Toshiaki Iida

Solutions of the Yang-Yang Integral Equation at Zero-Temperature

Presented are solutions of the Yang–Yang integral equation for a one-dimensional system of bosons with repulsive δ-function interaction at zero temperature. By use of a method proposed in the previous paper, the first few terms of the asymptotic expansions of the excitation spectrum for both strong and weak coupling cases are calculated explicitly.

Exact Analysis of δ-Function Attractive Fermions and Repulsive Bosons in One-Dimension

The Gaudin integral equation for the ground state of a one-dimensional δ-function attractive spin-1/2 fermions is solved in the form of power series. The first few terms of the asymptotic expansions for both strong and weak coupling cases are calculated analytically. The physical quantities such as the ground state energy are expressed in terms of a single dimensionless parameter γ= c / D , where c is the coupling constant and D is the number density. The results agree with those obtained from the perturbation calculations, which include the one in the classical electrostatics originally by Kirchhoff. In the strong coupling limit, the connection to the solutions of the Lieb–Liniger integral equation for the ground state of a one-dimensional δ-function repulsive bose gas is shown explicitly.

Exact Analysis of a δ-Function Spin-1/2 Attractive Fermi Gas with an External Magnetic Field

We study the excitation spectrum of a one-dimensional δ-function attractive spin-1/2 fermions by the thermal Bethe ansatz method at zero temperature. The integral equation for the dressed energies of the system with an external magmatic field is solved in the form of power series. The first few terms of the asymptotic expansions for both strong and weak coupling cases are calculated analytically. We also study the magnetization as a function of the coupling constant and the external field.

Thermal conductivity study of thin He films adsorbed in porous glasses with well controlled pore sizes

Thermal conductivity study of thin He films adsorbed in porous glasses with well controlled pore sizes[2] is reported. The measurements are performed in a cell where a torsional oscillator monitors the superfluid density change, for the same films for comparison. Since the heat flux through the superfluid is proportional to the superfluid velocity, we discuss the possible observation of the intrinsic critical velocity vsl = h/ml, inherent in superfluid He films in such porous systems with unit pore length l, as discussed by Minoguchi and Nagaoka[3], which marks the velocity at which phase slippages start to occur over macroscopic scales.

Contribution of ICT Monitoring System in Agricultural Water Management and Environmental Conservation

Recently, ICT based monitoring system is popularized in some agricultural areas. In such area, farmers can obtain their paddy conditions by using smart phone without going to the paddy. In this study, the effect of ICT based monitoring system on water and labor saving, and nutrient loads reduction was evaluated. Then, cost/benefit of monitoring system installation was compared. Finally, how to promote ICT systems in agricultural engineering field was discussed based on the characteristic of agricultural water management system.

Statistical Mechanics of Quantum Integrable Systems

Recent developments in statistical mechanics of quantum integrable systems are reviewed. Those studies are fundamental and have a renewed interest related to newly developing fields such as atomic Bose-Einstein condensations, photonic crystals and quantum computations. After a brief summary of the basic concepts and methods, the following three topics are discussed. First, by the thermal Bethe ansatz (TBA), a hard-core Bose gas is exactly solved. The model includes fully the effect of excluded volume and is identified to be a c=1 conformal field theory. Second, the cluster expansion method based on the periodic boundary condition for the Bethe wave function, which we call the Bethe ansatz cluster expansion (BACE) method, is developed for a δ-function gas and the XXX Heisenberg chain. This directly proves the TBA and reveals intrinsic properties of quantum integrable systems. Third, for a δ-function gas, the integral equations for the distribution functions of the quasi-momentum and the quasi-particle energy are solved in the form of power series. In the weak coupling case, the results reproduce those of Bogoliubov theory.

Seasonal characteristics of surface water quality in the wastewater catchment system of an urbanizing basin

Vientiane, Lao PDR, has been subject to extensive and ongoing urbanization plans, including development of natural marshes and residentialization of paddy fields into suburban areas, despite natural marshes playing a vital role in treating wastewater from urban areas. Therefore, it is important to understand the current situation regarding the nutrient balance in these natural wastewater treatment systems to predict future conditions and design appropriate measures against water quality deterioration. However, limited data are available in Vientiane on the hydrological characteristics of water and nutrient runoff that flow into marshes through drainage canals. In this study, we conducted a periodic survey of drainage canals and Mak Hiao River in the wastewater catchment system surrounding Vientiane during the rainy and dry seasons. We monitored the discharge of surface water at 21 observation sites and analyzed water quality of nitrogen, phosphorus, and total organic carbon. These observations revealed that the concentrations of dissolved nitrogen and phosphorus were significantly higher at sites in urban areas, followed by sites in the main river basin and those in agricultural areas. Dissolved nitrogen and phosphorus concentrations varied with runoff discharge, especially in urban and river basin sites, with lower concentrations in the rainy season and higher concentrations in the dry season. On the other hand, we found no significant differences between the rainy and dry seasons in nutrient concentrations in the agricultural basin. Finally, we proposed measures to counteract the deterioration of water quality during dry seasons and simulated the impact of these measures.

Reduction of Air Radiation Dose by Ponding Paddy Fields

Radioactive cesium (Cs) released by nuclear accidents is sorbed and fixed onto soil surfaces, which then radiate strong gamma rays (γ-rays). Decontamination around dwelling areas is now eagerly being implemented but more efforts are necessary to reduce the air radiation dose. Paddy field ponding, from the viewpoint of cost-effectiveness, is considered to be an effective practice for reducing the air radiation dose in the environment. In this study, field experiments were conducted at Sasu and Komiya regions in Iitate Village to verify the effectiveness of paddy field ponding, and numerical experiments were also conducted using the formula for uncollided γ-ray fluxes passing through the shield material.

Analysis of Value Co-creation Between Farmers and Land Improvement District in Japan Through Irrigation Service Improvement by Good Water Quality

In Japan, agricultural sector including rice production has several problems that are complex of farmers aging, small scale farming, and high cost management. To improve this situation, Japanese government pushed to increase efficiency to change high profit production or large scale agriculture. In this research, objectives is analyzed that farmer’s acceptability of new innovative irrigation water distribution technology to improve rice quality as high profitable production. As a methodology, water quality control management was assumed in a good rice quality control scenario for Agent Based Model (ABM). In water quality management for rice production, former research results showed that when nitrogen water quality was higher after flowering in rice growth stage, nitrogen concentration and protein contents ratio was increasing, then, taste of rice was decreasing. In study area as an example of application, Imbanuma basin is chose as high nitrogen concentration area. As results, the modified ABM was applied that farmer’s preference would be no change in prior the cost, and if new irrigation would be accepted the profit would be higher than a threshold, though interview results for farmers were more complicated because of cost, profit, and risk management.