Soil erosion monitoring and its implication in a limestone land suffering from rocky desertification in the Huajiang Canyon, Guizhou, Southwest China     

Jian Peng  Yue Qing Xu  Ren Zhang  Kang Ning Xiong  An Jun Lan 《Environmental Earth Sciences》2013,69(3):831-841

Over the past decades, the vast limestone mountain areas in southwestern China have suffered greatly from karst rocky desertification (KRD), which is a unique type of desertification caused by irrational land-use practices and has drawn increasing attention of international academic community. Characterizing soil erosion in this region is the key to understanding the escalating KRD problem and finding solution to it. The authors applied leveling method to study soil erosion process in the Huajiang Karst Canyon area between 1999 and 2003, and tried to relate it to KRD expansion. The monitoring data indicate that soil in the study area was losing at an alarming rate, which is much higher than soil formation rate and has already resulted in severe KRD problem. Soil loss under different land-use conditions varied greatly during the monitoring period. The highest soil erosion rate occurred in bare and newly abandoned cropland, followed by sparse grass land, forest land, and dense grass land. In addition, soil erosion could be significantly different under different micro-topographic conditions. Because soil erosion rate in the studied karst mountain areas is surprisingly high, it is urgent to take quick actions to fight against the ongoing KRD problems in Southwest China before an irreversible situation occurs. However, the traditional way to combat KRD by abandoning current cropland needs to be carefully reconsidered, since a bare newly abandoned cropland may suffer more from rapid soil loss than before.  相似文献   

Fermi gamma-ray and multi-wave band emission from TeV active galactic nuclei     

Dingrong Xiong  Haojing Zhang  Xiong Zhang  Yonggang Zheng  Wenguang Liu  Lisheng Mao  Bangrong Huang  Ting Kang  Yongjuan Cha  Fei Guo 《Astrophysics and Space Science》2013,343(1):345-360

Using γ-ray data detected by Fermi Large Area Telescope (LAT) and multi-wave band data for 40 TeV active galactic nuclei (AGNs), we have studied the correlations between flux densities (F _R, F _IR, F _O, F _X and F _γ ) in the radio, infrared, optical, X-ray and γ-ray wave bands. Our results are the following: (1) For TeV HSP BL Lacertae objects (THBLs), there are strong correlations between F _γ and F _R and between F _γ and F _IR in all states (average/high/low); (2) The TeV radio galaxies (TRGs) deviate from the area occupied by THBLs; (3) The TeV flat-spectrum radio quasars (TFSRQs) have much stronger γ-ray emission than THBLs; (4) For THBLs, there are weak correlations between F _γ and F _X in all states as well as between F _γ and F _O in both average and high states, and a strong correlation between F _γ and F _O in the low state; (5) For THBLs, there are strong correlations between F _O and F _R in both low and average states as well as between F _O and F _IR in all states and between F _IR and F _R in all states, but no strong correlations among other bands are found. From these results, we suggest that for THBLs, the synchrotron self-Compton radiation (SSC) is the main mechanism of high energy γ-ray emission and the inverse Compton scattering of circum-nuclear dust is likely to be a important complementary mechanism. Compared with THBLs, TRGs and TFSRQs may have a different origin of high energy γ-ray.  相似文献   

The Black Hole Masses and Radio Characteristics of Radio Quasars     

Xiong Ding-rong  Zhang XiongZheng Yong-gang  Huang Bang-rongMao Li-sheng  Liu Wen-guang 《Chinese Astronomy and Astrophysics》2013

In this paper, we collect the redshift, bolometric luminosity, the full- width at half maximum of the H_β emission line, the monochromatic luminosity at 5100 Å and the radio loudness for the sample of 117 quasars, including 20 radio-quiet quasars (RQQs) and 97 radio-loud quasars (RLQs). With the reverberation mapping method we calculate the black hole mass and Eddington ratio for this sample, as well as the radio luminosity from the total 5 GHz ?ux density. By analyzing the correlations among them, we obtain the following conclusions: (1) The black hole mass has weak correlations with the bolometric luminosity, radio loudness and radio luminosity for the RQQs, and has strong correlations with the bolometric luminosity, radio loudness and radio luminosity for the RLQs; (2) For the RQQs, the bolometric luminosity has weak correlations with the radio luminosity and 5 100 Å monochromatic luminosity, and for the RLQs, the bolometric luminosity has strong correlations with the radio luminosity and 5 100 Å monochromatic luminosity; (3) The RQQs and RLQs differ in the distributions of the black hole mass, emission line width and Eddington ratio. Based on these results, we suggest: the difference of emission line width between RQQs and RLQs is probably caused by the difference of black hole mass; the fundamental difference between RQQs and RLQs is caused by the difference of their intrinsic physical nature; the black hole mass, black hole spin, Eddington ratio, and host galaxy morphology are the important parameters to explain the origin of radio loudness and the double-peaked distribution; and the radio jet is closely related with the accretion rate of disk.  相似文献   

