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71.
72.
从实例出发,分析了避碰规则中经常出现的间隔和省略语法现象,如主语与谓语的间隔,谓语两个组成部分的分隔,以及长句中名词、介词短语和动词的省略等,旨在对航海英语教学和航海英语学习者有所启示。  相似文献   
73.
Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r2 = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (Ptot) and total nitrogen (Ntot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, Ptot and Ntot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution.  相似文献   
74.
以自建航海英语报刊语料库为基础,探讨如何在航海英语阅读教学中利用报刊英语语料库辅助教学,引导学生借助语境共现、词频表和关键词表等来进行英语学习,以达到快速掌握航海英语词汇,提高阅读速度和增强阅读理解能力,培养学生的跨文化交际意识等教学目标。  相似文献   
75.
李锋  李天杰 《极地研究》1997,9(4):61-65
利用地衣和苔藓化学分析资料对南极菲尔德斯半岛地区地衣和苔藓中化学元素的分配、相关性及其元素比值关系进行了分析。研究表明,地衣和苔藓促进了土壤与风化壳的发育,但受南极地区恶劣环境条件的限制,生物地球化学过程极其微弱。地衣和苔藓植株体中Fe、Al、Mn等元素丰度主要依赖于土壤与风化壳元素丰度的高背景值。Ca、K、Cr等元素是地衣选择性吸收较强的元素,苔藓对Mg、Na、Zn等元素则具有较强的选择性吸收能力。  相似文献   
76.
Contemporary variants of the lichenometric dating technique depend upon statistical correlations between surface age and maximum lichen sizes, rather than an understanding of lichen biology. To date three terminal moraines of an Alaskan glacier, we used a new lichenometric technique in which surfaces are dated by comparing lichen population distributions with the predictions of ecological demography models with explicit rules for the biological processes that govern lichen populations: colonization, growth, and survival. These rules were inferred from size–frequency distributions of lichens on calibration surfaces, but could be taken directly from biological studies. Working with two lichen taxa, we used multinomial‐based likelihood functions to compare model predictions with measured lichen populations, using only the thalli in the largest 25% of the size distribution. Joint likelihoods that combine the results of both species estimated moraine ages of ad 1938, 1917, and 1816. Ages predicted by Rhizocarpon alone were older than those of P. pubescens. Predicted ages are geologically plausible, and reveal glacier terminus retreat after a Little Ice Age maximum advance around ad 1816, with accelerated retreat starting in the early to mid twentieth century. Importantly, our technique permits calculation of prediction and model uncertainty. We attribute large confidence intervals for some dates to the use of the biologically variable Rhizocarpon subgenus, small sample sizes, and high inferred lichen mortality. We also suggest the need for improvement in demographic models. A primary advantage of our technique is that a process‐based approach to lichenometry will allow direct incorporation of ongoing advances in lichen biology.  相似文献   
77.
杨霄 《地理学报》2023,78(1):230-240
就军事地理环境而言,当代中国在海洋方向面临的最主要威胁来自环中国岛链的封锁,研究这一限制性地理环境对准备和实施军事活动的影响与相应对策,具有重要的现实意义。第一次世界大战(简称“一战”)初期,德国东亚驻军进行了跨岛链作战的实践,但在日本海军依托岛链和优势兵力的封锁下,其战略目标未能达成,并且出现了军事地理位置上的优劣转换。本文通过对“一战”初期德国东亚驻军跨岛链作战行动的军事地理分析,尝试提出军事地理研究思路、跨学科融合路径和分析框架。本文分析认为,彼时德占青岛虽然具有良好的战略态势和强大的军事力量,但孤悬海外,且缺乏战略纵深;从宏观的区域尺度分析来看,基地与舰队间的联系被岛链分隔,腹背受敌,军事地理上的劣势凸显。但依托岛链进行封锁,需要集结大量兵力,利用对方边缘区内作战力量相对比较薄弱的有利条件,原本实力较弱的德国东亚舰队取得了重大战果,形成反转式的“核心—边缘”结构。本文为中国的海疆安全和海洋强国建设提出了5条建议。  相似文献   
78.
In Alaska, lichenometry continues to be an important technique for dating late Holocene moraines. Research completed during the 1970s through the early 1990s developed lichen dating curves for five regions in the Arctic and subarctic mountain ranges beyond altitudinal and latitudinal treelines. Although these dating curves are still in use across Alaska, little progress has been made in the past decade in updating or extending them or in developing new curves. Comparison of results from recent moraine-dating studies based on these five lichen dating curves with tree-ring based glacier histories from southern Alaska shows generally good agreement, albeit with greater scatter in the lichen-based ages. Cosmogenic surface-exposure dating of Holocene moraines has the potential to test some of the assumptions of the lichenometric technique and to facilitate the development of a new set of improved lichen dating curves for Alaska.  相似文献   
79.
Data are reported demonstrating the potential role of microscale morphologies, induced by endolithic lichen communities, specifically Verrucaria baldensis, in the initiation and development of mesoscale solution basin formation on limestone in the Burren, County Clare. A biophysical model is proposed outlining the different microscale stages leading to solution basin initiation with a progression from initial lichen colonization and growth, associated perithecial biopitting followed by biopit coalescence to form biotroughs, their subsequent enlargement and eventual incipient solution basin formation. This model provides one explanation for solution basin development as this end state may also be achieved through simple solutional means without biological input. The complexity of interactions at the lichen–rock interface are identified with emphasis on the spatial and temporal variability of these underlining the point that, as with macrotopographies at the landscape scale, rock surface microtopographies also reflect historical weathering legacies. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
80.
中国海洋产业的结构与布局研究展望   总被引:3,自引:0,他引:3  
海洋产业结构与布局是海洋经济地理学研究的核心领域与主体内容,国内相关文献日益丰富,但海洋产业结构与布局研究尚未形成完整体系。梳理现有文献发现:国内研究存在起步晚、发展缓慢,高层次研究成果少且增长慢,以区域实证研究为主、理论创新研究较少等问题,现有研究集中在6方面:①海洋产业结构与布局的内涵、规律及其与陆域布局差异探索;②沿海省份或大城市海洋产业结构的现状与问题、结构优化与主导产业选择、产业结构绩效评价、竞争力与趋势研究;③区域海洋产业布局模式及优化政策支撑体系研究;④海洋资源与环境的产业承载力评价及海洋功能区划研究;⑤海洋产业集群,尤其是港航集群的初步探索;⑥国外海洋产业发展态势、统计标准与区域海洋产业合作探索。本文初步总结了国内对海洋产业结构与布局研究文献的增长规律,并立足于海洋产业结构与布局研究趋势,指出未来应加强海洋产业结构与布局的前沿领域及理论体系探索,并为我国海洋经济示范区建设提供科学指导。  相似文献   
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