On the three-dimensional structure of WC grains in cemented carbides

In the present work, the size distribution and shape of WC grains in cemented carbides (WC–Co), with different Co contents, have been investigated in three dimensions. Direct three-dimensional (3-D) measurements, using focused ion beam serial sectioning and electron backscattered diffraction (EBSD), were performed and a 3-D microstructure was reconstructed. These measurements were supplemented by two-dimensional (2-D) EBSD and scanning electron microscopy on extracted WC grains. The data from 2-D EBSD collected on planar sections were transformed to three dimensions using a recently developed statistical method based on an iterative inverse Saltykov procedure. This stereological analysis revealed that the assumed spherical shape of WC grains during the Saltykov method is reasonable and the estimated 3-D size distribution is qualitatively in good agreement with the actual distribution measured from 3-D EBSD. Although the spherical assumption is generally fair, the WC grains have both faceted and rounded surfaces. This is a consequence of the relatively low amount of liquid phase during sintering, which makes impingements significant. Furthermore, the observed terraced surface structure of some WC grains suggests that 2-D nucleation is the chief coarsening mechanism to consider.     

High flux mesoporous MCM-48 membranes: Effects of support and synthesis conditions on membrane permeance and quality

This communication reports experimental efforts to synthesize defect-free mesoporous MCM-48 membranes with improved gas flux. We demonstrate a facile and inexpensive method of synthesizing defect-free supported MCM-48 membranes with improved N₂ and CO₂ permeance (>2 × 10⁻⁷ mol/m² s Pa) employing asymmetric supports for the membrane synthesis which contain layers of macropores possessing different pore sizes. The membranes prepared on asymmetric -alumina supports displayed higher gas permeance than those fabricated on symmetric supports (N₂ permeance <10⁻⁷ mol/m² s Pa) as confirmed by unsteady-state gas permeation experiments. Further improvement in gas permeance was achieved by covering one face and the sides of the support with a ceramic tape during membrane synthesis.     

Some properties of boronized layers on steels with direct diode laser

Boronized layer on steel is known to be formed by thermal diffusion of boron into the surface of steel improving corrosion-erosion resistant properties. Boronizing is carried out at temperatures ranging from 800 °C to 1050 °C and takes from one to several hours. There is one problem in this process, however, that the structure and properties of the base material are influenced considerably by the high temperature and long time of treatment. In order to avoid the aforementioned drawbacks of pack boronizing and laser-assisted boronizing, a better way is to activate the pack boronizing media and the workpiece with a high density power. The laser boronizing processes do not change the properties of the base material. In this study, the effect of laser characteristics was examined on the laser boronizing of carbon steel. After laser boronizing, the microstructure of the boride layer was analysed with an optical microscope and X-ray diffractometer (XRD). The mechanical properties of borided layer are evaluated using Vickers hardness tester and sand erosion tester. Results showed that the boride layer was composed of FeB and Fe₂B with thickness ranging 200-300 μm. The laser boronizing process did not change the properties of the base material.     

关于龙安寺方丈庭园造园意图的考察

"龙安寺方丈庭园"是日本具有代表性的庭园,但其建造时期、建造者、建造意图都未有定论。本文认为此园是对中国五台山的描绘。自古以来五台山的文殊菩萨信仰非常兴盛,从8世纪开始有多位来自日本的高僧到访过五台山,并将佛像、绘画等带回了日本。以此为依据在13世纪绘制而成的"五台山文殊菩萨骑狮像",中央石峰的形态与"龙安寺方丈庭园"中央置石组群造型相同,可以推断"五台山文殊菩萨骑狮像"中的石峰是其描摹的原型。     

Aging-induced changes in microstructure and water distribution in fresh and cooked pork in relation to water-holding capacity and cooking loss - A combined confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance relaxation study

Confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance (LF-NMR) relaxometry were combined to characterize microstructural changes and water distribution in fresh and cooked pork during an aging period of 14 days. At day 1 (24 h postmortem) a few muscle fibres, which appear swollen, were observed in both fresh and cooked meat. An identical microstructure was still apparent after 14 days, however, the number of muscle fibres showing distinguished characteristics was found to increase throughout the aging period. Hence, it was apparent that during aging the individual fibres swell and disintegrate at different rates. Development in water-holding capacity (WHC) was followed during the aging period using gravimetric methods, and an increase in the WHC in the fresh meat was observed, which resembled the amount of extramyofibrillar water measured by NMR relaxometry (T₂₂ population). This was consistent with the CLSM images, as a substantial increase in the number of myofibrils that appeared swollen, capable of holding more water, was observed during aging. In the cooked meat the width of the T_21c population, reflecting the myofibrillar water in the cooked meat, was seen to decrease during the entire storage period, which corresponds to the development of a more homogeneous structure. In the CLSM data a continuous degradation during the storage period was observed, which could resemble a shift to a more homogeneous structure. Comparison of CLSM of transverse sections of fresh and cooked pork revealed a pronounced shrinkage of muscle fibres upon cooking. This resulted in large gaps between the cooked muscle fibres, which also was visible as shrinkage at the level of the individual myofibrils. This pattern was also reflected in the NMR relaxation data. The cooking-induced shrinkage of the myofibrils occurred concomitantly with a decrease in the amount of intermyofibrillar water within the individual fibre and an increase in the larger extramyofibrillar spaces between fibres, i.e. water is expelled from the myofibrillar matrix upon cooking. Accordingly, the present study demonstrated that the use of CLSM together with NMR relaxometry can provide further information on the relationship between structural characteristics of meat and resultant water distribution.     

