Echo mapping of active galactic nuclei

Echo mapping makes use of the intrinsic variaibility of the continuum source in active galactic nuclei to map out the distribution and kinematics of line‐emitting gas from its light travel time‐delayed response to continuum changes. Echo mapping experiments have yielded sizes for the broad line‐emitting region in about three dozen AGNs. The dynamics of the line‐emitting gas seem to be dominated by the gravity of the central black hole, enabling measurement of the black‐hole masses in AGNs. We discuss requirements for future echo‐mapping experiments that will yield the high‐quality velocity–delay maps of the broad‐line region that are needed to determine its physical nature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

用超导重力仪的潮汐观测资料研究海潮模型

系统研究了潮汐观测资料中海潮模型的适应性问题,用基于数值离散褶积积分方法获得的海潮负荷对武昌超导重务仪观测资料作负荷改正。结果说明,海潮负荷改正后的重力场观测残差大大降低了,与理论潮汐参数模型相比,８个主要潮流的平均振幅因子由改正前的１．３８％降至０．１３％和０．２６％。     

Contributions of groundwater conditions to soil and water salinization

 Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration, hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition. These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region, Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate precipitation and dissolution of capillary salts. Received, May 1998 · Revised, July 1998 · Accepted, September 1998     

甘肃张掖白垩纪早Aptian期黑色页岩揭示的气候岁差驱动及其意义*

白垩纪中期是温室气候的典型代表,在该时期地球经历了深刻的环境变化。有研究表明白垩纪中期欧洲低纬(约20°~30°N)地区海相地层的黑色页岩呈现斜率信号,同一时期同样纬度的中国地区以陆相沉积为主,但陆相低纬黑色页岩的轨道尺度周期研究较少。因此本研究选择甘肃张掖南台子白垩纪早Aptian期下沟组黑色页岩(古纬度约23°N)作为研究对象,以CaCO₃含量作为高分辨率古气候替代性指标,利用平均频谱拟合差和年代标尺优化法分析了南台子早Aptian期下沟组黑色页岩段的轨道周期变化,并利用频谱分析方法对调谐后的时间域序列进行分析。结果显示南台子下沟组黑色页岩段以岁差周期为主导,与欧洲低纬地区相关研究显著不同。这一气候变化的探索不仅提供了中国西北地区白垩纪轨道尺度气候变化的新证据,而且也有助于更全面认识白垩纪中期低纬地区气候变化的驱动机制。     

云南5月降雨量与前期季节内振荡活动相互关系的分析研究

云南地处低纬高原,受南亚季风影响,其5月降雨量的多寡基本表征了这一地区雨季开始的早晚,对该地区的农业生产有着重要的影响,本文利用TBB（黑体辐射温度）资料及云南地区的降水资料,分析研究了该地区5月降雨量与前期印度洋赤道地区季节内振荡活动的关系。分析结果表明,冬季印度洋赤道地区季节内振荡活动的强弱与次年5月云南地区的降雨量有着密切的联系,即,当冬季印度洋赤道地区季节内振荡活动较强时,次年云南地区5月降雨量较常年偏多;反之,则偏少。     

中国东北全新世干湿状况的演变

通过综合分析植物花粉,沙土埋藏土壤,泥炭形成与发展,沙丘活动历史,黄土状土堆积和黑土发育等多种资料表明,我国东北地区的湿润程度或土壤水分含量在５ｋａ ＢＰ以前的早中全新世较低,中晚全新世不能增加,早中全新世最干燥时段出现的＾１４Ｃ年代９－８ｋａ ＢＰ,中晚全新世湿润时期可能是最近的２ｋａ,近现代气候比过去１０ｋａ平均状况湿润。     

Organic carbon isotopes of the Sinian and Early Cambrian black shales on Yangtze Platform, China

Organic matter of the Sinian and early Cambrian black shales on the Yangtze Platform belongs to the light carhon group of isotopes with the δ¹³C values from - 27% to - 35 %, which are lower than those of the contempomneously deposited carbonates and phosphorites. A carbon isotope-stratified paleooceanographic model caused by upwelling is proposed, which can be used not only to interpret the characteristies of organic carbon isotopic compositions of the black shales, but also to interpret the paleogeographic difference in the organic carbon isotope compositions of various types of sedimentary rocks. Project supported by the National Natural Science Foundation of China (Grant No. 49472114) and the Open Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.     

