Article
Mathematics, Applied
Giona Veronelli
Summary: A basic property and useful tool in the theory of Sobolev spaces is the density of smooth compactly supported functions. On Riemannian manifolds, this property remains valid, but it may not hold on complete noncompact manifolds.
Article
Physics, Multidisciplinary
Pratik Sathe, Fenner Harper, Rahul Roy
Summary: Wannier functions play a crucial role in understanding properties of crystalline materials, with the ability to be exponentially localized and even more compactly supported in certain cases. This paper addresses the general conditions for constructing compactly supported Wannier functions, particularly in 1D non-interacting tight-binding models. It shows that the strict locality of the projection operator is necessary and sufficient for a subspace to be spanned by a compactly supported orthogonal basis.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Astronomy & Astrophysics
Bo Xiong, Yuqing Wang, Xiaolin Li, Yuxiao Li, You Yu
Summary: This study proposes a method for constructing a global ionospheric map of Total Electron Content (TEC) using spherical harmonic functions. The results show that this method can accurately reflect the properties of the ionospheric distribution and effectively monitor the ionospheric TEC response to space weather events.
ASTROPHYSICS AND SPACE SCIENCE
(2022)
Article
Mathematics
Aigerim Kalybay, Ryskul Oinarov, Yaudat Sultanaev
Summary: The paper establishes the oscillatory and spectral properties of a class of fourth-order differential operators based on the integral behavior of its coefficients at zero and infinity. To achieve these results, a certain weighted second-order differential inequality is investigated, which is of independent interest.
Article
Statistics & Probability
Moreno Bevilacqua, Christian Caamano-Carrillo, Emilio Porcu
Summary: This paper proposes a family of spatial covariance functions based on the reparameterization of the generalized Wendland family, which allows for flexible adjustment of smoothness and compact support. The proposed family can be generalized to the classic Matern model by setting specific parameter values.
JOURNAL OF MULTIVARIATE ANALYSIS
(2022)
Article
Mathematics
Youfa Li, Shengli Fan, Deguang Han
Summary: This paper addresses the single-angle reconstruction problem for compactly supported functions in the shift-invariant space. It discusses the existence of eligible direction vectors and sampling sets that can reconstruct the function using its single-angle Radon transform samples. The paper also explores the case where the generator is a positive definite function, which allows for a simpler solution. The proposed recovery results require the minimum number of samples.
JOURNAL OF FUNCTIONAL ANALYSIS
(2023)
Article
Environmental Sciences
Jayachandran P. Thayyil, Anthony M. McCaffrey, Yong Wang, David R. Themens, Christopher Watson, Benjamin Reid, Qinghe Zhang, Zanyang Xing
Summary: A study was conducted on GPS signal scintillation associated with a polar cap patch using a GPS network, ionosonde, and SuperDARN radar measurements. The observations showed that the patch moved antisunward with an average speed of 600 m/s and lasted for about 2 hours, with significant scintillation occurring on the leading edge. The scintillation was maintained as the patch moved, creating irregularities on the leading edge.
Article
Mathematics, Applied
Bartlomiej Dyda, Michal Kijaczko
Summary: This paper discusses conditions under which smooth and compactly supported functions are dense or not in the fractional Sobolev space, with a focus on the relationship between the density property and the Assouad codimension of the boundary of the set Ω. We also explicitly describe the closure of certain function spaces in the Sobolev space under mild assumptions about the geometry of set Ω, and present a variant of a fractional order Hardy inequality.
ANNALI DI MATEMATICA PURA ED APPLICATA
(2022)
Article
Mathematics, Applied
Bin Han, Ran Lu
Summary: This paper addresses the importance of framelets and the challenging problem of constructing multivariate nonseparable framelets. Utilizing the approach of quasi-tight framelets, it presents compactly supported multivariate framelets with high vanishing moments and fast transforms. By applying the oblique extension principle, the study deepens the understanding of multivariate quasi-tight framelets and their associated fast transforms.
SCIENCE CHINA-MATHEMATICS
(2022)
Article
Engineering, Multidisciplinary
Suliman Khan, Sakhi Zaman, Muhammad Arshad, Hongchao Kang, Hasrat Hussain Shah, Alibek Issakhov
Summary: This paper proposes the use of the Levin method with compactly supported radial basis functions to handle highly oscillatory integrals, along with theoretical error bounds and stability analysis. Numerical examples confirm the accuracy, efficiency, and well-conditioned behavior of the proposed method.
