For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocit...For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocity of the light pulse can be changed from subluminal to superluminal. The effects of the field intensity and the two-upper level splitting on the group velocity are also shown. At last, an analytical expression for the group velocity is given in the case of a weak field.展开更多
Heavy metal determination was carried out by applying the solid phase extraction （SPE） method in batch mode followed by atomic absorption spectroscopy （AAS） and inductively coupled plasma atomic emission spectrosc...Heavy metal determination was carried out by applying the solid phase extraction （SPE） method in batch mode followed by atomic absorption spectroscopy （AAS） and inductively coupled plasma atomic emission spectrosco py （ICP-AES） from aqueous solutions using Ghezeljeh montmorillonite nanoclay as a new natural adsorbent. The Ghezeljeh clay is characterized by using Fourier Transform Infrared （FT-IR） Spectroscopy, Scanning Electron Mi- croscopy-Energy Dispersive Spectrometry （SEM-EDS） and X-ray Diffractometry （XRD） and X-ray Fluorescence （XRF）. The results of XRD and FT-IR of nanoclay confirm that montmorillonite is the dominant mineral phase. Based on SEM images of Ghezeljeh clay, it can be seen that the distance between the plates is Nano. The effects of varying parameters such as initial concentration of metal ions, pH and type of buffer solutions, amount of ad- sorbent, contact time, and temperature on the adsorption process were examined. The effect of various interfer- ing ions was studied. The adsorption data correlated with Freundlich, Langmuir, Dubinin-Radushkevich （D-R）, and Temkin isotherms. The Langmuir and Freundlich isotherms showed the best fit to the equilibrium data for Hg（II）, but the equilibrium nature of Cu（ll） adsorption has been described by the Langmuir isotherm. The kinetic data were described with pseudo-first-order, pseudo-second-order and double-exponential models, The adsorp- tion process follows a pseudo-second-order reaction scheme, Calculation of AGσ, △Hσ and ASσ showed that tilenature of Hg（II） ion sorption onto the Ghezeljeh nanoclay was endothermic and was favored at higher temper- attire, and the nature of Cu（II） ion sorption was exothermic and was favored at lower temperature,展开更多
基金The project supported by National Natural Science Foundation of China under Grant No. 10547108
文摘For a V-type three-level atomic system with two closely spaced upper levels, we investigate the light pulse propagation properties with only one laser field. Due to spontaneously generated coherence, the group velocity of the light pulse can be changed from subluminal to superluminal. The effects of the field intensity and the two-upper level splitting on the group velocity are also shown. At last, an analytical expression for the group velocity is given in the case of a weak field.
基金financial support for this work by the Imam Khomeini International University (IKIU)Mines and Mining Industries Development and Renovation Organization of Iran (IMIDRO)
文摘Heavy metal determination was carried out by applying the solid phase extraction （SPE） method in batch mode followed by atomic absorption spectroscopy （AAS） and inductively coupled plasma atomic emission spectrosco py （ICP-AES） from aqueous solutions using Ghezeljeh montmorillonite nanoclay as a new natural adsorbent. The Ghezeljeh clay is characterized by using Fourier Transform Infrared （FT-IR） Spectroscopy, Scanning Electron Mi- croscopy-Energy Dispersive Spectrometry （SEM-EDS） and X-ray Diffractometry （XRD） and X-ray Fluorescence （XRF）. The results of XRD and FT-IR of nanoclay confirm that montmorillonite is the dominant mineral phase. Based on SEM images of Ghezeljeh clay, it can be seen that the distance between the plates is Nano. The effects of varying parameters such as initial concentration of metal ions, pH and type of buffer solutions, amount of ad- sorbent, contact time, and temperature on the adsorption process were examined. The effect of various interfer- ing ions was studied. The adsorption data correlated with Freundlich, Langmuir, Dubinin-Radushkevich （D-R）, and Temkin isotherms. The Langmuir and Freundlich isotherms showed the best fit to the equilibrium data for Hg（II）, but the equilibrium nature of Cu（ll） adsorption has been described by the Langmuir isotherm. The kinetic data were described with pseudo-first-order, pseudo-second-order and double-exponential models, The adsorp- tion process follows a pseudo-second-order reaction scheme, Calculation of AGσ, △Hσ and ASσ showed that tilenature of Hg（II） ion sorption onto the Ghezeljeh nanoclay was endothermic and was favored at higher temper- attire, and the nature of Cu（II） ion sorption was exothermic and was favored at lower temperature,
