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  • English  (47)
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  • 1
    Online Resource
    Online Resource
    Dordrecht :Springer Netherlands,
    Keywords: Microbial proteins. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (219 pages)
    Edition: 1st ed.
    ISBN: 9781402028441
    DDC: 636.208522
    Language: English
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  • 2
    Publication Date: 2020-02-12
    Description: The multi-constellation Global Navigation Satellite Systems (GNSS) offers promising potential for the retrieval of real-time (RT) atmospheric parameters to support time-critical meteorological applications, such as nowcasting or regional short-term forecasts. In this study, we processed GNSS data from the globally distributed Multi-GNSS Experiment (MGEX) network of about 30 ground stations by using the precise point positioning (PPP) technique for retrieving RT multi-GNSS tropospheric delays. RT satellite orbit and clock product streams from the International GNSS Service (IGS) were used. Meanwhile, we assessed the quality of clock and orbit products provided by different IGS RT services, called CLK01, CLK81, CLK92, GFZC2, and GFZD2, respectively. Using the RT orbit and clock products, the performances of the RT zenith total delays (ZTD) retrieved from single-system as well as from multi-GNSS combined observations were evaluated by comparing with the U.S. Naval Observatory (USNO) final troposphere products. With the addition of multi-GNSS observations, RT ZTD estimates with higher accuracy and enhanced reliability compared to the single-system solution can be obtained. Compared with the Global Positioning System (GPS)-only solution, the improvements in the initialization time of ZTD estimates are about 5.8% and 8.1% with the dual-system and the four-system combinations, respectively. The RT ZTD estimates retrieved with the GFZC2 products outperform those derived from the other IGS-RT products. In the GFZC2 solution, the accuracy of about 5.05 mm for the RT estimated ZTD can be achieved with fixing station coordinates. The results also confirm that the accuracy improvement (about 22.2%) can be achieved for the real-time estimated ZTDs by using multi-GNSS observables, compared to the GPS-only solution. In the multi-GNSS solution, the accuracy of real-time retrieved ZTDs can be improved by a factor of up to 2.7 in the fixing coordinate mode, compared with that in the kinematic mode.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
    Publication Date: 2021-10-22
    Description: Geobiology explores how Earth's system has changed over the course of geologic history and how living organisms on this planet are impacted by or are indeed causing these changes. For decades, geologists, paleontologists, and geochemists have generated data to investigate these topics. Foundational efforts in sedimentary geochemistry utilized spreadsheets for data storage and analysis, suitable for several thousand samples, but not practical or scalable for larger, more complex datasets. As results have accumulated, researchers have increasingly gravitated toward larger compilations and statistical tools. New data frameworks have become necessary to handle larger sample sets and encourage more sophisticated or even standardized statistical analyses. In this paper, we describe the Sedimentary Geochemistry and Paleoenvironments Project (SGP; Figure 1), which is an open, community-oriented, database-driven research consortium. The goals of SGP are to (1) create a relational database tailored to the needs of the deep-time (millions to billions of years) sedimentary geochemical research community, including assembling and curating published and associated unpublished data; (2) create a website where data can be retrieved in a flexible way; and (3) build a collaborative consortium where researchers are incentivized to contribute data by giving them priority access and the opportunity to work on exciting questions in group papers. Finally, and more idealistically, the goal was to establish a culture of modern data management and data analysis in sedimentary geochemistry. Relative to many other fields, the main emphasis in our field has been on instrument measurement of sedimentary geochemical data rather than data analysis (compared with fields like ecology, for instance, where the post-experiment ANOVA (analysis of variance) is customary). Thus, the longer-term goal was to build a collaborative environment where geobiologists and geologists can work and learn together to assess changes in geochemical signatures through Earth history. With respect to the data product, SGP is focused on assembling a well-vetted and comprehensive dataset that is tractable to multivariate statistical analyses accounting for multiple geological and methodological biases. Phase 1 of the project, which focused on the Neoproterozoic and Paleozoic, has been completed. Future phases will capture a broader range of geologic time, data types, and geography. The database contains tens of thousands of unpublished data points provided by consortium members, as well as detailed metadata that go beyond what is contained in papers. In many cases, these represent measurements that are tangential to a given published study but still of high utility to database studies; these allow the community to address questions that would be impossible to answer solely with the published data. For instance, in order to use a proxy such as Mo/TOC (total organic carbon) ratios in mudrocks deposited under a euxinic water column, the full suite of trace metal, iron speciation, and total organic carbon data is needed. Likewise, geospatial information is required to account for sampling biases, and many statistical learning approaches cannot accept, or have difficulty with, incomplete geological predictor variables. Ultimately, it is this complete data matrix that will allow for SGP’s most insightful analyses.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 4
