Epitaxial integrated dE1 − dE2 silicon detectors

Epitaxial integrated dE₁ ? dE₂ silicon detectors have been developed by using the multilayer epitaxial crystal growth technique combined with the chemical preferential etching technique. These detectors are useful for eliminating events affected by channeling and blocking effects in the identification of heavy ions using multiple detector telescope systems. Characteristics of dE detectors of the integrated dE₁ ? dE₂ type are confirmed to as good as those of integrated E ? dE detectors.     

3-D device modeling for SRAM soft-error immunity and tolerance analysis

Soft-error tolerance of static random-access memory (SRAM) devices has been predicted by using three-dimensional (3-D) and time-dependent device simulation in conjunction with circuit simulation. An inverter model developed for 3-D device simulation is described, along with the analysis of the inverters device response as a function of time. The output thus obtained was applied as an input voltage source in circuit simulation of unit SRAM cell and the stability of this bistable circuit is studied on that basis. The effects on soft-error immunity of changes in alpha-particle injection conditions and in load resistance and capacitance are described. The validity of the presented model is examined through comparison of the bit-error-rate dependence on incident angle of alpha particles to that of measured rates. To simulate the angular dependence, we introduce statistical distribution models for alpha-particle energy, position of incidence on the device surface, and angle of incident. Results of device/circuit simulation carried out with many sets of energy, position, and angle are presented. Reasonable agreement between results of simulation and experimental data without the use of adjustment parameters is demonstrated. A map of soft-error tolerance on the CR plane with critical charge Q/sub c/ as a parameter is presented and its derivation explained. An analytic expression for the tolerance is clarified by proposing an equivalent circuit model for the simulation of alpha-particle injection at the output node in an inverter circuit. Inverter modeling is shown to be essential to obtaining SRAM soft-error tolerance to high degrees of accuracy.     

Finite element analysis of fracture statistics of ceramics: Effects of grain size and pore size distributions

A novel numerical simulation method based on finite element analysis (FEA), which can evaluate the fracture probability caused by the characteristics of flaw distribution, is considered an effective tool to facilitate and increase the use of ceramics in components and members. In this study, we propose an FEA methodology to predict the scatter of ceramic strength. Specifically, the data on the microstructure distribution (i.e., relative density, size and aspect ratio of pore, and grain size) are taken as the input values and reflected onto the parameters of a continuum damage model via a fracture mechanical model based on the circumferential circular crack emanating from an oval spherical pore. In addition, we numerically create a Weibull distribution based on multiple FEA results of a three‐point bending test. Its validity is confirmed by a quantitative comparison with the actual test results. The results suggest that the proposed FEA methodology can be applied to the analysis of the fracture probability of ceramics.     

Stratified Markov Chain Monte Carlo Light Transport

Markov chain Monte Carlo (MCMC) sampling is a powerful approach to generate samples from an arbitrary distribution. The application to light transport simulation allows us to efficiently handle complex light transport such as highly occluded scenes. Since light transport paths in MCMC methods are sampled according to the path contributions over the sampling domain covering the whole image, bright pixels receive more samples than dark pixels to represent differences in the brightness. This variation in the number of samples per pixel is a fundamental property of MCMC methods. This property often leads to uneven convergence over the image, which is a notorious and fundamental issue of any MCMC method to date. We present a novel stratification method of MCMC light transport methods. Our stratification method, for the first time, breaks the fundamental limitation that the number of samples per pixel is uncontrollable. Our method guarantees that every pixel receives a specified number of samples by running a single Markov chain per pixel. We rely on the fact that different MCMC processes should converge to the same result when the sampling domain and the integrand are the same. We thus subdivide an image into multiple overlapping tiles associated with each pixel, run an independent MCMC process in each of them, and then align all of the tiles such that overlapping regions match. This can be formulated as an optimization problem similar to the reconstruction step for gradient-domain rendering. Further, our method can exploit the coherency of integrands among neighboring pixels via coherent Markov chains and replica exchange. Images rendered with our method exhibit much more predictable convergence compared to existing MCMC methods.     

A Survey on Gradient‐Domain Rendering

Monte Carlo methods for physically‐based light transport simulation are broadly adopted in the feature film production, animation and visual effects industries. These methods, however, often result in noisy images and have slow convergence. As such, improving the convergence of Monte Carlo rendering remains an important open problem. Gradient‐domain light transport is a recent family of techniques that can accelerate Monte Carlo rendering by up to an order of magnitude, leveraging a gradient‐based estimation and a reformulation of the rendering problem as an image reconstruction. This state of the art report comprehensively frames the fundamentals of gradient‐domain rendering, as well as the pragmatic details behind practical gradient‐domain uniand bidirectional path tracing and photon density estimation algorithms. Moreover, we discuss the various image reconstruction schemes that are crucial to accurate and stable gradient‐domain rendering. Finally, we benchmark various gradient‐domain techniques against the state‐of‐the‐art in denoising methods before discussing open problems.     

Doubly oriented β-form films of poly(vinylidene fluoride)

PVDF sheets, rapidly quenched, were (1) two-step transversely stretched at various temperatures and (2) stretched at various temperatures, rolled at room temperature and then annealed. The orientation patterns of the β-form crystal (which contains the polar b-axis) in these films were analysed on the basis of X-ray diffraction photographs taken with flat and cylindrical cameras. In the case of (1), when both of the two-step transversely stretching temperatures were below 100°C, a doubly oriented film with the plar b-axis oriented parallel to the film surface was obtained. In the case of (2), when the stretching temperature was below 100°C, the sheets then rolled without annealing, another doubly oriented film with the polar b-axis preferentially oriented at 30° to the film surface was obtained. On the other hand, when these films were annealed above 100°C, or the stretching temperatures were above 100°C, orientation patterns in which the polar b-axis was partially rotated through 60° were obtained. The orientation mechanisms of these films are discussed using the measurements of the lattice spacings of the β-form crystal.     

Oxidation of toluene to benzoic acid over modified V2O5-TiO2 catalyst with SeO2, TeO2 and Sb2O3

It was found that the addition of SeO₂, TeO₂ or Sb₂O₃ to a V₂O₅/TiO₂ catalyst greatly improved the catalytic activity in the vapor phase oxidation of toluene to selectively form benzoic acid.     

Phase Separation in 12 mol% Ceria-Doped Zirconia Induced by Heat Treatment in H2 and Ar

The phase separation in 12 mol% CeO₂─ZrO₂ ceramic heattreated in a mixture of H₂ and Ar was investigated by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, and Raman scattering. After heat treatment at temperatures above 1200°C, the tetragonal solid-solution phase separated into Zr₂Ce₂O₇ and the monoclinic phase. Raman scattering measurements also provided supplementary evidence for the phase separation. XPS showed that the valence change from Ce⁴⁺ to Ce³⁺ predominantly occurred, whereas the reduction from Zr⁴⁺ to Zr³⁺ took place above 1200°C. It is concluded, that in the highly reduced sample, where the valence changes from Ce⁴⁺ (Zr⁴⁺) to Ce³⁺ (Zr³⁺), the phase separation is noticeably promoted. Below 1000°C the phase separation was suppressed because of no appreciable valence change to trigger the phase separation, and the single tetragonal phase was retained.