Vertical profiles of aeolian sand mass flux   总被引：5，自引：0，他引：5  

J. R. Ni  Z. S. Li  C. Mendoza 《Geomorphology》2003,49(3-4):205-218

Vertical profiles of the horizontal mass flux of blown sand are investigated experimentally using a passive vertical array in a wind tunnel. Considering lower sampling efficiency of the sand trap in the near-bed region, this investigation is complemented by the measurements of the longitudinal profiles of mass flux made using a horizontal sand trap. The experiments were conducted with two test sands and five different stream velocities.In the upper part of the vertical profile, the measured data exhibit an exponential decay distribution with a positive deviation occurring in the near-bed region. The measured longitudinal profiles are similar to the measured vertical profiles. Linking both profiles and the modes of sand transport, it is possible that saltating sand grains give rise to the well-known exponential decay distribution of mass flux, and that creeping and reptating grains force a deviation from it. A simple equation applicable for both the vertical and the longitudinal sand mass flux variations is introduced and the parameters are estimated from experimental data.  相似文献   

Photometric study of five open star clusters     

《New Astronomy》2014

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南黄海冷水团海域溶解氧和叶绿素最大现象值及营养盐累积的季节演变   总被引：7，自引：0，他引：7  

韦钦胜  傅明珠  李艳  王保栋  于志刚 《海洋学报》2013,35(4):142-154

基于2006-2007年在南黄海冷水团海域开展的4个季度月的调查资料, 重点研究了该海域溶解氧(DO)、叶绿素a(Chl a)最大值现象和营养盐累积的季节演变规律。结果表明:春至秋季黄海冷水团海域DO和Chl a最大值层深度具有先加深后变浅的趋势, 出现最大值层的海域面积呈现出先增大后缩小的变化过程, DO和Chl a最大值层的深度及面积在夏季均达到最大, 至冬季DO和Chl a最大值现象消失;夏季冷水团海域深水区DO最大值处的氧含量整体高于春季, 而冷水团边界附近氧最大值处的氧含量整体低于春季;春至秋季冷水域深水区次表层Chl a最大值处的Chl a含量先降低后升高, 于夏季时最低, 入秋后开始升高, 而一年四季中冷水域边界附近Chl a最大值处的Chl a含量却在夏季时最高, 而且显著高于深水区。黄海冷水团海域的底层营养盐储库具有一定的空间异质性, 冷水域底层通常分别在深水区和西部边界处存在营养盐高值核心, 其中位于深水区的高值核心位置季节变化不明显, 而位于冷水域西部边界附近的高值核心位置则呈现出自春季至夏季向西移动、入秋后又向东部移动的季节变化特征。水文物理因素和生物化学过程对DO、Chl a最大值及营养盐储库的季节演变具有重要的调控作用。  相似文献   

黄海西部沿岸冷水在夏季南黄海西部底层冷水形成和季节演变过程中作用的化学水文学分析     

韦钦胜  于志刚  葛人峰  王辉武  王保栋 《海洋与湖沼》2013,44(4):890-905

以金枪鱼碎肉为原料, 采用双酶分步水解法制备高F值酶解液, 通过Box-Behnken试验设计, 分别确定两步酶解的最佳条件, 酶解液经活性炭静态吸附去除游离芳香族氨基酸, 对脱芳后的酶解液进行氨基酸组成分析并测定F值。结果表明, 胃蛋白酶为第一步水解用酶, 酶解的最佳工艺条件为酶用量650U/g, 料水比1∶7(g/mL), 温度35.9℃; 风味蛋白酶为第二步水解用酶, 酶解的最佳工艺条件为酶用量50700U/g, pH 6.51, 温度51℃, 最终水解度达到36.87%±0.54%; 酶解液在pH 3.0, 温度35℃条件下, 经5%(质量体积分数)的活性炭吸附时间3h后, 脱芳率达到63.18%, F值为30.33, 符合高F值肽的要求。  相似文献   

Mass movements,geotechnical properties,and slope stability in the outer shelf—Upper slope,northwestern Aegean sea     

Vasilios Lykousis  George Chronis 《Marine Georesources & Geotechnology》2013,31(3):231-247

Abstract

Subbottom profiling (3.5 kHz) in the uppermost slope of the outer shelf of the northwestern Aegean Sea has shown downslope slumping and intense sediment deformation as well as a succession of microslumping within the Late Pleistocene delta sequences. Postdeposition bottom erosion by currents and the overconsolidated sediments (Cu/Po > 1) indicate the termination of deformations a long time ago. Deformation processes are estimated to have been active 18,000–10,000 B.P. Large‐scale active downslope deformations with clockwise sediment block rotation have affected the area as well. These longer‐period deformations are associated with regional neotectonics and older unconformities (i. e., Plio‐Pleistocene) as potential slide planes.

