The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform

Akifumi Ogiwara - One of the best experts on this subject based on the ideXlab platform.

  • Optical Filter for Infrared Region Formed by Polymer Stabilized Cholesteric Liquid Crystals
    2019 24th Microoptics Conference (MOC), 2019
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    We investigated the formation of optical filter for infrared region by using polymer stabilized cholesteric liquid crystals (PSCLCs) under UV irradiation conditions. The selective reflection band in infrared region in PSCLCs is expanded with the increase of UV irradiation energy, and the change of bandwidth shows the threshold characteristics for UV irradiation. The experimental results suggest that the reflection bandwidth of infrared region in PSCLCs is tunable by the UV irradiation based fabrication process. The simple polymerization technique can be applied to achieve the performance of optical filter for Solar-Ray in infrared regions for basis of smart windows.

  • Thermally tunable light filter composed of cholesteric liquid crystals with different temperature dependence
    Solar Energy Materials and Solar Cells, 2016
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    Abstract A thermally tunable light filter by using cholesteric liquid crystals as a reflective type of optical device is proposed for an advanced thermo-driven light controller to realize the efficient control of Solar-Rays without losing the outdoor view and mounting the additional films. The cholesteric liquid crystals (CLCs) are fabricated to control the temperature dependence of selective transmittance spectra by using the composites of chiral dopants with different magnitude and sign of helical twisting power (HTP). The effects of chiral dopants on temperature dependence of selective wavelength are explained by the theoretical equation introduced for the mixture of chiral dopants. The optical properties for polymer stabilized cholesteric liquid crystal are also investigated by the spectroscopic measurements at different temperature in the various polymer concentrations. The optical performance of the tunable light filter formed by the combination of CLCs with different temperature dependence is demonstrated for the application as a reflective thermo-driven Solar-Ray controller.

  • Analysis of selective reflection spectrum in cholesteric liquid crystal cells for Solar-Ray controller
    Liquid Crystals XIX, 2015
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    The cholesteric liquid crystal (CLC) cells are fabricated by varying the concentration of various chiral dopants and liquid crystal (LC) diacrylate monomers. The wavelength and bandwidth of selective reflection spectrum in CLC cells are measured by a spectroscopic technique. The variation of the selective reflection spectrum in CLC cells is investigated by doping the different kinds of liquid crystal (LC) diacrylate monomers which stabilize a helical twisting structure by photopolymerization. The effects of the selective reflection spectrum on the visible and infrared lights in spectral Solar irradiance are explained by the performance for a Solar-Ray controller based on the spectral Solar irradiance for air mass 1.5 and the standard luminous efficiency function for photopic vision.

  • Effect of polymer concentration on selective reflection spectra in cholesteric liquid crystals
    2015 20th Microoptics Conference (MOC), 2015
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    The selective reflection spectra in cholesteric liquid crystals (CLCs) are investigated by doping different kinds of liquid crystal (LC) diacrylate monomers. The bandwidth of selective reflection spectrum in CLCs is characterized by the LC diacrylate monomer materials, and the bandwidth of spectrum becomes broader with the concentration of LC monomer. The results presents that the variation of selective reflection spectra induced in CLCs by the polymer concentration is applicable as performance indicators for the basis in reflective light controller of Solar-Ray control windows.

  • Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
    Solar Energy Materials and Solar Cells, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Kazuki Yoshimura, Akifumi Ogiwara
    Abstract:

    Abstract A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous Solar-Ray control window, which utilizes the nematic-to-isotropic ( N – I ) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the Solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 °C. Furthermore, a more practical solution for using the HPDLC for a Solar-Ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to N – I transition.

Hiroshi Kakiuchida - One of the best experts on this subject based on the ideXlab platform.

