Layered double hydrotalcites pillared by het erop olyoxometates, ZnAl- GeW11Z (Z=Ni2+, Cu2+) and ZnAl-GeW11 have been synhesized by ion exchange. A procedure for intercalating layered double hydroxides is described in...Layered double hydrotalcites pillared by het erop olyoxometates, ZnAl- GeW11Z (Z=Ni2+, Cu2+) and ZnAl-GeW11 have been synhesized by ion exchange. A procedure for intercalating layered double hydroxides is described in this paper, powder X-ray diffraction and IR spectra measuremnts confirm that for GeW11O39Z (H2O)6- and GeW11O8-39intercalation takes place and the gallery heights are of 9.9A. The new compounds are found to be calalytically efficient for the esterification of acetic acid with n-butanol in liquld-phase.展开更多
Quantitatively correcting the unconfined compressive strength for sample disturbance is an important research project in the practice of ocean engineering and geotechnical engineering. In this study, the specimens of ...Quantitatively correcting the unconfined compressive strength for sample disturbance is an important research project in the practice of ocean engineering and geotechnical engineering. In this study, the specimens of undisturbed natural marine clay obtained from the same depth at the same site were deliberately disturbed to different levels. Then, the specimens with different extents of sample disturbance were trimmed for both oedometer tests and unconfined compression tests. The degree of sample disturbance SD is obtained from the oedometer test data. The relationship between the unconfined compressive strength q u and SD is studied for investigating the effect of sample disturbance on q u. It is found that the value of q u decreases linearly with the increase in SD. Then, a simple method of correcting q u for sample disturbance is proposed. Its validity is also verified through analysis of the existing published data.展开更多
The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate bas...The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate based model is developed to de-scribe the mechanical behaviour for both unstructured and structured clays under one-dimensional loading.The advantage of the proposed model lies in the determination of model parameters in a straightforward way,which leads to an easy use of the model for practical problems.Coupled with consolidation,the model is used to simulate oedometer tests at constant rate of strain and long-term creep oedometer tests on two structured clays.All comparisons between predicted and measured results demonstrate that the proposed model can reasonably describe the effect of destructuration on the time-dependent behaviour of soft structured clay under one-dimensional condition.Although the model is proposed for one-dimensional analysis,it can be a good base for developing a more general 3D model.展开更多
Based on the relationships between the Hvorslev envelope,the current yield sur-face and the reference yield surface,a new constitutive model for overconsolidated clays is proposed. It adopts the unified hardening para...Based on the relationships between the Hvorslev envelope,the current yield sur-face and the reference yield surface,a new constitutive model for overconsolidated clays is proposed. It adopts the unified hardening parameter,to which the potential failure stress ratio and the characteristic state stress ratio are introduced. The model can describe many characteristics of overconsolidated clays,including stress-strain relationships,strain hardening and softening,stress dilatancy,and stress path dependency. Compared with the Cam-clay model,the model only re-quires one additional soil parameter which is the slope of the Hvorslev envelope. Comparisons with data from triaxial drained compression tests for Fujinomori clay show that the proposed model can rationally describe overconsolidated properties. In addition,the model is also used to predict the stress-strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.展开更多
The influences of temperature on the mechanical behavior of saturated clays are discussed first. Based on the concept of true strength and the revised calculation method of the potential failure stress ratio, the equa...The influences of temperature on the mechanical behavior of saturated clays are discussed first. Based on the concept of true strength and the revised calculation method of the potential failure stress ratio, the equation of the critical state stress ratio for saturated clays under different temperatures is deduced. Temperature is introduced as a variable into the UH model （3-dimensional elastoplastic model for overconsolidated clays adopting unified hardening parameter） proposed by Yao et al. and then the UH model considering temperature effects is proposed. By means of the transformed stress method proposed by Yao et al., the proposed model can be applied conveniently to 3-dimensional stress states. The strain-hardening, softening and dilatancy behavior of overconsolidated clays at a given temperature can be described using the proposed model, and the volume change behavior caused by heating can also be predicted. Compared with the modified Cam-clay model, the proposed model requires only one additional parameter to consider the behavior of the decrease of preconsolidation pressure with an increase of temperature. At room temperature, the proposed model can be changed into the original UH model and the modified Cam-clay model for overconsolidated clays and normally consolidated clays, respectively. The considered temperature range here is from the melting point to the boiling point of the pore water （e.g. the experimental temperatures （20℃-95℃） mentioned in this paper are within this range）. Comparison with existing test results shows that the model can reasonably describe the basic mechanical behavior of overconsolidated clays under various temperature paths.展开更多
