In Baotou rare earth tailings ore, the grade of rare earth is close to that of the raw ore nearly. The rare earths are discarded in tailings dam caused by a serious waste of resources. First of all, the decomposition ...In Baotou rare earth tailings ore, the grade of rare earth is close to that of the raw ore nearly. The rare earths are discarded in tailings dam caused by a serious waste of resources. First of all, the decomposition products of bastnaesite-and monazite-mixed rare earth tailings in CaO in reducing atmosphere were studied by means of X-ray diffraction（XRD）. The results show that the normal products are CeO2, Ce2O3, Ca5F（PO4）3, and Ce（0.75）Nd（0.25）O（1.875）, and there are no REPO4 and REFCO3.Secondly, the roasted product was extracted in HCl, and the relationship among roasting time,roasting temperature,CaO addition, and extraction temperature was studied by the quadratic regression-orthogonal analysis. Through analysis, the optimum process conditions of mixed rare earth tailings extracted are obtained as follows： roasting time of 60 min, roasting temperature of 800℃, CaO addition of 30%, extraction temperature of 80℃, and extraction ratio of 99.18%.展开更多
A series of new trialkoxytrialkanoyloxytriphenylene TP（OCnH2n＋1）3（OCOCmH2m＋1）3 （5a-5e） （n =m＋1 =4- 8） discotic liquid crystals were prepared and their mesomorphic properties were investigated using differen...A series of new trialkoxytrialkanoyloxytriphenylene TP（OCnH2n＋1）3（OCOCmH2m＋1）3 （5a-5e） （n =m＋1 =4- 8） discotic liquid crystals were prepared and their mesomorphic properties were investigated using differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. The symmetrical and shorter chain triphenylenes display higher melting points and clearing points, more highly ordered and stable columnar mesophase than the asymmetrical and longer chain triphenylenes respectively.展开更多
Let {Xn; n ≥ 1} be a stationary sequenceof non-negative random variables with heavy tails. Under mixing conditions, we study logarithmic asymptotics for the disp(Sn ＞ nx) ≈ n-αx+1 for appropriate values of x, whe...Let {Xn; n ≥ 1} be a stationary sequenceof non-negative random variables with heavy tails. Under mixing conditions, we study logarithmic asymptotics for the disp(Sn ＞ nx) ≈ n-αx+1 for appropriate values of x, where α is a specific parameter. The related conjecture proposed by Gantert is investigated. As a by-product, the so-called supremum large deviations principle is also studied.展开更多
基金financially supported by the Development Program of National Key Basic Research(No.2012CBA01205)
文摘In Baotou rare earth tailings ore, the grade of rare earth is close to that of the raw ore nearly. The rare earths are discarded in tailings dam caused by a serious waste of resources. First of all, the decomposition products of bastnaesite-and monazite-mixed rare earth tailings in CaO in reducing atmosphere were studied by means of X-ray diffraction（XRD）. The results show that the normal products are CeO2, Ce2O3, Ca5F（PO4）3, and Ce（0.75）Nd（0.25）O（1.875）, and there are no REPO4 and REFCO3.Secondly, the roasted product was extracted in HCl, and the relationship among roasting time,roasting temperature,CaO addition, and extraction temperature was studied by the quadratic regression-orthogonal analysis. Through analysis, the optimum process conditions of mixed rare earth tailings extracted are obtained as follows： roasting time of 60 min, roasting temperature of 800℃, CaO addition of 30%, extraction temperature of 80℃, and extraction ratio of 99.18%.
基金Project supported by the National Natural Science Foundation of China （No. 50473062）, Youth Foundation of Sichuan Province （No. 04ZQ026-044）.
文摘A series of new trialkoxytrialkanoyloxytriphenylene TP（OCnH2n＋1）3（OCOCmH2m＋1）3 （5a-5e） （n =m＋1 =4- 8） discotic liquid crystals were prepared and their mesomorphic properties were investigated using differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. The symmetrical and shorter chain triphenylenes display higher melting points and clearing points, more highly ordered and stable columnar mesophase than the asymmetrical and longer chain triphenylenes respectively.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.10071058,70273029)the Ministry of Education of China.
文摘Let {Xn; n ≥ 1} be a stationary sequenceof non-negative random variables with heavy tails. Under mixing conditions, we study logarithmic asymptotics for the disp(Sn ＞ nx) ≈ n-αx+1 for appropriate values of x, where α is a specific parameter. The related conjecture proposed by Gantert is investigated. As a by-product, the so-called supremum large deviations principle is also studied.
