Impact of backwater on water surface profile in curved channels

Owing to extensive construction of dams, the impact of backwater on flow may lead to navigation or flood control issues in curved channels. To date, the impact of backwater on the water surface profile in curved channels remains unknown and requires investigation. In this study, experiments were conducted in a glass-walled recirculating flume with a length of 19.4 m, a width of 0.6 m, and a depth of 0.8 m, and the impact of backwater on the water surface profile in a 90° channel bend was investigated. The experimental results showed that the backwater degree had a significant impact on the transverse and longitudinal flow depth distributions in the bend. The transverse slope of the flow (Jr) increased linearly with an increase in the Froude number of the approach flow upstream of the bend. Jr increased with the longitudinal location parameter ξ when −0.2 < ξ < 0.5, and decreased with ξ when 0.5 < ξ < 1.2. Furthermore, the results showed that Jr asymptotically decreased to zero with an increase in the degree of backwater. An equation was formulated to estimate the transverse slope of the flow in a 90° bend in backwater zones.

Surface-Related Multiple Elimination on High-Resolution Geopulse Profile

A geopulse seismic system was implemented to obtain new information on underlying strata beneath the Yellow River Delta. However, owing to the shpping of sea floor and shallow water （ 〈 25 m）, free surface-related multiples are conflicted with the flat primaries, which may instruct the interpreters in a wrong way and make wrong conclusions. Owing to the variation of multiple periods, standard anti-multiple techniques may lose their power, such as predictive deconvolution. Surface-related multiple elimination methods are introduced to attenuate the multiples based on the underlying waveequation principles. The results justified the method on the single-channel geopulse profile, revealing the real nature of the subsurface.

Study on End Milling Generation Surface Model and Simulation in View of Main Axle's Tolerance

In accordance with the relative movement between end-milling cutter and workpiece surface, a theoretical generation model for milled surface was established with the movement error of principal axle considered. Then the milled surfaces under various cutting condition were simulated, the results of which showed that end milled surfaces were of "vaulted profile", heights of surface irregularty at various points to be different with maximum value in the middle and smaller at both sides, the difference were determined by diameter of milling cutter, feeding speed, ratio between the diameter of milling cutter and teeth point curve radius and width of workpiece. The study results can be applied to quality prediction of milled surfaces for precision and/or super precision milling operation.

Using Impervious Surfaces to Detect Urban Expansion in Beijing of China in 2000s

The change of impervious surface area(ISA) can effectively reveal the gradual process of urbanization and act as a key index for monitoring urban expansion. Experiencing rapid growth of the built environment in the 2000 s, urban expansion of Beijing has not been fully characterized through ISA. In this study, Landsat TM images of Beijing in 2001 and 2009 were obtained, and the eight-year urban expansion process in Beijing was analyzed using the ISA extracted by means of the vegetation-imperious surface-soil(V-I-S) model. From the spatial variation in ISA, the ring structure of urban expansion in Beijing was significant during the study period, with decreasing urban density from the city center to the periphery. In the ring road analysis, the most dramatic changes of ISA were found between the fifth ring and the sixth ring. This area has experienced the most new residential development, and is currently the main source of urban expansion. The typical profile lines revealed the directional characteristics of urban expansion. The east-west profile was the most urbanized axes in Beijing, while ISA change in the east-north profile was more significant than in the other five profiles. Moreover, the transition matrix of ISA levels revealed an increase in urban density in the low density built areas; the Moran′s I index showed a clear expansion of the central urban area, which spread contiguously; and the standard deviational ellipse indicated the northeast was the dominant direction of urban expansion. These findings can provide important spatial control guidelines in the next round of national economic and social development planning, overall urban and rural planning, and land use planning.

Numerical Simulation of Nonlinear Surface Gravity Waves Transformation under Shallow-Water Conditions

This work considers the problems of numerical simulation of non-linear surface gravity waves transformation under shallow bay conditions. The discrete model is built from non-linear shallow-water equations. Are resulted boundary and initial conditions. The method of splitting into physical processes receives system from three equations. Then we define the approximation order and investigate stability conditions of the discrete model. The sweep method was used to calculate the system of equations. This work presents surface gravity wave profiles for different propagation phases.