A Theoretical Probe for Excitation Mechanisms of Solar-like and Mira-like Oscillations of Stars     

Xiong Da-run  Deng Li-cai 《Chinese Astronomy and Astrophysics》2013

The linear stability analysis of the radial and non-radial oscillations for the evolutionary model of a star with the mass of 0.6∼3 M8 has been per- formed by using the nonlocal and time-dependent convection theory. The results show that the unstable low-temperature stars on the right side of the instabil- ity strip in the HR diagram can be divided into two groups. One is of the stars of solar-like oscillations, composed of the main-sequence dwarfs, subgiants, and the red giants with low- and intermediate-luminosity, which are unstable in the intermediate- and high-order (nr ≥ 12) p-modes, but stable in the low- order (nr ≤ 5) p-modes. Another is of the Mira-like stars, composed of the luminous red giants and AGB stars, which are just contrary to the solar-like stars, unstable in the low-order (nr ≤ 5) p-modes, but stable in the intermediate- and high-order (nr ≥ 12) p-modes. On the red edge of Cepheid (δ Scuti) insta- bility strip, the oscillations of solar-like and Mira-like stars can be explained uniformly by the coupling between convection and oscillations (CCO). For the low-temperature stars on the right side of the instability strip, the CCO is the dominant excitation and damping mechanism for the low- and intermediate-order p-modes, and the stochastic excitation of turbulence becomes important only for the high-order p-modes of solar-like oscillations.  相似文献   

中条山铜矿峪铜矿区火山岩的地球化学特征及构造背景   总被引：1，自引：0，他引：1  

周雄 《四川地质学报》2013,(2):240-243,246

对铜矿峪火山岩进行常量元素、微量元素及稀土元素研究表明,SiO2质量分数为47.22%～76.00%,平均66.21%,Al2O3含量为11.03%～20.03%,属铝饱和类型。通过常量元素投点图分析,属一种高钾系列火山岩。稀土元素特征表明,火山岩的源岩浆来源于上地慢。在微量元素的球粒陨石标准化图上,表现为不相容元素Rb、K、Ba、Th的高度富集,同时,具有Sr、Tb和Nb、Ti的亏损,其总体配分型式类似于板内拉斑玄武岩。  相似文献   

Acute toxicity of organochlorine insecticide endosulfan to the giant freshwater prawn Macrobrochium rosenbergii     

戴习林  熊昭娣  谢剑  丁福江 《中国海洋湖沼学报》2014,32(1):111-119

Endosulfan, an organochlorine pesticide, is highly toxic and effective at controlling pests in agriculture, horticulture, and public health programs. In this study, static bioassays were used to evaluate the toxicity of endosulfan to freshwater prawns( Macrobrachium rosenbergii) of various lengths(1.5±0.03,4±0.08, and 7±0.06 cm). Additionally, the activities of peroxidase(POD), acid phosphatase(ACP),alkaline phosphatase, acetylcholinesterase(AChE), and Na + /K +-ATPase were analyzed to refl ect the effects of endosulfan exposure. The 96 h LC 50 of endosulfan for prawns 1.5, 4, and 7 cm long were 1.86, 4.53,and 6.09μg/L, respectively, improved tolerance to endosulfan with growth. The POD activities of test organisms exposed to low concentrations of endosulfan were inhibited, indicating the presence of oxygen damaged tissue. Moreover, a notable decrease in AChE activity was observed due to overstimulation of neurotransmission, which might result in abnormal behavior. The effect caused by endosulfan on phosphatase production in the hepatopancreas of prawns 1.5, 4, and 7 cm long was different because the ability of nonspecifi c immune regulation increased with growth. The 96 h LC 50 values obtained in this study could be used in the formulation of water-quality criteria in China. Moreover, the changes in enzymes activities of M. rosenbergii under stress of endosulfan could be applied in the establishment of early warning indicators for bio-safety.  相似文献   

