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  • 550  (68)
  • 2020-2022  (68)
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  • 1
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    Beiträge zur Geomathematik (2021)
    Reimer, Berlin
    In:  SUB Göttingen | ZB 45198:15
    Details
    Publication Date: 2021-12-21
    Description: Zur Lösung erdwissenschaftlicher Fragestellungen werden seit etwa einem Jahrzehnt in zunehmendem Umfang mathematische Methoden herangezogen. Eine der Ursachen für diese Entwicklung besteht darin, dass moderne technische Geräte, wie sie auch in den Erdwissenschaften eingesetzt werden, immer größere Datenmengen produzieren, die nach einer rationellen Verarbeitung verlangen. Es ist daher nicht verwunderlich, dass die Mathematische Geologie in Zusammenhang mit der Entwicklung von Groß-Rechenanlagen stark an Bedeutung gewonnen hat. […]
    Description: The use of mathematics in solving geoscientific problems has increased steadily within the last decade. The modernisation of the technical equipment available to geoscientists has resulted in ever-growing amounts of data which then must be analysed. Therefore, it is no wonder that the development of mathematical geology and computers are closely related.[...]
    Description: BURGER, H. : Digitale Blldverarbeitung - Ein wichtiges Hilfsmittel in der geologischen Fernerkundung (5) BÜRSTENBINDER, J. : Einige Ergebnisse eines Methodenvergleichs bei der Berechnung von Erzkörpern (21) LINDENBERG, H.G. & MENSINK, H. : Multivariate Gruppierungsmethoden in phylogenetisch orientierter Paläontologie (am Beispiel von Gastropoden aus dem Stelnhelmer Becken) (30) PENA, J.L. SURFACE II, ein graphisches Computer-System (52) PRISSANG, R. Die Anwendung einer Methode gleitender gewichteter Mittelwerte auf die Vorratsberechnung einer Gangerzlagerstätte (59) SCHOELE, R. : Geostat1st1k - Ein System von Rechenprogrammen zur Theorie der ortsabhängigen Variablen (67) SCHUMANN, Th. : Methoden der Sozialraumanalyse (80) SCHWIETZER, C.-A. : Klassifizierung von Ostracodenschalen mit Hilfe von Fourier-Koeffizienten (88) SHULMAN, M. The geologic applicability of some constitutive equations (94) SKALA, W. : Einige Eigenschaften geschlossener Prozentsysteme (101) WALLBRECHER, E. : Vektorstatistische Methoden zur Ermittlung von Regelungsgraden und zur Beschreibung von Verteilungsformen tektonischer Daten (110)
    Description: research
    Description: DFG, SUB Göttingen
    Keywords: 550 ; Mathematische und Statistische Geologie ; FID-GEO-DE-7
    Language: German
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  • 2
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    Geowissenschaftliche Mitteilungen - GMIT 86 (2021)
    ARGE GMIT, Bonn
    Details
    Publication Date: 2021-12-20
    Description: Die Ausgabe der Geowissenschaftlichen Mitteilungen vom September 2021 enthält die Themenblöcke: GEOfokus: (Die Antarktisforschung der BGR), GEOaktiv (Wirtschaft, Beruf, Forschung und Lehre), GEOlobby (Gesellschaften, Verbände, Institutionen), GEOreport (Geowissenschaftliche Öffentlichkeitsarbeit, Tagungsberichte, Ausstellungen, Exkursionen, Publikationen), GEOszene (Würdigungen, Nachrufe).
    Description: DFG, SUB Göttingen
    Description: journal
    Keywords: 550 ; Wissenschaftsorganisation und -pflege {Geologische Wissenschaften} ; GMIT ; Geowissenschaftliche Mitteilungen ; FID-GEO-DE-7
    Language: German
    Type: map , publishedVersion
    Format: 140
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  • 3
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    Wolfgang Beyer: A Groundwater Scientist from Dresden (2021)
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    Publication Date: 2021-12-07
    Description: Wolfgang Beyer was a groundwater scientist in Dresden, whose work on the permeability of sediments is cited the world over, but who is otherwise little known. This article is to commemorate him on the occasion of his 90th birthday.
