新疆三工河绿洲土地利用变化系统动力学仿真

从小区域(乡域)尺度出发,综合考虑人口、经济、技术、市场等主要人文因素对绿洲土地利用变化的驱动作用,建立系统动力学（SD）模型,并以天山北麓三工河流域为例,用1978—1998年的实际数据验证了模型的适用性和可靠性,在此基础上,模拟和分析了三种发展模式下本区域1998—2050年土地利用变化过程,结果表明：SD方法对于乡域尺度的土地利用变化研究是适宜的;三种模式下土地利用变化规律表现出明显的差异性,人口、经济、技术、市场等因素对本区域土地利用变化具有显著驱动作用。     

The Gyldén‐type problem revisited: More refined analytical solutions

We resume and consistently extend our previous researches concerning the Gyldén‐type problem (a two‐body problem with time‐dependent equivalent gravitational parameter). To approach most of the concrete astronomical situations to be modelled in this way, we consider a periodic small perturbation. For the nonresonant case, we present a second‐order analytical solution. For the resonant case, we adopt the most realistic astronomical situation: only one dominant term of the Hamiltonian. In this case we point out a fundamental model of resonance, common to every resonant situation, and, moreover, identical to the first fundamental model of resonance . Considering the simplest model of periodic change of the equivalent gravitational parameter, we .nd that all possible resonances are con.ned to the first fundamental model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于物态本构模型的路基动力反应分析

以动力固结理论和瞬态动力学理论为基础,将有效应力物态动本构关系引入到以动力反应与动力固结相耦合、静应力与动应力变化相耦合、孔压的产生、扩散和消散相耦合的动力三维瞬态动力学基本方程组中,形成了饱和土体有效应力物态地震反应分析的完整理论体系。利用有限元法对饱和路基进行了瞬态地震反应分析,较好地反映了土体在震动过程中剪 胀、剪缩的实际性态,比以往引进孔压模型和静-动交替分析计算更为合理。     

The lower mass function of young open clusters: clues to (sub)stellar formation

We report the present day mass functions (PDMFs) of 4 young open clusters over a mass range from 30 Jupiter masses to 3M_ . Three of these clusters have been chosen to have a similar age of ∼100 Myr. Their PDMFs are remarkably similar and are comparable to the field mass function. This suggests little impact of initial conditions (stellar density, metallicity) on the mass distribution and raises some issues concerning the currently debated star and brown dwarf formation theories. The fourth cluster is older (600 Myr) which allow us to investigate the effect of the cluster dynamical evolution on the shape of the mass function. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

构造体制转换与流体多层循环成矿动力学

基于成矿系统动力学研究进展的综合分析, 认为构造体制转换与流体多层循环成矿动力学研究是地球科学跨世纪的重要前沿领域之一, 进而提出这一领域的研究主题和关键问题、研究思路及方法, 阐释其重要意义, 指出构造体制转换与流体多层循环成矿动力学研究以构造演化、流体活动及区域地球化学和地球物理不均一性为基础, 通过变形-流动高温高压实验及计算机数值模拟再现成矿作用过程和机理, 解析构造体制转换与流体多层循环成矿动力学特征, 揭示成矿界面时-空演化规律, 建立成矿系统物质和能量交换-反馈耦合成矿的定量模型.这是深化矿床成因认识的重要基础和实现科学找矿的有效途径, 对地球系统科学和大陆动力学的研究也具有重要意义.      

Total ozone decrease in the Arctic after REP events

Eight periods of relativistic electron precipitation (REP) with electron energies of more than 300 keV are identified from VLF data (10/14 kHz) monitored along the Aldra (Norway) / Apatity (Kola peninsula) radio trace. In these cases, anomalous ionization below 55/50 km occurred without disturbing the higher layers of the ionosphere. The daily total ozone values in Murmansk for six days before and six days after the REP events are compared. In seven of eight events a decrease in the total ozone of about 20 DU is observed. In one event of 25 March, 1986, the mean total ozone value for six days before the REP is bigger han that for six days after, but this a case of an extremely high ozone increase (144 DU during the six days). However, on days 3 and 4 there was a minimum of about 47 DU with regard to REP days, so this case also confirms the concept of the ozone decrease after REP. The difference between mean ozone values for periods six days before and six days after the REPs was found also for 23 points in Arctic on TOMS data. The difference was negative only in Murmansk longitudinal sector. Along the meridian of the trace it was negative at high latitudes in both hemispheres and was near zero at low latitudes.     

