An X-Ray Study of Lobe-Dominated Radio-Loud Quasars with XMM-Newton     

Li-Ming Dou Wei-Min Yuan 《中国天文和天体物理学报》2008,8(6)

We report on our results of X-ray spectral analysis for a sample of radio-loud quasars covering a wide range of the radio core-dominance parameter, R, from core-dominated to lobe-dominated objects, using data obtained mostly with the XMM-Newton Observatory. We find that the spectral shape of the underlying power-law continuum is flat even for the lobe-dominated objects (average photon index ～ 1.5), indistinguishable from that of core-dominated quasars. For lobe-dominated objects, contribution of X-rays from the jets is expected to be very small based on previous unification schemes, more than one order of magnitude lower than the observed X-ray luminosities. Assuming that radio-loud quasars follow the same X-ray-UV/optical luminosity relation for the disk-corona emission as found for radio-quiet quasars, we estimate the X-ray flux contributed by the disk-corona component from the optical/UV continuum. We find that neither the luminosity, nor the spectral shape, of the disk-corona X-ray emission can account for the bulk of the observed X-ray properties. Thus in lobe-dominated quasars, either the disk-corona X-ray emission is much enhanced in strength and flatter in spectral shape (photon index～1.5) compared to normal radio-quiet quasars, or their jet X-ray emission is much enhanced compared to their weak radio core-jet emission. If the latter is the case, our result may imply that the jet emission in X-rays is less Doppler beamed than that in the radio. As a demonstrating example, we test this hypothesis by using a specific model in which the X-ray jet has a larger opening angle than the radio jet.  相似文献   

Zircon U-Pb Ages of Quaternary Loess-Paleosol Sequences from the Luochuan Section: Implication for Sediment Provenance     

GONG Hujun  XIE Wenbin  WANG Jiading  ZHANG Rui  ZHANG Yunxiang  YANG Lirong 《《地质学报》英文版》2017,91(1):357-358

<正>Objective The sediment provenances of the thick Quaternary Loess-Paleosol sequences of the Chinese Loess Plateau can provide clues to the evolution of the paleoclimate and paleoenvironment in East Asia.Furthermore,based on the proposed sediment sources and transport routes,the evolution of the East Asian monsoon can be evaluated.  相似文献   

Vertical dynamic impedance of pile considering the dynamic stress diffusion effect of pile end soil     

Tian-Le Liu  Wen-Bing Wu  Bin Dou  Guo-Sheng Jiang  Shu-Hui Lü 《Marine Georesources & Geotechnology》2017,35(1):8-16

A new analytical model is presented to analyze the dynamic stress diffusion effect of pile end soil on the vertical dynamic impedance of the pile. The surrounding soil of the pile is modeled by using the plane strain model and the pile is simulated by using one-dimensional elastic theory. Finite soil layers below the pile end are modeled as conical fictitious soil pile with stress diffusion angle which reflects the dynamic stress diffusion effect of pile end soil. By means of the Laplace transform and impedance function transfer method, the analytical solution of the vertical dynamic impedance at the pile head in frequency domain is yielded. Then, a comparison with other models is performed to verify the conical fictitious soil pile model. Finally, based on the proposed solution, the selected numerical results are compared to analyze the influence of dynamic stress diffusion effect for different design parameters of the soil-pile system on the vertical dynamic impedance at the pile head.  相似文献   

轻小型航空遥感系统空对地检校试验分析     

韩晓冬  杨娜  刘力荣  关艳玲 《测绘通报》2013,(1):33-36

对高精度轻小型航空遥感空对地检校试验进行分析.在已有检校场基站及控制点、检查点布设方案的基础上,结合项目实际需要,提出满足项目需求的检校场布设方案.通过检校场空三及检校参数计算结果,评价检校场布设的合理性,并以国外成熟的POS AV610直接地理定位精度为参照,评价国产POS直接地理定位精度及可行性.  相似文献   

潮汐强度与咸潮上溯距离试验   总被引：1，自引：0，他引：1       下载免费PDF全文

卢陈  袁丽蓉  高时友  陈荣力  苏波 《水科学进展》2013,24(2):251-257

采用物理模型实验方法对不同潮差驱动下咸水入侵距离进行实验研究,结果表明存在潮差临界值使得咸水入侵距离最短,当潮差小于该临界值,咸水入侵距离随潮差增大呈快速减小趋势,而大于该临界值则呈缓慢增大趋势。基于实验数据对盐淡水混合进行理论分析,揭示了实验现象的产生机制:①潮差增大过程中盐淡水混合由高度分层变为均匀混合,导致驱动咸潮入侵的动力发生了改变;②当盐淡水为弱混合类型,盐淡水高度分层,重力环流输运是盐进入河口的主要方式,潮汐强度增大减小了盐淡水分层,减弱了重力环流的输运作用,因此入侵距离变小;③当盐淡水为强混合类型,盐淡水混合均匀,重力环流输运作用大大减弱,潮汐扩散成为主要的输运方式,潮汐增强使得扩散能力增大,因此潮汐强度越大,咸潮入侵距离越大。  相似文献   

Measurements of physical characteristics of summer snow cover on sea ice during the Third Chinese Arctic Expedition     

