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Ishida H.,Nagaoka National College of Technology
Journal of Fire Sciences | Year: 2011

The propagation of a flame tip in an assisted flow along the high-temperature ground soaked with high-volatile liquid fuel was studied experimentally from the point of view of a fundamental study on the fire hazard prevention in many fuel spill accidents. The effects of flow velocity on the flame tip propagation and on the motion of flammable gas layer were investigated experimentally. The study revealed the interesting and characteristic dependence of the propagation velocity of the flame tip on the flow velocity, which is classified into three regions by the ratio of the flow velocity about 1 mm above the ground surface to the flame propagation velocity with no surrounding airflow. The flame tip blows off and no flame propagation occurs when the ratio is over about 1.5, which agrees with the blow-off of spreading flame in an opposed flow, described in detail in our previous study. The flame tip propagation in an assisted flow strongly depends on the formation of a flammable gas mixture downstream of the flow. © The Author(s), 2010.


Matsunaga S.,Nagaoka National College of Technology
Molecular Simulation | Year: 2012

Molecular dynamics simulation has been performed to investigate the dynamical and thermodynamic properties of the superionic and molten phases for (Ag x Cu 1-x)Br of x<0.5, which contains two kinds of cations, Ag + and Cu +. Ag + and Cu + ions show different transport and dynamical properties in superionic phase. Their frequency distributions are found in the infrared region. The concentration-concentration structure factor, Sc ic j(q), has also been evaluated. © 2012 Copyright Taylor and Francis Group, LLC.


Matsunaga S.,Nagaoka National College of Technology
International Journal of Molecular Sciences | Year: 2015

A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawatr. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence of thermal conductivity, have been observed in the higher-pressure region. © 2015 by the authors; licensee MDPI, Basel, Switzerland.


Katagiri H.,Nagaoka National College of Technology
ICP 2012 - 3rd International Conference on Photonics 2012, Proceedings | Year: 2012

In 1988, K. Ito and T. Nakazawa of Shinshu University succeeded in fabrication of Cu2ZnSnS4 (CZTS) thin films by an atom beam sputtering method and confirmed that CZTS has suitable optical properties for thin film solar cells. In 1995, we began to develop the novel thin film solar cells using CZTS as an absorber to be able to use in the after next generation. The conversion efficiency of CZTS thin film solar cells reported for the first time in 1996 was only 0.66% and it have been improved to 6.77% in these twelve years at our laboratory. Quite recently, IBM using CZTSSe that contain Se to some extent achieved the conversion efficiency of over 10%. Because the potential of CZTS-based thin film solar cells seems to be quite high, we will be able to overcome the resource problem of rare-metal in the near future. In this talk we will survey our previous works and show the recent results concerning with this promising solar cells. © 2012 IEEE.


Zanganeh J.,University of Newcastle | Moghtaderi B.,University of Newcastle | Ishida H.,Nagaoka National College of Technology
Progress in Energy and Combustion Science | Year: 2013

Fires caused by accidental spillage of flammable liquids have been a major safety concern in industries and urban areas. There has been a recent surge of interest in the research concerning the combustion and flame spread over an inert porous media soaked with flammable liquid. This interest has been driven by the need to better understand fire and its behaviour under these conditions and improve the relevant fire safety and prevention technologies. A review of key studies in this subject area has been conducted and summarised, focussing mainly on the theory plus a notable experimental findings about combustion and the flame spread phenomena of fuel-soaked porous media. The review covers topics such as flame spread behaviour, physical flame propagation aspects, heat transfer, temperature distribution; and fuel consumption over inert porous media. The review concludes with some practical safety and environmental considerations for decontamination of land soaked with flammable liquid. © 2013 Elsevier Ltd. All rights reserved.


Ishida H.,Nagaoka National College of Technology
Journal of Fire Sciences | Year: 2012

From the point of view of a fundamental study on flame propagation along ground soaked with high volatile liquid fuels, the effect of an entrained flammable mixture by airflow toward theignition location on traveling of a flame tip along the fuel-spillage area was studied. The thickness of flammable mixture layer is about one tenth of that of velocity boundary layer ofthe airflow. After the onset of ignition, the flame tip travels through the thin flammable mixture layer in the airflow with large velocity gradient. The effect of airflow velocity on the traveling of flame tip (both of upstream and downstream) was investigated. The dependence of the flame tip traveling on the airflow velocity is classified into some regions by the ratio of the airflow velocity about 1mm above the ground surface to the flame propagation velocity with no surrounding airflow. The critical airflow velocity for the blowoff of flame tip (upstream and downstream) strongly depends on the quantity of flammable mixture entrained toward the ignition location by the airflow. © The Author(s) 2011.


Matsunaga S.,Nagaoka National College of Technology
Physics and Chemistry of Liquids | Year: 2013

Phonon propagation in molten RbAg4I5 is discussed based on the partial dynamic structure factors Sξη(k,ω), which are obtaisned by molecular dynamics (MD) simulation using pair potentials considering the effect of polarisability of ions. The longitudinal acoustic (LA) and transverse acoustic (TA) modes have been observed in molten RbAg4I5, which are found to be propagated mainly by the different ions: LA mode by I ions and TA mode by Ag ions. The origin of the TA phonon mode is attributed to the cation-cation interaction. The electrical properties, the electron density of states, the band structure, etc., are also examined by ab initio calculation. The hybridisation of electronic states between ions is enhanced by the existence of Rb ion. © 2013 Copyright © 2013 Taylor & Francis.


Matsunaga S.,Nagaoka National College of Technology
Journal of Physics Condensed Matter | Year: 2010

The theory of the premelting phenomena in ionic crystals on the basis of the concept of the heterophase fluctuation has been applied to the pseudo-binary ionic crystals, KCl-NaCl, AgBr-AgCl and AgBr-CuBr systems. Molecular dynamics simulations (MD) have been performed to examine the ionic configurations in their premelting region in the vicinity of their melting points. Liquid-like clusters have been observed in the results of MD utilizing the Lindemann instability condition. The sizes of liquid-like clusters have been estimated by theory and MD. The characteristics of the dynamical behavior of ions in the premelting region have been examined by the mean square displacement and the velocity correlation functions. © 2010 IOP Publishing Ltd.


Matsunaga S.,Nagaoka National College of Technology
Journal of Physics: Conference Series | Year: 2014

The structure and thermal conductivity of the sodium chloride (NaCl) aqueous solution in similar concentration to the seawater with saturated carbon dioxide (CO2) have been investigated by molecular dynamics simulation. The effects of pressure have been investigated under various pressures corresponding to the depth of the sea from 40m to 10000m. The negative pressure dependence of the thermal conductivity has been detected in the depth of more than 8000m, whereas that of NaCl aqueous solution without CO2 shows the positive pressure dependence. © Published under licence by IOP Publishing Ltd.


Matsunaga S.,Nagaoka National College of Technology
Molecular Simulation | Year: 2013

Molecular dynamics (MD) simulation has been performed in molten RbAg 4I5 using the qualified pair potentials which includes the polarisability of ions. From the obtained results by MD, the partial pair distribution functions and the partial structure factors have been calculated. The results show the significant difference between Rb+ and Ag +. The velocity correlation functions have also been evaluated to examine the dynamical features of constituent ions. © 2013 Taylor & Francis.

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