Phase transitions of antiferroelectric lead zirconate thin films in high electric field

Phase transitions in antiferroelectric lead zirconate thin films were studied at room temperature and at 77 K. The lead zirconate films were prepared on Pt coated Si substrates by a reactive magnetron co-sputtering mthod followed by a rapid thermal annealing process at 700 °C. An electric field induced antiferroelectric — ferroelectric phase transition was observed at room temperature with a maximum polarization value of 70 μC/cm². The average field required to induce the ferroelectric state and that for the reversion to the antiferroelectric state were 294 kV/cm and 179 kV/cm respectively. At 77 K a metastable ferroelectric — ferroelectric transition was observed with a maximum polarization of 58 μC/cm². These transitions were found to be coincident with those of lead zirconate single crystals.     

Phase behavior and mechanical properties of poly-p-phenylene terephthalamide/amorphous nylon molecular composites

Poly(p-phenylene terephthalamide) (PPTA)/amorphous nylon (AN) molecular composites were prepared from sulfuric acid solution by rapidly coagulating in distilled water. The regenerated films appear homogeneous and transparent. However, the rod-like and flexible macromolecules are probably entrapped in a single phase during rapid coagulation, thus thermodynamically unstable and undergoing phase segregation upon thermal treatment. The miscibility between PPTA/AN was identified by a dielectric relaxation method. Phase behavior and kinetics of phase separation in PPTA/AN mixtures were thoroughly investigated by time-resolved light scattering as well as optical microscope. A pseudo phase diagram reminiscent of a lower critical solution temperature (LCST) was established by a cloud point measurement. Several temperature-jump experiments were undertaken from ambient to a two-phase temperature region. The low PPTA content molecular composites were prepared by coagulating in a non-solvent, then by compression molding below the phase separation temperatures. The 30 wt% PPTA molecular composite exhibits over three-fold increase in tensile modulus relative to that of the neat AN, however, there is little or no improvement in the tensile strength. On the other hand, by a slight addition of AN into PPTA, the tensile and compressive failures of spun fibers may be improved.     

Hydrophilic and adhesive properties of methacrylic acid-grafted polyethylene plates

Methacrylic acid (MAA) was grafted onto polyethylene (PE) surfaces by simultaneous irradiation with UV rays in the liquid phase to estimate hydrophilic and mechanical properties for MAA-grafted PE plates. The amount of grafted MAA increased sigmoidally with UV irradiation time, and the higher grafted amount was obtained at higher monomer concentrations. With an increase in grafting of MAA, the wettabilities from the contact angles of water were enhanced and the refractive indices from the ellipsometry decreased. Though the contact angles remained constant above the grafted amount of 0.02 mmol/cm², the refractive indices approached the value of PMAA around 0.009 mmol/cm², indicating that the PE surfaces were fully covered with grafted PMAA chains. Then, at a fixed grafted amount, the grafted layer can absorb more water and the grafted PE plates possessed higher tensile shear adhesive strength, in case grafting was carried out at lower monomer concentrations. Surface properties depended on the density of carboxyl group at the surfaces of grafted layers, whereas adhesive properties depended on the structural properties of grafted chains as well as on the density of carboxyl group of the whole grafted layers.     

Measurement and analysis of induced activities in concrete irradiated using high-energy neutrons at KENS Neutron Spallation Source Facility

Precise estimation of induced activities in concrete shields for high-energy accelerator facilities is one of the most important issues that need to be solved, not only for the reduction of exposure for workers, but also for the reduction of radioactive wastes. Irradiation experiments have been performed by using the 500 MeV Neutron Spallation Source Facility in KEK. The large concrete assembly was placed in the direction of 0 degrees to the beamline. Two kinds of samples were placed at several positions in the assembly. The irradiation period was about 1 week and induced activities in the samples were measured until approximately 1.5 y after irradiation. From the comparison between the experiment and the available Monte Carlo calculation code system, good agreement was obtained for 24Na, 47Sc, 47Ca and 54Mn within a factor 2; however, large discrepancies were observed for some other nuclides.     

Chemical composition of 14C in airborne release from the Tokai reprocessing plant, Japan

Fuel reprocessing plant is one of the most important sources of anthropogenic (14)C in the environment. A method was developed to determine the amount and chemical composition of airborne (14)C release from the Tokai reprocessing plant, Japan. Effluent monitoring using this method showed most of the (14)C is released in CO(2) form and the ratio of (14)C in hydrocarbons to the total is less than 3%, not depending on the type of fuel reprocessed. This finding would provide improved understanding on dynamical behaviour of (14)C in the environment and assessment of radioecological impact from nuclear fuel cycle.     

Interaction model between elastic objects for haptic feedback considering collisions of soft tissue

The simulation of organ–organ interaction is indispensable for practical and advanced medical VR simulator such as open surgery and indirect palpation. This paper describes a method to represent real-time interaction between elastic objects for accurate force feedback in medical VR simulation. The proposed model defines boundary deformation of colliding elements based on temporary surface forces calculated by temporary deformation. The model produces accurate deformation and force feedback considering collisions of objects as well as prevents unrealistic overlap of objects. A prototype simulator of rectal palpation is constructed on general desktop PC with a haptic device, PHANToM. The system allows users to feel different stiffness of a rear elastic object located behind another elastic object. The results of experiments confirmed the method expresses organ–organ interaction in real-time and produces realistic and perceivable force feedback.     

Coherence and polarization of electromagnetic beams modulated by random phase screens and their changes on propagation in free space

The spectral degree of coherence and of polarization of some model electromagnetic beams modulated by a polarization-dependent phase-modulating device, such as a liquid-crystal spatial light modulator, acting as a random phase screen are examined on the basis of the recent theory formulated in terms of the 2 x 2 cross-spectral density matrix of the beam. The phase-modulating device is assumed to have strong polarization dependence that modulates only one of the orthogonal components of the electric vector, and the phase of the phase-modulating device is assumed to be a random function of position imitating a random phase screen and is assumed to obey Gaussian statistics with zero mean. The propagation of the modulated beam is also examined to show how the spectral degrees of coherence and of polarization of the beam change on propagation, even in free space. The results are illustrated by numerical examples.     

Web-based delivery of medical multimedia contents using an MPEG-4 system

Moving picture expert group compression standard version 4 (MPEG-4) is a standard for video coding aimed at multimedia applications. MPEG-4 was developed to enable high compression rate in a low bitrate transmission via the Internet or mobile telecommunications. Although these characteristics of MPEG-4 are suitable for telemedicine, little is known about the possibility of using this technology in the field of telemedicine. We evaluated the quality of MPEG-4-encoded medical video streams and compared them with original analogue videos and audio-video-interleave (AVI) files. Although MPEG-4 video streams have the advantage of small file size, they were found to be inferior to original videos and AVI files in terms of smoothness of motion pictures, sharpness of images and clearness of sound. Illegibility of characters was a major problem in MPEG-4 files. The score for total impression of MPEG-4 files was significantly lower than those for AVI files. The results of this study suggest that the quality of MPEG-4-encoded video streams is not adequate for telemedicine.     

Effect of non-aqueous phase liquid on biodegradation of PAHs in spilled oil on tidal flat

Biodegradation rates of polycyclic aromatic hydrocarbons (PAHs) in spilled oil stranded on tidal flats were evaluated using model reactors to clarify the effects of non-aqueous phase liquid (NAPL) on the biodegradation of PAHs in stranded oil on tidal flat with special emphasis on the relationship between dissolution rates of PAHs into water and viscosity of NAPL. Biodegradation of PAHs in NAPL was limited by the dissolution rates of PAHs into water. Biodegradation rate of chrysene was smaller than that of acenaphtene and phenanthrene due to the smaller dissolution rates. Dissolution rates of PAHs in fuel oil C were smaller than those in crude oil due to high viscosity of fuel oil C. Hence, biodegradation rates of PAHs in fuel oil C were smaller than those in crude oil. Biodegradation rates of PAHs in NAPL with slow rate of decrease like fuel oil C was slower than those in NAPL with rapid rate of decrease like crude oil. The smaller rate of decrease of fuel oil C than crude oil was due to the higher viscosity of fuel oil C. Therefore, not only the dissolution rate of PAHs but also the rates of decrease of NAPL were important factors for the biodegradation of PAHs.