Gravity model development for TOPEX/POSEIDON: Joint Gravity Models 1 and 2

1994 ◽  
Vol 99 (C12) ◽  
pp. 24421 ◽  
Author(s):  
R. S. Nerem ◽  
F. J. Lerch ◽  
J. A. Marshall ◽  
E. C. Pavlis ◽  
B. H. Putney ◽  
...  
Keyword(s):  
Gravity Model ◽  
Model Development ◽  
Gravity Models

scholarly journals THE GRAVITY MODEL FORMALIZATION FOR THE INTERCITY PASSENGER’S CORRESPONDENCES PARAMETER’S ESTIMATION

2017 ◽  
Vol 16 (5) ◽  
pp. 437-443 ◽  
Author(s):  
C. V. Dolya
Keyword(s):  
Gravity Model ◽  
Transportation System ◽  
Gravity Models ◽  
Gravity Modeling ◽  
Passenger Transport ◽  
Passenger Transportation ◽  
The Given ◽  
Selection Of ◽  
Calibration Coefficients

he paper considers a possibility to apply gravity models for calculation of intercity passenger transport corres- pondences which are implemented with the help of public transport. The Ukraine transportation system has been selected as an object of investigation and this approach extends application possibilities of the obtained results. Calibration coefficients used in calculation of the indicated correspondences are rather important and significant in case of forecasting passenger transport correspondences. Formalization of these factors is necessary for every transportation system if a calculation of pas-senger transport correspondences has been made for it. In this case searching for actual calibration parameters and other coef-ficients as components of gravitational models is a relevant objective of the given paper. Selection of the gravity model va- riant plays rather significant role in solution of this problem. The developed methods for calculation of passenger transport correspondences are proposed for their application in respect of various transport and trip types. The executed research works have made it possible to investigate a process pertaining to providing of services for passenger transportation while using public routes. The obtained characteristics on functioning of the studied system have allowed to assess the possibility for ap-plication of the known methods for calculation of passenger correspondences and analyze the quality of their application. Calibration coefficients have been empirically selected for calculation of the indicated correspondences while using method of gravity modeling. Formalization of previously unexplored parameters of gravity model component provides the possibility to apply the considered approach for calculation of passenger correspondences within the framework of the investigated trans-portion system. This makes it possible to plan and arrange interaction of various transport types and provides new data and knowledge on the studied system.

Randomness in modified general relativity theory: The stochastic f(R) gravity model

2018 ◽  
Vol 96 (11) ◽  
pp. 1173-1177
Author(s):  
Tomer Shushi
Keyword(s):  
Gravity Field ◽  
Gravity Model ◽  
Gravity Models ◽  
Relativity Theory ◽  
Field Equations ◽  
Important Special Case ◽  
Proposed Model ◽  
Stochastic Space ◽  
Wavefunction Collapse ◽  
New Interpretation

We consider a stochastic modification of the f(R) gravity models, and provide its important properties, including the gravity field equations for the model. We show a prediction in which particles are localized by a system of random gravitational potentials. As an important special case, we investigate a gravity model in the presence of a small stochastic space–time perturbation and provide its gravity field equations. Using the proposed model we examine the stochastic quantum mechanics interpretation, and obtain a novel Schrödinger equation with gravitational potential that is based on diffusion in a gravitational field. Furthermore, we provide a new interpretation to the wavefunction collapse. It seems that the stochastic f(R) gravity model causes decoherence of the spatial superposition state of particles.

scholarly journals A fast quadrature-based gravity model for the homogeneous polyhedron

2019 ◽  
Vol 492 (1) ◽  
pp. 420-430
Author(s):  
Jason M Pearl ◽  
Darren L Hitt
Keyword(s):  
Gravitational Field ◽  
Gravity Model ◽  
Approximate Model ◽  
Edge Length ◽  
Gravity Models ◽  
Surface Topology ◽  
Constant Density ◽  
Bulk Properties ◽  
Average Edge Length ◽  
Computationally Expensive

ABSTRACT To date several probes have been sent to explore the Solar system’s asteroids and comets. These bodies are often irregular in shape and to safely navigate probes in their vicinity accurate gravity models are required. For an arbitrarily shaped constant-density body, the gravitational field can be determined from the surface topology and bulk properties. This is achieved by replacing the body’s true geometry with a polyhedron that closely resembles it and for which analytic equations for the gravitational field exist. For some applications however, these equations are too computationally expensive and it can be beneficial to replace them with numerically amenable approximations. In this work, a numerical-quadrature-based model for the gravitational field of a polyhedron consisting of triangular facets is derived. The proposed approximate model is found to be faster than its analytic counterpart. The error of the approximation is found to be negligible for the potential and Laplacian calculations. The approximate model introduces singularities to the surface of the acceleration calculation degrading the solution at altitudes less than the average edge length of the polyhedron.

