Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility   总被引：1，自引：0，他引：1  

D. M. Wright  J. A. Davies  T. R. Robinson  P. J. Chapman  T. K. Yeoman  E. C. Thomas  M. Lester  S. W. H. Cowley  A. J. Stocker  R. B. Horne  F. Honary 《Annales Geophysicae》2000,18(9):1248-1255

SPEAR is a new polar cap HF radar facility which is to be deployed on Svalbard. The principal capabilities of SPEAR will include the generation of artificial plasma irregularities, operation as an all-sky HF radar, the excitation of ULF waves, and remote sounding of the magnetosphere. Operation of SPEAR in conjunction with the multitude of other instruments on Svalbard, including the EISCAT Svalbard radar, and the overlap of its extensive field-of-view with that of several of the HF radars in the SuperDARN network, will enable in-depth diagnosis of many geophysical and plasma phenomena associated with the cusp region and the substorm expansion phase. Moreover, its ability to produce artificial radar aurora will provide a means for the other instruments to undertake polar cap plasma physics experiments in a controlled manner. Another potential use of the facility is in field-line tagging experiments, for coordinated ground-satellite experiments. Here the scientific objectives of SPEAR are detailed, along with the proposed technical specifications of the system.  相似文献   

龙游灵山多金属黄铁矿选矿研究与开发利用分析     

燕庭富 《浙江国土资源》1994,(2)

本文从选矿试验的结果出发，总结矿石的选矿规律，剖析产生的地质资源原因，并在此基础上提出灵山矿区分步建设，即先形成采矿能力，后建选矿厂。  相似文献   

氧化条件对样品有机碳同位素测定的影响因素讨论   总被引：1，自引：2，他引：1  

曹蕴宁  刘卫国  宁有丰  张庆乐  王政 《地球学报》2005,26(Z1):55-56

有机碳同位素在全球变化、古气候和古环境恢复研究中的应用日益广泛和深人。有机碳同位素分析的基本原理是在高温下过量的氧气中将样品有机物氧化为CO2，通过分离纯化得到纯净的CO2气体送人质谱测定其护δ13C值。 在已发表文章中，对于有机碳同位素的研究，人们所采用的氧化温度和氧化时间都有很大差异，但很少系统地研究有机碳同位素分析氧化条件对样品有机碳同位素测定结果的影响。为了解不同的氧化条件是否会造成样品的有机碳同位素分馏，以及不同氧化条件对样品有机碳同位素测定结果的影响程度，笔者采用封管法，选取了不同类型的样品（有机碳标准、植物、表土、黄土以及红粘土等），采用不同的氧化温度：500℃,550℃,650℃,750℃,850℃,900℃以及950℃等，恒温2.5 h,然后炉冷至室温。 实验结果表明：氧化温度为850℃，恒温时间为2.5 h，对于有机碳标准、植物、表土和较年轻的黄土样品，足以确保样品有机质氧化充分，δ13C值达到稳定，不会产生同位素分馏。 但对于深层黄土和红粘土样品，氧化温度为850℃，恒温时间为2.5 h，其δ13C值不能达到一个稳定值，仍有偏正趋势。这可能是由于深层样品成岩化作用强，样品中含有一些含碳的矿物包裹体，随温度上升到一定程度，才逐渐分解，释放出气体。对于深层黄土和红粘土样品，采用850℃甚至更高的氧化温度其δ13C值仍未达到稳定，合适的氧化温度需进一步的研究来确定。  相似文献   

Phase Relations and Stability of Magnetoplumbite- and Crichtonite-Series Phases under Upper-Mantle P-T Conditions: an Experimental Study to 15 GPa with Implications for LILE Metasomatism in the Lithospheric Mantle     

KONZETT  JURGEN; YANG  HEXIONG; FROST  DANIEL J. 《Journal of Petrology》2005,46(4):749-781

