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Search Results: 1 - 10 of 669 matches for " Yuichi Nakazaki "
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Wide and Fast Wavelength-Swept Fiber Laser Based on Dispersion Tuning for Dynamic Sensing
Shinji Yamashita,Yuichi Nakazaki,Ryosei Konishi,Osamu Kusakari
Journal of Sensors , 2009, DOI: 10.1155/2009/572835
Abstract: We have developed a unique wide and fast wavelength-swept fiber laser for dynamic and accurate fiber sensing. The wavelength tuning is based on the dispersion tuning technique, which simply modulates the loss/gain in the dispersive laser cavity. By using wideband semiconductor optical amplifiers (SOAs), the sweep range could be as wide as ~180 nm. Since the cavity contains no mechanical components, such as tunable filters, we could achieve very high sweep rate, as high as ~200 kHz. We have realized the swept lasers at three wavelength bands, 1550 nm, 1300 nm, and 800 nm, using SOAs along with erbium-doped fiber amplifiers (EDFAs), and in two laser configurations, ring and linear ones. We also succeeded in applying the swept laser for a dynamic fiber-Bragg grating (FBG) sensor system. In this paper, we review our researches on the wide and fast wavelength-swept fiber lasers.
Recent Advances in X-Ray Structures of Metal-Phenoxyl Radical Complexes  [PDF]
Yuichi Shimazaki
Advances in Materials Physics and Chemistry (AMPC) , 2013, DOI: 10.4236/ampc.2013.31A009
Abstract:

An “experimental” valence state of metal complexes is sometime different from the “formal” oxidation state, especially in the species having redox active ligands. This difference can be seen in biological system, such as iron(IV)-porphyrin π-cation radical in some heme proteins and copper(II)-phenoxyl radical in galactose oxidase (GO). Although structural characterizations of these species by X-ray diffraction methods have been rare due to their stability, some artificial metal-phenoxyl radical complexes have been synthesized and successfully characterized by X-ray crystal structure. In this review, syntheses and X-ray crystal structures of the one-electron oxidized metal-phenolate complexes, metal- phenoxyl radical, and high-valent metal phenolate species are discussed.

Relationships among Risk Assessment, Risk Perception and Acceptance Model of the Residents near Nuclear Power Plants in Japan  [PDF]
Yuichi Otsuka
Open Journal of Safety Science and Technology (OJSST) , 2015, DOI: 10.4236/ojsst.2015.52005
Abstract: This study aims at revealing the relationships among risk assessment result, risk perception model and risk acceptance model of the residents near nuclear power plants in Japan. Risk acceptance model is based on the trust of resident to nuclear power plants (NPPs) companies. The risk perception of the residents is very fragile and is not always based on objective technical knowledge. In addition, there are two models of risk acceptance: traditional trust model and salient value similarity model. In order to discuss the risk communication framework between NPPs with residents, applicability of two modes on the perception of the residents should be investigated. The author collected questionnaire from local resident near Kashiwazaki-Kariwa NPP in Niigata, Japan. Severity of risk is significantly affected by the extents of risks, not by amount of knowledge. Radiation relating hazard is normally evaluated higher risk. Risk acceptance level is significantly related to the factors of social benefits and trust to the NPPs company, not by regional interest nor amount of knowledge. Furthermore, value similarity model was not significant in this study. The results demonstrated that risk acceptance model of local residents near NPPs could be arranged by traditional trust model. In order to establish mutual trustworthy relationships between local residents and NPPs engineer, expert knowledge in nuclear power, communication skills, and expertise in safety are necessary to the engineers.
A Theoretical Study on Van Der Pauw Measurement Values of Inhomogeneous Compound Semiconductor Thin Films  [PDF]
Toru Matsumura, Yuichi Sato
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.15048
Abstract: The influence of intermixing heterogeneous regions that have different electrical properties from the base materials on van der Pauw measurement values was theoretically studied by computer simulation using the finite-element method. The measurement samples selected were thin films of inhomogeneous semiconductors. Calculated electrical properties, such as resistivity, carrier density, and mobility of the thin films, varied in predictable ways when heterogeneous regions were dispersed in wide ranges over the samples. On the other hand, the mobility of the thin films showed a different change when heterogeneous regions were locally concentrated in the measurement samples.
Engineering Management Framework to Achieve Safety of a Service of an Organization Based on Social Acceptance  [PDF]
Yuichi Otsuka, Hiroshi Noguchi
Open Journal of Safety Science and Technology (OJSST) , 2012, DOI: 10.4236/ojsst.2012.21003
Abstract: We aim at a management framework of an organization in order to achieve its safety in a limited case for a system in-volving the organization for the service, its users and the surrounding society. The proposed framework is possible to allow safety managers to specify tasks involving safety measures based on the concept of “a study of safety”. In the beginning, we discuss the definitions of safety and acceptance, which will be the target of safety management. Next, problems in which the hierarchy of components in the safety systems involves are noted. We then propose the following details of the management framework to achieve the safety of the service of the organization based on acceptance by the surrounding society. Applications of the components in the proposed framework are effectively demonstrated. The shown application can aid in visualizing a way of specification of the proposed concept in a target system.
Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms  [PDF]
Yuichi S. Hayakawa
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.46A2002
Abstract:

A waterfall highlights the locus of active fluvial erosion of bedrock, and its mechanism has been the subject of several studies; however, erosional processes remain to be clarified for specific rock structures composing a waterfall. Herein, the detailed morphology of cliffs around a waterfall is examined by a terrestrial laser scanning (TLS) approach to analyze erosional processes occurring in the cliffs. The study site is Kegon Falls in Japan, which has a vertical drop of surface water from the top of its cliff and groundwater outflows from its lower portion. The entire cliff is mostly overhanging and minor rockfalls are often observed. The latest major rockfall occurred in 1986, causing an approximate 8-m upstream shift of the waterfall lip. From the point cloud obtained by TLS measurement, a digital elevation model on a vertical plane was generated, and cross-sectional profiles were extracted. A distinct 5- to 10-m depression was found at the bottom of the upper andesite layer of the waterfall cliff, which appears to have been formed by freeze-thaw and wet-dry weathering following the upstream shift of the surface water drop. Stability analysis of the waterfall cliff with an undercutting notch indicates that the igneous rock composing the cliff is sufficiently strong to maintain its current overhanging shape and that catastrophic collapse of the entire waterfall face rarely occurs. Following the formation of the depression, the upper cliff face appears to have been gradually eroded by gravitational collapses of relatively small blocks bounded by columnar and platy joints.

Direct Measurement of Medical Linear Accelerator Electron Beam Width at Scattering Foil Position  [PDF]
Tomohiro Shimozato, Yuichi Aoyama
International Journal of Medical Physics,Clinical Engineering and Radiation Oncology (IJMPCERO) , 2017, DOI: 10.4236/ijmpcero.2017.61007
Abstract: Purpose: The aim of this study was to develop a method for the direct measurement of electron beam width and distribution at the scattering foil on the carrousel in a medical linear accelerator gantry head, which differs from an existing indirect method for measuring the focal spot size using a camera or metallic slit located outside the gantry head. Methods: The electron beam emitted by the linear accelerator was used to irradiate radiochromic film mounted on the scattering foil on the carrousel, which was not used for clinical treatment. The electron beam width at the scattering foil position was then evaluated using the full width at half maximum of the Gaussian distribution approximated from each one dimensional distribution of the irradiated radiochromic film. Results: The electron beam width at the scattering foil position was found to be 3.1 to 6.4 mm in the crossline direction and 2.8 to 5.5 mm in the inline direction with electron energy of 4 to 16 MeV. The two-dimensional distribution of the electron beam was therefore elliptical or distorted in shape, not circular. Conclusions: Direct measurement of the electron beam width at the scattering foil in the carrousel of a medical linear accelerator is possible, though the use of lower sensitivity film in addition to indirect methods is expected to bring about better results. However, as this method does not allow for direct measurement of the incident angle of the accelerated electron beam, further improvements and refinements are still needed.
Application of Hydration Thermodynamics to the Evaluation of Protein Structures and Protein-Ligand Binding
Yuichi Harano
Entropy , 2012, DOI: 10.3390/e14081443
Abstract: Discovering the mechanism that controls the three-dimensional structures of proteins, which are closely related to their biological functions, remains a challenge in modern biological science, even for small proteins. From a thermodynamic viewpoint, the native structure of a protein can be understood as the global minimum of the free energy landscape of the protein-water system. However, it is still difficult to describe the energetics of protein stability in an effective manner. Recently, our group developed a free energy function with an all-atomic description for a protein that focuses on hydration thermodynamics. The validity of the function was examined using structural decoy sets that provide numerous misfolded “non-native” structures. For all targeted sets, the function was able to identify the experimentally determined native structure as the best structure. The energy function can also be used to calculate the binding free energy of a protein with ligands. I review the physicochemical theories employed in the development of the free energy function and recent studies evaluating protein structure stability and protein-ligand binding affinities that use this function.
A Compact Computing Environment For A Windows PC Cluster Towards Seamless Molecular Dynamics Simulations
Yuichi Tsujita
Lecture Notes in Engineering and Computer Science , 2010,
Abstract:
Feasibility Study of Effective Remote I/O Using a Parallel NetCDF Interface in a Long-Latency Network
Yuichi Tsujita
Lecture Notes in Engineering and Computer Science , 2008,
Abstract:
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