Reflectance spectra of extreme ultraviolet mirrors for synchrotron radiation

Reflectance spectra have been measured for many materials in the wavelength range from 90 Å to 400 Å. The angle of incidence ranged from 20° to 85°. The samples were chemical-vapor-deposited silicon carbide (CVD-SiC), a single crystal of silicon with (100) surface, fused quartz, zerodur, pyrex, gold, platinum, copper and two kinds of steel. To obtain reflectances for surfaces for practical use, measurements were made on surfaces sufficiently exposed to air. Reflectances for s-polarized light (R_s) were measured for all samples. On CVD-SiC, gold and platinum, reflectances for p-polarized light (R_P) were also observed. At short wavelengths and large angles of incidence, the difference between R_s and R_P is small, and R_P happened to exceed R_s in contrast to the result from the Fresnel equation. This may be due to the deviation of the present surfaces of mirrors from an ideal plane. Reflectance spectra of surfaces prepared by some feasible techniques are also presented.     

Studies of the strong coupling and weak coupling methods in FSI analysis

The weak coupling methods in fluid–structure interaction analysis are newly classified into three types; the weak coupling method for solving structures with interfaces, the weak coupling method for solving fluids with interfaces, and the weak coupling method for solving both fluids and structures with interfaces. The consistent added matrices of these weak coupling methods are derived from the condensation of the strong coupling formulation. Some approximations for the consistent added matrices, which can avoid the matrix coupling, are proposed. The reasons for convergence difficulty in the weak coupling methods are clarified. A number of numerical results are presented to investigate the convergence properties and computational efficiency of these methods. Copyright © 2004 John Wiley & Sons, Ltd.     

Time-dependent characteristics of the nonequilibrium condensation in subsonic flows

High-speed moist air or steam flow has long been of important subject in engineering and industrial applications. Of many complicated gas dynamics problems involved in moist air flows, the most challenging task is to understand the nonequilibrium condensation phenomenon when the moist air rapidly expands through a flow device. Many theoretical and experimental studies using supersonic wind tunnels have devoted to the understanding of the nonequilibrium condensation flow physics so far. However, the nonequilibrium condensation can be also generated in the subsonic flows induced by the unsteady expansion waves in shock tube. The major flow physics of the nonequilibrium condensation in this application may be different from those obtained in the supersonic wind tunnels. In the current study, the nonequilibrium condensation phenomenon caused by the unsteady expansion waves in a shock tube is analyzed by using the two-dimensional, unsteady, Navier-Stokes equations, which are fully coupled with a droplet growth equation. The third-order TVD MUSCL scheme is applied to solve the governing equation systems. The computational results are compared with the previous experimental data. The time-dependent behavior of nonequilibrium condensation of moist air in shock tube is investigated in details. The results show that the major characteristics of the nonequilibrium condensation phenomenon in shock tube are very different from those in the supersonic wind tunnels.     

Neodymium-doped silica-based planar waveguide lasers

Fabrication and lasing characteristics of Nd-doped P₂O ₅-SiO₂ core planar waveguide lasers are described. CW oscillation at a wavelength of 1052.5 nm was successfully demonstrated in 0.2 wt%-Nd-doped silica-based planar waveguides fabricated on a silicon substrate by flame hydrolysis deposition and reactive ion etching. The lasing threshold and slope efficiency were optimized in an 8-μm-wide waveguide, in which a lasing threshold pump power of 26 mW and a slope efficiency of 2.0% were obtained for 805-nm pumping. The measured lasing characteristics agreed with theoretical characteristics calculated by employing finite-element waveguide analysis, indicating that the waveguide structure was well controlled by the developed waveguide fabrication technique. The possible lasing characteristics of the waveguide lasers are discussed based on this agreement. The attenuation and emission properties of the waveguides are also described     

