start-ver=1.4
cd-journal=joma
no-vol=19
cd-vols=
no-issue=1
article-no=
start-page=23-00531
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2024
dt-pub=2024
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Radiative energy transfer via surface plasmon polaritons around metal–insulator grating: For better understanding of magnetic polariton
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=A conventional metal–insulator nanograting has the potential to transmit near-infrared thermal radiation because an electromagnetic wave is resonated in the grating structure. Surface plasmon polaritons (SPPs) take place at the interface between the metal and the insulator with boundaries at both ends. Physicists formulated the resonance frequency of the grating from the Fabry–Pérot interference between the grating thickness and the wavelength of SPPs in a short-range coupled mode. On the other hand, engineering researchers often use a lumped-element model assuming a resonant circuit consisting of an inductance of metal and a capacitance of metal-insulator-metal grating structure. Furthermore, they have considered that the resonant circuit excites a strong magnetic field independent of SPPs. This study compares each physical model and numerical simulation results, then clearly shows that all resonance frequencies and features of the circuit resonance can be described by the Fabry–Pérot interference of the SPPs in short-range coupled mode. Moreover, the estimated resonance frequencies obviously correspond to the local maxima of the transmittance of the nanograting with the various thicknesses and pitches. In this case, a strong magnetic field can be observed in the insulator layer as if it might be an isolated magnetic quantum. However, since materials show no magnetism at near-infrared frequencies, the magnetic response appears due to the contribution of SPPs.
en-copyright=
kn-copyright=
en-aut-name=ISOBEKazuma
en-aut-sei=ISOBE
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=YAMADAYutaka
en-aut-sei=YAMADA
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=HORIBEAkihiko
en-aut-sei=HORIBE
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=HANAMURAKatsunori
en-aut-sei=HANAMURA
en-aut-mei=Katsunori
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Department of Advanced Mechanics, Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=4
en-affil=School of Engineering, Department of Mechanical Engineering, Tokyo Institute of Technology
kn-affil=
en-keyword=Surface plasmon polariton
kn-keyword=Surface plasmon polariton
en-keyword=Circuit resonance
kn-keyword=Circuit resonance
en-keyword=Magnetic polariton
kn-keyword=Magnetic polariton
en-keyword=Lumped-element model
kn-keyword=Lumped-element model
en-keyword=Fabry–Pérot interference
kn-keyword=Fabry–Pérot interference
END
start-ver=1.4
cd-journal=joma
no-vol=221
cd-vols=
no-issue=
article-no=
start-page=125047
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2024
dt-pub=202404
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Bayesian optimization of periodic multilayered slabs for passive absorptivity control
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=A vanadium dioxide (VO2) film grown on a titanium oxide crystal shows a metal–insulator transition at room temperature with drastically changed optical properties. A multilayered slab with a sub-micron scale VO2 film was proposed to utilize its unique properties for passive intensity control of sunlight absorption and radiative cooling. Its optimal geometries were numerically explored using the Bayesian optimization (BO) method. BO was applied for three types of multilayered slabs, those having one, two, or three isolated slabs of different widths. For each type of multilayered slab, BO could optimize geometric variables with practical calculation times considering the total number of possible combinations of variables, which is subsequently referred to as the total number of candidates. Optimization results revealed that two isolated slabs had the most suitable spectral absorptivity in both hot and cold environments. The infrared absorptivity of the double slab was kept low in cold conditions to suppress radiative cooling. However, the double slab exhibited good radiative cooling performance under hot conditions. Electromagnetic energy density surrounding the slab illustrated that metallic VO2 and gold placed in a parallel manner excited the coupled mode of surface plasmon polaritons to enhance absorptivity. Radiative cooling faded for the triple slab because each slab could couple with radiation propagating only across a portion of the cross-sectional area. Through three BO trials, improvement of the VO2 visible reflectivity was recognized as a future issue for further development of passive sunlight absorption control.
en-copyright=
kn-copyright=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=YamamotoTsuyoshi
en-aut-sei=Yamamoto
en-aut-mei=Tsuyoshi
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=4
en-affil=Department of Advanced Mechanics, Graduate School of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
en-keyword=Radiative cooling
kn-keyword=Radiative cooling
en-keyword=Sunlight absorption
kn-keyword=Sunlight absorption
en-keyword=Bayesian optimization
kn-keyword=Bayesian optimization
en-keyword=Vanadium dioxide
kn-keyword=Vanadium dioxide
en-keyword=Short-range surface plasmon polariton
kn-keyword=Short-range surface plasmon polariton
END
start-ver=1.4
cd-journal=joma
no-vol=123
cd-vols=
no-issue=23
article-no=
start-page=231601
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2023
dt-pub=20231204
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Water/ice mixture- and freezing-front motion in a non-isothermal liquid bridge
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=We 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.
