A simple approach to plane strain extrusion with dead metal zone using upper-bound theorem

This paper treats the upper-bound approach to the problem of rigid-plastic deformation in case where the configuration of the deformation zone is previously unknown. The plane strain forward extrusion process with the so-called dead metal zone is analysed by assuming a simple velocity field. The calculations are carried out for the material with or without strain hardening or strain rate sensitivity and for various reduction ratios. The numerical results show that the region of the dead metal zone becomes smaller with the increase in the reduction ratio. The calculated punch forces agree with the experimental ones fairly well. Furthermore, it is found that the dead metal zone becomes larger with increasing the strain hardening as well as the strain rate sensitivity of the material.     

Enhanced Infrared Absorption of C60 on Thin Evaporated Pd Island Films

Infrared transmission spectra of C₆₀ multilayers on thin Pd films deposited onto surface-oxidized Si(100) and hydrogen-terminated Si(111) substrates are reported. In both cases, the spectra in the 1500–1100 cm⁻¹ region exhibited bands at 1444, 1429, and 1182 cm⁻¹ due, respectively, to the A_g (2), T_1u (4), and T_1u (3) modes. The appearance of the A_g (2) mode, which is originally infrared inactive (Raman active), reveals electron transfer from the metal to chemisorbed C₆₀. Indeed, increasing the thickness of C₆₀, the A_g (2) mode intensity saturated more rapidly than the T_1u (4) and T_1u (3) modes. The originally infrared active T_1u (4) and T_1u (3) modes were enhanced in intensity depending upon the Pd thickness. Actually, while both substrates gave nearly the same magnitude of enhancement, the optimum Pd thickness was smaller on the hydrogen-terminated surface than on the surface-oxidized surface. On the other hand, the A_g (2) mode was less intense on the hydrogen-terminated surface than on the oxidized surface, suggestive of a shortage of chemisorbed C₆₀ and thus pointing out the importance of the metal film morphology. Indeed, Pd films deposited on the two substrates gave rise to quite different AFM images. We also show that, regardless of the substrate, the A_g (2) mode is an order of magnitude smaller than for Ag deposition, though no remarkable intensity differences were observed with respect to the T_1u (4) and T_1u (3) modes.     

Prediction of mill load in hot strip mill rolling

It has been ascertained whether or not the model capable of predicting the stress-strain relation of plain carbon steels, previously proposed, is applicable to the estimation of mill loads in the finishing process (consisting of six mill stands) of a hot strip mill. An appreciably good agreement with the predicted and measured mill load values has been obtained in the earlier passes where the strip microstructure is regarded to have completed static recrystallization, and the predicted mill loads in the later passes have been far less than the measured load owing to the effect of the strain accumulated in the previous rolling process. Then, a simple model to predict the accumulated strain has been constructed and introduced into the calculation of mill loads. As a result, the predicted mill loads have been fairly improved over the whole passes in the finishing process.     

Berechnung über das Umformverhalten von Brammen beim Vertikalwalzen

Rechnerisches Modell aus starr-plastischen finiten Elementen zum Ermitteln des Umformverhaltens von Brammen beim Vertikalwalzen. Berechnungsbeispiel zum Ermitteln des Einflusses der Breitenabnahme, der Form der Walze, des Walzendurchmessers und der Brammenbreite auf den Walzvorgang.     

Real-time IR and mass spectroscopic study of the reaction process of WF6 and a-Si:H:F

The deposition process of W from WF₆ onto a-Si:H:F film was studied by polarization modulation IR spectroscopy combined with quadruple mass spectrometry. The IR spectrum of the a-Si:H:F film formed by the spontaneous chemical deposition method (deposition temperature 373 K) showed that such fluorinated and hydrogenated Si species as —SiF₂, —SiF₂H and —SiH₂ were incorporated in the film. The lowest temperature at which W was deposited was 403 K. The intensity reduction of the IR bands due to the hydrogenated and fluorinated Si species as well as the evolutionary behaviour of the reaction products SiF₄ and H₂ depended upon the reaction temperature. At temperature between 403 K and 423 K, the IR band intensity of the —SiH₂ species remained unchanged in early stages of WF₆ exposure, while the bands due to —SiF₂ and —SiF₂H species decreased linearly with exposure time. No evolution of H₂ was observed as long as the —SiH₂ species remained unchanged, through SiF₄ evolved into the gas phase just after the beginning of the exposure. These results suggest that WF₆ reacts preferentially with the fluorinated silicon species in the films.     

Composition,Structure, and Color of Fat Bloom Due to the Partial Liquefaction of Fat in Dark Chocolate

A type of fat bloom, which had not previously been fully characterized, was investigated to identify the state of its existence and its formation mechanism. Samples of bloom on solid chocolate resulting from the partial liquefaction of fat during temperature variations were analyzed to determine the crystal characteristics, fat contents, and triacylglycerol (TAG) compositions. Also, observation and elemental analyses were performed by scanning electron microscope with an energy-dispersive X-ray spectrometer, color analyses of minute regions were made by using PARISS^®, and Fourier-transform infrared (FT-IR) analyses were performed. The dark- and light-brown areas did not show any differences in fat content or TAG compositions that could lead to the observed color differences. Although differences in component distributions were noted in micrometer-sized regions, no relation to the colors was confirmed. The bloom samples in this study and bloom developed without a tempering process resembled each other in the tone of color at their discolored regions, but the states they adopted differed from one another. It is suggested that the color in this type of bloom was affected by the roughness and/or porosity of the microstructure and could also be a result of the coarsened fat crystal network and of the liquid fat migration.     

Cloning and sequence analysis of hydroxyquinol 1,2-dioxygenase gene in 2,4,6-trichlorophenol-degrading Ralstonia pickettii DTP0602 and characterization of its product

A gene encoding hydroxyquinol 1,2-dioxygenase was cloned from 2,4,6-trichlorophenol-degrading Ralstonia (Pseudomonas) pickettii strain DTP0602. Cell-free extracts of Escherichia coli containing a cloned 1.4-kb StuI-XhoI DNA fragment of R. pickettii DTP0602 hydroxyquinol 1,2-dioxygenase converted hydroxyquinol into maleylacetate and also degraded 6-chlorohydroxyquinol. The 1.4-kb DNA fragment contained one open reading frame (designated hadC) composed of 948 nucleotides. The molecular mass of 34,591 deduced from the gene product (HadC) was in agreement with the size (35 kDa) of the purified HadC protein determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The amino acid sequence of HadC exhibited high homology to that of the hydroxyquinol 1,2-dioxygenase of 2,4,5-trichlorophenoxyacetic acid-degrading Burkholderia cepacia AC1100 (Daubaras, D. L. et al., Appl. Environ. Microbiol., 61, 1279-1289, 1995). The active enzyme had a molecular mass of 68 kDa, suggesting that it is functional as a homodimer. The enzyme also catalyzed the oxidation of pyrogallol and 3-methylcatechol, possible intermediates in the degradation of 2,4,6-trichlorophenol, in addition to 6-chlorohydroxyquinol and hydroxyquinol. The dioxygenase catalyzed both ortho- and meta-cleavage of 3-methylcatechol.