scholarly journals Absolute Velocity and Total Stellar Aberration

2018 ◽  
Vol 06 (05) ◽  
pp. 1034-1054
Author(s):  
Miloš Čojanović
2020 ◽  
Vol 17 ◽  
pp. 64-78
Author(s):  
Milos Cojanovic

In this paper, we will show that in addition to measuring annual and diurnal stellar aberration it is also possible 7 directly to measure the angle of secular aberration caused by the motion of the solar system relative to other 8 stars. In the manuscript [1] we dealt with this problem and gave a short description of a special telescope. Using 9 such a telescope we would be able to measure the exact position of the cosmic objects and thus eliminate errors 10 that occur due to the stellar aberration. Assuming that the tube of the telescope is filled with some optical 11 medium [2], we will show that this does not significantly affect the measurement of the stellar aberration angle, 12 but also that these differences are still large enough to enable us to determine the velocity at which the solar 13 system moves relative to the other stars.


2021 ◽  
Vol 11 (12) ◽  
pp. 5727
Author(s):  
Sifat Muin ◽  
Khalid M. Mosalam

Machine learning (ML)-aided structural health monitoring (SHM) can rapidly evaluate the safety and integrity of the aging infrastructure following an earthquake. The conventional damage features used in ML-based SHM methodologies face the curse of dimensionality. This paper introduces low dimensional, namely, cumulative absolute velocity (CAV)-based features, to enable the use of ML for rapid damage assessment. A computer experiment is performed to identify the appropriate features and the ML algorithm using data from a simulated single-degree-of-freedom system. A comparative analysis of five ML models (logistic regression (LR), ordinal logistic regression (OLR), artificial neural networks with 10 and 100 neurons (ANN10 and ANN100), and support vector machines (SVM)) is performed. Two test sets were used where Set-1 originated from the same distribution as the training set and Set-2 came from a different distribution. The results showed that the combination of the CAV and the relative CAV with respect to the linear response, i.e., RCAV, performed the best among the different feature combinations. Among the ML models, OLR showed good generalization capabilities when compared to SVM and ANN models. Subsequently, OLR is successfully applied to assess the damage of two numerical multi-degree of freedom (MDOF) models and an instrumented building with CAV and RCAV as features. For the MDOF models, the damage state was identified with accuracy ranging from 84% to 97% and the damage location was identified with accuracy ranging from 93% to 97.5%. The features and the OLR models successfully captured the damage information for the instrumented structure as well. The proposed methodology is capable of ensuring rapid decision-making and improving community resiliency.


2001 ◽  
Author(s):  
Fredrik Gustafsson ◽  
Stefan Ahlqvist ◽  
Urban Forssell ◽  
Niclas Persson

Author(s):  
Zach Bullock

This study proposes empirical ground motion models for a variety of non-spectral intensity measures and significant durations in New Zealand. Equations are presented for the prediction of the median and maximum rotated components of Arias intensity, cumulative absolute velocity, cumulative absolute velocity above a 5 cm/s2 acceleration threshold, peak incremental ground velocity, and the 5% to 75% and 5% to 95% significant durations. Recent research has highlighted the usefulness of these parameters in both structural and geotechnical engineering. The New Zealand Strong Motion Database provides the database for regression and includes many earthquakes from all regions of New Zealand with the exceptions of Auckland and Northland, Otago and Southland, and Taranaki. The functional forms for the proposed models are selected using cross validation. The possible influence of effects not typically included in ground motion models for these intensity measures is considered, such as hanging wall effects and basin depth effects, as well as altered attenuation in the Taupo Volcanic Zone. The selected functional forms include magnitude and rupture depth scaling, attenuation with distance, and shallow site effects. Finally, the spatial autocorrelation of the models’ within-event residuals is considered and recommendations are made for developing correlated maps of intensity predictions stochastically.


2009 ◽  
Vol 36 (10) ◽  
pp. 2561-2565
Author(s):  
孟婕 Meng Jie ◽  
丁志华 Ding Zhihua ◽  
杨勇 Yang Yong ◽  
王凯 Wang Kai ◽  
李佳纹 Li Jiawen

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