Acceleration of nonylphenol and 4-tert-octylphenol degradation in sediment by Phragmites australis and associated rhizosphere bacteria

We investigated biodegradation of technical nonylphenol (tNP) in Phragmites australis rhizosphere sediment by conducting degradation experiments using sediments spiked with tNP. Accelerated tNP removal was observed in P. australis rhizosphere sediment, whereas tNP persisted in unvegetated sediment without plants and in autoclaved sediment with sterile plants, suggesting that the accelerated tNP removal resulted largely from tNP biodegradation by rhizosphere bacteria. Three bacterial strains, Stenotrophomonas sp. strain IT-1 and Sphingobium spp. strains IT-4 and IT-5, isolated from the rhizosphere were capable of utilizing tNP and 4-tert-octylphenol as a sole carbon source via type II ipso-substitution. Oxygen from P. australis roots, by creating highly oxygenated conditions in the sediment, stimulated cell growth and the tNP-degrading activity of the three strains. Moreover, organic compounds from P. australis roots functioned as carbon and energy sources for two strains, IT-4 and IT-5, supporting cell growth and tNP-degrading activity. Thus, P. australis roots elevated the cell growth and tNP-degrading activity of the three bacterial strains, leading to accelerated tNP removal. These results demonstrate that rhizoremediation of tNP-contaminated sediments using P. australis can be an effective strategy.     

Effect of an Nb2O5 nanolayer coating on ZnO electrodes in dye-sensitized solar cells

Nanostructured porous zinc oxide electrodes for use in dye-sensitized solar cells (DSSCs) were coated with thin niobium oxide layers by using sol–gel transformation of niobium pentaethoxide in air. Coating solutions were prepared by mixing niobium pentaethoxide and ethanol. A dip-coating technique was adopted at a low withdrawal speed of 100 μm s⁻¹. The coated electrodes were then heat-treated at temperatures between 400 and 600 °C. The presence of niobium in the coated electrodes was confirmed by X-ray photoelectron spectroscopy. As expected, the niobium oxide layers worked as an energy barrier between the ZnO electrode and electrolyte. Open-circuit voltage (V_OC) of the cells using the coated electrodes was then enhanced up to 0.768 V, which was attributable to the suppression of the recombination of photogenerated electrons with oxidized species in electrolytes. An additional benefit of the coating was that grain growth of ZnO particles in the electrodes was hindered and short-circuit photocurrent density (J_SC) was kept relatively high due to large amounts of adsorbed dye. An overall light-to-electricity conversion efficiency was increased to a maximum of 5.19%, indicating that the proper coating technique was the key for improving the performance of ZnO-based DSSCs.     

Disparities of indoor temperature in winter: A cross-sectional analysis of the Nationwide Smart Wellness Housing Survey in Japan

The WHO Housing and health guidelines recommend a minimum indoor temperature of 18°C to prevent cold-related diseases. In Japan, indoor temperatures appear lower than in Euro-American countries because of low insulation standards and use of partial intermittent heating. This study investigated the actual status of indoor temperatures in Japan and the common characteristics of residents who live in cold homes. We conducted a nationwide real-world survey on indoor temperature for 2 weeks in winter. Cross-sectional analyses involving 2190 houses showed that average living room, changing room, and bedroom temperatures were 16.8°C, 13.0°C, and 12.8°C, respectively. Comparison of average living room temperature between prefectures revealed a maximum difference of 6.7°C (Hokkaido: 19.8°C, Kagawa: 13.1°C). Compared to the high-income group, the odds ratio for living room temperature falling below 18°C was 1.38 (95% CI: 1.04-1.84) and 2.07 (95% CI: 1.28-3.33) for the middle- and low-income groups. The odds ratio was 1.96 (95% CI: 1.19-3.22) for single-person households, compared to households living with housemates. Furthermore, lower room temperature was correlated with local heating device use and a larger amount of clothes. These results will be useful in the development of prevention strategies for residents who live in cold homes.     

Emulsion copolymerization of vinyl acetate-ethylene in high pressure reactor-characterization by inline FTIR spectroscopy

The objective of this research was to investigate the effect of temperature, pressure, initiator concentration and agitation rate, in ethylene-vinyl acetate emulsion copolymerization, on copolymer composition. The inline React-IR ATR system was used to monitor the reaction as well as to determine residual free vinyl acetate. Pressure, temperature and agitation rate have great influence on mass transfer of ethylene monomer to the reaction sites. The vinyl acetate was introduced in semi-batch mode as well as ethylene since the copolymerization was carried out under a constant pressure of ethylene. The higher temperature results in lower content of ethylene incorporated in copolymer. Increase of pressure has a direct effect on the ethylene content in the copolymers through increasing solubilization of ethylene monomer which in turn increases ethylene content in the copolymers. Copolymers of up to 15 wt.% of ethylene content have been synthesized at an ethylene pressure of 30 bar and a temperature of 75 °C. Analytical methods, such as differential scanning calorimetry, nuclear magnetic resonance, thermogravimetric analysis, and infrared spectroscopy were used for characterization of copolymers.