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1.
2.
This paper presents a method that can estimate the critical power of boiling water reactors, BWRs, with regard to spacer geometry. The current experimental method for estimating the critical power for BWR design requires many trained experts and expensive facilities to conduct the experiments. In the present method, the liquid film flow rate of adiabatic gas‐liquid two‐phase flow and a subchannel analysis of the actual BWR flow condition are measured experimentally and analyzed. In the experiment, deposition enhancement coefficients of three spacer geometries—a ferrule, an egg‐crate, and a ferrule spacer with twisted tape (CYCLONE spacer)—were estimated by measuring the liquid film flow rate of air‐water two‐phase flow flowing up in a vertical square (4 × 4) rod bundle that simulated the rod bundle of a BWR. Using these coefficients, the critical powers for bundles using each type of spacer geometry were calculated in the subchannel analysis. This method was validated using previous critical power data in the actual BWR flow condition. The critical powers predicted by this method agreed well with those of the experimental data. The result confirmed the effectiveness of this experiment‐simulation combined method, as well as the advantage over current experimental methods in terms of human and facility costs. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(5): 309–323, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20069 相似文献
3.
Yasuhiro Itoh Takamasa Oshita Kohki Satoh Hidenori Itoh 《Electrical Engineering in Japan》2014,186(1):26-33
The decomposition characteristics of an artificial biogas, which is a mixture of CH 4, CO 2, and H 2 S, using a low‐pressure DC glow discharge have been investigated. It is found that H 2, CO, C 2 H 2, H 2 O, CS 2, and COS are produced from the artificial biogas in the glow discharge. About 65% of the hydrogen atoms in CH 4 are converted into H 2 at an input energy of 800 J, at which CH 4 is completely decomposed, and the decomposition characteristics of the artificial biogas are minimally dependent on the H 2 S additive. Further, H 2 S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H 2 S, some of the carbon atoms are found to deposit on the electrodes and the wall of the discharge chamber. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 26–33, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22304 相似文献
4.
The swelling and adsorption behavior of poly(N-isopropylacrylamide)–SiO2 hybrid gels, derived from copolymerization of N-isopropylacrylamide and 3-methacryloxypropyltrimethoxysilane (MPTMOS) and following hydrolysis and condensation, were investigated. The hybrid gels exhibited temperature dependence of both the swelling ratio and adsorption of solutes, and their temperature dependence of both the swelling ratio and adsorption of solutes, and their temperature dependence was related to the MPTMOS content in the hybrid gels. In addition, the modification of thermosensitive properties of the hybrid gels could be achieved by treatment with other silane compounds. © 1996 John Wiley & Sons, Inc. 相似文献
5.
Takamasa Ishigaki Ya-Li Li Eiji Kataoka 《Journal of the American Ceramic Society》2003,86(9):1456-1463
The phase formation and microstructure of titanium oxides and composites produced by Ar–O2 thermal plasma oxidation of titanium carbide powders were investigated in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Relationships between the phase compositions and microstructures of the oxides were established by combined structural and phase analyses, in correlation with synthesis conditions and phase formation mechanisms. It is revealed that vapor condensation favored the formation of anatase, which existed as smaller particles, while liquid/solid oxidation favored the formation of rutile, which appeared as larger particles or composites. A higher oxygen input in the plasma gases (Ar + O2 ) enhanced the formation of anatase due to impeded oxidation and evaporation. A small amount of Ti4 O7 and Ti3 O5 was detected in the larger particles coexisting with rutile or TiC. These suboxides were formed as intermediates in solid oxidation of TiC or precipitated from the Ti–C–O melt during cooling. Furthermore, extensive cracks, dislocations and stresses were observed in the monolithic rutile and composites, in association with the rapid quenching in this high-temperature in-flight oxidation process. 相似文献
6.
Thermal oxidative degradation behavior of polypropylene (PP) with different tacticities was studied based on the activation energy (ΔE) data obtained by thermogravimetric analysis (TGA). The ΔE value showed a negative proportion to the content of meso pentad fraction (mmmm) in all of isotactic PP (iPP) samples, and that of syndiotactic PP sample considerably deviated from this negative proportion relationship. Since the value of mmmm was directly related to polymer chain conformation, the ΔE value was thought to have close connection with the concentration of 31 helix conformation in the iPPs. The ΔE changes would be caused by the competition between uni- and bimolecular hydroperoxide decomposition, which was controlled by concentration and character of conformations of PPs. 相似文献
7.
Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure
Ya-Li Li Fen Zheng Yong Liang Xian-Feng Ma Suo-Jing Cui Takamasa Ishigaki 《Journal of the American Ceramic Society》2001,84(4):875-877
Oxidized amorphous Si3 N4 and SiO2 powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si2 ON2 ) was observed from amorphous silicon nitride (Si3 N4 ) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si2 ON2 coexisted with β-Si3 N4 with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si2 ON2 . Pressing a mixture of amorphous Si3 N4 of lower oxygen (1.5 wt%) and SiO2 under 1.0–5.0 GPa between 1000° and 1350°C did not give Si2 ON2 phase, but yielded a mixture of α,β-Si3 N4 , quartz, and coesite (a high-pressure form of SiO2 ). The formation of Si2 ON2 from oxidized amorphous Si3 N4 seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure. 相似文献
8.
Masayuki Nogami Akihiko Koiwai Takamasa Nonaka 《Journal of the American Ceramic Society》2016,99(4):1248-1254
Glasses doped with well‐controlled Eu3+ and Eu2+ ions have attracted considerable interest due to the possibility of tuning the wavelength range of the emitted light from violet to red by using their 5D0→7Fj and 5d–4f electron transitions. Glasses were prepared to dope Eu3+ ions in a Na2O–Al2O3–SiO2 system, and the changes in the valence state of Eu3+ ions and the glass structure surrounding the Eu atoms during heating under H2 atmosphere were investigated using fluorescence spectroscopy, X‐ray absorption fine‐structure spectroscopy, and 27Al magic‐angle spinning solid‐state nuclear magnetic resonance spectroscopy. The reduction behavior of Eu3+ ions was dependent on the Al/Na molar ratio of the glass. For Al/Na < 1, the Al3+ ions formed the AlO4 network structure accompanied by the Na+ ions as charge compensators; the Eu3+ ions occupied the interstitial positions in the SiO4 network structure and were not reduced even under heating in H2 gas. On the other hand, in the glasses containing Al2O3 with the Al/Na ratio exceeding unity, the Eu3+ ions commenced to be coordinated by the AlO4 units in addition to the SiO4 network structure. When heated in H2 gas, H2 gas molecules reacted with the AlO4 units surrounding Eu3+ ions to form AlO6 units terminated with OH bonds, and reduced Eu3+ ions to Eu2+ via the extracted electrons. 相似文献
9.
Takamasa Fukuoka 《Polymer Engineering and Science》2000,40(12):2524-2538
A newly designed extruder reactor for grafting vinyl monomers onto polyolefins was studied experimentally and theoretically. The process was made up of a self‐wiping co‐rotating twin screw extruder with a separated reaction zone and two vent zones. The reactive extrusion was performed using a linear low density polyethylene, vinyltrimethoxysilane and di‐t‐butylperoxide under different operation conditions. For the purpose of process analysis, we built a computer simulation based on the reaction kinetics and rheological models studied in the preceding paper. The flow field in the extruder was calculated by the flow analysis network (FAN) method with non‐isothermal non‐Newtonian flow conditions. The iterative procedure was organized to predict local pressure, filling factor, cumulative residence time and temperature along the extruder. Furthermore, we succeeded in representing the profiles of reaction conversion and shear viscosity. Calculated results showed good agreements with the experimental data. 相似文献
10.
The authors have developed a new type of motor consisting of a piezoelectric device and strain wave gearing, and is called a piezoelectric motor. This is a first step in realizing a low-speed, small-size and lightweight motor. The principle of the motor is that the traveling wave is produced by piezoelectric devices and displacement conversion devices without mechanical resonance, and the torque to rotate the motor is generated by a mechanism of strain wave gearing (circular spline and flexspline) without using friction. The motor is operated at variable frequency and its rotational position (angle) is controlled in open-loop because it is basically a synchronous motor. In this paper, the structure and principle of the proposed motor are explained and the driving method and the mechanical characteristics of an experimental motor also are described. The results are as follows:
- 1 The realizability of the proposed piezoelectric motor is verified experimentally. The experimental motor operates at 2920 steps per revolution, and its speed range is 0 to 960 pps [or 0 to 20 (rpms)].
- 2 The torque characteristics are clarified qualitatively.
- 3 The generated torque of the experimental motor is small (less than 0.03 Nm) and therefore the improvement of the torque is an important subject hereafter.
- 4 It is possible to construct the motor with nonmetallic material. This fact is considered to facilitate obtaining a means to lighten the weight of the motor in the future.