scholarly journals A new f(R) gravity model and properties of gravitational waves in it

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Dhruba Jyoti Gogoi ◽  
Umananda Dev Goswami
Keyword(s):  
Gravitational Waves ◽  
Gravity Model ◽  
Longitudinal Mode ◽  
Mass Scale ◽  
Gravity Models ◽  
Jordan Frame ◽  
New Model ◽  
Existing Problems ◽  
Pulsar Timing ◽  
New Directions

AbstractIn this paper, we have introduced a new f(R) gravity model as an attempt to have a model with more parametric control, so that the model can be used to explain the existing problems as well as to explore new directions in physics of gravity, by properly constraining it with recent observational data. Here basic aim is to study the properties of Gravitational Waves (GWs) in this new model. In f(R) gravity metric formalism, the model shows the existence of scalar degree of freedom as like other f(R) gravity models. Due to this reason, there is a scalar mode of polarization of GWs present in the theory. This polarization mode exists in a mixed state, of which one is transverse massless breathing mode with non-vanishing trace and the other is massive longitudinal mode. The longitudinal mode being massive, travels at speed less than the usual tensor modes found in General Relativity (GR). Moreover, for a better understanding of the model, we have studied the potential and mass of scalar graviton in both Jordan frame and Einstein frame. This model can pass the solar system tests and can explain primordial and present dark energy. Also, we have put constraints on the model. It is found that the correlation function for the third mode of polarization under certain mass scale predicted by the model agrees well with the recent data of Pulsar Timing Arrays. It seems that this new model would be useful in dealing with different existing issues in the areas of astrophysics and cosmology.

scholarly journals A Gravity-Based Food Flow Model to Identify the Source of Foodborne Disease Outbreaks

2020 ◽  
Vol 17 (2) ◽  
pp. 444 ◽  
Author(s):  
Tim Schlaich ◽  
Abigail L. Horn ◽  
Marcel Fuhrmann ◽  
Hanno Friedrich
Keyword(s):  
Gravity Model ◽  
Food Supply ◽  
Food Item ◽  
Disease Outbreaks ◽  
Gravity Models ◽  
Shopping Behavior ◽  
Foodborne Disease ◽  
Inference Models ◽  
Computational Approaches ◽  
Home Location

Computational traceback methodologies are important tools for investigations of widespread foodborne disease outbreaks as they assist investigators to determine the causative outbreak location and food item. In modeling the entire food supply chain from farm to fork, however, these methodologies have paid little attention to consumer behavior and mobility, instead making the simplifying assumption that consumers shop in the area adjacent to their home location. This paper aims to fill this gap by introducing a gravity-based approach to model food-flows from supermarkets to consumers and demonstrating how models of consumer shopping behavior can be used to improve computational methodologies to infer the source of an outbreak of foodborne disease. To demonstrate our approach, we develop and calibrate a gravity model of German retail shopping behavior at the postal-code level. Modeling results show that on average about 70 percent of all groceries are sourced from non-home zip codes. The value of considering shopping behavior in computational approaches for inferring the source of an outbreak is illustrated through an application example to identify a retail brand source of an outbreak. We demonstrate a significant increase in the accuracy of a network-theoretic source estimator for the outbreak source when the gravity model is included in the food supply network compared with the baseline case when contaminated individuals are assumed to shop only in their home location. Our approach illustrates how gravity models can enrich computational inference models for identifying the source (retail brand, food item, location) of an outbreak of foodborne disease. More broadly, results show how gravity models can contribute to computational approaches to model consumer shopping interactions relating to retail food environments, nutrition, and public health.

New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure

Science ◽  
2014 ◽  
Vol 346 (6205) ◽  
pp. 65-67 ◽  
Author(s):  
David T. Sandwell ◽  
R. Dietmar Müller ◽  
Walter H. F. Smith ◽  
Emmanuel Garcia ◽  
Richard Francis
Keyword(s):  
Gravity Model ◽  
Deep Ocean ◽  
Gravity Models ◽  
Spreading Ridge ◽  
Radar Altimeter ◽  
Tectonic Structures ◽  
Tectonic Processes ◽  
Marine Gravity ◽  
Regional Tectonic ◽  
Slow Spreading

Gravity models are powerful tools for mapping tectonic structures, especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment. We combined new radar altimeter measurements from satellites CryoSat-2 and Jason-1 with existing data to construct a global marine gravity model that is two times more accurate than previous models. We found an extinct spreading ridge in the Gulf of Mexico, a major propagating rift in the South Atlantic Ocean, abyssal hill fabric on slow-spreading ridges, and thousands of previously uncharted seamounts. These discoveries allow us to understand regional tectonic processes and highlight the importance of satellite-derived gravity models as one of the primary tools for the investigation of remote ocean basins.

