Developing land use scenario dynamics model by the integration of system dynamics model and cellular automata model

Models of land use change are useful tools for un-derstanding the analysis of the cause and conse-quences of land use changes, assessing the impacts of land use system on ecological system and supporting land use planning and policy[1,2]. Modeling land use scenario changes and its potential impacts on the structure and function of the ecosystem in the typical regions are regarded as one of the good ways to un-derstand the interactive mechanism between land use system and ecological system[3―10…     

新疆博格达山晚古生代地层的形成时代、物源及其演化:碎屑锆石U-Pb年代学证据

新疆博格达山主体由石炭系海相火山—沉积岩系组成, 以发育两期双峰式火山岩, 但不发育花岗岩为特征, 对其晚古生代地层时代的划分和演化争议较大.本文重点对博格达山北部两个晚古生代砂岩进行了碎屑锆石U-Pb年代学分析, 重新标定博格达山地区晚古生代地层的形成时代; 利用物源区的演化, 约束晚古生代构造演化.测年结果显示博格达上亚群砂岩的碎屑锆石表面年龄值分布范围较宽, 主峰年龄为343～284 Ma(80%), 次峰年龄为386～375 Ma(3%)、503～441 Ma(7%)和871～735 Ma(10%); 芦草沟组砂岩的碎屑锆石表面年龄值非常集中, 主峰年龄为358～279 Ma(97%), 次峰年龄为257～251 Ma(约3%).博格达山中部原石炭纪博格达群上亚群与西部和南部下芨芨槽群相当, 应属于早二叠世, 中部—东部的石炭—二叠纪界线应在博格达下亚群—上亚群或居里得能组—沙雷塞尔克组之间的不整合面之中.博格达北部地区晚二叠世以南侧天山物源区供给为主, 反映出晚古生代期间博格达山地区至少存在晚石炭世末和中二叠世两期构造隆升.结合区域火山岩与火山碎屑岩的研究, 认为博格达山地区晚古生代主要经历4个演化阶段: 早石炭世弧后盆地裂解阶段、晚石炭世碰撞拼贴阶段、早二叠世碰撞后伸展阶段、中-晚二叠世再次隆升到稳定阶段.     

Vulnerability and fate of a coastal sand dune complex,Rosetta-Idku,northwestern Nile Delta,Egypt

Types, distribution, and origin of recent sand dunes between Rosetta and Idku, in the western sector of the Nile Delta, Egypt were investigated. Sand samples from the dunes, beach, and seafloor were studied for grain size distribution and mineralogical composition. It has been found that most of the dunes in the study area have been subjected to deterioration and removal due to the construction of buildings and the International Coastal Highway. The remnant constitutes a damaged belt of foredunes that extends from El Bouseily village to the west of Idku town. The dune’s origin is interpreted to be the result of coastal drifting and the subsequent transport of sediments of the former Canopic Nile branch eastward by the predominant longshore current and by aeolian processes. The blown sand grains accumulated to form a belt of coastal sand dunes of original longitudinal and crescentic forms. Urbanization of the coast has severely altered the landscape. The study area is considered vulnerable to the impacts of climate change and the expected rise in sea level. The outcome of potential sea level rise is serious; erosion problems are expected to be exacerbated and vast areas from land and property would be lost. Thus, protection and preservation the remaining dunes in the study area are vital requirements for shore protection.     

离子刻蚀全息光栅的研究

利用国产的光刻胶和国产离子刻蚀机在蒸镀的铝基衬底上进行刻蚀全息光栅,在国内是一项较新的技术。本文介绍和论述了该试验工作的工艺过程、参数计算和测试方法,得出了试验结果和参数计算值基本吻合的结论,并指出了进一步改善质量的方向。     

东北印度洋沉积岩芯热释光与古气候变化

孟加拉深海扇中扇的MD77181和下扇的MD81345岩芯沉积物天然热释光变化与古气候变化有明显的对应关系,岩芯记录的时间跨度约300 ka BP.将两支岩芯的热释光测量结果与δ18O、CaCO3含量和磁化率结果对比后发现,热释光强度与磁化率变化存在显著的一致性.它们与间冰期和冰期气候变化的对应关系表现为:间冰期,风化作用减弱,输入海洋的陆源性矿物减少,对碳酸盐的稀释作用低于冰期,热释光和磁化率同时降低.此时,热释光强度随碳酸盐含量的增加而增大,说明沉积物热释光主要来自于碳酸盐矿物的贡献,表现为海进沉积环境特征.在冰期,陆地风化作用加强,输入海洋的陆源性矿物增加,对碳酸盐的稀释作用增强,热释光强度随陆源物的增多而增强,热释光和磁化率同时增大.说明沉积物热释光主要来自陆源矿物,表现为海退沉积环境特征.     

