Nucleation and initial growth processes of diamond thin films for stripper foils

Carbon ion beam stripper foils were fabricated from diamond films synthesized on silicon via chemical vapor deposition. Fine-grained polycrystal diamond foils with decent surface flatness were obtained using a nucleation enhancement pretreatment process. Freestanding diamond foils were formed by etching a portion of the silicon substrate on which the diamond films well-adhered. In preliminary lifetime evaluations, the 1–3 μm-thick diamond foils lasted between 20 and 420 min for 3.2 MeV Ne⁺ion-beam charge stripping.     

Two-dimensional scattering of a plane wave from a periodic array of dielectric cylinders with arbitrary shape

A two-dimensional scattering of a plane wave from a periodic array of dielectric cylinders with arbitrary shape using the multigrid-moment method is examined. The scattered field is expressed in terms of the integral form by an infinite summation of the surface integral over the cross section of the reference cylinder. The integral form is converted into the matrix equation by using the moment method. The integration in the elements of the matrix equation is evaluated by the lattice-sums technique to obtain a precise solution. The multigrid method is applied to the matrix equation to improve the CPU time. The CPU time and the residual norm are examined numerically for a given number of iterations and cycle indices. Then the effects of shape and material of the periodic structure on the power reflection coefficient of the fundamental Floquet mode are shown. In addition, the results indicate the effect of changing the relative permittivity of the dielectric coated body and the reflection coefficient.     

Simultaneous measurement of lens accommodation and convergence in natural and artificial 3D vision

Recent advances in 3D technology have been accompanied by increasing complaints of visual fatigue. The usual explanation for such fatigue is that accommodation and convergence are mismatched during stereoscopic vision. The aim of this study was to measure fixation distances between lens accommodation and convergence in young subjects while they viewed real objects and 3D video clips. Measurements were made using an original instrument. The 3D video clips were presented to subjects using a liquid crystal shutter glass system. The results showed that when viewing real objects, the diopter values of subjects' accommodation and convergence were similar and changed periodically. This measurement method was thus considered to be appropriate for the measurement of stereoscopic vision. We also investigated lens accommodation and convergence when subjects viewed 3D video clips. Both accommodation and convergence were found to move along with the virtual position of 3D video clips. Therefore, there was little discrepancy between accommodation and convergence during the viewing of 3D images.     

Effect of the Loosening of Wood Texture on the Mercerization of Cellulose in Wood

When wood was treated with 23% aqueous sodium hydroxide followed by washing with water and drying, no lattice conversion of cellulose was observed under the experimental conditions employed. On the other hand, wood subjected to a pretreatment that results in the loosening of its morphological texture, upon mercerization, showed a varying degree of lattice conversion. The explosion process and the TFA (trifluoroacetic acid) treatment were used to achieve the loosening of wood texture. The lattice conversion of cellulose was studied by X-ray diffractograms. The extent of lattice conversion was found to depend on the conditions of the pretreatment used to achieve the loosening of wood texture. The extent of lattice conversion increased with an increase in the explosion temperature and the time at temperature, within the range of these experiments. Increased duration of TFA pretreatment, at a particular temperature, resulted in a higher degree of lattice conversion. These observed facts have been ascribed to the extent of loosening of the morphological texture of wood, which allows comparatively free swelling of cellulose in alkali.     

Optical properties and gamma-ray response of Czochralski grown Pr:Lu3Al5O12 scintillating garnet crystals with different Pr content

Pr:LuAG single crystalline scintillators with different Pr³⁺ concentration, 0.1, 0.18, and 0.22 mol% were grown by the Czochralski method. The crystals were cut to dimensions of 2.2 × 2.2 × 15 mm³ and polished, simulating sensors for Positron Emission Tomography (PET). Their absorption coefficients were examined, and the absorption strength was found to be proportional to the Pr concentration. The α-ray induced emission spectra of the samples demonstrated two emission lines peaking at 310 and 370 nm. The emission intensities in the radio luminescence spectra were also proportional to the Pr content. The absolute light yields and intrinsic energy resolution under γ-ray irradiation were evaluated at +20, 0, and −20 °C using avalanche photodiode as a photodetector. Pr 0.22% doped crystal had strongest light output of 16 400 ph/MeV, and its intrinsic energy resolution was around few % at several hundred keV. When coupled with PMT, the decay time was around 25 ns, and it was almost independent on concentration.     