Improvement of two-dimension AR model and application in simulation on surface profiles of steel plates

The order and parameter estimation is always difficult in two-dimension AR model because the two-dimension Yule-Walker equation does not have the property of uniqueness and identifiability as the one-dimension AR model.This paper provides an AR order estimation method for a two-dimension AR model, and an AR model parameter estimation method on the basis of an autocorrelation function. A simulation example on surface profiles of some kinds of steel plates is given using this improved AR model with positive results.

基于水动力学模型和代理模型的水库动库容精细化计算

山区河道型水库存在较大动库容,库容计算不准确使得制定水库调度计划时出现较大偏差。根据水库水面线变化特点引入分段法将水库分段,并结合水动力学模型计算出水库动库容,实现水库动库容的精细化计算。同时针对水动力学模型在调度计划制定的实时计算中所面临的计算效率瓶颈,建立了基于RSMGU和RSLSTM的代理模型。以三峡水库为例,对基于水位—库容曲线所算得的静库容模型,水库动库容与之相比增大了约12%。以2020年汛期#4洪水为例,采用动库容法计算库容,可减小部分下泄流量,进一步发挥水库的防洪兴利能力;发现RSMGU更适合作为水动力学模型的代理模型。

基于质构仪TPA模式构建蛋白肠感官评分预测模型及应用

为建立一套客观、数据化评价动植物双蛋白肠感官综合评分的方法,该研究采用质构剖面分析(TPA)测定24组不同配方的样品,结合感官评价方法,通过逐步回归分析建立感官综合评分预测模型,并将其应用于响应面实验以优化双蛋白肠的配方。结果表明,动植物双蛋白肠的感官综合评分预测模型为Y=-68.110+0.003×硬度+79.119×弹性-0.001×咀嚼性-18.393×回复性,该模型相关系数R~2为0.902,校正决定系数R_(Adj)~2为0.875;响应面回归模型相关系数R~2为0.962,校正决定系数R_(Adj)~2为0.924,预测系数R_(Pred)~2为0.861,优化后蛋白肠的最佳配方为大豆拉丝蛋白质量分数74%、猪肉质量分数16%、大豆分离蛋白与花生蛋白粉比例7∶3、猪肉肥瘦比例7∶3,该配方下产品的感官评分实际值为8.51,与理论预测值(8.45)误差较小。该研究得到的动植物双蛋白肠感官综合评分预测模型的拟合度较高,实测值与预测值的吻合度较好,模型在响应面实验中具有可行性,为客观、快捷地评价新型肉肠的感官品质提供了新思路。

Spatio-temporal Evolution Characteristics and Driving Forces of Winter Urban Heat Island:A Case Study of Rapid Urbanization Area of Fuzhou City,China

Under the influence of anthropogenic and climate change,the problems caused by urban heat island(UHI)has become increasingly prominent.In order to promote urban sustainable development and improve the quality of human settlements,it is significant for exploring the evolution characteristics of urban thermal environment and analyzing its driving forces.Taking the Landsat series images as the basic data sources,the winter land surface temperature(LST)of the rapid urbanization area of Fuzhou City in China was quantitatively retrieved from 2001 to 2021.Combing comprehensively the standard deviation ellipse model,profile analysis and GeoDetector model,the spatio-temporal evolution characteristics and influencing factors of the winter urban thermal environment were systematically analyzed.The results showed that the winter LST presented an increasing trend in the study area during 2001–2021,and the winter LST of the central urban regions was significantly higher than the suburbs.There was a strong UHI effect from 2001 to 2021with an expansion trend from the central urban regions to the suburbs and coastal areas in space scale.The LST of green lands and wetlands are significantly lower than croplands,artificial surface and unvegetated lands.Vegetation and water bodies had a significant mitigation effect on UHI,especially in the micro-scale.The winter UHI had been jointly driven by the underlying surface and socio-economic factors in a nonlinear or two-factor interactive enhancement mode,and socio-economic factors had played a leading role.This research could provide data support and decision-making references for rationally planning urban layout and promoting sustainable urban development.

