研究者データベース

藤井 宏之(フジイ ヒロユキ)
工学研究院 機械・宇宙航空工学部門 熱流体システム
助教

基本情報

所属

  • 工学研究院 機械・宇宙航空工学部門 熱流体システム

職名

  • 助教

学位

  • 博士(工学)(東北大学)

論文上での記載著者名

  • Hiroyuki Fujii

ホームページURL

J-Global ID

研究キーワード

  • 逆問題   数値計算   光伝搬   輻射輸送   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 熱工学 / ふく射輸送;光散乱

職歴

  • 2019年04月 - 現在 北海道大学 大学院工学研究院 機械宇宙工学部門 助教(テニュア)
  • 2019年09月 - 2019年12月 ミシガン大学 電子工学・計算科学学科 客員研究員
  • 2014年04月 - 2019年03月 北海道大学 大学院工学研究院 機械宇宙工学部門 助教(テニュアトラック)
  • 2012年04月 - 2014年03月 東京都医学総合研究所 ヒト統合脳機能プロジェクト 外部支援研究員

学歴

  • 2009年04月 - 2012年03月   東北大学大学院   工学研究科ナノメカニクス専攻   博士課程後期3年の課程
  • 2007年04月 - 2009年03月   東北大学大学院   工学研究科ナノメカニクス専攻   博士課程前期2年の課程
  • 2003年04月 - 2007年03月   筑波大学   第一学群自然学類   物理学専攻

所属学協会

  • 日本伝熱学会   日本機械学会   日本物理学会   

研究活動情報

論文

  • 藤井 宏之, Leung Tsang, Jiyue Zhu, 野村 航希, 小林 一道, 渡部 正夫
    Optics Express 28 15 22962 - 22977 2020年07月17日 [査読有り][通常論文]
  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    Scientific Reports 10 8143  2020年05月18日 [査読有り][通常論文]
  • 野村 航希, 藤井 宏之, 小林 一道, 渡部 正夫, 西村 吾朗
    Proceeding of the 7th Asian NIR symposium (ANS2020) 2020 AFI-0006 12 - 13 2020年02月 [査読有り][通常論文]
  • 遠藤 茂樹, 藤井 宏之, 小林 一道, 渡部 正夫
    Proceeding of the 7th Asian NIR symposium (ANS2020) 2020 NRT-0008 60 - 61 2020年02月 [査読有り][通常論文]
  • 藤井 宏之, 西村 吾朗, 遠藤 茂樹, 野村 航希, 小林 一道, 渡部 正夫
    Proceeding of the 7th Asian NIR symposium (ANS2020) 2020 AFI-0007 14 - 15 2020年02月 [査読有り][通常論文]
  • 藤井 宏之, 上野 萌黄, 小林 一道, 渡部 正夫
    Applied Sciences 10 93 1 - 16 2019年12月 [査読有り][通常論文]
  • 芦田 拓, 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之
    Physical Review Fluids 5 011601 1 - 9 2019年11月 [査読有り][通常論文]
  • 田部 広風海, 小林 一道, 矢口 久雄, 藤井 宏之, 渡部 正夫
    International Journal of Thermal Sciences 150 106203 1 - 10 2019年11月 [査読有り][通常論文]
  • 藤井 宏之, 千葉 豪, 山田 幸生, 星 詳子, 小林 一道, 渡部 正夫
    Proceedings of the 9th International Symposium on Radiative Transfer, RAD-19 SM05 261 - 268 2019年09月 [査読有り][通常論文]
  • 田林 孝介, 藤井 宏之, 小林 一道, 渡部 正夫
    AIP Conference Proceedings (ICNAAM2018) 2116 450052 1 - 4 2019年07月 [査読有り][通常論文]
  • 大川 晋平, 三村 徹也, 藤井 宏之, 川口 拓之, 谷川 ゆかり, 町田 学, 岡田 英史, 星 詳子
    Proceedings of SPIE, Diffuse Optical Spectroscopy and Imaging VII 11074 1107407 1 - 4 2019年07月 [査読有り][通常論文]
  • 藤井 宏之, 山田 幸生, 星 詳子, 小林 一道, 渡部 正夫
    AIP Conference Proceedings (ICNAAM2018) 2116 450037 1 - 4 2019年07月 [査読有り][通常論文]
  • 山本 恭平, 小林 一道, 渡部 正夫, 藤井 宏之, 今 美紗紀, 高比良 裕之
    Physical Review Fluids 4 063603 1 - 10 2019年06月 [査読有り][通常論文]
  • 田林 孝介, 藤井 宏之, 大川 晋平, 小林 一道, 山田 幸生, 星 詳子, 渡部 正夫
    CMBE Proceedings (6th International Conference on Computational & Mathematical Biomedical Engineering) A5 161 - 164 2019年05月 [査読有り][通常論文]
  • Correction to: Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet
    Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    Heat and Mass Transfer 55 4 1005 - 1005 2019年04月 [査読有り][通常論文]
  • 田部 広風海, 小林 一道, 矢口 久雄, 藤井 宏之, 渡部 正夫
    Heat and Mass Transfer 55 4 993 - 1003 2019年04月 [査読有り][通常論文]
  • Molecular Dynamics Study on Influence of Liquid-solid Intermolecular Force on Levitating Mechanism of Impacting Nanodroplet on Heated Wall
    Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    Surface Wettability Effects on Phase Change Phenomena(SWEP) 2019年 [査読有り][通常論文]
  • 小林 一道, 永山 貴広, 渡部 正夫, 藤井 宏之, 今 美沙紀
    Journal of Fluid Mechanics 856 10 1045 - 1063 2018年12月 [査読有り][通常論文]
  • 藤井 宏之, 山田 幸生, 千葉 豪, 星 詳子, 小林 一道, 渡部 正夫
    Journal of Computational Physics 374 591 - 604 2018年12月 [査読有り][通常論文]
  • 藤井 宏之, 山田 幸生, 星 詳子, 大川 晋平, 小林 一道, 渡部 正夫
    Reaction Kinetics, Mechanisms and Catalysis 123 439 - 453 2018年04月 [査読有り][通常論文]
  • Influence of surface roughness of high temperature wall on levitation of impacting droplet based on molecular dynamics simulation
    Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    Surface Wettability Effects on Phase Change Phenomena (SWEP) workshop 2018年 [査読有り][通常論文]
  • Numerical investigation of light and pressure propagation in biological tissue for model-based photoacoustic tomography
    田林 孝介, 藤井 宏之, 小林 一道, 渡部 正夫
    Extended Abstracts of The 9th JSME-KSME Thermal and Fluids Engineering Conference TFEC9-1526 1 - 4 2017年10月 [査読有り][通常論文]
  • 森川昌太郎, 立藏祐樹, 小林一道, 藤井宏之, 渡部正夫, 佐々木浩一
    ながれ 36 105 - 108 2017年05月 [査読有り][通常論文]
  • H. Fujii, Y. Yamada, K. Kobayashi, M. Watanabe, Y. Hoshi
    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 33 5 1 - 12 2017年05月 [査読有り][通常論文]
     
