Improved corrosion protection of aluminum alloys by electrodeposited silanes

Organofunctional silanes recently have emerged as outstanding, environmentally friendly corrosion protectors for metal substrates, compared with conventional chromate treatments. A simple immersion technique is typically used to coat the metal surface with silane films. However, the thickness and uniformity of the films are uncontrolled in this process. This paper proposes a new deposition technique for the silane films on the metal surface, i.e., by electrodeposition. Hydrolyzed silanes are water-soluble, ionized molecules, so they can be deposited on metals by electrodeposition. Various combinations of silane mixtures were tested at different voltages, pH values, bath concentrations, and exposure times on panels of alloy aluminum and mirror-polished ferro-plate. The surface structure was characterized by scanning electron microscopy (SEM) and ellipsometry. The resistance of the film to corrosion was investigated by direct current (DC) polarization and electrochemical impedance spectroscopy (EIS) techniques. Electrodeposition results in a more organized and uniform film with fewer pores, compared with immersed or dipped films. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appears on pp. 320–26 of the Proceedings.     

High performance liquid chromatographic separation of sucrose fatty acid esters

The synthesis of sucrose fatty acid esters always results in complex mixtures. Two procedures for quantitative analysis of sucrose monoesters, respectively sucrose diesters, by means of high performance liquid chromatography on reversed-phase columns, are described. A mixture of methanol and water (85:15, v/v) was used for the separation of the monoesters, while methanol, ethyl acetate and water (65:25:10, v/v/v) was used for the separation of diesters. These methods gave information about the amount of monoesters and diesters in the product; the ratio between sucrose monopalmitate and sucrose monostearate, and the number of the most important structure isomers. A complete separation of all the possible diester products seemed to be impossible, due to the presence of more complex structure isomers. The described procedures can give important support during preparative work on sucrose fatty acid esters and also in the evaluation of these products for application purposes.     

Quantum chemical studies of zeolite proton catalyzed reactions

Theoretical chemistry applied to zeolite acid catalysis is becoming an important tool in the understanding of the adsorption and interaction of guest molecules with the zeolitic lattice. Especially the understanding of the mechanisms by which zeolite catalyzed chemical reactions proceed becomes possible. It is shown here that the old interpretation of carbonium and carbenium ions as intermediates for zeolite catalyzed reactions has to be replaced by a new approach in terms of positively charged transition states that are strongly stabilized by the zeolitic lattice. The large deprotonation energy of the acidic zeolite is overcome by stabilization of the intermediate or transition state positive charge by the negative charge left in the lattice. The zeolitic sites responsible for the adsorption and/or reaction of guest molecules are the Brønsted-acid and Lewis-base sites. We also show that different transition states are responsible for different kinds of reactions, such as cracking, dehydrogenation, etc.     

IR在胎面胶中的应用

具有高含量3，4-结构的IR能特别有效地提高高性能轮胎的湿抓着力。因此，可以通过调整炭黑和BR用量来提高轮胎的磨耗和滚动阻力性能，同时保持优异的湿抓着性能。     

Polysulphone and poly(phenylene sulphide) blends: 1. Thermal characterization and phase morphology

The phase behaviour and morphology of injection moulded specimens of polysulphone (PSF) and poly(phenylene sulphide) (PPS) blends were studied by differential scanning calorimetry (d.s.c.), dynamical mechanical thermal analysis (d.m.t.a.) and transmission electron microscopy (TEM). The blends are phase separated regardless of the blend composition as revealed by d.s.c., d.m.t.a. and TEM. Upon annealing at 160°C for 2 h, d.m.t.a. results indicate that the PPS phase remains in the amorphous state at compositions <10%. At compositions between 20 and 35%, the PPS appears to be dispersed in a mixed mode of amorphous and crystalline domains. Above 35% the PPS phase appears to become fully crystallized upon annealing of the blends. At 10% PPS, TEM results showed 35–200 nm size dispersion both in the as-moulded and in the annealed specimens. At 20% the PPS phase varied widely in size, from 35 nm to tens of micrometres but remained as an included phase. TEM also revealed a compound morphology of the included phase at a composition of 50 wt% of each component.     

The lipids of krill (Euphausia species) and red crab (Pleuroncodes planipes)

The composition of the lipids of two samples of krill and one of “red crab” was determined by thin layer, column and gas chromatographic procedures. A large number of unusual fatty acids were present.     

Intrinsic reactivity of gold nanoparticles: Classical, semi-empirical and DFT studies

Gold nanoparticles used in most experiments (1–10 nm) in gold catalysis show varying degrees of reactivity, with particles below 5 nm generally being more reactive. The origin of this activity is a subject of a number of model experiments and theoretical studies on either clusters of a few atoms in size or extended surfaces (smooth or stepped). In the work described here, a classical theory for the variation of the metal workfunction with cluster size, Extended Hückel Theory (EHT) calculations combined with DFT calculations, as well as a carbon monoxide (CO) chemisorption model are combined to develop a relationship between metal particle size and the particle's reactivity towards CO. For gold, it is shown that while the contribution of the d-band hybridization energy to the total CO chemisorption energy is unfavourable for bulk gold, this is not true for gold particles below 5–6 nm. That is, the d-band hybridization energy is negative for small gold particles. This is believed to be explanation of the onset of high reactivity for small gold particles.     

Delineating Boundaries for Imprecise Regions

In geographic information retrieval, queries often name geographic regions that do not have a well-defined boundary, such as “Southern France.” We provide two algorithmic approaches to the problem of computing reasonable boundaries of such regions based on data points that have evidence indicating that they lie either inside or outside the region. Our problem formulation leads to a number of subproblems related to red-blue point separation and minimum-perimeter polygons, many of which we solve algorithmically. We give experimental results from our implementation and a comparison of the two approaches. This research is supported by the EU-IST Project No. IST-2001-35047 (SPIRIT) and by grant WO 758/4-2 of the German Research Foundation (DFG).     

Figure-ground separation by cue integration

This letter presents an improved cue integration approach to reliably separate coherent moving objects from their background scene in video sequences. The proposed method uses a probabilistic framework to unify bottom-up and top-down cues in a parallel, "democratic" fashion. The algorithm makes use of a modified Bayes rule where each pixel's posterior probabilities of figure or ground layer assignment are derived from likelihood models of three bottom-up cues and a prior model provided by a top-down cue. Each cue is treated as independent evidence for figure-ground separation. They compete with and complement each other dynamically by adjusting relative weights from frame to frame according to cue quality measured against the overall integration. At the same time, the likelihood or prior models of individual cues adapt toward the integrated result. These mechanisms enable the system to organize under the influence of visual scene structure without manual intervention. A novel contribution here is the incorporation of a top-down cue. It improves the system's robustness and accuracy and helps handle difficult and ambiguous situations, such as abrupt lighting changes or occlusion among multiple objects. Results on various video sequences are demonstrated and discussed. (Video demos are available at http://organic.usc.edu:8376/ approximately tangx/neco/index.html .).