Effect of a thin insulation film on thermal bubble‐triggered breakdown phenomena in liquid nitrogen

The effect of a thin insulation film on breakdown phenomena in liquid nitrogen in the presence of thermally induced bubbles is investigated with a cylinder‐to‐plane electrode. Bubbles were produced by a heater mounted in the cylinder, which is partially covered with an insulation film. The results show that the film's effect on the breakdown voltage is insignificant until a pore is formed on the film by a previous breakdown, but it becomes substantial after pore formation. The reduction rate in breakdown voltage after the pore formation depends on the gap length and heater power. The minimum breakdown voltage drops to the magnitude of the breakdown voltage in the gaseous phase at normal boiling temperature. The breakdown mechanism is discussed on the basis of bubble observation and numerical calculation of suspended‐bubble motion. © 1999 Scripta Technica, Electgr Eng Jpn, 127(4): 18–28, 1999     

Novel expansion/shrinkage modulation of 2D layered MOF triggered by clathrate formation with CO(2) molecules

Crystal-to-crystal transformation from a 3D interpenetrated-type MOF {[Cu(BF(4))(2)(bpy)(H(2)O)(2)] (bpy)} (1) to a 2D square-grid-type [Cu(BF(4))(2)(bpy)(2)] (2) (bpy = 4,4'-bipyridine) was observed. It was derived from dehydration and confirmed by in situ FT-IR, TG, and elemental analysis. Moreover, we elucidate the novel expansion/shrinkage dynamic modulation of 2 triggered by clathrate formation with gas molecules.     

Estimation method for the light extraction efficiency of light-emitting elements with a rigorous grating diffraction theory

The light extraction efficiency of a light-emitting element with microstructured surface is analyzed with a rigorous grating diffraction theory. The grating theory reveals an improvement of extraction efficiency due to diffraction of light by the surface microstructure. The simulation results show that the improvement of extraction efficiency is due mainly to the reflected diffraction rather than to the transmitted diffraction. A part of total-internal-reflection light is diffracted into directions at less than the critical angle. Extraction efficiency is improved by multiple reflection and diffraction of light in a high-refractive-index layer. We propose a simple design method for an efficient surface microstructure from the viewpoint of reflected diffraction.     

Spectral restoration and energy resolution improvement of electron energy-loss spectra by Pixon reconstruction: II. Application to practical ELNES analysis of low SNR

We applied Pixon deconvolution as introduced in Part I to several practical, examples of low signal-to-noise ratio (SNR), electron energy-loss spectra with a goal toward restoring their fine spectral features and/or improving the energy resolution. We demonstrate that by directly fitting the two-dimensional spectral data recorded on the CCD; the method enables us to reveal fine spectral structures. Consequently, Pixon reconstruction extends the ability to probe electronic states in very spatially localized areas, a capability currently unique to our method.     

Crystal growth and scintillation properties of Er-doped Lu3Al5O12 single crystals

Er-doped Lu₃Al₅O₁₂ (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down (μ-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under ²⁴¹Am α-ray excitation indicated host emission at approximately 350 nm and Er³⁺ 4f-4f emissions. According to the pulse height spectra recorded under γ-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The γ-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 μs and 6-10 μs).     

Eu-doped LiF-SrF2 eutectic scintillators for neutron detection

Eu²⁺ 0.05%, 0.1%, and 0.2% activated LiF-SrF₂ eutectic scintillators were prepared by the Bridgman method using ⁶Li enriched (95%) raw material. The α-ray-induced radio luminescence spectra showed intense emission peak at 430 nm due to an emission from Eu²⁺ 5d-4f transition in the Eu:SrF₂ layers. When excited by ²⁵²Cf neutrons, all the samples exhibited almost the same light yields of 5000-7000 ph/n with a typical decay times of several hundreds ns.     

Size-controlled recrystallization of fullerene by gas–antisolvent process

Gas–antisolvent (GAS) process using CO₂ successfully prepared crystals of fullerene (C₆₀) from a toluene solution through a precipitation. Particle sizes of precipitated C₆₀ could be easily controlled by changing the initial pressurization rate of CO₂, the temperature at the initial pressurization, and the quantity of C₆₀. Fullerene particles obtained by GAS method had regular octahedral shapes, whereas the particles obtained by adding liquid ethanol as an antisolvent to C₆₀ solution did not have such shape. Particle sizes could be changed in a range of 1.0–8.5 μm by GAS method; they were wider than the range of particles obtained by ethanol addition (0.7–1.8 μm).     

GISELA – GIS-based evaluation of land use and agriculture market analysis under global warming

One of the important future issues is how agriculture production can meet the future demand increase due to the population and the income growth. Global warming would give both positive and negative impacts on them. Agriculture is often expected to supply biofuels to meet the growing transportation energy demand and the warming control policy. GISELA – GIS-based evaluation for land use and agriculture production model – is developed to evaluate the current and the potential cropland for rice, wheat, maize and soy-beans production under climate changes. We also assess the food and the feed demand based on the historical regional statistics for world into 18 regions. Finally, we assess the future food market integrating the above supply and demand conditions developing a dynamic optimization model, GISELA. Current GISELA findings are as follows: (1) potential cropland in south America will be extensively cultivated, (2) market price of wheat and soy will gradually go up while that of maize is almost stable in medium yield case, and (3) in the low-yield case, all crop prices hike rapidly in the mid of this century.     

Cost efficiency of Japanese steam power generation companies: A Bayesian comparison of random and fixed frontier models

This study analyses and compares the cost efficiency of Japanese steam power generation companies using the fixed and random Bayesian frontier models. We show that it is essential to account for heterogeneity in modelling the performance of energy companies. Results from the model estimation also indicate that restricting CO₂ emissions can lead to a decrease in total cost. The study finally discusses the efficiency variations between the energy companies under analysis, and elaborates on the managerial and policy implications of the results.     

Electronic speckle pattern interferometry based on spatial fringe analysis method using two cameras

A new speckle measurement method is proposed by applying a spatial phase shifting method to multi-camera technology in order to perform a high resolution, high speed, and large deformation measurement. It is confirmed that the alignment of optical elements in this method is easier than the ordinary multi-camera methods because the optical system uses only two cameras. The validity of principle of the method is discussed by the results of experiments. It is shown that measurement precision of this method is about 1/50 wavelength in a small deformation measurement. Furthermore, the method is improved for a large deformation measurement method by accumulating the results of the small continuous deformation measurement. The optimum sampling process of the large deformation of an object is proposed in order to detect the phase map of the large deformation. It is confirmed that the large deformation can be precisely measured by this method.