    Diffuse optical tomography using near-infrared light in a wavelength range from 700 to 1000nm has the potential to enable non-invasive diagnoses of thyroid cancers; some of which are difficult to detect by conventional methods such as ultrasound tomography. Diffuse optical tomography needs to be based on a physically accurate model of light propagation in the neck, because it reconstructs tomographic images of the optical properties in the human neck by inverse analysis. Our objective here was to investigate the effects of three factors on light propagation in the neck using the 2D time-dependent radiative transfer equation: (1) the presence of the trachea, (2) the refractive-index mismatch at the trachea-tissue interface, and (3) the effect of neck organs other than the trachea (spine, spinal cord, and blood vessels). There was a significant influence of reflection and refraction at the trachea-tissue interface on the light intensities in the region between the trachea and the front of the neck surface. Organs other than the trachea showed little effect on the light intensities measured at the front of the neck surface although these organs affected the light intensities locally. These results indicated the necessity of modeling the refractive-index mismatch at the trachea-tissue interface and the possibility of modeling other neck organs simply as a homogeneous medium when the source and detectors were far from large blood vessels.
  • 小林 一道, 佐々木 清文, 今 美紗紀, 藤井 宏之, 渡部 正夫
    Microfluidics and Nanofluidics 21 3 1 - 13 2017年03月 [査読有り][通常論文]
     
