褐煤孔隙结构及比表面积特征

为揭示褐煤孔隙结构及比表面特征,选取全国主要褐煤产地样品,进行煤岩显微组分含量测定和低温氮吸附实验,从吸附曲线形态、比表面积、孔径结构分布刻画煤储层微孔隙特征,探讨孔径结构与比表面积的关系,分析BET比表面积与煤岩显微组分的相关性。结果表明：褐煤低温液氮曲线形态大致可以分为无吸附回线、有拐点的吸附回线和无拐点的吸附回线3类;BET比表面积随BJH总孔体积的增加呈线性增加趋势,在2~10 nm范围内的孔径和比表面积关系可以分为正相关、负相关和复合相关3种;显微组分组和比表面积的相关性较弱,但比表面积与细屑体含量具有较好的线性关系。     

机载InSAR系统精度分析

结合SAR成像原理,在提出了基于DGPS/IMU数据的机载InSAR系统DEM三维坐标求解的基础上,推导出了基线长度、基线倾角、相位差、雷达天线到地面目标点的距离、雷达天线位置、中心多普勒频率及飞机飞行速度等因素误差对DEM精度的影响公式,分析讨论了机载InSAR系统影响精度的主要因素及系统可实现的性能情况,提出了机载InSAR系统部分设计建议,并使用实际的机载InSAR数据进行了试验。结果表明,本方法结果与实际试验统计的精度基本一致,影响精度的分析结论正确。     

高精度地震探测陆域天然气水合物的有效性研究

为配合天然气水合物资源勘探工作,2010年在木里地区开展了高精度反射地震方法探测天然气水合物的有效性试验研究.反射地震采用192道接收,道间距2m,炮间距8m,覆盖次数24次,每道采用6个60 Hz检波器单点组合接收.激发震源使用炸药,井深为3~4m,激发药量为1.2~2.4 kg.采用该工作方法得到地震剖面的信噪比和分辨率较高,构造形态特征明显.综合分析解释反射地震和测井及地质资料,推断解释了天然气水合物富集地带,提出了验证孔位.2013年,该探测结果得到了DK9钻孔验证,在距离已发现天然气水合物DK3钻孔SE方向约450m处发现了厚度较大的天然气水合物.试验研究结果表明:在天然气水合物含量较低的测区,利用地震方法直接探测天然气水合物难度较大,但综合分析测区物化探和地质资料,结合钻井资料,能够通过反射地震探测天然气水合物的富集地带.     

天津滨海新区软土工程地质分区多级模糊综合评判模型

选择软土的成因类型、工程性质、空间分布及场地工程环境4个二级评价影响因素和相对应的16个一级单因素评价指标,采用模糊数学的方法,建立了天津滨海新区软土工程地质分区多级模糊综合评判模型。利用该模型对一般道路、货场、单层厂房等轻型建筑地基作用的浅部层进行分区,结果表明该区软土工程场地条件由西向东逐渐变差,特别是吹填场地为该区最不利的工程场地。     

Evaluating spatiotemporal variation in water chemistry of the upper Colorado River using longitudinal profiling

Stream water chemistry is traditionally measured as variation over time at fixed sites, with sparse sites providing a crude understanding of spatial heterogeneity. An alternative Lagrangian reference frame measures changes with respect to both space and time as water travels through a network. Here, we collected sensor-based measurements of water chemistry at high spatial resolution along nearly 500 km of the Upper Colorado River. Our objective was to understand sources of spatiotemporal heterogeneity across different solutes and determine whether longitudinal change manifests as smooth gradients as suggested by the River Continuum Concept (RCC) or as abrupt changes as suggested by the Serial Discontinuity Concept (SDC). Our results demonstrate that Lagrangian sampling integrates spatiotemporal variation, and profiles reflect processes that vary in both space and time and over different scales. Over each day of sampling, water temperature (T) and dissolved oxygen (DO) varied strongly in response to diel solar cycles, with most of the variation driven by sampling time rather than sampling location. Equilibration of T and DO with the atmosphere limited small scale spatial heterogeneity, with variation at the entire profile scale driven by regional climate gradients. As such, T and DO profiles more closely approximated the smooth gradients of the RCC (though including temporal sampling artefacts). Conversely, variation in specific conductance and nitrate (NO₃-N) was largely driven by spatial patterns of lateral inflows such as tributaries and groundwater. This resulted in discrete shifts in the profiles at or downstream of discontinuities, appearing as the profiles expected with the SDC. The concatenation of spatiotemporal variation that produces observed Lagrangian profiles presents interpretive challenges but also augments our understanding of where, how, and critically why water chemistry changes in time and space as it moves through river networks.     

