polymer at rather low temperatures. Ionic degradation of these polymers was also investigated using butyllithium as an anionic initiator and methanesulfonic acid as a cationic initiator. Tendencies similar to the thermal degradation were observed. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through several mechanisms such as radical, anionic and cationic depolymerization reactions. 相似文献
110.
Takahiro Takada Shuya Nakao Masaru Kojima Yukio Higuchi 《International Journal of Applied Ceramic Technology》2007,4(5):398-405
The effects of an inner constraint layer and alumina particles on the microstructure, strength, and shrinkage of the laminated low-temperature cofired ceramic (LTCC) green sheet were investigated. Alumina particles of several sizes were used in the inner-constraint layer in order to strengthen the LTCC substrate. Smaller alumina particles in the inner-constraint layer produced a substrate with a high bending strength. Sintering shrinkage in the x – y direction of the LTCC is related to the bending strength of the debinded alumina particle layer used for an inner-constraint layer. A larger pore size in the inner-constraint layer was found to increase the distance of the glass penetration from the glass–alumina layer into the inner-constraint layer. The total thickness of the constraint layer changes the shrinkage in the x – y direction and the bending strength. 相似文献