基于水动力耦合模型的城市内涝治理方案效果评估

为解决海南海口市龙昆沟流域的内涝问题,近期拟对龙昆沟下游段进行挖深等改造工程,远期采取优化排水分区等综合治理措施。基于InfoWorks ICM软件构建水动力学耦合模型,对近期、远期改造工程效果进行评估。结果表明:近期河道改造工程实施后,河道水位有所降低但对地表内涝缓解作用有限;远期流域规划工程实施后,河道水位明显降低且地表内涝情况明显改善,可达到预期效果。可见,通过加深河道断面从而增大过流断面面积,可有效降低河道水位,增大河道过流能力,但无法对地表内涝起到太大缓解作用;而通过优化排水分区等综合措施减少河道汇水面积,可明显降低河道水位,减少漫溢并改善地表内涝淹没情况。

HEC-RAS模型在河道治理工程水面线推求中的应用

为掌握山区复杂流态河流暴雨洪水特性,以吴上湾河大埠口村段河道治理工程为例,利用HEC-RAS软件构建迭代推演水面线分析模型,并结合流域特征值及设计洪水成果,模拟获得控制断面治理前后10年一遇洪水条件下的河道水面线数据。分析结果表明:治理前河道滩地上沙场侵占行洪断面,导致河道水位壅高。通过主河槽扩挖补偿和混凝土挡土墙护岸等措施治理后,河道流速降低、行洪能力增加。HEC-RAS软件对于天然河道复杂流态水文水力计算具有较强适用性,推求数据合理可信。

基于MIKE11的鉴江干流堤防防洪能力分析

鉴江干流堤防防洪能力分析对鉴江流域的防洪减灾具有重大意义,而设计水面线成果是分析堤防防洪能力的重要依据。基于MIKE11模型,通过率定验证,构建鉴江干流一维水动力学模型,计算了P=1%、2%、3.33%、5%、10%工况下的水面线,结果表明,设计水面线成果合理,能较好地反映近年人类活动和上游来水来沙条件改变对鉴江干流水位的影响。经分析,鉴江干流未达标需治理堤防总长69.76 km,表明沿岸防洪形势依然严峻,系统达标治理必要且迫切。

Ocean Data Assimilation Using Intermittent Analyses and Continuous Model Error Correction

A new data insertion approach is applied to the Derber and Rosati ocean data assimilation (ODA) system, a system that uses a variational scheme to analyze ocean temperature and provide ocean model corrections continuously. Utilizing the same analysis component as the original system, the new approach conducts analyses to derive model corrections intermittently at once-daily intervals. A technique similar to the Incremental Analysis Update (IAU) method of Bloom et al. is applied to incorporate the corrections into the model gradually and continuously. This approach is computationally more economical than the original.A 13-year global ocean analysis from 1986 to 1998 is produced using this new approach and compared with an analysis based on the original one. An examination of both analyses in the tropical Pacific Ocean shows that they have qualitatively similar annual and interannual temperature variability. However, the new approach produces smoother monthly analyses. Moreover, compared to the independent

A 3D analytical model for vortex velocity field based on spiral streamline pattern

Vortices that develop over intakes are a hazardous hydraulic phenomenon.In this study, a 3D model was developed to study the flow field in air-core vortices.This model is based on the spiral pattern of streamlines and the analytical solution of the momentum and continuity equations for deriving the three components of velocity.The model provides equations for free surface profiles and 3D patterns of the streamlines.Moreover, a new relationship was suggested for calculating effective viscosity and its distribution across the vortex flow field.The performance of the proposed analytical model was compared with existing experimental data and the results of previous analytical models.The outcomes indicated that the proposed model could predict characteristics of the vortex flow with good accuracy.

多源遥感土壤湿度产品与水文模拟结果的时空对比分析

为实现土壤湿度连续准确的时空刻画,在不同气候条件下进行多源遥感土壤湿度产品(SMOS、ASCAT、ESA CCI、SMAP)与分布式降雨径流模型模拟土壤湿度时空对比研究。考虑到遥感数据与模型模拟数据时空匹配度上的差异性,将遥感原始表层土壤湿度(Surface Soil Moisture,SSM)和预处理后的剖面土壤湿度(Profile Soil Moisture,PSM)与分布式水文模型模拟的PSM分别进行对比。对比所用时间尺度为日尺度,空间尺度为流域尺度和栅格尺度。研究区域为湿润气候条件下的渠江流域和半干旱气候条件下的伊洛河流域。结果表明,在同一流域内当分布式水文模型土壤湿度模拟能力较高时,SMAP反演PSM与模型模拟值一致性较高,相关系数达到0.8,相对其他遥感产品其准确度较高。研究成果对获取高准确度土壤湿度时空信息具有一定的指导意义和实践价值。

