Development of an engineering model for ferromagnetic shape memory alloys

This paper presents a relationship among stress, temperature and magnetic properties of a ferromagnetic shape memory alloy. In order to derive an engineering model of ferromagnetic shape memory alloys, we have developed a measuring system of the relationship among stress, temperature and magnetic properties. The samples used in this measurement are Fe68–Ni10–Cr9–Mn7–Si6 wt% ferromagnetic shape memory alloy. They are thin ribbons made by rapid cooling in air. In the measurement, the ribbon sample is inserted into a sample holder winding consisting of the B-coil and compensation coils, and magnetized in an open solenoid coil. The ribbon is stressed with attachment weights and heated with a heating wire. The specific susceptibility was increased by applying tension, and slightly increased by heating below the Curie temperature.     

Pyrolysis of amines: Infrared spectrum of methyleneimine

Methyleneimine was detected in the gas phase by a moderately high resolution infrared spectrometer as one of the intermediate species produced by a pyrolysis of amines. Observed vibrational frequencies of some isotopic derivatives have been combined with the ab initio values to reach a most reliable force constants set. Some other spectroscopic parameters, involving geometrical parameters and dipole moment derivatives, have also been calculated ab initio and compared with the observation. Its half-life in our experimental apparatus was about 10 min, which is much longer than the previously reported values, 0.1 or 10 sec.     

Raman spectroscopy of SWNTs produced by a XeCl excimer laser ablation at high temperatures

Synthesis of single-wall carbon nanotubes (SWNTs) was carried out by an ablation method using a XeCl excimer laser. It was irradiated onto a graphite target containing Co and Ni at the temperatures of 1073, 1173, 1273, 1373, 1473, 1523 and 1623 K under the atmosphere (0.1 MPa) of Ar gas with the flow rate of 12 ml/min. The measurement by a scanning/transmission electron microscope and Raman spectroscopy found the formation of SWNTs with the diameter of about 1.3 nm and the length of about 2 μm in ablated carbonaceous soot. The ratio of peak intensity of 1590 cm⁻¹ (G band) to that of 1335 cm⁻¹ (D band) in the high frequency Raman spectra increased with increasing the ambient temperature. The radial breathing mode (RBM) in the low frequency Raman spectra shows that the mean diameter of SWNTs increased with increasing the ambient temperature.     

Echo-intensity compensation in echolocating bats (Pipistrellus abramus) during flight measured by a telemetry microphone

An onboard microphone (Telemike) was developed to examine changes in the basic characteristics of echolocation sounds of small frequency-modulated echolocating bats, Pipistrellus abramus. Using a dual high-speed video camera system, spatiotemporal observations of echolocation characteristics were conducted on bats during a landing flight task in the laboratory. The Telemike allowed us to observe emitted pulses and returning echoes to which the flying bats listened during flight, and the acoustic parameters could be precisely measured without traditional problems such as the directional properties of the recording microphone and the emitted pulse, or traveling loss of the sound in the air. Pulse intensity in bats intending to land exhibited a marked decrease by 30 dB within 2 m of the target wall, and the reduction rate was approximately 6.5 dB per halving of distance. The intensity of echoes returning from the target wall indicated a nearly constant intensity (-42.6 +/- 5.5 dB weaker than the pulse emitted in search phase) within a target distance of 2 m. These findings provide direct evidence that bats adjust pulse intensity to compensate for changes in echo intensity to maintain a constant intensity of the echo returned from the approaching target at an optimal range.     

Eu-Doped KCl storage phosphor for erasable and rewritable optical memory utilizing photostimulated luminescence phenomenon

Intense photostimulated luminescence (PSL) with a peak at 420 nm is observed in ultraviolet (UV) Iight-irradiated europium-doped potassium chloride (KCl: Eu) crystalline phosphors. The PSL characteristics of UV-irradiated KCl: Eu phosphor for optical memory application were studied. The excitation and emission mechanisms of the 420 nm PSL, which are consistent with the results obtained, are discussed.     