Calculation of reflectance values for two models of texture of carbon materials

This paper presents two models of texture of carbon materials possessing porosity. For both models, R_MAX, R_INT and R_MIN values of reflectance have been calculated by modified Ting's 3A method [Ting, F.T.C., 1978. Petrographic techniques in coal analysis. In: C. Karr (Ed.), Analytical Methods for Coal and Coal Products, Vol. 1. Academic Press, New York, 1978, pp. 3–25]. It has been found that the reflectance indicating surface (RIS) for the studied models of texture changes from a biaxial negative up to a biaxial positive one (the type A texture) depending on the shape and size of pores. In particular case, for the type B texture and the isometry of pores, a uniaxial negative RIS is merely obtained.     

Potential wind erosion rate response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia reach of the Yellow River,China, 1986–2013

Climate and land‐use changes could strongly affect wind erosion and in turn cause a series of environmental problems. Thus, the objective of this study was to assess potential wind erosion rate (PWER) response to climate and land‐use changes in the watershed of the Ningxia–Inner Mongolia Reach of the Yellow River (NIMRYR), China. The watershed of NIMRYR suffers from serious wind erosion hazards, and over recent decades, wind erosion intensity and distribution has changed, following climate and land‐use changes. To understand these processes in the NIMRYR watershed, the Integrated Wind Erosion Modelling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to calculate the PWER under different climate conditions and land‐use scenarios, and to assess the influences of climate and land‐use changes on the PWER. The results show the PWER in the whole watershed had a significant declining trend from 1986 to 2013. The results of the relationship among PWER, climate change, and land‐use changes showed that climate change was the dominant control on the PWER change in this watershed. Compared to the period 1986–1995, the average PWER decreased 23.32% and 64.98% as a result of climate change in the periods 1996–2005 and 2006–2013, respectively. In contrast with climate change, the effects of land‐use changes on the average PWER were much lower, and represented a change in PWER of less than 3.3% across the whole watershed. The study method we used could provide some valuable reference for wind erosion modelling, and the research results should help climate and land‐use researchers to develop strategies to reduce wind erosion. Copyright © 2017 John Wiley & Sons, Ltd.     

Are modern metaheuristics successful in calibrating simple conceptual rainfall–runoff models?

In recent years sampling approaches have been used more widely than optimization algorithms to find parameters of conceptual rainfall–runoff models, but the difficulty of calibration of such models remains in dispute. The problem of finding a set of optimal parameters for conceptual rainfall–runoff models is interpreted differently in various studies, ranging from simple to relatively complex and difficult. In many papers, it is claimed that novel calibration approaches, so-called metaheuristics, outperform the older ones when applied to this task, but contradictory opinions are also plentiful. The present study aims at calibration of two simple lumped conceptual hydrological models, HBV and GR4J, by means of a large number of metaheuristic algorithms. The tests are performed on four catchments located in regions with relatively similar climatic conditions, but on different continents. The comparison shows that, although parameters found may somehow differ, the performance criteria achieved with simple lumped models calibrated by various metaheuristics are very similar and differences are insignificant from the hydrological point of view. However, occasionally some algorithms find slightly better solutions than those found by the vast majority of methods. This means that the problem of calibration of simple lumped HBV or GR4J models may be deceptive from the optimization perspective, as the vast majority of algorithms that follow a common evolutionary principle of survival of the fittest lead to sub-optimal solutions.