Observational and Theoretical Studies of 27 δ Scuti Stars with Investigation of the Period–luminosity Relation

The multi-color CCD photometric study of 27 δ Scuti stars is presented. By using approximately three years of photometric observations, we obtained the times of maxima and magnitude changes during the observation time interval for each star. The ephemerides of our δ Scuti stars were calculated based on the Markov Chain Monte Carlo (MCMC) method using the observed times of maxima and the period of the stars’ oscillations. We used the Gaia EDR3 parallaxes to calculate the luminosities and also the absolute magnitudes of these δ Scuti stars. The fundamental physical parameters of all the stars in our sample such as masses and radii were estimated. We determined the pulsation modes of the stars based on the pulsation constants. Moreover, the period–luminosity (P–L) relation of δ Scuti stars was investigated and discussed. Then, by using a machine learning classification, new P–L relations for fundamental and overtone modes are presented. © 2021. The Astronomical Society of the Pacific. All rights reserved.This work was supported by the Ministry of Science and Education, FEUZ-2020-0030. Popov A.A. acknowledges support by the Ministry of Science and Higher Education of the Russian Federation under the grant 075-15-2020-780. The machine learning section of this study has been performed according to the scientific agreement with Raderon Lab Inc. (https:// raderonlab.ca) with contract number R\AST\2021\1001. The authors would like to appreciate Dr. Fahri Alicavus and Dr. Somayeh Khakpash for their contributions to the research. Also, great thanks to Paul D. Maley for editing the text. The authors would like to thank the reviewer for comments and suggestions that helped to improve the paper

Militant Oil Agitations in Nigeria's Niger Delta and the Economy

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The Rhetoric of Corporate Social Responsibility (CSR) 1 in the Niger Delta

Abstract Petroleum exists as the source of an unholy convergence of interests between th

How a supported metal is influenced by an ionic liquid: In-depth characterization of SCILL-type palladium catalysts and their hydrogen adsorption

A novel approach to tremendously influence the gas adsorption behavior of heterogeneous metal catalysts consists of adding a small quantity of an ionic liquid during the catalyst synthesis yielding a supported catalyst with an ionic liquid layer (SCILL). Herein, SCILL-type catalysts derived from silica-supported palladium were characterized by means of ICP-OES, TPR, X-ray absorption spectroscopy (XANES/EXAFS), X-ray photoelectron spectroscopy (XPS), hydrogen pulse chemisorption, and differential scanning hydrogen adsorption calorimetry. EXAFS analysis of SCILL-type palladium catalysts did not indicate significant changes in the bulk properties of Pd compared to untreated Pd/SiO₂, the results are in good agreement with metallic Pd. XPS analysis revealed a more oxidized Pd surface if Pd/SiO₂ was treated with ionic liquids. In the case of [BMIM][N(CN)₂], Pd(II) species were present in part indicating a complexation of palladium by [N(CN)₂]⁻. Hydrogen uptakes determined by pulse chemisorption varied between 38 and 609 μmol gPd⁻¹ depending on the chosen IL, IL content, and temperature and were decreased in comparison to Pd/SiO₂ without IL. The initial heats of hydrogen adsorption were also affected in the presence of ionic liquids and were lowered compared to those of the untreated Pd/SiO₂. Mechanisms showing how the ionic liquids interact with the active palladium site are proposed and might be in summary interpreted as a ligand effect by the ionic liquid similar to the influence of second metals in bimetallic catalysts

Flexible Architecture for Testing Connected Vehicles in Realistic Traffic

Connected vehicles have the potential to transform the way we commute and travel in a multitude of ways. Vehicles will cooperate and coordinate with each other to solve problems appropriate for the environment in which they are operating. In this paper, we focus on the development of test equipment that includes the infrastructure and vehicles to measure and record all of the information necessary to quantify the performance of cooperative driving algorithms in realistic scenarios. The system allows tests to include real vehicles on the track and virtual vehicles in a digital twin. Real and virtual vehicles interact through the road-side units and test facility network, allowing each test vehicle to receive messages from virtual vehicles as well as the infrastructure. Messages transmitted from the test vehicles are received in the digital twin, allowing the real vehicle to interact with virtual vehicles. This provides the capability to test algorithms in congested traffic without the expense and risk of conducting tests with many cars. The system is shown to allow for real-time operation of connected vehicles in closed loop operation using industry standard networks, along with a protocol for centralized traffic management, which is not currently standardized. Tests have been performed at highway speeds. The architecture has a low barrier to entry application programming interface for its vehicle to infrastructure network that utilizes the Robotic Operating System interface. The paper describes the development and integration of components and protocols, characterization of the network performance, methods for recording data referenced to a single clock, and demonstration of the repeatability of measurements made on test vehicles. The discussion at the end of the paper looks at current research on the impact of cooperative driving algorithms on energy efficiency and traffic flow