Experimental investigation on reversal of secondary Bjerknes force between two bubbles in ultrasonic standing wave

The direction of the secondary Bjerknes force between a free bubble and an attached bubble was experimentally investigated. The behavior of the two bubbles in an ultrasonic standing wave of 27 kHz was observed using an imaging system with a high-speed video camera. It was demonstrated experimentally that the direction of the force reversed at a specific separation distance between the two bubbles, which was defined as the threshold distance. The threshold distance changed with the radius of the attached bubble. In addition, a theoretical calculation was performed using a previously derived model that coupled the vibrations of two free bubbles [Ida, Phys. Lett. A 297, 210-217 (2002)]. The experiment data for the threshold distance qualitatively agreed with the theoretical predictions, except when the separation distance was very small. Then, it was discovered that the free bubble became trapped near the attached bubble when the separation distance between the two bubbles was very small. This indicated that a stable equilibrium point for the separation distance exists that cannot be predicted by the theoretical model.     

Heavy Quark Potential and Quarkonium Spectrum in Nonperturbative pNRQCD

The charmonium and bottomonium mass spectra are investigated systematically in potential nonrelativistic QCD with the heavy quark potential computed by lattice QCD simulations nonperturbatively. The potential consists of a static potential and relativistic corrections classified in powers of the inverse of heavy quark mass m, and the effects of the O(1/m) correction, the O(1/m ²) spin–orbit and spin–tensor corrections on the mass spectra are examined systematically. The pattern of the mass spectra is found to be in fairly good agreement with the experimental data, in which the O(1/m) correction gives an important contribution.     

Hyperfine structure of the electron spin resonance of phosphorus-doped Si nanocrystals

Electronic states of P donors in Si nanocrystals (nc-Si) embedded in insulating glass matrices have been studied by electron spin resonance. Doping of P donors into nc-Si was demonstrated by the observation of optical absorption in the infrared region due to intraconduction band transitions. P hyperfine structure (hfs) was successfully observed at low temperatures. The observed splitting of the hfs was found to be much larger than that of the bulk Si:P and depended strongly on the size of nc-Si. The observed strong size dependence indicates that the enhancement of the hyperfine splitting is caused by the quantum confinement of P donors in nc-Si.     

Polarization Sensitive Spectral Interferometric Optical Coherence Tomography for Biological Samples

A spectral interferometric optical coherence tomography (OCT) system which has polarization sensitivity is developed. This system reduces the mechanical scanning dimension by employing the principle of spectral interferometry, and measures a two dimensional cross-sectional image of biological tissue with one dimensional mechanical scanning. Sixteen OCT images with different polarization conditions are measured, and two dimensional distributions of each element of the Müller matrix of a sample to be measured are calculated.     

Combustion behaviors of isolated n-decane and ethanol droplets in carbon dioxide-rich ambience under microgravity

The burning and sooting behaviors of isolated fuel droplets for ethanol and n-decane are examined in high concentration of the ambient carbon dioxide under microgravity. A quartz fiber with the diameter of 50 μm maintains the droplet in the center of the combustion chamber and the range in the initial droplet diameter is from 0.30 to 0.80 mm. The ambience consists of oxygen, nitrogen and carbon dioxide. The concentration of oxygen is 21% in volume, and that of carbon dioxide is varied from 0% to 60% in volume. Detail measurements of the projected image of the droplet are conducted by using a high speed video camera and the effective droplet diameter squared are calculated from the surface area of the rotating body of the projected object. From evolutions of the droplet diameter squared, the instantaneous burning rates are calculated. Time history of the instantaneous burning rate clearly represents the droplet combustion events, such as the initial thermal expansion, ignition and following combustion. The instantaneous burning rate for n-decane shows an increasing trend during combustion, while that for non-sooting ethanol remains almost constant or shows a decreasing trend. A slight stepwise increase in the instantaneous burning rate is observed for larger n-decane droplets in air, which may be attributed to soot accumulation. However, this behavior of the burning rate disappears in higher concentration of carbon dioxide. Direct observation of the droplet flame indicates suppression of soot production in higher concentration of carbon dioxide and the suppression is enhanced for smaller droplet.