Microstructural analysis of the stir zone of Al alloy produced by friction stir spot welding

The present study applied friction spot joining (FSJ), which was recently developed as a lap joining technique of Al alloys, to two sheets of Al alloy 6061, 1 mm in thickness, and then examined the microstructural feature in the weld. The weld had the nugget-shaped stir zone around the exit hole of the probe, and the stir zone exhibited the equiaxed grain structure having finer grain size than that of the base material. The crystallographic texture analysis using electron backscattered diffraction method suggested that the material movement occurred along the rotating direction of the welding tool in the wide region including the stir zone. In the periphery of the nugget-shaped stir zone, which was characterized as the region having the finer grain size than that of the stir zone interior, any inclusions and precipitates were not found in the SEM scale. The weld was softened around the weld centre. The softening could be explained by dissolution and/or growth of the strengthening precipitates due to thermal cycle of FSJ.     

Gradually contacting punch for improving stretch flangeability of ultra-high strength steel sheets

A gradually contacting punch for improving stretch flangeability of ultra-high strength steel sheets having small ductility was developed. In the gradually contacting punch, tensile stress around the corner edge of the sheet in stretch flanging is decreased by gradually pressing the edge of the sheet with the inclined bottom of the punch. The critical flange heights of bent 980 and 1180 MPa ultra-high strength steel sheets without fracture with the gradually contacting punch increased by 32% and 31%, respectively. In addition, the stroke limit of the press was avoided by 2-stage flanging consisting of peripheral bending and corner bending.     

SOME FUNDAMENTAL ATTRIBUTES OF FAR INFRARED RADIATION DRYING OF POTATO

Drying experiments were carried out using a far infrared heater to examine the drying characteristics of potato slices. The effect of several parameters e.g. radiation intensity, inlet air velocity and relative humidity on moisture and temperature history are presented. FIR drying of potato was observed to be a falling rate process. Drying rates were negatively correlated with air velocity. Relative humidity did not influence the drying rate. It was found that the modified exponential law describes the moisture removal of potato within an acceptable range.     

Sediment greenhouse gases (methane and carbon dioxide) in the Lobo-Broa Reservoir, São Paulo State, Brazil: Concentrations and diffuse emission fluxes for carbon budget considerations

Carbon gases (methane, CH₄, and carbon dioxide, CO₂) were measured for the first time in sediments of the Lobo‐Broa Reservoir, near São Carlos in São Paulo State, Brazil. It is believed these are the first measurements of this kind in any of the many reservoirs located in Brazil. Even though the Lobo‐Broa Reservoir is classified as oligotrophic, the sediment gas concentrations were exceedingly high, ranging from 0.4–3 mmol L^?1 for CH₄ and 1–9 mmol L^?1 for CO₂. Both gases exceeded their in situ gas saturation values at these shallow water depths (7 m in central basin; 11 m at dam), resulting in numerous sediment bubbles. Organic matter was highly concentrated in the reservoir sediments, averaging 25.5% loss on ignition (LOI) (dam) to 26.9% LOI (central basin) for the 0–12 cm depth interval, with values as high as 29–30% LOI (12% organic carbon) in the surface 0–5 mm layer. The theoretical flux of dissolved pore water carbon gases to the sediment–water interface (SWI) averaged 3.4 mmol L^?1 m^?2 day^?1 CH₄ and 7.3 mmol L^?1 m^?2 day^?1 CO₂ for the surface 0–10 mm. From gas emission measurements at the water surface, it was calculated that 90% of CH₄ is consumed either at the SWI or in the water column, resulting in a loss of 0.31 mmol L^?1 m^?2 day^?1 of CH₄ to the atmosphere. However, only 20% of the total CO₂ gas transported across the water–atmosphere interface (36.3 mmol L^?1 m^?2 day^?1, or 1600 mg CO₂ m^?2 day^?1) was produced in the sediments. The remaining 80% of CO₂ probably comes from other carbon sources. With CH₄ oxidation in the aerobic water column, close to 30% of the carbon gas flux to the atmosphere could be accounted for by gas production of CO₂ and CH₄ in the sediments and their diffuse transport to the water column.     

Influence of Ni2+ and Co2+ on methanogenic activity and the amounts of coenzymes involved in methanogenesis

The requirement of Ni2+ and Co2+ addition on methanogenic activity and the coenzymes involved in methanogenesis were investigated in anaerobic continuous cultivation with synthetic wastewater using acetate as the sole carbon source. Addition of Ni2+ and Co2+ to the synthetic wastewater drastically increased the maximum dilution rate of the cultivation. The concentrations of coenzymes F430 and corrinoids in the biomass increased to 0.62 micromol-Ni/g-VSS and 0.67 micromol-Co/g-VSS, respectively with the increase of the dilution rate. Methanogenic activity of the culture broth also increased with an increase of dilution rate. However, without addition of Ni2+ and Co2+, F430 and corrinoids were not detected in the biomass and methanogenic activity was only a trace level at a dilution rate of 0.025 d(-1). When the amounts of Ni2+ and Co2+ added at a dilution rate of 0.6 d(-1) were lowered in steps, the concentrations of F430 and corrinoids in the biomass and methanogenic activity decreased with decreasing amounts of Ni2+ and Co2+ added. These results suggest that Ni2+ and Co2+ were required for the methane-producing reactions via increases of coenzymes F430 and corrinoids.     

