国家公园制度是目前世界各国广泛使用的保护地模式。该研究以1990—2019年间的“Web of Science核心合集”相关文献为基础数据源,利用CiteSpace软件对国家公园管理制度的国际研究状况进行知识图谱分析。结果表明,近30 a国际国家公园管...国家公园制度是目前世界各国广泛使用的保护地模式。该研究以1990—2019年间的“Web of Science核心合集”相关文献为基础数据源,利用CiteSpace软件对国家公园管理制度的国际研究状况进行知识图谱分析。结果表明,近30 a国际国家公园管理研究可分为3个阶段,2016年来该领域文献量明显增加,美国、澳大利亚、加拿大等国家和机构研究成果比重较大,中国比重较小;旅游或游憩、保护和社区是近30 a国家公园管理制度研究的三大重要命题,相对应的管理研究对象大致为公民或消费者、国家公园生态系统和周边社区利益相关者,消费者行为或偏好、管理政策或保障、利益分配机制是管理研究的3个关键点;计量模型分析是当前领域研究的重要手段;该领域重要的研究前沿包括保护理念下的国家公园旅游或游憩、社区与国家公园的利益协调和基于游客感知的国家公园游憩服务。该研究从顶层制度建设、资金保障体系、社区协调机制3个方面对中国国家公园发展提出了借鉴建议。展开更多
Low temperature epitaxial growth of ZnO films is achieved on Si(001)substrates by reactive electron beam evap oration.Growth temperature is varied from 125 C to 420 C and the optimum temperature is found between 200&#...Low temperature epitaxial growth of ZnO films is achieved on Si(001)substrates by reactive electron beam evap oration.Growth temperature is varied from 125 C to 420 C and the optimum temperature is found between 200°C and 300 C.X-ray diffraction shows that the ZnO films are highly c-axis oriented and the line width of(002)diffraction peak is significantly smaller than that measured from the ZnO films deposited by magnetron sput tering.The combined photoluminescence and photoluminescence excitation(PLE)spectroscopic measurements demonstrate the sharp band-absorption edge and exciton absorption in the ZnO films.PLE has also revealed that the absorption characteristic near the band edge is remarkably improved with the increase of oxygen content in the ZnO films,although x-ray diffraction analysis shows that the crystalline structure of ZnO films grown under different oxygen pressures remains unchanged.展开更多
PbSe films were grown on(111)-oriented BaF_(2)substrates by using molecular beam epitaxy.High resolution x-ray diffraction characterization showed good crystalline quality of PbSe films.Both longitudinal optical phono...PbSe films were grown on(111)-oriented BaF_(2)substrates by using molecular beam epitaxy.High resolution x-ray diffraction characterization showed good crystalline quality of PbSe films.Both longitudinal optical phonon at 135cm^(-1)and transverse optical phonon at 47.6cm-1 were observed by Raman scattering measurements.The Raman tensor calculation demonstrates that both transverse-optical and longitudinal-optical(LO)phonons in PbSe crystal are Raman active on(111)-oriented surface,Furthermore,2LO phonon at about 270cm^(-1)and polaron at about 800cm^(-1)in PbSe,were also observed.The observed Raman frequencies are in good agreement with theoretical calculations using point ion model.展开更多
A SiGe/Si epilayer with a linear-step-graded buffer was grown by ultrahigh vacuum chemical vapor deposition technique at a relatively high growth temperature(780℃)and a relatively high growth rate.Almost linear Ge co...A SiGe/Si epilayer with a linear-step-graded buffer was grown by ultrahigh vacuum chemical vapor deposition technique at a relatively high growth temperature(780℃)and a relatively high growth rate.Almost linear Ge content variation was realized in the buffer layer due to the Ge segregation to the growing surface during epitaxial growth.Double crystal x-ray diffraction and Raman spectroscopy show that the upper layer is fully relaxed.However,the measured results show that the density of dislocation in the composition graded structure is much lower than that in single-step epilayer structures.展开更多
Optical studies of the CdTe/CdMnTe multiple quantum well structures with diluted manganese in barriers are presented.The combined measurements of photoluminescence and photoluminescence excitation allowed direct obser...Optical studies of the CdTe/CdMnTe multiple quantum well structures with diluted manganese in barriers are presented.The combined measurements of photoluminescence and photoluminescence excitation allowed direct observation of the binding energies of n=l heavy-and light-hole free excitons.The quantitative approach of variation of exciton binding energies with well width and barrier potential height is given.The calculated and measured exciton binding energies are in good agreement.Photoluminescence studies also show exciton-acoustic phonon scattering dominates the broadening of the exciton line width up to T=50 K,while T>50 K longitudinal-optical phonon scattering contributes to the line width broadening significantly.展开更多
