岡山大学環境理工学部 Acta Medica Okayama 1341-9099 12 1 2007 Numerical study of biodegradation of xenobiotic polymers based on exogenous depolymerization model with time dependent degradation rate 1 6 EN Masaji Watanabe Fusako Kawai A mathematical model for exogenous depolymerization with time dependent degradation rate is analyzed in order to study the biodegradation of polyethylene glycol. The weight distribution with respect to the molecular weight before and after cultivation of microorganisms were analyzed an inverse problem to determine the time dependent degradation rate. Numerical techniques to solve the inverse problem and to simulate the transition of the weight distribution are described. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 11 1 2006 Numerical Techniques for Simulation of Tsunami Based on Finite Elements 15 18 EN Masaji Watanabe Numerical techniques to simulate tsunamis are described. Partial differential equations are reduced to a system of ordinary differential equations to which appropriate numerical solvers can be applied. The techniques are illustrated with an example in which tsunami due to an earthquake is simulated. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 9 1 2004 Experimental and Computational Water Analysis for Kojima Lake 53 58 EN Masaji Watanabe We study a wind-generated current in Kojima Lake. We introduce an experimantal result which was obtained using a float equipped with a GPS unit. We also present a result of numerical study in which a result from finite element analysis of flow is applied to the momentum equation of the float to simulate its motion. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 9 1 2004 実験と計測に基づく密度流拡散装置の効果に関する考察 59 64 EN Masaji Watanabe Toshio Yamatogi The density current generator (Manufacturer: Nakashima Propeller Co., Ltd., Patent owner: Hitachi Metals, Ltd.) is designed to generate vertical circulation over a wide water area harnessing the density current effect. We present some experimental results that we obtained using a float equipped with a GPS unit to study water flows generated by a density current generator unit set in S-Reservoir in Okayama Prefecture. We also present some measured results concerning the water temperature around the unit. We discuss its effects observing the experimental results and the measured results. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 10 1 2005 Computational Analysis of Currents Generated in Kojima Lake Based on Updated Topographical Data 23 28 EN Masaji Watanabe Topographical data of Kojima Lake have been updated by applying data obtained after dredging. Together with tide level of Kojima Bay and water levels of Kurashiki River and Sasagase river, the information was incorporated in computational analysis of unsteady flows generated in the lake when the water was discharged from Kojima Lake to Kojima, Bay. A finite element method was applied to equations governing unsteady flows, and the transition of discharge was obtained. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 8 1 2003 An Experimental Study of Unsteady Flows Generated in Kojima Lake 23 26 EN Masaji Watanabe The global positioning system (GPS) is utilized for analysis of flows in the water environment. A float equipped with a GPS unit is designed to drift on the surface of the water. Its driving force is the fluid resistance exerted on a pair of rectangular plates. While it travels over the surface, the GPS unit evaluates its position every second, and spatiotemporal data that specify its motion are transmitted to be recorded. Results of experiments conducted to study unsteady flows generated in Kojima Lake are introduced. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 6 1 2001 An Experimental Evaluation of Lake Flow Simulation 11 15 EN Masaji Watanabe Shigeyuki Kunisada The global positioning system is utilized in lake flow analysis to facilitate experimental evaluation for numerical results of a lake flow simulation. In our lake flow experiment a float travels on the lake surface receiving the fluid resistance due to lake flow, while a global positioning system receiver keeps track of its position. A momentum equation is derived when the product of the float mass and its acceleration is set equal to the driving force. The temporal change in the position of the float can be simulated when numerical solutions of lake flow equations are given. A comparison of numerical results and experimental data leads to an evaluation of the numerical simulation of lake flow. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 7 1 2002 A Numerical Analysis and an Experimental Study of an Unsteady Flow in Kojima Lake 39 44 EN Masaji Watanabe We present some results of a finite element analysis for an unsteady flow in Kojima Lake. We also present an experimental result. The global positioning system was utilized in the experiment in order to record the temporal and the spatial data of a float traveling with the driving force of the fluid resistance. The spatial and temporal data were recorded to examine their correspondence with analytical results. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 3 1 1998 A numerical analysis of slow oscillations in dynamics of coupled systems 11 24 EN Masaji Watanabe We study a system that models a problem in which an oscillatory unit is coupled to a passive medium. We analyze the case in which an RCL circuit is coupled to an RC circuit. Some numerical results indicate when slow oscillations occur in coupled systems. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 5 1 2000 A Numerical Analysis of Unsteady Flow in Kojima Lake 31 34 EN Masaji Watanabe We study unsteady flow that models lake flow in Kojima Lake. We assume that a lake is connected to another area with gates, and that those gates are opened when the water level outside the gates is lower than the water level of the lake. We study unsteady flow due to the opening of the gates. We analyze the problem with the finite element method, and take detailed structures of the gates into account. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 2 1 1997 On Long-Period Oscillations in Coupled Systems of Nonlinear Oscillators and Stationary Systems 19 24 EN Masaji Watanabe We study a system obtained by coupling a nonlinear oscillator and a stationary system. We analyze the dynamics in a singular limit and show that asymptotically orbitally stable periodic solutions can exist. We also show how a slow oscillation can arise in the coupled system. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 1 1 1996 Computational water analysis in an artificial lake: Kojima Lake case 47 53 EN Toru Sasaki Hirofumi Ishikawa Tsuyoshi Kajiwara Masaji Watanabe We treat the problem of water pollution by the method of a mathematical model. We illustrate the method of analysis with Kojima Lake. We analyze in-flow and out-flow of the lake, compute numerical solutions of the governing equations of the water flow and the pollutant. The simulation leads to the conclusion concerning the figure of Kojima Lake. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 1 1 1996 On Resonance in Periodically Forced Oscillators and Coupled Systems of Excitable Systems and Nonlinear Oscillators 55 64 EN Masaji Watanabe We analyze some mathematical problems that arise in studies of phenomena observed in the cardiac action. We illustrate a method to characterize the response of a nonlinear oscillator to an external forcing, and introduce some numerical results. We also introduce some results of numerical computation in an example of a coupled system of an excitable system and a nonlinear oscillator. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 13 1 2008 Numerical Study of Effects of Tsunami Wave Generated on Nankai Trough 57 62 EN Shinya Sumida Kazuhiro Yamamoto Masaji Watanabe Numerical techniques to simulate tsunami waves are described, and numerical results are introduced. A finite difference method is applied to shallow water equations to analize the propagation of tsunami wave. Numerical results to simulate a tsunami wave generated on the Nankai Trough are introduced. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 4 1 1999 Circadian Oscillations in Systems of Biochemical Oscillators Coupled to Stationary Systems 1 6 EN Masaji Watanabe According ot previous studies, we may expect that slow oscillations can occur in dynamics of a parameterized family of systems in which a biochemical oscillator is coupled to a stationary systems. We introduce some numerical results that confirm our expectation. The results suggest that it is possible for slow oscillations to occur in dynamics of a system in which an active oscillatory unit is coupled to a passive medium, and that it is possible for circadian oscillations to arise from fast glycolytic oscillations in such a coupled system. No potential conflict of interest relevant to this article was reported.

