Book review     

Richard Barakat  Petr Vanicek  Randall L. Mackie  Jacek A. Majorowicz  Ley Truskinovsky  Andrea Borgia  Steven Carey  Ursula B. Marvin 《Pure and Applied Geophysics》1990,134(3):485-507

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Tunnel stability analysis during construction using a neuro‐fuzzy system     

Jos Luis Rangel  Ursula Iturrarn‐Viveros  A. Gustavo Ayala  Francisco Cervantes 《国际地质力学数值与分析法杂志》2005,29(15):1433-1456

This paper presents an alternative strategy to evaluate the stability of tunnels during the design and construction stages based on a hybrid system, composed by neural, neuro‐fuzzy and analytical solutions. A prototype of this system is designed using a database formed by 261 cases, 45 real and the rest synthetic. This system is capable of reproducing the displacements induced at the periphery of the tunnel before and after support installation. The stability of the excavation process is evaluated using a criterion that considers dimensionless parameters based on the shear strength of the media, the induced deformation level in the ground, the plastic radii and the advance of excavation without support. The efficiency and validity of the prototype is verified with two examples of actual tunnels, one included in the database used to train the system and the other not included. The results of both examples show a better approximation than other commonly used techniques. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

软性海洋沉积物中水含量对XRF测试的影响     

Rik Tjallingii  Ursula R 《海洋地质前沿》2008,24(3):24-26

Avaatech型X荧光扫描仪是由计算机控制的柱状样扫描装置，可以从剖开样品表面直接获得沉积物的化学组成，无需破坏样品的整体性。能够实现几乎连续的测试，快速地得到从Al到u的所有元素的相对含量。XRF扫描仪已经成功地应用于高分辨率、不同时间序列和时间尺度的地层对比以及沉积相和古气候重建。  相似文献   

Domenico Troili (1766): “The true cause of the fall of a stone in Albereto is a subterranean explosion that hurled the stone skyward”     

Ursula B. Marvin  Mario L. Cosmo 《Meteoritics & planetary science》2002,37(12):1857-1864

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AN UNPUBLISHED MEMOIR ON METEORITES BY LYMAN SPALDING, 1810     

Ursula B. Marvin 《Meteoritics & planetary science》1979,14(2):197-205

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Basalts from Mare Crisium     

Graham Ryder  Harry Y. Mcsween Jr.  Ursula B. Marvin 《Earth, Moon, and Planets》1977,17(3):263-287

The stratified core sample returned from Mare Crisium by the Luna 24 unmanned space probe is composed primarily of a new variety of subophitic to ophitic basalt with very low contents of TiO₂ and MgO. This consists of clinopyroxene, calcic plagioclase, olivine, and minor amounts of silica, chromite, ulvöspinel, ilmenite, troilite, apatite, and Fe-metal. Granular metabasalts have the same bulk composition, but mineral phases exhibit less compositional variation. Fine-grained impact melts have similar compositions and are apparently derived from these basalts. We conclude that the basalts, which are chemically distinct from the very-low-titanium basalts found elsewhere on the Moon, represent the local surface flows of Mare Crisium.Sparse fragments of an olivine vitrophyre that is low in TiO₂ but high in MgO and approaches the composition of the Apollo 15 green glasses may be derived from patches of dark mantling materials 20 km from the landing site.Now at Department of Geology, University of California at Davis, Davis, Calif., U.S.A.Now at Department of Geological Sciences, The University of Tennessee, Knoxville, Tenn., U.S.A.  相似文献   

Scattering and diffraction of SH waves by a finite crack: an analytical solution   总被引：1，自引：0，他引：1  

Francisco J. Sánchez&#;Sesma  Ursula Iturrarán&#;Viveros 《Geophysical Journal International》2001,145(3):749-758

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Late and post-glacial history of meromictic Längsee (Austria), in respect to climate change and anthropogenic impact     

Roland Schmidt  Sybille Wunsam  Ursula Brosch  Jan Fott  Andrea Lami  Heinz Löffler  Aldo Marchetto  Harald W. Müller  Miroslava Pražáková  Bernd Schwaighofer 《Aquatic Sciences - Research Across Boundaries》1998,60(1):56-88

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Human impact on Holocene sediment dynamics in the Eastern Mediterranean – the example of the Roman harbour of Ephesus          下载免费PDF全文

Friederike Stock  Maria Knipping  Anna Pint  Sabine Ladstätter  Hugo Delile  Andreas G. Heiss  Hannes Laermanns  Piers D. Mitchell  René Ployer  Martin Steskal  Ursula Thanheiser  Ralf Urz  Volker Wennrich  Helmut Brückner 《地球表面变化过程与地形》2016,41(7):980-996

During the past millennia, many erosion and accumulation processes have been modified by anthropogenic impact. This holds especially true for the environs of ancient settlements and their harbours along the Mediterranean coasts. Our multi‐proxy investigations in the Roman harbour and the harbour canal of Ephesus (western Turkey) reveals that humans have significantly triggered soil erosion during the last three millennia. Since the eighth century bc , and especially since the Hellenistic period, a high sedimentation rate indicates fast alluviation and delta progradation of the Küçük Menderes. Deforestation, agriculture (especially ploughing) and grazing (especially goats) were the main reasons for erosion of the river catchment area. One consequence was significant siltation of the Hellenistic/Roman harbour basin. This sediment trap archives the human impact, which was strongly enhanced from Hellenistic/Roman to Byzantine times (second/first centuries bc to the sixth/seventh centuries ad ), evidenced by high sedimentation rates, raised values of heavy metal contaminations [lead (Pb), copper (Cu)], the occurrence of fruit tree pollen and of intestinal parasites. From the middle to the end of the first millennium ad , the influence of Ephesus declined, which resulted in a decrease of human impact. Studies of several ancient settlements around the Mediterranean Sea tell a comparable story. They also confirm that during their most flourishing periods the human impact totally overprinted the climatic one. To detect the latter, geo‐bio‐archives of relatively pristine areas have to be investigated in detail. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Total body burden and tissue distribution of polyfluorinated compounds in harbor seals (Phoca vitulina) from the German Bight   总被引：1，自引：0，他引：1  

Lutz Ahrens  Ursula Siebert 《Marine pollution bulletin》2009,58(4):520-525

Total body burden and tissue distribution of polyfluorinated compounds (PFCs) were investigated in harbor seals (Phoca vitulina) from the German Bight in 2007. A total number of 18 individual PFCs from the following groups could be quantified in the different tissues: perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonates (PFSAs) and their precursors perfluorinated sulfinates (PFSiAs), perfluorinated sulfonamides, and sulfonamido ethanols. Perfluorooctanesulfonate (PFOS) was the predominant compound in all measured seal tissues (up to 1665 ng g⁻¹ wet weight in liver tissue). The dominant PFCAs were perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA), but their concentrations were much lower compared to PFOS. The mean whole body burden in harbor seals of all detected PFCs was estimated to be 2665 ± 1207 μg absolute. The major amount of the total PFCs burden in the bodies was in blood (38%) and liver (36%), followed by muscle (13%), lung (8%), kidney (2%), blubber (2%), heart (1%), brain (1%), thymus (<0.01%) and thyroid (<0.01%). These data suggest large differences in body burden and accumulation pattern of PFCs in marine mammals.  相似文献