scholarly journals Dynamical traceback age of the β Pictoris moving group

2020 ◽  
Vol 642 ◽  
pp. A179 ◽  
Author(s):  
N. Miret-Roig ◽  
P. A. B. Galli ◽  
W. Brandner ◽  
H. Bouy ◽  
D. Barrado ◽  
...  
Keyword(s):  
Selection Process ◽  
Sample Selection ◽  
Covariance Matrices ◽  
Radial Velocities ◽  
Velocity Measurements ◽  
Robust Estimate ◽  
New Approach ◽  
Age Dependent ◽  
First Time ◽  
Age Estimates

Context. The β Pictoris moving group is one of the most well-known young associations in the solar neighbourhood and several members are known to host circumstellar discs, planets, and comets. Measuring its age precisely is essential to the study of several astrophysical processes, such as planet formation and disc evolution, which are strongly age-dependent. Aims. We aim to determine a precise and accurate dynamical traceback age for the β Pictoris moving group. Methods. Our sample combines the extremely precise Gaia DR2 astrometry with ground-based radial velocities measured in an homogeneous manner. We use an updated version of our algorithm to determine dynamical ages. The new approach takes into account a robust estimate of the spatial and kinematic covariance matrices of the association to improve the sample selection process and to perform the traceback analysis. Results. We estimate a dynamical age of 18.5−2.4+2.0 Myr for the β Pictoris moving group. We investigated the spatial substructure of the association at the time of birth and we propose the existence of a core of stars that is more concentrated. We also provide precise radial velocity measurements for 81 members of β Pic, including ten stars with the first determinations of their radial velocities. Conclusions. Our dynamical traceback age is three times more precise than previous traceback age estimates and, more importantly, for the first time it reconciles the traceback age with the most recent estimates of other dynamical, lithium depletion boundaries and isochronal ages. This has been possible thanks to the excellent astrometric and spectroscopic precisions, the homogeneity of our sample, and the detailed analysis of binaries and membership.

scholarly journals Multiplicity among solar-type stars

2018 ◽  
Vol 619 ◽  
pp. A81 ◽  
Author(s):  
J.-L. Halbwachs ◽  
M. Mayor ◽  
S. Udry
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Formation Process ◽  
Statistical Properties ◽  
Radial Velocities ◽  
Spectroscopic Binaries ◽  
Orbital Elements ◽  
Velocity Measurements ◽  
Solar Type ◽  
First Time

Context. The statistical properties of binary stars are clues for understanding their formation process. A radial velocity survey was carried on amongst nearby G-type stars and the results were published in 1991. Aims. The survey of radial velocity measurements was extended towards K-type stars. Methods. A sample of 261 K-type stars was observed with the spectrovelocimeter CORAVEL (COrrelation RAdial VELocities). Those stars with a variable radial velocity were detected on the basis of the P(Χ2) test. The orbital elements of the spectroscopic binaries were then derived. Results. The statistical properties of binary stars were derived from these observations and published in 2003. We present the catalogue of the radial velocity measurements obtained with CORAVEL for all the K stars of the survey and the orbital elements derived for 34 spectroscopic systems. In addition, the catalogue contains eight G-type spectroscopic binaries that have received additional measurements since 1991 and for which the orbital elements are revised or derived for the first time.

scholarly journals Extended and Unscented Kalman Filtering Applied to a Flexible-Joint Robot with Jerk Estimation

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Mohammad Ali Badamchizadeh ◽  
Iraj Hassanzadeh ◽  
Mehdi Abedinpour Fallah
Keyword(s):  
Initial Conditions ◽  
Covariance Matrices ◽  
Flexible Joints ◽  
Velocity Measurements ◽  
Lagrange Equations ◽  
Robust Nonlinear Control ◽  
Flexible Joint ◽  
Flexible Joint Robots ◽  
Simulation Results

Robust nonlinear control of flexible-joint robots requires that the link position, velocity, acceleration, and jerk be available. In this paper, we derive the dynamic model of a nonlinear flexible-joint robot based on the governing Euler-Lagrange equations and propose extended and unscented Kalman filters to estimate the link acceleration and jerk from position and velocity measurements. Both observers are designed for the same model and run with the same covariance matrices under the same initial conditions. A five-bar linkage robot with revolute flexible joints is considered as a case study. Simulation results verify the effectiveness of the proposed filters.

