Article
Geochemistry & Geophysics
Hugo Lecomte, Severine Rosat, Mioara Mandea, Jean-Paul Boy, Julia Pfeffer
Summary: Space gravity measurements have been used to study mass variations on Earth's surface and within the mantle. However, variations in the Earth's core can also be observed in gravity field variations measured by GRACE and GRACE Follow-On satellites.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2023)
Article
Physics, Applied
M. H. Mostafa, N. Ha-Van, P. Jayathurathnage, X. Wang, G. Ptitcyn, S. A. Tretyakov
Summary: The Chu limit restricts the operational bandwidth of resonant circuits due to the size limitation of the resonator. This limitation hinders the miniaturization of antennas, as their bandwidth is inversely proportional to their size. To overcome this, we propose the use of slow time modulation of resistive elements to engineer the bandwidth of small antennas. The modulation of resistance induces a virtual impedance that can be fully controlled by modulation parameters and optimize the frequency response of a resonant circuit.
APPLIED PHYSICS LETTERS
(2023)
Article
Geochemistry & Geophysics
Zhaohui Chen, Shi Chen, Bei Zhang, Linhai Wang, Lei Shi, Hongyan Lu, Jinzhao Liu, Weimin Xu
Summary: This study applied Bayesian gravity adjustment method to the hybrid gravity network in Southeastern Tibet for the first time, effectively reducing measurement uncertainties. By using the equivalent source inversion algorithm, the study investigated mass redistributions in the deep crust and found close consistency with active tectonic block boundaries and low-velocity/high-conductivity zones.
PURE AND APPLIED GEOPHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Maaz Mahadi, Tarig Ballal, Muhammad Moinuddin, Ubaid M. Al-Saggaf
Summary: Recursive least-squares (RLS) algorithms are widely used in various applications. This paper focuses on time-varying regularized RLS (RRLS) techniques and proposes a low-complexity update method using an approximate recursive formula. Simulation results demonstrate the superiority of the time-varying RRLS strategy over the fixed one.
APPLIED SCIENCES-BASEL
(2022)
Article
Physics, Multidisciplinary
Benjamin Apffel, Sander Wildeman, Antonin Eddi, Emmanuel Fort
Summary: In this study, we investigate and implement the temporal analog in time disordered systems. We introduce randomly distributed temporal interfaces to a spatially homogeneous medium to create a temporal structure. The observed wave field is the result of interference between reflected and refracted waves on the interfaces. The growth of waves exponentially depends on the disorder level, similar to the evolution model in spatial cases. The relative position of the momentum gap in time modulated systems plays a crucial role in wave field evolution. By compensating for damping with tuned excitation, localized transient waves appear on the liquid surface, resulting from a specific history of multiple interferences.
PHYSICAL REVIEW LETTERS
(2022)
Review
Geosciences, Multidisciplinary
Yiqing Zhu, Xiong Yang, Fang Liu, Yunfeng Zhao, Shouchun Wei, Guoqing Zhang
Summary: This paper mainly introduces the application and progress of time-varying gravity in earthquake research in China. Gravity changes before and after significant earthquakes have been observed, and high-precision instruments were introduced to carry out mobile gravity observation. The development of a comprehensive gravity observation network in China has played a crucial role in medium-term earthquake prediction and the study of the earthquake mechanism. However, there are still existing issues in time-varying gravity monitoring in China, and future research prospects are also discussed.
FRONTIERS IN EARTH SCIENCE
(2023)
Article
Automation & Control Systems
Xian Yu, Xiaozhu Fang, Biqiang Mu, Tianshi Chen
Summary: For data-driven iterative learning control (ILC) methods, the model estimation and controller design problems are transformed into parameter estimation problems. Choosing the model order carefully is crucial to avoid models with large variance or bias. Using regularization, such as kernel-based regularization method (KRM), is an emerging trend in system identification to handle this issue. Integrating KRM into data-driven ILC for repetitive linear time-varying systems is proposed in this paper, and the method is shown to have ultimately bounded tracking error in the iteration domain. Numerical simulations demonstrate that the proposed method outperforms the least squares method and existing data-driven ILC methods in terms of convergence speed, accuracy, and robustness.
Article
Engineering, Marine
Shuaipeng Gao, Tijing Cai
Summary: This paper proposes a parallel multiple methods with adaptive decision making (PMMADM) model for gravity-aided navigation, which improves the positioning accuracy and long-term stability of this navigation method.
