Characterization of surface acoustic wave propagation in multi-layered structures using extended FEM/SDA software

This paper describes the characterization of SAW propagation in layered substrate and overlayered structures. The software based on the finite element method and spectral domain analysis was newly developed and applied to the characterization of SAW propagation under an infinitely-long Al interdigital transducer on a rotated Y-cut LiTaO₃/sapphire substrate. Because of the finite LiTaO₃ thickness, a series of spurious resonances appears. It is shown that the excitation strength of the spurious resonances changes with frequency as well as the rotation angle, which reflects the frequency and rotation angle dependence of the energy leakage. Next, the analysis was carried out for SAWs propagating in a SiO₂ layer/Al IDT/42°YX-LiTaO₃ structure. It is shown that the influence of the SiO₂ layer is significantly dependent on the location where the SiO₂ layer is deposited. In particular, it is shown that when the SiO₂ layer is deposited only on top of the electrodes, the SAW reflectivity increases compared with when the SiO₂ layer is deposited between and on top of electrodes.     

Tobit model with covariate dependent thresholds

Tobit models are extended to allow threshold values which depend on individuals’ characteristics. In such models, the parameters are subject to as many inequality constraints as the number of observations, and the maximum likelihood estimation which requires the numerical maximisation of the likelihood is often difficult to be implemented. Using a Bayesian approach, a Gibbs sampler algorithm is proposed and, further, the convergence to the posterior distribution is accelerated by introducing an additional scale transformation step. The procedure is illustrated using the simulated data, wage data and prime rate changes’ data.     

The Measurement of Structural Characteristics of Barley for Shochu Using Single‐Kernel Characterization System 4100 Crush‐Response Profiles

The selection of grain that is optimum for barley Shochu is not straightforward. Usually malting barley is used, but not all malting barley samples perform well in Shochu production. In addition there is a genotype × environment effect, so that a given variety may perform satisfactorily in one environment but not another. Therefore a method for testing samples for Shochu is required. This group has previously reported on the evaluation of barley for Shochu production using the Single Kernel Characterization System (SKCS) and demonstrated a significant correlation between the SKCS Hardness Index and pearling performance. The Hardness Index values are multivariate statistical predictions derived from an incremental change analysis of the crush‐response profiles. In the present study, a detailed analysis was performed of the averaged SKCS Crush‐Response Profiles of barley, obtained when measuring the SKCS Hardness Index. It was concluded that the morphological differences between averaged barley SKCS Crush‐Response Profiles appear to allow barley varieties to be classified into four distinct classes. In addition, the elastic response to the crushing on the SKCS device of the aleurone layers of barley kernels yields a useful predictor of pearling quality/performance.     

Free-standing,roll-able,and transparent silicone polymer film prepared by using nanoparticles as cross-linking agents

A free-standing, roll-able, and transparent silicone-based polymer film with a tensile modulus of ca. 7.8 MPa and strain at the break point of 0.76% was successfully prepared by reaction between a reactive silicone oligomer with methyl- and methoxy-side groups and hydrophilic SiO₂ nanoparticles. First, SiO₂ nanoparticles were grafted with silicone chains by a controlled wet chemical sol–gel-type reaction with the reactive oligomers. The solvent of the resulting solution was evaporated to form a viscous suspension, casted into a film, and finally heat-treated at 100 °C and 150 °C. A hydrolysis and condensation reaction among silicone-grafted SiO₂ nanoparticles and free silicone oligomers in the final heat treatment resulted to produce free-standing, roll-able, and transparent silicone-based polymer film. The fact that the silicone film cannot be synthesized without the presence of SiO₂ nanoparticles suggests that these nanoparticles act as cross-linking agents of silicone components providing the improved mechanical properties to the composite film. The rate-controlled mixing and heating of the SiO₂ aqueous/alcohol suspension and the silicone oligomer/alcohol solution was found to be the key step in the synthesis of the free-standing transparent film. While rapid addition/mixing resulted in a fragile and opaque film, a transparent material was achieved when those solutions were slowly mixed. The effect of the synthesis process on the macroscopic and microscopic properties of the prepared films is discussed along with their formation mechanism.     