  • Optical Filter for Infrared Region Formed by Polymer Stabilized Cholesteric Liquid Crystals
    2019 24th Microoptics Conference (MOC), 2019
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    We investigated the formation of optical filter for infrared region by using polymer stabilized cholesteric liquid crystals (PSCLCs) under UV irradiation conditions. The selective reflection band in infrared region in PSCLCs is expanded with the increase of UV irradiation energy, and the change of bandwidth shows the threshold characteristics for UV irradiation. The experimental results suggest that the reflection bandwidth of infrared region in PSCLCs is tunable by the UV irradiation based fabrication process. The simple polymerization technique can be applied to achieve the performance of optical filter for Solar-Ray in infrared regions for basis of smart windows.

  • Thermally tunable light filter composed of cholesteric liquid crystals with different temperature dependence
    Solar Energy Materials and Solar Cells, 2016
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    Abstract A thermally tunable light filter by using cholesteric liquid crystals as a reflective type of optical device is proposed for an advanced thermo-driven light controller to realize the efficient control of Solar-Rays without losing the outdoor view and mounting the additional films. The cholesteric liquid crystals (CLCs) are fabricated to control the temperature dependence of selective transmittance spectra by using the composites of chiral dopants with different magnitude and sign of helical twisting power (HTP). The effects of chiral dopants on temperature dependence of selective wavelength are explained by the theoretical equation introduced for the mixture of chiral dopants. The optical properties for polymer stabilized cholesteric liquid crystal are also investigated by the spectroscopic measurements at different temperature in the various polymer concentrations. The optical performance of the tunable light filter formed by the combination of CLCs with different temperature dependence is demonstrated for the application as a reflective thermo-driven Solar-Ray controller.

  • Analysis of selective reflection spectrum in cholesteric liquid crystal cells for Solar-Ray controller
    Liquid Crystals XIX, 2015
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    The cholesteric liquid crystal (CLC) cells are fabricated by varying the concentration of various chiral dopants and liquid crystal (LC) diacrylate monomers. The wavelength and bandwidth of selective reflection spectrum in CLC cells are measured by a spectroscopic technique. The variation of the selective reflection spectrum in CLC cells is investigated by doping the different kinds of liquid crystal (LC) diacrylate monomers which stabilize a helical twisting structure by photopolymerization. The effects of the selective reflection spectrum on the visible and infrared lights in spectral Solar irradiance are explained by the performance for a Solar-Ray controller based on the spectral Solar irradiance for air mass 1.5 and the standard luminous efficiency function for photopic vision.

  • Effect of polymer concentration on selective reflection spectra in cholesteric liquid crystals
    2015 20th Microoptics Conference (MOC), 2015
    Co-Authors: Akifumi Ogiwara, Hiroshi Kakiuchida
    Abstract:

    The selective reflection spectra in cholesteric liquid crystals (CLCs) are investigated by doping different kinds of liquid crystal (LC) diacrylate monomers. The bandwidth of selective reflection spectrum in CLCs is characterized by the LC diacrylate monomer materials, and the bandwidth of spectrum becomes broader with the concentration of LC monomer. The results presents that the variation of selective reflection spectra induced in CLCs by the polymer concentration is applicable as performance indicators for the basis in reflective light controller of Solar-Ray control windows.

  • Long-Term Optical and Thermal Examinations of Ceramic Wall System with Solar-Altitude Dependent Reflectance
    Advances in Science and Technology, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Toyohiko Sugiyama, Kazuki Yoshimura, Koji Tajiri, Yukio Ishikawa
    Abstract:

    Many ceramic tiles are used as outer skins of office and residential buildings and they prevent severe weathers of Solar Ray, temperature, wetness and wind. The Solar irradiance to the outer walls is a significant factor to influence the heat flow into room and consequently the energy load due to air conditioning. Particularly in the region where clear seasonal change is experienced, optical and thermal properties of the wall surfaces are desired to be controlled as a function of season; Solar reflective in hot days in summer; Solar absorptive in chilly days in winter. The ceramic walls with Solar-altitude dependent reflectance are expected to be a simple and efficient method for autonomous control of heat flow into the room and in this study they were investigated from the viewpoints of optical property and shape of the tiles. The correlation between Solar absorption and luminous reflectance revealed that there are some ceramic tiles whose Solar absorption slightly depends on Solar altitude. The triangular-shaped ceramic tiles that have reflective-upward and absorptive-downward surfaces were investigated in optical and thermal properties, based on one-year exposure of the tiles to Solar radiation and Ray-tracing simulation. These measurement and simulation found that the triangular-shaped tiles are an effective approach to the control of Solar absorption and suggested the effective shape and surface property of the tiles such as optical reflectance, surface specularity and triangular angle.

