<Emphasis Type="Italic">In-Situ</Emphasis> Observations of Martensitic Transformation in Blast-Resistant Steel

A hybrid in-situ characterization system, which couples the laser scanning confocal microscopy (LSCM) with the time-resolved X-ray diffraction (TRXRD) measurement with synchrotron radiation, was used to characterize the microstructure evolution during heat-affected zone (HAZ) thermal cycling of high-strength and blast-resistant steel. The combined technique has a time resolution of 0.3 seconds that allows for high-fidelity measurements of transformation kinetics, lattice parameters, and morphological features. The measurements showed a significant reduction in the martensite start transformation temperature with a decrease in the prior austenite grain size. In addition, the LSCM images confirmed the concurrent refinement of martensite packet size with smaller austenite grain sizes. This is consistent with dilatometric observations. The austenite grain size also influenced the rate of transformation (df _m /dT); however, the measurements from the hybrid (surface) and dilatometric (volume) measurements were inconsistent. Challenges and future directions of adopting this technique for comprehensive tracking of microstructure evolution in steels are discussed.     

Surface texture assessment of ultra-precision machined parts based on laser speckle pattern analysis

Surface texture plays an important role in overall product specification, because the surface quality of the product is dominated by the nano-scale surface texture. This paper presents a surface texture assessment method for evaluating roughness and periodicity of surface structure with a laser speckle pattern analysis. By investigating the relation between surface texture and laser speckle pattern, characteristic parameters for describing a laser speckle pattern are proposed. The proposed characteristic parameters can evaluate the surface texture in entire observed area and in limited area in any given direction. Furthermore, the surface texture can be qualitatively assessed with a radar chart of the proposed laser speckle characteristic parameters.     

Direct Observation that Bainite can Grow Below MS

In situ simultaneous synchrotron X-ray diffraction and laser scanning confocal microscopy have confirmed that bainite in steels can grow below the martensite start temperature. This observation suggests that the formation curves for bainite in time-temperature-transformation diagrams should be extended below the martensite start temperature. Furthermore, the implication of this observation on the growth mechanism of bainitic ferrite is discussed.     

Fast Algorithm and Efficient Implementation of GMM-Based Pattern Classifiers

This paper proposes a fast decision algorithm in pattern classification based on Gaussian mixture models (GMM). Statistical pattern classification problems often meet a situation that comparison between probabilities is obvious and involve redundant computations. When GMM is adopted for the probability model, the exponential function should be evaluated. This work firstly reduces the exponential computations to simple and rough interval calculations. The exponential function is realized by scaling and multiplication with powers of two so that the decision is efficiently realized. For finer decision, a refinement process is also proposed. In order to verify the significance, experimental results on TI DM6437 EVM board and TED TB-3S-3400DSP-IMG board are shown through the application to a color extraction problem. It is verified that the classification was almost completed without any refinement process and the refinement process can proceed the residual decisions.     

Room-temperature Coulomb staircase in semiconducting InP nanowires modulated with light illumination

Detailed electron transport analysis is performed for an ensemble of conical indium phosphide nanowires bridging two hydrogenated n(+)-silicon electrodes. The current-voltage (I-V) characteristics exhibit a Coulomb staircase in the dark with a period of ～ 1 V at room temperature. The staircase is found to disappear under light illumination. This observation can be explained by assuming the presence of a tiny Coulomb island, and its existence is possible due to the large surface depletion region created within contributing nanowires. Electrons tunnel in and out of the Coulomb island, resulting in the Coulomb staircase I-V. Applying light illumination raises the electron quasi-Fermi level and the tunneling barriers are buried, causing the Coulomb staircase to disappear.     

