Dust ejection from planetary bodies by temperature gradients: Laboratory experiments     

Thorben Kelling  Gerhard Wurm  Miroslav Kocifaj  Jozef Klačka  Dennis Reiss 《Icarus》2011,212(2):935-940

Laboratory experiments show that dusty bodies in a gaseous environment eject dust particles if they are illuminated. We find that even more intense dust eruptions occur when the light source is turned off. We attribute this to a compression of gas by thermal creep in response to the changing temperature gradients in the top dust layers. The effect is studied at a light flux of 13 kW/m² and 1 mbar ambient pressure. The effect is applicable to protoplanetary disks and Mars. In the inner part of protoplanetary disks, planetesimals can be eroded especially at the terminator of a rotating body. This leads to the production of dust which can then be transported towards the disk edge or the outer disk regions. The generated dust might constitute a significant fraction of the warm dust observed in extrasolar protoplanetary disks. We estimate erosion rates of about 1 kg s^?1 for 100 m parent bodies. The dust might also contribute to subsequent planetary growth in different locations or on existing protoplanets which are large enough not to be susceptible to particle loss by light induced ejection. Due to the ejections, planetesimals and smaller bodies will be accelerated or decelerated and drift outward or inward, respectively. The effect might also explain the entrainment of dust in dust devils on Mars, especially at high altitudes where gas drag alone might not be sufficient.  相似文献   

高压直流输电对泾县地震台地磁观测干扰分析     

郎孝龄  汪丹丹  严吉  翟义勇 《地震地磁观测与研究》2012,33(Z1)

高压直流输电线路对地磁观测的干扰幅度大,随意性大.泾县地震台地磁观测目前受到附近穿行的多条高压直流输电影响,且无法避免.通过对泾县地震台观测资料分析,就高压直流输电对地磁观测的干扰原理和一些识别的方法有一定认识,并掌握有效剔除方法.  相似文献   

秦直道旅游开发问题探讨   总被引：1，自引：0，他引：1  

张河清  王浪 《地域研究与开发》2008,27(1):59-63

秦直道是古代连接中原地区和北方少数民族地区的一条重要纽带,它是秦帝国传递中央政令和传播中原文化的重要通讯带,也是秦始皇为抵御匈奴、调动兵力和物资的一条战略要道,在历史上起到了极其重要的作用.通过对秦直道及其现阶段旅游资源开发现状的介绍和在对秦直道旅游资源开发的可行性综合评价与分析的基础上,提出秦直道旅游资源开发的初步构想.  相似文献   

吉林省小西南岔金铜矿床地球化学特征     

陈兆仁  胡朗  郑晓惠 《地质与资源》2011,20(3):194-200

小西南岔金铜矿床为浅成金铜共生大型矿床,受岩体-地层-构造联合控制,以叠加富集为主.矿区分为南山和北山两个矿段.矿化主要发育在闪长岩和斜长花岗岩中的北北西向断裂带及岩体接触带中,矿化以含金铜石英硫化物脉型及密集细脉为主.矿区水系沉积物异常元素为Au、Cu、Ag、Bi、Zn、Mo（W、Sb、As）;土壤异常元素为Cu、Mo、Au、Ag、Bi;岩石地球化学异常为Au、Cu、Ag、Bi、Ta、Ba、Sr（As、Sb、Zn、Co、Ni、W、Mo）.原生晕中轴向分带序列为（Bs、Sr）-As-Ag-Pb-Sn-W-Au-Bi-Cu-Sb-CoTe-Ni-Zn-Mo.南山矿段水平分带序列为Au-Cu-Bi-Te-Ag-Pb-Zn-As-Co-Ni-W-Sb-Mo-Sn;北山矿段为Au-Cu-Bi-Te-AgAs-Sb-Mo-Pb-Zn-Co-W-Ni-Sn.矿床地球化学异常特征及其分带性显示北山矿段矿体剥蚀程度大于南山矿段,矿区北西部矿体剥蚀强度大于南东部,表明向矿区南部仍有较大找矿远景.  相似文献   

