Luminescent Properties and Decay Characteristics of CaS: Mn2 + Phosphor     

Cao Lin  Li Dianchao 《世界地质(英文版)》2000,3(2)

CaS:Mn2 + has been synthesized by a new sulfurizing flux method, and the phosphors prepared in this way is relatively stable in water. The fluorescent spectra of CaS host and CaS: Mn2 + have been measured at room temperature. The luminescent centers formed by O2 - ions may be responsible for the host' s blue - green emission. The complete disappearance ofthis emission in CaS: Mn2 + system confirms that there exists efficient energy transfer from the host to the Mn2 + centers.The decay characteristics have been performed. The photoluminescence decay of CaS: Mn2 + consists of slow and fast components due to the single and paired Mn2 + centers, respectively.  相似文献   

Spectral Properties of Black Holes in Gamma Rays     

Sandip Kumar Chakrabarti 《Astrophysics and Space Science》2005,297(1-4):131-142

Black holes are the most compact objects in the universe. Therefore, matter accreting onto them is likely to radiate photons of energy comparable to very high gravitational potential energy. We discuss the nature of the emitted radiation in X-rays and gamma-rays from black hole candidates. We present theoretical solutions, which comprise both Keplerian and sub-Keplerian components and suggest that shocks in accretion and outflows may play a major role in producing these spectra.  相似文献   

Statistical Modeling with a Hidden Markov Tree and High-resolution Interpolation for Spaceborne Radar Reflectivity in the Wavelet Domain     

Leilei KOU  Yinfeng JIANG  Aijun CHEN  Zhenhui WANG 《大气科学进展》2020,37(12):1359-1374

With the increasing availability of precipitation radar data from space, enhancement of the resolution of spaceborne precipitation observations is important, particularly for hazard prediction and climate modeling at local scales relevant to extreme precipitation intensities and gradients. In this paper, the statistical characteristics of radar precipitation reflectivity data are studied and modeled using a hidden Markov tree (HMT) in the wavelet domain. Then, a high-resolution interpolation algorithm is proposed for spaceborne radar reflectivity using the HMT model as prior information. Owing to the small and transient storm elements embedded in the larger and slowly varying elements, the radar precipitation data exhibit distinct multiscale statistical properties, including a non-Gaussian structure and scale-to-scale dependency. An HMT model can capture well the statistical properties of radar precipitation, where the wavelet coefficients in each sub-band are characterized as a Gaussian mixture model (GMM), and the wavelet coefficients from the coarse scale to fine scale are described using a multiscale Markov process. The state probabilities of the GMM are determined using the expectation maximization method, and other parameters, for instance, the variance decay parameters in the HMT model are learned and estimated from high-resolution ground radar reflectivity images. Using the prior model, the wavelet coefficients at finer scales are estimated using local Wiener filtering. The interpolation algorithm is validated using data from the precipitation radar onboard the Tropical Rainfall Measurement Mission satellite, and the reconstructed results are found to be able to enhance the spatial resolution while optimally reproducing the local extremes and gradients.  相似文献   

Optical,Radiative and Chemical Characteristics of Aerosol in Changsha City,Central China     

Xiaoyan WU  Jinyuan XIN  Wenyu ZHANG  Chongshui GONG  Yining MA  Yongjing MA  Tianxue WEN  Zirui LIU  Shili TIAN  Yuesi WANG  Fangkun WU 《大气科学进展》2020,37(12):1310-1322

Industrial pollution has a significant effect on aerosol properties in Changsha City, a typical city of central China. Therefore, year-round measurements of aerosol optical, radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed. During the observation period, the energy structure was continuously optimized, which was characterized by the reduction of coal combustion. The aerosol properties have obvious seasonal variations. The seasonal average aerosol optical depth (AOD) at 500 nm ranged from 0.49 to 1.00, single scattering albedo (SSA) ranged from 0.93 to 0.97, and aerosol radiative forcing at the top of the atmosphere (TOA) ranged from ?24.0 to 3.8 W m^?2. The chemical components also showed seasonal variations. Meanwhile, the scattering aerosol, such as organic carbon, SO₄^2?, NO₃^?, and NH₄⁺ showed a decrease, and elemental carbon increased. Compared with observation in winter 2012, AOD and TOA decreased by 0.14 and ?1.49 W m^?2 in winter 2014. The scattering components, SO₄^2?, NO₃^? and NH₄⁺, decreased by 12.8 μg m^?3 (56.8%), 9.2 μg m^?3 (48.8%) and 6.4 μg m^?3 (45.2%), respectively. The atmospheric visibility and pollution diffusion conditions improved. The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol. The results indicate that Changsha is an industrial city with strong scattering aerosol. The energy structure optimization had a marked effect on controlling pollution, especially in winter (strong scattering aerosol).  相似文献   

