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当前天然橡胶产业持续低迷,追踪国际天然橡胶研究前沿热点对于我国天然橡胶产业发展和升级具有重要参考价值。本研究采用科学计量方法结合CiteSpace技术,对Web of Science数据库的天然橡胶文献进行共被引、共词和聚类分析,概述了该领域重要的基础文献,揭示其学科领域研究前沿和热点。结果表明,共探测出6个前沿热点,高度聚合在三大学科领域。其中,在化学与材料科学领域,领先优势十分明显,共遴选出4个前沿热点：（1）功能化改性石墨烯或氧化石墨/天然橡胶纳米复合材料;（2）生物基体/天然橡胶纳米复合材料;（3）弹性体或天然橡胶纳米复合材料的应变诱导结晶行为;（4）废旧橡胶的自修复与回收加工。在生物科学领域,遴选出1个前沿热点,即橡胶树基因组测序、橡胶生物合成路径与关键基因。在生态与环境科学领域,遴选出1个前沿热点,即橡胶林的扩张及其对生态环境的影响。高频和高突现关键词在三大学科呈现由多到少分布,反映了当前天然橡胶研究领域发展趋于多方向性,但其前沿热点相对集中在天然橡胶全产业链的下游。 相似文献
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Donald B. Olson 《Fisheries Oceanography》2001,10(2):133-150
The nature of the western portions of the biogeographic temperate or transition zones in the North Pacific and North Atlantic is reviewed. The physical transport of nutrients and biomass into them from the Kuroshio and Gulf Stream as well as from the poleward sides are estimated. The conclusion is that the upwelling in the two western boundary currents makes the largest contribution to the nutrient and biomass fluxes into these transition zones. A conservative estimate of the amount of upwelled fluid is derived from absolute velocity sections in the Gulf Stream. The estimate suggests that upwelling into the euphotic zone exceeds 2 × 106 m3 s–1. This implies that upwelling in these western boundary currents matches or exceeds that in eastern boundary currents such as the California Current. The two western boundary regimes have very different poleward situations. The Oyashio extension flows parallel to the Kuroshio and is a deep current. The North Atlantic Shelf Front flow is to the west where it is ultimately entrained into the edge of the Gulf Stream. There does not seem to be any tendency for this to occur in the Kuroshio. Despite these differences in the northern and western boundaries, the two transition zones are similar with large amplitude meanders, anticyclonic rings and streamers dominating their physical structure. The physical features responsible for the transfer of materials from the boundary current extensions into the transition zones are similar in both systems. Ring formation contributes only ? 10% of the transfer, while ring‐induced streamers contribute 30%. The rest of the transport is contributed by branching of the boundary current front. Both currents have well developed secondary fronts consisting of subtropical surface water pulled into the transition zone. Biologically, the upwelling in both western boundary currents leads to a biomass maximum along the boundary in both secondary producers (copepods) and in small pelagic fish. In the Kuroshio, the latter are the Japanese sardine, Sardinops melanostictus, that spawn in the Kuroshio and then enter the transition zone for the summer and fall months. In the Gulf Stream, the dominate species are menhaden, Brevoortia tyrannus and B. smithi. These species make use of the coastal environments of North America and although the adults spawn in the Gulf Stream, they are not thought to play a major role in the Slope Water, transition zone. The similar differences in the use of the Kuroshio and the Gulf Stream ecosystems occurs in the behaviour of bluefin tuna, squid and other large pelagics. The Gulf Stream system also lacks an equivalent to Pacific saury, Cololabis saira. The biology therefore is at least subtly different, with saury and sardines being replaced by mid‐water fish in the North Atlantic. A fuller comparison of the biology with quantitative methods in both systems should be encouraged. 相似文献
3.
Fishery‐linked aerial surveys for bluefin tuna (Thunnus thynnus) were conducted in the Gulf of Maine (GOM) from July through October, 1994–96. Each year, from 507 to 890 surface schools were detected and their locations examined in relation to oceanographic conditions. Correlations between bluefin tuna presence and environmental variables were explored for sea surface temperature (SST), distance to a SST front, frontal density (relative density of all SST fronts seen in a given 1 km area for 2 weeks prior to each tuna sighting), and bottom depth and slope. Mean SST associated with bluefin schools was 18.1°C (±2.8). Schools were located at a mean distance of 19.7 km (±19.6) from SST fronts, and in water masses with an average frontal density of 28.2 m km?2 (±35.7). Mean bottom depth of detected schools was 139.0 m (±70.3), and mean bottom slope was 0.7% rise (±0.7). A binomial generalized linear model fit to these variables indicated that bluefin are seen closer to fronts than locations in which no tuna were seen. Using simple and partial Mantel tests, we investigated the spatial correlation between bluefin tuna presence and the environmental variables, controlling for spatial autocorrelation. For each day that schools were sighted, we performed 24 Mantel tests, on a combination of response and predictor variables. The spatial relationship between bluefin tuna and SST fronts was inconsistent. Our analysis identified significant spatial structure in the bluefin school locations that had no significant correlation with any of the measured environmental features, suggesting that other untested features, such as prey density, may be important predictors of bluefin distribution in the GOM. 相似文献
4.
