明渠交汇口水流分离区研究

支流汇入主流后,在明渠交汇口下游附近形成分离区,造成过流断面束窄.采用水力学基本理论及试验手段,对等宽明渠交汇口水流分离区的形状及尺寸进行了理论分析和试验研究,提出了分离区收缩系数及能量损失系数的理论表达式并与试验结果进行了比较.研究结果表明,随交汇角或主支流流量相对大小不同,分离区尺寸发生变化;对于给定交汇口几何形状及尺寸,分离区形状基本保持不变,但分离区尺寸随流量比变化并具有较好的相关关系,并随交汇角增大呈有规律增加.     

采用最优频率匹配法实现信号的频段滤波处理

介绍采用最优频率匹配法进行频段滤波的基本原理,通过实际声波的信号分离,考察分离后信号的声音效果,验证了最优频率匹配法的合理性与完整性,并将该方法成功地应用于某矿区井间声波成析成像信号的滤波处理。在此基础上,比较了该方法与常规滤波方法的异同;指出了它们之间的主要差别在于匹配滤波能够从整体上保持分离后信号的协调和各自的独立性,滤波后能够获得比较完整的频段信号和匹配滤波信号;匹配滤波与常规滤波的数值差异主要表现在滤波信号的两端。通过对声波CT信号的匹配滤波处理,实现了该矿区噪声信号的分类,提取了相应的特征参数。这些工作的开展为以后科学合理地进行信号分离,以及信号与噪声的定量化处理创造了条件。     

Dynamic features of the Tianshan orogen deduced from satellitic gravity data

IntroductionGeopotential model, expressed by a spherical harmonic function, gives the global distribution of disturbed gravimetric potential. It is widely applied in the research of many disciplines of science, such as geodetics, geophysics, geodynamics, oceanography and space science. In geophysics, geopotential model shows the large-dimensional gravity variety, which is the reflection of anomalous density distribution in a large area or in the deep of the earth. Therefore, it is useful in th…     

来流速度型对立方体顶部湍流回流区影响的数值分析

为了研究不同上游来流速度型变化对立方体顶部表面是否会在前角附近产生分离、分离程度和附着情况,在对有关的实验数据进行分析比较的基础上,使用标准k-ε模型,说明立方体顶部在什么情况下会出现回流和附着,并提出附着长度Z_R和上游来流速度型u=y^1/m直接相关。同时计算结果表明：Z_R随着m的减小而增大;当m大于7时,在立方体块上部产生较严重的分离而不会有附着,这时出现Z_R>1.0。     

渗透破坏若干问题的解析解及机理分析

讨论了柱坐标下不同介质有限区域内用分离变量法求解Laplace 方程的问题。通过一系列计算试验,给出了柱坐标下Laplace 方程在不同介质有限区域内用分离变量方法求的解,并用该解对渗透破坏现象进行了讨论和实例验证。认为渗透系数分布不均匀是发生渗透破坏的根本原因,渗透破坏朝着渗透系数差异较大的方向发展,并对管涌的复杂机理进行了引申阐述。该工作对于流土、管涌机理的更深入研究具有重要的意义。     

采空场覆岩变形数值模拟与相似模拟比较研究

用有限元数值计算尝试了离层模拟,并分别采用数值模拟与相似模拟的方法研究了木架山矿区143剖面倾斜采空场处理时的地表移动与覆岩破坏规律。研究发现,随着矿柱的崩落,覆岩跨度不断增加,引起的地表移动范围也不断增大,地表垂直沉降范围大致为跨度的1.5～1.7倍,垂直沉降曲线始终对称于最大沉降点;水平移动的范围大于垂直沉降的范围,最大水平移动量大约为最大沉降量的40 %,且水平移动不对称。另外,当覆岩发生整体下沉时离层主要存在于跨度两端,离层由层理剪切破坏引起。     

树脂分离富集质谱法测定矿石中痕量铂、钯、金

讨论了王水溶矿、树脂分离富集、在硝酸介质中用质谱法测定铂、钯、金。     

Quantifying contributions of snowmelt water to streamflow using graphical and chemical hydrograph separation

In this study, we characterize the snowmelt hydrological response of nine headwater watersheds in southeast Wyoming by separating streamflow into three components using a combination of tracer and graphical approaches. First, continuous 15-min records of specific conductance (SC) from 2016 to 2018 were used to separate streamflow into annual contributions, representing water that contributes to streamflow in a given year that entered the watershed in the same year being considered, and perennial contributions, representing water that contributes to streamflow in a given year that entered the watershed in previous years. Then, diurnal streamflow cycles occurring during the snowmelt season were used to graphically separate annual contributions into rapid diurnal snowmelt contributions, representing water with the relatively fastest hydrological response and shortest residence time, and delayed annual contributions, representing water with relatively longer residence time in the watershed before becoming streamflow. On average, mean annual total streamflow was comprised of between 22% and 46% perennial contributions, 7% and 14% rapid diurnal snowmelt contributions, and 46% and 55% delayed annual contributions across the watersheds. A hysteresis index describing SC-discharge patterns indicated that, annually, most watersheds showed negative, concave, anti-clockwise hysteretic direction suggesting faster flow pathways dominate streamflow on the rising limb of the annual hydrograph relative to the falling limb. At the daily timescale during snowmelt-induced diurnal streamflow cycles, hysteresis was negative, but with a clockwise direction, implying that rapid diurnal snowmelt contributions generated from the concurrent daily snowmelt, with lower SC, arrived after delayed annual contribution peaks and preferentially contributed on the falling limb of diurnal cycles. South-facing watersheds were more susceptible to early season snowmelt at slower rates, resulting in less annual and more perennial contributions. Conversely, north-facing watersheds had longer snow persistence and larger proportions of annual contributions and rapid diurnal snowmelt contributions. Watersheds with surficial geology dominated by glacial deposits had a lower proportion of rapid diurnal snowmelt contributions compared to watersheds with large percentages of bedrock surficial geology.     

Water isotopes and hydrograph separation in different glacial catchments in the southeast margin of the Tibetan Plateau

Snow and glaciers are known to be important sources for freshwater; nevertheless, our understanding of the hydrological functioning of glacial catchments remains limited when compared with lower altitude catchments. In this study, a temperate glacial region located in the southeast margin of the Tibetan Plateau is selected to analyse the characteristics of δ¹⁸O and δD in different water sources and the contribution of glacier–snow meltwater to streamflow. The results indicate that the δ¹⁸O of river water ranges from ?16.2‰ to ?10.2‰ with a mean of ?14.1‰ and that the δD values range from ?117.0‰ to ?68.0‰ with a mean of ?103.1‰. These values are more negative than those of glacier–snow meltwater but less negative than those of precipitation. The d ‐excess values are found to decrease from meltwater to river to lake/reservoir water as a result of evaporation. On the basis of hydrograph separation, glacier–snow meltwater accounts for 51.5% of river water in the Baishui catchment in the melting season. In the Yanggong catchment, snow meltwater contributes 47.9% to river water in the premonsoon period, and glacier meltwater contributes only 6.8% in the monsoon period. The uncertainty in hydrograph separation is sensitive to the variation of tracer concentrations of streamflow components. The input of meltwater to a water system varies with local climate and glacier changes. The results confirm that hydrograph separation using water isotopes is valuable for evaluating the recharge sources of rivers, especially in ungauged glacial regions. This study provides insights into the hydrological processes of glacial catchments on the Tibetan Plateau, which is important for water resource management.