Atsuyuki Suzuki

Observation of a single-beam gradient-force optical trap for dielectric particles in air

A single-beam gradient-force optical trap for dielectric particles, which relies solely on the radiation pressure force of a TEM(00)-mode laser light, is demonstrated in air for what is believed to be the first time. It was observed that micrometer-sized glass spheres with a refractive index of n=1.45 remained trapped in the focus region for more than 30 min, and we could transfer them three dimensionally by moving the beam focus and the microscope stage. A laser power of ~40 mW was sufficient to trap a 5- microm -diameter glass sphere. The present method has several distinct advantages over the conventional optical levitation method.

Theoretical Gibbs free energy study on UO2(H2O)n2+ and its hydrolysis products

Abstract Hydration of uranyl ion (UO 2 2+ ) in aqueous system was investigated using hybrid density functional theory B3LYP method. Gibbs free energies and solvation energies for different UO 2 (H 2 O) n 2+ ( n =4, 5, and 6) (including the first and the second solvation shell) clusters were calculated. Polarized continuum model (PCM) was used to calculate the solvation energy. The results show that the hydration number of UO 2 2+ in liquid phase is 5. The hydrolysis reactions of UO 2 (H 2 O) 5 2+ were investigated. The temperature and pressure effects on the reaction energies were studied. It was found that temperature and pressure significantly changed the equilibrium constants of hydrolysis reactions.

SVM-Based feature selection of latent semantic features

Latent Semantic Indexing (LSI) is an effective method to extract features that captures underlying latent semantic structure in the word usage across documents, However, subspace selected by this method may not be the most appropriate one to classify documents, since it orders extracted features according to their variances, not the classification power. We propose to apply feature ordering method based on support vector machines in order to select LSI-features that is suited for classification. Experimental results suggest that the method improves classification performance with considerably more compact representation.

Use of Real Options in Nuclear Power Plant Valuation in the Presence of Uncertainty with CO2 Emission Credit

The purpose of this study is to analyze the value of an investment in power generation assets that do not emit CO2, by using a real option model. This study evaluates the effects of future uncertainty on investment decision-making, by focusing on the uncertainty of CO2 emission credits [yen/t-CO2 in the fairly near future in Japan. Electric utilities are required to keep plans to prepare for various future uncertainties such as the price of CO2 emission credits. The real option approach can evaluate the option value of decision-making under uncertainty. This study examined the option value of a power plant [yen/KW] to evaluate the effects of an externality under uncertainty. The results showed that nuclear power would have the most value under the forthcoming CO2 emission limitations. In order to secure the effectiveness of measures against global warming, we should reconsider the roles of nuclear power plants in Japan. Finally, the real option model is shown to be an effective candidate for a decision-making support tool to deal with problems in energy environmental policy.

A.c. magnetic properties of YBaCuO bulk superconductor in high Tc superconducting levitation

Abstract High T c melt-processed YBaCuO bulk superconductors have been utilized for the development of high T c superconducting magnetic bearings and flywheels. In such systems the superconductors are exposed to an a.c. magnetic field with frequencies of 100 Hz to 10 kHz during rotation of the rotor where the permanent magnet rings are installed. The a.c. magnetic field is caused by inhomogeneity of the magnetic field generated by the magnet in the azimuthal direction. Here the decay of rotational speed, termed rotational loss, becomes a very serious technical problem. In this paper, we analyse the a.c. magnetic properties of high T c superconductors in the above frequency range using a fundamental experiment and numerical simulation based on the flux flow and creep model and, in addition, we elucidate the mechanism of energy dissipation which causes the rotational loss.

Analysis of the decision to invest for constructing a nuclear power plant under regulation of electricity price

In this study, the effect of the regulation of electricity prices on the decision to invest in power plants is rationally explained using a real-options approach. Conditions under price regulation are described by a simple model in which the variable cost follows a stochastic process; free market conditions are described using Cortazars model. The resulting comparison could explain the promotion of nuclear power plant construction in Japan from about 1980 until the middle of the 1990s, and the avoidance of such investment in recent years. This difference between economic environments is not confirmed by the traditional net present value (NPV) approaches.

