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Considering the applications to in-line testing of products, water-free imaging technique is required. This study described defect imaging technique using a scanning laser source. Laser beam was emitted onto a surface of a plate, and then guided waves excited at the laser source were detected by ultrasonic transducers fixed on the plate surface. For a plate with rounded defects, amplitude distributions obtained by scanning the laser source corresponded to thickness distributions, but for plates with rectangular notches, unwanted artifacts were seen due to reflection, diffraction, and ultrasonic attenuation. Then, using multiple receiving transducers and synthesizing multiple images, distinct defect images were obtained for a flat plate and a curved plate with rectangular notches. [ABSTRACT FROM AUTHOR]

Strongly magnetized white dwarfs (WDs) are able to accelerate particles like rotating neutron-star pulsars. If magnetized WDs are a new Cosmic-ray origin, they should be a quiet but numerous accelerators, giving important contributions of low-energy cosmic-rays. We performed a high sensitive search for possible hard X-ray emission from the fast rotating WD, AE Aquarii with Suzaku. The object has a magnetic field with 105 Gauss and a rapid spin period of 33 sec. From 100 ksec dataset of Suzaku XIS and HXD, we have discovered spiky pulsations like pulsars in the hard X-ray band of over 4 keV, in addition to the well-known thermal modulation in the softer band. In order to account for the hard X-ray signals with the HXD, the X-ray spectrum requires an additional hard X-ray component on the well-known thermal emissions with temperatures of 0.5 and 2.9 keV. Combined with results from timing analyses, spectral shapes and flux, we concluded that the hard X-ray pulsations should be a non-thermal origin, for example, possible Synchrotron emission with sub MeV electrons. Thus, the object must be a first discovery of a WD equivalent of a neutron star pulsar. [ABSTRACT FROM AUTHOR]

In guided wave inspection for pipes, defect characterization is performed by echoes from defects. However, since detected signals become very complex due to mode conversion and multiple reflections, wave mechanics in a pipe with defects are not well studied. In this study, therefore, visualization technique for guided waves in a pipe is developed. In order to visualize guided wave propagation in a pipe, we need to scan an ultrasonic probe and measure ultrasonic waves at many points on a surface of a pipe. Position and posture of a laser doppler vibrometer are controlled by a robot arm, and ultrasonic vibration is detected at arbitrary points from arbitrary laser beam direction. Using the laser scanning technique, reflected guided waves from a shallow round defect was observed in the visualization results. From the defect, reflected waves propagated spirally in the oblique direction. From the view point of guided wave, the spiral waves were very high order modes that have not been measured in guided wave inspection. This result shows that such high order guided wave modes should be useful for defect characterization as well as low order modes. [ABSTRACT FROM AUTHOR]

An improved pulse compression technique was developed for long range testing using dispersive guided waves. This technique improves signal-to-noise ratio (SNR) of the guided wave signals and compensates for the wave distortion caused by dispersion characteristics of the guided wave. A fast calculation algorism was designed. It consists of integrations of both cross-correlation for pulse compression and compensation of velocity dispersion in wave number domain. Efficiency of the technique was verified experimentally, in which the results showed both spatial resolution and signal-to-noise ratio were improved. [ABSTRACT FROM AUTHOR]