Some Theoretical Aspects of Destination Choice and Their Relevance to Production-Constrained Gravity Models

1983 ◽  
Vol 15 (8) ◽  
pp. 1121-1132 ◽  
Author(s):  
A S Fotheringham
Keyword(s):  
Spatial Structure ◽  
Gravity Model ◽  
Distance Decay ◽  
Gravity Models ◽  
Destination Choice ◽  
Agglomeration Effects ◽  
Decay Parameters

Aspects of destination choice which concern relationships between destinations are explored in the context of a production-constrained gravity model. It is shown that, if competition exists between destinations or, alternatively, if agglomeration effects are present, the gravity model is misspecified and estimated distance-decay parameters obtained from the model are related to spatial structure.

scholarly journals Influence of the Choice of Lunar Gravity Model on Orbit Determination for Lunar Orbiters

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Young-Rok Kim ◽  
Young-Joo Song ◽  
Jonghee Bae ◽  
Bang-Yeop Kim
Keyword(s):  
Gravity Model ◽  
Orbit Determination ◽  
Selection Effect ◽  
Gravity Models ◽  
Gravity Modeling ◽  
Lunar Gravity ◽  
Deep Space ◽  
Error Covariance ◽  
Level Measurement ◽  
Acquisition Condition

We examine the influence of the lunar gravity model on the orbit determination (OD) of a lunar orbiter operating in a 100 km high, lunar polar orbit. Doppler and sequential range measurements by three Deep Space Network antennas and one Korea Deep Space Antenna were used. For measurement simulation and OD analysis, STK11 and ODTK6 were utilized. GLGM2, LP100K, LP150Q, GRAIL420A, and GRAIL660B were used for investigation of lunar gravity model selection effect. OD results were assessed by position and velocity uncertainties with error covariance and an external orbit comparison using simulated true orbit. The effect of the lunar gravity models on the long-term OD, degree and order level, measurement-acquisition condition, and lunar altitude was investigated. For efficiency verification, computational times for the five lunar gravity models were compared. Results showed that significant improvements to OD accuracy are observed by applying a GRAIL-based model; however, applying a full order and degree gravity modeling is not always the best strategy, owing to the computational burden. Consequently, we consider that OD using GRAIL660B with 70 × 70 degree and order is the most efficient strategy for mission preanalysis. This study provides useful guideline for KPLO OD analysis during nominal mission operation.

scholarly journals Are Economic Distance and Geographic Remoteness Important in Sustainable Trade? Evidence from the Bilateral Trade between China and Kazakhstan

2019 ◽  
Vol 11 (21) ◽  
pp. 6068 ◽  
Author(s):  
Daeheon Choi ◽  
Chune Young Chung ◽  
Jason Young
Keyword(s):  
Gravity Model ◽  
Bilateral Trade ◽  
Gravity Models ◽  
Spatial Effects ◽  
Extended Gravity ◽  
Economic Distance ◽  
Trading Partners ◽  
Geographic Remoteness ◽  
Sustainable Trade ◽  
Unobservable Factors

In this study, we investigate sustainable trade between China and Kazakhstan using the gravity model. We find that the distance between the importer and exporter relative to the distance to other trading partners, rather than the absolute distance, significantly negatively impacts trade volumes. Other factors, such as the structure and availability of free trade zones and unobservable factors related to the characteristics of the checkpoints, also affect trade volumes. To obtain these results, we derive an extended gravity model that considers spatial effects and specific features of the trade between China and Kazakhstan. Thus, we contribute to the fundamental foundations of gravity models.

scholarly journals Globalization and export flows between Eurasian Economic Union countries: a gravity model approach

2020 ◽  
Vol 74 ◽  
pp. 06001
Author(s):  
Juliet Abakumova ◽  
Olena Primierova
Keyword(s):  
Gravity Model ◽  
Positive Impact ◽  
Gravity Models ◽  
Trade Integration ◽  
Transport Costs ◽  
Integration Model ◽  
Time Estimates ◽  
Eurasian Economic Union ◽  
Model Approach

In the empirical tools for the research of trade integration a special place is occupied by gravity models, insofar as these models have rather high accuracy in explaining mutual trade flows. Recently, however, the gravity model approach has been subjected to critical rethinking: globalization brought considerable changes not only in economic growth, but also in international trade, what allowed speaking about a “Death of Distance”. At the same time, estimates based on gravity models almost always demonstrated an increase in the coefficient of distance as a proxy for transport costs, which contradicts the general perception of the phenomenon of globalization. The paper is devoted to testing the validity of inclusion of the globalization index in the model, which would allow consider the role of globalization in bilateral cross-country trade, as well as testing the hypothesis of reducing the coefficient of distance. Based on the annual panel data over the period 2000-2016 the trade integration model for the EEU countries was estimated. To test the hypothesis of a decrease in the estimated coefficient of distance over time, the gravity model was also evaluated at different time intervals. And the positive impact of the globalization factor on the volume of exports is revealed.

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