末次盛冰期以来河北平原第四系地下水流系统的演变

以区域自然地理及地质历史分析为基础,以环境同位素及大陆盐化咸水后期变化为实证依据,重塑了末次盛冰期以来河北平原第四系地下水流模式演变。研究发现,末次盛冰期以来河北平原第四系地下水流系统经历3个演变阶段:(1)距今18～15ka的低海平面时期,接受持续补给,地下水得到充分交替,发育穿透达到或接近第四系底界的区域水流系统;(2)距今15～12ka的海平面急剧抬升期,地形势差减弱,发育穿透第三含水层组的早期中间水流系统,与此同时区域水流系统趋于停滞;(3)距今2.5ka以来,现代河流地貌成形,高位河床与低位河床及河间低地的势差成为主要驱动力,发育穿透第一及第二含水层组的晚期中间水流系统。随着海平面抬升,后期发育的水流系统切割前期水流系统的一部分并叠置其上。因此,现今河北平原第四系的地下水流系统乃是不同演变时期地下水流系统的时空四维集合体。其他濒海平原,乃至侵蚀强度随时间减弱的内陆盆地,都有可能出现类似图景。距今12ka前后形成的大陆盐化咸水,由上升水流带到浅部,导致浅层咸水以及土地盐渍化,乃是河北平原水资源利用及生态与环境保护的关键性不利因素。     

IPCC AR6报告解读：地球能量收支、气候反馈和气候敏感度

文中对IPCC第六次评估报告（AR6）第一工作组（WGI）报告的第七章关于地球能量收支、气候反馈和气候敏感度中的重要内容进行了凝练,并简要总结该方面的最新研究成果和结论。评估显示,自工业革命以来,人类活动造成的有效辐射强迫（ERF）为2.72 [1.96~3.48] W/m²,其中,均匀混合温室气体的贡献为3.32 [3.03~3.61] W/m²,气溶胶的贡献为-1.1 [-1.7~-0.4] W/m²。净的气候反馈参数为-1.16 [-1.81~-0.51] W/(m²∙℃),云仍然是气候反馈整体不确定性的最大来源。平衡态气候敏感度（ECS）和瞬态气候响应（TCR）可用于评估全球平均地表气温对强迫的响应,是衡量全球气候响应的有效手段。ECS和TCR的最佳估计分别为3.0 [2.0~5.0]℃和1.8 [1.2~2.4]℃。     

公交车辆全线运行状态的监督站牌及查询系统

针对出行者对公交车辆运行信息的需求,基于GPS技术设计了一个动态显示公交车辆位置信息的监督站牌系统,并提供公交位置信息的网络查询服务,方便出行者了解公交车辆的实时运营信息,以及对公交车辆的实时监督.系统以LabVIEW为软件开发平台对数据进行分析与处理,利用ASP.NET进行Web网页开发并与数据库交互,实现公交系统的智能运营和智能服务.通过实际验证,该方案具有可行性、实用性.     

墨西哥湾“深水地平线”溢油事故处理研究进展

2010年4月20日美国墨西哥湾"深水地平线"石油钻井平台发生爆炸,并引发大火,致使大量的原油(~500万桶)在深海(~1 500m)泄露,这场灾难造成了巨大的环境和经济损失,也对石油开采业的发展产生了负面影响。文中综述了此次事故溢出石油的总量,泄露速率以及测量相关数据中所涉及的技术及方法,对进一步研究溢油转移的趋势和转化过程具有指导意义。喷洒了6.6×106 L的消油剂,消油剂可以促使溢油的快速分散,同时也会给海洋生态系统造成一定的影响。该事故对墨西哥湾的植被和海洋生物有不同程度的影响,如沼泽植被、海水中的浮游动/植物、鱼类、贝类、珊瑚虫、迁徙鸟类,甚至是墨西哥湾大型底栖生物。此次溢油事故涉及各种不同的环境情况,为研究石油烃降解菌在溢油转移和降解过程中种群和群落的变化提供了一个独特的机会,消油剂处理过的溢油转化机理以及微生物降解过程中生物表面活性剂的产生与生物标志物以及微生物菌落的变化之间的关系,仍需要进一步的深入研究和探讨。     

On Szebehely's problem for holonomic systems involving generalized potential functions

We consider the problem of finding the generalized potential function V = U _i(q ¹, q ²,..., q ⁿ)q ⁱ + U(q ¹, q ²,...;q ⁿ) compatible with prescribed dynamical trajectories of a holonomic system. We obtain conditions necessary for the existence of solutions to the problem: these can be cast into a system of n – 1 first order nonlinear partial differential equations in the unknown functions U ₁, U ₂,...;, U _n, U. In particular we study dynamical systems with two degrees of freedom. Using adapted coordinates on the configuration manifold M ₂ we obtain, for potential function U(q ¹, q ²), a classic first kind of Abel ordinary differential equation. Moreover, we show that, in special cases of dynamical interest, such an equation can be solved by quadrature. In particular we establish, for ordinary potential functions, a classical formula obtained in different way by Joukowsky for a particle moving on a surface.Work performed with the support of the Gruppo Nazionale di Fisica Matematica (G.N.F.M.) of the Italian National Research Council.     