    Using molecular dynamics simulations, the present study investigated the precise characteristics of the binary mixture of condensable gas (vapor) and noncondensable gas (NC gas) molecules creating kinetic boundary conditions (KBCs) at a gas-liquid interface in equilibrium. We counted the molecules utilizing the improved two-boundary method proposed in previous studies by Kobayashi et al. (Heat Mass Trans 52: 1851-1859, 2016. doi: 10.1007/s00231-015-1700-6). In this study, we employed Ar for the vapor molecules, and Ne for the NC gas molecules. The present method allowed us to count easily the evaporating, condensing, degassing, dissolving, and reflecting molecules in order to investigate the detailed motion of the molecules, and also to evaluate the velocity distribution function of the KBCs at the interface. Our results showed that the evaporation and condensation coefficients for vapor and NC gas molecules decrease with the increase in the molar fraction of the NC gas molecules in the liquid. We also found that the KBCs can be specified as a function of the molar fraction and liquid temperature. Furthermore, we discussed the method to construct the KBCs of vapor and NC gas molecules.
  • Molecular Dynamics Study of Droplet Impact on High-Temperature Wall
    Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    The 7th East Asia Mechanical and Aerospace Engineering Workshop 2017年 [査読有り][通常論文]
  • Molecular Dynamics Simulation of the Role of the Wettability in the Droplet Impact on a High-temperature Wall
    Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    Extended Abstracts of the 9th JSME-KSME Thermal and Fluids Engineering Conference TFEC9-1492 2017年 [査読有り][通常論文]
  • Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
    JOURNAL OF MATHEMATICAL CHEMISTRY 54 10 2048 - 2061 2016年11月 [査読有り][通常論文]
     
    Numerical calculation of photon migration in biological tissue using the radiative transfer equation (RTE) has attracted great interests in biomedical optics and imaging. Because biological tissue is a highly forward-peaked scattering medium, renormalization of the phase function in numerical calculation of the RTE is crucial. This paper proposes a simple approach of renormalizing the phase function by the double exponential formula, which was heuristically modified from the original one. Firstly, the validity of the proposed approach was tested by comparing numerical results for an average cosine of the polar scattering angle calculated by the proposed approach with those by the conventional approach in highly forward-peaked scattering. The results show that calculation of the average cosine converged faster using the proposed approach than using the conventional one as a total number of discrete angular directions increases. Next, the accuracy of the numerical solutions of the RTE using the proposed approach was examined by comparing the numerical solutions with the analytical solutions of the RTE in a homogeneous medium with highly forward-peaked scattering. It was found that the proposed approach reduced the errors of the numerical solutions from those using the conventional one especially at a small value of the total number of the directions. This result suggests that the proposed approach has a possibility to improve the accuracy for the numerical results of the RTE in the highly scattering medium.
  • Kazumichi Kobayashi, Kazuki Konno, Hisao Yaguchi, Hiroyuki Fujii, Toshiyuki Sanada, Masao Watanabe
    PHYSICS OF FLUIDS 28 3 1 - 10 2016年03月 [査読有り][通常論文]
     
    In this study, we investigated nanodroplet spreading at the early stage after the impact using molecular dynamics simulations by changing the magnitude of the intermolecular force between the liquid and wall molecules. We showed that the droplet deformation after the impact greatly depends on the intermolecular force. The temporal evolution of the spreading diameters was measured by the cylindrical control volume for several molecular layers in the vicinity of the wall. At the early stage of the nanodroplet impact, the normalized spreading radius of the droplet is proportional to the square root of the normalized time, (t) over cap. This result is understood by the geometrical consideration presented by Rioboo et al. ["Time evolution of liquid drop impact onto solid, dry surfaces," Exp. Fluids 33, 112-124 (2002)]. In addition, we found that as the intermolecular force between the liquid and wall becomes stronger, the normalized spreading diameter of the first molecular layer on the wall remains less dependent on the impact velocity. Furthermore, the time evolution of the droplet spreading changes from root(t) over cap to log (t) over cap with time. (C) 2016 AIP Publishing LLC.
  • 藤井 宏之, 大川 晋平, 灘本 健, 岡田 英史, 山田 幸生, 星 詳子, 渡部 正夫
    Journal of Applied Nonlinear Dynamics 5 1 117 - 125 2016年03月 [査読有り][通常論文]
     
    arXiv:1603.03769 [physics.med-ph]
    http://arxiv.org/abs/1603.03769
  • 服部 聖仁, 藤井 宏之, 西村 吾朗, 小林 一道, 渡部 正夫
    Proceeding of the fifth Asian NIR symposium (ANS2016) 2016 O-6 72 - 73 2016年 [査読有り][通常論文]
  • 藤井 宏之, 西村 吾朗, 服部 聖仁, 小林 一道, 渡部 正夫
    Proceeding of the fifth Asian NIR symposium (ANS2016) 2016 P-86 288 - 289 2016年 [査読有り][通常論文]
  • Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
    30TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS (RGD 30) 1786 110002 1 - 9 2016年 [査読有り][通常論文]
     
