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11.
Digital terrain analysis(DTA) is one of the most important contents in the research of geographical information science(GIS). However, on the basis of the digital elevation model(DEM), many problems exist in the current research of DTA in geomorphological studies. For instance, the current DTA research appears to be focused more on morphology, phenomenon, and modern surface rather than mechanism, process, and underlying terrain. The current DTA research needs to be urgently transformed from the study of landform morphology to one focusing on landform process and mechanism. On this basis, this study summarizes the current research status of geomorphology-oriented DTA and systematically reviews and analyzes the research about the knowledge of geomorphological ontology, terrain modeling, terrain derivative calculation, and terrain analytical methods. With the help of DEM data, DTA research has the advantage of carrying out geomorphological studies from the perspective of surface morphology. However, the study of DTA has inherent defects in terms of data expression and analytic patterns. Thus, breakthroughs in basic theories and key technologies are necessary. Moreover, scholars need to realize that DTA research must be transformed from phenomenon to mechanism, from morphology to process, and from terrain to landform. At present, the research development of earth science has reached the critical stage in which the DTA research should focus more on geomorphological ontology. Consequently, this study proposes several prospects of geomorphology-oriented DTA from the aspects of value-added DEM data model, terrain derivatives and their spatial relations, and macro-terrain analysis. The study of DTA based on DEM is at a critical period along with the issue on whether the current GIS technology can truly support the development of geography. The research idea of geomorphology-oriented DTA is expected to be an important exploration and practice in the field of GIS. 相似文献
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未来不同气候变化情景下我国玉米产量的初步预测 总被引:21,自引:0,他引:21
玉米是我国重要的粮食和饲料作物,研究气候变化对我国玉米产量的影响有重要意义。采用区域气候模式与CERES Maize模型相结合的方法,模拟了基准气候(BS,1961—1990年)和A2、B2两种温室气体排放方案下2011—2100年我国雨养和灌溉玉米产量,初步预测了未来不同气候情景下玉米产量的变化状况。结果表明,如果保持现有的玉米生产状况,气候变化将导致我国玉米主产区的玉米单产普遍降低,总产下降,给玉米生产带来一定经济损失。A2气候变化情景对我国玉米产量的负面影响要大于B2情景。CO2肥效作用可以在一定程度上缓解这种负面影响,其缓解作用对雨养玉米更明显。未来全国玉米主产区的雨养和灌溉玉米的稳产风险及低产出现的概率将会增大,总产的年际波动更剧烈。由于目前研究结果是未考虑农业生产的适应措施而得出的,可能会高估气候变化的负面影响。 相似文献
13.
地震波在热弹性介质中的衰减性质及其相应Q值的计算方法 总被引:1,自引:1,他引:0
该文得出热弹性介质中波的基本形式有准弹性纵波、横波和具有有限传播速度的温度波,并指出横波在传播过程中同其在完全弹性介质中一样是不衰减的,而准弹性纵波和温度波是相互伴随的、衰减的。其次,给出了具有两种不同传播速度的准弹性纵波的基本形式。最后,将地震P波看作由初始位移扰动的准弹性纵波,就固定频率和固定波长两种情况分别给出了相应Qr值的计算公式和近似公式。通常人们是利用多台的地震波资料在空间域中计算Qr值,而本文得到的时间域中Qr值的近似公式,为利用单台地震P波资料计算Qr值提供了一种方法。 相似文献
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区域可持续发展的一种评价模型:综合协调度——以广东省沿海城市为例 总被引:3,自引:0,他引:3
采用层次分析法(AHP)和主成分分析法建立了一种区域可持续发展定量评价的指标体系和综合协调度模型,确定了评价指标体系的权重,并根据广东省沿海14个地市1995年至2004年的统计数据,对其可持续发展综合协调度进行了定量评价。结果表明:(1)广东省沿海区域可持续发展的综合协调度总体上呈现上升趋势,但东中西部分布不均衡,呈现粤中较高东西两翼较低的格局;(2)14个沿海地市中,1995年综合协调度均处于较弱水平(Ⅳ),到2004年,只有深圳、广州的综合协调度超过0.4,达到中等协调水平(Ⅲ),而其它地市仍处于较弱水平(Ⅳ)的综合协调度阶段。 相似文献
17.
