春季长江口及邻近海域悬浮颗粒态硅的研究   总被引：2，自引：0，他引：2  

曹璐  刘素美  李瑞香 《海洋学报》2011,33(1):83-90

对春季长江口及邻近海域悬浮颗粒态生物硅(PBSi)、成岩硅(LSj)进行了大面调查和围隔培养实验研究,讨论了悬浮颗粒物中PBSi的分布情况及其影响因素.分析表明,PBSi与LSi的含量分别为0.22～4.25和1.75～184μmol/dm<'3>,与世界其他海域相比LSi的含量偏高,PBSi含量则处于中等水平.由于陆...  相似文献   

Computer experiments to investigate complex fibre patterns in natural antitaxial strain fringes     

D. Koehn  D. G. A. M. Aerden  P. D. Bons  C. W. Passchier 《Journal of Metamorphic Geology》2001,19(2):217-231

Antitaxial non‐deforming strain fringes from Lourdes, France, show complex quartz, calcite and chlorite fibre patterns that grew around pyrite in a slate during non‐coaxial progressive deformation. Development of these fringes was modelled using a computer program ‘Fringe Growth 2.0’ which can simulate incremental growth of crystal fibres around core‐objects of variable shape. It uses object‐centre paths as input, which are obtained from fibre patterns in thin section. The numerical experiments produced fibre patterns that show complex intergrowth of displacement‐controlled, face‐controlled and intermediate fibres similar to those in the natural examples. The direction of displacement‐controlled growth is only dependent on the relative movement between core‐object and fringe, so that core‐object rotation with respect to the fringe influences the fibre patterns and produces characteristic asymmetric fibre curvature. Object‐centre paths should be used for kinematic analysis of strain fringes instead of single fibres since these paths represent the fringe as a whole. The length along the path can be interpreted in terms of finite strain and path curvature in terms of rigid body rotation of fringes with respect to an external reference frame.  相似文献   

Bond rolling resistance and its effect on yielding of bonded granulates by DEM analyses     

M. J. Jiang  H. S. Yu  D. Harris 《国际地质力学数值与分析法杂志》2006,30(8):723-761

A discrete element modelling of bonded granulates and investigation on the bond effect on their behaviour are very important to geomechanics. This paper presents a two‐dimensional (2‐D) discrete element theory for bonded granulates with bond rolling resistance and provides a numerical investigation into the effect of bond rolling resistance on the yielding of bonded granulates. The model consists of mechanical contact models and equations governing the motion of bonded particles. The key point of the theory is that the assumption in the original bond contact model previously proposed by the authors (55th CSCE‐ASCE Conference, Hamilton, Ont., Canada, 2002; 313–320; J. Eng. Mech. (ASCE) 2005; 131 (11):1209–1213) that bonded particles are in contact at discrete points, is here replaced by a more reliable assumption that bonded particles are in contact over a width. By making the idealization that the bond contact width is continuously distributed with the normal/tangential basic elements (BE) (each BE is composed of spring, dashpot, bond, slider or divider), we establish a bond rolling contact model together with bond normal/tangential contact models, and also relate the governing equations to local equilibrium. Only one physical parameter β needs to be introduced in the theory in comparison to the original bond discrete element model. The model has been implemented into a 2‐D distinct element method code, NS2D. Using the NS2D, a total of 86 1‐D, constant stress ratio, and biaxial compressions tests have been carried out on the bonded granular samples of different densities, bonding strengths and rolling resistances. The numerical results show that: (i) the new theory predicts a larger internal friction angle, a larger yielding stress, more brittle behaviour and larger final broken contact ratio than the original bond model; (ii) the yielding stress increases nonlinearly with the increasing value of β, and (iii) the first‐yield curve (initiation of bond breakage), which define a zone of none bond breakage and which shape and size are affected by the material density, is amplified by the bond rolling resistance in analogous to that predicted by the original bond model. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Excitation of ion waves by charged dust beams in ionospheric aerosol release experiments     

M. Rosenberg  P.A. Bernhardt 《Planetary and Space Science》2011,59(4):312-318

Ion waves excited by charged dust beams streaming across or along the geomagnetic field in the ionosphere may be generated by plasma instabilities during aerosol release experiments. The injection speed of the dust and gas is comparable to or larger than the ion thermal speed in the background plasma. The dust grains can get charged by plasma collection from the ambient ionosphere, and can thus act as a charged beam that excites instabilities in the background plasma. The theory is applied to relatively early time scales of the order of in the dust-gas cloud expansion, with wave frequencies that are larger than the ion gyrofrequency, and collisions with neutrals are included.  相似文献   

数字摄影测量学专业课教学的探索与实践     

徐芳  邓非  朱惠萍 《东北测绘》2014,(1):3-4,8

针对数字摄影测量学专业课教学,提出了开放式阅读和走出教室、走入企业的思想,并辅以具有针对性的设计性实验。引导学生阅读本领域内的相关文献,指导学生了解本学科的应用领域和研究热点与难点,了解当前企业在本领域的发展前沿,拓宽学生视野,为学生的就业和深造建立感性认识,设计性实验加强学生综合运用多门学科知识的能力,增强学生的探索能力和解决问题能力,为学生日后的生产应用和科学研究奠定基础。  相似文献   

规则波和不规则波条件下射流实验对比          下载免费PDF全文

徐振山  陈永平  张长宽  王娅娜 《水科学进展》2013,24(5):715-721

利用三维声学多普勒流速仪分别对规则波和不规则波条件下垂向圆管射流的流场进行了测量。在规则波条件下,靠近自由表面的射流垂向速度横剖面出现了较为明显的"双峰"现象,相较而言不规则波条件下射流垂向速度横剖面保持更好的高斯分布,"双峰"现象更不明显。在波能密度和波能通量一致的比选原则下,射流在规则波条件下的轴线速度衰减在初始段较不规则波条件要快一些,这与上述 "双峰"现象存在一定的关系。  相似文献   

