Yooko Tsuchiya

Prediction of the melting point of n-alkanes using the molecular dynamics method

We report the melting point of normal alkanes, from molecular dynamics calculations using the NPT ensemble. From the radial distribution function reflecting the arrangement of carbons, the solid–liquid phase transformation was identified in calculating a melting point in good agreement with the measured value. The effectiveness of periodic boundary conditions in the molecular dynamics calculations was also confirmed.

Inorganic elements in typical Japanese trees for woody biomass fuel

The inorganic element contents of trees were measured to evaluate the safety of using wood biomass as thermal power generation fuel. Twelve species of typical conifer trees and 17 species of typical broad-leaved trees in Japan plus 9 species of commonly imported trees were selected and analyzed for the main inorganic elements and several trace elements that are potentially harmful in combustion ash. The ash content in bark, especially in the inner bark, was higher than that in wood, but the highest concentration was in the leaves. In almost all parts of the trees, the order of inorganic element concentration was calcium ≥ potassium ≥ magnesium ≥ sulfur ≥ phosphorous. Among the trace elements, the boron content was high and the mercury content was recorded as being high in conifer bark.

Effect of freeze-thaw repetitions upon the supercooling release ability of ice-nucleating bacteria.

We have studied the durability of ice-nucleating bacteria with a potent supercooling release capacity through repeated freeze-thaw cycles. Through experiment, we confirmed that UV sterilized Erwinia ananas maintains a superior supercooling release capacity at around -1 degrees C through 2000 freeze-thaw cycles. We also found that gamma-ray sterilization, which is more suitable than UV for large-scale sterilization treatment, has a similar effect at appropriately selected doses.

Prediction of Thermal Properties and Effect of OH Substituent for Poly(vinyl alcohol)s by Molecular Dynamics Calculations

Since heat storage technology contributes greatly to the effective use of energy, we are attempting to develop latent heat storage materials. If computer simulations enable the estimation of material properties prior to experiments, they will provide us with very effective tools for the development of new materials. We use molecular dynamics calculations to predict the melting points and latent heats of fusion, which are crucial thermal properties for evaluating the suitability of heat-storage materials. As the object of calculation, poly(vinyl alcohol) (PVA) was chosen, because polymer materials are effective in that they can be made to cover all temperature ranges by changing the molecular weight. The melting points were determined from the volume change, and the latent heats of fusion were determined from the internal energy. As for these calculations, it was ascertained that these thermal properties were suitable values in comparison with the results of actual calorimetry. From the comparative calculation of the polymer consistent force field (PCFF) and optimized potentials for liquid simulations (OPLS) force field, it was shown that the intermolecular potential could be simplified. Moreover, the stability of the structural isomer of PVA and the state of the hydrogen bond were evaluated, because a strong intermolecular bond leads to structural stability and a high melting temperature.

Prediction of the latent heat of n-alkanes using the molecular dynamics method

With the ultimate goal of developing thermal storage materials by means of computer simulation, we attempt to predict a materials melting point and latent heat of fusion, both of which are important properties for evaluating a thermal storage material. Molecular dynamics calculations using the NPT ensemble were performed to investigate the melting process of n-alkanes having carbon numbers of 8 to 18. A technique for determining the melting point from a radial distribution function that reflects the arrangement of carbon atoms has already been reported. Based on our previous study, we attempted to predict the latent heat of fusion from the internal energy. A calculation method that reflects the actual melting phenomenon was used and a precise value for the qualitative tendency of the latent heat was obtained.