Diamonds have been discovered in mantle peridotites and chromitites of six ophiolitic massifs along the 1300 km‐long Yarlung‐Zangbo suture (Bai et al., 1993; Yang et al., 2014; Xu et al., 2015), and in the Dongqiao and Dingqing mantle peridotites of the Bangong‐Nujiang suture in the eastern Tethyan zone (Robinson et al., 2004; Xiong et al., 2018). Recently, in‐situ diamond, coesite and other UHP mineral have also been reported in the Nidar ophiolite of the western Yarlung‐Zangbo suture (Das et al., 2015, 2017). The above‐mentioned diamond‐bearing ophiolites represent remnants of the eastern Mesozoic Tethyan oceanic lithosphere. New publications show that diamonds also occur in chromitites in the Pozanti‐Karsanti ophiolite of Turkey, and in the Mirdita ophiolite of Albania in the western Tethyan zone (Lian et al., 2017; Xiong et al., 2017; Wu et al., 2018). Similar diamonds and associated minerals have also reported from Paleozoic ophiolitic chromitites of Central Asian Orogenic Belt of China and the Ray‐Iz ophiolite in the Polar Urals, Russia (Yang et al., 2015a, b; Tian et al., 2015; Huang et al, 2015). Importantly, in‐situ diamonds have been recovered in chromitites of both the Luobusa ophiolite in Tbet and the Ray‐Iz ophiolite in Russia (Yang et al., 2014, 2015a). The extensive occurrences of such ultra‐high pressure (UHP) minerals in many ophiolites suggest formation by similar geological events in different oceans and orogenic belts of different ages. Compared to diamonds from kimberlites and UHP metamorphic belts, micro‐diamonds from ophiolites present a new occurrence of diamond that requires significantly different physical and chemical conditions of formation in Earth's mantle. The forms of chromite and qingsongites (BN) indicate that ophiolitic chromitite may form at depths of >150‐380 km or even deeper in the mantle (Yang et al., 2007; Dobrthinetskaya et al., 2009). The very light C isotope composition (δ13C ‐18 to ‐28‰) of these ophiolitic diamonds and their Mn‐bearing mineral inclusions, as well as coesite and clinopyroxene lamallae in chromite grains all indicate recycling of ancient continental or oceanic crustal materials into the deep mantle (>300 km) or down to the mantle transition zone via subduction (Yang et al., 2014, 2015a; Robinson et al., 2015; Moe et al., 2018). These new observations and new data strongly suggest that micro‐diamonds and their host podiform chromitite may have formed near the transition zone in the deep mantle, and that they were then transported upward into shallow mantle depths by convection processes. The in‐situ occurrence of micro‐diamonds has been well‐demonstrated by different groups of international researchers, along with other UHP minerals in podiform chromitites and ophiolitic peridotites clearly indicate their deep mantle origin and effectively address questions of possible contamination during sample processing and analytical work. The widespread occurrence of ophiolite‐hosted diamonds and associated UHP mineral groups suggests that they may be a common feature of in‐situ oceanic mantle. The fundamental scientific question to address here is how and where these micro‐diamonds and UHP minerals first crystallized, how they were incorporated into ophiolitic chromitites and peridotites and how they were preserved during transport to the surface. Thus, diamonds and UHP minerals in ophiolites have raised new scientific problems and opened a new window for geologists to study recycling from crust to deep mantle and back to the surface. 相似文献
18.
通过对白象厂金矿的区域地质概况、矿区地质特征及控矿因素的分析研究,认为,白象厂金矿产于二长斑岩与玄武岩接触带上,局部赋存于二长斑岩与大理岩、玄武岩与大理岩的接触带上,呈脉状,似层状透镜状产出。矿化受构造及岩浆岩联合控制。矿床为构造破碎斑岩蚀变型金矿床。根据该矿床的控矿规律,认为沿金矿化带的走向和倾向方向上可能找到厚大、品位高的金矿体或金的次生富集体。 相似文献
19.
中外合作项目“喜马拉雅和青藏高原深剖面试验综合研究”取得重要进展MainProgressesinInternationalDeepProfilingOfTibetandtheHimalaya关键词喜马拉雅,青藏高原,深地震反射剖面“喜马拉雅和青藏高原... 相似文献
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