渭河下游"03"洪水对河道冲淤及河势变化的影响

2003年汛期渭河下游出现了自1981年以来的较大洪水,成阳、临潼、华县洪峰流量分别为5340、5100、3570 m3/s,其洪峰水位达历史最高,洪水过程首尾相接,六次洪水过程造成干支流堤防决口11处,洪灾损失极其严重.着重分析了"03"洪水对渭河下游河道冲淤及河势变化带来的影响.     

Carbon isotopic composition of modern soil and paleosol as a response to vegetation change on the Chinese Loess Plateau

The relationship between the carbon isotopic composition of paleosols and pale-ovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of the carbon isotopic composition of modern soil in this area. A preliminary investigation of the carbon isotopic compositions of the modern soil and the loess/paleosol sequence on the Loess Plateau shows that the carbon isotopic composition of modern soil is consistent with the distribution of modern plants on the Loess Plateau, where the ecosystem is dominated by a mixture of C4 and C3 plants. Comparing the δ13C values of modern soil and loess-paleosol sequences from the Xunyi profile, we conclude that C3 plants dominated the landscape during loess sediment stages, while C4 plants expanded during paleosol stages.     

Nitrogen isotopic geochemical characteristics of crude oils in several basins of China

Nitrogen occupies a high content in crust and in atmospheric circle. It is one of the main elements in organism and an important element in sedimentary circle. Although nitrogen is little in crude oil, to a cer-tain degree, it influences the physical and chemical properties of oil, such as viscosity and density[1]. In reservoir the nitrogen-bearing compounds can form ion bonds or hydrogen bonds with substances on rock and form van der Vaals’ force among moleculae so they affect and alter the …     

Impacts of land-use and climate changes on ecosystem productivity and carbon cycle in the cropping-grazing transitional zone in China

Terrestrial ecosystems are both a carbon source and sink, therefore play an important role in the global carbon cycle that act as a link of interactions between human activities and climate changes[1,2]. Climate change impacts ecosystem carbon cycle through af- fecting biological processes, e.g. plant photosynthesis, respiration, and soil carbon decomposition. Land-use change directly modifies the distribution and structure of terrestrial ecosystems and hence the carbon storage and fluxes. Usi…     

Photometric studies of three Be stars

From 1978 December to 1979 May, we made spectrographic observations of φPer, ζTau and κDra using our Schmidt cassegrain grating spectrograph. Values of electron density, rotational speed and variation have been obtained and a comparison between ζTau and the supergiant βOri carried out. We found that, over our observed period, θPer showed clear shell activities, ζTau was in a relatively calm phase, its shell slowly expanding, while κDra had all the signs of a “classical” Be star.     

Cross-correlation between WMAP and 2MASS: non-Gaussianity induced by the SZ effect

We study the non-Gaussianity induced by the Sunyaev–Zel'dovich (SZ) effect in cosmic microwave background (CMB) fluctuation maps. If a CMB map is contaminated by the SZ effect of galaxies or galaxy clusters, the CMB maps should have similar non-Gaussian features to the galaxy and cluster fields. Using the WMAP data and 2MASS galaxy catalogue, we show that the non-Gaussianity of the 2MASS galaxies is imprinted on WMAP maps. The signature of non-Gaussianity can be seen with the fourth-order cross-correlation between the wavelet variables of the WMAP maps and 2MASS clusters. The intensity of the fourth-order non-Gaussian features is found to be consistent with the contamination of the SZ effect of 2MASS galaxies. We also show that this non-Gaussianity can not be seen by the high-order autocorrelation of the WMAP . This is because the SZ signals in the autocorrelations of the WMAP data generally are weaker than the WMAP –2MASS cross-correlations by a factor f ², which is the ratio between the powers of the SZ-effect map and the CMB fluctuations on the scale considered. Therefore, the ratio of high-order autocorrelations of CMB maps to cross-correlations of the CMB maps and galaxy field would be effective to constrain the powers of the SZ effect on various scales.     

