Population structure, size at maturity and condition of sardine, Sardina pilchardus (Walb., 1792), in the nursery ground of the eastern Adriatic Sea (Krka River Estuary, Croatia)

A total of 1125 specimens of sardine, Sardina pilchardus, ranging in total length from 4.9 to 12.5 cm (mean 8.31 ± 1.41 cm) and in weights between 1.02 g and 11.18 g (mean 4.40 ± 1.87 g) were randomly sampled using a beach seine from the Krka River estuary. Samples were collected monthly according to their occurrence in this area from October to February during 2002/03, 2003/04 and 2004/05, which is during the spawning period of this species. Monthly fluctuations in the length frequency distributions of sardine were observed during that time. The length–weight relationship of all sardine specimens was described by the equation: W=0.007L^2.9587(r² = 0.9626); and the isometric nature of relative growth was established (t = −5.1495; p < 0.05). According to the allometric condition factor K_a, sardine specimens were in better somatic condition at the beginning of their appearance (spawning period) in the Krka River estuary. The length at which 50% of sardines were mature (L₅₀) was calculated to be 7.9 cm.     

Small is beautiful: An inverted view of habitat fragmentation in seagrass beds

An intertidal Zostera marina landscape in Torbay, Devon, UK, was sampled to investigate the relationship between patch size, diversity and infaunal assemblage composition with the intention of defining a minimum Zostera patch size where the infaunal seagrass assemblage becomes distinct from the bare sand assemblage. All Zostera patches were found to support a higher level of biodiversity than the surrounding bare sand. However, the size of the Zostera patch had no impact on the level of diversity; it was just the presence or absence of seagrass that made a difference. The sediment and seagrass variables were not significantly different across the range of Zostera patch sizes, indicating that the environment characteristics were homogeneous within the Zostera patches at the patch scale. Multivariate analysis revealed that assemblage composition did vary between the patch types, although the opportunistic polychaete Capitella capitata was present in all patch types and was the most abundant species overall. The presence of opportunistic species and the homogeneity of the Zostera patch variables may be due to the location of this intertidal seagrass bed, which is relatively exposed compared to the locations of other seagrass beds along the south coast of Devon, resulting in a more dynamic and disturbed environment. Nevertheless, our results demonstrate that even small patches of seagrass comprising a few plants support a higher abundance and diversity of infaunal invertebrates than bare sand, indicating that Zostera patches have conservation value whatever their size.     

Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects

Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove-groove corrosion defect pair exposed to internal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines.     

Effect of the Zagros Mountains on the spatial distribution of precipitation

In order to examine the effect of the Zagros Mountains on precipitation, first, the annual and Seasonal rainfall indices （rain days frequency, rain amount, daily rainfall intensity, and heavy rains） from 43 stations in 1995 - 2004 between the 30° N to 35° N parallels over the mountain range were analyzed. Second, the effect of the Zagros Mountains was studied through the computation of the spatial correlations between the precipitation parameters and the topographic indices （station site elevation, station mean elevation within a radius of 2.5 km, mean elevation of 9 blocks along each of the eight Cartesian directions, and the elevation differences of these 9 blocks from the station mean elevation）. The results showed that in the cold season the maximal rainfall occurs on the upper range of west slope, while in warm season it spreads over the study area. The correlations between precipitation and elevation indices were positive on the north of the stations and negative on the south of the stations, that is, the higher elevations of the stations to the north force the uplifting of the moist air masses and increase rainfall at the stations, while the lower elevations to their south lead the movement of the moist air masses to the stations. This is due to the fact that these stations or slopes are exposed to the moist air masses coming from the Mediterranean Sea and the Persian Gulf. The heavy rain days and the summer sporadic rain events do not show significant correlations with the topographic indices. The findings indicate that the Zagros Mountains intensify the cold period frontal rains especially over the west slope and block the moist air masses from entering the interior parts of the country. Moreover, these mountains play a secondary role in creating rain days. But they are very important in the production of precipitation in the area. Therefore, their absence will decrease the amount of rainfall to their west and, in return, expand the dry climates of their west and east.     

顾及时空邻近的恐怖团伙关系发现方法

现有恐怖团伙关系挖掘方法因其难以顾及恐怖组织特有的结构复杂、行动灵活、生存期长等特点而难以应用于反恐研究中.为此,本文从时空角度出发,通过引入时空邻近与团伙时空同现模式等概念,将多元独立分布的团伙关系发现问题建模为时空同现模式的频繁度评价问题,提出一种点模式分布下的团伙关系挖掘方法.基于此方法构建团伙关系网络,进而提出...     

