Depicting the role of gas-solid interactions on the hydrodynamics of converging pneumatic riser

The understanding of the flow characteristics and effect of gas-solid interactions in pneumatic risers is fundamental to investigate to ensure effective design cost-effective operation. Thus, to understand the effect of gas-solid interactions on the hydrodynamics of newly proposed conversing risers, this study mainly focused on predicting pressure drop in the dilute phase pneumatic conveying system. The experiments were conducted in a converging riser having a convergence angle of 0.2693°. Various solid particles such as sago, black mustard, and alumina have been considered to study the effect of particle sizes and density on the pressure drop. The experimental outcomes indicate that the total pressure drop increases with an increase in the solid density and gas mass flow rate. Moreover, smaller particle sizes are also increased the pressure drop. An empirical correlation is developed for the prediction of total pressure drop ΔP_T in converging pneumatic riser via dimensional analysis. All dependent variables such as particle and air density, drag force, acceleration due to gravity, the mass flow rate of air and particle, the diameter of particle and converging riser, the height of converging riser were considered to develop the empirical correlation. The established relationship is tested, and experimental data have been fitted for its validation. The estimated relative error of less than 0.05 proved the significance of the developed correlation. Hence, it can be stated that the established relationship is useful in studying the effects of various parameters on the pressure drop across the length of the conversing riser.     

A comprehensive review of renewable energy resources for electricity generation in Australia

Recently, renewable energy resources and their impacts have sparked a heated debate to resolve the Australian energy crisis. There are many projects launched throughout the country to improve network security and reliability. This paper aims to review the current status of different renewable energy resources along with their impacts on society and the environment. Besides, it provides for the first time the statistics of the documents published in the field of renewable energy in Australia. The statistics include information such as the rate of papers published, possible journals for finding relative paper, types of documents published, top authors, and the most prevalent keywords in the field of renewable energy in Australia. It will focus on solar, wind, biomass, geothermal and hydropower technologies and will investigate the social and environmental impacts of these technologies.     

An experimental study of the synergistic effects of BMIM.BF4, BMIM.DCA and TEACl aqueous solutions on methane hydrate formation

In this work, the effects of three ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium dicyanamide and tetraethyl-ammonium chloride, on methane hydrate formation and dissociation kinetic parameters were studied. The kinetic parameters including the initial rate of hydrate formation, hydrate stability at atmospheric pressure and hydrate storage capacity were evaluated. The experimental measurements were performed in an initial pressure range of 3.5–7.1 MPa. It was found that both of ILs with imidazolium-based cation increase the initial methane hydrate formation rate while the IL with ammonium-based cation leads to a decrease in the initial methane hydrate formation rate. It was also interpreted from the results that all of the three studied ILs decrease methane hydrate stability at atmospheric pressure and increase methane hydrate storage capacity. Finally, both of ILs with imidazolium-based cations were found to have higher impacts on decreasing hydrate stability at atmospheric pressure and increasing the methane hydrate storage capacity than the applied IL with ammonium-based cation.     

Structural and Magnetic Studies of Ga-doped Yttrium Iron Garnet

Ga-doped Yttrium Iron Garnet (Y₃Ga_xFe_5-xO₁₂,Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased.SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration.Raman spectroscopy measurements confirmed the replacement of Fe³⁺ ions by Ga³⁺ ions in the garnet structure was revealed by the observed blue shifts in Raman spectra.The saturation magnetization decreased from 28.2 to 4.98 emu g^-1 with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga³⁺ ions for Fe³⁺ ions at tetrahedral sites.Room temperature M?ssbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites,and the development of additional components with increasing Ga concentration.Analysis of the magnetic data and M?ssbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.     

Removal of lead(Pb(Ⅱ))and zinc(Zn(Ⅱ))from aqueous solution using coal fly ash(CFA)as a dual-sites adsorbent

Coal fly ash(CFA)is composed of minerals containing some oxides in crystalline phase(i.e.,quartz and mullite),as well as unburned carbon as mesoporous material,thus enabling CFA to act as a dual-sites adsorbent with unique properties.This work focused on the adsorption of Pb(Ⅱ)and Zn(Ⅱ)from binary system,a mixture containing two metal ion solutions present simultaneously,onto NaOH-modified CFA(MCFA).Several adsorption tests were conducted to evaluate the effect of several parameters,includ-ing pH and contact times.The experiment results indicated that chemical treatment of CFA with NaOH increased pore volume from 0.021 to 0.223 cm3 g-1.In addition,it could also enhance the availability of functional groups on both minerals and unburned carbon,resulting in almost 100％Pb(Ⅱ)and 97％Zn(Ⅱ)adsorbed.The optimum pH for adsorption system was pH=3 and quasi-equilibrium occurred in 240 minutes.Equilibrium data from the experimental results were analyzed using Modified Extended Langmuir(MEL)and Competitive Adsorption Langmuir-Langmuir(CALL)isotherm models.The analysis results showed that the CALL isotherm model could better describe the Pb(Ⅱ)and Zn(Ⅱ)adsorption pro-cess onto MCFA in binary system compared with MEL isotherm model.     

铁素体渗氮工艺模拟

纯铁的莱勒图被广泛用于选择合金钢的渗氮工艺。本文首次采用计算热力学来确定AISI 4140钢的莱勒图。研究表明，AISI 4140钢的莱勒图与纯铁的存在明显差异。对AISI 4140钢进行了渗氮试验，目的是验证计算热力学的预测结果。扫描电镜结果显示化合物层中存在两种相，利用透射电镜对化合物层与扩散层界面的研究结果证实了γ′-Fe4N和ε-Fe2－3（C，N）相的共存。这些试验结果与用计算热力学建立的AISI 4140钢莱勒图高度吻合。     

对话

正Héctor Esrawe毕业于墨西哥伊比利亚美洲大学,2003年创建Esrawe工作室,开始了他独立设计师的职业生涯。Esrawe工作室主要涉及博物馆、酒店、餐馆、酒吧、办公室、住宅的设计以及产品包括家具的创新与定制。Héctor Esrawe认为,设计是一个将使用者和周围环境相联系并发生生动对话的过程。在选材方面,他对玻璃、木材、金属和石材等情有独钟,同时对新工艺和新材料的探索也有着极大的热忱。     

CFD modeling of immiscible liquids turbulent dispersion in Kenics static mixers: Focusing on droplet behavior

The present study is concerned with the computational fluid dynamics(CFD) simulation of turbulent dispersion of immiscible liquids, namely, water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software. To study the droplet size distribution(DSD), the Eulerian formulation incorporating a population balance model(PBM) was employed. For the Eulerian–Lagrangian approach, a discrete phase model(DPM) in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution(RTD) of droplets.In both approaches, a shear stress transport(SST) k-ω turbulence model was used. For validation purposes, the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor, Sauter mean diameter and the mean residence time. The reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean diameter. In addition, the influence of important geometrical and operational parameters, including the number of mixing elements and Weber number, was studied. It was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.     

Finite-time consensus protocols for multi-dimensional multi-agent systems

A finite-time consensus protocol is proposed for multi-dimensional multi-agent systems, using direction-preserving signum controls. Filippov solutions and nonsmooth analysis techniques are adopted to handle discontinuities. Sufficient and necessary conditions are provided to guarantee infinite-time convergence and boundedness of the solutions. It turns out that the number of agents which have continuous control law plays an essential role in finite-time convergence. In addition, it is shown that the unit balls introduced by ?p norms, where p∈[1,∞], are invariant for the closed loop.