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81.
南黄海中部泥质沉积成因和物源研究综述   总被引:1,自引:0,他引:1  
当前南黄海沉积学研究的核心问题是泥质沉积的形成过程和动力机制及其物质来源。许多学者对南黄海中部泥区的成因和物源进行了大量研究,但比较局限,缺少系统性。现有研究认为南黄海泥质沉积的形成受黄海冷水团和上升流的影响,但黄海冷水团并不是其形成的必要条件。对泥区物源的研究,主要考虑现代黄河物质、老黄河物质以及长江物质对其的影响,并且仅是定性的研究。对于朝鲜半岛物质对南黄海中部泥区的影响,国内的研究更是寥寥无几。海水对海底基岩的侵蚀沉积以及黄海暖流对海底沉积物的改造和再悬浮作用对南黄海中部泥区沉积的贡献仅是个别学者的观点。  相似文献   
82.
根据蓄冰中央空调的控制要求设计了一个基于西门子可编程逻辑控制器(PLC)的两级监控系统,现场工作站由PLC与触摸屏组成,作为现场监控及数据采集平台;管理工作站由工控计算机和打印机组成,作为主要的人机界面(HMI),除能打印数据及远程监控现场工作站外,还具有现场工作站的所有功能。实际运行结果表明,设计的监控系统能实时监视和控制蓄冰中央空调状态,有效地提高空调系统的制冷量及制冷效率。  相似文献   
83.
The glacially carved central coast of Maine is incised by river systems with interconnecting channels, offshore-trending submarine ridges, and narrow passages between nearshore islands and headlands. The tidal range exceeds 3 m, leading to complex and vigorous circulation patterns with strong flows in narrow channels, near river mouths, and between islands. The spongiform coastal morphology allows enhanced exchange between offshore waters, estuaries and internecine bays, resulting in rapid dispersal of nutrients, larvae and contaminants throughout the region. A fine-grid numerical circulation model has been used to examine the influences of the tides, river flows and winds on the dispersion of lobster larvae and pollutants in the nearshore and riverine environment. This paper describes the model application, presents a few salient features of the circulation patterns, and examines some implications for the coastal environment. For example, under realistic tides and variable southwest summer winds, about 80% of neutral near-surface particles introduced near the offshore islands (a proxy for stage IV lobster larvae from offshore sources) remain within a few km of the islands over a two-week period. On the other hand, a persistent, periodic sea breeze can remove more than two-thirds of the particles from the domain over the same period. Tidal mixing disperses pollutants entering the upper Kennebec River to the offshore and through internecine passages in about one week.  相似文献   
84.
简单评述了现有各种版本的大气折射表所依据的理论基础和编制方法,指出了实测大气折射值、建立随地形而异的实测大气折射模型的必要性和应具备的基本条件;在分析了长期以来不能直接测定大气折射值的原因后,介绍了一种在不同方向精确测定大气折射值和建立观测点大气折射模型的新方法,以及所依赖的观测仪器具备的特性,最后给出了用实测数据建立的本地大气折射模型。  相似文献   
85.
晁勐  张俊  刘翔 《干旱区地理》2022,45(6):2004-2012
以2021年兰州市主城区678个居住小区房价数据为基础,引入地理场模型量化影响房价的外部因素,通过空间自相关分析、多尺度地理加权回归等模型对房价分异的空间格局及驱动因素的作用机理、带宽差异展开研究,以期为推动河谷型城市房产市场的公平发展提供参考。结果表明:(1)兰州市主城区平均房价为13739元·m-2,空间上呈现“一主三副”的带状多中心组团式分布格局,房价由多中心向四周递减,价格相似的小区在地理空间上邻近分布,具有“小集中、大分散”的局部空间特征。(2)房价分异是多种驱动因素共同作用的结果,区位特征中的主商圈对房价的影响居于首位,建筑特征中的房龄、容积率和邻里特征中的中学数量、绿化率等对房价的影响较大,城市地理特征对房价具有显著影响,愈靠近黄河的小区、房价越高。(3)各驱动因素的带宽差异明显,主商圈、医院等小尺度变量存在高度空间异质性,而容积率、黄河等全局变量基本不存在空间异质性。  相似文献   
86.