JOURNAL OF MARINE SCIENCE AND ENGINEERING
(2023)
Article
Chemistry, Analytical
Huanlin Liu, Hongwei Ma
Summary: This paper proposes a novel time-varying external force identification method using group sparse regularization based on prior knowledge in the redundant dictionary. By establishing the relationship between time-varying external force and acceleration responses, a redundant dictionary is designed to create a sparse expression of external force. The prior knowledge is used to determine the group structures of atoms, thereby reducing the complexity in the process of identifying external force from measured acceleration responses.
Article
Engineering, Mechanical
Huanlin Liu, Ziwei Luo, Ling Yu
Summary: A novel MFI method based on a semi-convex function is proposed in this study, aiming to improve the accuracy of MFI results; by decomposing the moving force into constant and time-varying force components and identifying the forces through an alternating iterative method (AIM) and regularization techniques, the proposed method shows better performance compared to existing regularization methods in identifying moving forces accurately from structural responses.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2021)
Article
Geochemistry & Geophysics
Samurdhika Rathnayake, Robert Tenzer, Wenjin Chen, Mehdi Eshagh, Martin Pitonak
Summary: This study compares different isostatic and gravimetric methods for recovering the Moho depth under the oceanic crust and continental margins, with results indicating that the VMM model is likely the most suitable method considering lithospheric mantle density information. The Airy method tends to overestimate the Moho depth under oceanic volcanic formations.
SURVEYS IN GEOPHYSICS
(2021)
Article
Physics, Particles & Fields
L. B. Ednaldo Junior, Manuel E. Rodrigues, Henrique A. Vieira
Summary: In this paper, the Shapiro time delay is proposed as a tool to distinguish between different black hole solutions. The analytic Shapiro time is calculated using first order expansions for four solutions: Schwarzschild, Reissner-Nordstrom, Bardeen, and Ayon-Beato and Garcia. A numerical experiment based on measurements in the solar system is conducted, which involves the outward and return paths of light passing through a black hole at the center. Different delay times of the order of 10(-4) s and 10(-6) s for a stellar black hole, and variations on the order of hours for a supermassive black hole are obtained. Considering the accuracies currently achieved in solar system measurements are on the order of 10(-12) s, it is believed that this mechanism could be used in the determination of black hole models in the near future.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Geosciences, Multidisciplinary
Yang Ou, Qingtian Lu, Jiayong Yan, Dingyu Jia, Yang Li
Summary: Regularization theory is a powerful tool in addressing the ill-posed problem of potential field inversion. This paper analyzes the applications of stabilizing functionals in potential field inversion and proposes two improvements. By adopting an L0E norm stabilizing functional and a reformulated modulus constraint, sparse models with reasonable values and dipping structures can be obtained.
JOURNAL OF APPLIED GEOPHYSICS
(2023)
Article
Geosciences, Multidisciplinary
A. Vasanthi, M. Santosh
Summary: This study focuses on the lithospheric architecture and geodynamic evolution of the Dharwar craton in southern India and surrounding regions, uncovering a new feature named the "Koyna-Coimbatore rift" and successfully delineating the boundaries of major geotectonic units.
Article
Physics, Multidisciplinary
E. Harikumar, Suman Kumar Panja, Vishnu Rajagopal
Summary: This paper investigates the non-commutative corrections to the maximal acceleration in DFR space-time, finding that it decreases the magnitude of the maximal acceleration. By applying the positivity condition on the maximal acceleration in commutative space-time, upper bounds on acceleration are obtained, and lower bounds on radial distances between particles under gravitational attraction in DFR space-time are derived.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Environmental Sciences
Ibrahim Fayad, Nicolas Baghdadi, Frederic Frappart
Summary: This study validates the water level estimates from GEDI against in situ gauge station records and analyzes the factors affecting the accuracy. Results show that using viewing angle as a filtering criterion is the best compromise between retained shot count and water level estimation accuracy. V2 provides elevations with a more constant but higher bias compared to V1.
Article
Environmental Sciences
Lucia Seoane, Guillaume Ramillien, Benjamin Beirens, Jose Darrozes, Didier Rouxel, Thierry Schmitt, Corinne Salauen, Frederic Frappart
Summary: In this study, an iterative Extended Kalman Filter approach was used to recover the topographic heights of an undersea volcanic mount using gravity measurements at sea surface. The method showed good accuracy in estimating the topography, especially when regional compensation was considered. However, larger discrepancies were found in the seamount flanks due to missing high-resolution information.