A multi-manned assembly line balancing problem with classified teams: a new approach

2016 ◽  
Vol 36 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Hamid Yilmaz ◽  
Mustafa Yilmaz
Keyword(s):  
Design Methodology ◽  
Assembly Line ◽  
Assembly Line Balancing ◽  
Line Balancing ◽  
Test Problems ◽  
New Approach ◽  
Content Type ◽  
Line Test ◽  
Assembly Line Balancing Problem ◽  
First Time

Purpose – Within team-oriented approaches, tasks are assigned to teams before being assigned to workstations as a reality of industry. So it becomes clear, which workers assemble which tasks. Design/methodology/approach – Team numbers of the assembly line can increase with the number of tasks, but at the same time, due to physical situations of the stations, there will be limitations of maximum working team numbers in a station. For this purpose, heuristic assembly line balancing (ALB) procedure is used and mathematical model is developed for the problem. Findings – Well-known assembly line test problems widely used in the literature are solved to indicate the effectiveness and applicability of the proposed approach in practice. Originality/value – This paper draws attention to ALB problem in which workers have been assigned to teams in advance due to the need for specialized skills or equipment on the line for the first time.

A New Approach for the Fabrication of Tetragonal BaTiO3 Nanoparticles

2021 ◽  
Vol 21 (4) ◽  
pp. 2692-2701
Author(s):  
Vu T. Tan ◽  
La The Vinh ◽  
Vu Minh Khoi ◽  
Huynh Dang Chinh ◽  
Pham Van Tuan ◽  
...  
Keyword(s):  
Ferroelectric Properties ◽  
Particle Size Effect ◽  
Ferroelectric Material ◽  
Tem Analysis ◽  
New Approach ◽  
Xrd Pattern ◽  
Munk Function ◽  
Oxide Nanoparticle ◽  
First Time ◽  
Batio3 Nanoparticles

For the first time, the BaTiO3 nano-sized particles were obtained through solid-state reaction by employing the titanium oxide nanoparticle. Meanwhile, by using TiO2 with micro-sized particles, the synthesized BaTiO3 shows the micro-sized. The XRD pattern confirms that both BaTiO3 nano-sized and micro-sized particles display the tetragonal structure. Both SEM and TEM analysis revealed that the size of the nano-sized material is in the range of 30–50 nm; in the meantime, the microsized material shows a size of 500 nm. The Eg of both BaTiO3 micro-sized and nano-sized were calculated by using the Kubelka-Munk function. The shifted bandgap of BaTiO3 nano-sized particle is nearly 0.24 eV larger than that of BaTiO3 miro-sized particle due to the particle size effect. The P-E measurement of n-BaTiO3 proved that the obtained BaTiO3 nano-sized is ferroelectric material. The result may provide a new route for the fabrication of barium titanate nanoparticle with ferroelectric properties.

CHARACTERISTICS OF AGE-DEPENDENT CHANGES IN THE URINE'S PROTEOM COMPOSITION OF THE HEALTHY PERSONS (EXPERIMENTAL AND THEORETICAL STUDY)

2020 ◽  
pp. 735-740
Author(s):  
Л. Х. Пастушкова ◽  
Д. Н. Каширина ◽  
А. Г. Гончарова ◽  
Н. Б. Захарова ◽  
Е. С. Тийс ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Insulin Signaling ◽  
Defense Mechanisms ◽  
Theoretical Study ◽  
Clinical Manifestations ◽  
Age Dependent ◽  
First Time ◽  
Healthy Persons ◽  
Over Time

