稀土及杂质元素对ZA27合金晶间腐蚀的影响

为了从本质上了解杂质与稀土元素对锌铝合金晶间腐蚀的影响 ,探索抑制合金晶间腐蚀的有效途径 ,依据晶界的大角度重位点阵理论编制出相应计算机软件 ,建立含稀土、杂质及 η相颗粒的α相大角度晶界原子集团模型 ,采用递归法计算了α相晶界间的电荷转移 ,由此讨论了杂质 (Pb、Sn、Cd)及稀土元素 (La、Y)对Zn、Al电极电位的影响 .结果表明 ,杂质Pb、Sn、Cd增大原子间的电荷转移量 ,提高Zn、Al电极电位差 ,加速合金的腐蚀 ,稀土元素减小原子间的电荷转移量 ,降低Zn、Al电极电位差 ,具有抑制晶间腐蚀的作用 .     

Strategic commitment to price to stimulate downstream innovation in a supply chain

It is generally in a firm’s interest for its supply chain partners to invest in innovations. To the extent that these innovations either reduce the partners’ variable costs or stimulate demand for the end product, they will tend to lead to higher levels of output for all of the firms in the chain. However, in response to the innovations of its partners, a firm may have an incentive to opportunistically increase its own prices. The possibility of such opportunistic behavior creates a hold-up problem that leads supply chain partners to underinvest in innovation. Clearly, this hold-up problem could be eliminated by a pre-commitment to price. However, by making an advance commitment to price, a firm sacrifices an important means of responding to demand uncertainty. In this paper we examine the trade-off that is faced when a firm’s channel partner has opportunities to invest in either cost reduction or quality improvement, i.e. demand enhancement. Should it commit to a price in order to encourage innovation, or should it remain flexible in order to respond to demand uncertainty. We discuss several simple wholesale pricing mechanisms with respect to this trade-off.     

Tetradecanol dehydrogenation over CuO catalyst supported on BaO, CaO and MgO

Bimetallic Cu/Mg, Ca, Ba mixed oxide compounds acted as catalyst in the dehydrogenation of tetradecanol into tetradecanal, and were characterized by thermal gravimetric analysis, surface area, X-ray diffraction, temperature-programmed reduction and desorption of CO₂. Alkaline earth oxides increased the total basic site concentration in the order of Mg>Ca>Ba. A correlation was found between the total basic site concentration and initial dehydrogenation rate. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microwave Assisted Conversion of Oximes and Semicarbazones to Carbonyl Compounds Using Benzyltriphenylphosphonium Peroxymonosulfate

Summary.  Benzyltriphenylphosphonium peroxymonosulfate in the presence of catalytic amounts of bismuth chloride was found to be an efficient and mild reagent for the oxidative cleavage of oximes and semicarbazones to the corresponding carbonyl compounds under microwave irradiation. Corresponding author. E-mail: haji@cc.iut.ac.ir Received March 4, 2002; accepted (revised) April 8, 2002     

Solid state phase equilibria in the Gd-Si-B system at 1270 K

Solid state phase equilibria in the ternary Gd-Si-B phase diagram have been proposed at 1270 K using X-ray diffraction, scanning electron microscopy and electron probe microanalysis. Prior to this work, the binary systems Gd-B, Gd-Si and Si-B have also been reinvestigated. The main characteristic of the ternary diagram is the occurrence of two new ternary compounds Gd₅Si₂B₈ and Gd₅Si₃B_0.64. The former crystallizes in tetragonal symmetry, space group P4/mbm with unit cell parameters a=7.2665(3), c=8.2229(7) Å, the second one presents hexagonal symmetry, space group P6₃/mcm with unit cell parameters a=8.5080(4),c=6.4141(2) Å. The X-ray structures of the two structurally related phases Gd₅Si₃B_0.64 and host binary Gd₅Si₃ have been refined from three-dimensional single-crystal intensity data to the final R values of 0.036 (R_w=0.046) and 0.046 (R_w=0.055) for 457 and 401 reflections, respectively with [F>4σ(F)]. Both structures exhibit the Mn₅Si₃-type structure, with in addition for Gd₅Si₃B_0.64 a partial occupancy by boron of the normally vacant interstitial site at the center of the Gd₆ octahedron, which corresponds to the origin of the unit cell. Bonding between the interstitial boron atoms and the gadolinium ones forming the Gd₆B polyhedra is indicated by the decrease in the corresponding Gd-Gd distances and consequently in the unit cell volume. Finally, the Gd-Si-B phase diagram is compared with the previously reported Er-Si-B, at 1070 K.     

二茂铁有机锡衍生物的13C,119Sn NMR研究

本文测定了几种二茂铁有机锡衍生物的¹¹⁹Sn,¹³C NMR谱。对其中几种衍生物的¹³C NMR谱进行了归属,从而进一步验证了这类化合物的结构。着重讨论了结构如化合物中取代基X的改变对¹¹⁹Sn化学位移的影响。并对结构如 类化合物N→Sn异侧配位的问题进行了讨论。     

Insertion of benzothiazolium compounds into montmorillonite interlayers

Benzothiazolium compounds exhibit pronounced antimicrobial activities and stimulation effects on plant growth. When applied to fields they can pollute soil colloids. In contact with the soil they can potentially interact with a clay fraction giving rise to clay organocomplexes. Model intercalation complexes were prepared using monoionic montmorillonite and a variety of water-soluble benzothia zolium salts. It was found that the adsorption into the silicate interlayer space proceeds via a cation exchange process. Substantial differences were observed in the extent of the reaction between non-substituted andN-substituted species. The sulphur atoms present in the benzothiazolium molecules repel the surface oxygen atom: this is considered to be the factor responsible for prevention of insertion of the guest cations perpendicular to the layers.