可可西里北缘中新世火山活动带的基本特征

可可西里北缘火山活动带为可可西里中新世火山活动区数条火山活动带之一,其特征十分典型。本文以火山地质、同位素、岩石化学以及稀土元素地球化学为基础对其岩浆来源、演化、火山活动规律进行了研究。该火山带粗安岩-粗面岩-亚碱性流纹岩组合与世界高原溢流玄武岩类似,同时反映大陆伸展的构造环境。     

On the dominance of pre-existing swells over wind seas along the west coast of India

Wave data collected off Goa along the west coast of India during February 1996-May 1997 has been subjected to spectral analysis, and swell and wind sea parameters have been estimated by separation frequency method. Dominance of swells and wind seas on monthly and seasonal basis has been estimated, and the analysis shows that swells dominate Goa coastal region not only during southwest monsoon (93%), but also during the post-monsoon (67%) season. Wind seas are dominant during the pre-monsoon season (51%). The mean wave periods (T_m) during southwest monsoon are generally above 5 s, whereas T_m is below 5 s during other seasons. Co-existence of multiple peaks (from NW and NE) was observed in the locally generated part of the wave spectrum, especially during the post-monsoon season. NCEP reanalysis winds have been used to analyse active fetch available in the Indian Ocean, from where the predominant swells propagate to the west coast of India. A numerical model was set up to simulate waves in the Indian Ocean using flexible mesh bathymetry. The correlation coefficients between measured and modelled significant wave heights and mean wave periods are 0.96 and 0.85, respectively. Numerical simulations reproduced the swell characteristics in the Indian Ocean, and from the model results potential swell generation areas are identified. The characteristics of swells associated with tropical storms that prevail off Goa during 1996 have also been analysed.     

Identifying the characteristic signatures of fold-accommodation faults

Hand-specimen and outcrop scale examples of folds are analyzed here to identify the characteristic signatures of fold-accommodation faults. We describe and analyze the geometric and kinematic relationships between folds and their associated faults in detail including the structural position and spatial distribution of faults within a fold, the displacement distribution along the faults by applying separation–distance plots for the outcrop scale examples, and the change of cut-off angle when the fault cut across folded layers. A comparison between fold-accommodation faults and fault related folds based on their separation–distribution plots and the problem of time sequence between faulting and folding are discussed in order to distinguish fold-accommodation faults from the reverse faults geometrically and kinematically similar to them. The analysis results show that fold-accommodation faults originate and terminate within a fold and usually do not modify the geometry of the fold because of their limited displacement. The out-of-syncline thrust has a diagnostically negative slope (separation value decreasing away from the upper fault tip) in the separation–distance graph. The change of cut-off angle and the spatial distribution of faults display a close relationship with the axial surface of the fold. Our analyses show that fold-accommodation faults are kinematically consistent with the flexural slip of the fold. The interbedded strata with competence contrast facilitate formation of fold-accommodation faults. These characteristic signatures are concluded as a set of primary identification criteria for fold-accommodation faults.     

Seasonal characteristics of the Tsushima Current in the Tsushima/Korea Strait obtained by a fine-resolution numerical model

The horizontal distribution of the Tsushima Current in the Tsushima/Korea Strait is assessed by a fine-resolution numerical experiment. The comparison of the model results with the observations along a section crossing the strait shows that the model represents relatively well, the general tendency of what was observed, such as the separation of the Tsushima Current into the western and eastern streams by the Tsushima Island. In summer, strong and relatively uniformly distributed surface currents enhance the formation of the wake downstream of the Tsushima Island. The axis of the countercurrent, embedded in the wake, is closer to the western stream. Anti-cyclonic eddies are shed near the downstream tip of the Tsushima Island and propagate along the boundary between the western stream and the wake. The exchange of water between the western stream and the wake takes place through the intermediation of these eddies. There is a net water supply from the western stream to the wake, which is then carried to the eastern stream by the countercurrent via the eastern coast of the Tsushima Island. In winter, currents, strongly barotropic, tend to have banded structures, especially in the region downstream of the western channel where isobaths converge in the downstream direction. The eddies found in this region in winter appear to be fundamentally different from those associated with the Tsushima Island wake. The necessary condition for barotropic instability is satisfied for the monthly mean currents in this region, suggesting that the currents are barotropically unstable in this region in winter.     

Studying ice sheet stability using the method of separation of variables

Abstract

Stability of two-dimensional stationary continental and marine ice sheets is studied using perturbations of ice sheet surface elevation and the margin position about a steady-state solution. Ice accumulation rate at the upper surface is specified as a function of elevation and span. Ice is considered as a Newtonian fluid. Linearisation and separation of variables yield a non-homogeneous eigenvalue problem. In case when the margin moves, a necessary condition for the existence of a solution is very restrictive on the functions of the bed profile and accumulation rate. The method of separation of variables is applicable when the margin is assumed to be stationary. Singularity of the perturbation at the margin is treated using the method of matched asymptotic expansions. Numerical experiments show that dependence of accumulation rate on elevation contributes strongly towards ice sheet instability. Bed slope, ice thickness at the grounding line of a marine ice sheet and equilibrium line inclination are the main parameters determining the ice sheet reaction to a surface perturbation.     