Management of cosmic radiation exposure for aircraft crew in Japan

The International Commission on Radiological Protection has recommended that cosmic radiation exposure of crew in commercial jet aircraft be considered as occupational exposure. In Japan, the Radiation Council of the government has established a guideline that requests domestic airlines to voluntarily keep the effective dose of cosmic radiation for aircraft crew below 5 mSv y(-1). The guideline also gives some advice and policies regarding the method of cosmic radiation dosimetry, the necessity of explanation and education about this issue, a way to view and record dose data, and the necessity of medical examination for crew. The National Institute of Radiological Sciences helps the airlines to follow the guideline, particularly for the determination of aviation route doses by numerical simulation. The calculation is performed using an original, easy-to-use program package called 'JISCARD EX' coupled with a PHITS-based analytical model and a GEANT4-based particle tracing code. The new radiation weighting factors recommended in 2007 are employed for effective dose determination. The annual individual doses of aircraft crew were estimated using this program.     

Classification of fermentation performance by multivariate analysis based on mean hypothesis testing

Multivariate analysis, such as principal component analysis and artificial autoassociative neural networks, is currently extensively applied to feature capturing, physiological state recognition, fault detection and bioprocess control. However, it is not clear which process variable should be selected as an important input for multivariate analysis to analyze physiological conditions and/or bioprocess performance a priori. An efficacious method to select more informative process variables from the repository of historical data is highly desired. In this study, we focused on a premodeling step. Mean hypothesis testing (MHT) was used to select appropriate variables for multivariate analysis. Fermentation data sets were classified into two classes "good" and "bad" according to the MHT results. The results showed that selecting discriminating process variables from the historical database by MHT enhanced the overall effectiveness of multivariate analysis prior to principal component analysis and artificial autoassociative neural network model creation.     

Reduced influences of the HPHT substrates on the electronic quality of homoepitaxial CVD diamond layers and on their ultraviolet detector performance

We have carried out a detailed estimation of the influences of the high-pressure/high-temperature-synthesized (HPHT) Ib substrate on the crystalline quality of the homoepitaxial diamond and on the performance of the ultraviolet (UV) detector. The H3 center related luminescence peaks were observed even from the homoepitaxial diamond film having a thickness of 250 μm on a HPHT Ib substrate, suggesting that carriers excited in the epitaxial diamond layer can diffuse over a rather long distance to the HPHT substrate when the quality of the epitaxial layer is sufficiently high. Furthermore, we have attempted to efficiently reduce the long-distance carrier diffusion phenomenon by inserting a boron-doped layer between the epitaxial layer for the detection and the HPHT Ib substrate. The electrically-floating B-doped layer inserted between the homoepitaxial layer and the HPHT substrate efficiently reduced the long-distance carrier diffusion phenomenon, and substantially improved the performance of the UV detector fabricated on a low-quality HPHT Ib substrate.     

Anisotropic carbon nanotube papers fabricated from multiwalled carbon nanotube webs

We fabricated large-scale anisotropic carbon nanotube (CNT) paper sheets by stacking long-lasting multiwalled CNT (MWCNT) webs without using binder materials. The MWCNTs are highly aligned in the webs and they retain their alignment in the fabricated paper. Although MWCNTs are just connected by van der Waals force, tensile strength is as strong as 75.6 MPa. In addition, resistivity and thermal conductivity is as good as 2.5 × 10⁻³ Ω cm and 70 W/m K, respectively. The present high anisotropy ratios of 7.3 in resistivity and of 8.1 in thermal conductivity are due to the high alignment of the ultra-long MWCNTs which have lengths of millimeters. High-speed web drawing with a draw speed of over 10 m/s enables very rapid fabrication. The material properties of CNT structures can be measured by conventional methods for macroscopic samples rather than methods designed for nanomaterials. CNT web technology will enable CNTs to be used in new applications.     

Time domain identification for robust control

In this paper, we are concerned with a problem of robust control-oriented system identification in the time domain. Based on the well-known Schur-Takagi-AAK Theorem, we propose a linear algorithm to obtain the nominal model of the plant to be identified and the minimal bound of the uncertainty of the nominal model error which is measured by H^∞-norm. It is also shown that, in the model set defined by the nominal model and the uncertainty bound, there exists at least one model which matches the prescribed input-output data given in the time domain.