“21世纪海上丝绸之路”沿线国家水产品贸易网络分析     

彭飞  胡锦琳  伏捷  富宁宁 《热带地理》2021,41(6):1188-1198

水产品贸易是海洋经济的重要组成部分,是保证水产品有效供给、维护渔业产业链的重要措施。优化水产品贸易网络对保障中国粮食安全和扩展国际贸易具有重要意义。文章借助联合国商品贸易数据库,选取2000—2019年“21世纪海上丝绸之路”沿线国家水产品贸易数据,利用社会网络分析方法,测度“21世纪海上丝绸之路”沿线国家水产品贸易网络结构特征,进而分析沿线国家水产品贸易市场结构和产品结构。研究发现：1）2000—2019年“21世纪海上丝绸之路”沿线国家的水产品贸易变化可划分为2个阶段,其中第一阶段（2000—2008年）为平稳增长期,第二阶段（2009—2019年）为波动发展期。2）水产品贸易网络密度逐渐增大,空间集聚和网络凝聚力逐渐增强,网络的可达性不断提高,呈现小世界的特性。3）水产品贸易网络的核心—边缘结构较为稳定,核心国家的贸易联系紧密,贸易额占整体的一半以上,多边、双边贸易流存在差异,贸易网络的空间非均质性特征凸显;地理区位及距离对其组团有间接的影响,社团划分呈现层级性和地理临近组团的特点。4）水产品贸易网络的空间分异特性较为明显,重要节点国家主要集中在中国和东南亚国家,中间中心度高的国家和接近中心度排名靠前的国家具有趋同性,非洲东部及红海沿岸国家的网络中心性影响力较弱。5）在核心国家的水产品市场结构中,中国占据较大份额;国家间的关系变化引起市场结构发生调整;中国水产品进出口品种结构比较单一,进口和出口产品分别主要集中在冻鱼和水产品制品。  相似文献   

Activities of Parent Comets and Related Meteor Showers     

Jun-Ichi Watanabe  Mikiya Sato 《Earth, Moon, and Planets》2008,102(1-4):111-116

The activity of a meteor shower is thought to be proportional to the activities through time of the parent comet. Recent applications of the dust trail theory provide us not only with a new method to forecast the occurrences and intensities of shower activities, but it is also offers a new approach to explore the history of past activities of the parent comet by retro-tracking its associated meteor showers. We introduce the result of an effort for relating meteor shower activities to the parent comet activities for which we chose the October Draconids and comet 21P/Giacobini-Zinner in this paper.  相似文献   

21 世纪末珠江口深圳最高潮位重现期值预估     

聂宇华  汤超莲  程泽梅 《热带地理》2016,36(6):901-905

采用 P-III 适线拟合法分析赤湾验潮站建站以来的潮位资料,得出该站 1965―2014 年最高潮位的重现期值：其中 100 a 一遇最高潮位为 2.31 m,50 a 一遇最高潮位为 2.18 m。通过插值法分析 1965―2011 年赤湾站与北角/鰂鱼涌站的年最高潮位,得出两者存在显著相关关系,并据此后报出赤湾站近百年来 2 次最高潮位为 1962 年2.7 m 和 1937 年 2.34 m。。根据 IPCC AR5 中的 RCP2.6 方案,预估了 21 世纪末（2081―2100 年）赤湾最高潮位的重现期：100 a 最高潮位在全球海平面上升 0.24 m 的情况下为 2.55 m,在全球海平面上升 0.40 m 的情况下为 2.71m。并讨论了围海造地导致伶仃洋潮位上升率降低以及 0814 号台风“黑格比”对赤湾站增水的影响：赤湾北面西乡沿海地势特别低,当潮位≥1.40 m（珠基起算）时,就会发生海水倒灌现象。也就是说,未来海平面的上升将加大该区海水倒灌频率。通过分析台风过境时该站的潮位观测资料,得出 0814 号台风“黑格比”经过珠江口时赤湾站的最高潮位为增水 1.46 m。最后,重新修订了赤湾站最高潮位的重现期值,这不但能够提高该区域防台水位设计的准确性,还能为该海域的风暴潮预警预报提供参考依据。  相似文献   

