Melt synthesis of Eu-doped oxide phosphors using arc-imaging furnace

To synthesize various complex oxide materials and their solid solutions, we applied a novel “melt-synthesis technique” rather than conventional solid-state reaction techniques. Rapid synthesis methods to develop those double oxides have been strongly anticipated. During melt synthesis, the mixture of oxides or their precursors is melted rapidly (1–60 s) in an arc-imaging furnace using strong light radiation. A spherical molten sample with multiple homogeneously mixed cations was solidified directly on a copper hearth with rapid cooling of ca. 10² °C/s.We studied the synthesis of A₂BO₄ type double oxides (AA′)₂BO₄ (A = Sr²⁺, Ca²⁺, A′ = La³⁺, Gd³⁺, Y³⁺, Eu³⁺, B = Al) using this method. Homogeneous samples with Eu³⁺ dopants were synthesized using liquid phase mixing in a few seconds, which is much faster than diffusions of ions in solid phase. Red fluorescence under the irradiation of ultraviolet light (254 and 365 nm) was observed. The excitation band shifted.     

PARC process for an advanced PUREX process

An advanced PUREX process, the PARC process, has been developed which aims to reduce the radioactive waste volume containing TRU elements (neptunium, plutonium, americium and curium) and the environmental hazard risk due to long-lived nuclides such as technetium-99, carbon-14 and iodine-129. This paper describes the concept of the PARC process and major results of chemical flow sheet experiments using spent fuels.     

Field emission property of nanostructured tungsten formed by helium plasma irradiation

Field emission property of nanostructured tungsten formed by the exposure to a helium plasma is measured to investigate the initiation process of arcing in nuclear fusion devices. Field emission current from the nanostructured tungsten and tungsten with helium bubbles was significantly higher than that from the polished tungsten specimen. However, field enhancement factor was on the order of 100, which was almost comparable to that of bulk tungsten; the increase in the field emission current is attributed to primarily an increase in the effective emission surface area. From the calculation of thermo-field emission current from a heated tungsten, it is thought that a significant current emission can be still initiated even when the field enhancement factor is not so high when tungsten is exposed to high density plasmas such as the one accompanied with ELMs.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS XXXVI. SYNTHESIS OF CRYPTOMELANE-TYPE HYDROUS MANGANESE DIOXIDE AS AN ION-EXCHANGE MATERIAL AND THEIR ION-EXCHANGE SELECTIVITIES TOWARDS ALKALI AND ALKALINE EARTH METAL IONS

Abstract

Hydrous manganese dioxide in a cryptomelane-type showed an excellent ion-exchange selectivity for K⁺, Rb⁺and Ba²⁺ ions having the effective ionic radii of about 1.4 Å. Log-log plots of distribution coefficients for alkali and alkaline earth metal ions vs. [HNO₃] yielded a straight line with a slope of ?1 and ?2, respectively, indicating the “ideal” ion-exchange mechanism. The stoichiometry of ion-exchange reactions was also established for the uptake of macro-amounts of alkali metal ions in nitrate media.     

Combinatorial synthesis of phosphors using arc-imaging furnace

We have applied a novel ‘melt synthesis technique’ rather than a conventional solid-state reaction to rapidly synthesize phosphor materials. During a synthesis, the mixture of oxides or their precursors is melted by light pulses (10–60 s) in an arc-imaging furnace on a water-cooled copper hearth to form a globule of 1–5 mm diameter, which is then rapidly cooled by turning off the light. Using this method, we synthesized several phosphor compounds including Y₃Al₅O₁₂:Ce(YAG) and SrAl₂O₄:Eu,Dy. Complex phosphor oxides are difficult to produce by conventional solid-state reaction techniques because of the slow reaction rates among solid oxides; as a result, the oxides form homogeneous compounds or solid solutions. On the other hand, melt reactions are very fast (10–60 s) and result in homogeneous compounds owing to rapid diffusion and mixing in the liquid phase. Therefore, melt synthesis techniques are suitable for preparing multi component homogeneous compounds and solid solutions.     

An analysis of the field acceleration method and of vector control of induction motors

The two-axis theory and vector control based on this theory are well known. On the other hand, Yamamura has proposed the phase segregation method (spiral vector method) for the analysis of induction motors along with the field acceleration method (FAM). In this paper these analytical and control methods are compared. We begin by analyzing the equations for phase segegation, which contain information derived from the three-phase stator and rotor equations. We next demonstrate that the vector control system for constant rotor flux is obtained from the type T-I type field acceleration method when the transient term is zero. By By using the equivalent circuit for a T-I transient, we readily obtain the desired vector control system, because the circuit is identical to the steady-state circuit when the rotor flux is constant. An analytical solution of the transient response for the vector control system is obtained for arbitrary initial conditions. Finally, the stability of type T-II FAM is discussed, with special emphasis on the effect of changes in stator resistance, by computing the torque transfer function. When the stator resistance is correctly estimated, pole-zero cancellation occurs on the imaginary axis.     

Stability analysis of a controlled-current source-fed induction motor vector control system without a speed sensor

One of the representative vector-controlled induction motor drive systems without a speed sensor is composed of a rotor flux estimator, a PI torque current controller and a conventional vector-controlled current source. However, the stability analysis of this system has not been reported. In this paper, the flux estimator is interpreted as a flux observer. Then a linear model of the system is proposed by deriving the equations of the flux estimator in a synchronously rotating reference frame. By computing the trajectories of the poles and zeros and the transient responses, the following results are obtained. (1) If the rotor flux is estimated using only the stator equations (voltage model), the system becomes unstable when the actuator stator resistance is smaller than the value used by the controller. (2) By choosing a small time constant of the first-order lag element in the flux estimator (reciprocal number of observer gain), the poles and zeros on the imaginary axis move to the stable region. However, another pair of poles has reverse performance. (3) From the viewpoint of stability, the gain of the PI torque current controller should be chosen as large as possible and the stator and rotor resistances in the controller should be set to values smaller than their actual values.     

Conditioning of Meat with Raw Soy Sauce and Its Proteinases: Their Effects on the Quality of Beef

This investigation demonstrated that raw soy sauce added to beef in the process of tenderization was effective in improving its sensory quality. To estimate the contributions of proteinases occurring in the raw soy sauce, the degradation of myofibril and collagen was investigated by using the inhibitors, potato inhibitor, ethylenediaminetetraacetic acid (EDTA) and pepstatin which inhibit serine-, metallo-, and aspartic proteinases, respectively. A serine proteinase was most greatly involved in the degradations of both myofibril and collagen. Electrophoretic patterns of myofibril degraded by a purified serine proteinase coincided well with those of myofibril treated with the raw soy sauce per se.     

Reconstruction and semi-transparent display method for observing inner structure of an object consisting of multiple surfaces

A system of techniques is proposed for reconstructing the original object from multi-layered cross-section data including open contour lines and for displaying the inner structure as well as the outside using a stereoscopic semi-transparent image and cut-away views. The procedure is divided into three steps: 1) selection/construction of contour lines for each cross-section, 2) reconstruction of the object based on the contour line information including cutting away part of the reconstructed object with a convex polyhedron, and 3) display of the reconstructed image. Control parameters are provided to allow easy and reliable observation of multi-layererd structures.