    The aim of this study is to construct the kinetic boundary condition for Ar-Ne binary mixture in equilibrium using molecular dynamics (MD) simulations. The temperature of the MD simulation system is 85 K; Ar molecules behave as condensable gas (vapor), and Ne molecules behave as non-condensable gas (gas). In this simulation, we utilize the two-boundary method improved by our previous study to investigate behaviors of Ar and Ne molecules at the interface. From the results, we can obtain the molecular mass fluxes at the interface, and evaluate the values of evaporation and condensation coefficients of Ar (vapor) and Ne (gas) molecules.
  • Erina Miyakawa, Hiroyuki Fujii, Kiyohito Hattori, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
    Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016) 1790 050003 1 - 4 2016年 [査読有り][通常論文]
     
    Diffuse optical tomography (DOT), which is still under development, has a potential to enable non-invasive diagnoses of thyroid cancers in the human neck using the near-infrared light. This modality needs a photon migration model because scattered light is used. There are two types of photon migration models: the radiative transport equation (RTE) and diffusion equation (DE). The RTE can describe photon migration in the human neck with accuracy, while the DE enables an efficient calculation. For developing the accurate and efficient model of photon migration, it is crucial to investigate a condition where the DE holds in a scattering medium including a void region under the refractive-index mismatch at the void boundary because the human neck has a trachea (void region) and the refractive indices are different between the human neck and trachea. Hence, in this paper, we compare photon migration using the RTE with that using the DE in the medium. The numerical results show that the DE is valid under the refractive-index match at the void boundary even though the void region is near the source and detector positions. Under the refractive-index mismatch at the boundary, the numerical results using the DE disagree with those using the RTE when the void region is near the source and detector positions. This is probably because the anisotropy of the light scattering remains around the void boundary.
  • Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
    Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016) 1790 050002 1 - 4 2016年 [査読有り][通常論文]
     
    Numerical calculation of photon migration in biological tissue using the radiative transfer equation (RTE) has attracted great interests in biomedical optics and imaging. Because biological tissue is a highly forward-peaked scattering medium, a normalization of scattering phase function in the RTE is crucial. This paper proposes a simple way of normalizing the phase function by the double exponential formula, which is heuristically modified from the original one. The proposed method is validated by the agreement between the numerical solution of the RTE with the proposed method and analytical solution of the RTE for the case of a highly forward-peaked scattering medium, while the numerical solutions with conventional normalization methods disagree with the analytical solution. This result suggests the proposed method is accurate in numerical calculation of the RTE.
  • Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
    BIOPHOTONICS JAPAN 2015 9792 97921A 1 - 5 2015年 [査読有り][通常論文]
     
    An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product; then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis.
  • Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
    BIOPHOTONICS JAPAN 2015 9792 979214 1 - 5 2015年 [査読有り][通常論文]
     
    Development of a physically accurate and computationally efficient photon migration model for turbid media is crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation. In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency of computation. The coupling model provides an accurate description of the photon migration in various turbid media in a wide range of the optical properties, and reduces computational loads when compared with those of full calculation of the RTE.
  • Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe
    BIOMEDICAL APPLICATIONS OF LIGHT SCATTERING IX 9333 933313 1 - 6 2015年 [査読有り][通常論文]
     
    Accurate modeling and efficient calculation of photon migration in biological tissues is requested for determination of the optical properties of living tissues by in vivo experiments. This study develops a calculation scheme of photon migration for determination of the optical properties of the rat cerebral cortex (ca 0.2 cm thick) based on the three-dimensional time-dependent radiative transport equation assuming a homogeneous object. It is shown that the time-resolved profiles calculated by the developed scheme agree with the profiles measured by in vivo experiments using near infrared light. Also, an efficient calculation method is tested using the delta-Eddington approximation of the scattering phase function.
  • Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi
    JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER 147 145 - 154 2014年11月 [査読有り][通常論文]
     