Affinity of finely dispersed montmorillonite colloidal particles for americium and lanthanides

We studied (i) the affinity of the finely dispersed montmorillonite colloidal particles (<0.45 μm), which originated from Japan, for trace amounts of Am3+ and lanthanide ions (Ln3+: Nd3+, Eu3+, Gd3+), and (ii) the differences between the sorption behavior of Am3+ and Ln3+ onto the colloidal particles and that onto the massive montmorillonite solids. The ion-exchange stoichiometry of sorption reaction of Am3+ and Ln3+ onto the colloidal particles was 1:3 in the low Na+ concentration region. In the high Na+ concentration region, the sorption ratio was constant, and specific for Am3+ and each Ln3+. The influence of Na+ and Ca2+ on the sorption of Ln3+ onto the finely dispersed Na- and Ca-montmorillonite colloidal particles at different NaCl and CaCl2 concentrations was examined. It was found that the coverage of the sorption sites increased with the Ln3+ concentration. The affinity for Ln3+ was discussed by selectivity and a Langmuir-type isotherm.

Diffusion of the 241Am → 237Np Decay Chain Limited by Their Elemental Solubilities in the Artificial Barriers of High-Level Radioactive Waste Repositories

A mathematical analysis of the diffusion of the [sup 241]Am [r arrow] [sup 237]Np decay chain in the artificial barrier of a high-level radioactive waste repository is presented. First, analytical solutions obtained are for the space- and time-dependent concentration of [sup 241]Am in the artificial barrier and the time-dependent amount of americium precipitated at the surface of the waste glass, based on the assumption of the congruency of the radionuclides with solubility-limited dissolution of the glass matrix. The effects of solubility sharing with coexisting [sup 243]Am are considered. Transport and precipitation of [sup 237]Np in the artificial barrier are analyzed by dividing the time domain into a small time domain, where the [sup 241]Am concentration is so large that [sup 237]Np precipitation is dominant, and a large time domain, where the [sup 241]Am becomes negligible and the precipitation region shrinks by diffusion from the precipitation front. The equation for the movement of the precipitation front is obtained. As the overpack lifetime increases, the effect of neptunium precipitation becomes less significant. With a lifetime longer than [approximately]6000 yr, an earlier model, where neptunium is treated as a mother nuclide and the precipitation occurs only at the glass surface, can be used.

Chloride concentration and temperature effects on the hydration of Th(IV) ion: a molecular dynamics simulation

Abstract Molecular dynamics simulations have been performed to investigate the structural and dynamical properties of the second hydration shell of Th 4+ ion at various chloride concentrations and temperatures. When the concentration increases (ca. 5 M), the hydration of Th 4+ ion involves the displacement of the water molecules by Cl − ligand and slightly decreases the total coordination number. The residence time of water molecules in the second hydration shell decreases as a function of increasing solution temperature.

Sorption of neptunium on bentonite and its migration in geosphere

Abstract Firstly, sorption of Np(IV), which is dominant under the anaerobic conditions such as under the deep geologic conditions, onto the bentonite is investigated by batch experiment at pH=6–10. It is found that the sorption ratio of Np(IV) increases with pH, reaches at maximum around pH=8.5, and then decreases. Secondly, diffusion of Np(IV) in compacted bentonite with a dry density of 1.0 g/cm 3 is studied. From the diffusion profiles of Np(IV), the apparent diffusion coefficients are evaluated as (6–9)×10 −15 m 2 /s. Thirdly, the effect of formation of Np(IV)-bearing bentonite colloid on the migration of Np(IV) is investigated by column experiment using a quartz-packed column. While Np(IV) ions in the absence of colloid are strongly retarded in the column, ≈75% of Np(IV) injected into the column are recovered in the presence of colloid.