Ceramic supported cerium, manganese and cerium-manganese catalysts were prepared by direct impregnation of aq precursor, and characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Brunauer-E...Ceramic supported cerium, manganese and cerium-manganese catalysts were prepared by direct impregnation of aq precursor, and characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Brunauer-Emmett-Teller rn （BET）, temperature programmed reduction （Ha-TPR）, X-ray photoelectron spectroscopy （XPS） acidity measurements and elec conductivity. The catalytic activity was evaluated for volatile organic compounds （VOC） （ethanol, methyl ethyl ketone and tol oxidation. Additionally, catalysts were tested in particulate matter （PM） combustion. The characterization results indicated that Ce was in the form of Ce4＋ and Ce3＋, and Mn existed in the form of Mn4＋ and Mn3＋ on the surface of the Mn/AC sample and in the of Mn4＋ in the Ce/Mn/AC monolith. VOC oxidation results revealed that the Ce/Mn/AC sample showed an excellent perforr compared with ceramic supported CeO2 （Ce/AC） and MnO, （Mn/AC） samples. The PM combustion was also higher on Ce/M monoliths. The enhanced catalytic activity was mainly attributed to the Ce and Mn interaction which enhanced the acidity, cond ity and the reducibility of the oxides.展开更多
Adsorption of microcystins (MCs) by carbon nanotubes (CNTs) and clay materials was studied. Compared with various clays tested, CNTs showed a much stronger ability to adsorb MC-RR and LR that were two typical types of...Adsorption of microcystins (MCs) by carbon nanotubes (CNTs) and clay materials was studied. Compared with various clays tested, CNTs showed a much stronger ability to adsorb MC-RR and LR that were two typical types of microcystins found in China. At initial 21.0 mg/L of MC-RR and 9.5 mg/L of MC-LR in solution, the adsorption amounts of MC-RR and LR by CNTs were 14.8 and 6.7 mg/g that were about five times higher than those by the clay ma-terials of sepiolite, kaolinite and talc, etc. In the presence of CNTs and the bacterial Ralstonia solanacearum that was firstly isolated and used for the biodegradation of MCs by the authors, a remarkable removal of MCs from water were observed. The mechanism was that CNTs could absorb large amount of both MCs and the embedded R. solanacearum so that, even when diluted by a large amount of water, the con-centrations of both organic pollutants and the added bacteria could be largely enhanced on the surface of CNTs where a concerted biodegradation reaction was effectively conducted. This finding could be important for the further development of practical techniques to eliminate MCs from polluted drinking waters.展开更多
文摘Layered double hydrotalcites pillared by het erop olyoxometates, ZnAl- GeW11Z (Z=Ni2+, Cu2+) and ZnAl-GeW11 have been synhesized by ion exchange. A procedure for intercalating layered double hydroxides is described in this paper, powder X-ray diffraction and IR spectra measuremnts confirm that for GeW11O39Z (H2O)6- and GeW11O8-39intercalation takes place and the gallery heights are of 9.9A. The new compounds are found to be calalytically efficient for the esterification of acetic acid with n-butanol in liquld-phase.
文摘Quantitatively correcting the unconfined compressive strength for sample disturbance is an important research project in the practice of ocean engineering and geotechnical engineering. In this study, the specimens of undisturbed natural marine clay obtained from the same depth at the same site were deliberately disturbed to different levels. Then, the specimens with different extents of sample disturbance were trimmed for both oedometer tests and unconfined compression tests. The degree of sample disturbance SD is obtained from the oedometer test data. The relationship between the unconfined compressive strength q u and SD is studied for investigating the effect of sample disturbance on q u. It is found that the value of q u decreases linearly with the increase in SD. Then, a simple method of correcting q u for sample disturbance is proposed. Its validity is also verified through analysis of the existing published data.
文摘The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured clays.Viscosity coupled with destructuration is analysed based on experimental observations.A strain-rate based model is developed to de-scribe the mechanical behaviour for both unstructured and structured clays under one-dimensional loading.The advantage of the proposed model lies in the determination of model parameters in a straightforward way,which leads to an easy use of the model for practical problems.Coupled with consolidation,the model is used to simulate oedometer tests at constant rate of strain and long-term creep oedometer tests on two structured clays.All comparisons between predicted and measured results demonstrate that the proposed model can reasonably describe the effect of destructuration on the time-dependent behaviour of soft structured clay under one-dimensional condition.Although the model is proposed for one-dimensional analysis,it can be a good base for developing a more general 3D model.