Article
Environmental Sciences
Catherine Prigent, Carlos Jimenez, Lan Anh Dinh, Frederic Frappart, Pierre Gentine, Jean-Pierre Wigneron, Joseph Munchak
Summary: This study documents the variability of tropical forest structure and function using satellite observations from GPM, analyzing the seasonal and diurnal cycles of microwave data for the first time. The analysis reveals diurnal patterns in backscatter and emissivity, with differing behaviors during the dry season in the southeastern Amazonian forest.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2022)
Article
Environmental Sciences
Xiaojun Li, Jean-Pierre Wigneron, Lei Fan, Frederic Frappart, Simon H. Yueh, Andreas Colliander, Ardeshir Ebtehaj, Lun Gao, Roberto Fernandez-Moran, Xiangzhuo Liu, Mengjia Wang, Hongliang Ma, Christophe Moisy, Philippe Ciais
Summary: Passive microwave remote sensing at L-band provides an unprecedented opportunity to estimate global surface soil moisture and vegetation water content. This study presents a new algorithm (SMAP-IB) to retrieve soil moisture and L-band vegetation optical depth from SMAP radiometric observations. The results suggest that SMAP-IB performs well in capturing the temporal trends of in-situ observations and exhibits good correlation with aboveground biomass and tree height.
REMOTE SENSING OF ENVIRONMENT
(2022)
Article
Environmental Sciences
Ibrahim Fayad, Nicolas Baghdadi, Jean-Stephane Bailly, Frederic Frappart, NUria Pantaleoni Reluy
Summary: The GEDI LiDAR on the International Space Station has acquired a significant amount of shots globally, which could provide a database for measuring and monitoring inland water levels. However, the accuracy of GEDI elevation estimates is found to be lower than radar or LiDAR altimeters. This study aims to post-process the original GEDI water level estimates using an error model that considers instrumental, atmospheric, and lakes surface state factors, leading to reduced errors in elevation estimation.
Article
Multidisciplinary Sciences
Heidi Kreibich, Anne F. Van Loon, Kai Schroeter, Philip J. Ward, Maurizio Mazzoleni, Nivedita Sairam, Guta Wakbulcho Abeshu, Svetlana Agafonova, Amir AghaKouchak, Hafzullah Aksoy, Camila Alvarez-Garreton, Blanca Aznar, Laila Balkhi, Marlies H. Barendrecht, Sylvain Biancamaria, Liduin Bos-Burgering, Chris Bradley, Yus Budiyono, Wouter Buytaert, Lucinda Capewell, Hayley Carlson, Yonca Cavus, Anais Couasnon, Gemma Coxon, Ioannis Daliakopoulos, Marleen C. de Ruiter, Claire Delus, Mathilde Erfurt, Giuseppe Esposito, Didier Francois, Frederic Frappart, Jim Freer, Natalia Frolova, Animesh K. Gain, Manolis Grillakis, Jordi Oriol Grima, Diego A. Guzman, Laurie S. Huning, Monica Ionita, Maxim Kharlamov, Dao Nguyen Khoi, Natalie Kieboom, Maria Kireeva, Aristeidis Koutroulis, Waldo Lavado-Casimiro, Hong-Yi Li, Maria Carmen LLasat, David Macdonald, Johanna Mard, Hannah Mathew-Richards, Andrew McKenzie, Alfonso Mejia, Eduardo Mario Mendiondo, Marjolein Mens, Shifteh Mobini, Guilherme Samprogna Mohor, Viorica Nagavciuc, Thanh Ngo-Duc, Thi Thao Nguyen Huynh, Pham Thi Thao Nhi, Olga Petrucci, Hong Quan Nguyen, Pere Quintana-Segui, Saman Razavi, Elena Ridolfi, Jannik Riegel, Md Shibly Sadik, Elisa Savelli, Alexey Sazonov, Sanjib Sharma, Johanna Sorensen, Felipe Augusto Arguello Souza, Kerstin Stahl, Max Steinhausen, Michael Stoelzle, Wiwiana Szalinska, Qiuhong Tang, Fuqiang Tian, Tamara Tokarczyk, Carolina Tovar, Thi Van Thu Tran, Marjolein H. J. Van Huijgevoort, Michelle T. H. van Vliet, Sergiy Vorogushyn, Thorsten Wagener, Yueling Wang, Doris E. Wendt, Elliot Wickham, Long Yang, Mauricio Zambrano-Bigiarini, Gunter Bloschl, Giuliano Di Baldassarre
Summary: Risk management can reduce the impacts of floods and droughts, but faces difficulties in managing unprecedented events of a greater magnitude. Improved risk management and integrated management can help lower the impacts of more hazardous events.
Article
Environmental Sciences
Theo Gravalon, Lucia Seoane, Guillaume Ramillien, Jose Darrozes, Laurent Roblou
Summary: This study successfully derived local sea level variations at different latitudes using the Signal-to-Noise Ratio (SNR) of GNSS reflected signals and compared them with tide gauge records and models. The results indicate that GNSS reflectometry technique is effective for studying sea level variations and the response of the sea surface to atmospheric forcing.