海洋溢油合成孔径雷达图像特征提取及其关键度分析

就SAR图像溢油检测的方法论而言,用于识别溢油和疑似现象的定性或定量的统计特征量选择,通常是任意的。对于不同的分类模型,所选用的特征量也不尽相同。主要是进行海洋SAR图像特征提取及其关键度分析。其目的是将"最小距离"判别法应用于海上溢油和疑似溢油的识别研究。首先,针对海洋SAR图像溢油检测常用的特征量,进行冗余处理;然后,引入关键系数,定量地研究特征量的关键度,提取显著特征量;藉以构造一个多维的特征矢量空间,以适于最小距离判别法在特征矢量空间中进行溢油和疑似溢油的识别研究。     

The Woods Reef (New South Wales) earthquake of 14 November 1990: Focal mechanism derived from amplitude ratios and synthetic seismograms

On the morning of 15 November 1990 local time, Armidale and the area to the west of Armidale was shaken by a magnitude 3.2 earthquake. The epicentre was located at 30.39° S, 150.88° E and the depth of focus at 12 ± 7 km. As the epicentre was close to the Peel Fault an attempt was made to constrain the focal mechanism of this earthquake. The conventional method, which is based on the analysis of P wave polarities, was not applicable because the event was not strong enough. In an alternative method, the amplitudes of various seismic phases recorded at a number of stations well distributed in azimuth were compared with theoretical amplitudes calculated with the reflectivity method for a point shear dislocation in a layered medium. The differences between observed and calculated amplitudes were minimized as a function of fault strike, fault dip and direction of the slip vector. The analysis indicates that none of the possible fault planes had the strike of the Peel Fault. The solution suggests predominantly strike slip motion along two possible, steeply dipping fault planes. The inferred direction of the maximum compressional stress. is east‐west which is in good agreement with other estimates of the stress field for eastern Australia.     

Disaggregation modelling of monthly streamflows using a new approach of the method of fragments

Abstract

The method of fragments is applied to the generation of synthetic monthly streamflow series using streamflow data from 34 gauging stations in mainland Portugal. A generation model based on the random sampling of the log-Pearson Type III distribution was applied to each sample to generate 1200 synthetic series of annual streamflow with an equal length to that of the sample. The synthetic annual streamflow series were then disaggregated into monthly streamflows using the method of fragments, by three approaches that differed in terms of the establishment of classes and the selection of fragments. The results of the application of such approaches were compared in terms of the capacity of the method to preserve the main monthly statistical parameters of the historical samples.

Editor D. Koutsoyiannis; Associate editor C. Onof

Citation Silva, A.T. and Portela, M.M., 2012. Disaggregation modelling of monthly streamflows using a new approach of the method of fragments. Hydrological Sciences Journal, 57 (5), 942–955.     

A continuous simulation model for design-hydrograph estimation in small and ungauged watersheds

Abstract

A detailed investigation of the behaviour of various hydraulic parameters, using data from rivers in Greece, was conducted in order to explore the universality of features that many natural streams are believed to have in common. Analysis of vertical profiles of temporal mean of horizontal velocities (u) in the longitudinal (river flow) direction and of transverse profiles of depth-mean longitudinal velocities (U) estimated from these vertical profiles, measured at 232 cross-sections of several rivers in Greece, provided valuable information: on the distribution of local roughness coefficients (n_i ) along the wetted perimeter of the cross-sections examined; on the shape of u profiles; on the ratio of maximum to mean cross-sectional velocity, V_max/V_m , and its relation to a dimensionless entropy parameter, M; on the shape of U profiles; and on the normalized intensity, r, of the spatial departure of u velocities from V_m . The similarities among the quantities (u, U, n, V_max/V_m , M, r) analysed in this study and in pertinent literature reveal that the rivers examined exhibit many of the basic features, of rather universal character, shown by other rivers (all over the world) having different geometric and/or other characteristics (aspect ratios, bottom roughness, flow kinematics, etc.). Corresponding differences are also described and explained.     

Dam risk assessment based on univariate versus bivariate statistical approaches: a case study for Argentina

Abstract

Considering floods as multivariate events allows a better statistical representation of their complexity. In this work the relevance of multivariate analysis of floods for designing or assessing the safety of hydraulic structures is discussed. A flood event is characterized by its peak flow and volume. The dependence between the variables is modelled with a copula. One thousand random pairs of variables are transformed to hydrographs, applying the Beta distribution function. Synthetic floods are routed through a reservoir to assess the risk of overtopping a dam. The resulting maximum water levels are compared to estimations considering the peak flow and volume separately. The analysis is performed using daily flows observed in the River Agrio in Neuquén Province, Argentina, a catchment area of 7300 km². The bivariate approach results in higher maximum water level values. Therefore the multivariate approach should be preferred for the estimation of design variables.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi