scholarly journals Deriving stellar parameters from GALANTE photometry: bias and precision

2020 ◽  
Vol 494 (3) ◽  
pp. 3342-3357
Author(s):  
A Lorenzo-Gutiérrez ◽  
E J Alfaro ◽  
J Maíz Apellániz ◽  
R H Barbá ◽  
A Marín-Franch ◽  
...  
Keyword(s):  
Physical Properties ◽  
Observational Data ◽  
Physical Parameter ◽  
Figure Of Merit ◽  
Physical Parameters ◽  
Detailed Knowledge ◽  
Spectral Library ◽  
Central Wavelength ◽  
Peculiar Behaviour ◽  
Best Fitting

ABSTRACT In this paper, we analyse how to extract the physical properties from the GALANTE photometry of a stellar sample. We propose a direct comparison between the observational colours (photometric bands normalized to the 515 nm central wavelength) and the synthetic colours derived from different stellar libraries. We use the reduced χ2 as the figure of merit for selecting the best fitting between both colour sets. The synthetic colours of the Next Generation Spectral Library (NGSL) provide a valuable sample for testing the uncertainty and precision of the stellar parameters derived from observational data. Reddening, as an extrinsic stellar physical parameter becomes a crucial variable for accounting for the errors and bias in the derived estimates: the higher the reddenings, the larger the errors and uncertainties in the derived parameters. NGSL colours also enable us to compare different theoretical stellar libraries for the same set of physical parameters, where we see how different catalogues of models can provide very different solutions in a, sometimes, non-linear way. This peculiar behaviour makes us to be cautious with the derived physical parameters obtained from GALANTE photometry without previous detailed knowledge of the theoretical libraries used to this end. In addition, we carry out the experiment of deriving physical stellar parameters from some theoretical libraries, using some other libraries as observational data. In particular, we use the Kurucz and Coelho libraries, as input observational data, to derive stellar parameters from Coelho + TLUSTY and Kurucz + TLUSTY stellar libraries, respectively, for different photometric errors and colour excesses.

scholarly journals MEGARA-GTC stellar spectral library: I

2020 ◽  
Vol 493 (1) ◽  
pp. 871-898
Author(s):  
M L García-Vargas ◽  
E Carrasco ◽  
M Mollá ◽  
A Gil de Paz ◽  
S R Berlanas ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Globular Cluster ◽  
Theoretical Models ◽  
High Spectral Resolution ◽  
Physical Parameters ◽  
Spectral Library ◽  
Stellar Spectra ◽  
Open Time ◽  
Minimization Technique ◽  
Best Fitting

ABSTRACT MEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical (3650–9750 Å), fibre-fed, medium-high spectral resolution (R = 6000, 12 000 and 20 000) instrument for the Gran Telescopio CANARIAS (GTC) 10.4-m telescope, commissioned in the summer of 2017, and currently in operation. The scientific exploitation of MEGARA requires a stellar spectra library to interpret galaxy data and to estimate the contribution of the stellar populations. In this paper, we introduce the MEGARA-GTC spectral library, detailing the rationale behind the building of this catalogue. We present the spectra of 97 stars (21 individual stars and 56 members of the globular cluster M15, which are both subsamples taken during the commissioning runs, and 20 stars from our ongoing GTC Open-Time programme). The spectra have R = 20 000 in the HR-R and HR-I set-ups, centred at 6563 and 8633 Å, respectively. We describe the procedures to reduce and analyse the data. Then, we determine the best-fitting theoretical models to each spectrum through a χ2 minimization technique, to derive the stellar physical parameters, and we discuss the results. We have also measured some absorption lines and indices. Finally, we introduce our project to complete the library and the data base in order to make the spectra available to the community.

scholarly journals Analysis of the Physical Properties of Seeds of Selected Viburnum Species for the Needs of Seed Sorting Operations

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 711
Author(s):  
Zdzisław Kaliniewicz ◽  
Dariusz J. Choszcz
Keyword(s):  
Physical Properties ◽  
Ornamental Plants ◽  
Seed Mass ◽  
Terminal Velocity ◽  
Landscape Design ◽  
Physical Parameters ◽  
Regression Analyses ◽  
Uniform Size ◽  
Size Fractions ◽  
Physical Attributes

Viburnum is a genus of colorful and ornamental plants popular in landscape design on account of their high esthetic appeal. The physical properties of viburnum seeds have not been investigated in the literature to date. Therefore, the aim of this study was to characterize the seeds of selected Viburnum species and to search for potential relationships between their physical attributes for the needs of seed sorting operations. The basic physical parameters of the seeds of six Viburnum species were measured, and the relationships between these attributes were determined in correlation and regression analyses. The average values of the evaluated parameters were determined in the following range: terminal velocity—from 5.6 to 7.9 m s−1, thickness—from 1.39 to 1.87 mm, width—from 3.59 to 6.33 mm, length—from 5.58 to 7.44 mm, angle of external friction—from 36.7 to 43.8°, mass—from 16.7 to 35.0 mg. The seeds of V. dasyanthum, V. lentago and V. sargentii should be sorted in air separators, and the seeds of V. lantana and V. opulus should be processed with the use of mesh screens with round apertures to obtain uniform size fractions. The seeds of V. rhytodophyllum cannot be effectively sorted into batches with uniform seed mass, but they can be separated into groups with similar dimensions.

A Method for Identifying Parameters of Mechanical Joints

1990 ◽  
Vol 57 (2) ◽  
pp. 337-342 ◽  
Author(s):  
J. Wang ◽  
P. Sas
Keyword(s):  
Physical Parameter ◽  
Mechanical Systems ◽  
Degree Of Freedom ◽  
Modal Testing ◽  
Physical Parameters ◽  
Mechanical Joints ◽  
Joint Parameters

A method for identifying the physical parameters of joints in mechanical systems is presented. In the method, a multi-d.o.f. (degree-of-freedom) system is transformed into several single d.o.f. systems using selected eigenvectors. With the result from modal testing, each single d.o.f. system is used to solve for a pair of unknown physical parameters. For complicated cases where the exact eigenvector cannot be obtained, it will be proven that a particular physical parameter has a stationary value in the neighborhood of an eigenvector. Therefore, a good approximation for a joint physical parameter can be obtained by using an approximate eigenvector and the exact value for the joint parameters can be reached by carrying out this process in an iterative way.

scholarly journals Understanding Type II Supernovae

2005 ◽  
Vol 192 ◽  
pp. 275-280 ◽  
Author(s):  
L. Zampieri ◽  
M. Ramina ◽  
A. Pastorello
Keyword(s):  
Physical Properties ◽  
Large Range ◽  
Simultaneous Analysis ◽  
Light Curves ◽  
Physical Parameters ◽  
Expansion Velocity ◽  
Type Ii ◽  
Strong Correlations ◽  
Systematic Analysis ◽  
Robust Estimates

SummaryWe present the results of a systematic analysis of a group of Type II plateau supernovae that span a large range in luminosities, from faint objects like SN 1997D and 1999br to very luminous events like SN 1992am. The physical properties of the supernovae appear to be related to the plateau luminosity or the expansion velocity. The simultaneous analysis of the observed light curves, line velocities and continuum temperatures leads us to robust estimates of the physical parameters of the ejected envelope. We find strong correlations among several parameters. The implications of these results regarding the nature of the progenitor, the central remnant and the Ni yield are also addressed.

scholarly journals Study on the Water-Physical Properties of the Cement-Plaster Bonded Rock-Like Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Yong Zhang ◽  
Zhiguo Cao ◽  
Xiaomeng Shi
Keyword(s):  
Physical Properties ◽  
Physical Model ◽  
Coupling Model ◽  
Model Tests ◽  
Physical Parameters ◽  
Test Results ◽  
Physical Model Tests ◽  
Fluid Coupling ◽  
Softening Coefficient ◽  
Solid Fluid Coupling

The cement-plaster bonded rock-like material is one of the most commonly used materials to simulate different rocks in physical model tests. However, the applicability of this material in solid-fluid coupling model tests is not clear because there are few research studies on the water-physical properties of this material and its similarity to the actual rock is uncertain. This paper presents a systemic experimental study on the water-physical properties of the cement-plaster bonded rock-like materials. The parameters of rock-like materials, including water absorption, softening coefficient, and permeability coefficient, were compared with those of actual rocks to analyse the applicability of such material. Then, the influence of proportion on the water-physical properties of this material was discussed. By multiple regression analysis of the test results, empirical equations between the water-physical parameters and proportions were proposed. The equations can be used to estimate the water-physical properties of cement-plaster bonded rock-like materials with specific proportion and thus to select suitable materials in the solid-fluid coupling physical model tests.

Identification of Physical Helicopter Models Using Subspace Identification

2020 ◽  
Vol 65 (2) ◽  
pp. 1-14
Author(s):  
Sevil Avcıoğlu ◽  
Ali Türker Kutay ◽  
Kemal Leblebicioğlu
Keyword(s):  
Parameter Estimation ◽  
State Space ◽  
Nonlinear Optimization ◽  
Physical Parameter ◽  
Test Data ◽  
Flight Test ◽  
The State ◽  
Physical Parameters ◽  
Subspace Identification ◽  
Study Results

Subspace identification is a powerful tool due to its well-understood techniques based on linear algebra (orthogonal projections and intersections of subspaces) and numerical methods like singular value decomposition. However, the state space model matrices, which are obtained from conventional subspace identification algorithms, are not necessarily associated with the physical states. This can be an important deficiency when physical parameter estimation is essential. This holds for the area of helicopter flight dynamics, where physical parameter estimation is mainly conducted for mathematical model improvement, aerodynamic parameter validation, and flight controller tuning. The main objective of this study is to obtain helicopter physical parameters from subspace identification results. To achieve this objective, the subspace identification algorithm is implemented for a multirole combat helicopter using both FLIGHTLAB simulation and real flight-test data. After obtaining state space matrices via subspace identification, constrained nonlinear optimization methodologies are utilized for extracting the physical parameters. The state space matrices are transformed into equivalent physical forms via the "sequential quadratic programming" nonlinear optimization algorithm. The required objective function is generated by summing the square of similarity transformation equations. The constraints are selected with physical insight. Many runs are conducted for randomly selected initial conditions. It can be concluded that all of the significant parameters can be obtained with a high level of accuracy for the data obtained from the linear model. This strongly supports the idea behind this study. Results for the data obtained from the nonlinear model are also evaluated to be satisfactory in the light of statistical error analysis. Results for the real flight-test data are also evaluated to be good for the helicopter modes that are properly excited in the flight tests.

scholarly journals First-Principles Calculations of High-Pressure Physical Properties of Ti0.5Ta0.5 Alloy

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 796
Author(s):  
Fang Yu ◽  
Yu Liu
Keyword(s):  
High Pressure ◽  
Physical Properties ◽  
First Principles ◽  
Theoretical Study ◽  
Applied Pressure ◽  
Lattice Parameter ◽  
Physical Parameters ◽  
First Principles Calculations ◽  
Analysis Method ◽  
Metallic Bond

In this paper, an in-depth theoretical study on some physical properties of Ti0.5Ta0.5 alloy with systematic symmetry under high pressure is conducted via first-principles calculations, and relevant physical parameters are calculated. The results demonstrate that the calculated parameters, including lattice parameter, elastic constants, and elastic moduli, fit well with available theoretical and experimental data when the Ti0.5Ta0.5 alloy is under T = 0 and P = 0 , indicating that the theoretical analysis method can effectively predict the physical properties of the Ti0.5Ta0.5 alloy. The microstructure and macroscopic physical properties of the alloy cannot be destroyed as the applied pressure ranges from 0 to 50GPa, but the phase transition of crystal structure may occur in the Ti0.5Ta0.5 alloy if the applied pressure continues to increase according to the TDOS curves and charge density diagram. The value of Young’s and shear modulus is maximized at P = 25   GPa . The anisotropy factors A ( 100 ) [ 001 ] and A ( 110 ) [ 001 ] are equal to 1, suggesting the Ti0.5Ta0.5 alloy is an isotropic material at 28 GPa, and the metallic bond is strengthened under high pressure. The present results provide helpful insights into the physical properties of Ti0.5Ta0.5 alloy.

