ITRF2014框架简介

介绍了ITRF2014的定义、测站的全球分布、输入数据的基本情况、处理数据的基本策略以及相对于ITRF2008的改进。ITRF2014首次考虑了非潮汐大气载荷模型,提升了参考框架的精度并优化了内部模型。在推出台站坐标、速度、残差、EOPs等常规产品的基础上,ITRF2014提出两个新产品：只基于SLR的地心运动模型和震后形变模型。原有模型的改进与新模型的提出为世界各区域坐标系的更新与精化、地震的预测等作出了新的贡献。     

三塔自锚式悬索桥动力特性及影响参数分析

以某三塔自锚式悬索桥为工程背景,建立三维有限元模型,通过调整缆索初应变确定恒载作用下的成桥线形,基于静力平衡状态进行模态分析得到三塔自锚式悬索桥的振型及频率。结构动力特性影响参数分析表明:主缆抗拉刚度、加劲梁竖向弯曲刚度、桥面恒载集度、矢跨比等参数对结构动力特性影响较大。     

南海西北部半日内潮参量次谐频不稳定生成的近惯性波研究

为了研究非临界纬度上参量次谐频不稳定(parametric subharmonic instability,PSI)过程生成的近惯性波(near-inertial wave,NIW),本文基于国家重点研发项目的 准实时传输深海潜标资料,对内波速度谱、近惯性流速和动能、D2-f(半日频减惯性频)流速和动能、半日内潮流速和...     

在平台振荡条件下TLP张力腿的涡激非线性响应

给出了预测张力腿涡激横向振动的时域分析,考虑了波浪、海流、张力腿平台的横漂与垂荡诸因素.张力腿平台的垂荡引起张力周期性变化,对张力腿的涡激横向振动起参数激励的作用,使其动力响应更为复杂.讨论了参数激励下涡激响应的共振条件;以尾流振子模型为基础,发展了分析张力腿在动张力作用下的涡激振动的工程方法,并分析了一座TLP实例,给出了在横漂周期内张力腿上质点的相对位移、弯矩、剪力幅值的时间历程.结果表明,平台垂荡使张力腿的涡激响应幅值升高、高频成分增加,因此它对张力腿的疲劳设计是重要的.     

The econometric estimation and testing of DARP models

DARP, acronym for Drift Analysis of Regression Parameters, originated as a heuristic technique for the investigation of parametric drift in any arbitrary `expansion space', geographic or otherwise. DARP was intended as an exploratory tool useful to aid with the formal specification of parametric drift. In this paper, the DARP technique is reformulated in terms of `DARP models', and the estimation and testing of these models by GLS, FGLS, and ML are discussed. The ML estimation of a spatial DARP model is demonstrated using empirical data. Received: 4 March 1998/Accepted: 23 December 1998     

Statistical Methods for Jointly Estimating the Decay Constant of 40K and the Age of a Dating Standard

To simultaneously evaluate the decay constant of ⁴⁰K () and the age of a standard (t _std) using isotopic data from geologic materials, we applied a series of statistical methods. The problem of estimating the most probable intercept of many nonlinear curves in and t _std space is formulated by an errors-in-variables nonlinear regression model. Then a maximum likelihood method is applied to the model for a point estimate, which is equivalent to the nonlinear least square method when measurement error distributions are Gaussian. Uncertainties and confidence regions of the estimates can be approximated using three methods: the asymptotic normal approximation, the parametric bootstrap method and Bonferroni confidence regions. Five pairs of published data for samples with ages from 2 ka to 4.5 Ga were used to estimate and the age of Fish Canyon sanidine (t _FCs). The statistical procedure yields most probable estimates of (5.4755 ± 0.0170 × 10^–10 (1)/year) and t _FCs (28.269 ± 0.0661 (1) Ma) which are in between previously published values. These results indicate the power of our approach to provide improved constraints on these parameters, although the preliminary nature of some of the input data require further review before the values can be adopted.     

临近既有地铁车站的基坑变形性状研究

通过36组二维有限元数值模拟,研究了不同参数（基坑与地铁车站距离D,基坑开挖深度 ）组合下临近既有地铁车站的基坑变形性状,并与邻近无车站时的基坑变形性状进行对比分析。研究结果表明：（1）当邻近存在地铁车站时,靠近车站一侧的地下连续墙最大侧移量减小,另一侧的地下连续墙最大侧移量增加;（2）当基坑开挖深度接近或超过地铁车站底板埋深时,车站对远离车站侧的基坑墙后地表沉降的影响显著,但不明显改变地表沉降影响范围和最大沉降值位置;（3）D较小时,随着 的增大,地铁车站的“遮拦效应”越来越显著。而当D逐渐增大时, 对地铁车站“遮拦效应”的影响逐渐减弱。（4）地铁车站的存在与否对基坑远离车站侧最大地表沉降和最大地下连续墙侧移的比值（δevm / δehm）几乎没有影响,并且,该值受D与 的影响较小。     

Parametric Analysis and Experimental Study on Local Flexibility of TY-Type Tubular Joints

Loal flexibility of tubular joints has important effect on the static and dynamic behaviour of offshore platforms, therefore, the determination of it becomes an important research subject in the field of offshore engineering. In this paper, the local flexibility of TY-type tubular joints, which are widely used in offshore platforms, is calculated by using semi- analytical method. Based on the calculated results, parametric formulae for evaluating element in the local joint flexibility matrix of TY- type tubular joints are derived by regression. A test on PVC models of TY-type tubular joints to measure the local joint flexibility is also reported. A comparison of the results calculated from the parametric formulae presented in this paper with those measured from the model test shows that the parametric formulae are reliable. It is recommended that these formulae be used in the global structural analysis of offshore platforms.