为进一步探明陇中黄土高原区旱地春小麦产量形成对不同干旱胁迫的响应机制,依据甘肃省定西市安定区凤翔镇安家沟村2016—2018年大田控水试验数据以及定西市安定区1971—2018年气象数据,验证农业生产系统模拟(Agricultural production systems simulation,APSIM)模型模拟不同...  相似文献   
87.
The Arunta Inlier is a 200 000 km2 region of mainly Precambrian metamorphosed sedimentary and igneous rock in central Australia. To the N it merges with similar rocks of lower metamorphic grade in the Tennant Creek Inlier, and to the NW it merges with schist and gneiss of The Granites‐Tanami Province. It is characterized by mafic and felsic meta‐igneous rocks, abundant silicic and aluminous metasediments and carbonate, and low‐ to medium‐pressure metamorphism. Hence, the Arunta Inlier is interpreted as a Proterozoic ensialic mobile belt floored by continental crust. The belt evolved over about 1500 Ma, and began with mafic and felsic volcanism and mafic intrusion in a latitudinal rift, followed by shale and limestone deposition, deformation, metamorphism and emergence. Flysch sedimentation and volcanism then continued in geosynclinal troughs flanking the ridge of meta‐igneous rocks, and were followed by platform deposition of thin shallow‐marine sediments, further deformation, and episodes of metamorphism and granite intrusion.  相似文献   
88.
滇中郝家河砂岩铜矿的地球化学及其成因意义   总被引:1,自引:0,他引:1  
秦德先  马宏 《地质论评》1994,40(2):183-192
本文论术字滇中生代地层与矿区及春外围马头山组中铜的时空分布与迁移富集规律,揭示了矿床的沉积-后期叠加改造成因。成矿作用经历了同生沉积形成矿源层,后期叠加改造形成矿体的过程。后期改造中铜元素发生了大量迁移,矿质主要来自矿体之下伏紫色矿源层。  相似文献   
89.
Hideo  Horikawa 《Island Arc》1994,3(4):309-328
Abstract The well preserved cranium of Protodobenus japonicus, a new genus and species of odobenine walrus, is from the lower part of the Tamugigawa Formation at Ooshima-mura, Higashi Kubiki-gun, Niigata Prefecture, central Japan. The lower part of the formation that yielded P. japonicus is Early Pliocene, dating approximately from 5.0 to 4.9 Ma. The skull of P. japonicus is generally shaped like that of the modern walrus, Odobenus rosmarus (Linnaeus, 1758), but is much more primitive, especially in the dentition. Protodobenus japonicus is derived from the Imagotariinae. It is similar to such primitive fossil walruses as Prorosmarus alleni from the Western Atlantic and Aivukus cedrosensis from Baja California, and has some similarities as well as significant differences from them. Protodobenus japonicus could have evolved directly into Odobenus in the North Pacific Ocean, and could have dispersed directly to the Arctic Ocean. This is contrary to the scenario proposed by Repenning and Tedford, in which primitive odobenids, like Aivukus cedrosensis, migrated to the Atlantic Ocean through the Central American Seaway and returned to the North Pacific Ocean as O rosmarus via the Arctic about 0.6 Ma. Regarding the first lower premolar of the living walrus, Fay concluded after studying fetal O. rosmarus that the first premolar (P1) of the mandible is absent, and that the lower tooth row consists of: C1 P2, P3, P4. Protodobenus japonicus has in its mandible I 1-2 C1 P2, P3, P4, and this is the primitive pinniped formula. Pinnipeds typically lose the molars, not the anterior premolars, and the present author believes that the correct tooth formula for O rosmarus is C1 P1, P2, P3. Its skull, palate, and mandible suggest that P. japonicus had morphology pre-adapted to an early stage of benthic suction feeding, but it probably was unable to rely on that method of feeding. The discovery of P. japonicus demonstrates that the odobenine lineage (true walruses) goes back in time at least 5 Ma. Other more aberrant odobenine walruses, such as Aivukus and Prorosmarus, and pseudo-walruses of the subfamily Dusignathinae, are more distantly removed from the lineage leading to living walruses than has previously been suspected.  相似文献   
90.
The influence of the attenuation model used in seismic hazard assessment in terms of intensity and acceleration is studied. For two sites in central Italy, the catalogue of the actual observed intensities during the last three centuries has been recovered. In the study region, the data collected during a recent seismic sequence give the basis for relating intensity and acceleration. The results show the importance of establishing statistical relationships among the used quantities, based on a representative set of data.  相似文献   
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