AIP PublishingActa Medica Okayama0003-6951123232023Water/ice mixture- and freezing-front motion in a non-isothermal liquid bridge231601ENYutakaYamadaFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityKodaiOkanoSchool of Engineering, Okayama UniversityKazumaIsobeFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityAkihikoHoribeFaculty of Environmental, Life, Natural Science and Technology, Okayama UniversityWe experimentally investigate the water/ice mixture- and freezing-front behavior in a water liquid bridge under isothermal and non-isothermal conditions. We find rapid propagation, temporary suspension, and regression of the water/ice mixture front, and finally, it merges with the freezing front when part of the liquid bridge is higher than the freezing temperature. However, freezing-front propagation follows dendritic ice formation, and a protrusion forms at the middle of the liquid bridge as long as the whole liquid bridge is lower than the freezing temperature. We explain those phenomena by quasi-stationary heat-transfer considerations.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama1932-10581752023Diamond quantum sensors in microfluidics technology054107ENMasazumiFujiwaraDepartment of Chemistry, Graduate School of Environmental, Life, Natural Science and Technology, Okayama UniversityDiamond quantum sensing is an emerging technology for probing multiple physico-chemical parameters in the nano- to micro-scale dimensions within diverse chemical and biological contexts. Integrating these sensors into microfluidic devices enables the precise quantification and analysis of small sample volumes in microscale channels. In this Perspective, we present recent advancements in the integration of diamond quantum sensors with microfluidic devices and explore their prospects with a focus on forthcoming technological developments.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama0021-9606156222022Osmotic second virial coefficients for hydrophobic interactions as a function of solute size221104ENHidefumiNaitoDepartment of Chemistry, Faculty of Science, Okayama UniversityRyuichiOkamotoDepartment of Chemistry, Faculty of Science, Okayama UniversityTomonariSumiDepartment of Chemistry, Faculty of Science, Okayama UniversityKenichiroKogaDepartment of Chemistry, Faculty of Science, Okayama UniversityTo gain quantitative insight into how the overall strength of the hydrophobic interaction varies with the molecular size, we calculate osmotic second virial coefficients B for hydrophobic spherical molecules of different diameters in water based on molecular simulation with corrections to the finite-size and finite-concentration effects. It is shown that B (<0) changes by two orders of magnitude greater as increases twofold and its solute-size dependence is best fit by a power law B <jats:sup> </jats:sup> with the exponent ≃ 6, which contrasts with the cubic power law that the second virial coefficients of gases obey. It is also found that values of B for the solutes in a nonpolar solvent are positive but they obey the same power law as in water. A thermodynamic identity for B derived earlier [K. Koga, V. Holten, and B. Widom, J. Phys. Chem. B 119, 13391 (2015)] indicates that if B is asymptotically proportional to a power of , the exponent must be equal to or greater than 6. No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama2158-32261232022Magnetic thickness measurement for various iron steels using magnetic sensor and effect of electromagnetic characteristics035109ENKeijiTsukadaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityMinoruHayashiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityTaiseiKawakamiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityShoyaAdachiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityKenjiSakaiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityToshihikoKiwaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityToshiyukiIshikawaFaculty of Environmental and Urban Engineering Department of Civil, Environmental and Applied System Engineering, Kansai UniversityMohd MawardiSaariFaculty of Electrical and Electronic Engineering, Universiti Malaysia PahangKengoHoriNippon Steel Metal Products Co., Ltd.KazumasaHisazumiNippon Steel Corp. TomonoriTominagaNippon Steel Corp. The diagnosis and prevention of the deterioration of iron-steel infrastructure has become an important social issue in recent years. The thickness measurement technique (extremely low-frequency eddy current testing (ELECT)) using a magnetic sensor for detecting steel corrosion at extreme frequency ranges has been previously reported. Using the calibration curves based on the correlation between the phase of the detected magnetic signal and the plate thickness, the plate thickness reduction caused by corrosion can be estimated from the detected phase signal. Iron-steel materials have large changes in electromagnetic characteristics; therefore, the reference calibration data for each type of iron-steel are required for plate thickness estimation. In this study, the effect of electromagnetic characteristics on the magnetic thickness measurement was investigated to improve the thickness estimation. Four types of iron-steel plates (SS400, SM400A, SM490A, and SMA400AW) with thicknesses ranging from 1 mm to 18 mm were measured by ELECT, and the phase change at multiple frequencies of each plate were analyzed. The shift in the phase and linearity regions of the calibration curves for each type of steel plate was observed. To analyze this shift phenomenon, the electromagnetic characteristics (permeability mu and conductivity sigma) of each type of steel were measured. Compared with the permeability mu and conductivity sigma of each steel plate in the applied magnetic field strength range, the product (sigma mu) for various steel plates decreased in the following order: SM400 > SS400 >SMA400AW > SM490A. The product of mu and sigma is related to the skin depth, indicating the electromagnetic wave attenuation and eddy current phase shift in the material. Therefore, each shift in the calibration curve of each type of iron steel is explained by the changes in the parameters sigma and mu.