微压流化式复合生物反应器的同步脱氮     

刘淼  陈睿阳  李广柱  郎贵林 《吉林大学学报(地球科学版)》2012,42(3):832-837

通过对曝气系统的调节,微压流化式复合生物反应器（MP-FHBR）内可以实现好氧区和缺氧区共存,利用这一特点和MP-FHBR中同时存在的活性污泥﹑悬浮生物膜复合生物体系,进行了同步脱氮的试验研究。结果表明,MP-FHBR在好氧-缺氧条件下,实现了同步脱氮过程,TN和COD的平均去除率分别达到77.5%和98.3%。降低DO质量浓度使反应器内形成完全缺氧环境,对MP-FHBR同步脱氮效果没有显著影响,但会降低系统去除COD的效果;而提高DO质量浓度使反应器内形成完全好氧环境,MP-FHBR同步脱氮效果显著下降。在一定范围内提高进水COD/TN有利于提高MP-FHBR同步脱氮效果,COD/TN 由2升高到10,TN平均去除率由58.4%提高到78.8%,而继续提高COD/TN对系统同步脱氮效果的影响并不明显。在反应器允许的条件下,提高污泥质量浓度(MLSS)有利于提高系统反硝化脱氮效果,TN去除率随MLSS的增加而提高。  相似文献   

快速城市化地区水系结构变化特征——以深圳市为例   总被引：12，自引：4，他引：8  

黄奕龙  王仰麟  刘珍环  曾祥坤  陈朗 《地理研究》2008,27(5):1212-1220

为了探讨城市化对水系结构的影响,应用深圳市1982、2002年的二期水系详查图,定量分析了水系长度、密度、分枝比、分枝能力和分维数等参数的变化特征。结果表明: 快速城市化过程中, 深圳市的河道总长度减少、密度减小, 河道数目减少, 特别是低级别的支流减少较多; 河道的分枝比和分枝能力都有不同程度的弱化, 单个水系片区和全市的河流分维数都下降,河流具有简单化的趋势, 河流的多元化特征削弱; 对于不同水系片区来说, 其变化速度不同, 表明城市化过程对水系结构的干扰存在空间差异性。建议强力推进河流的蓝线规划和滨水区的开发管理, 将水网的保护和规划纳入到城市规划的管理范围; 注重在开发利用中的保护, 减少各类新建城市用地、农用地整理过程中对水系的破坏; 加大水土保持力度, 减少因水土流失导致河流淤塞; 加强管理, 严禁向河道中倾倒垃圾。  相似文献   

Impact of loading displacements on SLR-derived parameters and on the consistency between GNSS and SLR results   总被引：5，自引：4，他引：1  

Krzysztof Sośnica  Daniela Thaller  Rolf Dach  Adrian Jäggi  Gerhard Beutler 《Journal of Geodesy》2013,87(8):751-769

Displacements of the Earth’s surface caused by tidal and non-tidal loading forces are relevant in high-precision space geodesy. Some of the corrections are recommended by the international scientific community to be applied at the observation level, e.g., ocean tidal loading (OTL) and atmospheric tidal loading (ATL). Non-tidal displacement corrections are in general recommended not to be applied in the products of the International Earth Rotation and Reference Systems Service, in particular atmospheric non-tidal loading (ANTL), oceanic and hydrological non-tidal corrections. We assess and compare the impact of OTL, ATL and ANTL on SLR-derived parameters by reprocessing 12 years of SLR data considering and ignoring individual corrections. We show that loading displacements have an influence not only on station long-term stability, but also on geocenter coordinates, Earth Rotation Parameters, and satellite orbits. Applying the loading corrections reduces the amplitudes of annual signals in the time series of geocenter and station coordinates. The general improvement of the SLR station 3D coordinate repeatability when applying OTL, ATL and ANTL corrections are 19.5 %, 0.2 % and 3.3 % respectively, w.r.t. the solutions without loading corrections. ANTL corrections play a crucial role in the combination of optical (SLR) and microwave (GNSS, VLBI, DORIS) space geodetic observation techniques, because of the so-called Blue-Sky effect: SLR measurements can be carried out only under cloudless sky conditions—typically during high air pressure conditions, when the Earth’s crust is deformed, whereas microwave observations are weather-independent. Thus, applying the loading corrections at the observation level improves SLR-derived products as well as the consistency with microwave-based results. We assess the Blue-Sky effect on SLR stations and the consistency improvement between GNSS and SLR solutions when ANTL corrections are included. The omission of ANTL corrections may lead to inconsistencies between SLR and GNSS solutions of up to 2.5 mm for inland stations. As a result, the estimated GNSS–SLR coordinate differences correspond better to the local ties at the co-located stations when applying ANTL corrections.  相似文献   

