基于空间自回归和空间聚类的渔情预报模型

作者针对远洋渔场渔情预报精度偏低的问题,提出一种基于空间自回归和空间聚类的渔情预报模型。该模型利用空间自回归对收集到的渔业历史数据进行预处理,然后通过空间聚类将所有数据样本根据地理位置分划成若干个区域,最后研究每个区域中环境数据与渔获数据之间的数学关系,各自建立栖息地适宜性指数模型(Habitat Suitability Index,HSI),并以印度洋大眼金枪鱼(Thunnus obesus)为例进行验证。结果表明,本模型的均方差为0.1742,与传统线性回归方法的均方差0.2363相比,能更好地表达海洋环境数据与渔获量之间的关系,预测精度显著提高。     

Modelling the effects of motion on primary production in the mixed layer of lakes

A model of the time dependent relationship between productivity and light intensity following changes in light intensity is briefly described. The model incorporates two response timescales simulating initial response and photoinhibition, although additional timescales could easily be incorporated. The model is calibrated against one set of time dependent data, and applied to two simple models of motion in the upper mixed layer of a lake. The two models are: organised motion simulating Langmuir cells, and disorganised motion simulating the turbulent velocity field associated with surface wind stirring. The depth and therefore light histories for a number of photosynthesising particles are calculated by these models, and used by the productivity model to calculate mean productivities. The results show that the influence of the time dependent nature of the productivity relationship depends on the ratio of the mixed layer depth to the euphotic depth, and to a less extent, on the rate at which the particles circulate in the mixed layer.     

Mixed layer depth climatology of the North Pacific based on Argo observations

A monthly mean climatology of the mixed layer depth (MLD) in the North Pacific has been produced by using Argo observations. The optimum method and parameter for evaluating the MLD from the Argo data are statistically determined. The MLD and its properties from each density profile were calculated with the method and parameter. The monthly mean climatology of the MLD is computed on a 2° × 2° grid with more than 30 profiles for each grid. Two bands of deep mixed layer with more than 200 m depth are found to the north and south of the Kuroshio Extension in the winter climatology, which cannot be reproduced in some previous climatologies. Early shoaling of the winter mixed layer between 20–30°N, which has been pointed out by previous studies, is also well recognized. A notable feature suggested by our climatology is that the deepest mixed layer tends to occur about one month before the mixed layer density peaks in the middle latitudes, especially in the western region, while they tend to coincide with each other in higher latitudes.     

Defining dynamic pelagic habitats in oceanic waters off eastern Australia

Although many species in the pelagic ocean are widespread, they are not randomly distributed. These species may have associations with particular water masses or habitats, but to best understand patterns in the ocean, these habitats must be identified. Previous efforts have produced static or seasonal climatologies, which still represent smearing over habitats. The Eastern Tuna and Billfish Longline Fishery (ETBF) targets a range of high trophic level species in oceanic waters off eastern Australia. In this study, dynamic ocean habitats in the region were identified for each month based on cluster analysis of five oceanographic variables averaged at a monthly time scale and a spatial scale of 0.5° for the period 1995-2006. A total of seven persistent habitats were identified off eastern Australia with intra and interannual variation in size and location, indicating the importance of spatial and temporal variation in the dynamics of the region. The degree to which these dynamic habitats were distinguished was tested using (i) stable isotope analysis of top fish predators caught in the region and (ii) estimates of variation in estimated abundance generated from catch data from the fishery. More precise estimates (measured as lower total CV) of isotopic values from swordfish (Xiphias gladius), yellowfin tuna (Thunnus albacares) and albacore (Thunnus alalunga) were obtained for 4 of 6 isotope comparisons using the dynamic habitat groupings, which indicate that stratifying by pelagic habitat improved precision. Dynamic habitats produced more precise abundance estimates for 7 of 8 large pelagic species examined, with an average reduction in total CV of 19% compared to when abundance was estimated based on static habitat stratification. These findings could be used to guide development of effective monitoring strategies that can distinguish patterns due to environmental variation, and in the longer term, climate change.     