High-Spatial-Resolution Imaging Combining High-Order Adaptive Optics,Frame Selection,and Speckle Masking Reconstruction

We present, for the first time, high-spatial-resolution observations combining high-order adaptive optics (AO), frame selection, and post-facto image correction via speckle masking. The data analysis is based on observations of solar active region NOAA 10486 taken with the Dunn Solar Telescope (DST) at the Sacramento Peak Observatory (SPO) of the National Solar Observatory (NSO) on 29 October 2003. The high Strehl ratio encountered in AO corrected short-exposure images provides highly improved signal-to-noise ratios leading to a superior recovery of the object’s Fourier phases. This allows reliable detection of small-scale solar features near the diffraction limit of the telescope. Speckle masking imaging provides access to high-order wavefront aberrations, which predominantly originate at high atmospheric layers and are only partially corrected by the AO system. In addition, the observations provided qualitative measures of the image correction away from the lock point of the AO system. We further present a brief inspection of the underlying imaging theory discussing the limitations and prospects of this multi-faceted image reconstruction approach in terms of the recovery of spatial information, photometric accuracy, and spectroscopic applications.The editors apologize to the authors: due to a misunderstanding during the editorial process, the publication of this paper has been delayed.     

板状绿柱石晶体的结构测定

自然界中绿柱石晶体多为柱状,具板状晶形的绿柱石非常少见。本文对产于四川雪宝顶云英岩晶洞中的无色透明板状绿柱石进行了精确的结构分析,并与产于阿尔泰山号伟晶岩脉中的柱状绿柱石进行了比较。与阿尔泰柱状绿柱石相比,雪面板状绿石富Ｌi、Ｎａ,ｃ／ａ值较高,为１．００１,属钠－锂绿柱石或“四面体”绿柱石。本文还对这种特殊形貌柱石的形成机制进行了初步讨论,成矿流体中Ｌi的浓度以及Ｓi的化学形态可能是影响柱石忻驳闹     

资料插值的进展

对气候学中资料插值、数值天气预报中的客观分析和气候模拟中的降尺度技术作了统一论述，重点是气候资料插值的原理和进展。由于应用领域不同，这些技术也是很不相同的，但它们的动力学和统计学原理是相近或一致的。近十年来三种插值技术，尤其在建立计算机自动化插值系统方面，都取得了长足进展。     

Trends in chemical composition of precipitation in Nanjing, China, during 1992–2003

In this study, variations of the chemical composition of precipitation in Nanjing, China, over a 12-year period (1992–2003) are presented. The average annual concentration of pH value was 5.15, ranging from 4.93 to 5.36, and there was no significant trend in the acidity of precipitation. SO₄²⁻, Cl⁻ and NO₃⁻ were the main anions, while Ca²⁺, NH₄⁺ and Mg²⁺ were the main cations. The concentrations of these main ions were very high compared to those reported in many other areas around the world. Most of the ions came from anthropogenic and crustal sources. High correlations were found among dust-derived cations Ca²⁺, Mg²⁺and K⁺, between Cl⁻ and SO₄²⁻, between Cl⁻ and NH₄⁺ and between acidic anions and dust-derived cations, such as SO₄²⁻ and Ca²⁺, SO₄²⁻ and K⁺, Cl⁻ and Ca²⁺, Cl⁻ and K⁺, F⁻ and Mg²⁺ and F⁻ and K⁺. A significant decreasing trend was observed in concentration of SO₄²⁻ because of the abatement strategies for SO₂ emissions and energy policy change, while a significant increasing trend was found in the contribution of NO₃⁻ to acidification due to the rapidly growing number of motor vehicles. A significant decreasing trend was found in dust-derived cation Ca²⁺ due to more stringent controls of industrial dust emissions and rapid urbanization reducing the amount of open land, while the contribution of NH₄⁺ to neutralization increased relatively.