GR Model Research Articles

A Structural Overview through GR(s) Models Characteristics for Better Yearly Runoff Simulation

In rainfall-runoff modelling, a monthly timescale and an annual one are sufficient for the management of deductions. However, to simulate the flow at a large time-step (annual), we generally precede the use of a model working for a finer time-step (daily) while aggregating the desired outputs. The finest time-steps are considered, apriori, as the most performant. By passing from one time-step to another, and in order to work in the desired time-step (annual) and calculate the potential gains or loss, this article proposed a comparative study between the aggregation method of outputs of a modal working at a finer time step, and a method in which we use a conceived model from the beginning. To ensure this comparative and empirical approach, the choice has been focused on (GRs) models to a daily time-step (GR4J), monthly time step (GR2M) and annual time step (GR1A). The modelling platform used is the same for all three models taking into account the specificities of each one: the same data sample, the same optimization method, and the same function criterion are used during the construction of these models. Due to the moving between these time steps, results show that the best way to simulate the annual flow is to use an appropriate and designed modal initially conceived to this time step. Indeed, this simulation seems to be less effective when using a model at a finer time-step (daily).

The The structure of the Si IV region in Be stars: a study of Si IV spectral lines in Be 68 stars

Using the GR model, we analyze the UV Si IV resonance lines in the spectra of 68 Be stars of different spectral subtypes, in order to detect the structure of Si IV region. We calculated the values of the rotational, radial and random velocities as well as the absorbed energy of each one of the λλ 1393.755, 1402.778 Å Si IV resonance lines and we present the relation between some of these parameters and their variation as a function of the spectral subtype.

Multi-Layer Ionospheric VTEC Estimation for GNSS Positioning

In this paper, the multi-layer ionospheric model based regional VTEC (Vartical Total Electron Content) estimation methods applied by GNSS (Global Navigation Satellite System) Regressive models (abbreviated as GR models) are presented. In the methods, the SCHA (Spherical Cap Harmonic Analysis) as well as the SHF (spherical harmonic functions) are also applied to model the regional VTEC distributions. The ionospheric delays (or advances) over Japan are estimated by using GEONET (Gps Earth Observation NETwork) data provided from the GSI (Geospatial Information Authority of Japan). By applying the ionospheric correction based on the multi-layer model, the positioning accuracy can be improved, and consequently the regional ionosphere can be modeled more accurately by the multi-layer model.

Comparative analysis of a geomorphology‐based instantaneous unit hydrograph in small mountainous watersheds

AbstractA conceptual insytnataneous unit hydrograph (IUH) based on geomorphologival association of linear reservoirs (GR) previously developed by the authors has been compared with other IUH models: a distributed GR variation (GR(v)), the Nash IUH, the Chutha and Dooge IUH, and the Troutman and Karlinger IUH for the analysis of direct runoff hydrographs recorded in three experimental watershed of the north of Spain. The comparison was made through a calibration‐validation process in which a leave‐one‐out cross‐validation method was applied. The results indicate the satisfactory performance of all the models, with the advantage for the GR model of the dependence on only one parameter, which can be identified from the watershed and event characteristics. This property makes its use easier than that of other models. Copyright © 2011 John Wiley & Sons, Ltd.

A Statistical Study of the Si IV Resonance Line Parameters in 19 Be Stars

Abstract Using the GR model, we analyze the ultraviolet Si IV resonance lines in the spectra of 19 Be stars of different spectral subtypes, in order to detect the presence of absorption components and to analyze their characteristics. From this analysis we can calculate the values of a group of physical parameters, such as the apparent rotational and radial velocities, the random velocities of the ion thermal motions, as well as the absorbed energy and the logarithm of the column density of the independent regions of matter which produce the main and the satellite components of the studied spectral lines.

Studying the UV Mg II Resonance Lines in 20 Be Stars

Abstract Using the GR model, we analyze the UV Mg II resonance lines in the spectra of 20 Be stars of different spectral subtypes, in order to detect the presence of satellite or discrete absorption components. The values of some physical parameters – rotational, radial and random velocities, as well as the FWHM and the absorbed energy, as a function of the effective temperature for the studied stars are determined.

What difference does dynamics make? The case of digital cameras

When the well-known BLP model is applied to products with rapid technological changes and declining prices it tends to yield implausible results. A sequence of increasingly sophisticated dynamic demand models, most recently Gowrisankaran and Rysman (2009, hereafter GR), have been developed to overcome these problems. We apply both models to new data on the US digital camera market. In addition, we demonstrate that the GR model can be specified as a BLP model plus an additional set of terms. This suggests that a dynamic model can be estimated as a BLP model plus a non-parametric function which is less computationally demanding. As a first step to implementing this semi-parametric approach we estimate a BLP model augmented with age as a proxy for the non-parametric component. We find that demand for digital cameras is more elastic when demand dynamics is accounted for in both the dynamic model and the BLP model with the age proxy. This suggests that the market is more competitive though the results are consistent with firms engaging in intertemporal price discrimination. Merger simulations predict the lowest price and quantity changes using the GR model.

