136 research outputs found
Liquefiable Ground Treatment Using Cruciform Section Probe Resonant Compaction Method: A Case Study in the Xitong Expressway, Eastern China
No full textThe foundation treatment of liquefiable soil has always been an important part of construction. Sand liquefaction decreases the foundation capacity and can cause severe building, highway, or bridge engineering accidents. This study used self-developed cruciform section probe resonant compaction equipment (CSPRCE) to evaluate the applicability and reinforcement effect of the Xitong Expressway foundation. The cone penetration test (CPT) results showed that this soil was liquefiable ground requiring treatment before construction. Laboratory tests illustrated that the clay particle content was nearly 10% in the surface layer, indicating that the traditional resonant compaction probe (RCP) would not provide effective reinforcement; therefore, we adopted the new resonant compaction method (RCM) for the reinforcement process. The CPT and standard penetration test (SPT) results after foundation reinforcement indicated that the cruciform section probe resonant compaction method (CSPRCM) is suitable for treating the Xitong Expressway liquefiable foundation. Before reinforcement, 7-8 liquefiable soil layers were observed, whereas after reinforcement, no foundation testing points were liquefiable. Cone resistance and unit sleeve friction resistance were both improved by a factor of nearly 3 after the CSPRCM reinforcement. The CSPRCM has wider applicability than traditional vibrating compaction methods, especially for sites with a high content of silt and clay particles. The strengthening mechanism of the CSPRCM is a vibration hammer that generates vibrational energy to obliterate the original soil structure and render the sand completely liquefied; the soil particles then rearrange to form a new structure
Chemically modified magnetic chitosan microspheres for Cr(VI) removal from acidic aqueous solution
No full textA bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsorbent was then used to remove Cr(VI) from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1 mg/g at pH 2.5 and 25 degrees C, and the equilibrium time was determined to be 40-120 min depending on the initial Cr(VI) concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCl with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr(Vl) removal from acidic wastewater. (C) 2016 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved
Removal of chromium(VI) from wastewater using weakly and strongly basic magnetic adsorbents: adsorption/desorption property and mechanism comparative studies
No full textTwo novel strongly basic magnetic adsorbents, quaternary ammonium-modified polystyrene and chitosan magnetic microspheres (Pst-MIMCl and CTS-GTMAC), were prepared using the in situ coprecipitation and emulsion cross-linking methods under mild conditions, with features of strong magnetic responsiveness and high quaternary ammonium group contents. The Cr(VI) adsorption/desorption properties and mechanisms of strongly and weakly basic magnetic adsorbents were compared through simulated wastewater. The strongly basic adsorbent exhibited low pH dependence, and the main adsorption mechanism was ion exchange. The weakly basic adsorbent exhibited high pH dependence, and the major adsorption mechanism was electrostatic attraction. Besides, the strongly basic adsorbent required higher desorption conditions than the weakly basic adsorbent owing to the difference of the desorption mechanisms. Furthermore, the removal selectivity of the strongly and weakly basic magnetic adsorbents was estimated by the chromium plating wastewater. The results demonstrated that the strongly basic magnetic adsorbents exhibited higher selectivity than the weakly basic magnetic adsorbents. In addition, the Pst-MIMCl was selected as the optimal magnetic adsorbent for Cr(VI) recovery from wastewater, with the advantages of strongly magnetic responsiveness, wide pH applicable range, high removal efficiency, high adsorption selectivity and good reusability
Removal of Cr(VI) from aqueous solution using amino-modified Fe3O4-SiO2-chitosan magnetic microspheres with high acid resistance and adsorption capacity
No full textA novel, bioadsorbent material of polyethylenimine-modified magnetic chitosan microspheres enwrapping magnetic silica nanoparticles (Fe3O4-SiO2-CTS-PEI) was prepared under relatively mild conditions. The characterization results indicated that the adsorbent exhibited high acid resistance and magnetic responsiveness. The Fe3O4 loss of the adsorbent was measured as 0.09% after immersion in pH 2.0 water for 24 h, and the saturated magnetization was 11.7 emu/g. The introduction of PEI obviously improved the adsorption capacity of Cr(VI) onto the adsorbent by approximately 2.5 times. The adsorption isotherms and kinetics preferably fit the Langmuir model and the pseudo-second-order model. The maximum adsorption capacity was determined as 236.4 mg/g at 25 degrees C, which was much improved compared to other magnetic chitosan materials, and the equilibrium was reached within 60 to 120 min. The obtained thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption process. Furthermore, the Cr(VI)-adsorbed adsorbent could be effectively regenerated using a 0.1 mol/L NaOH solution, and the adsorbent showed a good reusability. Due to the properties of good acid resistance, strong magnetic responsiveness, high adsorption capacity, and relatively rapid adsorption rate, the Fe3O4-SiO2-CTS-PEI microspheres have a potential use in Cr(VI) removal from acidic wastewater. (C) 2015 Wiley Periodicals, Inc