ENGINEERING ANALYSIS WITH BOUNDARY ELEMENTS
(2021)
Article
Multidisciplinary Sciences
Suliman Khan, Sharifah E. Alhazmi, Aisha M. Alqahtani, Ahmed EI-Sayed Ahmed, Mansour F. Yaseen, Elsayed M. Tag-Eldin, Dania Qaiser
Summary: The purpose of this work is to develop an accurate, efficient, and stable algorithm for the computation of the Fredholm integral equations with oscillatory kernels. The proposed algorithm evaluates the oscillatory part of the equations using the Levin quadrature coupled with a compactly supported radial basis function. The algorithm exhibits sparse and well-conditioned matrix even for large-scale data points.
Article
Environmental Sciences
Vladimir Truhlik, Dieter Bilitza, Dmytro Kotov, Maryna Shulha, Ludmila Triskova
Summary: This study proposes improvements to the ion temperature (Ti) model in the IRI by combining older satellite data with newly available data, resulting in a new global empirical model with solar activity variation. The proposed model captures local time variation of Ti at different altitudes and latitudes better than the current IRI-2016 Ti model, showing the importance of intercalibration and additional anchor points in the model.
Article
Astronomy & Astrophysics
A. Silwal, S. P. Gautam, P. Poudel, M. Karki, B. Adhikari, N. P. Chapagain, R. K. Mishra, B. D. Ghimire, Y. Migoya-Orue
Summary: The study analyzed the changes in total electron content (TEC) observed at different locations in Nepal during the annular solar eclipses on January 15, 2010, and June 21, 2020, finding that the eclipses caused a decrease in electron content in the ionosphere, which was closely related to the extent of the lunar disc obscuration.
Article
Statistics & Probability
Tarik Faouzi, Emilio Porcu, Moreno Bevilacqua
Summary: This study focuses on the estimation and prediction of Gaussian processes with nonseparable, dynamically compact supported DGW covariance models. Firstly, we establish the strong consistency and asymptotic normality of the maximum likelihood estimator for the microergodic parameter of the DGW covariance model under fixed-domain asymptotics. Secondly, we investigate optimal kriging prediction under the DGW model and asymptotically correct estimation of the mean squared error using a misspecified model. Our theoretical results are based on the equivalence of Gaussian measures under certain families of compact space-time covariance functions.
Article
Engineering, Aerospace
Masoud Dehvari, Sedigheh Karimi, Saeed Farzaneh, Mohammad Ali Sharifi
Summary: The International Reference Ionosphere (IRI) is a widely used empirical model for studying long-term ionospheric conditions. However, it is not precise enough for applications like Precise Point Positioning (PPP). This study uses an Extremely Learning Machine (ELM) to improve the accuracy of the IRI-2016 model by using historical data. The results show improved accuracy and the potential for high precision real-time applications.
ADVANCES IN SPACE RESEARCH
(2023)
Article
Remote Sensing
Reza Arabsahebi, Behzad Voosoghi, Mohammad J. Tourian
INTERNATIONAL JOURNAL OF REMOTE SENSING
(2020)
Article
Engineering, Aerospace
Rasoul Feizi, Behzad Voosoghi, Mir Reza Ghaffari Razin
ADVANCES IN SPACE RESEARCH
(2020)
Article
Astronomy & Astrophysics
Hossein Etemadfard, Robert Heinkelmann, Masoud Mashhadi Hossainali, Harald Schuh
Summary: Geodetic very long baseline interferometry (VLBI) observations are utilized to study the ionospheric spatial gradient impact on VTEC values, showing a more significant influence in the equatorial region compared to polar areas. The inclusion of ionospheric spatial gradients helps reduce errors in VLBI-derived VTEC values, especially during periods of high solar activity.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2021)
Article
Geochemistry & Geophysics
Saeid Haji-Aghajany, Yazdan Amerian, Sandra Verhagen, Witold Rohm, Harald Schuh
Summary: The paper examines the impact of tropospheric wet delay and tomography methods on positioning accuracy, finding that function-based tomography methods can improve the precision of GPS positioning under different weather conditions.
JOURNAL OF GEODESY
(2021)
Article
Geochemistry & Geophysics
Hany Mahbuby, Yazdan Amerian, Amirhossein Nikoofard, Mehdi Eshagh
Summary: The study uses spherical radial basis functions for gravity anomaly interpolation and solving the fundamental equation of physical geodesy to increase accuracy.
STUDIA GEOPHYSICA ET GEODAETICA
(2021)
Article
Engineering, Aerospace
Hany Mahbuby, Yazdan Amerian
Summary: This study proposes a least-squares parameterization method to model the retrieved VTEC from GPS stations and achieve regional VTEC reconstruction by optimizing the shape parameter. By using global ionospheric maps as background, the modeling difficulties are overcome and accurate regional ionospheric maps are produced. The results show that the proposed method performs well in ionospheric delay estimation and single-frequency positioning accuracy.