en-copyright=
kn-copyright=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=OkanoKodai
en-aut-sei=Okano
en-aut-mei=Kodai
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=School of Engineering, Okayama University
kn-affil=
affil-num=3
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=4
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
END
start-ver=1.4
cd-journal=joma
no-vol=39
cd-vols=
no-issue=44
article-no=
start-page=15587
end-page=15596
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2023
dt-pub=20231023
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Analysis of Evaporation of Droplet Pairs by a Quasi-Steady-State Diffusion Model Coupled with the Evaporative Cooling Effect
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Multidroplet evaporation is a common phase-change phenomenon not only in nature but also in many industrial applications, including inkjet printing and spray cooling. The evaporation behavior of these droplets is strongly affected by the distance between neighboring droplets, and in particular, evaporation suppression occurs as the distance decreases. However, further quantitative information, such as the temperature and local evaporation flux, is limited because the analytical models of multidroplet evaporation only treat vapor diffusion, and the effect of the latent heat transfer through the liquid–vapor phase change is ignored. Here, we perform a numerical analysis of evaporating droplet pairs that linked vapor diffusion from the droplet surface and evaporative cooling. Heat transfer through the liquid and gas phases is also considered because the saturation pressure depends on the temperature. The results show an increase in the vapor concentration in the region between the two droplets. Consequently, the local evaporation flux in the proximate region significantly decreases with decreasing separation distance. This means that the latent heat transfer through the phase change is diminished, and an asymmetrical temperature distribution occurs in the liquid and gas phases. These numerical results provide quantitative information about the temperature and local evaporation flux of evaporating droplet pairs, and they will guide further investigation of multiple droplet evaporation.
en-copyright=
kn-copyright=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
affil-num=1
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Faculty of Environmental, Life, Natural Science and Technology, Okayama University
kn-affil=
en-keyword=19K14910
kn-keyword=19K14910
en-keyword=21K03898
kn-keyword=21K03898
END
start-ver=1.4
cd-journal=joma
no-vol=44
cd-vols=
no-issue=5
article-no=
start-page=69
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2023
dt-pub=20230311
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Synthesis and Characterization of Silica-Encapsulated n-Tetracosane and the Effect of Surface Modification by Silane Coupling Agents
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Microencapsulation of n-tetracosane, whose melting point is approximately 50 degrees C, in a silica shell has been performed through the sol-gel method using tetraethyl orthosilicate (TEOS) as the precursor for silica-shell formation. Additionally, two types of silane coupling agents were used to modify the surface of the microcapsules to change the wettability. The morphology of the microcapsules was observed by scanning electron microscopy. The chemical composition was characterized by Fourier transform infrared spectroscopy. The results confirmed the presence of n-tetracosane and silica in the synthesized microcapsules. Wettability analysis showed hydrophobic and hydrophilic features because of the added silane coupling agents. From the results of differential scanning calorimetry measurements, the encapsulation ratio of the microcapsules increased with decreasing TEOS/n-tetracosane ratio, and the highest encapsulation ratio was 87.1 % at a TEOS/n-tetracosane ratio of 0.25. The pH in the microcapsule solution was affected by addition of a silane coupling agent, and shifting the pH to the basic side lowered the encapsulation ratio owing to enhancement of silica condensation. After 100 differential scanning calorimetry cycles, there was no significant degradation in the phase-change temperatures and enthalpies, which confirmed the good phase-change stability and repeatability. Therefore, the microcapsules are a potential material for thermal-energy-storage systems to effectively utilize energy.
en-copyright=
kn-copyright=
en-aut-name=OkunoKyosuke
en-aut-sei=Okuno
en-aut-mei=Kyosuke
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=4
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
en-keyword=Microcapsule
kn-keyword=Microcapsule
en-keyword=n-Tetracosane
kn-keyword=n-Tetracosane
en-keyword=Silane coupling agent
kn-keyword=Silane coupling agent
en-keyword=Sol-gel method
kn-keyword=Sol-gel method
en-keyword=Thermal energy storage
kn-keyword=Thermal energy storage
END
start-ver=1.4
cd-journal=joma
no-vol=12
cd-vols=
no-issue=22
article-no=
start-page=13917
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2022
dt-pub=2022
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Droplet motion on a wrinkled PDMS surface with a gradient structural length scale shorter than the droplet diameter
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Droplet transportation using a wettability gradient surface has attracted much attention owing to applications such as in microfluidic devices. A surface with a spatial structural gradient was prepared through a simple and cost-effective process even though understanding of droplet behavior on the structure was still limited. Here, we report impinging droplet motion on a gradient wrinkled surface. Surfaces were prepared through hard film deposition on soft pre-strained polydimethylsiloxane (PDMS) with a mask installed with a slit to control the amount of deposition, which is related to the wavelength of the wrinkles. Droplets were impinged with varying position with respect to the structure, and the droplet motion was observed in the direction away from the region under the slit. We found an asymmetric contact angle and alternate motion on both sides of the three-phase contact line during the motion according to the gradient of the wrinkle wavelength. These results may help not only to understand the behavior of droplet impingement on a gradient structural surface but also to further develop applications using directional droplet transfer.