1. All reserve designs must be guided by an understanding of natural history and habitat variability. 2. Differences in scale and predictability set aside highly dynamic pelagic systems from terrestrial and nearshore ecosystems, where wildlife reserves were first implemented. Yet, as in static systems, many pelagic species use predictable habitats to breed and forage. Marine protected areas (MPAs) could be designed to protect these foraging and breeding aggregations. 3. Understanding the physical mechanisms that influence the formation and persistence of these aggregations is essential in order to define and implement pelagic protected areas. We classify pelagic habitats according to their dynamics and predictability into three categories: static, persistent and ephemeral features. 4. While traditional designs are effective in static habitats, many important pelagic habitats are neither fixed nor predictable. Thus, pelagic protected areas will require dynamic boundaries and extensive buffers. 5. In addition, the protection of far‐ranging pelagic vertebrates will require dynamic MPAs defined by the extent and location of large‐scale oceanographic features. 6. Recent technological advances and our ability to implement large‐scale conservation actions will facilitate the implementation of pelagic protected areas. 7. The establishment of pelagic MPAs should include enforcement, research and monitoring programmes to evaluate design effectiveness. 8. Ultimately, society will need a holistic management scheme for entire ocean basins. Such overarching management will rely on many innovative tools, including the judicious use of pelagic MPAs. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
5.
提出并研究了非线性项含有时滞且以卷积形式出现的扩散 Musca domestica 苍蝇模型,重点考察了该模型连结两一致稳态解的波前解的存在性。利用几何奇异摄动理论,证明了对一类特定形式的卷积核,只要时滞充分小,该模型的波前解仍然能得以保持。 相似文献
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PETER MUNK CLIVE J. FOX LOES J. BOLLE CINDY J. G. van DAMME PETTER FOSSUM GERD KRAUS 《Fisheries Oceanography》2009,18(6):458-469
Spawning of fishes takes place across a wide area of the North Sea. However, more intense spawning is seen in restricted areas, indicating that such areas present favorable conditions. To update information on fish spawning in the North Sea and analyze potential linkages to hydrographic characteristics, an internationally coordinated survey was conducted in the winter/spring of 2004. Oblique hauls for fish eggs and larvae and vertical profiles of temperature and salinity were carried out at 393 stations across the entire North Sea. The hydrography was strongly influenced by the interfacing of water masses of different salinity, and frontal zones were seen along all coastal areas and off the Dogger and Fisher Banks. Total abundances of eggs and larvae, including fish species such as cod, haddock, plaice, long rough dab and sandeel, peaked in the vicinity of the frontal areas. Hence our findings indicate that the main spawning locations of fish are linked to recurrent hydrographic features such as salinity fronts. Such a linkage may provide survival advantages, as the fronts present favorable feeding conditions, and the related physical processes may confine egg and larval dispersal and transport them towards suitable nursery habitats. 相似文献
8.
Steven G. Wilson 《Fisheries Oceanography》2004,13(4):283-286
Schools of up to 50 basking sharks (Cetorhinus maximus) were observed on the warm side of a persistent thermal front in the southern Gulf of Maine from early September through mid‐October 2002. Aerial photographs showed a variety of schooling patterns, including echelon, cartwheel and milling formations. While the function of these aggregations remains unknown, they may represent group courtship behaviour. 相似文献
9.
供水压力对微孔陶瓷渗灌土壤水分运移的影响 总被引：1，自引：0，他引：1
为探明供水压力对微孔陶瓷灌水器灌水条件下土壤水分运移规律的影响,通过室内土箱模拟试验,研究了3个压力水平下的微孔陶瓷灌水器灌水时的土壤水分入渗特征。研究结果表明,微孔陶瓷灌过程中,供水压力是决定土壤水分初始入渗速率和累计入渗量的关键因素,且供水压力越大,土壤水分初期入渗速率越大,最终累计入渗量也越大;微孔陶瓷渗灌形成的湿润体轮廓为上下不对称的椭球体,湿润锋在各方向上的运移距离与时间呈幂函数关系,其中入渗向上距离水平距离向下距离,供水压力越大,水平最大入渗半径距离灌水器底部距离越远;供水压力对土壤含水分分布影响较大,供水压力越大,灌水器周围含水率越高,高含水率区域越大。在各供水压力水平下,微孔陶瓷渗灌形成的湿润体大小和含水率均能满足作物根系吸水需求。 相似文献
10.
Coupling an oceanographic model to a Fishery Observing System through mixed models: the importance of fronts for anchovy in the Adriatic Sea 
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下载免费PDF全文 Piera Carpi Michela Martinelli Andrea Belardinelli Aniello Russo Enrico Arneri Alessandro Coluccelli Alberto Santojanni 《Fisheries Oceanography》2015,24(6):521-532
Anchovy, Engraulis encrasicolus, forms the basis of Italian small pelagic fisheries in the Adriatic Sea. The strong dependence of this stock on environmental factors and the consequent high variability makes the dynamics of this species particularly complicated to model. Weekly geo‐referenced catch data of anchovy obtained by means of a Fishery Observing System (FOS) from 2005 to 2011 were referred to a 0.2 × 0.2 degree grid (about 20 km2) and associated with the environmental parameters calculated by a Regional Ocean Modelling System, AdriaROMS. Generalized Additive Mixed Models (GAMM) with and without random effects were used to identify a relationship between abundance in the catch and oceanographic conditions. The outcomes of models with no random effects, with random vessel effects and with the random vessel and random week‐of‐the‐year effects were examined. The GAMM incorporating a random vessel and week‐of‐the‐year effect were selected as the best model on the basis of the Akaike information criteria (AIC). This model indicated that catches (abundance) of anchovy in the Adriatic Sea correlate well with low temperatures, salinity fronts and sea surface height, and allowed the identification of areas where high concentrations of this species are most likely to occur. The results of this study demonstrate that GAMM are a useful tool to combine geo‐referenced catch data with oceanographic variables and that the use of a mixed‐model approach with spatial and temporal random effects is an effective way to depict the dynamics of marine species. 相似文献