Fifty-five-year longevity for the largest member of the family Sparidae: the endemic red steenbras Petrus rupestris from South Africa

A previous study that explored the age and growth of red steenbras Petrus rupestris (Valenciennes, 1830), a large sparid (family Sparidae, seabreams or porgies) endemic to South Africa and reported to approach 2 m in length, provided estimates as a moderately slow-growing species with a maximum age near 30 years. The stock is considered collapsed and a fishing moratorium was imposed in 2012, resulting in this species being assessed as Endangered by the IUCN. One consideration in addressing population status is validation of life-history traits. In this study, estimates of age for red steenbras from thin-sectioned otoliths were reassessed visually in terms of both the original ages and revised estimates using a different age-reading pattern. The revised ages exceeded the original ages by up to 30 years, with a maximum estimated age of 55 years from a well-defined otolith section that provided a basis for the revised age-reading procedure. Bomb radiocarbon (¹⁴C) dating revealed there was an offset in the timing of the ¹⁴C rise on the Agulhas Bank that, when coupled with considerations for regional oceanography, provided support for the revised age-reading pattern and an estimated longevity that exceeds 50 years. These findings were further supported by the fortuitous recapture of a tagged red steenbras that was at liberty for 22 years.     

湖南石门杨家坪下寒武统杷榔组三段混合沉积研究

湖南石门杨家坪下寒武统杷榔组三段发育陆源碎屑与海相碳酸盐的混合沉积。综合前人研究成果,通过对研究区野外露头资料的详细观测和室内样品分析及数据统计等工作,对研究区杷榔组三段混合沉积进行了详细的研究。研究区混合沉积特征宏观上表现为由陆源碎屑与混积物交互沉积、碳酸盐与混积物交互沉积和不同类型混积物本身的交互沉积构成的混积层系,微观上表现为陆源碎屑组分与碳酸盐组分混合沉积所形成混积岩;混合沉积类型主要为内潮汐沉积作用和浊流沉积作用形成的复合式混合沉积Ⅱ,次为深水原地沉积作用形成的渐变式混合沉积,但是不同成因的沉积作用形成的混合沉积类型往往叠加在一起,形成复合式混合沉积Ⅱ+渐变式混合沉积的混合沉积复合体;混合沉积环境为深水斜坡,发育内波、内潮汐混合沉积微相、深水原地混合沉积微相和远源浊流混合沉积微相等类型;在沉积环境分析的基础上,根据内波、内潮汐沉积特征,剖析了混合沉积的沉积机理;结合混合沉积的成因、沉积机理、产出部位及沉积环境等因素,以沉积学原理为指导,建立了研究区杷榔组三段的混合沉积模式。     

北京土地利用混合度对居民职住分离的影响

市场经济体制改革以来,中国城市土地利用方式发生巨大变化,深刻影响居民日常生活。尽管国内外学者关注土地利用方式对居民通勤行为的影响,然而其研究方法均采用简单的单层模型,未能将数据的多层嵌套关系纳入模型中。为解决这一问题,本文采用多层线性模型(Multilevel Models),以北京为例,同时分析了在居住地和工作地层级上的街道土地利用混合度对居民职住分离的影响,以及居民住房情况和社会经济属性对其职住分离的影响。研究结果表明,微观层面的土地利用混合度的提升的确有利于减轻个体的职住分离;个体所在的工作地土地利用方式也对其职住分离产生影响,而且工作地对个体的影响要比居住地的影响更大;居民的社会经济属性、住房情况等对其职住分离程度存在显著的影响;交叉分类多层线性模型适用于解决存在复杂嵌套关系的影响因素分析。     

考虑三向应力效应的最大Mises应力复合断裂判据

通过对脆性断裂过程中开裂扩展机理的分析,提出了径向平面最大Mises应力(RPMS)概念。在平面应变条件下考虑泊松比的影响,对不同应力复合比的I-II复合型载荷作用下裂尖处应力分布进行了分析,以此为基础,考虑裂尖处三向应力状态对断裂过程的影响,将径向平面上的最大Mises应力作为裂纹开裂扩展的控制因素。据此,针对复合型载荷模式,提出了裂尖复合脆性断裂判据及裂纹开裂方向表达式。将计算结果与现有试验或其他理论进行了对比分析,以此验证了该径向平面上最大Mises应力断裂判据的合理性。     

黑龙江伊春红山华夏—安加拉混生植物群

系统研究了黑龙江省伊春红山地区晚二叠世红山组植物群,认为其性质为华夏—安加拉混生植物群。华夏植物区与安加拉植物区的界限,应以内蒙古陆及其东、西延展部分为界。