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  • 1
    Online Resource
    Online Resource
    Computational methods for optimizing distributed systems (1984)
    Orlando : Academic Press
    Details Availability
    Keywords: Differential equations, Parabolic Numerical solutions ; Boundary value problems Numerical solutions ; Distributed parameter systems ; Geometry, Riemannian ; Distributed parameter systems ; Boundary value problems Numerical solutions ; Differential equations, Parabolic Numerical solutions ; Differential equations, Parabolic Numerical solutions. Boundary value problems ; Numerical solutions. Distributed parameter systems ; Distributed parameter systems. Optimal control ; Distributed parameter systems ; MATHEMATICS ; Differential Equations ; Partial ; Boundary value problems ; Numerical solutions ; Differential equations, Parabolic ; Numerical solutions ; Electronic books ; Electronic books ; Optimierung ; System mit verteilten Parametern ; Numerisches Verfahren ; Optimale Kontrolle ; Randwertproblem ; Parabolische Differentialgleichung ; Numerisches Verfahren ; System mit verteilten Parametern ; Kontrolltheorie ; Parabolische Differentialgleichung ; Numerisches Verfahren ; Optimale Kontrolle ; Randwertproblem ; Optimale Kontrolle ; Randwertproblem ; Parabolische Differentialgleichung ; Numerisches Verfahren ; System mit verteilten Parametern ; Kontrolltheorie ; Parabolische Differentialgleichung ; Numerisches Verfahren ; Optimale Kontrolle ; Randwertproblem
    Description / Table of Contents: Computational methods for optimizing distributed systems
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (XIII, 317 Seiten)
    Edition: Elsevier e-book collection on ScienceDirect
    ISBN: 9780126854800 , 0080956785
    Series Statement: Mathematics in science and engineering 173
    URL: http://www.sciencedirect.com/science/book/9780126854800
    URL: http://www.sciencedirect.com/science/bookseries/00765392/173
    URL: https://www.sciencedirect.com/science/bookseries/00765392/173
    URL: http://www.sciencedirect.com/science/book/9780126854800
    URL: https://www.sciencedirect.com/science/book/9780126854800
    RVK:
    SK 920
    RVK:
    SK 915
    Language: English
    Note: Literaturverzeichnis: Seite 301-312
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  • 2
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    Thermoelastic properties of ringwoodite (Fex,Mg1−x)2SiO4: Its relationship to the 520km seismic discontinuity (2012)
    In:  Earth and Planetary Science Letters
    Details
    Publication Date: 2020-02-12
    Description: We combine density functional theory (DFT) within the local density approximation (LDA), the quasiharmonic approximation (QHA), and a model vibrational density of states (VDoS) to calculate elastic moduli and sound velocities of γ-(Fex,Mg1−x)2SiO4 (ringwoodite), the most abundant mineral of the lower Earth's transition zone (TZ). Comparison with experimental values at room-temperature and high pressure or ambient-pressure and high temperature shows good agreement with our first-principles findings. Then, we investigate the contrasts associated with the β→γ(Fex,Mg1−x)2SiO4 transformation at pressures and temperatures relevant to the TZ. This information offers clearly defined reference values to advance the understanding of the nature of the 520 km seismic discontinuity.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 3
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    West–east transition from underplating to steep subduction in the India–Tibet collision zone revealed by receiver-function profiles (2016)
    In:  Earth and Planetary Science Letters
    Details
    Publication Date: 2020-02-12
    Description: Closely-spaced receiver-function profiles in the east-central India–Tibet collision zone reveal drastic west–east changes of the crustal and upper mantle structure. West of ∼91.5°E, we show the Indian crust-mantle boundary (Moho) extending subhorizontally from ∼50 km depth below sea level under the High Himalaya to ∼90 km under the central Lhasa terrane. Further north, this boundary transitions to become the top of the Indian lithospheric mantle and, becoming faint but still observable, it can be tracked continuously to ∼135 km depth near ∼31.5°N. The top of the Indian lithospheric mantle is clearly beneath the Tibetan Moho that is also a conspicuous boundary, undulatory at 60–75 km depth from the central Lhasa terrane to the north end of our profile at ∼34°N. This geometry is consistent with underthrusting of Indian lower crust and underplating of the Indian plate directly beneath southern Tibet. In contrast, east of ∼91.5°E, the Indian Moho is only seen under the southernmost margin of the Tibetan plateau, and eludes imaging from ∼50 km south of the Yarlung-Zangbo suture to the north. The Indian lower crust thins greatly and in places lacks a clear Moho. This is in contrast to our observation west of ∼91.5°E, that the Indian lower crust thickens northwards. A clear depression of the top of the Indian lower crust is also observed along west–east oriented profiles, centered above the region where the Indian Moho is not imaged. Our observations suggest that roll-back of the Indian lithospheric mantle has occurred east of ∼91.5°E, likely due to delamination associated with density instabilities in eclogitized Indian lower crust, with the center of foundering beneath the southern Lhasa terrane slightly east of 91.5°E.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 4
