Lattice vibrational modes in synthetic tremolite-Sr-tremolite and tremolite-richterite solid solutions

Powder IR spectra of synthetic richterite-tremolite and Sr-tremolite-tremolite solid solutions were obtained in the spectral range between 1400 and 600?cm^?1. Under the consideration of the crystal structure and the Wykoff positions of the atoms in the primitive unit cell, the number, type and symmetry of vibrational modes were deduced. The space group of tremolite C_2h was used as the factor group leading to 16 theoretical stretching vibrations in the IR range caused by the Si₄O₁₁ ^∞-ribbon. The energy of the internal vibrations of the Si₄O₁₁ ^∞-ribbon is a function of the relative bond strengths and masses of nearby ions. For the amphiboles a one-mode behavior was observed for all the Si-O, Si-O-Si and O-Si-O stretching vibrations, indicating no clustering in the two solid solution series. In both solid solution series the vibrational energy of the stretching vibrations is a linear function of composition. In the system richterite-tremolite a shift of the stretching frequencies of the Si₄O₁₁ ^∞-ribbon over the whole compositional range of up to 30?cm^?1 was observed. In contrast, for Sr-tremolite-tremolite the maximum shift was only 5?cm^?1. These quite small band shifts allow the (Si₄O₁₁)^∞-ribbon to be treated as an isolated entity for factor group analysis. Nevertheless, by the two exchange mechanisms, Ca(M4)???Sr(M4) and □(A) Ca(M4)???Na(A)Na(M4), the FWHHs increased and the amplitudes decreased, indicating a slight distortion of the ribbon. For Sr-tremolite-tremolite only a linear expansion of the lattice was observed. In the series richterite-tremolite individual bond angles of the SiO₄ tetrahedra are additionally changed, causing the higher energy shift of the bands. The strongest and sharpest bands were observed for the end member tremolite. The one-mode behavior of the Si₄O₁₁-double chain indicates that there is no short-range order of Na/Ca and Ca/Sr at the M4 sites of these amphiboles.     

PERSISTENCES IN THE δ~(13)C AND δ~(18)O FROM TS95, A LAKE CORE AT THE SOUTH FRANK OF WEST KUNLUN MOUNTAIN

PERSISTENCES IN THE δ~(13)C AND δ~(18)O FROM TS95, A LAKE CORE AT THE SOUTH FRANK OF WEST KUNLUN MOUNTAIN     

海底管道收弃管作业分析

为保证海洋管道在收弃管作业过程中不发生屈服,利用样条函数配点法分析了管道为形,利用线性积分法分析了缆索的收放和受力,以图表的形式给出了管道和缆索的受力和变形、铺管船的运动以及Ａ／Ｒ绞车的拉力之间的关系。     

基于R/S分析的黑河出山年径流量灰色预测

径流过程具有分形和灰色特征。基于此,将R/S分析与灰色系统理论相结合,提出了R/S灰色预测模型以预报黑河出山径流量。针对1949—2011年莺落峡水文站年径流量资料,首先进行R/S分析,确定径流量序列的Hurst指数和平均循环周期T;然后在一个周期内进行径流量灰色预测。结果表明:黑河出山径流量循环周期在20~25年之间,在进行R/S灰色预测时,取T=20为宜;R/S灰色预测结果的精度高于直接进行灰色预测。该方法拓宽了分形和灰色理论在径流过程研究的应用范围,为径流量的科学预测提供了一种新方法。     

Effect of foundation flexibility on ductility reduction factors for R/C stack-like structures

The most important parameter used to determine force reduction factors in force-based design procedures adopted in the current seismic codes is the structural ductility. For a structure supported on a flexible foundation, the ductility factor could be affected by foundation compliances. The ductility factors given in the current codes are mostly assigned ignoring the effect of SSI and therefore the objective of this research is to assess the signifi cance of SSI phenomenon on ductility factors of stack-like structures. The deformed confi guration of stack-like structures is idealized as an assemblage of beam elements considering nonlinear moment-curvature relations, while a linear sway-rocking model was implemented to model the supporting soil. Using a set of artifi cial records, repeated linear and nonlinear analyses were performed by gradually increasing the intensity of acceleration to a level where the fi rst yielding of steel in linear and nonlinear analyses is observed and a level corresponding to the stack collapse in the nonlinear analysis. The difference between inelastic and elastic resistance in terms of displacement ductility factors has been quantifi ed. The results indicate that foundation flexibility can decrease the ductility of the system and neglecting this phenomenon may lead to erroneous conclusions in the prediction of the seismic performance of flexibly-supported R/C stack-like structures.     

测井资料计算源岩有机碳含量模型对比及分析

研究首先从理论分析入手,根据Δlog R模型在基线、有机碳含量背景值、叠合系数K、成熟度参数方面存在不足或不便推导出改进的Δlog R模型,针对改进Δlog R模型在测井参数选取方面的不足提出逐步回归模型;然后用具体实例对比三种模型应用效果,结合实例分析说明了改进的Δlog R模型优于Δlog R模型、逐步回归模型优于...     

Precipitation anomalies,economic production,and the role of “first-nature” and “second-nature” geographies: A disaggregated analysis in high-income countries

Linkages between hydroclimate variability and economic development are often theorized to be present only in developing economies. Using spatially small-scaled data from multiple decades for European regions, we examine the relationship between precipitation anomalies and economic performance in highly developed economic systems. We conduct a disaggregated empirical analysis to mitigate the bias potentially arising from spatial aggregation because precipitation realizations tend to vary drastically within larger sized economic units. We modify original precipitation indices to capture the dynamic expectation formation of economic agents about climate conditions to measure deviations from these anticipated environmental states. Using panel model regressions in a quasi-experimental research design, we analyse whether deviations from average growth rates of aggregated economic output are potentially non-linearly related to the magnitude of precipitation deviations from the anticipated climate norm within regions, after accounting for any shocks common to all regions. We find that precipitation deviations that exceed critical thresholds (intermediate anomalies) for both unusually dry and unusually wet years reduce regional growth rates. The adverse impacts are more pronounced for overly dry periods. Importantly, the relationship between economic growth and precipitation anomalies is not generalizable across all regions. Natural geographical circumstances such as prevailing climatic conditions (“first-nature” geographies) and human-made socio-economic factors such as sector structure and income level (“second-nature” geographies) moderate the anomaly response. The empirical findings substantiate the necessity to incorporate precipitation variability into the assessment of economic costs of climate change; not only in developing countries or agricultural societies but also in highly developed economic systems. Moreover, the empirical results have important implications for policy makers as uneven effect sizes at the subnational level suggest that policy measures should be targeted in space and coordinated between national and regional levels of government.