    Keywords: 550 ; Wolfgang Bayer ; groundwater scientist ; commemorative paper
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  • 4
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    A seismic monitoring approach to detect and quantify river sediment mobilization by steelhead redd-building activity (2021)
    Details
    Publication Date: 2021-10-28
    Description: The role of spawning salmonids in altering river bed morphology and sediment transport is significant, yet poorly understood. This is due, in large part, to limitations in monitoring the redd-building process in a continuous and spatially extended way. A complementary approach may be provided through the use of a small seismic sensor network analysing the ground motion signals generated by the agitation of sediment during the redd-building process. We successfully tested the viability of this approach by detecting and locating artificially generated redd signals in a reach of the Mashel River, Washington State, USA. We then utilize records of 17 seismic stations, in which we automatically detected seismic events that were subsequently manually checked, yielding a catalogue of 45 potential redd-building events. Such redd-building events typically lasted between 1 and 20 min and consisted of a series of clusters of 50–100 short energetic pulses in the 20–60 Hz frequency range. The majority (〉90%) of these redd-building events occurred within 11 days, predominantly during the early morning and late afternoon. The seismically derived locations of the signals were in agreement with independently mapped redds. Improved network geometry and installation conditions are required for more efficient detection, robust location and improved energetic insights into redd-building processes in larger reaches. The passive and continuous nature of the seismic approach in detecting redds and describing fish behaviour provides a novel tool for fish biologists and fisheries managers, but also for fluvial geomorphologists, interested in quantifying the amount of sediment mobilized by this ecosystem engineer. When complemented with classic approaches, it could allow for a more holistic picture of the kinetics and temporal patterns (at scales from seconds to multiple seasons) of a key phase of salmonid life cycles. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
    Keywords: 550 ; environmental seismology ; ecosystem engineers ; salmonid spawning ; gravel-bed rivers ; biogeomorphology
    Language: English
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  • 5
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    Impact Forecasting to Support Emergency Management of Natural Hazards (2021)
    Details
    Publication Date: 2021-10-27
    Description: Forecasting and early warning systems are important investments to protect lives, properties, and livelihood. While early warning systems are frequently used to predict the magnitude, location, and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services, or financial loss. Complementing early warning systems with impact forecasts has a twofold advantage: It would provide decision makers with richer information to take informed decisions about emergency measures and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multihazard early warning systems. This review discusses the state of the art in impact forecasting for a wide range of natural hazards. We outline the added value of impact-based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.
    Keywords: 550 ; impact forecasting ; natural hazards ; early warning
    Language: English
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  • 6
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    Ptychographic X-ray speckle tracking (2021)
    Details
    Publication Date: 2021-10-14
    Description: A method is presented for the measurement of the phase gradient of a wavefront by tracking the relative motion of speckles in projection holograms as a sample is scanned across the wavefront. By removing the need to obtain an undistorted reference image of the sample, this method is suitable for the metrology of highly divergent wavefields. Such wavefields allow for large magnification factors that, according to current imaging capabilities, will allow for nanoradian angular sensitivity and nanoscale sample projection imaging. Both the reconstruction algorithm and the imaging geometry are nearly identical to that of ptychography, except that the sample is placed downstream of the beam focus and that no coherent propagation is explicitly accounted for. Like other X-ray speckle tracking methods, it is robust to low-coherence X-ray sources, making it suitable for laboratory-based X-ray sources. Likewise, it is robust to errors in the registered sample positions, making it suitable for X-ray free-electron laser facilities, where beam-pointing fluctuations can be problematic for wavefront metrology. A modified form of the speckle tracking approximation is also presented, based on a second-order local expansion of the Fresnel integral. This result extends the validity of the speckle tracking approximation and may be useful for similar approaches in the field.
    Keywords: 550 ; X-ray speckle tracking ; ptychography ; phase retrieval ; wavefront metrology ; in-line projection holography
    Language: English
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  • 7
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    Tomographic reconstruction with a generative adversarial network (2021)
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    Publication Date: 2021-10-14
    Description: This paper presents a deep learning algorithm for tomographic reconstruction (GANrec). The algorithm uses a generative adversarial network (GAN) to solve the inverse of the Radon transform directly. It works for independent sinograms without additional training steps. The GAN has been developed to fit the input sinogram with the model sinogram generated from the predicted reconstruction. Good quality reconstructions can be obtained during the minimization of the fitting errors. The reconstruction is a self-training procedure based on the physics model, instead of on training data. The algorithm showed significant improvements in the reconstruction accuracy, especially for missing-wedge tomography acquired at less than 180° rotational range. It was also validated by reconstructing a missing-wedge X-ray ptychographic tomography (PXCT) data set of a macroporous zeolite particle, for which only 51 projections over 70° could be collected. The GANrec recovered the 3D pore structure with reasonable quality for further analysis. This reconstruction concept can work universally for most of the ill-posed inverse problems if the forward model is well defined, such as phase retrieval of in-line phase-contrast imaging.
    Keywords: 550 ; missing-wedge tomography ; reconstruction algorithms ; generative adversarial network (GAN) ; ptychography
    Language: English
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  • 8
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    Deep Emulators for Differentiation, Forecasting, and Parametrization in Earth Science Simulators (2021)
    Details
    Publication Date: 2021-09-29
    Description: To understand and predict large, complex, and chaotic systems, Earth scientists build simulators from physical laws. Simulators generalize better to new scenarios, require fewer tunable parameters, and are more interpretable than nonphysical deep learning, but procedures for obtaining their derivatives with respect to their inputs are often unavailable. These missing derivatives limit the application of many important tools for forecasting, model tuning, sensitivity analysis, or subgrid‐scale parametrization. Here, we propose to overcome this limitation with deep emulator networks that learn to calculate the missing derivatives. By training directly on simulation data without analyzing source code or equations, this approach supports simulators in any programming language on any hardware without specialized routines for each case. To demonstrate the effectiveness of our approach, we train emulators on complete or partial system states of the chaotic Lorenz‐96 simulator and evaluate the accuracy of their dynamics and derivatives as a function of integration time and training data set size. We further demonstrate that emulator‐derived derivatives enable accurate 4D‐Var data assimilation and closed‐loop training of parametrizations. These results provide a basis for further combining the parsimony and generality of physical models with the power and flexibility of machine learning.