Generalized Lyapunov exponents indicators in Hamiltonian dynamics: An application to a double star system

The Lyapunov characteristic numbers (LCNs) which are defined as the mean value of the distribution of the local variations of the tangent vectors to the flow (=ln _k ⁱ ) (see Froeschlé, 1984) have been found to be sensitive indicators of stochasticity. So we computed the distribution of these local variations and determined the moments of higher order for the integrable and stochastic regions in a binary star system with =0.5.     

Glacier inventory of the Gran Campo Nevado Ice Cap in the Southern Andes and glacier changes observed during recent decades

The Gran Campo Nevado (GCN) forms an isolated ice cap on the Península Muñoz Gamero (PMG) located 200 km to the south of the Southern Patagonia Icefield (SPI). We present a glacier inventory of the GCN made up by 27 drainage basins (in total 199.5 km²) and other small cirque and valley glaciers of the southern part of PMG (in total 53 km²). The glacier inventory is based on a digital elevation model (DEM) and ortho-photos. Contour lines from maps, relief information derived from Landsat TM satellite imagery from 1986 and 2002 and stereoscopic data from aerial photos were combined in a knowledge-based scheme to obtain a DEM of the area. A digital ortho-photo map based on aerial photos from 1998 and several ortho-photos based on aerial photos from 1942 and 1984 could be produced from the initial DEM. A geographical information system (GIS) served to outline the extent of the present glaciation. All major glaciers of the GCN show a significant glacier retreat during the last 60 yr. Some of the outlet glaciers lost more than 20% of their total area during this period. Overall glacier retreat amounts to 2.8% of glacier length per decade and the glacier area loss is 2.4% per decade in the period from 1942 to 2002. We hypothesise that GCN glaciers may have reacted faster and more synchronously with the observed warming trend during recent decades when compared with the SPI.     

Strong bursts and diffusion in avalanching systems

The connection between avalanche dynamics and space physics has been studied for several years. In that context we recently suggested an avalanche model which explains the phenomena of reconnection. In this work the model is generalized to include the influence of an extremely strong perturbation, reflecting the effect of plasma storms originating from the sun. In addition, we allow for diffusion processes and show that the behavior changes with the onset of diffusion processes, rendering it quasi-periodic, along with the supression of small-size avalanches.     

White dwarf + red dwarf binary systems and the period gap of cataclysmic variables

Cataclysmic variables (CV) and pre-cataclysmic binaries (PCB) are discussed. The main difference between them (accretion or its absence) is shown to be a consequence of the evolutionary process and the properties of their progenitors. Both types of system have a bimodal distribution of their periods, but the extrema are in counterphase. Luminosity-effective temperature diagrams for the primary components are used to show that both systems have approximately the same age, which conflicts with the notion of PCBs as precursors of CVs. Calculations of the maximum distance between components for which the system remains stable show that CVs have passed this limit, while PCBs maintain their stability during this evolution. It is suggested that, after ejecting a common shell, future CVs immediately become semi-detached systems. It this is so, then there must be cataclysmic variables which are the central stars of planetary nebulae. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 427–439 (August 2007).     

Close encounters in young stellar clusters: implications for planetary systems in the solar neighbourhood

The stars that populate the solar neighbourhood were formed in stellar clusters. Through N -body simulations of these clusters, we measure the rate of close encounters between stars. By monitoring the interaction histories of each star, we investigate the singleton fraction in the solar neighbourhood. A singleton is a star which formed as a single star, has never experienced any close encounters with other stars or binaries, or undergone an exchange encounter with a binary. We find that, of the stars which formed as single stars, a significant fraction is not singletons once the clusters have dispersed. If some of these stars had planetary systems, with properties similar to those of the Solar System, the planets' orbits may have been perturbed by the effects of close encounters with other stars or the effects of a companion star within a binary. Such perturbations can lead to strong planet–planet interactions which eject several planets, leaving the remaining planets on eccentric orbits. Some of the single stars exchange into binaries. Most of these binaries are broken up via subsequent interactions within the cluster, but some remain intact beyond the lifetime of the cluster. The properties of these binaries are similar to those of the observed binary systems containing extrasolar planets. Thus, dynamical processes in young stellar clusters will alter significantly any population of Solar System-like planetary systems. In addition, beginning with a population of planetary systems exactly resembling the Solar System around single stars, dynamical encounters in young stellar clusters may produce at least some of the extrasolar planetary systems observed in the solar neighbourhood.