Experimental investigation of limestone of the Faiyah Range area,United Arab Emirates

The paper presents results of a laboratory experimental program performed on limestone rock samples, using both physical and mechanical methods. The studied rocks (Simsima Formation, Upper Cretaceous) can be classified as highly ferruginous and highly fossilliferous limestone. The lower part of the Simsima Formation contains common fauna such as Orbittoids, rhodolithic and rudists, whereas the upper part of the limestone is interbedded with conglomerates. Detailed geological, petrographic in addition to physical and mechanical tests were carried out on some representative samples from the Faiyah area, aiming at getting a better understanding of the important properties of these rocks. It is shown that the uniaxial unconfined compressive stress is the controlling factor of classification of the Faiyah limestone.     

敏感环境下基坑数值分析中土体本构模型的选择

数值分析已成为敏感环境下基坑工程分析的最重要手段,其关键是选择合适的土体本构模型和计算参数。在分析了岩土数值分析中常用土体本构模型特点的基础上,通过算例较系统地对比了各类模型在基坑开挖数值分析中的适用性。敏感环境下的基坑工程需重点关注墙后土体的变形,从满足工程需要和方便实用的角度出发,建议采用能考虑黏土的塑性和应变硬化特征、能区分加荷和卸荷且刚度依赖于应力水平的硬化类弹塑性模型,如MCC模型和HS模型进行分析。具体工程实例的分析,表明了硬化类弹塑性模型在敏感环境下基坑开挖数值分析中的适用性。     

氮添加降低了半干旱草原土壤呼吸但未改变其温度敏感性

半干旱生态系统土壤呼吸(Rs)对氮添加的响应机制仍有待探索。本研究在中国半干旱草原设置不同氮添加水平(0、2、4、8、16、32 gN m-2 yr-1),测定土壤呼吸速率、土壤温湿度、微生物磷脂脂肪酸、土壤理化性质与地上生物量等指标,探讨氮添加对土壤呼吸及其温度敏感性(Q10)的影响。结果表明:氮添加显著增加了土壤可溶性有机碳(DOC)和无机氮(IN)的含量,降低了土壤pH值,对地上生物量(ABM)无显著影响。氮添加降低了磷脂脂肪酸(PLFAs)的总量,降低了真菌细菌比(F:B),提高了革兰氏阳性阴性菌比(G+:G–)。氮添加显著降低了土壤呼吸,N2、N4、N8、N16和N32处理下的土壤呼吸分别比对照N0变化了–2.58%、14.86%、22.62%、23.97%和19.87%,结构方程模型表明,氮添加通过降低PLFAs总量和改变微生物组成降低土壤呼吸。氮添加对温度敏感性(Q10)、土壤总有机碳(TOC)和总氮(TN)的影响均不显著,表明氮添加减轻了土壤碳的损失,且不会改变全球变暖背景下土壤有机碳矿化的潜力。     

闽浙沿岸沉积物的工程地质特性及其成因简析

根据闽浙沿岸沉积物的实验室分析资料,从物理性质和力学特征对海底沉积物的综合工程地质特征进行了研究,结果发现,本区沉积物以淤泥和淤泥质黏土为主,含少量细砂、粉砂、黏土和粉质黏土等,总的表现为含水率高、孔隙比大、压缩性强、塑性大和强度低。从微观结构、物质来源、物质成分、水动力条件等方面对沉积物的工程特性进行了成因分析,这些因素是造成本区沉积物工程性质不良的主要原因。     

Er3+/Yb3+共掺TeO2-WO3-Bi2O3玻璃的光谱性质和上转换发光

本文制备了Er³⁺/Yb³⁺共掺TeO₂-WO₃-Bi₂O₃(TWB)玻璃. 测试和分析了样品的吸收光谱、荧光光谱及上转换发光. 用Judd-Oflet(J-O)理论计算了Er³⁺在玻璃样品中的光谱强度参数,随着Bi₂O₃含量的增加,Ω₂增加,Ω₄     

In掺杂对n型方钴矿化合物的微结构及热电性能的影响规律

用熔融退火法结合放电等离子烧结(SPS)技术成功制备了具有不同 In含量的In_xCo₄Sb₁₂(x=0.1—0.4)方钴矿化合物.X射线衍射分析和扫描电镜分析结果表明,当In的掺杂量超过一定值时,化合物中会原位析出纳米InSb的第二相,且其含量会随In掺杂量的增加而增大.研究结果表明,InSb第二相的存在增大了化合物的功率因子,降低了化合物的晶格热导率,显著提高了化合物的热电性能.在温度为800 K时,In相似文献   

Comparison between petroleum hydrocarbon concentrations and magnetic properties in Chennai coastal sediments,Bay of Bengal,INDIA

Petroleum hydrocarbon concentrations (PHC) of surface sediments along the Chennai coast, India, were measured by UV-Fluorescence (UVF) Spectroscopy and the results are expressed in terms of Chrysene equivalents. The concentration of PHC in sediment varies widely (from 1.88 ppm to 39.76 ppm) as compared to the baseline (1.88 ppm) with higher values obtained in the northern part of the study area. The highest magnetic susceptibility (96.8 × 10⁻⁸ m³kg⁻¹) value was determined from the Chennai harbour area. The magnetic parameters show that the Chennai coastal sediments are dominated by ferrimagnetic minerals. The positive correlation (r² = 0.86; p < 0.05) between petroleum hydrocarbon concentrations and magnetic susceptibility suggests that the magnetic minerals and petroleum hydrocarbons along the Chennai coast are derived from the same sources. Factor analysis shows that the magnetic concentration dependent parameters (χ, χ_ARM and SIRM) covary with the petroleum hydrocarbon concentration, suggesting that large amounts of magnetic minerals originate from anthropogenic activities. It is evident that using magnetic measurements may be considered a simple, rapid, cheap and non-destructive method to determine petroleum hydrocarbon concentrations in coastal sediments. Furthermore, this technique may be applied to petroleum exploration studies. Magnetic susceptibility measurements in sediments have been proposed as complementary or alternative means of exploration and assessment of hydrocarbon reservoirs.     

Negative differential resistance behaviour in N-doped crossed graphene nanoribbons

By using first-principles calculations and nonequilibrium Green's function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance (NDR) behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.     

商河油田古近系碎屑岩储层及同沉积断层对其控制作用

商河地区为自北向南成明显阶梯状分布的多级构造调节带及多级坡折带,受其构造特征影响,储层特征也表现出明显的规律性。通过对商河地区大量储层物性数据的统计,结合镜下薄片观察发现商河油田具有同一层位,自北向南,商一区、商二区、商三区、商四区储层物性依次变差的特点;而对于同一地区,整体上自上向下随深度增加储层物性逐渐变差;同一层位不同沉积微相的储层具有不同的物性特征,三角洲前缘河口坝砂体储层物性最好,水下分支河道较好,而远砂坝、席状砂砂体储层物性相对较差。经综合研究分析认为储层特征主要受沉积相及成岩作用共同影响,储层成岩作用主要受地层埋深的影响,而由于商河地区的分界大断层主要为同沉积断层,地层厚度和沉积相分布主要受同生断层活动的影响,因此构造作用的同沉积断层是商河地区储层物性的主要控制因素。     

粘性类土侵蚀强度量化研究

海洋动力作用下,粘性土内部粘结力与重力的联合作用使其冲刷侵蚀特性较为复杂。从侵蚀原理出发,利用粘结力仪进行侵蚀试验,探讨了粘性土临界侵蚀剪应力τ_c与土体物理力学性质之间的相关性,并提出中值粒径、粘粒含量、密度及抗剪强度与τ_c之间的计算关系式。同时通过侵蚀公式计算结果与试验结果比较,验证了试验结果的准确性。