事故树方法在泥石流灾害分析中的应用

为了解决泥石流灾害预防工作中的实际问题,通过系统安全工程的事故树分析方法,找到影响泥石流灾害产生的主要因素,建立泥石流灾害事故树图,从最小割集、最小径集、结构重要度三个方面全面分析,阐述了各基本事件对泥石流发生的影响程度,以及它们之间的逻辑关系,找到预防关键因素。最后,结合实际情况,对预防泥石流灾害提出了具体建议。     

横向各向同性介质中地震波走时模拟

横向各向同性介质是地球内部广泛分布的一种各向异性介质.针对这种介质,我们对各向同性介质的最小走时树走时模拟方法进行了推广,推广后的方法可适用于非均匀、对称轴任意倾斜的横向各向同性介质模型.为保证计算效率,最小走时树的构建采用了一种子波传播区域随地震波传播动态变化的改进算法.对于弱各向异性介质,我们使用了一种新的地震波群速度近似表示方法,该方法基于用射线角近似表示相角的思想,对3种地震波（qP, qSV和qSH）均有较好的精度.应用本文地震波走时模拟方法对均匀介质、横向非均匀介质模型进行了计算,并将后者结果与弹性波方程有限元方法的模拟结果进行了对比,结果表明两者符合得很好.本文方法可用于横向各向同性介质的深度偏移及地震层析成像的深入研究.     

Amending Soils with Hydrogels Increases the Biomass of Nine Tree Species under Non‐water Stress Conditions

The classical aim of the application of super absorbent polyacrylate (SAPs) hydrogels is the prolonging of plant survival under water stress. Their effect on plant growth during non‐water stress conditions is not known. This study examined the root and shoot biomass of seedlings of nine tree species; Eucalyptus grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba. The seedlings were potted in five soil types; sand, sandy loam, loam, silt loam and clay. These were amended at two hydrogel levels: 0.2 and 0.4% w/w and grown under controlled conditions in a green house. Root and shoot growth responses of the seedlings were determined by measuring the dry weight of the roots, stems, leaves and twigs. The addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in a significant increase of the root dry weight (p < 0.001) in eight tree species compared to the controls after 8 wk of routine watering. Also, the dry weight of stems and leaves and twigs were significantly (p < 0.001) higher in the nine tree species potted in hydrogel amended soil types than in the hydrogel free controls. These results suggested that hydrogel amendment enhances the efficiency of water uptake and utilization of photosynthates of plants grown in soils which have water contents close to field capacity.     

Impacts of unregulated harvesting on a recovering stock of native oysters (Ostrea edulis)

In Strangford Lough, Northern Ireland stocks of Ostrea edulis collapsed in the 1890s and the species was rarely recorded again until 1998 when the wild stock was estimated to be 100,000. The stock increased to 1.2 million in 2003 but declined to 650,000 by 2005. In 2007 the stock exceeded 1 million. The initial recovery of wild stocks is attributed to the combined effects of spawning commercial O. edulis stocks of and larval retention due to local hydrography. The stock decline between 2003 and 2005 is attributed to unregulated harvesting. Significant differences in abundances between sites over this period may be explained by the exploitation of more-readily accessible sites initially and of less accessible sites later. Oysters at sites where there was minimal exploitation probably contributed to widespread recruitment in 2007. Sustainable management of recovering native oyster stocks in Strangford Lough and elsewhere and will be impossible without appropriate legislation and enforcement.     

秦岭树轮记录中的ENSO事件

通过秦岭树轮宽度年表和1949年以来6次最强El Nino年和7次最强La Nina年进行对比，发现每个El Nino年都对应正的年表指数正距平，而每个La Nina年都对应年表指数的负距平，赤道东太平洋（Nino3、4）海水表层温度（SST）和树轮宽度差值年表显著正相关（r=0.269,N=121,α=0.008),1960年以后，相关系数0.480(N=33,α=0.028)，同时，树轮年表序列和南方涛动指数（SOI）显著负相关（r=-0.484,N=33,α=0.013)，在此基础上对1743年以来的SOI进行了重建，并且重建序列具有显著的2-3a周期。     

Seismic Hazard of Honduras

In this paper we have described the proceduresused, input data applied and results achieved in ourefforts to develop seismic hazard maps of Honduras.The probabilistic methodology of Cornell is employed.Numerical calculations were carried out by making useof the computer code SEISRISK III. To examine theimpact of uncertainties in seismic and structuralcharacteristics, the logic tree formalism has beenused. We compiled a de-clustered earthquake cataloguefor the region comprising 1919 earthquakes occurringduring the period from 1963 to 1997. Unified momentmagnitudes were introduced. Definition of aseismotectonic model of the whole region under review,based on geologic, tectonic and seismic information,led to the definition of seven seismogenetic zones forwhich seismic characteristics were determined. Fourdifferent attenuation models were considered. Resultsare expressed in a series of maps of expected PGA for60% and 90% probabilities of nonexceedence in a50-year interval which corresponds to return periodsof 100 and 475 years, respectively. The highest PGAvalues of about 0.4g (90% probability ofnon-exceedence) are expected along the borders withGuatemala and El Salvador.     