Впервые описаны белки, достоверно увеличивающиеся и уменьшающиеся в моче с возрастом в интервале 20-60 лет. Охарактеризованы комбинации белков, связанных с изменением иммунных процессов, нарушением реологии крови, в том числе риском коагулопатии, противоопухолевых защитных механизмов, инсулинового сигнального пути, с изменением характеристик клеточного деления и качества новообразованной ткани. Таким образом, возрастная динамика основных процессов запускает каскад реакций, проявляющихся в замыкании «патологических биохимических кругов», которые формируют предпосылки к развитию заболеваний и, с течением времени, клинические проявления. For the first time proteins are described, reliably increasing and decreasing in urine with age in the range of 20 to 60 years. The combinations of proteins associated with changes in immune processes, violation of blood reology, including the risk of coagulopathy, anticancer defense mechanisms, insulin signaling pathway, changes in cell characteristics are characterized division and quality of the newly formed fabric. Thus, the age dynamics of the main processes triggers a cascade of reactions manifested in the closure of «pathological biochemical circles» that form the prerequisites for the development of diseases and, over time, clinical manifestations.

How is the Balance of a Forecast Ensemble Affected by Adaptive and Nonadaptive Localization Schemes?

2015 ◽  
Vol 143 (9) ◽  
pp. 3680-3699 ◽  
Author(s):  
Ross N. Bannister
Keyword(s):  
Forecast Error ◽  
Covariance Matrices ◽  
Error Statistics ◽  
Error Covariance ◽  
Localization Scheme ◽  
Adaptive Schemes ◽  
Convective Scale ◽  
Free Parameters ◽  
Hydrostatic Balance ◽  
First Time

Abstract This paper investigates the effect on balance of a number of Schur product–type localization schemes that have been designed with the primary function of reducing spurious far-field correlations in forecast error statistics. The localization schemes studied comprise a nonadaptive scheme (where the moderation matrix is decomposed in a spectral basis), and two adaptive schemes: a simplified version of Smoothed Ensemble Correlations Raised to a Power (SENCORP) and Ensemble Correlations Raised to a Power (ECO-RAP). The paper shows, the author believes for the first time, how the degree of balance (geostrophic and hydrostatic) implied by the error covariance matrices localized by these schemes can be diagnosed. Here it is considered that an effective localization scheme is one that reduces spurious correlations adequately, but also minimizes disruption of balance (where the “correct” degree of balance or imbalance is assumed to be possessed by the unlocalized ensemble). By varying free parameters that describe each scheme (e.g., the degree of truncation in the schemes that use the spectral basis, the “order” of each scheme, and the degree of ensemble smoothing), it is found that a particular configuration of the ECO-RAP scheme is best suited to the convective-scale system studied. According to the diagnostics this ECO-RAP configuration still weakens geostrophic and hydrostatic balance, but overall this is less so than for other schemes.

scholarly journals Exploiting superspace to clarify vacancy and Al/Si ordering in mullite

IUCrJ ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 497-509 ◽  
Author(s):  
Paul Benjamin Klar ◽  
Iñigo Etxebarria ◽  
Gotzon Madariaga
Keyword(s):  
Density Functional ◽  
X Ray Diffraction ◽  
Intrinsic Structure ◽  
Functional Theory ◽  
New Approach ◽  
X Ray ◽  
Vacancy Ordering ◽  
Harmonic Modulation ◽  
First Time

Synchrotron single-crystal X-ray diffraction has revealed diffuse scattering alongside sharp satellite reflections for different samples of mullite (Al4+2xSi2−2xO10−x). Structural models have been developed in (3+1)-dimensional superspace that account for vacancy ordering and Al/Si ordering based on harmonic modulation functions. A constraint scheme is presented which explains the crystal-chemical relationships between the split sites of the average structure. The modulation amplitudes of the refinements differ significantly by a factor of ∼3, which is explained in terms of different degrees of ordering,i.e.vacancies follow the same ordering principle in all samples but to different extents. A new approach is applied for the first time to determine Al/Si ordering by combining density functional theory with the modulated volumes of the tetrahedra. The presence of Si–Si diclusters indicates that the mineral classification of mullite needs to be reviewed. A description of the crystal structure of mullite must consider both the chemical composition and the degree of ordering. This is of particular importance for applications such as advanced ceramics, because the physical properties depend on the intrinsic structure of mullite.