Stress biaxiality in high-burnup PWR fuel cladding under reactivity-initiated accident conditions

In order to promote a better understanding of failure mechanisms of high-burnup pressurized water reactor (PWR) fuels under reactivity-initiated accident (RIA) conditions, stress biaxiality in cladding has been estimated for the pellet-cladding (PC) mechanical interaction (PCMI) phase. The estimation was based on an analysis of the transient elongations of a pellet stack and a cladding tube measured in RIA-simulating experiments in the nuclear safety research reactor (NSRR) using the RANNS code. Stress biaxiality in the high-burnup PWR fuel cladding during the PCMI phase has been estimated to be 0.7–0.8, on average, at the mid-wall of the cladding. A comparison with fresh fuel test results and a sensitivity analysis showed that the effects of burnup and pulse width on cladding stress biaxiality are less than 10% for the investigated range. The present analysis also indicated that PC friction is strong, and that the cladding constraint on pellet stack elongation is significant irrespective of burnup. Therefore, it is recommended that strong PC friction be assumed, which is similar to the mechanical bonding condition, and that fuel pellets be treated as deformable materials in models of fuel behavior during the PCMI phase.     

Application of digital inverter-controlled AC pulsed MIG welding system to light metal joining

A digital inverter-controlled AC pulsed GMAW system has been developed for welding sheet metal structures. The arc is quite stable by extracting arc-length-related voltage through the intelligent filter. The synergic AC pulse control automatically adjusts wire feed speed to keep the setting current when the EN ratio (ratio of electronegative current integration to electrode negative plus electrode positive current integration over one pulse cycle) changes. These features make finding optimum welding conditions for gap existing joint.     

Effect of copolymerizing fluorine‐bearing monomers on the relationship among internal structure,gas permeability,and transparency in copolymer networks composed of methacrylates and siloxane macromers

To clarify the effect of the type of acrylic monomer and the molecular weight (M_n) of polydimethylsiloxane (PDMS) on the relationship among the internal structure, oxygen permeability coefficient [P(O₂)] and transparency, crosslinked copolymers were prepared with two different acrylic monomers : methyl methacrylate (MMA) and trifluoroethyl methacrylate (TFEMA). PDMS macromers with M_n of 1700, 3300, 4700, and 7800 g/mol were used. DSC measurements suggested that all constituent phases were insoluble with each other. The M_n of PDMS affected both the light transmittance and P(O₂). The relationship between the M_n and P(O₂) over the low M_n range (1700 and 3300 g/mol), and the calculated PDMS domain size ratio, were found to support the [M_n]^2/3 rule into the crosslinked copolymer. Furthermore, a 3300 g/mol M_n copolymer became transparent when the amount of PDMS was greater than PMMA. In addition, copolymerization with TFEMA drastically affected those properties, and this effect was much greater than the effect of the PDMS M_n. To clarify the mechanism of P(O₂) improvement induced by TFEMA copolymerization, calculations on the relationship among the P(O₂), PDMS volume fraction, and morphology model were performed, and some properties such as solubility parameters should play important roles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ethylene–propylene copolymer/ordered polysilsesquioxane nanocomposites prepared via organic acid‐ or base‐catalyzed binary silica water‐crosslinking reactions

In situ silica sol–gel‐derived organic–inorganic hybrid materials, which comprise a vinyltrimethoxysilane‐grafted ethylene–propylene copolymer (EPR‐g‐VTMS) and n‐hexyltrimethoxysilane (HTMS), were successfully prepared in the presence of an organic acid and base catalyst. Benzenesulfonic acid and aniline were selected as the organic acid and base catalyst, respectively, to examine the progress and effect of progressive changes in the silane water‐crosslinking reaction of EPR‐g‐VTMS/HTMS composites. The water‐crosslinked EPR‐g‐VTMS/HTMS composites were characterized by means of attenuated total reflectance Fourier transform infrared spectroscopy, gel content, solid‐state ²⁹Si cross‐polarization/magic‐angle spinning NMR, wide‐angle X‐ray scattering, tensile strength and field‐emission scanning electron microscopy measurements. These results revealed that the type of catalyst has a substantial influence on the nature of siloxane bonds and eventually the physical tensile properties of the water‐crosslinked EPR‐g‐VTMS/HTMS composites, which can be explained mainly from knowledge of the traditional acid‐ and base‐catalyzed silica sol–gel reaction. Moreover, an in‐depth analysis of the aniline‐catalyzed composites indicated the formation of ladder‐type poly(n‐hexylsilsesquioxane)s and the presence of a highly ordered structure with a thickness equal to the length of two n‐hexyl groups in all‐trans conformation. We demonstrate potential for the future design of highly ordered silicate‐based organic–inorganic hybrid nanocomposites. Copyright © 2009 Society of Chemical Industry