The decline process and major pathways of Microcystis bloom in Taihu Lake, China

Eutrophication has become a serious concern in many lakes, resulting in cyanobacterial blooms. However, the mechanism and pathways of cyanobacteria decline are less understood. To identify and define the growth and decline of Microcystis blooms in Taihu Lake of China, and to illuminate the destination of surface floating blooms, we investigated the biomass distribution and variations in colony size, morphology, and floating velocity from October 2008 to September 2009. The results showed that the Microcystis bloom declined in response to biomass decrease, colony disaggregation, buoyancy reduction, and increased phytoplankton biodiversity, and these indicative parameters could be applied for recognition of the development phases of the bloom. Three major decline pathways were proposed to describe the bloom decline process, colony disaggregation (Pathway Ⅰ), colony settlement (Pathway Ⅱ), and cell lysis in colonies (Pathway Ⅲ). We proposed a strategy to define the occurrence and decline of Microcystis blooms, to evaluate the survival state under different stress conditions, and to indicate the efficiency of controlling countermeasures against algal blooms.     

Local entropy map: a nonparametric approach to detecting spatially varying multivariate relationships

The relationship between two or more variables may change over the geographic space. The change can be in parameter values (e.g., regression coefficients) or even in relation forms (e.g., linear, quadratic, or exponential). Existing local spatial analysis methods often assume a relationship form (e.g., a linear regression model) for all regions and focus only on the change in parameter values. Therefore, they may not be able to discover local relationships of different forms simultaneously. This research proposes a nonparametric approach, a local entropy map, which does not assume a prior relationship form and can detect the existence of multivariate relationships regardless of their forms. The local entropy map calculates an approximation of the Rényi entropy for the multivariate data in each local region (in the geographic space). Each local entropy value is then converted to a p-value by comparing to a distribution of permutation entropy values for the same region. All p-values (one for each local region) are processed by several statistical tests to control the multiple-testing problem. Finally, the testing results are mapped and allow analysts to locate and interactively examine significant local relationships. The method is evaluated with a series of synthetic data sets and a real data set.     

Diversity and distribution of landscape trees in the compact Asian city of Taipei

The promotion and preservation of biodiversity in urban areas remains scant, especially in Asian cities. This study focuses on spatial pattern and diversity of landscape trees in compact Taipei. Aggregate species diversity of three urban habitats (streets, urban parks and riverside parks) exceeded the countryside's secondary forests. Urban parks with site heterogeneity and multiple functions accommodate the highest richness, and streets with acute site limitations the poorest represented by popular native species. More affinities exist between urban and riverside parks. Low diversity in riverside parks echoes natural site constraints and primary use for river discharge and flood control. The compact urban form has not stifled species diversity and spatial variability of urban forests. Development history and park area have no significant relationship with species diversity. Understanding species composition in urban ecosystems could frame conservation strategies to augment species richness, appropriate site selection, habit preservation and wildlife recruitment.     

Palaeogeographic reconstruction of the 1.55 Ma synchronous isolation of the Ryukyu Islands,Japan, and Taiwan and inflow of the Kuroshio warm current

In the Quaternary, the Ryukyu Islands evolved from a continental margin arc to an island arc by backarc spreading of the Okinawa Trough, accompanied by subsidence and isolation of the islands, a process that has continued to the present. Trough-parallel half grabens were filled with marine siltstone. Similar sediments filling orthogonal fault-controlled and west-draining non-tectonic valleys record island separation. New Quaternary nannofossil biostratigraphic data date the deposition of the marine siltstone at 1.552 ± 0.154 Ma. At that time, the entire 1000 km-long island chain comprising the Ryukyu Islands separated from the Asian continent by rifting extending from the Okinawa Trough to the Tsushima Strait. The Tokara, Kerama, and Yonaguni gaps, branched or transverse rifts of the Okinawa Trough, separate the island chain into subgroups of the Osumi, Amami, Okinawa, and Yaeyama islands, and Taiwan. The shallow Taiwan Strait separated Taiwan from the Chinese mainland. The Kuroshio warm current that previously ran offshore of the continental margin arc began to enter the opening backarc basin through the Yonaguni gap and to exit through the Tokara gap, flowing along the axis of the Okinawa Trough. Under influence of the warm current and because of entrapment of continentally sourced detrital sediments by the Okinawa Trough, coral reefs formed around each island. These reefs make up a unit called the Ryukyu limestone. Subsidence continued through the deposition of this limestone, resulting in further isolation of each island. Some islands did not separate from the mainland but emerged above sea level later as a result of volcanic edifice construction or forearc uplift. Following initial isolation, the Japanese islands and Taiwan may have been connected to the mainland by land bridges during some sea level low stands related to glacial periods, whereas the other islands remained isolated. Based on ages of isolation of each island, a Quaternary palaeogeographic map and ‘phylogenetic tree’ of the islands can be drawn showing the separation time of each island from the mainland and from each other. This information should be useful for phylogenetic molecular biologists studying evolution of Ryukyu endemic species and vicariant speciation and could facilitate analysis of the DNA substitution rate.