渤海海域旅大21-A构造沙四段储集层特征及控制因素     

刘志刚  杜晓峰  王清斌  王军  王晓刚  郭涛 《海洋地质译丛》2012,(2):26-29,89

渤海海域旅大21-A构造在3600m以下的沙四段中发现了很好的油气显示,并且测试成功。沙四段在该构造是个新的油气勘探层系,具有很好的勘探前景。为了更好地研究该构造储集层情况,通过对该构造沙四段岩心、壁心资料,运用常规、铸体薄片鉴定和扫描电镜等化验分析资料,对该构造沙四段储集层基本特征进行了系统分析,认为该构造岩性主要以长石岩屑砂岩为主,岩屑长石砂岩次之,孔隙质量为中等一好,渗透率为特低渗～中渗,储集层物性中等。确定了影响储集层物性的主要因素为沉积作用、成岩作用和构造作用,三者综合影响着储集层的物性变化。  相似文献   

The Middle Triassic (Anisian) Otter Sandstone biota (Devon,UK): review,recent discoveries and ways ahead     

Robert A. Coram  Jonathan D. Radley  Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(3-4):294-306

The Middle Triassic (Anisian) Otter Sandstone was laid down mostly by braided rivers in a desert environment and is now well exposed along the south-east Devon coast in south-west England, part of the ‘Jurassic Coast’ World Heritage Site. It yields uncommon and generally fragmentary fossils, principally of vertebrates, including fish, temnospondyl amphibians and reptiles such as rhynchosaurs, predatory archosaurs, and small superficially lizard-like forms. These provide important information about a freshwater and terrestrial ecosystem that marks recovery from the end-Permian mass extinction, but pre-dated the appearance of dinosaurs and mammals. The constantly eroding Otter Sandstone exposures continue to reveal new taxa (for example, freshwater sharks). Furthermore, microvertebrate material obtained by sieving bone-bearing levels has the potential to further expand the faunal list. Newly discovered associated and articulated vertebrate remains, including small tetrapods, improve knowledge of whole-body anatomy and facilitate systematic work. Invertebrate burrows and reptile footprints provide information on ecological interactions and detailed bed-by-bed collecting casts light on taphonomic processes and faunal changes over time.  相似文献   

Evaluation of two spectral wave models for wave hindcasting in the Mackenzie Delta     

《Applied Ocean Research》2017

Climate change, reduced sea ice and increased ice-free waters over extended areas for longer summer periods potentially lead to increased wave energy in the Beaufort Sea (Wang et al., 2015; Khon et al., 2014) [1], [2], which is a major concern for coastal and offshore engineering activities. We compare two spectral wave models SWAN (Simulating WAves Nearshore) and MIKE 21 SW (hereafter MIKE21) in simulations of storm-generated waves in the Mackenzie Delta region of the southern Beaufort Sea. SWAN model simulations are performed using two nested grids system, whereas MIKE21 uses an unstructured grid system. Forcing fields are defined by hourly hindcast winds. Moving ice edge boundaries are incorporated during storm simulations. Modelled wave spectra from four storms are shown to compare well with field observations. Two established whitecapping formulations in SWAN are investigated: one dependent on mean spectral wave steepness, and the other on local spectral steepness. For the Beaufort Sea study area, we suggest that SWAN wave simulations using the latter local spectral steepness formulation are better than those using the former mean spectral steepness formulation. MIKE21 simulations also tend to agree with SWAN results using the latter whitecapping formulation.  相似文献   

Harnessing the wind: A case study of applying Flettner rotor technology to achieve fuel and cost savings for Fiji's domestic shipping industry     

《Marine Policy》2017

For over 5000 years, humans have successfully harnessed the power of wind to transport people and goods across the world's oceans. This research expands on previous studies of the unique Flettner rotor propulsion system and the demonstrable success in reducing fuel consumption and carbon dioxide (CO₂) emissions. Recent examples such as Enercon's E-ship 1 have proven seaworthy and economically viable along major shipping routes. The remote Pacific island countries (PICS), however, have the unique characteristics of retaining a remarkable seafaring heritage while remaining on the periphery of global commerce. With data obtained from a field study of Fiji's domestic shipping, this research analyzes the potential for implementing Flettner rotor systems to achieve more economically viable alternatives to the current situation. The findings show that with an incremental approach and the addition of a government fuel savings incentive, the Government Shipping Franchise Scheme (GSFS) subsidies could be significantly lowered for Fiji's ten uneconomical shipping routes. Four scenarios of 5%, 10%, 15%, and 25% fuel savings contrast the baseline data on one extreme with a zero-emissions scenario on the other. The most likely fuel savings scenario of between 10% and 15% results in a 20-year government savings of between 348,042 and 522,063 U.S. dollars and a 20-year cumulative reduction in CO₂ emissions of between 2931 and 4396 t. The paper concludes that Flettner rotors show promising results in reducing fuel consumption and CO₂ emissions and recommends future studies in collaboration with the Fiji government to develop practical strategies of implementation.  相似文献   

