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$C_{x}F_{y}$ Polymer Film Deposition in rf and dc $C_{7}F_{16}$ Vapor Plasmas
Sakai, Y.,Akazawa, M.,Sakai, Yosuke,Sugawara, H.,Tabata, M.,Lungu, C.P.,Lungu, A.M. The Korean Institute of Electrical and Electronic 2001 Transactions on Electrical and Electronic Material Vol.2 No.1
$C_{x}F_{y}$ polymer film was deposited in rf and dc Fluorinert vapor ($C_{7}F_{16}$) plasmas. In the plasma phase, the spatial distribution of optical emission spectra and the temporal concentration of decomposed species were monitored, and kinetics of the $C_{7}F_{16}$ decomposition process was discussed. Deposition of $C_{x}F_{y}$ film has been tried on substrates of stainless steel, glass, molybdenum and silicon wafers at room temperature in the vapor pressures of 40 and 100 Pa. The films deposited in the rf plasma showed excellent electrical properties as an insulator for multi-layered interconnection of deep-submicron LSI, i.e. the low dielectric constant ∼2.0, the dielectric strength ∼2 MV/cm and the high deposition rate ∼100nm/min at 100W input power.
POLYMERIC MATERIALS USABLE FOR GAS SENSORS
Sakai, Y. 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.1 No.3
Various types of sensors to monitor humidity and gases were prepared using organic polymers. In order to prepare resistive type humidity sensors which can be used at high humidities, several methods of cross-linking of hydrophilic polymer chains were proposed, while in order to prepare capacitive humidity sensors durable in organic solvent vapors, utilization of cross-linked hydrophobic polymers were proposed. In addition, for a resistive type $CO_2$ sensors, solid polyethylene glycol containing alkali carbonate can be used. Polymers which have dimethyl amino branch can be used for the sorbing layer in a QCM type sensor. These polymers are alos applicable to the fabrication of both resistive and QCM type acetic acid vapor sensor. Polypyrrole and polyaniline can be used to detect $NH_3$gas.
Complexity Control Method of Chaos Dynamics in Recurrent Neural Networks
Sakai, Masao,Homma, Noriyasu,Abe, Kenichi Institute of Control 2002 Transaction on control, automation and systems eng Vol.4 No.2
This paper demonstrates that the largest Lyapunov exponent λ of recurrent neural networks can be controlled efficiently by a stochastic gradient method. An essential core of the proposed method is a novel stochastic approximate formulation of the Lyapunov exponent λ as a function of the network parameters such as connection weights and thresholds of neural activation functions. By a gradient method, a direct calculation to minimize a square error (λ - λ$\^$obj/)$^2$, where λ$\^$obj/ is a desired exponent value, needs gradients collection through time which are given by a recursive calculation from past to present values. The collection is computationally expensive and causes unstable control of the exponent for networks with chaotic dynamics because of chaotic instability. The stochastic formulation derived in this paper gives us an approximation of the gradients collection in a fashion without the recursive calculation. This approximation can realize not only a faster calculation of the gradient, but also stable control for chaotic dynamics. Due to the non-recursive calculation. without respect to the time evolutions, the running times of this approximation grow only about as N$^2$ compared to as N$\^$5/T that is of the direct calculation method. It is also shown by simulation studies that the approximation is a robust formulation for the network size and that proposed method can control the chaos dynamics in recurrent neural networks efficiently.
