ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ unde...ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ under a pressure of 3.6 GPa. As the pressure increased to 3.9 GPa, the ZrSiO4 formation temperature was reduced to 815 ℃. The formation temperature for coesite was 990 ℃ under 3.9 GPa. The lower formation temperature for ZrSiO4, as compared to that for coesite, provided an experimental evidence that the coesite in the Earth＇s surface usually occurs as inclusions in ZrSiO4.展开更多
High-pressure Raman studies up to 0.84GPa are performed on oleic acid.Spectral analysis indicates that oleic acid undergoes a pressure-induced phase transition in the 0.29–0.36GPa range.Only one high-pressure phase b...High-pressure Raman studies up to 0.84GPa are performed on oleic acid.Spectral analysis indicates that oleic acid undergoes a pressure-induced phase transition in the 0.29–0.36GPa range.Only one high-pressure phase below 0.84GPa is present,in which the polymethylene chains take the ordered all-trans conformation,with the methyl end of the chains exhibiting the ordered chain-end conformation and the olefin group taking the skew-cis-skew’conformation.The conformational characters of the oleic acid molecule show that the high-pressure phase is the same as the low-temperature crystalline𝛾phase.The pressure-induced phase transition is typical of first-order transitions and the transition path during compression is different from that during cooling.展开更多
Photoluminescence measurements have been performed on cubic GaN films with carrier concentration as low as 3×10^(13) cm^(-3).From the temperature and excitation intensity dependence,the emission lines at 3.268,3....Photoluminescence measurements have been performed on cubic GaN films with carrier concentration as low as 3×10^(13) cm^(-3).From the temperature and excitation intensity dependence,the emission lines at 3.268,3.150 and 3.081 eV were assigned to the excitonic,donor-acceptor pair,and free-to-acceptor transitions,respectively.Additionally,we observed two additional emission lines at 2.926 and 2.821 eV,and suggested that they belong to donor-acceptor pair transitions.Furthermore,from the temperature dependence of integral intensities,we confirmed that three donor-acceptor pair transitions(3.150,2.926,and 2.821 eV)are from a common shallow donor to three different acceptors.The excitonic emission at 3.216 eV has a full-width-at-half-maximum value of 41 meV at room temperature,which indicates a good optical quality of our sample.展开更多
A general four-layer structure linear theory for predicting the effects of arbitrarily distributed roughness change on the variations of wind speed and shear stress in the surface layer of 3D and 2D atmospheres was pr...A general four-layer structure linear theory for predicting the effects of arbitrarily distributed roughness change on the variations of wind speed and shear stress in the surface layer of 3D and 2D atmospheres was presented.The results derived by the theory were agreeable to the previous ones.展开更多
基金Supported by the National Natural Science Foundation of China(Nos30370406, 10374022 and 10674034)
文摘ZrSiO4 and coesite were obtained under high-pressure and high-temperature from the nano precursor of a-SiO2 and ZrO2. XRD and Raman measurements indicate that ZrSiO4 was formed at a temperature higher than 920 ℃ under a pressure of 3.6 GPa. As the pressure increased to 3.9 GPa, the ZrSiO4 formation temperature was reduced to 815 ℃. The formation temperature for coesite was 990 ℃ under 3.9 GPa. The lower formation temperature for ZrSiO4, as compared to that for coesite, provided an experimental evidence that the coesite in the Earth＇s surface usually occurs as inclusions in ZrSiO4.
基金Supported by National Natural Science Foundation of China(61376092,61076114,61106108,51172046)Specialized Research Fund for the Doctoral Program of Higher Education(20110071130005)
基金by the Scientific and Technical Development Foundation of Jilin Province of China under Grant No 20080513.
文摘High-pressure Raman studies up to 0.84GPa are performed on oleic acid.Spectral analysis indicates that oleic acid undergoes a pressure-induced phase transition in the 0.29–0.36GPa range.Only one high-pressure phase below 0.84GPa is present,in which the polymethylene chains take the ordered all-trans conformation,with the methyl end of the chains exhibiting the ordered chain-end conformation and the olefin group taking the skew-cis-skew’conformation.The conformational characters of the oleic acid molecule show that the high-pressure phase is the same as the low-temperature crystalline𝛾phase.The pressure-induced phase transition is typical of first-order transitions and the transition path during compression is different from that during cooling.
基金Supported by the National Natural Science Foundation of China under Grant No.69776012.
文摘Photoluminescence measurements have been performed on cubic GaN films with carrier concentration as low as 3×10^(13) cm^(-3).From the temperature and excitation intensity dependence,the emission lines at 3.268,3.150 and 3.081 eV were assigned to the excitonic,donor-acceptor pair,and free-to-acceptor transitions,respectively.Additionally,we observed two additional emission lines at 2.926 and 2.821 eV,and suggested that they belong to donor-acceptor pair transitions.Furthermore,from the temperature dependence of integral intensities,we confirmed that three donor-acceptor pair transitions(3.150,2.926,and 2.821 eV)are from a common shallow donor to three different acceptors.The excitonic emission at 3.216 eV has a full-width-at-half-maximum value of 41 meV at room temperature,which indicates a good optical quality of our sample.
文摘A general four-layer structure linear theory for predicting the effects of arbitrarily distributed roughness change on the variations of wind speed and shear stress in the surface layer of 3D and 2D atmospheres was presented.The results derived by the theory were agreeable to the previous ones.