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    In:  Protokoll zum 23. Schmucker-Weidelt-Kolloquium für Elektromagnetische Tiefenforschung
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 5
    Publication Date: 2020-02-14
    Description: The correction of higher-order ionospheric (HOI) delays remaining in the dual-frequency ionosphere-free combined observations is suggested after the confirmation of its impact on precise Global Navigation Satellite System (GNSS) data processing. However, in the precise orbit determination (POD) for generating ultra-rapid orbits, the higher-order corrections are not always considered most likely because a RT ionospheric model needed for calculating the higher-order corrections is hardly available or the HOI impact is believed rather small compared to the accuracy of the predicted orbit. With the increasing requirement on the positioning performances from various applications, providing more accurate and reliable ultra-rapid orbits becomes an essential task of the real-time GNSS precise positioning services. In this contribution, the temporal–spatial characteristics of HOI effects on GNSS observables are investigated thoroughly using data collected from International GNSS Service (IGS) global ground stations and fluctuations of the higher-order delays up to several centimeters are detected during periods of high ionospheric activity. Hereafter, we evaluate the HOI effects on the multi-GNSS POD based on a network with globally distributed IGS stations. Results show that owing to the applied HOI corrections, the agreement of overlapping orbits can be improved significantly for all satellites and especially in radial direction. The three-dimensional RMS values of the overlapping differences are reduced from 1.6, 2.0, 4.6 and 1.7 to 1.0, 1.1, 3.4, and 1.5 cm for GPS, GALILEO, BDS, and GLONASS, respectively. Furthermore, the orbit improvement is also confirmed by the satellite laser ranging (SLR) observations over a 2-month time period where the STD of SLR residuals is reduced by HOI corrections from 6.4 to 5.3 cm for the BDS-IGSO satellites.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 6
    Publication Date: 2022-01-28
    Description: Lagrangian particle-based smoothed particle hydrodynamics (SPH) is increasingly widely used in landslide modelling. This paper investigates four important issues not addressed by previous studies on SPH modelling of large-scale landslides, i.e., convergence property, influence of constitutive parameters, scale effect and friction reduction, and influence of different treatments of the viscous effect. The GPU-acceleration technique is employed to achieve high-resolution three-dimensional (3D) modelling. The Baige landslide is investigated by comparing numerical results with field data, and detailed analyses on the four issues are provided. Suggestions on particle resolution, constitutive parameter, and formulations of viscous discretization are also presented for future SPH modelling of large-scale landslides.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 7
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    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Publication Date: 2023-08-02
    Description: The second national pollution source survey showed that agricultural non-point source pollution (ANP) has become one of the main causes of water environment deterioration in Guangdong Province. It is important to clarify the ANP status in the province for the prevention and control of water pollution and the construction of rural revitalization. The improved export coefficient method was used to analyze the annual ANP loads and their spatial and temporal variation characteristics in Guangdong Province from 2009 to 2019. The seasonal and monthly pollution loads of ANP were also evaluated with consideration of monthly differences in fertilizer application, precipitation, livestock, and aquaculture. The impact of ANP on the water environment was evaluated by the unit area load coefficient method, and the main sources of ANP were explored. The results indicate that (i) from 2009 to 2019, the total nitrogen load in Guangdong province showed a decreasing trend and the total phosphorus load showed a rising trend with spring and summer being the peak seasons of pollution emissions in a year; (ii) The total nitrogen load trended decreasing in 76.2% of the cities and the total phosphorus load trended increasing in 61.9% of the cities; (iii) in general, the environmental damage caused by agricultural nitrogen and phosphorus loads in western Guangdong was more serious than that in Pearl River Delta, northern and eastern Guangdong; and (iv)the contribution rate of pollution source to nitrogen and phosphorus pollution loads from high to low is livestock and poultry breeding, planting and aquaculture.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 8