    Numerical modeling of light propagation in random media has been an important issue for biomedical imaging, including diffuse optical tomography (DOT). For high resolution DOT, accurate and fast computation of light propagation in biological tissue is desirable. This paper proposes a space-time hybrid model for numerical modeling based on the radiative transfer and diffusion equations (RTE and DE, respectively) in random media under refractive-index mismatching. In the proposed model, the RTE and DE regions are separated into space and time by using a crossover length and the time from the ballistic regime to the diffusive regime, rho(DA) similar to 10/mu(t)' and t(DA) similar to 20/v mu(t)' where mu(t)' and v represent a reduced transport coefficient and light velocity, respectively. The present model succeeds in describing light propagation accurately and reduces computational load by a quarter compared with full computation of the RTE. (C) 2014 Elsevier Ltd. All rights reserved.
  • Image errors of time-resolved optical tomography based on the radiative transfer and diffusion equations
    藤井宏之, 大川晋平, 吉永哲哉, 山田幸生, 星詳子
    ODF'14 Technical Digest (9th International Conference on Optics-photonics Design and Fabrication) 13PDb-20 1 - 2 2014年02月 [査読有り][通常論文]
  • H. Fujii, Y. Hoshi, S. Okawa, T. Kosuge, S. Kohno
    4TH INTERNATIONAL SYMPOSIUM ON SLOW DYNAMICS IN COMPLEX SYSTEMS: KEEP GOING TOHOKU 1518 579 - 585 2013年 [査読有り][通常論文]
     
    Recently, numerical models for photon propagation inside the living tissues have extensively been discussed based on the radiative transfer (RTE) and diffusion equations (DE). In this paper, we propose a hybrid model based on the RTE and DE for photon propagation in a turbid medium with an anisotropic source and refractive-index-mismatched boundaries. At first, we examine the validity of the diffusion approximation by comparing calculated fluence rates between the RTE and DE. The accuracy of the diffusion approximation is confirmed when the detector is placed far from the source and boundaries. These length scales are estimated at similar to 10/mu(t) from the source and similar to 3/mu(t) from the boundaries with the transport coefficient These length scales are estimated at similar to 10/mu(t) from the source and similar to 3/mu(t) from the boundaries with the transport coefficient mu(t). By using the two length scales, we can construct a hybrid model successfully. Our hybrid model recovers photon propagation based on the RTE, and effectively reduces computation costs by approximately half.
  • 藤井 宏之, 星 詳子, 大川 晋平, 小菅 朋也, 河野 理
    Proceedings of SPIE, Optical Tomography and Spectroscopy of Tissue X 8578 857835 1 - 7 2013年 [査読有り][通常論文]
  • Hiroyuki Fujii, Yoko Hoshi, Shinpei Okawa, Tetsuya Yoshinaga, Satoru Kohno, Yukio Yamada
    11TH INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2013, PTS 1 AND 2 (ICNAAM 2013) 1558 2528 - 2531 2013年 [査読有り][通常論文]
     
    Recently, transport phenomena of photon energy have been attractive topics due to the applications of the biomedical imaging such as diffuse optical tomography (DOT). For improvement of numerical modeling in DOT, accurate and fast calculations of light propagations in biological tissues are necessary. This paper proposes a light propagation model based on the radiative transfer and diffusion equations (RTE and DE) in random media. Numerical calculations of light propagation using the both equations provide the condition for the DE to be valid. Length and time scales for the validity of the DE are estimated to be about 10l(m) and 20l(m)/v, respectively, where l(m) is the mean free path of photon and v is the light velocity. The proposed model can provide accurate descriptions of spatial and temporal profiles of light propagation in random media subject to the refractive-index mismatched boundary condition. Also, it can appropriately reduce computation time by an order of magnitude when compared with that fully computing the RTE.
  • Hiroyuki Fujii, Michio Tokuyama
    PHYSICAL REVIEW E 83 2 1 - 8 2011年02月 [査読有り][通常論文]
     
    The recently proposed universality near the glass transition [M. Tokuyama, Phys. Rev. E 80, 031503 (2009)] is tested for the dynamics of a single atom in ternary metallic glass-forming Cu60TixZr40-x melts by using molecular-dynamics simulations for different compositions, x = 10, 20, and 30. First, a master curve for the dynamics of the atom, such as the mean-square and mean-fourth displacements, is shown to exist independently of x if the long-time self-diffusion coefficient D-S(L) has the same value. Second, a master curve for the temperature dependence of D-S(L) is shown to exist independently of x. Finally, master curves for characteristic length and time scales of the atom are also shown to exist independently of x.
  • 藤井 宏之, 徳山 道夫
    Proceedings of Eighth International Conference on Flow Dynamics OS12-72 618 - 619 2011年 [査読有り][通常論文]