High-pressure–high-temperature experiments were performedin the range 7–15 GPa and 1300–1600°C to investigatethe stability and phase relations of the K- and Ba-dominantmembers of the crichtonite and magnetoplumbite series of phasesin simplified bulk compositions in the systems TiO₂–ZrO₂–Cr₂O₃–Fe₂O₃–BaO–K₂Oand TiO₂–Cr₂O₃–Fe₂O₃–BaO–K₂O. Both seriesof phases occur as inclusions in diamond and/or as constituentsof metasomatized peridotite mantle xenoliths sampled by kimberlitesor alkaline lamprophyres. They can accommodate large ion lithophileelements (LILE) and high field strength elements (HFSE) on awt % level and, hence, can critically influence the LILE andHFSE budget of a metasomatized peridotite even if present onlyin trace amounts. The Ba and K end-members of the crichtoniteseries, lindsleyite and mathiasite, are stable to 11 GPa and1500–1600°C. Between 11 and 12 GPa, lindsleyite breaksdown to form two Ba–Cr-titanates of unknown structurethat persist to at least 13 GPa. The high-pressure breakdownproduct of mathiasite is a K–Cr-titanate with an idealizedformula KM₇O₁₂, where M = Ti, Cr, Mg, Fe. This phase possessesspace group P6₃/m with a = 9·175(2) Å, c = 2·879(1)Å, V = 209·9(1) ų. Towards high temperatures,lindsleyite persists to 1600°C, whereas mathiasite breaksdown between 1500 and 1600°C to form a number of complexTi–Cr-oxides. Ba and K end-members of the magnetoplumbiteseries, hawthorneite and yimengite, are stable in runs at 7,10 and 15 GPa between 1300 and 1400°C coexisting with anumber of Ti–Cr-oxides. Molar mixtures (1:1) of lindsleyite–mathiasiteand hawthorneite–yimengite were studied at 7–10GPa and 1300–1400°C, and 9–15 GPa and 1150–1400°C,respectively. In the system lindsleyite–mathiasite, onehomogeneous Ba–K phase is stable, which shows a systematicincrease in the K/(K + Ba) ratio with increasing pressure. Inthe system hawthorneite–yimengite, two coexisting Ba–Kphases appear, which are Ba rich and Ba poor, respectively.The data obtained from this study suggest that Ba- and K-dominantmembers of the crichtonite and magnetoplumbite series of phasesare potentially stable not only throughout the entire subcontinentallithosphere but also under conditions of an average present-daymantle adiabat in the underlying asthenosphere to a depth ofup to 450 km. At still higher pressures, both K and Ba may remainstored in alkali titanates that would also be eminently suitablefor the transport of other ions with large ionic radii. KEY WORDS: crichtonite; magnetoplumbite; high-P–T experiments; phase relations; upper mantle  相似文献   

Bedload path length and point bar development in gravel-bed river models     

RICHARD S. PYRCE  PETER E. ASHMORE 《Sedimentology》2005,52(4):839-857

Low-sinuosity meandering gravel-bed flume experiments were employed to investigate spatial patterns of deposition, which point to patterns of channel development related to the pool and bar morphology. At channel-forming discharges, fluorescent bedload tracers indicate that deposition is typically focused around the point bar apex, downstream of the apex (contributing to downstream bar migration), and at the bar head/riffle surface. Seven flume experimental runs illustrate a sequence of point bar development related to the spatial patterns of tracer deposition, and the related path length distribution. At early stages of bar formation, transport is from the scour zone across the point bar head to the bar apex and bar margin downstream of the apex. As the point bar develops, bedload transport across the bar decreases, as transport along the channel thalweg increases and sediment is deposited along the bar margin. Deposition cells appear to move from downstream to upstream of the bar apex as this sequence of bar formation progresses. At low (non-channel-forming) discharges, transport occurs to the bar head/riffle surface with very little material being transported to the apex region or point bar interior. The implication is that there is an inherent connection between the loci of particle deposition and point bar formation, largely controlled by the morphology of the channel.  相似文献   

森林下垫面陆面物理过程及局地气候效应的数值模拟试验   总被引：5，自引：0，他引：5  

刘树华  邓毅  胡非  梁福明  刘和平  王建华 《气象学报》2005,63(1):1-12

文中基于大气边界层和植被冠层微气象学基本原理 ,建立了一个森林植被效应的陆面物理过程和二维大气边界层数值模式。并应用该模式进行了植被和土壤含水量等生物和生理过程在陆面过程和局地气候效应方面的数值模拟试验。所得数值模拟试验结果与实际情况相吻合。结果表明 ,应用该模式可获得植被温度、植被冠层内空气温度、地表温度日变化特征 ;森林下垫面大气边界层风速、位温、比湿、湍流交换系数的时空分布和日变化特征。该模式还可应用于不同下垫面 ,模拟陆面物理过程与大气边界层相互作用机制及其局地气候效应的研究 ,这将为气候模式与生物圈的耦合研究奠定一个良好的基础。  相似文献   

