Review of cold spraying and its use for metallic glass coatings

Cold spraying (CS), a solid-state spraying technology, is expected to become an appropriate supplementary for traditional spraying methods owing to its plenty of merits such as high deposition efficiency, low temperature and little influence on the particles/substrate. The most reported researches are bulk alloys fabricated by CS. However, the systematic introduction and cold-sprayed metallic glass coatings have not been summarised. Therefore, in this paper, the international research status of CS including equipment structure, spraying process and parameters, advantages and disadvantages, deposit features and bonding mechanism were introduced. By using this technology, the successful researches about Fe-, Al-, Ni-, Cu- and Zr- based amorphous alloy coatings are reported. To overcome the limitations, further development and solutions were proposed.     

DRYING OF TOBACCO PARTICLES IN A MOBILISED BED

ABSTRACT

The drying performance of a novel device capable of mobilising a bed of fibrous materials is evaluated. The drying kinetic of the vegetable product used for this work, cut lamina tobacco particles, was determined from fixed bed experiments. A falling-rate period was observed for the entire drying curve. The results showed that the drying rate is controlled by internal mass transfer mechanism for gas superficial velocities above 0.8 m/ s. The proposed model is based on an effective liquid diffusion coefficient that varies with solids temperature according to an Arrhenius-type relationship. Batch drying experiments were carried out in the mobilised bed apparatus under various conditions of inlet air temperature, humidity and flowrate. Assuming perfect mixing and no internal resistance to heat transfer for the solids, the performance of the mobile bed can be predicted using the proposed internal liquid diffusion model     

Rolling and sliding wear properties of hybrid systems composed of uncured/cured HNBR and partly polymerized cyclic butylene terephthalate (CBT)

The phase structure, rolling and sliding wear properties of the hybrids composed of uncured/cured hydrogenated acrylonitrile/butadiene rubber (HNBR) and partly polymerized cyclic butylene terephthalate oligomers (CBT) were investigated. The ratio between HNBR and CBT was varied in the hybrids between 1:0.5 and 1:2. The CBT conversion and phase structure were studied by extraction, differential scanning calorimetry, and dynamic-mechanical thermal analysis.The rolling and sliding wear behaviors of the hybrids under unlubricated condition were determined by using various wear test rigs. It was found that the partly polymerized CBT worked as reinforcement in the HNBR matrix. The specific wear rate of the compounds usually decreased with increasing amount of CBT in both rolling and sliding wear tests. The coefficient of friction (COF) of the hybrids strongly depended on the type and configuration of the wear tests. Dynamic vulcanization of the HNBR in the HNBR/CBT mixes mostly improved the tribological performance. The wear mechanisms were studied as a function of CBT content and discussed.     

Nimesulide adsorbed on silica aerogel using supercritical carbon dioxide

Silica aerogel (SA) was loaded with nimesulide, a drug model compound, to demonstrate the potentiality of adsorption processes based on the usage of supercritical carbon dioxide to treat poorly water-soluble drugs, forming new kinds of drug delivery systems. Adsorption isotherms and kinetics were measured and described by models. The effect of pressure, temperature and solution concentration on loaded SA were also studied. Modelling of kinetic data showed that the sorption process was best described by a pseudo-second-order model. The adsorption isotherm data were best fitted by the Freundlich isotherm. The drug/SA composites were characterized using scanning electron microscopy, X-ray microanalysis, and FT-IR. Release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. Results showed that nimesulide can be uniformly dispersed into the aerogel and that the release rate of nimesulide from the composite, constituted by drug and silica aerogel, is much faster than that of the crystalline drug.     

Trade-offs and individual differences in evolved traits.

Comments on Evolutionary psychology: Controversies, questions, prospects, and limitations (see record 2010-02208-001) by Confer et al. We applaud Confer et al.’s (February–March 2010) clarifications of the many misconceptions surrounding the use of evolutionary analyses in psychology. As they noted, such misunderstandings are common and result in a curious tendency of some of our colleagues to criticize evolutionary psychology without a firm understanding of evolution itself. Confer et al. also did an admirable job acknowledging current unresolved issues among evolutionary psychologists (e.g., the relative importance of group selection on humans). The above said, we disagree with their view that a current limitation of evolutionary psychology is its inability to explain phenomena “that appear to reduce an individual’s reproductive success, and cannot be explained by mismatches with, or hijacking of, our psychological mechanisms by modern-day novel inputs” (Confer et al., 2010, p. 122). Mismatches between modern environments and environments of evolutionary adaptedness are only one set of explanations for seemingly maladaptive traits (Nesse, 2005). Another set involves evolutionary trade-offs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mining seismicity in the Witwatersrand Basin:monitoring, mechanisms and mitigation strategies in perspective

