Traffic characteristics of LEOS-based global personalcommunications networks

The authors present important traffic issues in a low earth orbit satellite-based global personal communications network. The article gives an overview of the characteristics of tomorrow's personal communications networks from a subscriber traffic viewpoint. Selection of multiple access scheme as well as traffic modeling in such systems is discussed, and effects of natural, unbalanced global communications traffic on the performance of the system are distinguished     

Role of adsorbed iodine into poly(vinyl alcohol) films drawn in KI/I2 solution

We have investigated the microstructure of the poly(vinyl alcohol) (PVA) films using small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) techniques. The samples were uniaxially drawn in water or KI/I₂ aqueous solution and then dried in an air-oven at 333 K for 1 h prior to SAXS and WAXS measurements. It was found that for the films drawn in KI/I₂ solution PVA chains in the microfibrillar structure are more extended upon the film drawing compared to the case of the films drawn in pure water, which is resulted from the correlation function analysis on the SAXS data. Adsorbed iodines into the film were anticipated to act as junction points between the microfibrils via the formation of the PVA-iodine complexes.     

Modified thermoelectric figure of merit estimated from enhanced mobility of [100] oriented beta-FeSi<Subscript>2</Subscript> thin film

The modification of thermoelectric figure of merit was estimated from enhanced mobility of [100] oriented beta-FeSi₂ film. beta-FeSi₂ on Si(001) substrate was prepared by molecular beam epitaxy method using an Fe source. The crystallographic orientation of beta-FeSi₂ film on Si(001) substrate was characterized by using X-ray diffraction. Using scanning electron microscopy, surface morphology and film thickness of samples were observed and estimated, respectively. The mobility of beta-FeS₂ film on Si(001) substrate were also characterized by Hall measurement at room temperature. A part of the enhancement of figure of merit was evaluated as the functions of mobility and crystallographic orientation of samples.     

Oxidation and stress relief in air at room temperature of amorphous silicon hydrogenated in a glow discharge

Glow-discharge-hydrogenated amorphous silicon (a-Si : H) was found to be oxidized in the following two ways after exposing to air at room temperature; first, thin oxide films grew uniformly on the a-Si : H, slowly with increase of exposure time; secondly, oxide with a columnar morphology grew rapidly with the increase of exposure time and the cross section of the columnar oxide was small. Mechanical stress caused by the differences of the thermal expansion coefficient and the crystallographical structure between the a-Si : H and substrates was relieved with the increase in the amount of the columnar oxide.     

Effects of low- or medium-pressure ultraviolet lamp irradiation on Microcystis aeruginosa and Anabaena variabilis

A pure culture of Microcystis aeruginosa or Anabaena variabilis, the representatives of water blooming algae, was exposed to low-pressure (LP) or medium-pressure (MP) UV lamps. Irradiated pure culture suspension was subsequently incubated for 7d under white light fluorescent lamps. During incubation, profiles of the number of cells, DNA damage and photosynthetic activity were determined. When UV fluence was 600mJ/cm(2), M. aeruginosa cell numbers decreased throughout the 7-d incubation period, to produce 1.5log reduction (LP) or 1.2log reduction (MP) compared with control. The amount of DNA damage was 2.02x10(-4) ESS/base (LP) and 3.42x10(-4) ESS/base (MP) just after UV irradiation, which became 0.05x10(-4) ESS/base and 0.23x10(-4) ESS/base, respectively, after 3d incubation. However, cell number kept decreasing, even after DNA repair. Photosynthetic activity decreased by 1.5log within 1d (LP) or 3d (MP). Thus, reduction in photosynthetic activity could contribute to the reduction in M. aeruginosa cell numbers. A. variabilis cell numbers reduced by 2.3log (LP) or 2.2log (MP) during the 7-d incubation period; however, after DNA damage repair, cell number began to increase. The amount of DNA damage was 6.07x10(-4) ESS/base (LP) and 4.48x10(-4) ESS/base (MP) just after UV irradiation, which became 0.23x10(-4) ESS/base and 0.40x10(-4) ESS/base, respectively, after 3d incubation. No reduction was observed in photosynthetic activity/cell. Therefore, DNA damage is the main contributor of the reduction in cell number of A. variabilis.     

Purification and characterization of an extracellular alpha-neoagarooligosaccharide hydrolase from Bacillus sp. MK03

An agarolytic bacterium was isolated from soil in Gifu prefecture, Japan, and identified as Bacillus sp. strain MK03. The strain secreted neoagarooligosaccharide hydroluse into the culture medium. The enzyme was purified 49.7-fold from the culture fluid by ammonium sulfate precipitation and anion-exchange and gel-filtration column chromatographic methods. The purified enzyme appeared as a single band on polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. Estimations of the molecular mass by gel filtration and SDS-PAGE gave values of 320 kDa and 42 kDa, respectively, indicating that the enzyme is octametric. The enzyme cleaved the alpha-1,3 linkage in neoagarobiose to produce 3,6-anhydro-L-galactose and D-galactose. It also selectively cleaved the alpha-1,3 linkage at the nonreducing end in neoagarotetraose or neoagarohexaose to give 3,6-anhydro-L-galactose and agarotriose or agaropentaose. The optimum temperature and pH for the enzyme were 30 degrees C and 6.1, respectively. The N-terminal amino acid sequence showed no homology to sequences of other known neoagarooligosaccharide hydrolases and agarases.     

Application of microalgae hydrolysate as a fermentation medium for microbial production of 2-pyrone 4,6-dicarboxylic acid

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Microstructure and Softening of Laser-Welded 960 MPa Grade High Strength Steel Joints

The microstructural evolution of laser-welded 960 MPa grade high strength steel joints and its effect on softening behavior of heat affected zone (HAZ) were investigated in this paper. The results show that microstructure of HAZ and fusion zone (FZ) is composed of lath martensite and bainitic ferrite. The microstructure of mixed grained zone presents strip-like characteristics and small block martensite distributes along the grain boundary. The grain size near the fusion line is about 25 μm, and the grain size in the fine grain zone is less than 5 μm. Microhardness of HAZ and FZ is lower than base metal. The soft zone locates in transitional region between tempering zone and mixed grained zone due to the interaction of the martensite tempering and the recovery and recrystallization of the rolled microstructure. Microhardness of soft zone is 310 HV and drops 18% compared to base material. Welding heat input has a remarkable effect on the width of soft zone and microhardness. The tensile properties of weld joints are closely related to the softening behavior of HAZ.     

Review of laser welding monitoring

Laser welding, as a highly efficient processing technology, has been widely applied to manufacturing industry. This paper makes an overview on real time monitoring of laser welding. It begins with a detailed introduction to six typical sensors (photodiode, visual, spectrometer, acoustical sensor, pyrometer, plasma charge sensor) in laser welding detection. Then it makes a review on multi-sensor fusion technology in both laser welding monitoring and adaptive control. Last, subjects for future research concerning welding monitoring and control have been proposed. The paper concludes that the real-time monitoring of laser welding can provide a great amount of valid information about welding status to help effectively identify weld defects and realize adaptive control.