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  • Author or Editor: S. Tanaka x
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Fuzzy inference approach was applied to select the control input for the precision water bath of the heat exchange calorimeter used at a non-air-conditioned laboratory. The thermal fluctuation of the bath water was necessary to be kept within a narrow range. The cooling water or coolant kept at a temperature lower than the set temperature was circulated in the bath. The deviation corresponding to the difference between the set temperature and the observed temperature was observed as the input signal. The output or control input to be given to the heather element in the water bath was calculated by the fuzzy modus. The output function was simplified by means of circulating the cooling water. The contribution of each membership function was changed according to the thermal progress of the observed temperature of the water. The whole system including the control programs was examined by a practical water bath, and fairly good results were obtained. Reasonable recoveries were also shown for external thermal disturbances given to the controlled system.

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Adsorption experiments were performed to measure distribution coefficients of237Np(V),238Pu(IV) and241Am(III) for sedimentary sequential chemical extraction of the adsorbed radionuclides was carried out with water, CaCl2, KCl, NH2OH−HCl, K-oxalate and H2O2 solutions, to elucidate their dominant sorption mechanisms. The distribution coefficient of237Np was two orders of magnitude smaller than that of238Pu and241Am. Most of237Np adsorbed was extracted with CaCl2 solution and its sorption was controlled by a reversible ion exchange reaction. The adsorbed238Pu was mainly extracted with NH2OH−HCl+K-oxalate solution and its sorption was possibly controlled by irreversible reactions.

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The following first order nonlinear differential equation with a deviating argument
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage{bbm} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$x'(t) + p(t)[x(\tau (t))]^\alpha = 0$$ \end{document}
is considered, where α > 0, α ≠ 1, pC[t 0; ∞), p(t) > 0 for tt 0, τC[t 0; ∞), limt→∞ τ(t) = ∞, τ(t) < t for tt 0. Every eventually positive solution x(t) satisfying limt→∞ x(t) ≧ 0. The structure of solutions x(t) satisfying limt→∞ x(t) > 0 is well known. In this paper we study the existence, nonexistence and asymptotic behavior of eventually positive solutions x(t) satisfying limt→∞ x(t) = 0.
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Speciation and solubility of neptunium were studied using paper electrophoresis, ion exchange and ultrafiltration. Among these methods, the paper electrophoresis was found to be suitable for measuring speciation and solubility of neptunium of low concentration, if chemical species had opposite charge each other or dissolved species had a charge. Using paper electrophoresis, hydrolysis constants of NpO2OH0 and NpO 2 (OH) 2 and solubility product of NpO2 were obtained and ionic-strength dependence of speciation was observed.

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High resolution-type ICP-MS was applied to the analysis of 239Pu and 240Pu in soil samples. The detection limit of Pu was about 0.001 pg.ml-1 (ppt) in the sample solution or about 0.0005 pg in a total sample. This method was used to determine concentrations of Pu and its isotopic ratios in several soil samples collected from different areas in Japan. Concentrations of Pu in surface soils collected from forests were significantly higher than those in soils from agricultural fields. The 240Pu/239Pu atom ratios observed were usually 0.17-0.19, except for one very low ratio (0.037) found in the Nishiyama area (Nagasaki).

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The coextraction equilibrium of technetium(VII) and uranium(VI) from nictric acid solution was studied in a system involvingn-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) in decalin. Stoichiometry of technetium, uranium and CMPO in the Tc-U-CMPO complex was obtained from the distribution data by slope analysis. The results indicated that the enhanced extraction of technetium was caused by the formation of UO2NO3TcO4·nCMPO (wheren=2 and/or 3). It was found that this coextraction of technetium with uranium was well explained by using ion exchange reaction between UO2(NO3)2·2CMPO complex and TcO 4 .

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In order to be more confident of the performance assessment of high-level radioactive waste disposal, radionuclide transport must be investigated in more detail in the disturbed host rock region adjacent to the engineered barriers where disturbance has been introduced during the construction and waste-emplacement period. Geochemical, hydrological, and rock-mechanical properties should be quite different from those of undisturbed host rock. We have to elucidate the effect of bentonite intrusion into intersecting fractures from the standpoint of radionuclide confinement. In the present work, sorption distribution ratios (Kd's) of Np and Am are measured experimentally for various values or redox potential (Eh) in a simulated rock fracture filled with bentonite. The Kd of Am is approximately 6.5×103 ml/g and found to be insensitive to the redox potential. Under anaerobic conditions, the Kd of Np is approximately 6×104 ml/g. Under aerobic conditions, Kd is as small as 30 to 100 ml/g. This is the first report to measure the sorption behavior of Np and Am in a simulated rock fracture filled with bentonite (namely, in a disturbed zone) under pH, Eh and ionic strength control. We aan make use of these Kd data for numerically evaluating the mass transfer from bentonite filled fractures into the water-flowing fracture network1.

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Positron annihilation lifetime measurements of PMMA, PEMA, PiPMA, PnPMA and PnBMA were performed in the temperature range between 15 and 300 K, where , and relaxational transitions occur for these polyalkylmethacrylates. The variations of free volume size and content calculated from the longest lifetime component against temperature are correlated to the results obtained by dielectric, viscoelastic and dynamic mechanical relaxation data of the polymers. The variations of free volume sizes and contents, apparent free volume fraction and size distribution of the polyalkylmethacrylates are well correlated with the rotational transitions of side chains. The location of free volumes, in which positronium annihilates can be estimated near the vicinity of alkyl groups bound to oxygen atom of side ester chains.

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The hemispherical total emissivity of partially stabilized zirconia has been obtained by a spectral analysis of the normal emission spectra between 400–850 K. Thermal conductivity was evaluated with this emissivity and temperature gradient in the sample. Effects of the scattering of the radiation in a ceramic sample are also investigated. In addition, specific heat capacity was measured by thermal radiation calorimetry. Current results are compared with those reported for tetragonal zirconia with the same yttria content and for monoclinic phase.

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A systematic and non-destructive technique is proposed for the determination of boron in coral samples by neutron-induced prompt γ-ray analysis (PGA) using a thermal neutron guide beam of the JRR-3M reactor. About 50–150 mg samples in sealed FEP film were irradiated and measured for 5000 s in the PGA system at a neutron flux of 2.4 × 107 n cm−2 s−1. In order to determine B content in coral skeletons, the Doppler-broadened γ-ray peak of 478 keV (10B) was used together with the correction of interference from the Na-peak of 472 keV. The analytical precision was ~3% for the JCp-1 coral standard. The data (n = 56) obtained by the present method showed a range of B content from 40.7 to 76.9 ppm which is similar to reported values. Boron in corals showed the highest levels in Rukan-sho (Okinawa) with an average B content of 62.5 ppm, whereas corals collected from Mizugama (Okinawa), Cebu (the Philippines) and Khang Khao (Thailand) exhibited B contents of 56.5, 53.0 and 45.7 ppm, respectively. The uptake of boron by living corals may be influenced by seawater pH related to higher seawater B(OH)4 . In this paper we discuss factors controlling the B levels in corals.

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