Geotechnical properties reflect mainly textural variations and locally (within sapropelic layers) high organic matter content. Relatively high values of shear strength were measured (5–29 kPa) with intermediate sensitivities (2–5), whereas relatively low values of water content (33–81%) were found along the five selective sediment cores.

Infinity slope stability analysis revealed that the slopes in the study area are most stable, although theoretical evaluations (Cu estimated from linear regression analysis) indicate relative instability for the potential glide plane at 20 m depth. The outer shelf is covered by compact relict sands, and their gentle and low‐angle (<0.2°) slopes are the most stable region of the investigated area.  相似文献   

一个压力坐标海洋环流模式(PCOM1.0)的基本模拟性能评估     

欧念森  林一骅  毕训强  张宇 《气候与环境研究》2016,21(1):56-64

参照Griffies et al.(2009)提出的海洋—海冰耦合模式参考试验(Coordinated Ocean-ice Reference Experiments,COREs),设计了一个800年积分的数值试验,对一个质量严格守恒的压力坐标海洋环流模式(Pressure Coordinate Ocean Model,PCOM1.0)的基本模拟性能进行了评估,并与观测资料和再分析资料进行了对比。结果表明,PCOM1.0模拟的温盐场和基本流场与COREs模式的模拟水平基本接近。其中,模拟的大西洋经向翻转流在45°N附近达到18 Sv(1 Sv=106 m3 s-1),与观测估计值接近;对海表面温度的模拟误差主要集中在北太平洋黑潮区和北大西洋湾流区等中高纬度急流区;模拟的热带太平洋温跃层过于深厚;模拟的经德雷克海峡的体积输送达130 Sv,比大部分COREs模式及再分析资料都更接近于观测估计值。  相似文献   

青藏高原及附近区域穿越对流层顶的质量和臭氧通量研究   总被引：2，自引：1，他引：1       下载免费PDF全文

王卫国  梁俊平  王颢樾  樊雯璇 《高原气象》2010,29(3):554-562

利用等熵坐标下的Wei公式对青藏高原及附近地区穿越动力学和热力学定义下对流层顶的质量和臭氧通量的时空分布变化进行了计算分析。结果表明,采用这两种定义下的对流层顶时,穿越对流层顶的质量和臭氧通量都表现出在热带纬度带为TST通量,到了副热带则转换为STT通量。由于热力学定义下的对流层顶位置稍高,造成了穿越热力学对流层顶的质量和臭氧通量变化幅度大于动力学对流层顶的情况。另外,还发现在所研究的区域穿越对流层顶质量和臭氧通量交换具有明显的年代际变化特征,在1958—2001年时段内交换是先减弱后增强。青藏高原南部及南侧地区向上的质量和臭氧输送经历了逐渐减弱过程,青藏高原北部地区向下的质量和臭氧通量交换也表现为逐渐减弱的过程,这些区域作为通量输送的通道作用是在减弱的。而接近青藏高原西北侧的塔里木盆地附近的向上输送则是逐渐加强的,表明这一区域交换通道作用在青藏高原及附近地区的质量和臭氧交换过程中起着越来越重要的作用。  相似文献   

Large calcite and bulk-rock volume loss in metacarbonate xenoliths from the Quérigut massif (French Pyrenees)     

Cyril Durand  Didier Marquer  Lukas Baumgartner  Philippe Goncalves  Philippe Boulvais  Michel Rossy 《Contributions to Mineralogy and Petrology》2009,157(6):749-763

