颗粒劣化效应的堆石料流变细观数值模拟

堆石料流变的主要机理是由于水位变化、降雨入渗、日晒雨淋等环境因素导致堆石料发生性质劣化,与此同时,颗粒发生高接触应力-破碎和重新排列-应力释放、调整和转移,这一过程由于颗粒的持续劣化而不断重复。在考虑颗粒破碎的堆石体不连续变形分析方法(SGDD)中,引入颗粒强度劣化模型反映颗粒强度随外界环境的持续劣化。应用该方法进行堆石料三轴流变数值试验,模拟结果与室内试验所观察到的规律一致,表明考虑流变效应的SGDD方法抓住堆石料流变的主要机理,适合模拟堆石料的流变变形这一复杂的、非线性演化问题。数值试验结果表明,堆石料随外界环境的劣化程度、劣化速率、母岩强度对宏观流变变形有较大影响。     

广域电磁与伪随机信号电磁法在四川盆地页岩气勘探中的应用

广域电磁与伪随机信号电磁法采用伪随机信号发射,突破远区限制,可观测面积大,信号强、精度高、只观测场的一个分量,野外效率高。伪随机信号电磁法一次能同时发送和接收多个强度大体相当的主频率信号,成倍地提高电磁法的野外效率。本文将广域电磁与伪随机信号电磁法应用于四川盆地某页岩气区块,结果表明它在干扰较强的地区仍然能够获得深部5～6km的有效数据,具有抗干扰能力强、勘探深度大的优点;同时广域电磁法在大套地层划分、油气层识别、断层及构造识别方面的效果显著。     

基于信息量模型与随机森林模型的崩岗风险对比评估

崩岗是发生在我国南部地区一种典型的水土流失现象,对其进行风险评估有利于崩岗防控.建立崩岗风险评估体系和崩岗评估模型是崩岗风险评估的基础,而不同的评估模型对崩岗风险的评估结果存在差异.探究不同模型在崩岗风险评估中的应用差异,提高预测精度是目前亟需解决的问题.本研究以福建省安溪县龙门镇小流域为例,根据风险因子与崩岗发生之间...     

资源环境保护下天津市用地空间增长模拟

从资源承载和生态保护的角度预测城镇土地利用变化,是实现国土空间用途管制的客观需求。以典型缺水城市天津市为研究区,采用系统动力学模型预测土地利用规模、最小成本路径法构建生态廊道和FLUS模型模拟土地利用变化等方法,分别模拟自然扩张和资源环境保护情景下天津市2035年土地利用情况。结果表明：① 资源约束条件显著制约城镇人口和建设用地的超量发展,随着资源约束增强、科技发展增速,人口和建设用地增长量随之降低,城镇GDP保持稳定增长。② 天津市重要生态廊道以南北向联系为主,东部和北部生态廊道重要性较高,部分生态廊道由于路径较长或距离建设用地较近而面临被蚕食挤压的风险。③ 水体湿地在资源环境保护情境下面积略有增长,在自然扩张情境下则延续以往不可持续的发展模式,出现向草地退化的情况,部分生态源地和廊道受到耕地侵占和建设用地扩张的影响。④ 受交通发展和京津职住分离的影响,天津市城镇建设用地增长主要发生在蓟州、武清和宝坻区。此外,在资源环境保护情景下,中心城区和滨海新区增长率较低,津南区表现出较大发展潜力。以资源环境承载约束城镇扩张,能够为国土空间规划实践提供科学引导。     

黑土区土壤有机质和全氮含量遥感反演研究

以东北典型黑土区耕地为研究区,以Sentinel-2A（全球环境与安全监测计划的第二颗卫星,于2015年6月23日发射）影像作为数据源,构建光谱指数,分别采用多元逐步线性回归（Multiple Stepwise Linear Regression, MSLR）和随机森林（Random Forest, RF）算法建立土壤有机质（SOM）和土壤全氮（STN）预测模型,并采用十折交叉验证方法评估模型的性能。研究对比分析了不同气候、土壤类型和地形下土壤有机质和全氮的空间分布差异。研究表明：① 海伦示范区的SOM和STN含量最高,其年均温最低,高程最高,年降水量多,SOM含量升高,其年均温最低,年降水量多,STN含量升高;② 与基于多元逐步线性回归算法建立的SOM和STN预测模型相比,随机森林算法建立的SOM和STN预测模型,有着更高的精度和稳定性;③ 运用RF算法建立的SOM反演模型的R²为0.96,均方根误差为5.49 g/kg,STN反演模型的R²为0.95,均方根误差为0.27 g/kg; ④ 不同示范区统一建立SOM和STN预测模型,有助于提高预测精度,实现跨区域建模与制图。     

