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51.
Tien-Hsiu Tsai Takumi Hamaguchi Hiraku Iramina Mitsuhiro Nakamura 《Journal of Nuclear Science and Technology》2019,56(2):210-220
Filter-based energy-resolved X-ray computed tomography (CT) is an approach for implementing energy-resolved CT imaging using a flat-panel-detector-based cone-beam system. In this study, we performed experiments with a 20-cm-diameter phantom on a clinical X-ray imager. The material density results showed good agreement with the ideal values. We also propose an improved method for obtaining the detector response function and the X-ray spectrum, which requires fewer measurements and will be practical for future clinical use. Issues such as scatter and image noise remain to be addressed. 相似文献
52.
Mitsuhiro Horade Sommawan Khumpuang Susumu Sugiyama 《Microsystem Technologies》2008,14(9-11):1695-1698
Microfabrication technique using SR ablation for 3-D polytetrafluoroethylene (PTFE) structure is reported in this work. First of all, we investigated necessary basic data for the fabricated structure like the processing depth and the etching rate, etc. And, the exposure energy distribution was given to the surface of polytetrafluoroethylene by using the plane pattern to cross-section transfer (PCT) technique, 3-D microstructures was fabricated. To establish three dimension of highly accurate PTFE processing technology, we are researching the application to the device. 相似文献
53.
Polarisation mode dispersion in elliptical-core single-mode fibres has been measured by a spatial technique based on a visibility maximum position measurement in an interferometer. Using the technique, wavelength dependence of the modal dispersion has been measured by varying optical source wavelengths between 821 and 904 nm. As a result, contribution of geometrical and strain birefringences on the modal dispersion has been evaluated, and normalised frequency dependence of the modal dispersion has been clarified. 相似文献
54.
Characteristics of a periodic structure waveguide with a finite width are studied theoretically and numerically. Propagation constants of two orthogonally polarized fundamental modes converge to values which are different from each other, when the total periodic structure width exceeds twice the wavelength. The asymptotic characteristic equation is derived analytically. The normalized frequencyV of the high-index layers must be less than unity in order that the optical energy does not localize in the high-index layers. Both the magnitude of the birefringence and the effective refractive index in the form-birefringent media can be controlled by varying the thickness of the high-index layer and the thickness ratio of the high- and low-index materials. 相似文献
55.
Wavelength dependence of polarisation mode dispersion in an elliptical core single-mode fibre was measured by a spatial technique based on the visibility maximum position measurement in the 0.67?1.25 ?m wavelength region. Normalised frequency dependence of the modal dispersion due to thermal-stress-induced birefringence was clearly obtained from the measurement and numerical calculation of normalised delay time difference using the point-matching principle. 相似文献
56.
Summary Cloud points were observed in the blends of deuterated polystyrene (PSD) and hydrogeneous poly (vinyl methyl ether) (PVME) by means of temperature scanning Small Angle Neutron Scattering (SANS) technique. The scattering function in the miscible region can be described by the random phase approximation results calculated by de Gennes. This scattering function can also be expressed in the Ornstein-Zernike form in the small q region. A correlation length and spinodal point can then be determined from this critical fluctuation approach. 相似文献
57.
A nondestructive method is proposed for evaluating power coupling coefficients of directional couplers contained in an optical integrated circuit. This technique, which is based on optical heterodyne interferometry, makes it possible to obtain individual coupler element information without removing the element from the optical circuit. General N -channel waveguide coupling characteristics are analyzed, and they are experimentally evaluated for two- and four-channel waveguides that have been practically designed as frequency multi/demultiplexers operating in the 1.55-μm-wavelength region 相似文献
58.
Although natural convection is frequently encountered in various chemical processes, Rayleigh number (Ra) cannot be defined fully in shear-thinning fluid systems. In particular, the velocity scale, which is necessary to estimate the effective viscosity of the system, should be discussed carefully. Thus, in this study, the representative velocity scale of Rayleigh-Bénard (RB) convection, which is a typical example of natural convection, with shear-thinning fluids was investigated based on the velocity fields obtained using computational fluid dynamics. Numerical simulations revealed that the critical temperature difference at which RB convection starts to fully develop decreases with an increase in the shear-thinning property. The shear-thinning property also induced subcritical bifurcation. In addition, the velocity scale of convection increases with an increase in the shear-thinning property. Thus, the shear-thinning property is considered to accelerate convection. Compared with several types of velocity scales used by other researchers, significant deviations from the actual scale were observed. Therefore, a new type of velocity scale, including the buoyant to viscous force ratio, arbitrary parameter, and thermal diffusivity, was proposed. The proposed velocity scale allowed an approximate estimation of the actual velocity scale. Although further investigation of the validity is necessary with varying geometries and rheological parameters, this velocity scale will be useful for controlling RB convection with Newtonian/shear-thinning fluids. 相似文献
59.
60.
Xi‐Ping Deng Lun Shan Shinobu Inanaga Mitsuhiro Inoue 《Journal of the science of food and agriculture》2005,85(8):1379-1388
The greatest fear of global climate change is drought. World‐wide, 61% of countries receive rainfall of less than 500 mm annually; domestication of wheat first occurred in such a semiarid region of southwestern Asia, and it seems that wheat foods originally came from dryland gardens. Wheat plants respond to drought through morphological, physiological and metabolic modifications in all plant parts. At the cellular level, plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought‐induced genes have been identified in a wide range of wheat varieties, a molecular basis for wheat plant tolerance to water stress remains far from being completely understood. The rapid translocation of abscissic acid (ABA) in shoots via xylem flux, and the increase of ABA concentration in wheat plant parts correlate with the major physiological changes that occur during plant response to drought. It is widely accepted that ABA mediates general adaptive responses to drought. For a relatively determinate target stress environment, and with stable genotype × environment interaction, the probability for achieving progress is high. This approach will be possible only after we learn more about the physiology and genetics of wheat plant responses to water stress and their interactions. The difficulties encountered by molecular biologists in attempting to improve crop drought tolerance are due to our ignorance in agronomy and crop physiology and not to lack of knowledge or technical expertise in molecular biology. Copyright © 2005 Society of Chemical Industry 相似文献