中国城乡实体要素流动对城乡融合发展的影响机制研究

城乡要素流动贯穿城乡发展全过程,是构建城乡能否实现融合发展的核心,探究城乡实体要素流动对城乡融合发展的作用机制,能够为城乡融合发展破局提供科学指导。论文基于TOPSIS模型对全国292个城市的城乡融合发展水平进行评价,采用普通最小二乘法(OLS)和地理加权回归(GWR)模型探究城乡实体要素流动对城乡融合的影响机制。研究结果表明：(1)中国城市层面的城乡融合发展水平存在较大空间分异特征,达到深度融合水平的多为经济发达城市。相较而言,东部地区的城乡融合发展最为平衡。(2)全局上看,土地要素与人才要素的流动对城乡融合发展的影响最为显著,且两者驱动作用为负;局部上看,各城乡实体要素流动对城乡融合发展的影响具有明显的地域差异性。(3)土地要素流失使乡村失去了生产要素和发展空间,而人才要素无有效路径回流至乡村,使其限制了城乡融合;政府投资促进实体要素集聚并降低要素流动成本,城乡产业实现分工协作、功能互补,信息要素有效流动降低其他实体要素配置成本并提高配置效率,这益于城乡融合。     

东北地区人口流动与多元交通网络格局的偏离和关联

受限于个体流动数据的获取制约,以往人口流动研究多采用交通网络强度来模拟城市间的人口流动强度,忽视了二者之间的偏离。论文以铁路、公路车次构建交通网络,以腾讯位置大数据的铁路出行、公路出行数据构建人口流动网络,运用社会网络分析法、QAP模型,对比分析两者之间的偏离和关联。研究发现：(1)东北地区铁路人口流动和其交通网络格局均呈现出以“哈大”走廊为轴的南密北疏、东众西寡的特征。铁路人口流动网络结构较为分散,铁路交通网络的极化效应明显。(2)公路人口流动和其交通网络的偏离较大。公路和铁路之间存在竞争和互补关系,在铁路交通不太发达的地区,公路人口流动强度和其交通网络强度较高。(3)人口流动与交通网络存在一定关联,但人口流动受多方面因素影响,综合联系网络模型则能更准确地模拟城市间人口流动。其他影响因素中,经济联系、人口规模等因素对人口流动的影响不够明显,而城市间的邻接关系对人口流动有显著影响。(4)铁路人口流动与其交通网络的关联程度较公路人口与其交通网络的关联程度高。论文定量说明了人口流动与其交通网络的相关程度,为交通网络模拟人口流动提供了理论和实际操作层面的参考。     

A theoretical analysis of interactive coercing effects between urbanization and eco-environment

Objectively, a complex interactive coercing relationship exists between urbanization and eco-environment, and the research of this relationship is primarily divided into three schools, i.e., interactive coercion theory, interactive promotion theory and coupling symbiosis theory. Harmonizing the relationship between urbanization and eco-environment is not only an important proposition for the national development plan but also the only way to promote healthy urbanization. Based on an analysis of urbanization process and its relationship with the eco-environment, this article analyzes interactive coercing effects between urbanization and eco-environment from three perspectives of population urbanization, economic urbanization and spatial urbanization, respectively, and analyzes risk effects of the interactive coercion. Further, it shows six basic laws followed by interactive coercion between urbanization and eco-environment, namely, coupling fission law, dynamic hierarchy law, stochastic fluctuation law, non-linear synergetic law, threshold value law and forewarning law, and divides the interactive coercing process into five stages, namely, low-level coordinate, antagonistic, break-in, ameliorative and high-grade coordinate. Based on the geometric derivation, the interactive coercing relationship between urbanization and eco-environment is judged to be non-linear and it can be explained by a double-exponential function formed by the combination of power and exponential functions. Then, the evolutionary types of the interactive coercing relationship are divided into nine ones: rudimentary coordinating, ecology-dominated, synchronal coordinating, urbanization lagging, stepwise break-in, exorbitant urbanization, fragile ecology, rudimentary break-in and unsustainable types. Finally, based on an interactive coercion model, the degree of interactive coercion can be examined, and then, an evolutionary cycle can be divided into four phases, namely rudimentary symbiosis, harmonious development, utmost increasing and spiral type rising. The study results offer a scientific decision-making of healthy urbanization for achieving the goal of eco-environment protection and promoting urbanization.     

略论医学地质

医学地质主要研究地球上的无机物(元素、矿物、岩石等)和有机物(微生物等)对人类、动物和植物的作用和影响。这种作用和影响既包括致病的一面,也包括治病的一面,两者是辩证的统一体。研究表明:砷、汞、氡、石棉、晶质硅等地球物质及沙尘暴等均对人类健康造成危害。而通过对钙、磷等元素与人体骨骼的关系和元素-食物-心血管病关系的分析以及对某些人土食石习惯的探讨都清楚地证明了人体与地球的密切关系。地方病是医学地质研究的重点。我国在地方病防治工作中已取得重要成果。医学地质这一综合性边缘学科有着很大的发展潜力。     

宏观异常与地震关系的统计分析

通过对《中国震例》中所辑宏观异常的统计分析认为,随着震级的增大,震前出现宏观异常的概率逐步增大,震级大的地震震前宏观异常数量也相对较多。宏观异常大多数为短期和临震异常,多数发生在距震中100km的范围内。在时间上,宏观异常开始时数量较少;随着时间的推进,异常不断增多;越近临震,异常数量越多,直到发震达到高潮。在地域上则表现出始于震中、然后向外围发展、最后震中爆发式增多的特点。