Dynamic observations of welding phenomena and finite element analysis in high-frequency electric resistance welding

High-frequency electric resistance welding (hereinafter referred to as HFW) pipes and tubes are used for high-grade line pipes. To cope with the high need for weld seam reliability, the clarification of welding phenomena is important. To clarify the HFW phenomena, at first we developed a HFW simulation system by using electromagnetic, heat conductive and elastic plastic finite element analysis (FEA) methods. Continuous electromagnetic and heat conduction analysis was conducted by subdividing the cross section containing the electrode and the welding point into a large number of two-dimensional models. The temperature distribution in the HFW pipe welding procedure can be successfully simulated by this system. The deformation behaviour in which a portion of the weld rises to the inner and outer surfaces as the result of pressurization from welding rolls can be analysed with this system. Secondly, HFW phenomena have been visualized dynamically using a high-speed video camera technique. The high-intensity part visualized by high-speed images has good accordance with the temperature distribution of the FEA result. High-speed images have visualized the dynamic phenomena of molten metal flow and sputtering of molten steel. Very rapid movement of molten metal in the forming direction along the welding line was observed at the V-convergence point with a speed of 2–50 m s^?1, which was far faster than the welding speed. This rapidly moved molten metal generated the peculiar sputtering which spread the molten metal particles as describing an arc perpendicular to the welding line. These phenomena were assumed to be caused by the electromagnetic force concerning the molten steel at the V-convergence point.     

Comparative field study on precipitation, throughfall, stemflow, fog water, and atmospheric aerosol and gases at urban and rural sites in Japan

Precipitation collected by a wet-only sampler (WP), precipitation collected by a filtering-type bulk sampler (BP), throughfall (TF), stemflow (SF), fog water (FW), and atmospheric aerosol and gases were collected at two sites with different site classifications: an urban site (Mt. Rokko) and a rural site (Mt. Awaga) to investigate canopy-atmosphere interactions and to study the chemistry of precipitation in forested areas located in different atmospheric conditions. Compared to those at the rural site, the monthly volume-weighted pH values at the urban site were not significantly (p>0.05) different for WP, higher (p<0.05) for BP, not significantly (p> 0.05) different for TF, lower (p<0.01) for SF, and lower (p<0.01) for FW. The order of mean pH values at the urban site was FW相似文献   

Locational disadvantage of the hub

We show how spatial evolution is different between the two representative models of economic geography: [Krugman 99:483–499, 1991] and [Ottaviano et al. 43:409–436, 2002]. We analyze the impacts of falling transport costs on the spatial distribution of economic activities and welfare for a network economy consisting of three regions located on a line. It is normally considered that a hub city, i.e., a central region, always has locational advantage and manufacturing workers gain from trade. This is true in the former model, but not in the latter when markets are opened up to trade. This is because the price competition is so keen in the central region that the manufacturing sector moves to the peripheral regions, which aggravates the social welfare. We then show that when goods are close substitutes and share of manufacturing is of an intermediate level, the manufacturing activities completely disappear from the central region leading to a full agglomeration in one peripheral region.

Influence of fermentation temperature on volatile thiols concentrations in Sauvignon blanc wines

The effect of Saccharomyces cerevisiae strains on the amount of 4-mercapto-4-methylpentan-2-one, a major varietal aroma of Sauvignon blanc wines, was demonstrated by previous research work. However, the influence of different alcoholic fermentation parameters on the levels of volatile thiols (4-mercapto-4-methylpentan-2-one, 3-mercaptohexan-1-ol and 3-mercaptohexyl acetate) in wines has not yet been investigated. The impact of fermentation temperature on the final amount of volatiles thiols and on some other analytical parameters (ethanol, total acidity, residual sugars, volatile acidity) was determined in a model medium and in grape juice. Interaction between fermentation temperature and yeast strain was also tested. The fermentation temperature influenced the amount of volatile thiols irrespective of the yeast strain used. The final levels of 4MMP and 3MH in model medium and in wines were higher when the alcoholic fermentation is conducted at 20 degrees C than at 13 degrees C. The 3MHA, which was correlated with the amount of 3MH determined in wines, was also higher when the alcoholic fermentation was conducted at 20 degrees C. From a technological point of view, the choice of yeast strain and fermentation temperature has a decisive influence on the concentrations of the varietal aromas of Sauvignon blanc wines.     