Stratosphere-troposphere exchange in an extratropical cyclone, calculated with a Lagrangian method

A Lagrangian technique is developed and applied to calculate stratosphere-troposphere exchange in an extratropical cyclone. This exchange is computed from the potential vorticity or PV along trajectories, calculated from ECMWF circulation data. Special emphasis is put on the statistical significance of the results. The computed field of the cross-tropopause flux is dominated by elongated patterns of statistically significant large downward and small upward fluxes. The downward fluxes mainly occur in the lower part of the considered tropopause folds. The upward fluxes are found near the entrance of the folds, in the tropopause ridges. The ratio between the area averaged downward and upward cross-tropopause fluxes increases with increasing strength of the cyclone. Since the largest fluxes are shown to occur in the regions with the largest wind shear, where PV-mixing is thought to cause large cross-tropopause fluxes, the results are expected to be reliable, at least in a qualitative sense. The position of a tropopause fold along the northwest coast of Africa is confirmed by total ozone observations. The results indicate that the applied Lagrangian technique is an appropriate tool for diagnosing stratosphere-troposphere exchange.     

20世纪中国大陆6级以上地震活动图像及其意义

１９００年以来,中国大陆经历了５个地震活跃期和４个地震平静期,活跃期中Ｍｓ≥６．０地震为线性分布和块状分布。平静期中Ｍｓ≥６．０地震为线性分布。线性分布和块状分布形象地展示了每个活动期中作用力的传递方向和途径,以及地震活动区域所受到的严格约束。因此,为进一步探讨中国大陆地震动力学和地震活动区域提供了新的线索。     

沙坡头地区固沙植被土壤水分动态研究

沙坡头地区始建于1956年的无灌溉人工固沙植被,是我国交通干线防沙体系的成功模式。利用40余年的土壤水分定位观测数据,分析了不同期间建立的固沙植被土壤水分的时空变化特征及对植被的影响。结果表明,固沙植被发展至9~10a后土壤含水量开始明显下降,特别是较深层(>100cm)的含水量下降明显;0~40cm层土壤水分含量与降水相关显著,而降水对40~300cm层土壤水分的含量影响不显著;深根系固沙植物对根际区域水分的利用,进一步恶化了固沙区土壤深层的水分状况,进而抑制了这些植物的生长和生存,间接地影响了原有固沙植被组成和稳定性;经过40多年的演变,固沙植被中优势灌木种的盖度从最大盖度47.6%降至6%~9%,群落中草本和微生物结皮层得到发育。当深根系灌木的盖度降低至6%~9%时,深层土壤可维持一个相对稳定的低含水量。     

地质系统的复杂性—地质科学的基本问题(Ⅰ)

笔者根据其所提出的“地质作用与时空结构是一切地质现象的本质与核心”的自然哲学理念将地质科学的学科体系划分为地球物质的成分与结构、地质作用、地质学场与地质系统的演化等四大基本领域, 它与9个重大基础地质问题以及与其相关的基础理论问题相对应(表 2).笔者将其已发表的地质科学的复杂性理论“地质作用的临界过程动力学——地质系统在混沌边缘分形生长”应用于研究9个重大基础地质问题, 着重对于其中所包含的主要基础理论问题的实质及其理论与研究方法作较深入而简要的剖析.目的是通过将地质系统的复杂性作为地质科学的基本问题的新视角对古老而常新的地质科学进行再认识, 将重大基础地质问题的研究提高到非线性科学和复杂性理论的层次, 并实现地质科学向精确科学的跨越, 取得突破性进展