Research Progress in China on the Tropical Atmospheric Intraseasonal Oscillation          下载免费PDF全文

LI Chongyin  LING Jian  SONG Jie  PAN Jing  TIAN Hu  CHEN Xiong 《Acta Meteorologica Sinica》2014,28(5):671-692

Tropical intraseasonal oscillation (including the Madden-Julian oscillation) is an important element of the atmospheric circulation system. The activities and anomalies of tropical intraseasonal oscillations affect weather and climate both inside and outside the tropical region. The study of these phenomena therefore represents one of the frontiers of atmospheric sciences. This review aims to synthesize and summarize studies of intraseasonal oscillation (ISO) by Chinese scientists within the last 5-10 years. We focus particularly on ISO's mechanisms, its numerical simulations (especially the impacts of diabatic heating profiles), relationships and interactions with ENSO (especially over the western Pacific), impacts on tropical cyclone genesis and tracks over the northwestern Pacific, and influences on the onset and activity of the South and East Asian monsoons (especially rainfall over China). Among these, focuses of ongoing research and unresolved issues related to ISO are also discussed.  相似文献   

2012年初欧洲严寒天气成因的分析   总被引：1，自引：1，他引：0  

陈雄  李崇银  谭言科  郭文华 《气象科学》2014,34(2):213-221

2012年初欧洲遭受了严重的低温严寒天气。分析表明:从对流层低层到高层持续的大气环流异常与此次严寒天气有着密切的联系,1、2月出现的北极涛动(AO)的强负异常是造成此次欧洲严寒天气的主要原因。AO负异常导致北大西洋副高异常偏强、偏东和偏北,使得暖湿空气沿副高北侧流向北极地区,极大减弱了欧洲暖湿空气的来源;同时使乌拉尔山高压强度偏强,位置偏西偏北,有利于上游偏强、偏北的大西洋副高的维持,并加强了极区冷空气南下西进,造成了南欧地区的严寒天气。AO负异常引起的地中海低压槽的加深,为北方冷空气的南下创造了有利条件,也使冷暖空气在地中海北岸交汇,从而导致亚平宁半岛和巴尔干半岛的暴雪天气。虽然La Nia事件对这次严寒天气也有一定的贡献,但AO负异常对这次严寒天气的作用远远大于La Nia事件的作用。  相似文献   

计算机兵棋棋盘中坐标快速转换方法研究     

张欣  武志强  游雄  张寅宝 《测绘软科学研究》2014,(4):17-20

兵棋是对作战过程进行逻辑推演研究和评估的重要工具,是现代作战模拟的一种重要方法和手段。兵棋的三大要素包括棋盘、棋子和规则,棋盘的经典样式就是六角格网兵棋棋盘,计算机兵棋中也常采用六角格网兵棋棋盘描述战场地形环境。推演过程中通常涉及到大量的坐标转换,因此坐标转换效率对于推演效率具有重要影响。针对经纬度坐标和六角格网编码的转换,提出了直接转换和间接转换两种坐标转换方法,分析了各自的基本转换原理,并给出了坐标转换公式,最后通过实验对两种方法的转换效率进行了分析,证实间接坐标转换法具有更高的转换效率。  相似文献   

Assessment of theoretical approaches to derivation of internal solitary wave parameters from multi-satellite images near the Dongsha Atoll of the South China Sea     

Huarong Xie  Qing Xu  Quanan Zheng  Xuejun Xiong  Xiaomin Ye  Yongcun Cheng 《海洋学报(英文版)》2022,41(6):137-145

This study assesses the accuracy and the applicability of the Korteweg-de Vries(KdV) and the nonlinear Schr?dinger(NLS) equation solutions to derivation of dynamic parameters of internal solitary waves(ISWs) from satellite images. Visible band images taken by five satellite sensors with spatial resolutions from 5 m to 250 m near the Dongsha Atoll of the northern South China Sea(NSCS) are used as a baseline. From the baseline, the amplitudes of ISWs occurring from July 10 to 13, 2017 are estimate...  相似文献