en-copyright=
kn-copyright=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
affil-num=1
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
END
start-ver=1.4
cd-journal=joma
no-vol=43
cd-vols=
no-issue=3
article-no=
start-page=44
end-page=
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2022
dt-pub=2022110
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Absorptivity Control Over the Visible to Mid-Infrared Range Using a Multilayered Film Consisting of Thermochromic Vanadium Dioxide
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Vanadium dioxide (VO2) is a phase transition material that exhibits metallic or insulating characteristics depending upon its temperature. In this study, a multilayered film consisting of 2, silicon dioxide (SiO2) and gold was proposed as a metamaterial that switches its absorptivity over a broad wavelength range depending on the ambient temperature as a fundamental element of a building pigment. At high temperatures, the multilayer showed a high absorptivity at mid-infrared wavelengths, promoting radiative cooling. Simultaneously, the multilayer presented a low absorptivity in the visible and near-infrared wavelengths, enhancing sunlight absorption. The daily average heat flux can possibly be suppressed in summer in comparison with a gray body whose emissivity was 0.8. Conversely, at a lower temperatures, the multilayer showed opposite absorptivity in both the mid-infrared and visible ranges, and its daily average heat flux increased in winter. The metal–insulator phase transition of VO2 caused a drastic shift of the resonant wavelength related to surface phonons and surface plasmons at an infrared wavelength, and optical interference at a visible wavelength, originating at the interface of the SiO2 layer. Thus, the radiative heat flux for both sunlight absorption and radiative cooling was simultaneously controlled depending on the temperature of VO2.
en-copyright=
kn-copyright=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=TomiokaMinoru
en-aut-sei=Tomioka
en-aut-mei=Minoru
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University
kn-affil=
affil-num=2
en-affil=Faculty of Engineering, Department of Mechanical Engineering, Okayama University
kn-affil=
affil-num=3
en-affil=Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University
kn-affil=
affil-num=4
en-affil=Graduate School of Natural Science and Technology, Department of Mechanical Engineering, Okayama University
kn-affil=
END
start-ver=1.4
cd-journal=joma
no-vol=13
cd-vols=
no-issue=29
article-no=
start-page=35079
end-page=35085
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2021
dt-pub=2021714
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Wettability Difference Induced Out-of-Plane Unidirectional Droplet Transport for Efficient Fog Harvesting
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=Securing freshwater resources is a global issue for ensuring sustainable development. Fog harvesting is attracting great attention as a method to collect water without any energy input. Previous reports that were inspired by insects and plants have given insights such as the effectiveness of in-plane wettability and structural differences for droplet transport, which might enhance artificial water harvesting efficiency. However, further efforts to transfer droplets while maintaining performance are needed because droplet motion owing to these effects is limited to the in-plane direction. In this study, we report droplet transport between three-dimensional copper wire structures with nanostructured hydrophobic and superhydrophilic features. This mechanism enhanced the fog harvesting capability by more than 20% compared with the cumulative value of individual wires. In addition, the relationship between the droplet height and spacing of wires affected the performance. Our results show the importance of out-of-plane directional droplet transport from the wire surface assisted by differences in wire wettability, which minimizes limiting factors of fog harvesting including clogging and droplet shedding. Furthermore, the proposed arrangement reduces the overall system width compared with that of a two-dimensional arrangement while maintaining the amount of harvested water. These results provide a promising approach to designing large-scale and highly efficient fog harvesters.
en-copyright=
kn-copyright=
en-aut-name=YamadaYutaka
en-aut-sei=Yamada
en-aut-mei=Yutaka
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=1
ORCID=
en-aut-name=SakataEiji
en-aut-sei=Sakata
en-aut-mei=Eiji
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=2
ORCID=
en-aut-name=IsobeKazuma
en-aut-sei=Isobe
en-aut-mei=Kazuma
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=3
ORCID=
en-aut-name=HoribeAkihiko
en-aut-sei=Horibe
en-aut-mei=Akihiko
kn-aut-name=
kn-aut-sei=
kn-aut-mei=
aut-affil-num=4
ORCID=
affil-num=1
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=2
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=3
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
affil-num=4
en-affil=Graduate School of Natural Science and Technology, Okayama University
kn-affil=
en-keyword=fog harvesting
kn-keyword=fog harvesting
en-keyword=wettability difference
kn-keyword=wettability difference
en-keyword=unidirectional droplet transport
kn-keyword=unidirectional droplet transport
en-keyword=projected area
kn-keyword=projected area
en-keyword=vertical copper wires
kn-keyword=vertical copper wires
END