The Kaapvaal Craton in South Africa hosts one of the largest gold placer deposits in the world. Mining in the Witwatersrand Basin here has been the source of about one third to one half of the gold ever produced in the world. Gold was discovered in the Johannesburg area in 1886 and after 120 years of continuous operation, mining is currently approaching depths of 4 000 m. In spite of the challenges and risks that the industry has had to deal with including rock temperature, ventilation and water, one of the most feared hazards in the basin has been the threat from the ongoing occurrence of seismicity and rockbursts. The problem first manifested itself by way of the occurrence of tremors roughly twenty years after the commencement of mining operations. This paper traces the history of the approach to rockbursts and seismicity during the 120 year history of mining in the basin. It portrays a picture of the mining seismicity in terms of monitoring phases, mechanisms and mitigation strategies. The work of research organizations over the years is highlighted with a brief mention of current regulation strategies on the part of the mining inspectorate.     

催化超临界水氧化技术研究进展

催化超临界水氧化技术是在超临界水氧化技术基础上,借鉴催化湿式氧化技术发展起来的一种高效环保的有机废弃物处理技术,可以提高有机污染物的氧化速率,降低工艺条件,拥有十分广阔的应用前景。综述了近年来催化超临界水氧化技术在处理工业污水中催化剂、反应机理、反应动力学、反应器的研究进展。提出了催化超临界水氧化技术的研究方向,以期为催化超临界水氧化技术处理难降解有机污水的发展提供参考。     

Oil-Lubricated Fretting Behaviors of 304 Stainless Steels under Different Fretting Strokes and Normal Loads

The influence of oil lubrication on the fretting wear behaviors of 304 stainless steel flat specimens under different fretting strokes and normal loads has been investigated. The results proved that fretting regimes and fretting wear behaviors of 304 stainless steels were closely related to the fretting conditions. In general, the increase in normal load could increase wear damage during sliding wear. However, according to the results, a significant reduction in wear volume and increase in friction coefficient was observed when the normal load was increased to critical values of 40 and 50 N at a fretting stroke of 50 μm due to the transformation of the fretting regime from a gross slip regime to partial slip regime. Only when the fretting stroke further increased to a higher value of 70 μm at 50 N, fretting could enter the gross slip regime. There was low wear volume and a high friction coefficient when fretting was in the partial slip regime, because oil penetration was poor. The wear mechanisms were fatigue damage and plastic deformation. There was high wear volume and low friction coefficient when fretting was in the gross slip regime, because the oil could penetrate into the contact surfaces. Unlike the wear mechanisms in the partial slip regime, fretting damage of 304 stainless steels was mainly caused by abrasive wear in the gross slip regime.     

Shaking force balancing of a 2-DOF isotropic horological oscillator

Despite centuries of research and significant advances, the escapement mechanism used to count and maintain oscillations of mechanical time bases remains a complex mechanism and a major source of energy losses. We showed in previous work that, instead of the widely used rotational one degree-of-freedom (DOF) oscillators, 2-DOF flexure oscillators have the potential of revolutionizing mechanical watchmaking by eliminating the traditional escapement, replacing it by a simple crank driving a pin. Additionally, using flexures increases the quality factor of the time base, leading to further potential improvements in timekeeping accuracy and energy consumption. However, a significant challenge of these new time bases is their balancing such that the influence of external accelerations on their frequency is minimized, a necessary condition for accurate timekeeping in portable applications. This article presents a novel 2-DOF planar flexure oscillator called Wattwins and demonstrates how it can be made insensitive to linear accelerations such as gravity. For this purpose, a new approach to shaking force balancing is developed based on the decomposition of perturbations into effects corresponding to different orders of center of mass displacement. A full analytical model for frequency tuning and shaking force balancing of the 2-DOF oscillator is derived using a pseudo-rigid-body model and assuming that it can be decomposed into two independent 1-DOF oscillators. The results are validated by the finite element method and show that practical mechanical watch specifications can theoretically be reached. A physical prototype was also constructed and preliminary experimental results confirm the theory as well as the simulations.