超临界甲醇中PBT的分解行为研究

在超临界甲醇中考察了反应温度,反应压力对聚对苯二甲酸二丁酯（PBT）的分解及单体对苯二甲酸二甲酯（DMT）收率的影响,在此基础上对PBT熔点前后的反应速度常数进行了求解,PBT的分解效果以DMT单体的生成量评价,并采用气相色谱和凝胶色谱（GPC）对液相产物的组成进行分析。结果表明：随反应温度的增加,单体对苯二甲酸二甲酯的回收率增加,250℃,10min时可达92%;反应压力对PBT的分解几乎无影响;在PBT熔点以上,分解反应速度常数明显增大,分解反应速度显著提高;熔点以上进行反应时,分解产物中低聚物的分子量降低,单体收率增加。     

Sensitivity to red/green/blue illumination of amorphous selenium based photodetector driven by nitrogen (N)-Doped CVD diamond

An imaging device that could detect weak light of approximately 0.001 lx with high SN ratio is capable of opening up the possibility of creating artificial visions as a substitute for a human eye. In terms of sensitivity and SN ratio, amorphous selenium (a-Se) is known to be one of the best candidates among other photoconductive target. Combined with a-Se, a diamond cold cathode would be one of the best options in order to steadily emit electrons under low vacuum. The a-Se film is modified with Arsenic (As) and Tellurium (Te) to prevent crystallization and narrow the optical gap for red light detection. An RGB filtered light from a halogen light source was illuminated onto this modified a-Se film and the photo-response was measured for each color. The device could detect extremely weak illumination of under 0.39 lx, which is approximately the darkness under moonlight. Results of the photo-response compared between films with and without Te clarified that Te dopants enhances red light detection significantly. The illuminated light was then pulsed at 10 mHz and the current to time stability was observed. It showed clear correspondence between the intensity of the luminance and current, which the Te modified samples showed good response to other colored light as well.     

The synthesis and thermotropic liquid crystalline behavior of the novel poly(aryl ether ketone)s containing chloro-side group

The novel poly(aryl ether ketone)s containing chloro-side group were synthesized by nucleophilic substitution reactions of 4,4′-biphenol and chlorohydroquinone with either 4,4′-difluorobenzophenone (BP/CH/DF) or 1,4-bis(p-fluorobenzoyl)benzene (BP/CH/BF) and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. The thermotropic liquid crystalline behavior was observed in the copolymers containing 50 and 70% biphenol. Melting transition (Tm) and isotropization transition (Ti) both appeared in the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline state. The novel poly(aryl ether ketone)s had relatively higher glass transition temperature (Tg) in the range of 168 ∼ 200 °C and lower melting temperature (Tm) in the range of 290 ∼ 340 °C. The thermal stability (Td) was in the range of 430 ∼ 490 °C. Received: 7 February 1997/Revised: 31 March 1997/Accepted: 2 April 1997     

Glass fiber having isocyanate group on the surface

Summary Reaction of silanol groups on the surface of glass fiber with diisocyanates were investigated. It was found that the effect of organometallic catalysts upon the reaction varied with their metal ions or their ester substituents. Then the addition reaction of isocyanate group on glass fiber surface, with amino acid was carried out successfully to prepare a glass fiber-amino acid adduct.     

Magnetic properties of metal layer deposited by reduction of polymer containing metal ions

Magnetic properties of metal layer deposited by reduction of polymer containing metal ions were investigated. Varying the ratio of the cobalt ion to the nickel ion in the polymer, the coercivity, the maximum flux density and the remanent flux density of the deposited metal layer were changed from 100 to 600 Oe, from 1 000 to 12 600 G and from 500 to 7 600 G, respectively. The X-ray diffraction pattern of the metal layer with excellent magnetic properties gives distinct peaks corresponding to the (101) and (100) planes of the crystal of α-Co. This suggests that such a deposited metal layer has the structure of highly crystalline metal layer.