Coexisting phenomena of surge and rotating stall in an axial flow compressor

The unsteady inner flow structure of a single-stage axial flow compressor under the coexisting conditions of surge and rotating stall was experimentally investigated via detailed measurements of the unsteady characteristics and the internal flow velocity fluctuations. The main relevant feature of the tested compressor is a shock tube with a capacity tank connected in series to the compressor outlet through slits and a concentric duplex pipe： surge and rotating stall can both be generated by connecting the shock tube. Research attention is focused on the unsteady behavior of a rotating stall during the surge cycle. The size of the rotating stall cell during the recovery process of an irregular surge cycle was experimentally determined by the circumferential flow velocity fluctuations ahead of the rotor blade. The results suggested that the size of the rotating stall cell at the switching point of the performance curve between large and small cycles is considered to be the key parameter in determining the following surge cycle. In addition, the surge cycle is largely influenced by the unsteady behavior of the rotating stall cell.     

Purification and characterization of a novel glutamyl aminopeptidase from chicken meat

A novel glutamyl aminopeptidase (aminopeptidase A, EC 3.4.11.7) was purified from chicken meat by ammonium sulfate fractionation, ethanol fractionation, heat treatment, and successive column chromatographies of DEAE-Sepharose CL-6B and Sephadex G-200. The purified enzyme migrated as a single band on SDS-PAGE. The molecular weight of this enzyme was found to be 55,000 and 550,000 by SDS-PAGE and Sephadex G-200 column chromatographies, respectively. This enzyme hydrolyzed Glu- and Asp-, but not Leu-, Arg-, and Ala-2-naphthylamide (-2NA) at all. The optimum pH and temperature for hydrolysis of Glu-2NA was 7.5. and 70°C, respectively. Reducing agents such as cysteine and dithiothreitol inhibited the activity of this enzyme at concentrations of 1 mM. However, the activation by Ca(2+) and the inhibition by amastatin were not observed.     

Effect of Welsh Onion (Allium fistulosum L.) on Breadmaking Properties

Breadmaking properties, such as bread height and specific volume, were improved in bread, made with wheat flour blended with Welsh onion (Allium fistulosum L.) powder, which is high in di‐n‐propyl disulfide (Pro₂S₂). Breadmaking properties also were improved in bread prepared from wheat flour blended with Pro₂S₂ alone. Brabender farinographs of Welsh onion powder/wheat flour and Pro₂S₂/wheat flour showed interesting properties in modifying the width of the tail. Size‐exclusion high performance liquid chromatography of the wheat proteins in the control and blended flours showed a profile of low, medium, and high molecular weight peaks. The area of the high molecular weight peak was larger in the 2 blended flours than in control, indicating this protein was important for the improvement.     

Cloning and characterization of a 4-nitrophenol hydroxylase gene cluster from Rhodococcus sp. PN1

A 4-nitrophenol (4-NP)-degrading bacterium was isolated from activated sludge and identified as a Rhodococcus sp. This bacterium, designated as strain PN1, could utilize 4-NP as a sole carbon, nitrogen and energy source. Degradation tests of 4-NP using cell suspensions of strain PN1 revealed that the degradation was induced by 4-NP and that 4-nitrocatechol (4-NC) was one of the metabolites. A gene library was constructed from the total DNA of strain PN1 and introduced into Rhodococcus rhodochrous ATCC 12674. Two recombinant strains showed 4-NP hydroxylase activity, and a 9.1-kb DNA fragment encoding the activity was isolated from one of the strains. In addition, a 2.4-kb smaller fragment expressing the activity was subcloned from the 9.1-kb fragment and sequenced. The sequence analysis showed that the fragment encodes a two-component 4-NP hydroxylase, the predicted amino acid sequence of which exhibits significant similarity to those of phenol hydroxylases and 4-hydroxyphenylacetate 3-hydroxylases belonging to the two-component flavin diffusible monooxygenase (TC-FDM) family proposed by Galán et al. (J. Bacteriol., 182, 627-636, 2000).     

A 1.0-V 230-MHz column access embedded DRAM for portable MPEGapplications

This paper describes a 32-Mb embedded DRAM macro fabricated using 0.13-μm triple-well 4-level Cu embedded DRAM technology, which is suitable for portable equipment of MPEG applications. This macro can operate 230-MHz random column access even at 1.0-V power supply condition. The peak power consumption is suppressed to 198 mW in burst operation. The power-down standby mode, which suppresses the leakage current consumption of peripheral circuitry, is also prepared for portable equipment. With the collaboration of array circuit design and the fine Cu metallization technology, macro size of 18.9 mm² and cell efficiency of 51.3% are realized even with dual interface and triple test functions implemented