最大可能输沙量的工程计算

输沙量是一个重要的物理量和极其有用的工程参数。它是一个复合向量,具有明显的空间分布的非均一性和随时间变化的非定常性。文中把最大可能输沙量定义为输沙量的理论极限值,并根据最大可能输沙率的实验关系式,利用风的自计记录,计算了一个地区不同风向(16个方位),一年内最大可能输沙量的总和。按向量合成原理,计算了该地区的最大可能合成输沙量与合成输沙方向,其结果与该地区主体沙丘的平均移动速度和移动方向具有较好的一致性。     

异常温压条件下水文地质参数实验室计算方法的研究

异常温压条件下的渗透系数和弹性储水系数是评价深层地下水资源量的关键水文地质参数。本文针对目前国内外在深层地下水资源评价研究中,沿用浅层地下水的非稳定井流试验求参数所造成的弊端,考虑到深层地下水因埋藏深度很大而形成的异常温压条件,提出了通过实验室测定岩样,水样的弹性模量、泊松比、孔隙度、渗透率、液体体积压缩系数、粘滞系数等,进而计算深层地下水所处的特定环境中的水文地质参数的方法。     

四种浮游植物生物量计算方法的比较分析

浮游植物是水生生态系统中重要的初级生产者,其生物量是反映其现存量的关键指标.本文利用具有3个处理组的围隔实验中的浮游植物数据,对文献中常见的计算浮游植物种群生物量和群落生物量的4种方法:标准法、细分法、粗分法和资料法进行比较,并分析采用这4种不同方法得到的浮游植物生物量与叶绿素a浓度的相关性.结果表明:粗分法是计算浮游植物生物量的高效方法,能够保证准确度和节省时间;提高浮游植物生物量计算准确度不是影响浮游植物生物量与叶绿素a浓度相关性显著程度的关键.通过比较剔除稀有种(生物量不超过群落生物量5%的种类)前后浮游植物生物量的差异,发现忽略稀有种会导致种类均匀度较高的浮游植物群落生物量严重偏低,建议浮游植物生物量的计算不能一概忽略稀有种.     

水库库容变化对蓟县地震台DSQ型水管倾斜仪观测的影响

对比于桥水库库容变化与蓟县地震台DSQ型水管仪观测数据表明,水库容量对水管仪长周期趋势性变化影响不大,蓄水和泄水过程中库容量变化与水管仪观测数据不存在相关关系。根据近场三维不规则形状荷载模型,对于于桥水库3次蓄水和3次泄水过程,定量计算库容变化对蓟县地震台DSQ型水管倾斜仪观测影响的理论值,结果表明,库容变化引起的水管仪倾斜值与实际观测数据变化幅度相比小得多,库容改变不足以对水管仪倾斜观测造成显著干扰。该分析结果可在观测资料异常判定中提供参考。     

地质统计学在煤炭储量评价中的应用

储量评价是矿床地质可靠性评价的核心内容,也是采矿工程中的关键环节。地质统计学方法用于储量评价有很大的优越性。本文叙述了运用地质统计学方法进行储量评价的步骤,并对胜利煤田一号露天矿6号煤做了储量评价。      

Mallat算法在数字地震信号压缩中的应用

地震台站多、数据采集量大,日产出数据量庞大,研究数字地震信号的压缩方法成为行业热门课题。尝试将Mallat算法应用于数字地震波形数据压缩。选取不同的小波分解函数,对不同类型的数字地震信号进行3—5层的小波分解,将得到的小波系数进行分层硬阈值重构运算,对原始信号和处理信号进行压缩。分析可知,Mallat算法压缩比更高,与原始信号相比,重构信号不失真、能量保留系数高。     

Application of Bayesian model and discriminant function analysis to the estimation of sediment source contributions