Collisional disruption experiments of porous targets     

Akiko M. Nakamura  Kensuke Hiraoka  Nagisa Machii 《Planetary and Space Science》2009,57(2):111-118

More and more small bodies are found to be porous. Laboratory impact experiments of various porous materials have been performed, which increased our understanding of the impact process of porous bodies. In this review, we classify porous targets according to the internal structure, describe the physical properties that characterize these materials, and summarize some results of impact strength and the general tendency upon impact condition and material properties. The material property presented here includes a relation between applied load and distension although measured in static condition. Further investigation is required to clarify the role of crack growth and compaction in the time evolution of physical properties of porous materials upon impact. Laboratory experiments with detailed material properties will be useful as a database that can serve as a reference for numerical modeling and theoretical scaling considerations.  相似文献   

Retardation capacity of altered granitic rock distributed along fractured and faulted zones in the orogenic belt of Japan     

H. Yoshida  R. Metcalfe  Y. Seida  H. Takahashi  T. Kikuchi 《Engineering Geology》2009,106(3-4):116-122

There are wide areas of granitic rocks in the Japanese orogenic belt. These granitic bodies inevitably contain fracture and fault systems associated with alteration zones. However, relatively little attention has been given to the possible influence of such widely distributed alteration zones on the migration of radionuclides from any radioactive waste repository that might in future be sited within granitic rock. In particular, the influences of alteration products and micro-fractures, due to chemical sorption and/or physical retardation require further consideration. In order to understand the retardation capacity of the altered deep granitic rocks, detailed geometrical characterization of pores, geochemical analysis, and batch sorption and flow-through experiments have been carried out. Those results show that the altered granite has a large volume of accessible pores, particularly in potassium-feldspar grains, which would influence nuclide retardation more than the accessible porosity in other minerals present, such as biotite. The distribution coefficients, Kd estimated from batch sorption tests and flow-through experiments suggest that altered granite has a high capability to retard the migration of nuclides. The retardation would probably be due to sorption on altered minerals such as sericite and iron hydroxides formed along grain boundaries and in pores created by dissolution, in addition to sorption on primary sorptive minerals. These results provide confidence that even altered and fractured parts of any granitic rock that might be encountered in a site for the disposal of high level radioactive waste may still retard radionuclide migration and thereby help the geosphere to function as a barrier.  相似文献   

断裂熔融作用中单质铁的形成及其指示的孕震环境     

张蕾  李海兵  孙知明  曹勇  王焕 《岩石学报》2019,35(6):1875-1891

目前缺乏来自于地震断裂带的假玄武玻璃的原始特征研究,制约着我们对地震孕震环境和地震发生机制的认识。本文以龙门山断裂带汶川科钻2号钻孔岩心的碎裂岩及花岗闪长岩为研究对象,通过氩气环境下的高温加热实验(最高温度达1750℃)、显微结构观察、地球化学分析和岩石磁学测试,探讨断裂熔融作用中单质铁的形成及其指示意义。花岗闪长岩和碎裂岩在1100℃时发生部分熔融作用,形成了非晶质和微晶;在≥1300℃时形成了大量单质铁组成的微球粒,可能是含铁矿物发生了以碳物质为还原剂的高温还原反应。高温实验后样品的磁化率值高于碎裂岩的磁化率值,新生成的磁铁矿是≤1100℃的样品高磁化率值的主要原因;熔融作用中形成的单质铁和少量的磁铁矿是≥1300℃样品高磁化率值的重要原因。结合前人对于快速摩擦实验熔体、地幔物质及陨石的研究,我们认为粘土矿物、硅酸盐矿物含量较多的断层泥在同震滑移中因热增压机制很难形成单质铁;而花岗岩、安山岩、辉长岩、闪长岩等岩浆岩和糜棱岩在流体作用弱和硫化物含量低的环境中易在大地震中形成单质铁。龙门山断裂带的假玄武玻璃的熔融温度≥1300℃,硫元素含量较低并发现有过剩铁元素。因此,表明龙门山断裂带的假玄武玻璃中可能形成了单质铁,其和磁铁矿是假玄武玻璃高磁化率值异常的重要原因,并指示了深部流体作用弱、硫化物含量低、还原性的孕震环境。  相似文献   

Effects of the low-frequency zonal wind variation on the high frequency atmospheric variability over the tropics     

K. P. Sooraj  Daehyun Kim  Jong-Seong Kug  Sang-Wook Yeh  Fei-Fei Jin  In-Sik Kang 《Climate Dynamics》2009,33(4):495-507

Recently, there is increasing evidence on the interaction of atmospheric high-frequency (HF) variability with climatic low-frequency (LF) variability. In this study, we examine this relationship of HF variability with large scale circulation using idealized experiments with an aqua-planet Atmospheric GCM (with zonally uniform SST), run in different zonal momentum forcing scenarios. The effect of large scale circulation changes to the HF variability is demonstrated here. The HF atmospheric variability is enhanced over the westerly forced region, through easterly vertical shear. Our study also manifests that apart from the vertical wind shear, strong low-level convergence and horizontal zonal wind shear are also important for enhancing the HF variance. This is clearly seen in the eastern part of the forcing, where the HF activity shows relatively maximum increase, in spite of similar vertical shear over the forced regions. The possible implications for multi-scale interaction (e.g. MJO–ENSO interaction) are also discussed.  相似文献