Assemblage structure is related to slope and depth on a deep offshore Pacific seamount chain

Scientific study has generated a range of hypotheses about the ecological structure and function of seamounts. Interpretations of these ideas and data are vital to understanding how seamount communities will respond to anthropogenic impacts. Here, we examine how diversity and structure of seamount assemblages vary with depth and slope of the sea floor. We conducted ROV video transects on three seamounts of the Taney Seamount Chain in the Northeast Pacific Ocean. Depth and slope were both related to assemblage structure on the Taney seamounts. Depth differences were seen in alpha‐ and beta‐diversity but not density. Beta‐diversity and density but not alpha‐diversity varied with slope. Overall, slope and depth together explained 14–31% of beta‐diversity. The findings suggest that differences in beta‐diversity as related to depth gradients may differ among onshore and offshore and/or between shallow and deep summit seamounts. Specifically, we hypothesize that differences in productivity and depth gradients among seamounts may generate different patterns of beta‐diversity.     

No evidence for a decrease of nuclear decay rates with increasing heliocentric distance based on radiochronology of meteorites

It has been argued that the decay rates of several radioactive nuclides are slightly lower at Earth’s aphelion than at perihelion, and that this effect might depend on heliocentric distance. It might then be expected that nuclear decay rates be considerably lower at larger distances from the sun, e.g., in the asteroid belt at 2–3 AU from where most meteorites originate. If so, ages of meteorites obtained by analyses of radioactive nuclides and their stable daughter isotopes might be in error, since these ages are based on decay rates determined on Earth. Here we evaluate whether the large data base on nuclear cosmochronology offers any hint for discrepancies which might be due to radially variable decay rates. Chlorine-36 (t_1/2 = 301,000 a) is produced in meteorites by interactions with cosmic rays and is the nuclide for which a decay rate dependence from heliocentric distance has been proposed, which, in principle, can be tested with our approach and the current data base. We show that compilations of ³⁶Cl concentrations measured in meteorites offer no support for a spatially variable ³⁶Cl decay rate. For very short-lived cosmic-ray produced radionuclides (half-lives < 10–100 days), the concentration should be different for meteorites hitting the Earth on the incoming vs. outgoing part of their orbit. However, the current data base of very short-lived radionuclides in freshly fallen meteorites is far from sufficient to deduce solid constraints. Constraints on the age of the Earth and the oldest meteorite phases obtained by the U–Pb dating technique give no hints for radially variable decay rates of the α-decaying nuclides ²³⁵U or ²³⁸U. Similarly, some of the oldest phases in meteorites have U–Pb ages whose differences agree almost perfectly with respective age differences obtained with “short-lived” radionuclides present in the early solar system, again indicating no variability of uranium decay rates in different meteorite parent bodies in the asteroid belt. Moreover, the oldest U–Pb ages of meteorites agree with the main-sequence age of the sun derived from helioseismology within the formal ∼1% uncertainty of the latter. Meteorite ages also provide no evidence for a decrease of decay rates with heliocentric distance for nuclides such as ⁸⁷Rb (decay mode β⁻) ⁴⁰K (β⁻ and electron capture), and ¹⁴⁷Sm (α).     

基于震幅叠加的微地震事件定位在地面监测中的应用

在微地震地面监测中,由于微地震信号能量微弱,因此很难对微地震事件进行精确拾取。本文提出了一种基于STA/LTA(short term averaging/long term averaging)的判别频率估计模式识别方法,可以避免由于设定阈值出现漏判小能量微地震事件的情况,并在精度上比传统的STA/LTA方法提升10%以上。采用基于震幅叠加的能量聚焦方法对微地震事件进行定位计算,同时通过对能量聚焦结果的分析,进一步剔除"假"的微地震事件,从而能够更加精确地描述地下裂缝的发育情况。最后,通过对河北北部一水平井的压裂监测对该方法进行验证,结果表明,本方法计算效率高、监测结果获得施工单位的认可,能够对下一步压裂施工方案提供理论指导。     

Relationship between somatic growth and otolith growth: a case study of the ornate jobfish Pristipomoides argyrogrammicus from the coast of Réunion (SW Indian Ocean)