ADVANCES IN SPACE RESEARCH
(2022)
Article
Remote Sensing
Elaheh Sadeghi, Masoud Mashhadi Hossainali, Abdolreza Safari
Summary: In voxel-based tropospheric tomography, water vapor is computed for a set of voxels to determine its distribution and changes in the troposphere. This study applies Principal Component Analysis (PCA) to determine the horizontal size of voxels while maintaining the assumption of homogeneity. The results indicate that a 40 km horizontal resolution model has the strongest similarity with the reference model in terms of scattering.
Article
Environmental Sciences
Saeid Haji-Aghajany, Yazdan Amerian, Alireza Amiri-Simkooei
Summary: Precipitation is a significant meteorological indicator that has a direct impact on human health and crucial aspects of life. Scaling methods are required to monitor variations in this parameter at both global and local levels. Research shows that using function-based tropospheric tomography techniques can greatly enhance the accuracy of the scaling process.
Article
Remote Sensing
Masoud Mashhadi Hossainali, Hanieh Tabatabaei
Summary: Although GNSS tropospheric tomography is a powerful tool in meteorology, its accuracy and precision analysis are limited by available validation data. This study uses principal component analysis to study the sensitivity of the tomography model and finds that different parts of the model have different sensitivities to input perturbations. The response of the model to input perturbations is also different when using the virtual reference station (VRS) concept to constrain the model.
Article
Environmental Sciences
Parisa Agar, Shirzad Roohi, Behzad Voosoghi, Arash Amini, Davod Poreh
Summary: Coastal zones pose challenges for satellite altimeters due to the presence of non-water surfaces and calm sea surfaces, which lead to erroneous powers in return waveforms. Selecting an optimized retracker for post-processing waveforms is crucial for accurate water level estimation. Two approaches, waveform decontamination and waveform modification, were introduced to minimize the impact of erroneous powers. The performance of these approaches was evaluated against tidal gauges and compared with external datasets. The results showed that the first meaningful sub-waveform of the decontaminated waveforms had the best performance. The ALES database had worse performance compared to our sub-waveform retracking scenarios.
Article
Environmental Sciences
Mohammad Amin Khalili, Behzad Voosoghi, Luigi Guerriero, Saeid Haji-Aghajany, Domenico Calcaterra, Diego Di Martire
Summary: This paper aims to determine the best interval for interpreting long-term deformation processes and identifying displacement patterns by using three unsupervised clustering algorithms and implementing the advanced integration method for atmospheric phase screen correction. Through the comparison of signals corrected by the AIM and the GPS station, as well as similarity measures and Davies-Bouldin index scores, the SBAS technique with the unsupervised K-medians method has been chosen as the accurate and reliable interval.
Article
Engineering, Aerospace
Hany Mahbuby, Yazdan Amerian
Summary: Retrieved VTEC from dual-frequency GPS measurements is valuable for regional VTEC and IED modeling. However, 4D reconstruction of IED requires additional knowledge of electron density distribution, which is often obtained from global empirical models. Data assimilation, including the optimum interpolation method, plays a key role in IED modeling, especially in regions with sparse observations.
ADVANCES IN SPACE RESEARCH
(2023)
Article
Environmental Sciences
Saeid Haji-Aghajany, Yazdan Amerian, Alireza Amiri-Simkooei
Summary: This study investigates the impact of meteorological indicators on groundwater resources and predicts groundwater levels in regions experiencing drought and subsidence. Precipitation, temperature, evapotranspiration, and precipitable water vapor (PWV) are important parameters for predicting groundwater levels. Two subsidence areas with different weather conditions were selected for a comprehensive study on the influence of temperature and precipitation on groundwater level changes. The exact locations of the areas were determined using Interferometric Synthetic Aperture Radar (InSAR) images and the meteorological parameters were downscaled using statistical models. An Artificial Neural Network (ANN) was used to predict groundwater level changes based on meteorological data, including GPS-based PWV and evapotranspiration index. The results showed a high-performance prediction algorithm and emphasized the importance of including PWV and evapotranspiration in groundwater level predictions.
Article
Geochemistry & Geophysics
Mohammad Amin Khalili, Behzad Voosoghi
Summary: This paper proposes a new Gaussian Radial Basis Functions (GRBF) for the interpolation and differentiation of scattered data in vertical deformation analysis. By comparing different methods in simulated and actual data, it was found that the LGRBF and PGRBF methods significantly improve the surface interpolation accuracy compared to traditional methods.
GEODESY AND GEODYNAMICS
(2021)
Article
Geochemistry & Geophysics
Hany Mahbuby, Yazdan Amerian
Summary: This study presents a data assimilation method for regional ionosphere modeling using observations from dual-frequency Global Navigation Satellite System (GNSS) receivers, showing significant improvements over global ionosphere models. The corrected regional model can be used to enhance the accuracy of single-frequency positioning.
PURE AND APPLIED GEOPHYSICS
(2021)