岡山大学保健環境センター環境安全部門 Acta Medica Okayama 0917-1533 26 2004 数値シミュレーションによるポリエチレングリコール生分解性解析 17 22 EN Masaji Watanabe Fusako Kawai We examined the biodegradability of polyethylene glycol by analyzing gel permeation chromatography patterns, which were obtained before and after cultivation of a microbial consortium E-1 in culture media containing polyethylene glycol as its sole carbon source. We solved an inverse problem of the initial value problem, which consists of an exogenous depolymerization model and the initial weight distribution, in order to determine an oxidation rate, for which the solution of the initial value problem also satisfies the final condition. Given the oxidation rate, we simulated the transition of the weight distribution solving the initial value problem. We interpret the result that reflects a physical significance of the molecular weight on the oxidation rate, and reach a conclusion concerning the role of the membrane transport in exogenous depolymerization processes. No potential conflict of interest relevant to this article was reported.

岡山大学環境管理センター Acta Medica Okayama 0917-1533 25 2003 実験結果と数値シミュレーションによるポリマー生分解性解析 25 32 EN Masaji Watanabe Fusako Kawai We describe techniques that we developed previously in studies of biodegradation of polymeric compounds. We present some experimental results concerning biodegradation of polyethylene. We introduce a mathematical model that govern the evolution of the weight distribution, and show how its inverse problem can be analyzed. We also introduce a mathematical model that governs the evolution of the weight distribution of polymeric compound subjected to enzymatic degradation, and present some numerical results concerning enzymatic degradation of polyvinyl alcohol. No potential conflict of interest relevant to this article was reported.

American Institute of Physics Acta Medica Okayama 0094-243X 1707 2016 Numerical study on anaerobic digestion of fruit and vegetable waste: Biogas generation 050017 EN Puteri Kusuma Wardhani Graduate School of Environmental and Life Science, Okayama University Masaji Watanabe Graduate School of Environmental and Life Science, Okayama University The study provides experimental results and numerical results concerning anaerobic digestion of fruit and vegetable waste. Experiments were carried out by using batch floating drum type digester without mixing and temperature setting. The retention time was 30 days. Numerical results based on Monod type model with influence of temperature is introduced. Initial value problems were analyzed numerically, while kinetic parameters were analyzed by using trial error methods. The numerical results for the first five days seems appropriate in comparison with the experimental outcomes. However, numerical results shows that the model is inappropriate for 30 days of fermentation. This leads to the conclusion that Monod type model is not suitable for describe the mixture degradation of fruit and vegetable waste and horse dung. No potential conflict of interest relevant to this article was reported.

American Institute of Physics Acta Medica Okayama 0094-243X 1707 2016 Mathematical Formulation and Numerical Simulation of Bird Flu Infection Process within a Poultry Farm 050013 EN Arrival Rince Putri Graduate School Environmental and Life Science, Okayama University Tertia Delia Nova Andalas University Masaji Watanabe Graduate School Environmental and Life Science, Okayama University Bird flu infection processes within a poultry farm are formulated mathematically. A spatial effect is taken into account for the virus concentration with a diffusive term. An infection process is represented in terms of a traveling wave solutions. For a small removal rate, a singular perturbation analysis lead to existence of traveling wave solutions, that correspond to progressive infection in one direction. No potential conflict of interest relevant to this article was reported.