Experimental investigation of boundary layer transition over a delta wing at Mach number 6

An experimental study on the boundary layer transition over a delta wing was carried out at Mach number 6 in a quiet wind tunnel. The Nano-tracer-based Planar Laser Scattering (NPLS) and Temperature-Sensitive Paints (TSP) techniques were used to measure the fine flow field structure and the wall Stanton number of the delta wing. The influence of factors such as the angle of attack and the Reynolds number was studied. The following results were obtained. The boundary layer transition between the leading edge and the centerline was dominated by the crossflow instability. At the location of the initial appearance of the traveling crossflow waves, the Stanton number began to rise. The Stanton number reached a maximum when the crossflow waves were broken up to turbulence. Increasing the angle of attack increased the spanwise pressure gradient at the windward side of the delta wing, thereby increasing the crossflow instability and advancing the boundary layer transition front. However, increasing the angle of attack caused the transition front to move backward at the leeward side. In addition, the sensitivity of the boundary layer transition to the Reynolds number varied with the angle of attack and the region.     

淮北地区水稻适宜发展规模的研究

准北地区水稻发展的主要制约因素是水资源，该地区水资源系统是江水北调大系统的一个有机部分，其水稻适宜规模取决于江水北调系统水资源的开发利用。根据输水线路或水资源特征将整个系统划分为１５个子系统，以水资源利用量最大，以及缺水造成的减产损失和提水费用之和最小作为水资源利用的两个目标，建立了模拟分析数学模型，提出了求解该模型的大系统分解一协调技术，给出了模拟模型的执行顺序和运行程序，研究了当前工程水平、泵站改造项目完成、通榆河工程完成和南水北调工程建成四种情况淮北水稻适宜发展规模。     

乐安河流域儿童头发中微量元素的调查与分析

本文对乐安河流域１６０名儿童发中Ｃｕ、Ｚｎ、Ｐｂ、Ｃｄ、Ｎｉ、Ｍｎ、Ｆｅ七种微量元素的含量进行了测定和分析。经比较发现，新建与中洲之间，Ｃｕ、Ｍｎ、Ｆｅ含量差异有极显著性（ｐ＜０．０１），Ｚｎ、Ｐｂ含量差异有显著性（ｐ＜０．０５）；新建与戴村之间Ｃｕ、Ｚｎ含量差异有显著性；新建与蔡家湾之间，Ｍｎ、Ｆｅ含量差异有显著性；以上差异都是实验点（中洲、戴村、蔡家湾）高于对照点（新建）。Ｃｄ、Ｎｉ含量各点之间浓度值相近。对受试儿童身高、体重、胸围的调查结果表明，对照点均高于实验点。结果显示，重金属污染对乐安河流域儿童的健康可能造成不同程度的影响     

M/G/1排队系统性能梯度估计的非标准分析法

如何估计系统性能梯度是离散事件动态系统研究中的一个重要问题.系统性能对于概率参数的梯度无法用传统的摄动分析法来估计,我们从非标准分析的角度提出了一种基于Dirac δ函数的摄动分析算法,分析了相应估计量的强相合性和渐近无偏性.新算法在实现过程中需要用样条函数来近似δ函数,但可以同时估计M/G/1排队系统中顾客期望系统时间和忙期期望长度对概率参数的梯度.数值实验结果表明估计量的相对误差和无偏性检验值都比较小,新算法能够很好地估计M/G/1排队系统的性能梯度.     

Supersonic flow over a pitching delta wing using surface pressure measurements and numerical simulations

Experimental and numerical methods were applied to investigating high subsonic and supersonic flows over a 60° swept delta wing in fixed state and pitching oscillation.Static pressure coefficient distributions over the wing leeward surface and the hysteresis loops of pressure coefficient versus angle of attack at the sensor locations were obtained by wind tunnel tests.Similar results were obtained by numerical simulations which agreed well with the experiments.Flow structure around the wing was also demonstrated by the numerical simulation.Effects of Mach number and angle of attack on pressure distribution curves in static tests were investigated.Effects of various oscillation parameters including Mach number, mean angle of attack, pitching amplitude and frequency on hysteresis loops were investigated in dynamic tests and the associated physical mechanisms were discussed.Vortex breakdown phenomenon over the wing was identified at high angles of attack using the pressure coefficient curves and hysteresis loops, and its effects on the flow features were discussed.     

