Impact of time-dependant thermal expansion coefficient on the early-age volume changes in cement pastes

Volume changes and time-dependent thermal expansion coefficient were determined at early stages and the measured total strain was separated into thermal strain and autogenous strain. Cement paste specimens were subjected to temperature histories that imitated hydration-induced temperature rise of the mass concrete. It was shown that the thermal expansion coefficient increased significantly with the development of hydration and became more conspicuous when the ground granulated blast furnace slag was added. The time-dependant increase of thermal expansion coefficient, due to self-desiccation, could result in considerable shrinkage strain at the end of the temperature history. The impact of the time-dependant increase of thermal expansion coefficient might be taken into account as one of the necessary factors in the crack control design from now and cannot even be neglected within the range of the water to binder ratio of this study, because the shrinkage originated in that effect sometimes exceed the autogenous shrinkage.     

Artificial Intelligence-based determination of fracture toughness and bending strength of silicon nitride ceramics

Two mechanical properties, fracture toughness (K_IC) and bending strength (σ), of silicon nitride (Si₃N₄) ceramics were determined from their microstructural images via convolutional neural network (CNN) models. The Si₃N₄ samples used for database were fabricated using various kinds of sintering additives under different process conditions. In total, 330 data sets were prepared and used for building the CNN models for artificial intelligence-bassed determination of the two mechanical properties and testing the determination accuracy of the trained models. The determination coefficients (R²), which were used as accuracy indices, were approximately 0.85 for K_IC and 0.92 for σ. Although both the R² values were relatively high, the lower value for K_IC suggests that it is influenced more by what is little obtained from the microstructural information, such as grain-boundary characteristics. Furthermore, gradient-weighted class activation mapping, which can visualize which parts of the image the CNN models focus on, showed that the trained models determined the two mechanical properties based on correct recognition of the microstructural difference among the images.     

Toward stabilized 10% efficiency of large-area (>5000 cm) a-Si/a-SiGe tandem solar cells using high-rate deposition

This paper reviews recent progress in large-area a-Si/a-SiGe tandem solar cells at Sanyo. Optimized hydrogen dilution conditions for high-rate deposition of hydrogenated amorphous silicon (a-Si:H) films and thinner i-layer structures have been systematically investigated for improving both the stabilized efficiency and the process throughput. As a result, a high photosensitivity of 10⁶ for a-Si:H films has been maintained up to the deposition rate of 15 Å/s. Furthermore, the world's highest initial conversion efficiency of 11.2% which corresponds to a stabilized efficiency of about 10% has been achieved for a 8252 cm² a-Si/a-SiGe tandem solar cell by combining the optimized hydrogen dilution and other successful technologies.     

Theoretical approach of a flat-plate solar collector taking into account the absorption and emission within glass cover layer

A rigorous theoretical approach of a flat-plate solar collector with a black absorber considering the glass cover as an absorbing–emitting media is presented. The glass material is analyzed as a non-gray plane-parallel medium subjected to solar and thermal irradiations in one-dimensional case using the Radiation Element Method by Ray Emission Model (REM²). The optical constants of a clear glass window proposed by Rubin have been used. These optical constants, 160 values of real part n and imaginary part k of the complex refractive index of a clear glass, cover the range of interest for calculating the solar and thermal radiative transfer through the glass cover. The computational time for predicting the thermal behavior of solar collector was found to be prohibitively long for the non-gray calculation using 160 values of n and k. Therefore a suitable semi-gray model is proposed for rapid calculation. The profile of the efficiency curve obtained in the present study was found to be not linear in shape. Indeed, the heat loss from the collector is a combination of convection and radiation and highly non linear. The effect of the outside convective heat transfer on the efficiency curve is also studied. In fact, when the convection is the dominant heat transfer mode compared with the radiation one, the profile of the efficiency curve is more or less straight line. Consequently, the heat loss coefficient could be calculated using Klein model. It has been also shown that the effect of the wind speed on the glass cover mean temperature is very important. This effect increases with the increase of the mean absorber temperature.     

Real-time PCB monitoring using time-of-flight mass spectrometry with picosecond laser ionization

The study demonstrates the applicability of laser ionization time-of-flight mass spectrometry for real-time measurement of polychlorinated biphenyls (PCBs). Picosecond 266-nm laser light ionization reduced fragmentation and provided very high PCB detection sensitivity. This high sensitivity has advantages in terms of real-time monitoring capability as compared to the conventional GC-ECD or GC-MS methods, which require at least several days for the analysis of PCBs. Detection sensitivity of under 0.01 mg/Nm3 was achieved with a 1-min measuring time; this sensitivity is superior to the exhaust gas control guideline of 0.15 mg/Nm3 by a factor of 10. A prototype PCB monitoring device has been developed and tested in a pilot PCB treatment plant. The 1-min detection time represents a substantial advance in the monitoring of exhaust gas and the workplace atmosphere in accordance with safety regulations.     