The ornate jobfish Pristipomoides argyrogrammicus Valenciennes 1832 occurs in the Indo-West Pacific Ocean, where it is harvested by small-scale coastal fisheries. Management of this species is hindered by lack of adequate biological data. We sampled a total of 113 individuals from the landings of local artisanal fishers on the island of Réunion (southwestern Indian Ocean), from March 2014 to March 2015. The relationships between two types of body length (total and standard length, cm) and total weight (g) were shown to be significant (p < 0.05). The length–weight relationship was described by a power function, with the scaling factor estimated to be 0.008 and the exponent 3.146. Age was determined using whole otoliths. The von Bertalanffy growth equation was estimated to be TL_t = 30.68(1 – e^?0.52(t)). Otolith morphometry variables (length, width and area) were significantly correlated with age estimates (p < 0.05). No significant difference in age estimates was observed between left and right otoliths used as predictors. Readings from observed age and the estimates from modelled age indicated relatively good agreement, suggesting the potential to use whole otoliths for age estimation.     

影响防城港市的热带气旋灾害评估方法

对1970~2003年影响防城港市的热带气旋造成的灾情进行定量评估研究,应用灾情指数,客观划分灾情等级,用来表示受灾程度,利用逐步回归方法,建立影响防城港市的热带气旋灾情定量评估和预估方法。     

雷达定量测量降水

根据桂林新一代天气雷达实际定义混合扫捕面,采用降水回波强度分级,用最优化方法统计Z-I关系中的A、b系数,定量测量降水能力得到了明显的提高,比用天气系统分类确立的Z-I关系准确率提高20%,比直接应用美国提供的Z-J关系准确率提高近40%.利用回波强度分级确定降水定量关系操作方便,容易自动变更定量估测降水的关系及实现降...     

三门峡市雷暴气候特征分析

利用1970--2009年三门峡40a逐日雷暴观测资料,采用线性倾向估计、Mann-Kendall法、小波分析,对三门峡市雷暴变化特征及突变情况进行了分析。结果表明：三门峡市年平均雷暴日数达16．5个,高发季节为每年6—8月,高发时段为14—21时;年雷暴日数年代际线性变化呈下降趋势,气候倾向率为0．5个／10a。Mann-Kendall法检验显示,雷暴总体上呈减少趋势,没有发生突变。从小波分析的结果看,三门峡市雷暴日序列具有3、6a的短周期和8、14a的长周期振荡变化,其中以6a和8a振荡周期为主要特征。     

主特征提取法在天气雷达降水估测集成分析中的应用

提出使用主特征提取法对天气雷达定量估测降水的几种模式结果进行集成分析，获得降水分布的共同特征，并参照雨量计资料确定雷达探测范围内的降水强度分布，实例分析表明效果较好。     

强降水发生的概率估计与比较

年以下时间尺度的降水量分布常在极值部分比高斯分布有着更大的发生值,为厚尾分布.作者根据在极值理论中处于重要地位的GP分布模型(Generalized Pareto distri-bution),讨论了分布模型的一些性质,运用该模型对月和日降水量的强降水概率进行了分布拟合,得到各站强降水发生的直观年数;此外,重点分析了模型中一个重要的参数--尾指数的算法和意义,并使用尾指数来比较各地强降水分布尾部的大小,对预防洪涝灾害提供了一个科学的依据.       

边坡稳定性的聚类未确知综合识别方法及应用

影响岩石边坡稳定性的因素众多且关系复杂,且存在大量未确知信息,很难用简单的方法进行分析判断,借鉴工程类比的思想,采用聚类与未确知测度相结合的方法进行研究。针对边坡工程问题环境的复杂性,以大量的历史数据为训练样本,通过动态聚类分析,求得其分类中心。针对大量的未确知信息,利用未确知测度方法对其进行评价,提出一种分析边坡稳定问题的新方法。研究表明,该算法可以对边坡的稳定状态进行预测,正确率在90%以上,为比较合理快速地分析边坡稳定分析方法提供了一条新的途径。