Determination of fluoride ion in animal bone by microdiffusion analysis

A microdiffusion analysis method for the determination of fluoride ion in animal bone sample was established by using a new diffusion cell. The cell is equipped with a water jacket to control the temperature. The space inside the cell is divided by a crossed-beam stand into top and bottom parts. In the bottom part, derivatization of fluoride ion to trimethylfluorosilane (TMFS) by hexamethyldisiloxane as the reagent occurs, with the volatile TMFS being absorbed into alkali placed in an open-top cup supported by the stand. The cell is placed on a magnetic stirrer to rotate the stirring bars in both reaction and absorption solutions. Stirring and elevation of temperature increase the reaction rates. Maintaining the cell at 40 degrees C for 3 h is sufficient for complete extraction of fluoride ion from the bone and its recovery. With our method, more than 10 micrograms/g of fluoride ion in bone can be assayed with a coefficient of variation of less than 3%. The fluoride levels of various rat bones were clarified.     

A GTO DC Circuit Breaker Controlled by a Single-Chip Microcomputer

Power semiconductor circuit-breaker application suggests the need for microcomputers that provide firing control, excellent dc short-circuit fault interrupting performance, precise overload protection of themselves, as well as high reliability with minimum components. This paper deals with the prototype dc 1500 V GTO (gate turnoff thyristor) circuit breaker controlled by a single-chip microcomputer. Emphasis is on the GTO junction temperature observation.     

Gain switching of waveguide laser based on Nd-doped silica planarlightwave circuit pumped by laser diodes

A gain-switched Nd-doped silica waveguide laser pumped by laser diodes (LDs) was successfully realized. The light from two CW operated and modulated LDs was synthesized and used to investigate gain switching characteristics under various pump conditions. Pulses with a peak power of 1.0 mW and a full width at half maximum of 480 ns were obtained at a repetition rate of 150 kHz. The average modulated pump power was 17 mW and the bias pump power was 35 mW. A gain-switched pulse repetition rate of 25 to 150 kHz was achieved by controlling the pump power of a CW operated and a modulated LD     

Comparison of the effects of hypercholesterolaemia on relaxation responses in aortas of spontaneously hypertensive rats and Dahl salt-sensitive rats

1. We investigated the effects of hypercholesterolaemia on relaxation responses in thoracic aortas isolated from two different types of hypertensive rats; spontaneously hypertensive rats (SHR) and Dahl salt-sensitive rats (DSR). 2. All rats fed the high cholesterol diet for 8 weeks showed a significant increase in the serum cholesterol level. The high cholesterol diet did not change the blood pressure of SHR, but increased that of hypertensive DSR fed a high-salt diet. 3. In aortas of SHR, the high-cholesterol diet did not change the endothelium-dependent and -independent relaxation induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively. 4. In aortas of hypertensive DSR, the high-cholesterol diet notably reduced the ACh-induced relaxations and slightly reduced SNP-induced relaxation. 5. These results suggest that hypercholesterolaemia causes greater impairment of endothelium-dependent relaxation in rat aorta with salt-induced hypertension than genetic hypertension.     

Cyclic stress-strain curves at finite strains under high pressures in crystalline polymers

The cyclic torsional stress-strain behaviour for crystalline polymers of polyethylene (PE), polypropylene (PP) and polyoxymethylene (POM) was investigated at finite strain amplitude under hydrostatic pressure up to 2000 kgf cm^–2. The following features for the cyclic stress-strain curves were indicated. (1) Two types of cyclic stress-strain curve were observed: one was a PE type where the present hysteresis loop was not so affected by the strain histories, and the other was a PP type where the hysteresis loop was greatly affected by the previous maximum strain. (2) In the pressure ranges tested, the shape of the cyclic stress-strain curves for the polymers used was not essentially altered by the hydrostatic pressure. (3) The stress-strain curves after the first strain reversal showed an unusual shape which has not been observed for metals. (4) The decrease in cyclic softening caused by the stress amplitude with increasing number of cycles at a constant strain amplitude test occurred irrespective of the hydrostatic pressure. (5) The stress-strain behaviour at a partly reversed cyclic loading was different from that expected at a fully reversed cyclic loading.