正交小波变换研究复杂下垫面边界层的湍流特征

小波变换方法具有较好的时频局部特性,非常适合于分析非平稳的湍流信号。本文对35 m铁塔的超声风速测量数据进行了离散正交小波变换,计算了各向同性系数(ISO isotropy coefficient)及小波功率谱,以此对实验场所代表的水陆交际复杂下垫面的近地面层湍流特征进行了研究。ISO系数可以很好地描述实际大气在不同尺度的各向同性特征。根据ISO系数的分布,我们可以通过设定一定的阈值(ISO=0.7)来得到各向同性小涡的分离尺度(记为ISO0.7),即湍流的各向同性尺度范围。研究表明,下垫面对于边界层湍流各向同性特性具有相当大的影响,当风从不同下垫面吹过时ISO0.7尺度的均值具有较明显的差异。同时湍流度和稳定度对湍流各向同性也有一定的影响。对湍流小波功率谱研究表明,功率谱谱幂率在分离出的小涡所处的频段接近于-5/3。而当风从陆面吹过且湍流度较弱时,湍流小波功率谱小涡以分离尺度所对应的频率(fms)为界具有明显的两段趋势:高于fms的频段,谱幂率一般接近-5/3;而低于fms的频段的谱幂率接近-3/3。这反映了下垫面特征对湍流功率谱的影响。同时在不同的风向转变过程中下垫面对功率谱的影响具有差异。     

离子液体合成及其在萃取分离中的应用进展

作为环境友好型功能材料—离子液体以其独特的物理化学性质已引起人们的广泛关注。简要介绍了离子液体的组成、结构和性能,概述了离子液体的合成方法,详细介绍了离子液体在萃取分离有机物、金属离子、稀土、放射性元素及燃气脱硫等领域的应用进展。最后探讨了当前存在的问题及研究方向,展望了其应用前景。     

Tilting separation flows: a mechanism for intense vertical mixing in the coastal ocean

Observations of a front associated with boundary layer separation from a headland illustrate a mechanism by which horizontal density gradients create intense turbulence and vertical mixing, thus, contributing to water property modification in the coastal zone. Tidal current past an island separates from the coast, creating a shear zone between the primary flow and the slowly moving water in the lee of the island. The density structure on either side of the front may differ due to different origins or degrees of prior mixing. Consequently, there can be horizontal density gradients across the front. Boundary layer separation from the headland begins as a vertical vortex sheet on which instabilities grow to form a sequence of eddies. The presence of horizontal density gradients causes the shear layer to tilt. Tilting and stretching of the sheared flow generates intense circulation. Whirlpools and boils appear at the surface accompanied by vertical motions in which broad areas of upwelling alternate with narrow areas of downwelling. These mix the water throughout its depth; bubbles entrained at the surface reach depths of over 120 m. Such violent mixing weakens stratification associated with the estuarine circulation and aerates water masses passing through the area.     

响应面法优化浒苔半纤维素的提取条件及其组分分析

以浒苔(Enteromorpha prolifera)为原料,采用响应面法优化碱性过氧化氢提取半纤维素的条件。在单因素实验的基础上,运用Box-Benhnken中心组合原理,设计四因素三水平实验,确定半纤维素最佳提取条件。采用红外光谱(FT-IR)和离子色谱(IC)分析浒苔半纤维素组分。结果表明,各因素对浒苔半纤维的提取率的影响为:时间温度料液比氢氧化钠浓度。碱性过氧化氢法提取半纤维素的最佳条件为:氢氧化钠浓度为4.8 g/L,提取温度为92℃,提取时间为5 h,料液比1︰70,半纤维素的提取率为56.75%,与预测值57.30%基本一致。FT-IR结果显示,浒苔半纤维素红外吸收光谱中含有明显的木糖和阿拉伯糖的特征吸收峰,为吡喃环结构,由β-糖苷键连接。离子色谱结果表明,浒苔半纤维素主要由木糖和阿拉伯糖组成,含有少量葡萄糖和半乳糖。木糖含量为54.4%,其次为阿拉伯糖,含量为15.3%,葡萄糖和半乳糖含量分别为5.6%和2.7%。     

磁组构的分离与岩石构造变形分析

目前实验条件下获得的AMS（磁化率各向异性）是岩石内所有磁性矿物磁化率各向异性叠加的综合响应,详细的岩石磁学和构造地质学的综合分析表明常规AMS测试结果通常无法揭示岩石复杂的构造变形过程.本文综述了运用非磁滞剩磁各向异性（AARM）、低温AMS（LT-AMS）和高场AMS（HF-AMS）等实验方法对岩石AMS组分进行分离,可以定量获取不同磁性矿物的磁组构贡献,进而解释其不同的变形特征.在此基础上阐述了近年来针对不同磁性矿物组合的AMS分离方法的理论技术创新和进展及其在岩石构造变形特征分析中的应用前景,讨论了常见磁性矿物单晶的岩石磁学性质及各向异性度（P_j）与形状因子（T）在揭示岩石变形特征中的复杂性与局限性,最后举例并分析了磁组构分离技术在造山带岩石构造变形分析中的应用.