100MPa压力下温度和水对干酪根结构状态影响的实验研究   总被引：1，自引：0，他引：1  

曾贻善  吴朝东 《岩石学报》2005,21(1):245-250

为了实验验证变质沉积物中的碳质物拉曼光谱地质温度计的可用性,利用冷封口式高温高压水热系统将焊封金管内的干酪根于100MPa压力和温度(250-700℃)、有水和无水条件下处理24小时,激光拉曼探针(LRM)分析表明,实验所得碳质物的一级和二级拉曼谱特征(拉曼峰的存在、峰的位置、宽度、高度和面积)随温度系统地变化,所得碳质物的D/O比值随温度升高而减小,但在D/O比-温度关系图上-500℃处有一拐点(极小)。实验条件下处理的干酪根的显微富利叶变换红外谱(micro-FTIR)分析表明,脂族C-H和芳族C-H吸收峰的相对强度在500℃左右急剧变化以及在700℃的实验产物中仍存在含氢的功能团。高温高压条件下,水的存在不利于碳质物的石墨化(有序化)。  相似文献   

Redox state of iron in peralkaline rhyolitic glass/melt: X-ray absorption micro-spectroscopy experiments at high temperature     

N. Métrich  J. Susini  F. Farges  D. Massare  S. Lequien 《Chemical Geology》2006,231(4):350-363

Assessing the ferric-ferrous ratio in magmas prior to eruption remains a challenging task. X-ray absorption near-edge structure (μXANES) spectra were collected at the iron K-edge in water-rich peralkaline silicic melt/glass inclusions trapped in quartz. These experiments were carried out between 800 and 20 °C. The chemical environment of iron was also determined in the naturally quenched samples (glass inclusions and matrix glass) and in the peralkaline rhyolitic reference glasses, with variable [Fe³⁺ / ∑Fe] ratios.In the reference glasses, both the intensity of the pre-peaks (Fe²⁺, Fe³⁺) and site geometry of iron change as the oxidation state increases. Fourfold-coordinated Fe³⁺ prevails in highly oxidised peralkaline silicic glasses, using alkalis for charge balance. The position of the pre-edge centroid of the 1s-3d transition correlates with the Fe³⁺ / ΣFe ratios that allowed calibration of the redox state of iron of our natural samples.At high temperatures, Fe²⁺ dominates in the pre-edge structure of melt inclusions. Upon cooling down to 20 °C, the intensity of the Fe³⁺ peak increases, the centroid position of the pre-edge features shifts by nearly 0.5 eV and the main edge moves slightly towards higher energies. The slower the cooling rate, the higher the ferric iron contribution. Iterative μXANES experiments performed on the same samples show that the process is reversible. However, this apparent oxidation of iron upon cooling is an artefact of changes in Fe coordination. It implies that the [Fe³⁺ / ΣFe] ratio of glassy samples, measured at 20 °C, may be overestimated by a factor > 1.7, and that this ratio cannot be reliably retrieved by probing naturally cooled glass inclusions, and most silicate glasses. High temperature μXANES experiments led first to an assessment of the ferric-ferrous ratio in the water-rich peralkaline melt in pre-eruptive magmatic conditions and second to the determination of the corresponding oxygen fugacity at 740 °C.  相似文献   

On the impossibility of measuring the general relativistic part of the terrestrial acceleration of gravity with superconducting gravimeters     

Lorenzo Iorio 《Geophysical Journal International》2006,167(2):567-569

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GRAPES模式动力框架的长期积分特征   总被引：4，自引：2，他引：4       下载免费PDF全文

胡江林沈学顺  张红亮杨学胜 王盘兴 《应用气象学报》2007,18(3):276-284

通过考虑动量表面拖曳并利用牛顿松弛方法将温度松弛到纬向对称的温度场, 对GRAPES模式的动力框架进行了长期时间积分试验。通过统计分析其积分结果表明:GRAPES模式的动力框架可以模拟出大气环流的基本特征; 随着分辨率的提高, GRAPES模式动力框架的模拟结果显示出收敛的特性; 虽然GRAPES模式动力框架采用的是能量不守衡的半隐式半拉格朗日时间积分方案, 但长期时间积分试验表明其能量基本保持稳定。这些结果显示使用GRAPES模式动力框架作大气环流和气候研究的大气动力框架是可行的, 同时也为进一步改进GRAPES模式动力框架提供了线索和依据。  相似文献