Defects in a railhead and web can be detected with rail inspection cars and rail inspection tools equipped with special transducers such as wheel probes. However, bottom edges of rails, easily damaged regions due to contact to soil and fastening, are blind zones for the conventional ultrasonic inspection technique in which signals are input from a railhead. In this paper, inspection technique for defects in bottom edges of rails using guided waves were described. Dispersion curves for a rail obtained by a semi analytical finite element calculation show that a lot of propagating modes exist in a frequency region used for guided wave inspection, eg. 10kHz – 200kHz. Guided wave modes mainly vibrating a bottom edge of a rail were selected among the many modes in dispersion curves, and then defect detection tests were done using the selected modes. Good reflections from an artificial defect and a rail end were obtained with a vertically vibrating mode. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Pipe screening technique with guided waves has become widely applied to pipe inspection in actual industrial plants. In most cases, however, guided wave propagating in a pipe is still difficult for inspection technicians due to its complex characteristics. Authors have developed the fast calculation technique for guided wave propagation using a semi-analytical finite element method (SAFEM). This study is on development of software for guided wave propagation with the SAFE calculation. A parameter input interface was made with Visual C++, and a core execution file was coded with Fortran 90. Visualization of data set obtained by the calculation was carried out with a free visualization tool OPEN DX. Using this software including a preprocessor and a postprocessor, many kinds of guided wave simulation have become feasible even by a non-expert in guided waves. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Charge detection measurement on a double quantum dot allows bidirectional counting of single-electrons for extremely small current. We discuss higher-order moment of current noise in single-electron transport through a double quantum dot, and find that the third order moment is insensitive to the thermal noise. The counting statistics provides useful technique for studying correlated transport. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We theoretically study the ballistic transport through a quantum wire with a narrow constriction, “point contact,” in the presence of Rashba spin-orbit (SO) interaction. By numerical studies, we find that the conductance is quantized in units of 2e2/h when the constriction changes gradually in space, and that the current is spin-polarized in the transverse direction. This is due to the transition between subbands of different spins during the transport through the point contact. The spin-polarization ratio is determined by the adiabaticity of the transition, which is evaluated by the Landau-Zener theory. The spin polarization of 60% can be realized with experimentally accessible values of the SO interaction strength. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nonlinear evolutions of MHD instabilities in the large helical device are studied by means of direct numerical simulations under the vacuum configuration with the magnetic axis position R = 3.6m, including effects of its full three-dimensional geometry, flows parallel to the magnetic field lines and the fluid compressibility. The linear growth of the pressure-driven modes and their nonlinear saturations are observed. The linear growth brings about the flows parallel to the magnetic field lines as strong as the perpendicular flows. The fluid compressibility reduces the linear growth rate significantly. In the nonlinear saturation process, a qualitative difference is found in the behaviors of the parallel and perpendicular flows. The plasma appears to approach to a near-equilibrium state, keeping finite amplitudes of the parallel flow. Our numerical results highlight important roles of the parallel flow and compressibility in nonlinear MHD simulations in the large helical device. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The hysteresis of the glow discharge in VI space has been investigated by the numerical simulation. The simulation code has been formed by combination of the equation of the discharge current and the equation of the circuit. We have shown that the hysteresis is produced by the instability of the relaxation oscillation and the equilibrium state. [ABSTRACT FROM AUTHOR]

Stratified type photocatalyst with the extremely higher photocatalytic activities can be synthesized by using the chemical reaction between the Na2S solution and Cd(OH)2 precursors. This type of photocatalyst has the specific morphology which constructed by the nano-sized and capsule like formed structure, and the metal concentration was gradually changed in its wall. The “charge gradient” was formed at the metal sulfide and oxide/hydroxide junction in the wall, which favored for the separation of the photo excited electron-hole pair. Consequently, stratified type photocatalyst shows the high catalytic activity than the usual nano CdS particles. By the addition of sulfur compound into the bio reactor contained the sulfur reducing bacteria, the H2S gas concentration can increased to about 1000 times enlarge than the usual condition. Therefore, we can conclude that the enhancement of the H2S gas evolved from the bio reactor was successfully achievement, and we don't need to afraid the shortage risk of H2S supply. These H2S gas concentration can enlarged to 80% by using A type zeorite. Especially, Ca-A type zeorite is considered as the suitable material. [ABSTRACT FROM AUTHOR]

An ultra-high frequency gyrotron is being developed as a THz radiation source by using a pulsed magnet. We have achieved the highest field intensity of 20.2 T. High frequency operation at the second harmonic will achieve 1.01 THz; the corresponding cavity mode is TE6,11,1. On the other hand, an ultra-high power gyrotron with a pulsed magnet is also being developed as a millimeter to submillimeter wave radiation source. The gyrotron is a large orbit gyrotron (LOG) using an intense relativistic electron beam (IREB). A pulsed power generator “ETIGO-IV” is applied for generation of the IREB. A prototype relativistic LOG was constructed for fundamental operation. The output of the LOG will achieve 144 GHz and 9 MW; the corresponding cavity mode is TE1,4,1. Cavities for 2nd and 4th harmonic operations were designed by numerical simulation for achievement of higher frequency. The progress of development for prototype high frequency gyrotrons with pulsed magnets is presented. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

KANATA is a 1.5-m optical—near infrared telescope of Hiroshima University, which has been developed for observations of astronomical transients and variables, such as γ-ray bursts, blazars. X-ray transients, and cataclysmic variables. Here, we introduce three characteristics of KANATA with examples of observations, that is, i) high ability for prompt observations, ii) simultaneous optical and infrared observations, and iii) polarimetric observations. Collaborating with GLAST, we are planning to perform follow-up optical—infrared observations of γ-ray sources with KANATA. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]