Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equ...Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1 ) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r 2 ) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.展开更多
We propose a six-parameter exponential-type potential (SPEP), which has been shown to be a shape-invariant potential with a translation of parameters. For this reducible potential, the exact energy levels are obtained...We propose a six-parameter exponential-type potential (SPEP), which has been shown to be a shape-invariant potential with a translation of parameters. For this reducible potential, the exact energy levels are obtained byusing the supersymmetric shape invariance technique. Choosing appropriate parameters, four classes of exponential-typepotentials and their exact energy spectra are reduced from the SPEP and a general energy level formula, respectively.Each class shows the identity except for the different definitions of parameters.展开更多
According to the basic characteristics of the activities of summer monsoon in the South China Sea, a standardized index, sI, has been designed that integrates a dynamic factor (southwesterly component) and a thermodyn...According to the basic characteristics of the activities of summer monsoon in the South China Sea, a standardized index, sI, has been designed that integrates a dynamic factor (southwesterly component) and a thermodynamic factor (OLR) for the indication of summer monsoon in the South China Sea. With the index determined for individual months of June, July and August and the entire summertime from 1975 to 1999, specific months and years are indicated that are either strong or weak in monsoon intensity. The variation is studied for the patterns and sI抯 relationship is revealed with the onset of summer monsoon and the precipitation in Guangdong province and China. The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsoon over the past 25 years. When it has an early (late) onset, the summer monsoon is usually strong (weak). In the strong (weak) monsoon years, precipitation tends to be more (less) in the first raining season of the year but normal or less (normal) in the second, in the province, but it would be more (less) in northeastern China and most parts of the northern China and south of the lower reaches of the Changjiang River and less (more) in the middle and lower reaches of the river, western part of northern China and western China.展开更多
The metastable phase 3c-Fe7S8 with the hexagonal platelet morphology has been prepared by using solvothermal route. The product was characterized by means of X-ray powder diffraction (XRD) and transmission electron mi...The metastable phase 3c-Fe7S8 with the hexagonal platelet morphology has been prepared by using solvothermal route. The product was characterized by means of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS). The experiment results show that the as-prepared Fe7S8 is a metastable phase with the hexagonal platelet morphology.展开更多
In this paper, we define a roll-attaching operation of a hexagonal chain, and prove Gutman's conjecture affirmatively by using the operation. The idea of the proof is also applicable to the results concerning extr...In this paper, we define a roll-attaching operation of a hexagonal chain, and prove Gutman's conjecture affirmatively by using the operation. The idea of the proof is also applicable to the results concerning extremal hexagonal chains for the Hosoya index and Merrifield-Simmons index.展开更多
Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-B...Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.展开更多
基金Project supported by the Open foundation of the State Key Lab of Soil and Sustainable Agriculture, Institute of SoilScience, Chinese Academy of Sciences (No. 0812000037)the Scientific Research Starting Foundation for the ReturnedOverseas Chinese Scholars, Ministry of Education, China (No. 20091001)the National Science and Technology PillarProgram During the 11th Five-Year Period of China (No. 2009BADA6B04)
文摘Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1 ) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r 2 ) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.
文摘We propose a six-parameter exponential-type potential (SPEP), which has been shown to be a shape-invariant potential with a translation of parameters. For this reducible potential, the exact energy levels are obtained byusing the supersymmetric shape invariance technique. Choosing appropriate parameters, four classes of exponential-typepotentials and their exact energy spectra are reduced from the SPEP and a general energy level formula, respectively.Each class shows the identity except for the different definitions of parameters.
基金 Research on the Formation Mechanism and Prediction Theory of Severe Climate Disasters in China (G1998040900(I))
文摘According to the basic characteristics of the activities of summer monsoon in the South China Sea, a standardized index, sI, has been designed that integrates a dynamic factor (southwesterly component) and a thermodynamic factor (OLR) for the indication of summer monsoon in the South China Sea. With the index determined for individual months of June, July and August and the entire summertime from 1975 to 1999, specific months and years are indicated that are either strong or weak in monsoon intensity. The variation is studied for the patterns and sI抯 relationship is revealed with the onset of summer monsoon and the precipitation in Guangdong province and China. The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsoon over the past 25 years. When it has an early (late) onset, the summer monsoon is usually strong (weak). In the strong (weak) monsoon years, precipitation tends to be more (less) in the first raining season of the year but normal or less (normal) in the second, in the province, but it would be more (less) in northeastern China and most parts of the northern China and south of the lower reaches of the Changjiang River and less (more) in the middle and lower reaches of the river, western part of northern China and western China.
基金This work was supported by the National Natural Science Foundation of China.
文摘The metastable phase 3c-Fe7S8 with the hexagonal platelet morphology has been prepared by using solvothermal route. The product was characterized by means of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS). The experiment results show that the as-prepared Fe7S8 is a metastable phase with the hexagonal platelet morphology.
基金the Foundation for University Key Teacher by Education Ministry of China the National Natural Science Foundation of China (Grant No. 19831080) .
文摘In this paper, we define a roll-attaching operation of a hexagonal chain, and prove Gutman's conjecture affirmatively by using the operation. The idea of the proof is also applicable to the results concerning extremal hexagonal chains for the Hosoya index and Merrifield-Simmons index.
文摘Low-energy electron microscopy （LEEM） has been used to study the structure, initial growth orientation, growth progression, and the number of layers of atomically thin hexagonal boron nitride （h-BN） films. The h-BN films are grown on heteroepitaxial Co using chemical vapor deposition （CVD） at low pressure. Our findings from LEEM studies include the growth of monolayer film having two, oppositely oriented, triangular BN domains commensurate with the Co lattice. The growth of h-BN appears to be self-limiting at a monolayer, with thicker domains only appearing in patches, presumably initiated between domain boundaries. Reflectivity measurements of the thicker h-BN films show oscillations resulting from the resonant electron transmission through quantized electronic states of the h-BN films, with the number of minima scaling up with the number of h-BN layers. First principles density functional theory （DFT） calculations show that the positions of oscillations are related to the electronic band structure of h-BN.
