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101.
From time immemorial people dealt with size reduction processes (mill, mineral liberation, etc.). As time has passed industrial units for comminution processes have become larger and more sophisticated, but still they perform with low efficiencies [1], [2] and [3]. The strength of a particle is one of its most crucial characteristics due to the mechanical stresses experienced by each particle within an industrial unit. This is because the final size of particles is mostly dependant on the strength distribution of the raw material [4]. In this present study, the ability of a number of statistical formulations to accurately describe the strength distribution of particles was examined. Additionally, selected equations were analyzed and a general expression including the effect of the material and particle size was developed. A number of approaches to define particle strength were considered, and strength in terms of crushing force was chosen. Particle strength in terms of force and in terms of energy was also compared and found to be size independent. Finally, particle strength in terms of stress was examined and compared to the particle strength in terms of force.The ability to describe the compression strength distribution will significantly improve the accuracy of the comminution processes simulation, design and optimization. 相似文献
102.
The synthesis of polymer-stabilized nanoparticles (PSNPs) can be successfully carried out using intermatrix synthesis (IMS) technique, which consists in sequential loading of the functional groups of a polymer with the desired metal ions followed by nanoparticles (NPs) formation stage. After each metal-loading-NPs-formation cycle, the functional groups of the polymer appear to be regenerated. This allows for repeating the cycles to increase the NPs content or to obtain NPs with different structures and compositions (e.g. core-shell or core-sandwich). This article reports the results on the further development of the IMS technique. The formation of NPs has been shown to proceed by not only the metal reduction reaction (e.g. Cu0-NPs) but also by the precipitation reaction resulting in the IMS of PSNPs of metal salts (e.g. CuS-NPs). 相似文献
103.
Bhari Mallanna Nagaraja Dmitri A. Bulushev Sergey Beloshapkin Sarayute Chansai Julian R. H. Ross 《Topics in Catalysis》2013,56(18-20):1686-1694
Ni/K–MgO–ZrO2 catalysts for dry reforming of methane, with a range of Mg/Zr ratios and each containing about 10 wt% Ni, were prepared via Ni nitrate impregnation on MgO–ZrO2 supports synthesized by co-precipitation using K2CO3. It was found that a proportion of the potassium of the precipitant remained in the samples and improved the stability of the catalysts in the reaction. It was also shown that reduction of the catalysts at 1,023 K without calcination in air is necessary for stable and high activity; calcination in air at 1,073 K gives a deterioration of the catalytic properties, leading to rapid deactivation during the reaction. The order of the CH4 conversions of the reduced catalysts after 14 h on stream was as follows: Ni/K–Mg5Zr2 ~ Ni/K–Mg ≥ Ni/K–Mg2Zr5 ? Ni/K–Zr. A catalyst with 0.95 wt% K on MgO–ZrO2 with a Mg:Zr mole ratio of 5:2 showed the best resistance to deactivation. Experiments in a microbalance system showed that there was only negligible coke deposition on the surface of this sample. This behaviour was attributed to the presence of Ni nanoparticles with a diameter of less than 10 nm located on a MgO/NiO solid solution shell doped by K ions; this in turn covers a core of tetragonal ZrO2 and/or a MgO/ZrO2 solid solution. This conclusion was supported by EDS/TEM, XPS, XRD and H2 chemisorption measurements. 相似文献
104.
In Wireless Mesh Networks (WMNs), mobile clients may experience frequent handoffs due to the relatively small transmission range of the mesh routers. Each handoff may lead to packet delays and/or packet losses, which limits the performance of real-time applications over WMNs. In this work, we propose BASH—a Backhaul-Aided Seamless Handoff scheme. BASH takes advantage of the wireless backhaul feature of WMNs, and allows a mobile station to directly access the backhaul channel to probe the neighboring mesh routers. Our work shows that by utilizing the wireless backhaul, BASH (1) reduces the probing latency and, thus, the Layer-2 handoff latency; (2) allows partial overlap of the Layer-2 and Layer-3 handoffs, reducing the overall handoff latency; and (3) shortens the authentication latency by utilizing the transitivity of trust relationship. The experimental results show that BASH achieves an average Layer-2 handoff of 8.9 ms, which supports real-time applications during the handoff. 相似文献
105.
Ho Nyung Lee Dmitri Zakharov Stephan Senz Alain Pignolet Dietrich Hesse 《Integrated ferroelectrics》2013,141(1-4):73-80
Abstract We have successfully grown non-c-axis-oriented epitaxial ferroelectric SrBi2Ta2O9 (SBT) films with (116) and (103) orientations on Si(100) substrates using epitaxial (110)- and (111)-oriented SrRuO3 (SRO) bottom electrodes, respectively. The SRO orientations have been induced by coating the Si(100) substrates with epitaxial YSZ(100) and MgO(111)/ YSZ(100) buffer layers, respectively. All films were sequentially grown by pulsed laser deposition. Specific in-plane orientations of the epitaxial SBT films were found, which are in turn determined by specific in-plane orientations of the epitaxial SRO bottom electrodes. These include a diagonal rectangle-on-cube epitaxy of SRO(110) on YSZ(100) and a triangle-on-triangle epitaxy of SRO(111) on MgO(111). 相似文献
106.
Guoqiang Xie Dmitri V. Louzguine-Luzgin Qingsheng Zhang Wei Zhang Akihisa Inoue 《Journal of Alloys and Compounds》2009,483(1-2):24
The crystallization kinetics and structure changes in a melt-spun Cu50Zr45Ti5 glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu50Zr45Ti5 alloy was crystallized forming Cu10Zr7 and CuZr2 phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate. 相似文献
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Wouter N. Wermink Dmitri Spinu Geert F. Versteeg 《Chemical Engineering Communications》2019,206(4):454-475
The oxidation of ferrous ions in acidic sulfate solutions in the presence of cupric ions at elevated air pressures was investigated in a high-intensity gas–liquid contactor. The study was required for the design of the regeneration steps of the novel Vitrisol® desulphurization process. The effects of the Fe2+ concentration, Cu2+ concentration, Fe3+ concentration, initial H2SO4 concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, i.e., T?=?50?°C, 70?°C, and 90?°C. Most of the experiments were determined to be affected by the mass transfer of oxygen, and therefore true intrinsic kinetics could not be fully determined. An increase in Fe2+ and Cu2+ concentrations, as well as the partial pressure of oxygen and temperature, increased the Fe2+ oxidation rate. H2SO4 did not influence the Fe2+ oxidation rate. An increase in Fe3+ concentration decreased the Fe2+ oxidation rate. Although determined from experiments partially affected by mass transfer, a first order of reaction in Fe2+ was observed, fractional orders in both Cu2+ and O2 were measured, a zero order in H2SO4 was determined, and a negative, fractional order in Fe3+ was obtained. The activation energy was estimated to be 31.3?kJ/mol. 相似文献