光学芯轴测量台四点自动调平方法研究

针对Wolter-I型芯轴装调、测量过程中需要多次调平,时刻保持平衡的问题,研究了四点式自动调平方法。从机械、软件两个方面介绍自动调平测量台,分析调平控制机构以及相关软件,用表面轮廓数据采集方法进行数据采集确定倾斜角,对“最高点不动”调平算法进行数学建模,对倾斜角的不同种情况进行仿真计算分析,计算随机产生的倾角对应的支腿移动量。实验结果表明:该方法用5~7次即可达到调平目的,具有较高的检测效率、调平精度和抗倾覆力。

基于MIKE11模型的东江干流水面线演变分析

为研究近年来东江干流水面线的演变情况,基于MIKE11模型软件构建了东江干流一维水动力学模型,并分别采用2019年6月和2020年6月的洪水进行模型的率定和验证。用本次率定的模型进行水面线计算并与1991年行洪控制线和2005年水面线相比较,结果表明东江干流自20世纪80年代以来河床不断下切,导致相同流量下水位有下降趋势,符合实际情况。计算成果可为东江干流防洪治理工程的堤防、建筑物设计提供参考。

基于多元优化的百米级胶凝砂砾石坝设计方法

随着胶凝砂砾石坝(CSG坝)筑坝技术的提高,对百米级CSG坝的建造需求不断增加,亟需对不同剖面形式和胶凝含量的百米级CSG坝进行研究。本文采用有限元法建立CSG坝响应面预测模型回归方程;将预测模型回归方程作为目标函数,运用人工蜂群算法对CSG坝剖面形式及胶凝含量进行优化,得到一系列最优剖面解集;选取一组优化模型与实际工程开展模型试验进行对比验证。结果表明:两组模型在加载过程中的破坏模式不同,实际工程模型坝体与坝基接触面出现裂缝并逐渐发生贯通,坝踵处出现剪切裂缝破坏;优化模型发生滑移失稳破坏,坝体本身未见明显结构破坏,说明优化模型的结构强度得到了增强;正常工况下,优化模型较实际工程水平位移减小了36.9%,竖直位移减小了25.5%,超载安全系数增大了9.1%。结果为实际工程中CSG坝的剖面形式优化和百米级CSG坝的建造提供参考。

三维地质建模在煤矿地面塌陷范围预测中的应用研究--以宁东羊场湾煤矿为例

利用钻孔、测井、地震、测绘以及煤矿开采等多源数据,构建羊场湾矿区初始三维地质模型。利用宁东矿区覆岩“三带”高度及平面分布范围,构建煤矿开采后地表沉陷的模型。通过前后2个模型的对比可以展示煤矿采煤后的地层沉降程度和地表塌陷范围,分析地面塌陷的发展趋势,实现对宁东地区采空区预防治理工作的预警。

基于耦合热传导-冰流模型的冰川钻孔温度重建的气候反演算法比较

冰川内部温度与冰面温度变化过程密切相关,因此可由实测冰温-深度剖面重建冰面温度变化。耦合热传导-冰流物理模型及其相关反演算法是基于冰温-深度剖面重建冰面温度变化的理论基础和关键。通过构造理想条件下的数值实验,分析比较了最小二乘法、Tikhonov正则化方法和蒙特卡罗算法重建百年尺度冰面温度变化的实验结果。同时,以我国藏北高原腹地的马兰冰川钻孔资料为例,结合气象资料构造真实钻孔数据模拟实验。分别给出了三种反演算法重建10 a和40 a尺度的冰面温度变化结果,并讨论了不同算法的优劣性和适用性。两组模拟实验结果均表明:Tikhonov正则化方法是目前求解该反问题的最优方法。与其他算法相比,Tikhonov正则化方法在各个时间尺度的重建结果与真实冰面温度变化吻合更好。另外,分别对重建百年和40 a尺度的冰温-深度剖面添加±0.02℃和±0.01℃的随机误差,研究发现Tikhonov正则化方法能够有效降低噪声干扰,相较其他算法得到的解更加稳定。这在一定程度上解决了该反问题中解的稳定性问题。