Effect of Annealing Conditions on Enthalpy Relaxation Parameters of <em>D</em>-Sorbitol Glass

We studied the enthalpy relaxation dynamics of amorphous D-sorbitol by differential scanning calorimetry (DSC). A series of specific heat capacities (Cp(T)) for D-sorbitol were measured upon heating of 10 K·min-1. The samples were subjected to thermal treatment involving isothermal annealing with different annealing time (ta). A new phenomenological model by Gomez Ribelles (the GR model) of enthalpy relaxation based on the evolution of configurational entropy was used to simulate the experimental data to verify the applicability of the GR model to small molecular glass. The results indicated that a single set of GR model parameters only reproduced the corresponding experimental Cp(T) curve of D-sorbitol fairly well. It failed to find a set of GR model parameters as the material constant independent of the thermal history. In contrast with other phenomenological models, some parameters of the GR model remained unchanged. The model parameter sets obtained under longer annealing time show better predictive ability. In contrast to the continuous cooling process for D-sorbitol, the ratio between the mean value of the limit state parameter (δ) and the increment of specific heat capacity at Tg (△Cp(Tg)) apparently increases, but the increase is less than that of polymers. The results brought into question if the metastable limit state introduced by the GR model applied to small molecular glass systems.

Studying the complex BAL profiles in the BALQSOs spectra

Most of Broad Absorption Lines (BALs) in quasars (QSOs) present very complex profiles. This means that we cannot fit them with a known physical distribution. An idea to explain these profiles is that the dynamical systems of Broad Line Regions (BLRs) are not homogeneous but consist of a number of density regions or ion populations with different physical parameters. Each one of these density regions gives us an independent classical absorption line. If the regions that give rise to such lines rotate with large velocities and move radially with small velocities, the produced lines have large widths and small shifts. As a result they are blended among themselves as well as with the main spectral line and thus they are not discrete. Based on this idea we study the BALs of UV C IV resonance lines in the spectra of a group of Hi ionization Broad Absorption Line Quasars (Hi BALQSOs) using the Gauss-Rotation model (GR model).

対流圏水平勾配を考慮した GR モデルに基づく PPP 測位

対流圏水平勾配を考慮した GR モデルに基づく PPP 測位

Ionosphere TEC Estimation of the Sky over Japan Based on Spherical Cap Harmonics

In [1], the authors have developed a method of estimating the local models of an ionosphere VTEC (Vertical Total Electron Content) [2] based on GNSS (global navigation satellite systems) regression models (abbreviated by GR models) and we have shown the ionospheric delay (or advance) in the sky over Japan using the Gps Earth Observation NETwork (GEONET) data provided from the Geographical Survey Institute (GSI) of Japan [3]. In the GNSS positioning, the ionospheric delays are predominant error factors. Therefore, it is important to correct them for higher accurate positioning. In this paper, we present a method of estimating an ionospheric TEC (Total Electron Content) based on GNSS Regression Models. The method of estimating the local models with power series in Spherical Cap Harmonics Expansion (SCHs) [4] for TEC at the ionospheric pierce points in the ionospheric single layer model is discussed.

GPS Positioning Algorithms and Regression Models - Clarifying the Brains of GPS

GNSS (Global Navigation Satellite Systems) Regression (GR) models are shown. Two kinds of GR models for unknown and known positions are derived. The unified methods of point and relative positioning algorithms are shown based on combining GR models. Further, estimation methods of ionosphere total electron content, and orbit and clock errors of GPS satellites are reviewed by applying GR models and measuerement data at the known positions such as GEONET.

General relativistic models of the X-ray spectral variability of MCG–6-30-15

We study in detail the GR models of the X-ray spectral variability for various geometries of the X-ray source and with various relativistic effects being the dominant cause of spectral variability. The predicted properties are compared with the Suzaku observational data of the Seyfert 1 galaxy MCG--6-30-15. The data disfavor models with the X-ray source (1) moving vertically on the symmetry axis or (2) corotating with the disc and changing height not far above the disc surface. The most likely explanation for the observed variability is given by the model involving the X-ray source located at a very small, varying distance from a rapidly rotating black hole. This model predicts some enhanced variations in the red wing of the Fe line, which are not seen in the Suzaku observations. However, the enhanced variability of the red wing, while ruled out by the Suzaku data, is consistent with an excess RMS variability, between 5 and 6 keV, reported for some previous ASCA and XMM observations. We speculate that the presence or lack of such a feature is related to the change of the ionization state of the innermost part of the disc, however, investigation of such effects is currently not possible in our model (where a neutral disc is assumed). If the model, completed by description of ionization effects, proves to be fully consistent with the observational data, it will provide a strong indication that the central black hole in MCG--6-30-15 rotates rapidly, supporting similar conclusions derived from the Fe line profile.