    Description: Plain Language Summary: Many Earth science simulators are implemented as monolithic programs that calculate changes in the state of a system over time. In many cases, using or improving these simulators also requires the derivatives of their outputs with respect to inputs, which describe how future states depend on past states. These derivatives can be difficult or costly to compute. Several recent studies have applied deep learning (DL) to simulation data to construct emulators of their dynamics. Here, we use the fact that DL models can be easily and automatically differentiated to obtain approximate derivatives of the original simulator and test this idea on a simple and common chaotic model of the atmosphere. We verify in several experiments that the emulator derivatives, which require neither additional training nor extensive postprocessing to obtain, can indeed be used as a valid substitute for the derivatives of the simulator.
    Description: Key Points: Deep learning models trained on simulation data can learn the dynamics of Earth science simulators. Deep learning models also learn the input–output derivatives of the state‐update function, which are unavailable for many simulators. We show on Lorenz‐96 that these learned derivatives can be used directly for data assimilation and parametrization tuning.
    Keywords: 550 ; machine learning ; deep learning ; data assimilation ; parametrization tuning ; model Jacobians ; Lorenz‐96
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  • 9
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    Zur Geschichte der Geophysik in Deutschland (2021)
    Deutsche Geophysikalische Gesellschaft, Hamburg
    In:  Herausgeberexemplar
    Details
    Publication Date: 2021-08-07
    Description: Die Jubiläumsschrift zum 75jährigen Bestehen der Deutschen Geophysikalischen Gesellschaft (DGG) enthält zahlreiche Beiträge von Mitgliedern zu vier Schwerpunkten: 1) Eine Aktualisierung der Geschichte der DGG vor allem zu den an Ereignissen reichen letzten 25 Jahren sowie Ergänzungen zu vorausgegangenen Darstellungen. 2) Die Darstellung der Geschichte geophysikalischer Institute und Institutionen in Deutschland inklusive eines Rückblicks auf das erfolgreiche Wirken ihrer verdienstvollen Persönlichkeiten. 3) Die Beschreibung einer Auswahl in der deutschen Geophysik angegangener Großprojekte der letzten 25 Jahre. 4) In Anlehnung an die Festschrift zum 50jährigen Gründungsjubiläum ist schließlich noch ein Kapitel zu geophysikalischen 'Detailthemen' ausgeführt. In ihm sind auch Beiträge enthalten, die Traditionslinien bzw. Arbeiten betreffen, die in der früheren DDR aufgenommen worden waren und z.T. keine direkte Fortsetzung an einer Nachfolgeinstitution gefunden haben.
    Description: commemorativepublication
    Keywords: 550 ; Geschichte der Geophysik ; Festschriften {Geophysik} ; Deutsche Geophysikalische Gesellschaft ; Deutschland ; Geophysik ; Geschichte ; FID-GEO-DE-7
    Language: German
    Type: anthology_digi
    Format: 226 S.
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  • 10
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    Cable reverberations during wireline distributed acoustic sensing measurements: their nature and methods for elimination (2021)
    Details
    Publication Date: 2021-07-21
    Description: The application of distributed acoustic sensing in borehole measurements allows for the use of fibre optic cables to measure strain. This is more efficient in terms of time and costs compared with the deploying of conventional borehole seismometers. Nevertheless, one known drawback for temporary deployment is represented by the freely hanging wireline cable slapping and ringing inside the casing, which introduces additional coherent coupling noise to the data. The present study proposes an explanation for the mechanism of noise generation and draws an analogy with similar wave propagation processes and phenomena, such as ghost waves in marine seismics. This observation allows to derive a ringing noise filter function, to study its behaviour and to consider known effects of the gauge length filter. After examining existing methods aimed at eliminating ringing noise and results of their application, we propose a two‐step approach: (1) developing a denoising method based on a matching pursuit decomposition with Gabor atoms and (2) subtracting the noise model for imaging improvement. The matching pursuit method focuses on decomposing the original input signal into a weighted sum of Gabor functions. Analysing Gabor atoms properties for frequency, amplitude and position in time provides the opportunity to distinguish parts of the original signal denoting noise caused by the vibrating cable. The matching pursuit decomposition applied to the distributed acoustic sensing‐vertical seismic profiling data at the geothermal test site Groß Schönebeck provides a versatile processing instrument for noise suppression.
    Description: German Federal Ministry of Economic Affairs and Energy
    Keywords: 550 ; Borehole geophysics ; Distributed acoustic sensing ; Noise ; Signal processing ; Vertical seismic profiling
    Type: article
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