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Mathematically modeling fixed-bed adsorption in aqueous systems
Zhe Xu, Jian-guo Cai, Bing-cai Pan
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2013, 14(3): 155-176.
https://doi.org/10.1631/jzus.A1300029
Adsorption is one of the widely used processes in the chemical industry environmental application. As compared to mathematical models proposed to describe batch adsorption in terms of isotherm and kinetic behavior, insufficient models are available to describe and predict fixed-bed or column adsorption, though the latter one is the main option in practical application. The present review first provides a brief summary on basic concepts and mathematic models to describe the mass transfer and isotherm behavior of batch adsorption, which dominate the column adsorption behavior in nature. Afterwards, the widely used models developed to predict the breakthrough curve, i.e., the general rate models, linear driving force (LDF) model, wave propagation theory model, constant pattern model, Clark model, Thomas model, Bohart-Adams model, Yoon-Nelson model, Wang model, Wolborska model, and modified dose-response model, are briefly introduced from the mechanism and mathematical viewpoint. Their basic characteristics, including the advantages and inherit shortcomings, are also discussed. This review could help those interested in column adsorption to reasonably choose or develop an accurate and convenient model for their study and practical application.
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Immobilization of heavy metals in sludge using phosphoric acid and monobasic calcium phosphate
Ping Tang, Yong-chao Zhou, Zhen-miao Xie
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2013, 14(3): 177-186.
https://doi.org/10.1631/jzus.A1200263
The purpose of this research is to investigate the potential of pre-treatment with phosphoric acid (PA) and monobasic calcium phosphate (MCP) for the stabilization of heavy metals in sludge and its bottom ash. The tannery sludge samples were collected in Wenzhou, China and heavily contaminated with heavy metals, such as Pb, Cr and so on. The samples were pre-treated with PA or MCP. Then XRD and TCLP tests were adopted as the evaluating methods to characterize the Pb, Cr, Cu, Zn and Cd immobilization in the pre-treated sludge and its bottom ash. The results showed that this treatment effectively immobilized Pb and Cd in the sludge, lightly stabilized the metal Cu, and adversely, enhanced the leachability of Zn. After incineration at 900 °C, Pb and Cr in the bottom ash of pre-treated sludge were significantly stabilized due to the formation of their highly thermostable phosphates and pyromorphite-like minerals during the incineration process. However, an increase of Cu and Zn solubility was observed which might be attributable to the acidification of sludge due to the addition of PA or MCP.
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Characteristics of bifurcation and buckling load of space truss in consideration of initial imperfection and load mode
Su-deok Shon, Seung-jae Lee, Kang-guk Lee
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2013, 14(3): 206-218.
https://doi.org/10.1631/jzus.A1200114
This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss, which were sensitive to initial conditions. The critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness matrix. The two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence, and characteristics of the parameters as defined by the load ratio of the center node and surrounding node, as well as rise-span ratio were performed. The sensitivity to the imperfection of the initial shape of the two-free-nodes example, which occurs due to snapping at the critical point, resulted in bifurcation before the limit point due to the buckling mode, and the buckling load was reduced by the increase in the amount of imperfection. The two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes, and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or bifurcation. Furthermore, the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified model. The star dome, which was used to examine the influence among several nodes, indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was higher. Besides, global buckling is occurred with reaching bifurcation point as the value of load ratio was higher, and the buckling load level was about 50%–70% of load level at limit point.
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Soundscape of the West Lake Scenic Area with profound cultural background—a case study of Evening Bell Ringing in Jingci Temple, China
Jian Ge, Min Guo, Miao Yue
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2013, 14(3): 219-229.
https://doi.org/10.1631/jzus.A1200159
From the case study of Evening Bell Ringing at Nanping Hill, one of the West Lake Cultural Landscapes in Hangzhou, China, we investigated the soundscape of a scenic area with a profound cultural background. First, we conducted the soundscape physical index of the area in both winter and spring seasons to analyze its objective graphical expression. Second, we focused on people’s reactions to the soundscape in order to obtain a subjective evaluation of each component in the soundscape and integrated environment. Then, the relationship between the objective data and the subjective evaluation was analyzed. Finally, the impacts of the natural environment, history, and cultural factors on the evaluation of the Jingci Temple soundscape were studied. It was found that natural sounds, cultural sounds, and historic sounds were widely acclaimed in people’s subjective feelings, which indicated the close relationships among historical and cultural background, soundscape, and natural environment. Thus, the conclusion was made that soundscape should be consistent with the local natural environment and the historical and cultural background.
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7 articles
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