Plasma Jet Experiments Using LULI 2000 Laser Facility     

B. Loupias  E. Falize  M. Koenig  S. Bouquet  N. Ozaki  A. Benuzzi-Mounaix  C. Michaut  M. Rabec le Goahec  W. Nazarov  C. Courtois  Y. Aglitskiy  A. YA. Faenov  T. Pikuz 《Astrophysics and Space Science》2007,307(1-3):103-107

We present experiments performed with the LULI2000 nanosecond laser facility. We generated plasma jets by using specific designed target. The main measured quantities related to the jet such as its propagation velocity, temperature and emissive radius evolution are presented. We also performed analytical work, which explains the jet evolution in some cases.  相似文献   

Physical modelling of gelifluction and frost creep: Some results of a large-scale laboratory experiment   总被引：1，自引：0，他引：1  

Charles Harris  Michael Gallop  Jean-Pierre Coutard 《地球表面变化过程与地形》1993,18(5):383-398

An experimental slope was constructed in a 5 m × 5 m square refrigerated tank. The slope was formed of four sections, each consisting of regolith (soil) collected from a distinct bedrock lithology. The four lithologies utilized were granite, limestone, mudstone and slate. The slope was subjected to freezing and thawing from the surface downwards. Water was supplied at the base of the soil during freezing. Frost heaving and surface downslope soil movement were determined after each of 15 freezing cycles, and the profiles of soil movement with depth for each soil type were measured at the end of the 15th cycle. The experimental soils were non-cohesive; those derived from granite and limestone were respectively sandy and gravelly in texture, while those derived from mudstone and slate were silt-rich. Mass movement in the granite and limestone soils was due mainly to frost creep and was associated with the growth of needle ice. In the mudstone and slate soils, gelifluction was dominant as a result of high moisture contents caused by the melting of segregation ice. Mean per cycle rates of downslope soil transport for the granite, limestone, mudstone and slate soils were 5·8 cm³ cm^?1, 6·9 cm³ cm^?1, 21·2 cm³ cm^?1 and 31·2 cm³ cm^?1 respectively, units referring to the volume of soil passing a unit width of slope per cycle. Mass movement rates were shown to be strongly related to the silt content of the soils.  相似文献   

Mangos shale-associated alluvium     

Jonathan B. Laronne 《地球表面变化过程与地形》1981,6(6):541-552

Inquiry into the dissolution kinetics of naturally occurring geologic materials, rather than individual mineral species, has been relatively neglected. This is especially true of surface processes, the realm of surface water hydrology and geomorphology. This paper focuses attention at a laboratory study of the rate of such complex reactions. Functions defining the dissolution rates of saline (0.1–20 per cent salt content) Mancos Shale-associated alluvium in distilled water follow varying patterns. Dissolution is characterized by an initial (<5 min) high rate constant, by a following phase (20 min-57 h) where rates are reduced drastically, and by a final period of encroachment to equilibrium. Initial dissolution rates increase with increase in salt content and sediment: water ratio. The time necessary to approach equilibrium is, however, found to be directly proportional to the sediment; water ratio. The concentration of Na⁺, Mg²⁺, Ca²⁺, SC^2?₄ and HCO^?₃, and the relative abundance of Ca²⁺ and HCO^?₃ increase continuously with contact time, indicating that the hydrated sodium and magnesium sulphate minerals provide most of the initial solutes, though not necessarily most of the total solute bulk. The results obtained in this study indicate that the high initial dissolution rate of soluble minerals from alluvium, and particularly from shales in contact with aqueous solutions, is too short-lived to account for most of the solutes occurring in heavily sediment-laden surface flow. Excluding input from slower, usually supersaturated subsurface flow, dissolution from sediment in transport should be a major source of solutes in originally undersaturated and kinetically unequilibrated surface water in semiarid and arid regions.  相似文献   

Coincidence of cadmium and antibiotic resistance in New York Bight apex benthic microorganisms     

M.A Devanas  C.D Litchfield  C McClean  J Gianni 《Marine pollution bulletin》1980,11(9):264-269

Microorganisms resistant to 1–500 ppm cadmium were isolated over an 11 month period from sediments at the sewage sludge, dredge spoils and industrial acid waste disposal sites, as well as at an estuarine outflow to the New York Bight apex. Tests for antibiotic resistance in these isolates revealed that 94% of the isolates were resistant to one or more antibiotics and that 91% of the original isolates could be characterized by multiple drug resistance. Different selective pressures may account for the various genera and antimicrobial resistance patterns observed. The possibility of extrachromosomal linkage of cadmium and streptomycin resistance is discussed.  相似文献   