Conclusions and Suggestions on Low-Dose and Low-Dose Rate Radiation Risk Estimation Methodology
Sakai, Kazuo,Yamada, Yutaka,Yoshida, Kazuo,Yoshinaga, Shinji,Sato, Kaoru,Ogata, Hiromitsu,Iwasaki, Toshiyasu,Kudo, Shin'ichi,Asada, Yasuki,Kawaguchi, Isao,Haeno, Hiroshi,Sasaki, Michiya The Korean Association for Radiation Protection 2021 방사선방어학회지 Vol.46 No.1
Background: For radiological protection and control, the International Commission on Radiological Protection (ICRP) provides the nominal risk coefficients related to radiation exposure, which can be extrapolated using the excess relative risk and excess absolute risk obtained from the Life Span Study of atomic bomb survivors in Hiroshima and Nagasaki with the dose and dose-rate effectiveness factor (DDREF). Materials and Methods: Since it is impossible to directly estimate the radiation risk at doses less than approximately 100 mSv only from epidemiological knowledge and data, support from radiation biology is absolutely imperative, and thus, several national and international bodies have advocated the importance of bridging knowledge between biology and epidemiology. Because of the accident at the Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Station in 2011, the exposure of the public to radiation has become a major concern and it was considered that the estimation of radiation risk should be more realistic to cope with the prevailing radiation exposure situation. Results and Discussion: To discuss the issues from wide aspects related to radiological protection, and to realize bridging knowledge between biology and epidemiology, we have established a research group to develop low-dose and low-dose-rate radiation risk estimation methodology, with the permission of the Japan Health Physics Society. Conclusion: The aim of the research group was to clarify the current situation and issues related to the risk estimation of low-dose and low-dose-rate radiation exposure from the viewpoints of different research fields, such as epidemiology, biology, modeling, and dosimetry, to identify a future strategy and roadmap to elucidate a more realistic estimation of risk against low-dose and low-dose-rate radiation exposure.
Comparative Study on Pitting Corrosion of Copper Tubes in Pitting and Fitting-Free Area
Sakai, Masahiro,Seri, Osami 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.3
Field tests for the copper tube in the area where pitting corrosion has often occurred were carried out in order to investigate the initiation and the propagation of pits. For a comparative study, we installed the same field equipment in two areas (pitting and pitting-free areas) to measure the corrosion potential of copper tubes and the electric conductivity of tap water. The electric conductivity in the pitting area was higher than that in the pitting-free area during the whole period of examination. It was found that the pitting corrosion has occurred in both pitting and pitting-& areas, but the maximum pit in the pitting area after 12 months was about three times deeper than that in the pitting-free area after 12 months.
CYP1A1, GSTM1, GSTT1 and TP53 Polymorphisms and Risk of Gallbladder Cancer in Bolivians
Sakai, Kazuaki,Loza, Ernesto,Roig, Guido Villa-Gomez,Nozaki, Ryoko,Asai, Takao,Ikoma, Toshikazu,Tsuchiya, Yasuo,Kiyohara, Chikako,Yamamoto, Masaharu,Nakamura, Kazutoshi Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.2
The Plurinational State of Bolivia (Bolivia) has a high incidence rate of gallbladder cancer (GBC). However, the genetic and environmental risk factors for GBC development are not well understood. We aimed to assess whether or not cytochrome P450 (CYP1A1), glutathione S-transferase mu 1 (GSTM1), theta 1 (GSTT1) and tumor suppressor protein p53 (TP53) genetic polymorphisms modulate GBC susceptibility in Bolivians. This case-control study covered 32 patients with GBC and 86 healthy subjects. GBC was diagnosed on the basis of histological analysis of tissues at the Instituto de Gastroenterologia Boliviano-Japones (IGBJ); the healthy subjects were members of the staff at the IGBJ. Distributions of the CYP1A1 rs1048943 and TP53 rs1042522 polymorphisms were assayed using PCR-restriction fragment length polymorphism assay. GSTM1 and GSTT1 deletion polymorphisms were detected by a multiplex PCR assay. The frequency of the GSTM1 null genotype was significantly higher in GBC patients than in the healthy subjects (odds ratio [OR], 2.35; 95% confidence interval [CI], 1.03-5.37; age-adjusted OR, 3.53; 95% CI, 1.29-9.66; age- and sex-adjusted OR, 3.40; 95% CI, 1.24-9.34). No significant differences were observed in the frequencies of CYP1A1, GSTT1, or TP53 polymorphisms between the two groups. The GSTM1 null genotype was associated with increased GBC risk in Bolivians. Additional studies with larger control and case populations are warranted to confirm the association between the GSTM1 deletion polymorphism and GBC risk suggested in the present study.