scholarly journals Elephant Herding Optimization for Energy-Based Localization

2018 ◽  
Author(s):  
Sérgio Correia ◽  
Marko Beko ◽  
Luís Cruz ◽  
Slavisa Tomic
Keyword(s):  
Source Localization ◽  
Wireless Sensors ◽  
Performance Comparison ◽  
Sensor Nodes ◽  
Convex Relaxations ◽  
Noisy Environments ◽  
New Approach ◽  
Metaheuristic Methods ◽  
Simulation Results ◽  
First Time

This work addresses the energy-based source localization problem in wireless sensors networks. Instead of circumventing the maximum likelihood (ML) problem by applying convex relaxations and approximations (like all existing approaches do), we here tackle it directly by the use of metaheuristics. To the best of our knowledge, this is the first time that metaheuristics is applied to this type of problems. More specifically an elephant herding optimization (EHO) algorithm is applied. Through extensive simulations, the key parameters of the EHO algorithm are optimized such that they match the energy decay model between two sensor nodes. A detailed analysis of the computational complexity is presented, as well as performance comparison between the proposed algorithm and existing non-metaheuristic ones. Simulation results show that the new approach significantly outperforms the existing solutions in noisy environments, encouraging further improvement and testing of metaheuristic methods.

scholarly journals Optimal Sampling for the Population Coverage Survey of the New Italian Register Based Census

2021 ◽  
Vol 37 (3) ◽  
pp. 655-671
Author(s):  
Paolo Righi ◽  
Piero Demetrio Falorsi ◽  
Stefano Daddi ◽  
Epifania Fiorello ◽  
Pierpaolo Massoli ◽  
...  
Keyword(s):  
Sampling Design ◽  
Sample Selection ◽  
Sampling Strategy ◽  
Selection Method ◽  
Population Census ◽  
Optimal Sampling ◽  
Population Coverage ◽  
Sample Allocation ◽  
Population Counts ◽  
First Time

Abstract For the first time in 2018 the Italian Institute of Statistics (Istat) implemented the annual Permanent Population Census which relies on the Population Base Register (PBR) and the Population Coverage Survey (PCS). This article provides a general overview of the PCS sampling design, which makes use of the PBR to correct population counts with the extended dual system estimator (Nirel and Glickman 2009). The sample allocation, proven optimal under a set of precision constraints, is based on preliminary estimates of individual probabilities of over-coverage and under-coverage. It defines the expected sample size in terms of individuals, and it oversamples the sub-populations subject to the risk of under/over coverage. Finally, the article introduces a sample selection method, which to the greatest extent possible satisfies the planned allocation of persons in terms of socio-demographic characteristics. Under acceptable assumptions, the article also shows that the sampling strategy enhances the precision of the estimates.

Imperial Impotence: Treason in 1774 Massachusetts

2011 ◽  
Vol 29 (3) ◽  
pp. 657-701
Author(s):  
Neil L. York
Keyword(s):  
Edmund Burke ◽  
Henry Viii ◽  
House Of Commons ◽  
New Approach ◽  
The Subject ◽  
American Policy ◽  
First Time ◽  
The Way

So contended Edmund Burke in the House of Commons, during a May 1770 speech that ridiculed the government's American policy. It was not the first time Burke raised the subject of this 1543 statute. He had asked—rhetorically—during debates two weeks before, “The Act of Henry VIII. Did you mean to execute that?” He then answered his own question, the scorn beneath it probably apparent to all. “You showed your ill will to America, at the same time you dared not execute it.” Burke hoped that by shaming the ministry he might be able to push through a set of resolutions condemning its policies, which could open the way for a new approach to imperial management. He failed, but that did not mean he had been wrong about the futility of threatening to resurrect an old statute to intimidate protesting Americans.

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