赣江吴城段底质Cu元素垂直污染分布研究

为建立鄱阳湖水域沉积物中重金属的相关研究方法,了解重金属污染物的迁移规律,并探讨底泥中重金属的垂直分布特征,采用底质柱状采样器通过临水垂直插管法采集鄱阳湖流域赣江吴城段的底质样品,利用微波消解—AS-990型原子吸收分析体系对柱状样中不同深度的样品进行重金属Cu含量的测定。结果显示,柱状样垂直方向和年代分布中Cu含量呈锯齿型分布。重金属垂直分布与年代变化相一致,是因为年代分布与底泥沉积厚度之间的关系主要由沉积率所决定。     

造成去年关中洪灾的原因及法律索赔探析

2003年关中渭河洪灾,不是纯天灾,而是“人祸与天灾混合体”。“人祸”即三门峡某水电企业拒绝各方长期劝告,坚持高水位发电,酿成陕西56万灾民和20多亿元损失。在酝酿处理善后的思路上,并没有涉及该企业对陕西公私受灾者依法进行部分赔偿的问题,本文从法律角度进行了深入剖析,提出了应给灾民以合理合法的赔偿。     

GRACE products and land surface models for estimating the changes in key water storage components in the Nile River Basin

The Nile River Basin (NRB) is facing extreme demand for its water resources due to an alarming increase in population and the changing climate. The NRB is not compatible with ground-based in-situ observations owing to its large basin area size and limited hydrological data access from basin countries. Thus, it lends itself to remotely sensed approaches with high spatial resolution and extended temporal coverage. The Gravity Recovery and Climate Experiment (GRACE) avails a unique opportunity to investigate the changes in key components of terrestrial water storage (TWS). GRACE TWS solutions have specific tuning parameters and processing strategies that result in regionally specific variations and error patterns. We explored the TWS time series spatiotemporal changes, trends, uncertainties, and signal-to-noise ratio among different GRACE TWS data. We had also investigated the key terrestrial water storage components such as surface water, soil moisture, and groundwater storage changes. The results show that GRACE spherical harmonic solutions' uncertainty is higher than the mass concentration (mascon) over the NRB, and the Center for Space Research-mascons had the best performance. The evapotranspiration correlation (R² = 0.85) has the highest correlation with GRACE’s TWS, whereas the normalized difference vegetation index (R² = 0.82) has the second highest correlation. Notably, significant long-term (2003–2017) negative groundwater and soil moisture trends demonstrate a potential depletion of the NRB. Despite an increase in precipitation and the TWS time series, the rate of decline increased rapidly after 2008, thereby indicating the possibility of human-induced change (e.g. for irrigation purposes). Therefore, the results of this study provide a guide for future studies related to hydro-climatic change over the NRB and similar basins.     

测轨时序差分观测权阵的解析表达式

基于相关权逆阵和二次差分矩阵的对应关系,利用Delta函数的性质,推导了时序差分组合的相关权矩阵公式,并利用M atlab对解析表达式进行了数值验算。该公式可以直观地反映出差分组合观测量的统计相关信息。     

基于DTW的HJ-1B卫星地表温度产品质量检验

HJ-1B卫星热红外数据应用广泛,但其地表温度反演产品的质量检验工作尚不完善。以黑河流域为研究区,利用普适性单通道算法得到HJ 1B地表温度,基于7个地面站点（下垫面为荒漠、沙漠、植被、农作物、雪地和湿地）同步观测资料和MODIS地表温度产品（MOD11A1）,引入动态时间规整方法（DTW）对站点处HJ 1B地表温度进行验证。试验结果表明：HJ 1B地表温度反演产品与地面观测值的偏差值在沙漠和荒漠站点为1K以内,均方根误差在05K左右;对于植被和农作物站点的偏差在2K以内,均方根误差为1~2K;基于DTW的验证对时序不匹配的数据评价结果与现有指标表现一致。HJ-1B地表温度反演产品与地面站点的相对偏差均低于其与MODIS地表温度反演产品的相对偏差。