Cytocompatibility and mechanical properties of novel porous 316 L stainless steel

Novel 316 L stainless steel (SS) foam with 85% porosity and an open pore diameter of 70–440 μm was developed for hard tissue application. The foam sheet with a 200-μm diameter had superior cell proliferation and penetration as identified through in vitro experiments. Calcification of human osteosarcoma cells in the SS foam was observed. Multi-layered foam preparation is a potential alternative technique that satisfies multi-functional requirements such as cell penetration and binding strength to the solid metal. In tensile tests, Young's modulus and the strength of the SS foam were 4.0 GPa and 11.2 MPa respectively, which is comparable with human cancellous bone.     

Suppression of transverse mode responses in ultra-wideband SAW resonators fabricated on a Cu-grating/15 degrees YX-linbO3 structure.

This paper discusses a technique to suppress spurious transverse mode responses appearing in ultra-wideband SAW resonators fabricated on a Cu-grating/15 degrees YX-LiNbO3 structure. The basic idea of the technique is inserting length- and width-weighted dummy electrodes between a bus-bar and interdigital electrodes. For practical device design, an analysis was made to show how the profile (field distribution) of both dominant and spurious transverse modes depends on the length and width (equivalent to SAW velocity) of the dummy electrodes. IDT-type SAW resonators were fabricated on a Cu-grating/15 degrees YX-LiNbO3 structure using the length- and width-weighted dummy electrodes. The experimental results were in good agreement with the theoretical analysis and prediction, showing that the proposed technique is effective in suppressing the spurious responses caused by the transverse modes.     

Compact central arbiters for memories with multiple read/writeports

Fast and compact central arbiter circuits for detection and regulation of access conflicts in memories with multiple ports are proposed. A layout study in 0.5 μm, 2 metal CMOS technology verifies that area-overhead and access time penalty are small up to 32 ports     

Non-equilibrium Green’s function method for modeling quantum electron transport in nano-scale devices with anisotropic multiband structure

Aggressive scaling of devices has reduced device dimensions into nanometer scale in which the single-band effective mass model is inadequate to simulate quantum transport in such devices. Thus it motivates the use of more realistic full band structures in quantum transport simulations. In this study we perform the analysis of multiband quantum transport in nanoscale devices based on a non-equilibrium Green’s function (NEGF) formalism coupled self-consistently with the Poisson equation. The empirical nearest neighbor sp ³ s ^* tight binding approximation (TBA), where the couplings among atomic orbitals of the host crystal are taken into account, is employed to obtain a realistic multiband structure. The effects of non-parabolic bandstructure as well as anisotropic features of Si are studied and analyzed. Our multiband simulation results on potential and current profiles show significant differences, especially in higher applied bias, with those of conventional effective mass model where only parabolic singleband is considered in the simulation.     

Effect of endothermic reaction associated with glass transition on the breakdown strength of biodegradable polymer films

Effects of endothermic reaction associated with glass transition on the impulse, DC, and AC breakdown strengths of poly-L-lactic acid (PLLA) and polyethylene terephthalate succinate (PETS) were studied experimentally. Impulse breakdown strength at first decreases monotonically with an increase in temperature for both PLLA and PETS. However, it increases and shows a hump when the temperature approaches a certain temperature that is slightly lower than the glass transition temperature. Then it decreases again. Moreover, it is shown that the degree of increment in impulse breakdown strength at this hump depends upon the crystallinity in PLLA. In the case of DC and AC breakdown, a similar local maximum as seen in impulse breakdown is not observed. Two possibilities, namely energy absorption and structural change both due to glass transition are discussed to explain the experimental results.     

Inflammatory bronchial polyps with a foreign body-like substance

A 68-year-old male complaining of hemosputum was admitted to our hospital. Fiberoptic bronchoscopic examinations revealed bronchial polyps and a flat foreign body-like substance in the left main bronchus. A closer inspection of a biopsied bronchial inflammatory polyp showed inflammatory edema with hypervascularization in the submucosal space and inflammatory cell infiltration. Following complete removal of this foreign body-like substance, the polyps disappeared within six weeks. It is therefore feasible to assume that the polyps appeared as a reaction to this extrinsic substance. The origin of the foreign matter is not obvious because the patient had no history of aspiration and because the histological examination did not confirm that it was a foreign body. The substance could have been formed out of the organization and calcification of some secretes in the bronchus.