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    Thermal elasticity of (Fex,Mg1−x)2SiO4 olivine and wadsleyite (2013)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2020-02-12
    Description: [1] We present first-principles results for elastic moduli (bulk, K, and shear, G) and acoustic velocities (compressional, VP, shear, VS, and bulk VΦ) of olivine (α) and wadsleyite (β) (Fex,Mg1 − x)2SiO4, at high pressure (P) and temperature (T) with varying iron content (0 ≤ x ≤ 0.125). Pressure and temperature derivatives of these properties are analyzed. We show that adding 12.5% of Fe in forsterite softens VP and VS by ∼3–6%, the same effect as raising temperature by ∼1000 K in dry olivine at 13.5 GPa—the same is true in wadsleyite. This study suggests that Fe is effective in producing seismic velocity heterogeneity at upper mantle and transition zone conditions and should be another key ingredient, in addition to temperature and water content variations, in interpreting seismic heterogeneities in the transition zone. The effect of Fe on density, elastic, and velocity contrasts across the α → β transition is also addressed at relevant conditions. We show that simultaneous changes of composition, temperature, and pressure do not affect significantly the relative density contrasts. We also find that compressional and shear impedance contrasts result primarily from velocity discontinuities rather than density discontinuity.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 5
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    Validating HY-2A CMR precipitable water vapor using ground-based and shipborne GNSS observations (2020)
    In:  Atmospheric Measurement Techniques
    Details
    Publication Date: 2020-12-10
    Description: The calibration microwave radiometer (CMR) on board the Haiyang-2A (HY-2A) satellite provides wet tropospheric delay correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. The ground-based global navigation satellite system (GNSS) provides precise precipitable water vapor (PWV) with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 International GNSS Service (IGS) stations along the global coastline and 56 d shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made in the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm as the root mean square (rms) within 100 km. Geographically, the rms is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an rms of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 6
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    Receiver-function imaging of the lithosphere at the Kunlun-Qaidam boundary, Northeast Tibet (2019)
    In:  Tectonophysics
    Details
    Publication Date: 2020-11-24
    Description: We studied the crustal structure and tectonics in the north Tibetan Plateau from the Songpan-Ganzi terrane to the Qaidam Basin using teleseismic receiver-function imaging, across a major lithospheric boundary, the Kunlun- Qaidam boundary, where previous studies suggest a ~15–20-km change in crustal thickness from thicker crust in the Kunlun Mountains to thinner crust in the Qaidam Basin. We report P receiver functions for 70 stations, largely the International Deep Profiling of Tibet and the Himalaya (INDEPTH), phase IV, experiment. Our most dense station coverage is located along the roughly north-south INDEPTH-IV active-source seismic profile at approximately 95° E longitude. Azimuthal and geographical changes in the receiver functions reveal significant changes in crustal structure and Vp/Vs from across the study area. Receiver functions show strong converters that we interpret as the Moho at ~70 km depth beneath the Qiangtang, Songpan-Ganzi terranes and Kunlun Mountains and at ~50 km depth beneath the central Qaidam Basin. This large change in crustal thickness occurs〉 50 km north of the North Kunlun strike-slip fault, on which the 2001 M8.1 Kunlun earthquake occurred. Receiver functions for some of the stations north of the thickness change at the Kunlun-Qaidam boundary also show a deeper ~70-km bright converter in addition to the 50-km converter. The two converters appear to overlap by up to ~30 km in some locations along the south Qaidam Basin. We combine previous results with these new results to discuss implications for mechanisms for crustal thickening in the north Tibetan Plateau including crustal flow and crustal injection. At depths imaged here, shallower than ~100 km, we see no evidence of southward subduction of Eurasian lithosphere.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 7
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    Seismology Across the Northeastern Edge of the Tibetan Plateau (2008)
    In:  Eos, Transactions American Geophysical Union
    Details
    Publication Date: 2020-02-12
    Description: On 12 May, a great earthquake (Ms=8.0) on the Longmenshan thrust fault rumbled through Chinas Sichuan province, killing more than 69,000 people and injuring 374,000. The Longmenshan thrust is part of the eastern border of the Tibetan Plateau, but it is not the plateaus only restless margin. An even larger earthquake (Ms=8.1) on the Kunlun fault shook northeastern Tibet in 2001, fortunately in a sparsely populated area. These massive quakes underscore the importance of understanding the tectonic response of Asia to collision by India. The International Deep Profiling of Tibet and the Himalaya (INDEPTH) program explores the dynamics of the India-Asia collision. Though many past geophysical studies have focused on the Himalayas and the southern Tibetan Plateau, the INDEPTH IV project examines the deep structure of the northeastern margin of the Tibetan Plateau.