Chemical mass transfer was quantified in a metacarbonate xenolith enclosed within the granodiorite of the Quérigut massif (Pyrenees, France). Mass balance calculations suggest a strong decrease of CaO, SrO and CO₂ contents (up to −90%), correlated with a decrease of modal calcite content as the contact is approached. Most other chemical elements behave immobile during metasomatism. They are therefore passively enriched. Only a small increase of SiO₂, Al₂O₃ and Fe₂O₃ contents occurs in the immediate vicinity of the contact. Hence, in this study, skarn formation is characterized by the lack of large chemical element influx from the granitoid protolith. A large decrease of the initial carbonate volume (up to −86%) resulted from a combination of decarbonation reactions and loss of CaO and CO₂. The resulting volume change has potentially important consequences for the interpretation of stable isotope profiles: the isotope alteration could have occured over greater distances than those observed today.  相似文献   

Geological and geotechnical investigations of Loharinag-Pala Hydroelectric Project,Garhwal Himalaya,Uttarakhand   总被引：1，自引：0，他引：1  

Ajay K. Naithani  A. K. Bhatt  K. S. Krishna Murthy 《Journal of the Geological Society of India》2009,73(6):821-836

The project area, forming a part of Bhagirathi valley, exposed rocks classed as central Himalayan crystallines and are medium to high grade metamorphics. The rock types exposed are feldspathic gneisses, quartz-biotite schists, garnet-biotite schist, biotite gneisses, migmatites and amphibolites. To design the rock support for the underground structures of desilting chambers, HRT, surge shaft, pressure shafts, power house, TRT and for the foundations of barrage and intake of desilting chambers, rock mass classifications was attempted following the methods of Bieniawski Rock Mass Rating (RMR) Classification and Tunnelling Quality Index (Q) of Barton et al. RMR technique involves collection of data on rock strength, RQD (%), spacing of discontinuities, condition of discontinuities and groundwater condition, while the ‘Q’ involves collection of data on RQD (%), joint set numbers (Jn), joint roughness number (Jr), joint alternation number (Ja), joint water reduction factor (Jw) and stress reduction factors (SRF). The permeability test in the overburden was done by the constant head method, while in the bed rock portion conducted by packer test. The result indicates that the rock masses of the area fall under the good, fair and poor rock quality. Augen gneiss of power house area is coming under the category of moderately strong rock as proved by deformability characteristics and strength parameter. On the basis of above study recommendations have been made for the proper and safe construction of the project components.  相似文献   

In situ radiometric dating on Mars: Investigation of the feasibility of K-Ar dating using flight-type mass and X-ray spectrometers     

D.L. Talboys  S. Barber  S.P. Kelley  A.B. Verchovsky  A. Fazel  C.T. Pillinger  I.P. Wright 《Planetary and Space Science》2009,57(11):1237-1245

The absolute chronology of Mars is poorly known and, as a consequence, a key science aim is to perform accurate radiometric dating of martian geological materials. The scientific benefits of in situ radiometric dating are significant and arguably of most importance is the calibration of the martian cratering rate, similar to what has been achieved for the Moon, to reduce the large uncertainties on absolute boundary ages of martian epochs. The Beagle 2 Mars lander was capable of performing radiometric date measurements of rocks using the analyses from two instruments in its payload: (i) the X-ray Spectrometer (XRS) and (ii) the Gas Analysis Package (GAP). We have investigated the feasibility of in situ radiometric dating using the K-Ar technique employing flight-like versions of Beagle 2 instrumentation. The K-Ar ages of six terrestrial basalts were measured and compared to the ‘control’ Ar-Ar radiometric ages in the range 171-1141 Ma. The K content of each basalt was measured by the flight spare XRS and the ⁴⁰Ar content using a laboratory analogue of the GAP. The K-Ar ages of five basalts broadly agreed with their corresponding Ar-Ar ages. For one final basalt, the ⁴⁰Ar content was below the detection limit and so an age could not be derived. The precision of the K-Ar ages was ∼30% on average. The conclusions from this study are that careful attention must be paid to improving the analytical performance of the instruments, in particular the accuracy and detection limits. The accuracy of the K and Ar measurements are the biggest source of uncertainty in the derived K-Ar age. Having investigated the technique using flight-type planetary instrumentation, we conclude that come of the principle challenges of conducting accurate in situ radiometric dating on Mars using instruments of these types include determining the sample mass, ensuring all the argon is liberated from the sample given the maximum achievable temperature of the mass spectrometer ovens, and argon loss and non-radiogenic argon in the analysed samples.  相似文献