Double-walled boron nitride nanotubes grown by floating catalyst chemical vapor deposition

One-dimensional nanostructures exhibit quantum confinement which leads to unique electronic properties, making them attractive as the active elements for nanoscale electronic devices. Boron nitride nanotubes are of particular interest since, unlike carbon nanotubes, all chiralities are semiconducting. Here, we report a synthesis based on the use of low pressures of the molecular precursor borazine in conjunction with a floating nickelocene catalyst that resulted in the formation of double-walled boron nitride nanotubes. As has been shown for carbon nanotube production, the floating catalyst chemical vapor deposition method has the potential for creating high quality boron nitride nanostructures with high production volumes.     

Development of Microstructures of Long-Period Stacking Ordered Structures in Mg85Y9Zn6 Alloys Annealed at 673 K (400 °C) Examined by Small-Angle X-Ray Scattering

Development of LPSO structure and in-plane ordering during annealing the Mg85Y9Zn ternary alloy sample at 673 K (400 °C) was examined by synchrotron radiation small-angle scattering/diffraction measurements. By examining the first diffraction peaks for 18R, 10H, and in-plane order spot, the growth kinetics of in-plane order domain and the transition from 10H into 18R were discussed. The domain growth of in-plane order was characterized by small domain with little correlation between neighboring segregation layers.     

Transport of organic acids through a supported liquid membrane driven by lipase-catalyzed reactions

We have developed a lipase-facilitated supported liquid membrane. Lipase-catalyzed reactions were coupled with a supported liquid membrane (SLM) to transport organic acids through the SLM. We succeeded in the rational transport of organic acids through the SLM using lipase-catalyzed reactions and observed that there were differences in the transport behavior of various organic acids due to the substrate specificity of lipase. Subsequently, various parameters, such as the alcohol concentration in the feed phase, the pH in each aqueous phase, an organic solvent in the SLM, and the kind of lipase, were investigated. We found that the optimum conditions were 65 vol% alcohol concentration, pH 6.3 in each aqueous phase, isooctane as the liquid membrane phase and Candida rugosa lipase as the esterification biocatalyst.     

Effects of engineered methionine in the 8Sα globulin of mungbean on its physicochemical and functional properties and potential nutritional quality

The major storage protein of mungbean, 8Sα globulin or vicilin, was engineered using site-directed mutagenesis to increase the number of methionine (Met) residues in the molecule for improvement of functional and nutritional qualities. Eight Met-rich proteins were designed and prepared to have 2 to 10 Met residues introduced in disordered regions II and IV. The designed proteins were highly expressed as soluble form in Escherichia coli. Their production level of the modified proteins was estimated to be about 30%, and was almost the same as that of 8Sα globulin wild type (WT). The modified proteins formed stable native conformation similar to WT as shown by gel filtration chromatography. They demonstrated greater stability in terms of thermal denaturation temperature and greater emulsifying ability and emulsion stability, especially the 10-Met protein, compared to the wild type. Met-rich proteins with 3, 5, and 10 Met residues had 74, 96, and 145% of nutritional requirement for Met compared with 41% for WT. Based on allergenicity prediction programs, WT and all the modified proteins had no allergenic potential.     

Speciation of sulfate in size-fractionated aerosol particles using sulfur K-edge X-ray absorption near-edge structure

X-ray absorption near-edge structure (XANES) at sulfur K-edge was used to determine the sulfate species present in size-fractionated aerosol particles based on the postedge structure after the main absorption peak in the XANES region. A comparison of the XANES spectra of reference sulfate materials and aerosol samples collected in Tsukuba in Japan clearly showed that (NH4)2SO4 was the main sulfur species in particles with a smaller diameter and CaSO4 x 2H2O (gypsum) was the main sulfur species in particles with a larger diameter. A simulation of the XANES spectra by reference materials allows us to obtain the quantitative mixing ratios of the different sulfate species present in the aerosol samples. The presence of minor sulfur species other than (NH4)2SO4 and gypsum at the surface of mineral aerosols is suggested in our simulations and by a surface-sensitive conversion electron/He-ion yield XANES. In the absence of a contribution from a large dust event, the mole concentration of gypsum in the mineral aerosol fraction (particle diameter > 1 microm) determined by XANES is similar to that of Ca which is determined independently using ion chromatography. This shows that the Ca and sulfate in the mineral aerosols are present only as gypsum. Considering that calcite is the main Ca mineral in the original material arising from an arid and semiarid area in China, it is strongly suggested that gypsum is formed in aerosol during its long-range transportation by a reaction between calcite and sulfate ions.