高空西北气流下铜仁东部特大暴雨的预报分析及思考

利用贵州省预报业务常规、地面自动站加密观测资料、NCEP/FNL1°×1°再分析资料、业务数值预报模式,分析2020年6月29日铜仁市东部高空西北气流影响下的特大暴雨环境场特征,地面中小尺度场特征以及3家数值预报模式检验,初步分析产生此次特大暴雨的可能成因是在副高东南退,东北冷涡槽后高空西北气流维持,低层冷平流下传西输,地面辐合维持增强为涡旋,地面东路弱冷空气侵入,能量锋区斜压性增强;短临监测发现雷达回波有列车效应,低层辐合高层辐散的共轭配置,中层气旋式辐合;初步得出了西北气流影响下弱天气尺度环境场的铜仁市东部暴雨的预报着眼点。     

莱州湾地区500年来旱涝灾害指数系列的建立

作者根据《山东省历代自然灾害志》的记载，应用Foxpro提供的软件，建立了莱州湾地区500年来旱涝灾害的汉字库，并通过一系列转换，将其转为数字库；将旱涝灾情的文字记我转换为区域旱涝指数，并与现代降水资料相对接，建立了1470－1990年共521年的历年逐季旱涝灾害指数序列，为分析该地区旱涝灾害发生规律和预测提供了依据。     

Numerical simulation of strong ground motion for the <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript>8.0 Wenchuan earthquake of 12 May 2008

The Wenchuan earthquake of 12 May 2008 is the most destructive earthquake in China in the past 30 years in terms of property damage and human losses. In order to understand the earthquake process and the geo-morphological factors affecting the seismic hazard, we simulated the strong ground motion caused by the earthquake, incorporating three-dimensional (3D) earth structure, finite-fault rupture, and realistic surface topography. The simulated ground motions reveal that the fault rupture and basin structure control the overall pattern of the peak ground shaking. Large peak ground velocity (PGV) is distributed in two narrow areas: one with the largest PGV values is above the hanging wall of the fault and attributed to the locations of fault asperities and rupture directivity; the other is along the northwestern margin of the Sichuan Basin and caused by both the directivity of fault rupture and the amplification in the thick sediment basin. Rough topography above the rupture fault causes wave scattering, resulting in significantly larger peak ground motion on the apex of topographic relief than in the valley. Topography and scattering also reduce the wave energy in the forward direction of fault rupture but increase the PGV in other parts of the basin. These results suggest the need for a localized hazard assessment in places of rough topography that takes the topographic effects into account. Finally, had the earthquake started at the northeast end of the fault zone and ruptured to the southwest, Chengdu would have suffered a much stronger shaking than it experienced on 12 May, 2008. Supported by the U.S. National Science Foundation (Grant Nos. EAR 0738779 and OCE 0727919), the National Basic Research Program of China (Grant No. 2004CB418404), and partially by the National Nature Science Foundation of China (Grant No. 40521002)     

The geobiological formation process of the marine source rocks in the Middle Permian Chihsia Formation of South China

The Chihsia Formation is one of the four sets of regional marine hydrocarbon source rocks from South China.In the past two decades,detailed geochemical and sedimentological studies have been carried out to investigate its origination,which have demonstrated that the high primary productivity plays a primary role in the deposition of sediments enriched in the organic matter.However,the mechanism of this high productivity and the path of the deposition and burial of the organic matter have always been a mystery.Based on the previous studies on the Shangsi Section in Guangyuan City,Sichuan Province,we proposed that the development of the equatorial upwelling due to the sea level rise is responsible for the relatively high productivity in the Chihsia Formation.The sea waters with high nutrient were transported by the sub-surface currents along the equator.High organic carbon flux was deposited on the deeper shelf,and then decomposed by bacteria,leading to the occurrence of anaerobic respiration.The metabolism of the microorganisms consumed the dissolved oxygen in waters,which was in favor of the preservation of the organic matter.This suggested geobiological model integrating with paleoclimatology,paleoceanography and geomicrobiology will help us to understand the causes of this particular sedimentary sequence.