Resistance to flow in rough supercritical sheet flow     

Jan Savat 《地球表面变化过程与地形》1980,5(2):103-122

Shallow water depths on steep slopes of as much as fifty per cent can be measured easily by weighing a light flume and the water it contains. Because water accelerates along the flume, a good approximation of the steady state depth is obtained when the recording balance is fixed to its bottom end. From the unit discharge and the depth, and not from measurements of the surface velocity, the Darcy-Weisbach friction coefficient can be calculated. The present results show that this friction coefficient is larger in thin sheet flows than that calculated from the equation for rough turbulent flow. This latter could fit at a Reynolds Number of 50,000. When the regime is laminar (Re < 2,440) the Darcy-Weisbach friction coefficient always exceeds the theoretical value of 96/Re. The great relative depth of standing and travelling waves could account for this discrepancy together with turbulence and wake formation around bottom grains. Herein it is assumed that a regime can prevail where a laminar superlayer glides over a turbulent sublayer in the vicinity of bottom grains, because the ratio of the surface velocity to the mean velocity can greatly exceed 1.5, especially on steep slopes. Until photographs of the streamlines are taken, no statement about flow regimes in supercritical sheet flow can be made.  相似文献   

Laboratory modelling of gravel braided stream morphology     

Peter E. Ashmore 《地球表面变化过程与地形》1982,7(3):201-225

Hydraulic modelling principles, together with a knowledge of channel pattern thresholds, allow the development of a small scale model of a gravel braided stream with flow characteristics and equivalent dimensions of a natural river. The forms and processes of natural gravel braided rivers are reproduced by imposing a constant flume discharge and slope, and maintaining approximate equilibrium with an adjustable sediment feed. Beginning from a straight trough, braiding is initiated by development of a series of alternating bars and scour pools which produce bends of increasing amplitude, leading finally to channel division. These lobate bars accrete downstream by deposition of bed material at their margins, often in the form of avalanche faces. Together with the scour pools with which they are necessarily closely associated, these bars are the fundamental elements of the channel pattern. Channel migration and division is a response to the development of bars, and these adjustments leave portions of the originally active bars in the form of exposed and eroded remnants. Complex flats built from these lobate forms show varying degrees of preservation of the original depositional units, but the model allows observation of the systematic construction of some flats. Sorting of sediment on active bars with avalanche faces shows a distinct fining downstream. This may be the result of the accretion of fining upwards avalanche faces along the bar margins rather than a ‘winnowing out’ of fine material. The processes and forms observed in the model appear to be very similar to those occurring in natural gravel braided streams during peak flows.  相似文献   

膨胀土胀缩性评价中有关问题的研究   总被引：3，自引：0，他引：3  

林玉山  凌泽民 《工程地质学报》1998,6(3):264-268

膨胀土吸水膨胀、失水收缩,产生地表变形,进而导致建筑物破坏。本文就现行膨胀土胀缩性指标试验及地基变形量评价计算中有关问题进行了研究,认为以天然含水量为起始含水量测定土样胀缩率是不合适的,建议以缩限为起点进行膨胀试验,以胀限为起点进行收缩试验,采用加荷膨胀量（而非卸荷膨胀量）参加有荷载下的膨胀率计算。膨胀土地基勘察必须结合场地条件分析可能影响土体含水量变化的因素,对同一工程采用几种方法评价,互相对比、参照。  相似文献   

Stability analysis of lateritic waste deposits   总被引：1，自引：0，他引：1  

Kamel Omraci  Vronique Merrien-Soukatchoff  Jean-Paul Tisot  Jack-Pierre PiguetLe Nickel-SLN 《Engineering Geology》2003,68(3-4):189-199

In open-pit mines covered with lateritic soil, the sterile ground is stored in specially prepared sites. The waste area must then be enhanced in order to extend storage capacity.

To better understand the effect of an elevated dump, typical laboratory tests (triaxial and oedometer tests) have been performed on the lateritic material. The waste disposal site has been modeled using both limit equilibrium and finite element methods. Different types of finite element models have been run; they take the variation of Young's modulus with depth into account and simulate the effect of construction over various phases. Modeling results are then compared with in situ measurements.  相似文献   

实验室盐度计校准结果的不确定度分析     

田锐  李扬眉 《海洋技术学报》2006,25(4):122-124

文中分析了实验室盐度计校准不确定度来源项,按不确定度的评定方法,以实例形式分析评定了校准结果的不确定度。  相似文献   

西秦岭金矿化带中土壤与岩石实验室光谱相关性研究     

郭子祺  王志刚 《遥感学报》1999,3(3):220-224

通过西秦岭金矿化带中土壤与岩石实验室光谱的相关性分析与研究。探索该区表层壤覆盖条件下应用遥感信息寻找金矿床。研究表明,土壤与岩石两者光谱之间有很高的正相关性,并且在谱形上亦有相似性,使得利用该地区土壤光谱特征从遥感信息中提取出土壤覆盖层下的岩石光谱特征成为可能,为这种遥感技术找矿方法提供依据。  相似文献