    Publication Date: 2023-08-08
    Description: On November 23〈sup〉rd〈/sup〉 2022, a M〈sub〉W〈/sub〉 6.0 earthquake occurred in direct vicinity of the M〈sub〉W〈/sub〉 7.1 Düzce earthquake that ruptured a portion of the North Anatolian Fault in 1999. The M〈sub〉w〈/sub〉 6.0 event was attributed to a small fault portion of the Karadere segment that did not rupture during the 1999 sequence. We analyze the spatio-temporal evolution of the M〈sub〉W〈/sub〉 6.0 Gölyaka-Düzce seismic sequence at various scales and resolve the source properties of the mainshock. Modelling the decade-long evolution of background seismicity of the Karadere Fault employing an Epistemic Type Aftershock Sequence model shows that this fault was almost seismically inactive before 1999, while a progressive increase in seismic activity is observed from 2000 onwards. A newly generated high-resolution seismicity catalog from 1 month before the mainshock until six days after created using Artificial Intelligence-aided techniques shows only few events occurring within the rupture area within the previous month, no spatio-temporal localization process and a lack of immediate foreshocks preceding the rupture. The aftershock hypocenter distribution suggests the activation of both the Karadere fault which ruptured in this earthquake as well as the Düzce fault that ruptured in 1999. First results on source parameters and the duration of the first P-wave pulse from the mainshock suggest that the mainshock propagated eastwards in agreement with predictions from a bimaterial interface model. The M〈sub〉W〈/sub〉 6.0 Gölyaka-Düzce represents a good example of an earthquake rupture with damaging potential within a fault zone that is in a relatively early stage of the seismic cycle.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 9
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    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Publication Date: 2023-08-16
    Description: Complex fault geometry can strongly affect earthquake rupture processes and slip sequences. I will first present our recent work on modeling earthquake and slow slip sequences on 3D fault surfaces, with applications to the Yingxiu-Beichuan fault (YBF) which hosted the 2008 Mw 7.9 Wenchuan earthquake in China and the Cascadia subduction zone. In the rate-and-state friction computational framework, earthquake and aseismic slip nucleate and propagate spontaneously under the influence of long-term tectonic loading and heterogeneous frictional properties. In particular, fault dip angle has a primary control on the along-strike segmentation of simulated earthquake and slow slip, in general agreement with observations from YBF and Cascadia. Fault local strike angle on the other hand strongly affects small-scale along-strike variations in the rupture speed and slip rate. Next, I will introduce a newly developed mixed-flux-based discontinuous Galerkin method and its application to simulate fully dynamic ruptures on complex fault geometries. The new method greatly reduces numerical dependence on mesh quality, and can accommodate complex fault properties including geometry, material heterogeneities and multi-physics mechanisms such as off-fault plasticity and thermal pressurization.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 10
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    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Publication Date: 2023-08-02
    Description: The recent Mw 7.4 Madoi, Tibet earthquake provides a valuable opportunity to assess the contribution of the fully operational global BeiDou Navigation Satellite System (BDS-3) and other Global Navigation Satellite Systems (GNSS) in real-time seismic waveform capture. This event was successfully recorded by 111 1-Hz GNSS stations and 16 200-Hz strong motion stations. All GNSS stations are capable of recording BDS, GPS, GLONASS and Galileo observations. The variometric approach has been expanded to process multi-frequency and multi-GNSS data to estimate velocity, and then the coseismic displacements can be obtained by integrating the velocities. The results indicate that the phase-specific inter-frequency clock bias between BDS and GPS has minimal impact on velocity and displacement estimation, and there is no significant accuracy improvement with the help of a third frequency. Although the velocities derived from BDS are more noisy than those from GPS, the accuracy of integrated horizontal displacements for the regional BDS (BDS-2) shows 20% improvement with the RMS value of 0.5 cm. Compared to BDS-2, the seismic waveforms retrieved from BDS-3 shows nearly 50% better accuracy, due to the higher observation quality and stronger satellite geometry, and the performance can be further improved through fusion with multi-GNSS. The GNSS-derived seismic waveforms are consistent with those from accelerometer data. The inversion of the rapid rupture process indicates that BDS can provide a more reliable estimation of the fault slip distribution than GPS, and the performance can be further improved by using the GCRE observations, which will undoubtedly contribute to seismology applications.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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