Rapid Tooling by Powder Casting Transferred from RIP Model -Manufacturing Conditions Pursuing Zero Shrinkage

High accuracy is being sought in the rapid manufacturing of long life metal dies and molds by transferring from layer laminated models. Powder casting serves as a promising rapid tooling method as it enables high density filling and thus controls dimensional shrinkage to a considerable extent during sintering and infutrating This study aims to study the relation between the tooling conditions and dimensional changes of powder casting and fmd the conditions at which dimensional changes are minimum. In the experiments performed, a golf ball model was chosen as an exampIe of a small mold and results show that dimensional changes can be controlled to below 0.1%, which will facilitate practical application. By subjecting the cast powder to vibrations after adding the binder to achieve higher density, and adding fme copper powder to a mixture of two different size stainless steel powders for dimensional adjustments, almost zero shrinkage control in rapid tool making was realized.Mechanical Engineerin

3-element super-directive endfire array with decoupling network

Abstract -This paper presents a 3-element super-directive array antenna as a small and high gain antenna. Superdirective array is closely spaced array antenna and its directivity of an end-fire liner array of N isotropic radiators is N 2 . However, antenna characteristics are degraded by strong mutual coupling. The proposed antenna can achieve antenna gain of 8.14dB by using decoupling network to suppress mutual coupling effect

A New Route for Preparation of 2-Deoxy-D-ribofuranose Phospho Sugar

The addition reaction of dimethyl phosphonate to (2R,4S)-4-(tertbutyldimethylsilyl)oxymethyl-2-methyl-1,3-dioxan-5-one (11a), followed by dehydroxylation, provided 1-O-(tert-butyldimethylsilyl)-3-deoxy-3-dimethoxyphosphinoyl-2,4-O-ethylidene-D-erythritol (13a). Elongation of carbon skeleton of the D-erythrose (14) derived from 13a and then acidic methanolysis gave a mixture of methyl 2,4-dideoxy-4-dimethoxyphosphinoyl-alpha,beta-D-erythropentopyranosides (7), which was led to 2-deoxy-D-ribofuranose phospho sugar (4) in an appreciably improved total yield compared with the procedures via previously reported route

Tetra­methyl­ammonium dihydrogen phosphate hemihydrate

In the crystal structure of the title compound, C4H12N+·H2PO4 −·0.5H2O, the anions form an infinite hydrogen-bonded chain along the [10] direction. The anion chains are connected by water mol­ecules, which lie on crystallographic twofold rotation axes, through O—H⋯O hydrogen bonds. These hydrogen bonds are almost perpendicular to the other hydrogen bonds which create an assembled structure of anions. In addition, C—H⋯O hydrogen bonds between anions and cations are observed

Action of Pyrroloquinolinequinol As an Antioxidant Against Lipid Peroxidation in Solution

This is the publisher's version, also available electronically from: http://online.liebertpub.com/doi/pdfplus/10.1089/ars.1999.1.4-547.The activities of pyrroloquinoline quinone (PQQ), a coenzyme of methanol dehydrogenase and amine oxidase, and its reduced form pyrroloquinoline quinol (PQQH2 ) as an antioxidant have been measured in solution. PQQH2 was stable in the absence of oxygen but rapidly auto-oxidized to PQQ in the presence of oxygen in water. PQQH2 was stable in an aprotic solvent such as acetonitrile, even in air. PQQ did not exert appreciable antioxidant activity, whereas PQQH2 exerted higher reactivity than a-tocopherol toward galvinoxyl radical and peroxyl radical. PQQH2 acted as a potent antioxidant against the oxidation of methyl linoleate in acetonitrile induced by azo compound and produced a clear induction period, from which the apparent stoichiometric number was obtained as 1.1. PQQH2 reduced the a-tocopheroxyl radical and spared a-tocopherol in the oxidation of methyl linoleate. These results suggest that PQQH2 may act as a potent antioxidant, particularly in combination with a-tocopherol. Antiox. Redox Signal. 1, 547-554

Roles of bulk γ(L)-Bi₂MoO₆ and surface β-Bi₂Mo₂O₉ in the selective catalytic oxidation of C₃H₆

γ(L)-Bi₂MoO₆ (L: low temperature phase) catalysts, whose surface compositions have a Mo/Bi ratio above = 0.5, exhibited high selectivity in the partial oxidation of C₃H₆, while catalysts with Mo/Bi surface ratios near or below = 0.5 exhibited low selectivity. γ(L)-phase catalysts which have Mo/Bi surface ratios greater than = 0.5, were demonstrated to form β-Bi₂Mo₂O₉ on their surface. An interaction between the β- and γ(L)-phases was observed in these catalysts’ UV–vis spectra at 430 nm. The new β-phase material seems to grow along b-axis of γ(L)-phase, i.e., perpendicular to MoO₂–Bi₂O₂ layers. Structure visualizations revealed that the α-Bi₂Mo₃O₁₂, β-, and γ(H)-phases, which are selective catalysts, contain twin Mo tetrahedral structures, and that their Mo and Bi ions lie on the same plane. The pure γ(L)-phase does not contain this structure. A model for the very rapid transfer of oxygen between the γ(L)- and β-phases is discussed in relation to the kinetics of C₃H₆ oxidation.ArticleJournal of molecular catalysis. A, Chemical. 318(1-2):94-100 (2010)journal articl