scholarly journals Semi-analytic forecasts for JWST – II. Physical properties and scaling relations for galaxies at z = 4–10

2019 ◽  
Vol 490 (2) ◽  
pp. 2855-2879 ◽  
Author(s):  
L Y Aaron Yung ◽  
Rachel S Somerville ◽  
Gergö Popping ◽  
Steven L Finkelstein ◽  
Harry C Ferguson ◽  
...  
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
High Redshift ◽  
Formation Rate ◽  
Distribution Functions ◽  
Scaling Relations ◽  
Physical Parameters ◽  
Model Parameters ◽  
Galaxy Populations ◽  
The Impact

ABSTRACT The long anticipated James Webb Space Telescope (JWST) will be able to directly detect large samples of galaxies at very high redshift. Using the well-established, computationally efficient Santa Cruz semi-analytic model, with recently implemented multiphase gas partitioning, and H2-based star formation recipes, we make predictions for a wide variety of galaxy properties for galaxy populations at z = 4–10. In this work, we provide forecasts for the physical properties of high-redshift galaxies and links to their photometric properties. With physical parameters calibrated only to z ∼ 0 observations, our model predictions are in good agreement with current observational constraints on stellar mass and star formation rate distribution functions up to z ∼ 8. We also provide predictions representing wide, deep, and lensed JWST survey configurations. We study the redshift evolution of key galaxy properties and the scaling relations among them. Taking advantage of our models’ high computational efficiency, we study the impact of systematically varying the model parameters. All distribution functions and scaling relations presented in this work are available at https://www.simonsfoundation.org/semi-analytic-forecasts-for-jwst/.

The Preliminary Results of Rock Physical Properties in Yudu-Ganxian Ore Concentration Area

2013 ◽  
Vol 813 ◽  
pp. 225-229
Author(s):  
Bin Zhao ◽  
Jian Guo Li ◽  
Shao Wei Sun ◽  
Xin Peng Zhou ◽  
Zhen Bin Wang ◽  
...  
Keyword(s):  
Physical Properties ◽  
Research Method ◽  
Three Dimensional ◽  
Physical Property ◽  
Physical Parameters ◽  
Distribution Characteristics ◽  
Actual Distribution ◽  
New Information ◽  
Metallogenic Prognosis ◽  
Rock Physical Property

As the lack of work on comprehensive rock physical properties in deep geophysical exploration in Yudu-Ganxian ore concentration area, this paper focuses in comprehensive and systematic study about the comprehensive rock physical properties in this area. Known from the rock (ore) actual distribution in this area, this paper presents the comprehensive rock physical properties research method of the area, which use varieties of techniques to collect specimens systematic, determine the physical parameters, and even study the distribution characteristics and variation law of rock (ore) integrated rock physical properties parameters. In this paper, the results can provide the new information about integrated rock physical property parameters for understanding and explaining the integrated geophysical anomaly, providing the basis for the future in Nanling to carry out deep geophysical three-dimensional exploration and deep metallogenic prognosis.

scholarly journals How to Make the Physical Parameters Small

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Sergey G. Rubin
Keyword(s):  
Physical Parameter ◽  
Extra Dimensions ◽  
Energy Levels ◽  
The Other ◽  
Physical Parameters ◽  
Green Functions ◽  
Other Hand ◽  
Low Energies ◽  
Parameter Values ◽  
Positive Point

We study the evolution of the physical parameter values defined at the sub-planckian energies to values at low energies. The Wilson action is the basis of the research. The presence of the compact extra dimensions has two consequences. The positive point is that the integration over extra dimensions is a promising way to substantially reduce the parameters to be comparable with the observational values. On the other hand, the discreteness of the energy levels of compact extra dimensions complicates the analysis. This difficulty can be overcome with the truncated Green functions.

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