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama2158-32261172021Design and validation of microfluidic parameters of a microfluidic chip using fluid dynamics75224ENFerozAhmedGraduate School of Natural Science and Technology, Department of Medical Bioengineering, Okayama UniversityYuichiYoshidaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama UniversityJinWangGraduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama UniversityKenjiSakaiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama UniversityToshihikoKiwaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Department of Medical Bioengineering, Okayama UniversityThe internal fluidic parameters of microfluidic channels must be analyzed to solve fundamental microfluidic problems, including microscale transport problems involving thermal analysis, chemical reactivity, velocity, pressure drop, etc., for developing good-quality chemical and biological products. Therefore, the characterization and optimization of the interaction of chemical and biological solutions through microfluidic channels are vital for fluid flow design and engineering for quality assurance in microfluidic platforms. As the internal structures and kinetics of microfluidic channels are becoming increasingly complex, experiments involving optimal fluidic and transport designs are challenging to perform with high accuracy. However, highly integrated simulation tools can guide researchers without specialized computational fluid backgrounds to design numerical prototypes of highly integrated devices. In this study, a microfluidic chip with two inlet wells and one outlet well was fabricated from polydimethylsiloxane following which simulations were performed using an ANSYS Fluent tool influenced by computational fluid dynamics at a nearly identical scale. The pressure drop and velocity profiles of the interaction of two pH buffer solutions (pH 4 and 10) through the designed microfluidic chip were qualitatively estimated from experimental data analysis and validated with the simulation results obtained from the CFD-influenced ANSYS Fluent tool.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama0021-960615492021Formation of hot ice caused by carbon nanobrushes. II. Dependency on the radius of nanotubes094502ENMasakazuMatsumotoResearch Institute for Interdisciplinary Science, Okayama UniversityTakumaYagasakiDivision of Chemical Engineering, Graduate School of Engineering Science, Osaka UniversityHidekiTanakaResearch Institute for Interdisciplinary Science, Okayama UniversityStable crystalline structures of confined water can be different from bulk ice. In Paper I [T. Yagasaki et al., J. Chem. Phys. 151, 064702 (2019)] of this study, it was shown, using molecular dynamics (MD) simulations, that a zeolite-like ice structure forms in nanobrushes consisting of (6,6) carbon nanotubes (CNTs) when the CNTs are located in a triangle arrangement. The melting temperature of the zeolite-like ice structure is much higher than the melting temperature of ice Ih when the distance between the surfaces of CNTs is ∼0.94 nm, which is the best spacing for the bilayer structure of water. In this paper, we perform MD simulations of nanobrushes of CNTs that are different from (6,6) CNTs in radius. Several new porous ice structures form spontaneously in the MD simulations. A stable porous ice forms when the radius of its cavities matches the radius of the CNTs well. All cylindrical porous ice structures found in this study can be decomposed into a small number of structural blocks. We provide a new protocol to classify cylindrical porous ice crystals on the basis of this decomposition.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama2158-32261012020Laser monitoring of dynamic behavior of magnetic nanoparticles in magnetic field gradientENKentaTsunashimaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityKatsuyaJinnoGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityBuntaHiramatsuGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityKayoFujimotoGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityKenjiSakaiGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityToshihikoKiwaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityMohd MawardiSaariFaculty of Electrical & Electronic Engineering, Universiti Malaysia PahangKeijiTsukadaGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama UniversityManipulation of magnetic nanoparticles (MNP) by an external magnetic field has been widely studied in the fields of biotechnology and medicine for collecting and/or reacting biomaterials in the solutions. Here, dynamic behaviors of MNP in solution under changing gradient magnetic field were investigated using our newly developed laser transmission system (LTS) with a variable magnetic field manipulator. The manipulator consists of a moving permanent magnet placed beside the optical cell filled with MNP solution. A laser beam was focused on the cell and the transmitted laser beam was detected by a silicon photodiode, so that the localized concentration of the MNP at the focused area could be evaluated by the intensity of transmitted laser beam. In this study, the LTS was applied to evaluate dynamic behaviors of MNP in serum solution. Dispersion and aggregation of MNP in the solution were evaluated. While time evolution of dispersion depends on the serum concentration, the behavior during aggregation by the magnetic field was independent of the serum concentration. A series of measurements for zeta-potentials, distributions of particle size, and magnetization distributions was carried out to understand this difference in the behavior. The results indicated that a Brownian motion was main force to distribute the MNP in the solution; on the other hand, the magnetic force to the MNP mainly affected the behavior during aggregation of the MNP in the solution.No potential conflict of interest relevant to this article was reported.AIP PublishingActa Medica Okayama0094-243X21802019Consideration to Display Operator Support Information to Human Operators under High Mental Pressure020028ENAkioGofukuGraduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Operator support systems are extensively studied and developed to support human operators for their activities in especially an abnormal condition of a nuclear power plant. By the advancement of computer technology and artificial intelligence, an operator support system can provide detailed support information based on detailed models and utilizing detailed simulation of plant dynamics and/or complicated inference algorithms. However, human operators may not understand the detailed support information under high mental pressure in an abnormal plant condition. In such a case, it is important how to provide essential and understandable support information. This paper deals with a technique to simplify functional models in order to display operator support information that is generated based on detailed functional models. This paper defines eight cognitive states of human operators from the viewpoint of cognitive abilities of human. In addition, three ways to simplify functional models are identified.No potential conflict of interest relevant to this article was reported.