Two-dimensional discontinuous Galerkin model for flow and mixing within emergent vegetation
No full textCombined pretreatment of lignocellulosic biomass by solid base (calcined Na2SiO3) and ionic liquid for enhanced enzymatic saccharification
No full textA novel method combining a solid base catalyst (Na2SiO3) and a cheaper ionic liquid (1-butyl-3-methylimidazolium, [BMIm]Cl), was proposed and used for the pretreatment of lignocellulosic biomass such as spruce, willow and soybean straw. The addition of calcined Na2SiO3 in [BMIm] Cl pretreatment significantly destroyed the recalcitrant cell wall architecture, removed lignin and hemicellulose, decreased cellulosic crystallinity, and strongly broke lignocellulosic morphology, which enhanced the biomass accessibility for enzymatic hydrolysis. The combined pretreatment seemed more suitable for willow and soybean straw than spruce. According to single factor experiments, the maximum enzymatic hydrolysis yield and glucose yield of willow were 98.6% and 39.5 g/100 g biomass, respectively, 2.6-fold of single pretreatment with [BMIm]Cl
Wind Load Analysis on a High-rise Square-plan Building
No full textabstract: Buildings and other structures, all components and cladding thereof, shall be designed and constructed to resist the wind loads are required in all wind codes. Simple quasi-static treatment of wind loads, which is universally applied to design of low to medium-rise structures, can be either overly conservative or erroneous under-estimated for design of high-rise structures. Dynamic response, vortex, wind directionality, and shedding from other structures are all complicated key factors suppose to be considered in design. Meanwhile, wind tunnel testing is expansive, difficult and sometimes inaccurate even if it is a widely used method in simulation of aerodynamic response. Computational Fluid dynamics (CFD), historically, were two-dimensional (2D) method using conformal transformations of the flow about a cylinder to the flow about an airfoil were developed in the 1930s. A number of three-dimensional (3D) codes were developed, leading to numerous commercial packages, which is more accessible and economical for wind load analysis.Dissertation/ThesisMasters Thesis Civil and Environmental Engineering 201
Numerical Investigation on Flow-Field Characteristics towards Removal of Free-Water by A Separator with Coalescing Plates
No full textThe produced water-containing polymer brings new challenges to oil-water separation in oilfield production, yet separators with coalescing plates to remove free water have been playing an active role. In this paper, the flow-field characteristics of polymer-laden produced water in a separator with coalescing plates are analyzed using computerized mathematical methods to investigate the effects with a water content of 55%, 70%, and 85%, flow rate of 3500 m3/d, 4800 m3/d, and 6000 m3/d, and duration time of 20 min, 40 min, and 60 min on flow-field properties and separating efficiency are studied. The results show that the separating efficiency is positively correlated with water content and duration time, and duration time has the greatest improvement to the separating efficiency, but the enhancement of flow rate may reduce the separating efficiency. It is also observed that the separation efficiency of free-water reached 70.9% and the water content at the oil outlet of the separator reached 20.4% at a duration time of 60 min, when the contained polymer concentration and water content in the oil-water mixture are 500 mg/L and 70%, respectively
ChemInform Abstract: Theoretical Insight into the Selectivities of Copper‐Catalyzing Heterogeneous Reduction of Carbon Dioxide
No full textANTECEDENTS OF EMPLOYEES’ EXTENDED USE OF ENTERPRISE SYSTEMS: A PROACTIVE BEHAVIOR PERSPECTIVE
No full textAfter enterprise systems (ES) are infused to daily businesses, employees’ extended use has already become an important concern to firms striving for reaping benefits from IT investment. Considering the innovative and extra-role nature of extended use, the paper further re-conceptualizes extended use as proactive behaviour. And based on the theory of proactive motivation, a research model is developed to explain how three specific antecedents, i.e., system self-efficacy, leader-member exchange, and system modularity jointly impact employees’ extended use. The model is tested with a survey of enterprise system users in six firms which have already implemented ERP systems, and several meaningful findings are yielded. First, except for leader-member exchange, both system self-efficacy and modularity can positively and directly affect extended use. Second, leader-member exchange, rather than exerting a direct effect, can positively moderate the effects of system self-efficacy and modularity on extended use. Third, system modularity can strengthen the relationship between system self-efficacy and employees’ extended use. The limitations and implications for research and practical fields are discussed
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