贵州省罗甸透闪石矿床地质特征及找矿预测   总被引：1，自引：0，他引：1  

范二川  兰永文  戴朝辉  王洪雨  李浪 《矿物学报》2012,32(2):304-309

罗甸透闪石矿床属燕山期岩浆热液矿床,成矿作用为接触交代;侵入岩体为辉绿岩,属偏碱性基性幔源浅成岩,岩体呈似层状顺层侵入于二叠系中统栖霞组（P2q）与茅口组（P2m）接触面之间;围岩蚀变有透闪石化和大理岩化,由岩体向外依次分为大理岩化带→透闪石化带;软玉矿体赋存于外接触带茅口组一侧,顺层产出;含矿带厚10～30余米,其中夹矿体十余层,矿体形态以似层状为主,次为透镜状,厚0.05～0.3 m。在1000 km2范围内发现5个辉绿岩体露头,呈带状出露,长3～35 km,显示有矿化,具有较好的找矿远景。  相似文献   

松辽盆地深层火山岩储层测井响应及地质解译   总被引：1，自引：0，他引：1  

吴颜雄  王璞珺  边伟华  高有峰  郎元强 《吉林大学学报(地球科学版)》2012,(6):1927-1934,1965

为研究测井信息与地质属性的对应性,利用丰富的岩心描述结果刻度测井资料,对12种常见火山岩常规测井和8种成像测井图像进行地质解译。结果表明,火山岩地质属性的测井响应具有普遍性。常规测井中自然伽马和密度曲线对基、中、酸性火山岩响应明显,电阻率和三孔隙度曲线对火山岩的结构构造及孔缝响应明显。成像测井模式具体为:凝灰结构表现出高阻亮点模式,原生气孔表现出低阻暗点模式,流纹构造表现出中高阻黄白相间的正弦曲线模式,角砾结构表现出高阻亮块和低阻暗点模式,低角度裂缝表现出低阻正弦曲线模式,沉火山角砾结构表现出中低阻黄橙相间正弦曲线模式,火山碎屑溶孔表现出亮块中含暗点模式,块状结构表现出亮块模式。  相似文献   

Mutual validation of GNSS height measurements and high-precision geometric-astronomical leveling     

Christian Hirt  Martin Schmitz  Uwe Feldmann-Westendorff  Gerhard Wübbena  Cord-Hinrich Jahn  Günter Seeber 《GPS Solutions》2011,15(2):149-159

The method of geometric-astronomical leveling is presented as a suited technique for the validation of GNSS (Global Navigation Satellite System) heights. In geometric-astronomical leveling, the ellipsoidal height differences are obtained by combining conventional spirit leveling and astronomical leveling. Astronomical leveling with recently developed digital zenith camera systems is capable of providing the geometry of equipotential surfaces of the gravity field accurate to a few 0.1 mm per km. This is comparable to the accuracy of spirit leveling. Consequently, geometric-astronomical leveling yields accurate ellipsoidal height differences that may serve as an independent check on GNSS height measurements at local scales. A test was performed in a local geodetic network near Hanover. GPS observations were simultaneously carried out at five stations over a time span of 48 h and processed considering state-of-the-art techniques and sophisticated new approaches to reduce station-dependent errors. The comparison of GPS height differences with those from geometric-astronomical leveling shows a promising agreement of some millimeters. The experiment indicates the currently achievable accuracy level of GPS height measurements and demonstrates the practical applicability of the proposed approach for the validation of GNSS height measurements as well as the evaluation of GNSS height processing strategies.  相似文献