文摘国家公园制度是目前世界各国广泛使用的保护地模式。该研究以1990—2019年间的“Web of Science核心合集”相关文献为基础数据源,利用CiteSpace软件对国家公园管理制度的国际研究状况进行知识图谱分析。结果表明,近30 a国际国家公园管理研究可分为3个阶段,2016年来该领域文献量明显增加,美国、澳大利亚、加拿大等国家和机构研究成果比重较大,中国比重较小;旅游或游憩、保护和社区是近30 a国家公园管理制度研究的三大重要命题,相对应的管理研究对象大致为公民或消费者、国家公园生态系统和周边社区利益相关者,消费者行为或偏好、管理政策或保障、利益分配机制是管理研究的3个关键点;计量模型分析是当前领域研究的重要手段;该领域重要的研究前沿包括保护理念下的国家公园旅游或游憩、社区与国家公园的利益协调和基于游客感知的国家公园游憩服务。该研究从顶层制度建设、资金保障体系、社区协调机制3个方面对中国国家公园发展提出了借鉴建议。
基金Supported by the National Natural Science Foundation of China under Grant No.69606006Natural Science Fund of Zhejiang Province.
文摘Low temperature epitaxial growth of ZnO films is achieved on Si(001)substrates by reactive electron beam evap oration.Growth temperature is varied from 125 C to 420 C and the optimum temperature is found between 200°C and 300 C.X-ray diffraction shows that the ZnO films are highly c-axis oriented and the line width of(002)diffraction peak is significantly smaller than that measured from the ZnO films deposited by magnetron sput tering.The combined photoluminescence and photoluminescence excitation(PLE)spectroscopic measurements demonstrate the sharp band-absorption edge and exciton absorption in the ZnO films.PLE has also revealed that the absorption characteristic near the band edge is remarkably improved with the increase of oxygen content in the ZnO films,although x-ray diffraction analysis shows that the crystalline structure of ZnO films grown under different oxygen pressures remains unchanged.
基金Supported in part by the National Natural Science Foundation of China under Grant No.69606006Oklahoma Center for the Advancement of Science and Technology(OCAST#AR6-054).
文摘PbSe films were grown on(111)-oriented BaF_(2)substrates by using molecular beam epitaxy.High resolution x-ray diffraction characterization showed good crystalline quality of PbSe films.Both longitudinal optical phonon at 135cm^(-1)and transverse optical phonon at 47.6cm-1 were observed by Raman scattering measurements.The Raman tensor calculation demonstrates that both transverse-optical and longitudinal-optical(LO)phonons in PbSe crystal are Raman active on(111)-oriented surface,Furthermore,2LO phonon at about 270cm^(-1)and polaron at about 800cm^(-1)in PbSe,were also observed.The observed Raman frequencies are in good agreement with theoretical calculations using point ion model.
基金Supported by the National Natural Science Foundation of China under Grant No.69686002the‘Talents Across the Century’of Education Ministry of Chinathe Natural Science Fund of Zhejiang Province.
文摘A SiGe/Si epilayer with a linear-step-graded buffer was grown by ultrahigh vacuum chemical vapor deposition technique at a relatively high growth temperature(780℃)and a relatively high growth rate.Almost linear Ge content variation was realized in the buffer layer due to the Ge segregation to the growing surface during epitaxial growth.Double crystal x-ray diffraction and Raman spectroscopy show that the upper layer is fully relaxed.However,the measured results show that the density of dislocation in the composition graded structure is much lower than that in single-step epilayer structures.
基金Supported in part by the National Natural Science Foundation of China under Grant No.69606006the Office of State Education Commission.
文摘Optical studies of the CdTe/CdMnTe multiple quantum well structures with diluted manganese in barriers are presented.The combined measurements of photoluminescence and photoluminescence excitation allowed direct observation of the binding energies of n=l heavy-and light-hole free excitons.The quantitative approach of variation of exciton binding energies with well width and barrier potential height is given.The calculated and measured exciton binding energies are in good agreement.Photoluminescence studies also show exciton-acoustic phonon scattering dominates the broadening of the exciton line width up to T=50 K,while T>50 K longitudinal-optical phonon scattering contributes to the line width broadening significantly.