Effects of Aerosols on Fogs Observed in the North China Plain          下载免费PDF全文

ZHANG Jia-Wei  XUE Hui-Wen  DENG Zhao-Ze  ZHAO Chun-Sheng  ZHANG Qing-Hong 《大气和海洋科学快报》2013,6(2):79-83

fog, microphysical properties, aerosol indirect effect, visibility  相似文献   

固化滨海盐渍土路用性能的室内试验与现场测试     

王沛  柴寿喜 《工程地质学报》2011,19(3):440-446

渤海湾西海岸带地区的路堤多为填方型式,且以滨海盐渍土为主要填料.以滨海盐渍土填筑路堤,须解决土的盐胀、溶陷和吸湿软化带来的强度下降和稳定性降低问题,以进行土的改性或固化处理.为降低工程费用,固化材料应以常规的无机材料为主,辅助少量的高分子材料.为研究滨海盐渍土填筑路堤的力学性能,完成了石灰固化土和石灰+SH固土剂固化土...  相似文献   

Amino Acid Composition and Functional Properties of Giant Red Sea Cucumber （Parasfichopus californicus） Collagen Hydrolysates     

LIU Zunying  SU Yicheng  ZENG Mingyong 《青岛海洋大学学报(英文版)》2011,(1):80-84

  相似文献   

Mollisols properties and changes in Ukraine and China   总被引：4，自引：2，他引：2  

Yuri S KRAVCHENKO  Richard M CRUSE 《中国地理科学(英文版)》2011,21(3):257-266

Soils are the foundation of civilizations and the basis for human food production.Mollisols in Ukraine and Northeast China are two out of the four major Mollisol regions in the world.The natural areas from which Mollisols developed are the prairies and steppes that experience temperate and freezing conditions.This review paper introduces the general climate,vegetation,and topography of Mollisols regions in Ukraine and Northeast China,analyzes their properties,including soil texture,soil organic matter content,soil bulk density,pH,cation exchange capacity and other chemical properties,and compares the property changes and management practices of Mollisols in relation to sustainable grain production.  相似文献   

不同精制方法对鱿鱼（Ommastrephes bartrami）墨黑色素的微观形态、光谱特征及金属元素的影响     

宋茹  李仁伟  俞群娣  邓尚贵 《海洋与湖沼》2011,42(6):839-843

采用扫描电镜、光谱分析和元素分析法,进行了胃蛋白酶水解法、高速离心法和酸水解法精制的鱿鱼墨黑色素颗粒形态、紫外可见光谱、红外光谱及金属元素含量的研究。结果表明,酸水解法破坏了鱿鱼墨黑色素的颗粒结构;三种不同精制方法所得的鱿鱼墨黑色素在220nm附近均有强吸收。胃蛋白酶水解和酸水解法有效切除黑色素的氨基基团,但酸水解法下...  相似文献   

Geotechnical characteristics of deep-sea sediments from the North Atlantic and North Pacific oceans     

Horst G. Brandes 《Ocean Engineering》2011,38(7):835-848

Geotechnical properties from a series of deep-sea sites in the North Atlantic and North Pacific oceans are examined to evaluate overall trends and to compare with similar fine-grained soils found on land. The study areas encompass a range of sedimentary environments dominated by combinations of turbidite and pelagic deposits. Carbonate content in excess of 20% is seen to result in a decrease in liquid limit and compressibility. Vertical profiles of geotechnical properties in the North Pacific show broader changes in down-core geotechnical properties compared to the North Atlantic and reflect the effects of long-term climatic changes and seafloor spreading. Sediments in the North Atlantic indicate significant differences depending on location, which is attributed to variability in turbidite deposition, water depth, distance from sediment sources, and the effects of bottom currents. Compared to equivalent fine-grained soils on land, deep-sea sediments are generally softer, more compressible and have higher friction angles at comparable Atterberg limits. Deeper and older sediments in the North Pacific are characterized by unusually large plastic limits, which are attributed to the presence of volcanic fractions. Empirical relationships for compression index and friction angle are discussed for sediments from both oceans.  相似文献