その他活動・業績

共同研究・競争的資金等の研究課題

  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 藤井 宏之
  • 秋山記念生命科学振興財団:研究助成(一般)
    研究期間 : 2020年07月 -2021年03月 
    代表者 : 藤井 宏之
  • 生体の大域・局所構造に起因したふく射の干渉機構の解明と光散乱特性の理論値導出
    日本学術振興会:科学研究費助成事業 若手研究
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 藤井 宏之
     
    本研究では、生体組織を高密度かつ網目構造を有した高分子溶液として捉え、光干渉散乱理論に基づいて、生体組織における光散乱特性の理論値を導出すること、そして、生体組織の構造特性に起因した光の干渉機構を解明することを目的としている。
    平成30年度では、まず、従来の単分散のコロイド水溶液における干渉散乱理論を多分散に拡張することを試みた。ここで、Cartignyらによって構築された干渉散乱理論を適用し、静的構造因子にはPercus-Yevickの解析解を用いた。また、粒径分布や粒子径などは、生体や農産物の模擬試料として広く用いられているイントラリピッド水溶液に関する計測データを用いた。体積分率が2%程度より低い場合、独立散乱理論と干渉散乱理論による散乱係数は同じとなり、それより大きい場合では干渉効果によって、干渉散乱理論の結果の方が値が小さくなった。この結果は、先行研究による単分散シリカ溶液の結果と同じ傾向であることから、多分散の効果は、定量的に寄与することが考えられた。 次に、イントラリポス溶液を用いて、粒径分布や光計測を行う準備を進めた。粒径分布は北海道大学工学研究院マテリアル分析・構造解析共用ユニットMASAOUにて光計測した。計測結果より、粒径分布はGauss分布の形をしていることが分かったが、計測原理上、高い体積分率では測定できず、今後は別の手法で測定することになった。 最後に、散乱係数を測定するため、ふく射輸送方程式に基づいた逆解析アルゴリズムを構築した。均一無限媒体における、ふく射輸送方程式の解析解と拡散近似した境界条件を用いて、半無限媒体における、ふく射輸送方程式の近似解を構築し、光伝播モデルとした。この近似が成立する光源ー検出点間距離を、ふく射輸送方程式の数値計算と比較することで評価した。
  • エリザベス・アーノルド富士財団:学術研究助成
    研究期間 : 2019年07月 -2020年02月 
    代表者 : 藤井 宏之
  • 大川情報通信基金:2017年度研究助成
    研究期間 : 2018年03月 -2019年03月 
    代表者 : 藤井 宏之
  • 微細構造を有する生体組織内のふく射輸送現象の解明に基づいた光学特性値の高精度計測
    日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 藤井 宏之
     
    本研究課題では,ふく射輸送方程式に基づいて,微細構造を有する生体組織内の光伝搬を明らかにした上で,in-vivoにおける生体組織の光学特性値を高精度に算出する逆解析アルゴリズムを開発することを目指した. 主な成果としては,生体のような強い異方性散乱媒体に対して,高速かつ高精度のふく射輸送方程式の数値計算手法を開発し,弾道光から拡散光へと遷移する長さと時間を光学特性値の関数として提示したこと,逆解析アルゴリズムを構築し,農産物や食品の光学特性値をin-vivo及びex-vivoで算出,構造特性との関係性を明らかにしたことである.
  • エリザベス・アーノルド富士財団:学術研究助成・舟橋重明記念奨励助成
    研究期間 : 2016年07月 -2017年04月 
    代表者 : 藤井 宏之
  • 秋山記念生命科学振興財団:研究助成(奨励)
    研究期間 : 2016年07月 -2017年03月 
    代表者 : 藤井 宏之
  • ノーステック財団:フードイノベーション創造支援事業
    研究期間 : 2015年07月 -2016年02月 
    代表者 : 藤井 宏之
  • ノーステック財団:若手研究人材・ ネットワーク育成補助金
    研究期間 : 2014年08月 -2015年02月 
    代表者 : 藤井 宏之

教育活動情報

主要な担当授業

  • 熱流体力学演習Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 熱力学第1法則、第2法則、蒸気、湿り空気、サイクル論 ナビエ・ストークス方程式、レイノルズ数、粘性摩擦抵抗、境界層、乱流、運動量・角運動量理論
  • 応用数学演習Ⅱ
    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 複素関数論,フーリエ解析,ラプラス変換,偏微分方程式

大学運営

委員歴

  • 2015年04月 - 2017年03月   日本機械学会 流体工学部門   広報委員 ニューズレター担当
  • 2015年01月 - 2015年10月   日本機械学会   2015年度年次大会 実行委員会 委員


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