Measuring the velocity of sand particles in an air/particle two-phase flow: A comparison of several commonly used methods

The velocity of blown sand particles is an important parameter in aeolian movement （a special case of gas particle two-phase flow） and has ever been a topic of interest. At present, several techniques have been applied in measuring velocity of the blown sand particles. This paper reviews the measurement results of several commonly used methods： photoelectric cell method, high-speed photographic method, Particle Dynamics Analyzer （PDA） method and Particle Image Velocimetry （PIV） method. Photoelectric cell method, high-speed photograph method and PDA method are useful in studying the velocity distribution of particles. PIV is a whole-flow-field technique and a useful tool to study the average velocity field in a target area. These methods got some similar results but considerable differences also exist. They have come to similar conclusions on the velocity distributions at a single height but direct measurement results with respect to the velocity distribution very close to the surface are still scarce except some PDA results. The magnitude of measured mean particle velocity differs greatly. The relationship obtained by different methods between mean particle velocity and wind velocity, particle size and possibly other influencing factors also differs considerably. Although several authors have proposed similar power functions to describe the variation with height of the mean particle velocity, the predicted results have wide differences. Each technique is based on some unique principles, and has its advantages and disad- vantages. To make full use of different techniques, a lot of work needs be done to validate them. Developing a reliable technique to measure the velocity of blown particles is still a necessary task in aeolian research.     

中国天气发生器的降水模拟

A stochastic model for daily precipitation simulation in China was developed based on the framework of a ‘Richardson-type‘ weather generator that is an important tool in studying impacts of weather/climate on a variety of systems including ecosystem and risk assessment. The purpose of this work is to develop a weather generator for applications in China. The focus is on precipitation simulation since determination of other weather variables such as temperature is dependent on precipitation simulation. A framework of first order Markov Chain with Gamma Distribution for daily precipitation is adopted in this work. Based on this framework, four parameters of precipitation simulation for each month at 672 stations all over China were determined using daily precipitation data from 1961 to 2000. Compared with previous works, our estimation for the parameters was made for more stations and longer observations, which makes the weather generator more applicable and reliable. Spatial distributions of the four parameters are analyzed in a regional climate context. The seasonal variations of these parameters at five stations representing regional differences are discussed.Based on the estimated monthly parameters at 672 stations, daily precipitations for any period can be simulated. A 30-year simulation was made and compared with observations during 1971-2000 in terms of annual and monthly statistics. The results are satisfactory, which demonstrates the usefulness of the weather generator.     

洪泽湖湿地发现大面积6米高以上原生野生芦苇

在北纬33°18′,东经118°13′．洪泽湖溧河洼湿地滩涂发现一片原生野生高大芦苇,面积约500亩。芦苇高度6,05～6．30米。地上部分39～42节,叶长75厘米,叶宽5厘米。芦苇花长50厘米,花宽最大58厘米,节最长达33厘米,根径2．2～29厘米。随机调查每平方米有芦苇22株,单株重达0．8公斤左右,每亩约13000多株。亩产量5～7吨。     

粒子图像测速(PIV)技术在风沙环境风洞中的应用

粒子图像测速技术是一种全新的非接触、瞬时、全场流速测量方法,广泛应用于流体力学实验中。笔者将其引入风沙运动研究是一个尝试,旨在为风沙物理和防沙工程研究提供新的测量手段。通过分析一系列的风洞实验结果,我们认为,在风沙流中颗粒速度分布、浓度分布、风沙地貌形成演化、防沙工程原理及应用方面,粒子图像测速技术具有一定优势,可以克服传统测量手段的某些不足。     

直立阻沙栅栏流场特征的风洞模拟实验

直立栅栏作用于地表深刻地影响了周围气流的流动特性,使原来流经地表的气流成为一种特殊形式的“次生流”。根据PIV所测的非对数-线性风速廓线形态及风速廓线所表现的不同速度梯度,栅栏周围的流场可以划分为6个典型区域。随着栅栏疏透度的增加,流动的区域会随着下风向距离的增加逐渐合并,划分的区域越来越少。这些典型的区域分别表现了气流的不同运移行为及能量传输特征,对栅栏周围的风沙沉积有很大的影响。