基金the National Natural Science Foundation of China (Grant Nos. 50479001 and 10672010)the National Science and Technology Supporting Item (Grant No. 2006BAK12B12)the National Basic Research Program of China (Grant No. 2007CB714203)
文摘Based on the relationships between the Hvorslev envelope,the current yield sur-face and the reference yield surface,a new constitutive model for overconsolidated clays is proposed. It adopts the unified hardening parameter,to which the potential failure stress ratio and the characteristic state stress ratio are introduced. The model can describe many characteristics of overconsolidated clays,including stress-strain relationships,strain hardening and softening,stress dilatancy,and stress path dependency. Compared with the Cam-clay model,the model only re-quires one additional soil parameter which is the slope of the Hvorslev envelope. Comparisons with data from triaxial drained compression tests for Fujinomori clay show that the proposed model can rationally describe overconsolidated properties. In addition,the model is also used to predict the stress-strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.
基金supported by the National Natural Science Foundation of China (Grant Nos.50879001,90815024,10872016,11072016)the National Basic Research Program of China ("973" Project) (Grant No.2007CB714103)
文摘The influences of temperature on the mechanical behavior of saturated clays are discussed first. Based on the concept of true strength and the revised calculation method of the potential failure stress ratio, the equation of the critical state stress ratio for saturated clays under different temperatures is deduced. Temperature is introduced as a variable into the UH model （3-dimensional elastoplastic model for overconsolidated clays adopting unified hardening parameter） proposed by Yao et al. and then the UH model considering temperature effects is proposed. By means of the transformed stress method proposed by Yao et al., the proposed model can be applied conveniently to 3-dimensional stress states. The strain-hardening, softening and dilatancy behavior of overconsolidated clays at a given temperature can be described using the proposed model, and the volume change behavior caused by heating can also be predicted. Compared with the modified Cam-clay model, the proposed model requires only one additional parameter to consider the behavior of the decrease of preconsolidation pressure with an increase of temperature. At room temperature, the proposed model can be changed into the original UH model and the modified Cam-clay model for overconsolidated clays and normally consolidated clays, respectively. The considered temperature range here is from the melting point to the boiling point of the pore water （e.g. the experimental temperatures （20℃-95℃） mentioned in this paper are within this range）. Comparison with existing test results shows that the model can reasonably describe the basic mechanical behavior of overconsolidated clays under various temperature paths.
基金Project supported by National Scientific and Technical Research Council of Argentina(PIP 942)National Science and Technology Promotion Agency of Argentina(PICT 2012-2366)
文摘Ceramic supported cerium, manganese and cerium-manganese catalysts were prepared by direct impregnation of aq precursor, and characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Brunauer-Emmett-Teller rn （BET）, temperature programmed reduction （Ha-TPR）, X-ray photoelectron spectroscopy （XPS） acidity measurements and elec conductivity. The catalytic activity was evaluated for volatile organic compounds （VOC） （ethanol, methyl ethyl ketone and tol oxidation. Additionally, catalysts were tested in particulate matter （PM） combustion. The characterization results indicated that Ce was in the form of Ce4＋ and Ce3＋, and Mn existed in the form of Mn4＋ and Mn3＋ on the surface of the Mn/AC sample and in the of Mn4＋ in the Ce/Mn/AC monolith. VOC oxidation results revealed that the Ce/Mn/AC sample showed an excellent perforr compared with ceramic supported CeO2 （Ce/AC） and MnO, （Mn/AC） samples. The PM combustion was also higher on Ce/M monoliths. The enhanced catalytic activity was mainly attributed to the Ce and Mn interaction which enhanced the acidity, cond ity and the reducibility of the oxides.
文摘Adsorption of microcystins (MCs) by carbon nanotubes (CNTs) and clay materials was studied. Compared with various clays tested, CNTs showed a much stronger ability to adsorb MC-RR and LR that were two typical types of microcystins found in China. At initial 21.0 mg/L of MC-RR and 9.5 mg/L of MC-LR in solution, the adsorption amounts of MC-RR and LR by CNTs were 14.8 and 6.7 mg/g that were about five times higher than those by the clay ma-terials of sepiolite, kaolinite and talc, etc. In the presence of CNTs and the bacterial Ralstonia solanacearum that was firstly isolated and used for the biodegradation of MCs by the authors, a remarkable removal of MCs from water were observed. The mechanism was that CNTs could absorb large amount of both MCs and the embedded R. solanacearum so that, even when diluted by a large amount of water, the con-centrations of both organic pollutants and the added bacteria could be largely enhanced on the surface of CNTs where a concerted biodegradation reaction was effectively conducted. This finding could be important for the further development of practical techniques to eliminate MCs from polluted drinking waters.