Interpreting the complex line profiles in the stellar spectra

In this review we present our recent investigation of the complex absorption lines in spectra of hot emission stars. The lines are created in a material ejected from stars (here we call it density regions around the objects). Particularly we present a model (GR model) which is developed to study satellite or discrete absorption components (SACs or DACs). Using the model we are able to extract kinematical parameters (rotational, radial and random velocity) and some physical parameters (full width at half maximum, optical depth in the center of the line, column density and absorbed or emitted energy) of the density regions.

Modeling Ionosphere VTEC over Japan Based on GNSS Regression Models and GEONET

In [1-3], we have preliminary developed a method of estimating the local models of an ionosphere VTEC (Vertical Total Electron Content) based on GNSS regression models (abbreviated by GR models) and have shown the ionospheric delay (or advance) in the sky over Japan using the Gps Earth Observation NETwork (GEONET) data provided from the Geographical Survey Institute (GSI) of Japan [4]. In this paper, we try to refine the local models based on the orthogonal polynomials for VTEC at the ionospheric pierce points in the ionospheric single layer model with by comparing with the Taylor series expansion. Furthermore from the aspect of model fitting, we discuss the best number of orthogonal polynomials for the local model of VTEC from informational theoretical points of views such as AIC [5] and BIC [6].

AN INVERSE f(R) GRAVITATION FOR COSMIC SPEED UP, AND DARK ENERGY EQUIVALENT

To explain the cosmic speed up, brought to light by the recent SNIa and CMB observations, we propose the following: (a) In a spacetime endowed with a FRW metric, we choose an empirical scale factor that best explains the observations. (b) We assume a modified gravity, generated by an unspecified field Lagrangian, f(R). (c) We use the adopted empirical scale factor to work back retroactively to obtain f(R), hence the term "Inverse f(R)". (d) Next we consider the classic GR and a conventional FRW universe that, in addition to its known baryonic content, possesses a hypothetical "Dark Energy" component. We compare the two scenarios and find the density, the pressure, and the equation of the state of the Dark Energy required to make up for the differences between the conventional and the modified GR models.

Ionosphere TEC Estimation Based on GR Models at Known Positions

In this paper, we present an ionospheric estimation method based on GNSS Regression models (abbreviated by GR models) and show to derive the ionospheric delay (or advance) local model in the sky over Japan using the Gps Earth Observation NETwork (GEONET) data provided from the Geographical Survey Institute (GSI) of Japan. By showing the GR models for GNSS observables in the case of known positions (in the reference stations), we derive a method to estimate the ionospheric delays (or advances) as well as the so-called integer ambiguities contained in L1 and L2 band carrier-phase data at the reference stations. Then we emphasize the importance to estimate integer ambiguities of their own receivers at the reference stations.

A New GNSS Relative Positioning Algorithm Based on GR Models

In this paper, we derive new relative positioning algorithms based on new GR models (: GNSS Regression models). We have proposed GR models for GNSS navigation such that the precise point positiong algorithms were derived. The derived PPP algorithm achieved a positioning accuracy at the decimeter error level without any external information such as from WAAS. After introducing more precise GR models which contain the so-called receiver's and satellite's hardware delays, we extend our PPP algorithms to relative positioning occasion based on applying the GR equations such that we derive new simple recursive relative positioning algorithms. Finally we show the results of relative positioning for real GPS deta.

Very Precise Point Positioning Based on GR Models

In this paper, we present a new carrier-phase-based precise point positioning (PPP) algorithm based on a new GR model (: GNSS Regression model) by using multiple antennas. Previously we introduced GR equations such that a PPP algorithm was derived which achieved a positioning accuracy at the decimeter error level without any external information such as from WAAS. In this paper, after introducing more precise GR models which contain the so-called receiver's and satellite's hardware biases, we extend our PPP algorithm to the positioning occasion of using multiple antennas. Very precise point positioning (VPPP) algorithms using two or more PPP antennas with common clock errors and known receivers' distances are derived.

Parameter equivalence for the Gardner and van Genuchten soil hydraulic conductivity functions for steady vertical flow with inclusions

The analytic element method is well suited for the Gardner hydraulic conductivity function, but is limited in describing real soils. Therefore, parameter equivalence between the van Genuchten and Gardner hydraulic conductivity functions is explored for the case of steady vertical flow through a homogeneous medium with a single inclusion, i.e., a binary soil. The inclusion has different hydraulic parameters than the background medium. Equivalence is established using three methods: (1) effective capillary drive; (2) capillary length; (3) and a least-squares optimization method that aims to fit a Gardner function to a corresponding van Genuchten function by minimizing the difference in log conductivity over a specified pressure range. Comparisons between hydraulic models are made based on scatterplots of pressure head and the vertical Darcian flux obtained using a finite-element numerical solution with both constitutive relations. For applicability of an equivalent Gardner function over a broad range of pressure heads, the crossover pressure must be maintained between the two parametric functions. The crossover pressure is defined as the pressure in which the hydraulic conductivity of the inclusion is equal to the background. It can be shown that a hybrid methodology of preserving the crossover pressure exactly and using the effective capillary drive will result in hydraulic parameters that are easily obtained and provide good agreement between the conductivity functions of the GR model to the VG model.