TheHI content of the Eridanus group of galaxies     

A. Omar  K. S. Dwarakanath 《Journal of Astrophysics and Astronomy》2005,26(1):71-87

The HI content of galaxies in the Eridanus group is studied using the GMRT observations and the HIPASS data. A significant HI deficiency up to a factor of 2–3 is observed in galaxies in the high galaxy density regions. The HI deficiency in galaxies is observed to be directly correlated to the local projected galaxy density, and inversely correlated to the line-of-sight radial velocity. Furthermore, galaxies with larger optical diameters are predominantly in the lower galaxy density regions. It is suggested that the HI deficiency in Eridanus is due to tidal interactions. In some galaxies, evidences of tidal interactions are seen. An important implication is that significant evolution of galaxies can take place in the group environment. In the hierarchical way of formation of clusters via mergers of groups, a fraction of the observed HI deficiency in clusters could have originated in groups. The co-existence of S0s and severely HI deficient galaxies in the Eridanus group suggests that tidal interaction is likely to be an effective mechanism for transforming spirals to S0s.  相似文献   

GMRTHI observations of the Eridanus group of galaxies     

A. Omar  K. S. Dwarakanath 《Journal of Astrophysics and Astronomy》2005,26(1):1-70

The GMRTHI 21 cm-line observations of galaxies in the Eridanus group are presented. The Eridanus group, at a distance of ≈ 23 Mpc, is a loose group of ≈200 galaxies. The group extends to more than 10 Mpc in projection. The velocity dispersion of the galaxies in the group is ≈240 km s⁻¹. The galaxies are clustered into different sub-groups. The overall population mix of the group is 30% (E + S0) and 70% (Sp + Irr). The observations of 57 Eridanus galaxies were carried out with the GMRT for ≈ 200 h. HI emission was detected from 31 galaxies. The channel rms of ≈ 1 mJy beam⁻¹ was achieved for most of the image-cubes made with 4 h of data. The corresponding HI column density sensitivity (3σ) is ≈ 1 × 10²⁰ cm⁻² for a velocity-width of ≈ 13.4 km s⁻¹. The 3σ detection limit of HI mass is ≈ 1.2 X 10⁷ Mpd for a line-width of 50 km s⁻¹. Total HI images, HI velocity fields, global HI line profiles, HI mass surface densities, HI disk parameters and HI rotation curves are presented. The velocity fields are analysed separately for the approaching and the receding sides of the galaxies. These data will be used to study the HI and the radio continuum properties, the Tully-Fisher relations, the dark matter halos, and the kinematical and HI lopsidedness in galaxies.  相似文献   

Physical controls on the dynamics of inlet sandbar systems     

E. Siegle  D. A. Huntley  M. A. Davidson 《Ocean Dynamics》2004,54(3-4):360-373

Knowledge of the physical processes acting at inlet systems and their interaction with sediments and sediment bodies is important to the understanding of such environments. The objectives of this study are to identify and assess the relative importance of the controlling processes across the complex sandbar system at the Teign inlet (Teignmouth, UK) through the combined application of a numerical model, field data and Argus video images. This allows the determination of the regions dominated by wave processes or by tidal processes and definition of the variability of these regions under different wave, tide and river-discharge conditions. Modelling experiments carried out for one stage of the evolution of the system show that the interaction between tidal motion and waves generates complex circulation patterns that drive the local sediment transport and sandbar dynamics, producing a cyclic morphological behaviour of the sandbars that form the ebb-tidal delta. The relative importance of each physical process on the sediment transport and consequent morphodynamics varies across the region. The main inlet channel is dominated by tidal action that directs the sediment transport as a consequence of the varying tidal flow asymmetry, resulting in net offshore transport. Sediment transport over the shoals and secondary channels at both sides of the main channel is dominated by wave-related processes, displacing sediment in the onshore direction. The interaction between waves and tide-generated currents controls the transport over the submerged sandbar that defines the channels seaward extend. High river discharge events are also proven to be important in this region, as they can change sediment-transport patterns across the area.Responsible Editor: Iris Grabemann  相似文献