REMOTE SENSING OF ENVIRONMENT
(2022)
Article
Remote Sensing
Minh-Cuong Ha, Jose Darrozes, Muriel Llubes, Manuela Grippa, Guillaume Ramillien, Frederic Frappart, Frederic Baup, Hakan Torbern Tagesson, Eric Mougin, Idrissa Guiro, Laurent Kergoat, Huu Duy Nguyen, Lucia Seoane, Gregory Dufrechou, Phuong-Lan Vu
Summary: With population growth, water resources will increase significantly in the coming decades. Accurate soil moisture monitoring is essential for optimizing agricultural water use. Recent GNSS-R studies use navigation signals emitted by the GNSS constellations to track changes in soil moisture. However, during drought periods, the penetration of GNSS waves into the soil reduces the accuracy of surface moisture measurements.
EUROPEAN JOURNAL OF REMOTE SENSING
(2022)
Article
Geosciences, Multidisciplinary
Hui Yang, Philippe Ciais, Frederic Frappart, Xiaojun Li, Martin Brandt, Rasmus Fensholt, Lei Fan, Sassan Saatchi, Simon Besnard, Zhu Deng, Simon Bowring, Jean-Pierre Wigneron
Summary: Changes in terrestrial carbon storage under environmental and land-use changes are crucial for regional and global carbon budgets. This study used L-band microwave vegetation optical depth to generate global maps of annual live vegetation biomass, and found that boreal and temperate forests contribute the most to the global carbon sink, while wet tropical forests serve as small carbon sources. Additionally, the study revealed that tropical deforested and degraded old-growth forests are nearly carbon neutral, while young and middle-aged forests in temperate and boreal regions are the largest sinks.
Article
Chemistry, Analytical
Benjamin Beirens, Jose Darrozes, Guillaume Ramillien, Lucia Seoane, Patrice Medina, Pierre Durand
Summary: In this study, the feasibility of using small INS for gravity measurements both during in situ experiments and on a UAV is presented. The study shows that these INS are capable of capturing the periodic signal of solid Earth tides after correcting for temperature bias. Correlation with CG5 gravimeter data at different altitudes is observed. The study also investigates the use of INS on a moving platform and the need for extensive filtering of GPS and accelerometric data due to vibrations. The method of isolating accelerometric signals related to the studied area and altitude is proposed to obtain gravity variations.
Article
Environmental Sciences
Lien Rodriguez-Lopez, David Bustos Usta, Iongel Duran-Llacer, Lisandra Bravo Alvarez, Santiago Yepez, Luc Bourrel, Frederic Frappart, Roberto Urrutia
Summary: In this study, machine learning and remote sensing techniques were combined to estimate chlorophyll-a concentration in a freshwater ecosystem in Southern Chile. The study found that the SARIMAX, LSTM, and RNN models effectively predicted the presence of algae in water bodies, with the LSTM model performing the best.
Article
Environmental Sciences
Leonardo Gutierrez, Adrian Huerta, Evelin Sabino, Luc Bourrel, Frederic Frappart, Waldo Lavado-Casimiro
Summary: This study evaluates the performance of the RE and ED datasets in soil erosion estimation models in Peru and finds that estimating with observed-corrected satellite data is more effective. The study also presents the average annual RE for Peru and identifies the spatial distribution of erosion risk areas.
Proceedings Paper
Geography, Physical
Pierre Zeiger, Frederic Frappart, Jose Darrozes
Summary: This study analyzes the potential of using GNSS Reflectometry (GNSS-R) based on observations from the CYGNSS mission to map flood dynamics in the pan-tropical area. The study shows that CYGNSS observations can effectively detect flooded areas and there is a strong correspondence between the GNSS-R parameters and the percentage of flooded areas. However, there are limitations in high-elevation areas and densely vegetated regions.
XXIV ISPRS CONGRESS: IMAGING TODAY, FORESEEING TOMORROW, COMMISSION III
(2022)
Article
Geosciences, Multidisciplinary
Benjamin Kitambo, Fabrice Papa, Adrien Paris, Raphael M. Tshimanga, Stephane Calmant, Ayan Santos Fleischmann, Frederic Frappart, Melanie Becker, Mohammad J. Tourian, Catherine Prigent, Johary Andriambeloson
Summary: This study analyzes a large record of in situ and satellite-derived observations to characterize the hydroclimatic characteristics of the Congo River basin. The results provide valuable information for hydrological modeling and studying hydrological processes in the region.
HYDROLOGY AND EARTH SYSTEM SCIENCES
(2022)