Kazuki Yoshimura - One of the best experts on this subject based on the ideXlab platform.

  • Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
    Solar Energy Materials and Solar Cells, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Kazuki Yoshimura, Akifumi Ogiwara
    Abstract:

    Abstract A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous Solar-Ray control window, which utilizes the nematic-to-isotropic ( N – I ) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the Solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 °C. Furthermore, a more practical solution for using the HPDLC for a Solar-Ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to N – I transition.

  • Long-Term Optical and Thermal Examinations of Ceramic Wall System with Solar-Altitude Dependent Reflectance
    Advances in Science and Technology, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Toyohiko Sugiyama, Kazuki Yoshimura, Koji Tajiri, Yukio Ishikawa
    Abstract:

    Many ceramic tiles are used as outer skins of office and residential buildings and they prevent severe weathers of Solar Ray, temperature, wetness and wind. The Solar irradiance to the outer walls is a significant factor to influence the heat flow into room and consequently the energy load due to air conditioning. Particularly in the region where clear seasonal change is experienced, optical and thermal properties of the wall surfaces are desired to be controlled as a function of season; Solar reflective in hot days in summer; Solar absorptive in chilly days in winter. The ceramic walls with Solar-altitude dependent reflectance are expected to be a simple and efficient method for autonomous control of heat flow into the room and in this study they were investigated from the viewpoints of optical property and shape of the tiles. The correlation between Solar absorption and luminous reflectance revealed that there are some ceramic tiles whose Solar absorption slightly depends on Solar altitude. The triangular-shaped ceramic tiles that have reflective-upward and absorptive-downward surfaces were investigated in optical and thermal properties, based on one-year exposure of the tiles to Solar radiation and Ray-tracing simulation. These measurement and simulation found that the triangular-shaped tiles are an effective approach to the control of Solar absorption and suggested the effective shape and surface property of the tiles such as optical reflectance, surface specularity and triangular angle.

  • Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
    Solar Energy Materials and Solar Cells, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Kazuki Yoshimura, Akifumi Ogiwara
    Abstract:

    A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous Solar-Ray control window, which utilizes the nematic-to-isotropic (NI) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the Solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 °C. Furthermore, a more practical solution for using the HPDLC for a Solar-Ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to NI transition. © 2010 Elsevier B.V.

Masato Tazawa - One of the best experts on this subject based on the ideXlab platform.

  • Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
    Solar Energy Materials and Solar Cells, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Kazuki Yoshimura, Akifumi Ogiwara
    Abstract:

    Abstract A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous Solar-Ray control window, which utilizes the nematic-to-isotropic ( N – I ) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the Solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 °C. Furthermore, a more practical solution for using the HPDLC for a Solar-Ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to N – I transition.

  • Long-Term Optical and Thermal Examinations of Ceramic Wall System with Solar-Altitude Dependent Reflectance
    Advances in Science and Technology, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Toyohiko Sugiyama, Kazuki Yoshimura, Koji Tajiri, Yukio Ishikawa
    Abstract:

    Many ceramic tiles are used as outer skins of office and residential buildings and they prevent severe weathers of Solar Ray, temperature, wetness and wind. The Solar irradiance to the outer walls is a significant factor to influence the heat flow into room and consequently the energy load due to air conditioning. Particularly in the region where clear seasonal change is experienced, optical and thermal properties of the wall surfaces are desired to be controlled as a function of season; Solar reflective in hot days in summer; Solar absorptive in chilly days in winter. The ceramic walls with Solar-altitude dependent reflectance are expected to be a simple and efficient method for autonomous control of heat flow into the room and in this study they were investigated from the viewpoints of optical property and shape of the tiles. The correlation between Solar absorption and luminous reflectance revealed that there are some ceramic tiles whose Solar absorption slightly depends on Solar altitude. The triangular-shaped ceramic tiles that have reflective-upward and absorptive-downward surfaces were investigated in optical and thermal properties, based on one-year exposure of the tiles to Solar radiation and Ray-tracing simulation. These measurement and simulation found that the triangular-shaped tiles are an effective approach to the control of Solar absorption and suggested the effective shape and surface property of the tiles such as optical reflectance, surface specularity and triangular angle.

  • Thermal control of transmittance/diffraction states of holographic structures composed of polymer and liquid crystal phases
    Solar Energy Materials and Solar Cells, 2010
    Co-Authors: Hiroshi Kakiuchida, Masato Tazawa, Kazuki Yoshimura, Akifumi Ogiwara
    Abstract:

    A microperiodic structure composed of polymer and liquid crystal (LC) phases, called holographic polymer dispersed liquid crystal (HPDLC), was fabricated by a photo-induced phase-separation technique. It is anticipated that the HPDLC can be used as a thermo-driven light controller, in particular, for an autonomous Solar-Ray control window, which utilizes the nematic-to-isotropic (NI) phase transition phenomenon in the LC phase of the periodic structure. In the present study, the transmittance/diffraction properties of samples with different thermal behaviors were examined, and it was found that 15% of the Solar radiation was switched between the transmittance and diffraction states as a function of temperature at around 30 °C. Furthermore, a more practical solution for using the HPDLC for a Solar-Ray control window was demonstrated. From the viewpoint of structural analysis, scanning electron microscopy reveals that LC droplets, a few tens of nanometers in size are, distributed and coalesce to form periodic LC layers. By carrying out polarizing microscopy and performing transmittance/diffraction measurements as a function of temperature, it is observed that the LC molecules in the droplets are strongly oriented along the grating vector and their orientations decline with a rise in temperature. These observed structures are of importance for the generation of a large change in the transmittance/diffraction properties due to NI transition. © 2010 Elsevier B.V.

Vicente Flores - One of the best experts on this subject based on the ideXlab platform.

  • Solar Ray Tracing Analysis to Determine Energy Availability in a CPC Designed for Use as a Residential Water Heater
    Energies, 2018
    Co-Authors: Miguel Terrón-hernández, Manuel I. Peña-cruz, J. G. Carrillo, Ulises Diego-ayala, Vicente Flores
    Abstract:

    Compound parabolic concentrators are relevant systems used in Solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water heating applications. This work presents a simulation study using a Ray tracing analysis. With this technique, we simulate the interaction between Solar Rays and Solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations throughout the year: static setup at 21° and multi-position setup; tilted with respect to the horizontal, depending on three seasonal positions: 0° for summer, 16° for spring/autumn, and 32° for winter, with the aim to evaluate the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21°, the proposed Solar Compound Parabolic Concentrator (CPC) works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The most effective design was also built and analyzed outdoors. The obtained thermal efficiency was of ~43%. The optical design and its evaluation developed herein proved to be a valuable tool for prototype design and performance evaluation.

  • Solar Ray Tracing Analysis to Determine Energy Availability in a CPC Designed for Use as a Residential Water Heater
    2017
    Co-Authors: Miguel Terrón-hernández, Manuel I. Peña-cruz, J. G. Carrillo, Ulises Diego-ayala, Vicente Flores
    Abstract:

    Compound parabolic concentrators are relevant systems used in Solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water applications. This work presents a simulation study using a Ray tracing methodology. With this technique we simulate the interaction between Solar Rays and Solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations: stationary at 21° throughout the year and multi position setup; tilted with respect to the horizontal depending on three seasonal positions: 0° for summer, 16° for spring / autumn and 32° for winter, with the objective of increasing the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21°, the proposed system works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The methodology developed herein proved to be a valuable tool for prototype design and performance evaluation.