TingFeng Dou  CunDe Xiao 《寒旱区科学》2013,5(3):0309-0315

The spatial distribution of snow cover on the central Arctic sea ice is investigated here based on the observations made during the Third Chinese Arctic Expedition. Six types of snow were observed during the expedition: new/recent snow, melt-freeze crust, icy layer, depth hoar, coarse-grained, and chains of depth hoar. Across most measurement areas, the snow surface was covered by a melt-freeze crust 2-3 cm thick, which was produced by alternate strong solar radiation and the sharp temperature decrease over the summer Arctic Ocean. There was an intermittent layer of snow and ice at the base of the snow pack. The mean bulk density of the snow was 304.01±29.00 kg/m3 along the expedition line, and the surface values were generally smaller than those of the subsurface, confirming the principle of snow densification. In addition, the thicknesses and water equivalents of the new/recent and total-layer snow showed a decreasing trend with latitude, suggesting that the amount of snow cover and its spatial variations were mainly determined by precipitation. Snow temperature also presented significant variations in the vertical profile, and ablation and evaporation were not the primary factors in the snow assessment in late summer. The mean temperature of the surface snow was 2.01±0.96°C, which was much higher than that observed in theinterface of snow and sea ice.  相似文献   

准噶尔盆地中部1区钻井优化设计研究          下载免费PDF全文

窦玉玲  陈明  徐云龙 《探矿工程》2012,39(5):12-14

围绕钻井工程设计优化展开研究,论述了准噶尔盆地中部1区井身结构优化过程,提出了井身结构优化方案;建立了该区岩石可钻性剖面,结合钻头使用效果评价,推荐了钻头选型方案;介绍了该区钻井液体系优选及使用情况。形成了准噶尔盆地中部1区钻井设计优化方案,提出了后续研究方向。  相似文献   

Simulation and control of the linked systems of water quantity–water quality–socio-economics in the Huaihe River basin     

Ming Dou  Qiting Zuo  Junxia Ma  Guiqiu Li 《水文科学杂志》2013,58(4):763-774

Abstract

This work makes explicit an algebraic expression giving the matrix of transient influence coefficients associated with a one-dimensional semi-confined aquifer model. The domain studied is divided into a series of connected and completely mixed compartments over which the governing equation is discretized. The discrete equations obtained are solved for the compartmental hydraulic head and used to derive the algebraic expression in question. The basic properties of the so-called algebraic influence coefficients are investigated. In particular, their consistency with the exact Green function is highlighted. Finally, the newly derived influence coefficients are applied to a simplified aquifer system in order to formulate and solve the problem of identifying illegal groundwater pumping.  相似文献   

铜绿微囊藻(Microcystis aeruginosa)与三种丝状蓝藻间的相互作用   总被引：10，自引：0，他引：10  

张婷  宋立荣 《湖泊科学》2006,18(2):150-156

研究了单细胞铜绿微囊藻和三种丝状蓝藻（水华束丝藻、水华鱼腥藻及土生席藻）间的相互作用，包括以下两个方面的内容：①铜绿微囊藻细胞滤出液对水华束丝藻、水华鱼腥藻及土生席藻生长的影响；②水华束丝藻、水华鱼腥藻及土生席藻细胞滤出液对铜绿微囊藻生长的影响．研究发现，当滤出液浓度为60％（滤出液与BG11的体积比为3：2）时，铜绿微囊藻细胞滤出液对水华束丝藻、水华鱼腥藻的生长有显著促进效果，尤其对水华束丝藻的作用更加明显；对土生席藻的生长却起着微弱的抑制作用，仅表现于100％细胞滤出液中．对铜绿微囊藻而言，土生席藻细胞滤出液对其的生长起着显著抑制作用，浓度越高、抑制作用越强；而水华束丝藻、水华鱼腥藻仅在100％细胞滤出液中才表现出微弱的抑制作用．为验证营养盐浓度差异是否影响滤出液的作用效果，进行了无机营养盐（NO3-N、NH4^＋-N、PO4-P）干扰的消除试验．结果表明，无机营养盐（（NO3-N、NH4^＋-N、PO4-P）的改变并不影响滤出液的作用效果，从而我们推测水华蓝藻之间存在着化感作用．本研究为解释自然水体中藻类种群演替的原因，深入认识水华蓝藻的动力学机制提供了新的实验证据．  相似文献   

Modeling Research of the 27-day Forecast of 10.7 cm Solar Radio Flux (I)     

Liu Si-qing  Zhong Qiu-zhen  Wen Jing  Dou Xian-kang 《Chinese Astronomy and Astrophysics》2010

Adopting the autoregressive method for time-series modeling, we have made a study on the medium-term forecast of solar 10.7 cm radio flux (F10.7). The result of forecast experiments and the error analysis indicate that when the solar activity is at a rather low level and the 27-day periodicity of F10.7 is apparent, the autoregressive forecast method has a high accuracy and relatively ideal effectiveness, but when a large active region appears or disappears on the solar dusk, the forecast effectiveness is not ideal. This means that the autoregressive method for the time-series modeling can reflect well the 27-day periodicity of F10.7, and that it has certain applicability for building a mediumterm forecast model of F10.7. By comparing the forecast results in the period from 21th September 2005 to 7th June 2007, it is demonstrated that the accuracy of the autoregressive forecast method is equivalent to that of the forecast made by the American Air Force.  相似文献