Initial Stages in the Metal-dusting Process on Alloy 800

The initial stages of the metal-dusting process on Alloy 800 at 620 °C were investigated by light optical microscopy, RAMAN spectroscopy, atomic-force microscopy, Auger electron spectroscopy, transmission-electron microscopy and electron back-scatter diffraction. As it turned out the incubation period for metal-dusting is characterized by simultaneous formation of a heterogeneously growing oxide scale and deposition of carbon. The material surface shows different tarnish colors depending on the substrate-grain orientation with different susceptibility to the beginning of metal-dusting attack. “Low-index” grains were not attacked within the times investigated while the other grain orientations showed pitting. Carbon is evidently incorporated into the oxide scale from the very beginning of exposure with different intensities depending on the underlying substrate-grain orientation leading to differences in the tarnish colors. As a consequence carbides are formed even underneath “dense” oxide layers. Evidently metal-dusting attack starts at positions of the oxide scale where “higher carbon concentrations” are present.     

Mechanisms of non-toxic anticorrosive pigments in organic waterborne coatings

Investigations have been carried out concerning the mechanism of the behaviour of non-toxic anticorrosive pigments belonging to the group of phosphates, ferrites and ion exchange pigments in waterborne systems. The mechanism controlling the protective effectiveness of organic coatings is complex and results from simultaneous activity of various agents, from among which the kind of the corrosion inhibitor and the structure of the coating are of fundamental importance. The effect of pigments on the protective properties of coatings was tested by means of electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) as well as the salt spray and Prohesion tests. For the investigation of the structure of coatings the porosymetric method and modulated-force thermomechanical analysis (mf TMA) were applied. The results of these investigations have shown that calcium zinc phosphate and zinc ferrite are the most effective. These pigments take part in the passivation of steel, which has been proved by the results of electrochemical investigations and by the presence of the passive layers as has been found out by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDXA) and scanning electron microscopy (SEM). Calcium zinc phosphate and zinc ferrite affect the structure of the coatings, increasing the glass transition temperature (Tg) of the coatings. Zinc phosphate and calcium-exchanged silica do not act in compliance with electrochemical mechanism neither do they improve the barrier properties of the binder.     

Glyoxal Ozonation Process in Aqueous Solution

The process of ozonation of glyoxal in aqueous solution has been studied by following its chemical and kinetic evolution. Results show that the oxidative process leads to formation of carboxylic functions and carbon dioxide according to a constant selectivity ratio at varying conversion degree.. Comparison between the oxygen amounts of reaction products and the corresponding ozone consumptions reveals that molecular oxygen takes part in the reaction process. System behavior is explained on the basis of radical reaction mechanism.     

The Chemistry of Water Treatment Processes Involving Ozone,Hydrogen Peroxide and Ultraviolet Radiation

Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O₃ at high pH, 0₃/H₂0₂, O₃/UV and H₂O₂/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O₃/UV process, the effect of the H₂0₂:0₃ ratio in the O₃/H₂O₂ process, and the impact of the low extinction coefficient of H₂O₂ in the H₂0₂/UV process.     

Incorporating characteristics of human creativity into an evolutionary art algorithm

A perceived limitation of evolutionary art and design algorithms is that they rely on human intervention; the artist selects the most aesthetically pleasing variants of one generation to produce the next. This paper discusses how computer generated art and design can become more creatively human-like with respect to both process and outcome. As an example of a step in this direction, we present an algorithm that overcomes the above limitation by employing an automatic fitness function. The goal is to evolve abstract portraits of Darwin, using our 2nd generation fitness function which rewards genomes that not just produce a likeness of Darwin but exhibit certain strategies characteristic of human artists. We note that in human creativity, change is less choosing amongst randomly generated variants and more capitalizing on the associative structure of a conceptual network to hone in on a vision. We discuss how to achieve this fluidity algorithmically.

A recursive algorithm for generating the equations of motion of spatial mechanical systems with application to the five-point suspension

In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented. The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the concepts of linear and angular momenta. Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation.     

Promoting dark fermentation for biohydrogen production: Potential roles of iron-based additives

Dark fermentation (DF) is a promising technology for biohydrogen production. Low efficiency of biohydrogen production is a bottleneck of the scale-up prospects for DF. Additives have been extensively studied to improve the biohydrogen production efficiency. Among of them, iron-based additives present a promising application potential due to their demonstrated significant enhancement of DF efficiency and among the low-cost bioactive agents. However, current reviews mainly examined the effects of nano-materials on DF and an in-depth analysis of enhancing mechanisms with addition of iron-based additives in DF is still lacking. To this end, this article comprehensively reviewed and evaluated the effects of iron-based additives on DF. Further, the potential mechanisms, including altering metabolic pathways, improving activities of microbes and enzymes, promoting electron delivery, and enriching hydrogen-producing bacteria, were discussed. Lastly, prospects and challenges of iron-based additives for subsequent research and large-scale application for DF were summarized.     

How the Beast really moves: Cayley analysis of mechanism realization spaces using CayMos

For a common class of 2D mechanisms called 1-dof tree decomposable linkages, the following fundamental problems have remained open: (a) How to canonically represent (and visualize) the connected components in the Euclidean realization space. (b) How to efficiently find two realizations representing the shortest “distance” between two connected components. (c) How to classify and efficiently find all the connected components, and the path(s) of continuous motion between two realizations in the same connected component, with or without restricting the realization type (sometimes called orientation type).For a subclass of 1-dof tree-decomposable linkages that includes many commonly studied 1-dof linkages, we solve these problems by representing a connected component of the Euclidean realization space as a curve in a carefully chosen Cayley (non-edge distance) parameter space; and proving that the representation is bijective. We also show that the above set of Cayley parameters is canonical for all generic linkages with the same underlying graph, and can be found efficiently. We add an implementation of these theoretical and algorithmic results into the new software CayMos, and give (to the best of our knowledge) the first complete analysis, visualization and new observations about the realization spaces of many commonly studied 1-dof linkages such as the amusing and well-known Strandbeest, Cardioid, Limacon and other linkages.     

W-4Re-0.27HfC合金的1500~1700℃拉伸蠕变性能及损伤机理

本文研究了粉末冶金制备的W-4Re-0.27HfC合金的拉伸蠕变行为,测试环境为真空,蠕变温度为1500~1700℃,蠕变应力为40~60MPa。采用SEM、EBSD和TEM观察其微观组织,表征晶粒尺寸和位错等组织在蠕变过程中的演变规律。结果表明,W-4Re-0.27HfC合金的稳态蠕变速率范围为1′10-7~5′10-6,较纯钨(W)低两个数量级。W-4Re-0.27HfC合金抗蠕变性能优于纯W主要原因是弥散分布的HfC颗粒钉扎位错和Re取代W原子产生晶格畸变阻碍位错运动,降低位错迁移率。蠕变温度为1500℃时,W-4Re-0.27HfC的蠕变机制以位错滑移为主,伴随有晶界滑动。随着温度升高,位错攀移成为主要蠕变机制。HfC颗粒塞积位错,导致HfC/基体界面结合变差,HfC颗粒剥落出现孔洞,合金蠕变性能下降。