Bayesian and discriminant function analysis (DFA) models have recently been used as tools to estimate sediment source contributions. Unlike existing multivariate mixing models, the accuracy of these two models remains unclear. In the current study, four well-distinguished source samples were used to create artificial mixtures to test the performance of Bayesian and DFA models. These models were tested against the Walling-Collins model, a credible model used in estimation of sediment source contributions estimation, as a reference. The artificial mixtures were divided into five groups, with each group consisting of five samples with known source percentages. The relative contributions of the sediment sources to the individual and grouped samples were calculated using each of the models. The mean absolute error (MAE) and standard error of (SE) MAE were used to test the accuracy of each model and the robustness of the optimized solutions. For the individual sediment samples, the calculated source contributions obtained with the Bayesian (MAE = 7.4%, SE = 0.6%) and Walling-Collins (MAE = 7.5%, SE = 0.7%) models produced results which were closest to the actual percentages of the source contributions to the sediment mixtures. The DFA model produced the worst estimates (MAE = 18.4%, SE = 1.4%). For the grouped sediment samples, the Walling-Collins model (MAE = 5.4%) was the best predictor, closely followed by the Bayesian model (MAE = 5.9%). The results obtained with the DFA model were similar to the values for the individual sediment samples, with the accuracy of the source contribution value being the poorest obtained with any of the models (MAE = 18.5%). An increase in sample size improved the accuracies of the Walling-Collins and Bayesian models, but the DFA model produced similarly inaccurate results for both the individual and grouped sediment samples. Generally, the accuracy of the Walling-Collins and Bayesian models was similar (p > 0.01), while there were significant differences (p < 0.01) between the DFA model and the other models. This study demonstrated that the Bayesian model could provide a credible estimation of sediment source contributions and has great practical potential, while the accuracy of the DFA model still requires considerable improvement.     

Remotely-sensed phenology of Italian forests: Going beyond the species

Remotely sensed observations of seasonal greenness dynamics represent a valuable tool for studying vegetation phenology at regional and ecosystem-level scales. We investigated the seasonal variability of forests in Italy, examining the different mechanisms of phenological response to biophysical drivers. For each point of the Italian National Forests Inventory, we processed a multitemporal profile of the MODIS Enhanced Vegetation Index. Then we applied a multivariate approach for the purpose of (i) classifying the Italian forests into phenological clusters (i.e. pheno-clusters), (ii) identifying the main phenological characteristics and the forest compositions of each pheno-cluster and (iii) exploring the role of climate and physiographic variables in the phenological timing of each cluster. Results identified four pheno-clusters, following a clear elevation gradient and a distinct separation along the Mediterranean-to-temperate climatic transition of Italy. The “High-elevation coniferous” and the “High elevation deciduous” resulted mainly affected by elevation, with the former characterized by low annual productivity and the latter by high seasonality. To the contrary, the “Low elevation deciduous” showed to be mostly associated to moderate climate conditions and a prolonged growing season. Finally, summer drought was the main driving variable for the “Mediterranean evergreen”, characterized by low seasonality. The discrimination of vegetation phenology types can provide valuable information useful as a baseline framework for further studies on forests ecosystem and for management strategies.     

确定似大地水准面的Hotine-Helmert边值解算模型

空间大地测量技术的发展使大地高的观测成为可能,从而为第二大地边值问题的研究带来了新的机遇,本文对基于Helmert第二压缩法的第二边值问题(简称为Hotine-Helmert边值问题)展开研究。首先介绍了地形直接、间接影响的定义与算法,然后推导了Hotine-Helmert边值问题的解算模型。Hotine-Helmert边值理论无须计算地形压缩对重力的次要间接影响,因而较Stokes-Helmert边值理论更简单。此外,文中引入了一种低阶修正的Hotine截断核函数,该核函数较传统的截断核函数能有效地改善似大地水准面的解算精度。为了验证本文构建的Hotine-Helmert边值解算模型的有效性和实用性,本文将EIGEN-6C4模型的前360阶作为参考模型,利用Hotine-Helmert边值解算模型构建了我国中部地区6°×4°范围、1.5′×1.5′分辨率的重力似大地水准面,其精度达到±4.8 cm。     

珊瑚砂地质条件下钢板桩结构可靠性分析

在热带地区开展水运工程设计施工项目,经常会遇到珊瑚砂地质,其力学特性较为特别,强度低、易碎、黏性低,力学指标变异性较大,国内现有设计规范对珊瑚砂地质条件特殊性考虑不足,设计人员在相关设计参数选取时经常忽略采用可靠度理论进行结构安全复核。以马尔代夫机场扩建项目为案例,运用可靠度理论分析了珊瑚砂力学指标的高变异性对钢板桩结构稳定可靠度的影响。根据分析,在珊瑚砂地质条件下,按照《码头结构设计规范》（JTS167-2018）进行稳定性计算,得出的结果偏于危险,应引起结构设计人员的重视。在进行结构设计时,应同时按照《港口工程结构可靠性设计统一标准》（GB50158-2010）复核板桩结构可靠度。同时,珊瑚砂较小的黏性,在进行结构可靠度计算时可以忽略。