    Keywords: 550 - Earth sciences
    Language: English
    Type: info:eu-repo/semantics/article
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  • 8
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    Sub-seasonal prediction of drought over the Horn of Africa with Neural Networks (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-02
    Description: Socioeconomic livelihoods in the Horn of Africa (HA) are highly dependent on seasonal rainfall, which occurs during two main seasons: October-November-December (OND) and March-April-May (MAM). During the two last decades the HA region has been affected by severe and prolonged droughts, leading to acute food insecurity, shortage of drinking water, and increasing risk of disease. Sub-seasonal drought prediction over the HA, from two weeks to two months, is therefore crucial for decision making and early warnings across several sectors. The sub-seasonal prediction of high and low precipitation extremes (PEs) by dynamical forecast systems is challenging for both rainy seasons, but there may be potential for extending the current prediction timescale based on remote drivers. To investigate the sub-seasonal predictability of PEs during the OND season we build a Long Short-Term Memory (LSTM) Neural Network predicting biweekly precipitation tercile categories over the HA region. The LSTM is trained on observational and reanalysis data during the period 1981—2020 and provides predictions with lead times of one week to one month. The results show that floods can be more skillfully predicted than droughts for all lead times. Moreover, we use explainable AI methods to explore the contribution of remote drivers to the predictions and potential sub-seasonal forecast opportunities for PEs. Preliminary results show that the sea surface temperature over the tropical Pacific is important for the LSTM prediction, but further investigation is needed to determine more factors affecting the prediction skill for PEs over the HA region.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 9
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    An integrated multi-structure monthly precipitation prediction model and its application in the middle and lower reaches of Yangtze river basin (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-02
    Description: Monthly precipitation prediction is of great significance to bridge the gap between short-term weather forecast and seasonal forecast. However, due to the complexity of the climate system, there is still a great deal of uncertainty in the prediction of precipitation at the monthly scale. In order to reduce the uncertainty of the monthly precipitation predictions results，we analyzed the corrective effect of BJP (Bayesian Joint Probabilistic ) and EMOS (Ensemble Model Output Statics) model on precipitation bias prediction using S2S (sub-seasonal to seasonal scale) near-real-time overall forecast data and re-forecast data from five global data centers, including ECMWF, NCEP, UKMO, JMA and KMA. According to the advantages of different models the integrated multi-structure monthly precipitation prediction model was constructed based on EM (Expectation-Maximum) algorithm. The prediction application of monthly precipitation was carried out during the flood season of 1981~2010 in the middle and lower reaches of the Yangtze River, and the result showed as follows. (1)The monthly precipitation prediction results of the ensemble model showed that the Nash efficiency coefficient reached more than 0.6 and the correlation coefficient was 0.83. It indicates that the prediction sequence and the measured sequence of the ensemble model had good consistency. (2) The average relative deviation of the monthly precipitation prediction results is 25%, which effectively reduces the uncertainty of the monthly precipitation prediction results of a single model compared with the monthly precipitation forecast results of a single model. The results provide scientific support for improving the accuracy of drought or flood prediction.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 10
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    Insolation triggered abrupt cooling at the end of interglacials and implication for the future (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-25
    Description: Various paleoclimate records show that the end of interglacials of the late Pleistocene was marked by abrupt cooling events. Strong abrupt cooling occurring when climate was still in a warm interglacial condition is puzzling. Our transient climate simulations for the eleven interglacial (sub)stages of the past 800,000 years show that, when summer insolation in the Northern Hemisphere (NH) high latitudes decreases to a critical value (a threshold), it triggers a strong, abrupt weakening of the Atlantic meridional overturning circulation and consequently an abrupt cooling in the NH. The mechanism involves sea ice-ocean feedbacks in the Northern Nordic Sea and the Labrador Sea (Yin et al., 2021, doi: 10.1126/science.abg1737). The insolation-induced abrupt cooling is accompanied by abrupt changes in precipitation, vegetation from low to high latitudes and in particular by abrupt snow accumulation in polar regions. The timing of the simulated abrupt events at the end of interglacials is highly consistent with those observed in marine and terrestrial records, especially with those observed in high-resolution, absolutely-dated speleothem records in Asia and Europe, which validates the model results and reveals that the astronomically-induced slow variations of insolation could trigger abrupt climate events. Our results show that the insolation threshold occurred at the end of each interglacial of the past 800,000 years, suggesting its fundamental role in terminating the warm climate conditions of the interglacials. The next insolation threshold will occur in 50,000 years, implying an exceptionally long interglacial ahead.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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