稻城冰帽库照日冰碛垄的宇生核素10Be年代测定

沙鲁里山南端的稻城冰帽在第四纪曾发生过大规模的冰川作用,然而,关于冰川作用的年代数据相对较少。选择稻城冰帽南缘库照日附近的3套冰碛垄进行宇生核素10Be的暴露年代测定,研究结果表明:(1)库照日最老冰碛垄(E)的暴露年代为(714±8.0)～(529±8.0)kaBP,D垄的暴露年代为(121±2.9)～(114±2.9)kaBP,DC垄的暴露年代为(47±1.3)～(43±1.3)kaBP。由于宇生核素暴露年代所反映的是冰川消退时的年代,因此,我们结合深海氧同位素的气候特征以及其他测年数据推断,E垄、D垄、DC垄可能是MIS16、MIS6以及MIS3b阶段冰川作用的产物;(2)冰川退却是一种逐步退却的模式。样品E的两次测验结果比较吻合,表明宇生核素10 Be暴露测年方法对冰碛垄形成年代的测定是可靠的,该方法在地貌学和第四纪年代学研究中有着巨大的潜力。     

Industrial structural changes in Hong Kong, China under one country, two systems framework

Hong Kong has undergone substantial economic transformations and developed into a sophisticated business and financial center in the Asia-Pacific region,since the return of sovereignty to China as a Special Administrative Region under the One Country Two Systems (OCTS) in 1997.This paper discusses and analyzes the industrial structural changes of Hong Kong in recent decades as well as its future challenges and opportunities.The data and finding reveal that even though Hong Kong will face fierce competition from the Mainland’s cities as the rise of China,the important role as a bridge between China and the rest of the world will brace Hong Kong itself under the OCTS for developing into a service hub for business and trade in the Asia-Pacific region.     

Self-centering seismic retrofit scheme for reinforced concrete frame structures: SDOF system study

This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.     

基于观测系统模拟试验的海表气象观测站点布局方案研究

为了科学设计黄渤海海洋气象边界层观测站网并研究观测网布局对数值天气预报模式的影响,本文采用模式误差、海洋气象要素特征区域资料统计分析和观测系统模拟试验（OSSE）方法,根据边界层雾、层云降水、小风与中等风速天气条件设计布局方案,并分析站点观测要素对数值预报模式的要素预报的影响。模拟试验数据使用了每6 h NCEP再分析资料FNL（NCEP Final Operational Global Analysis data）、NCEP每天平均的高分辨率海温资料RTG_SST（Real-Time Global Sea Surface Temperature）和石油平台、浮标站等每小时实况观测资料,评估了黄渤海海洋气象站网布局各个方案的优缺点。评估结果表明,湿度和风的要素预报受实况风向风速条件影响,偏东和偏北风个例湿度要素预报较好。然而,在偏南中等风速个例中,风场预报要素更接近实况。温度场的分析综合结果显示,在海气相互作用影响较大的天气过程中,特征区域布站能明显提高温度要素的预报准确率。最后,综合分析多项模拟试验的结果,给出了改进数值预报准确率的海洋布站建议。     

卫星遥感NO2资料地面验证对 中国大气本底观测的潜在需求

受各种因素的影响,卫星反演大气成分的数据质量存在一定的误差和不确定性,系统和全面的验证工作是获得准确可靠的卫星数据的一个重要组成部分.卫星观测资料的验证主要涉及反演算法中所用的输入参数和卫星反演产品的直接验证这两个部分的内容.本工作以对流层NO2卫星资料验证的需求出发,对当前中国大气本底站的观测现状进行评述,讨论了大气...     

Equilibrium mass-dependent fractionation relationships for triple oxygen isotopes

With a growing interest in small ¹⁷O-anomaly, there is a pressing need for the precise ratio, ln¹⁷α/ln¹⁸α, for a particular mass-dependent fractionation process (MDFP) (e.g., for an equilibrium isotope exchange reaction). This ratio (also denoted as “θ”) can be determined experimentally, however, such efforts suffer from the demand of well-defined process or a set of processes in addition to high precision analytical capabilities. Here, we present a theoretical approach from which high-precision ratios for MDFPs can be obtained. This approach will complement and serve as a benchmark for experimental studies. We use oxygen isotope exchanges in equilibrium processes as an example.We propose that the ratio at equilibrium, θ^E ≡ ln¹⁷α/ln¹⁸α, can be calculated through the equation below:

     

基于WRF-VAR的卫星资料同化分析检验试验

利用YHGSM 0.25°×0.25°高分辨数值产品作为背景场资料,使用WRF模式与WRF-VAR同化系统对中国区域进行连续一个月(2009年7月1～31日)的模拟试验,试验分为3组:(1)不同化任何资料,(2)同化常规资料,(3)同化ATOVS卫星资料;对3组试验进行了形势场检验和Ts评分.结果表明,第(2)、(3)...     

Electromagnetic anomaly before earthquakes measured by electromagnetic experiments

Three experiments are carried out for earthquake monitoring using electromagnetic (EM) methods in recent years. Some earthquakes occurred in chance of the measurement time period for each experiment and the anomalies were recorded before the shocks. The observation at a site 20 km away from the epicenter of Zhangbei MS6.2 earthquake in 1998 shows that the apparent resistivity decreases in the strike direction before and/or during the earthquake and the resistivity increases in the de-cline direction. This a...     

大气对流的阻尼模型

本文建立了同时包含线性和非线性层结和阻尼作用的大气对流模型,研究表明：阻尼条件下,对流稳定决定于层结和阻尼参数拱同作用,线性阻尼条件下,线性层结参数的正负变化会引发鞍结分岔,阻尼作用有利于对流稳定,即使线性、非线性层结构不稳定时仍可出现稳定,阻尼作用会引发新的平衡态,出现极限环。