451 research outputs found
Trajectories of charged particles trapped in Earth's magnetic field
I outline the theory of relativistic charged-particle motion in the
magnetosphere in a way suitable for undergraduate courses. I discuss particle
and guiding center motion, derive the three adiabatic invariants associated
with them, and present particle trajectories in a dipolar field. I provide
twelve computational exercises that can be used as classroom assignments or for
self-study. Two of the exercises, drift-shell bifurcation and Speiser orbits,
are adapted from active magnetospheric research. The Python code provided in
the supplement can be used to replicate the trajectories and can be easily
extended for different field geometries.Comment: 10 pages, 7 figures. Submitted to American Journal of Physic
Numerical Investigation of Dam-Break Flow over a Bottom Obstacle Using Eulerian Finite Element Method
Dam-break flows can cause major destructions in case settlements located atthe downstream area. Since many people live in the settlements, investigations regarding the dam-break flow have great importance.Dam break flow characteristics can become variousbased on different downstream conditions. In this study, an investigation was made relating tothe dam break flow in a channel with symmetrical triangular-shaped bottom obstacle using Finite Element Method (FEM) formulation. Numerical results of the present study were compared with experimental results. It was concluded that numerical and experimental results are in good agreement
Students' Reluctance to Attend Office Hours: Reasons and Suggested Solutions
This paper focuses on investigating students’ reasons for their reluctance to attend faculty members’ office hours. Study participants included 500 male and female students from the Colleges of Engineering (n = 248) and Arts and Social Sciences (CASS) (n = 252) at Sultan Qaboos University (SQU). The study followed a descriptive-analytical approach, and a questionnaire was utilized to collect people’s views. The results of the study indicate that the rates of SQU students’ attendance to office hours were low, and some students (11.2%) do not attend at all as they consider these office hours a waste of time. The main reasons behind the students’ lack of interest in office hours were busy student timetables, conflicts between faculty office hours and students’ timetables, and easier and faster ways of getting information than visiting faculty members. Additional reasons were related to faculty members’ personalities and their discouraging attitudes toward attending office hours. The researchers recommend that SQU adopt a new strategy for encouraging faculty members to hold office hours, familiarizing students with the importance of office hours and assigning part of a course’s grades to meeting with faculty members’ office hours
The temporal analysis of light pollution in Turkey using VIIRS data
© 2021, The Author(s), under exclusive licence to Springer Nature B.V.Artificial Light pollution (AL) in Turkey and in Turkish observatories between 2012–2020 have been studied using the archival data of Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. The astroGIS database has been used in processing the data (astrogis.org) Aksaker et al. (2020a). The total energy released to space from Turkey increased by 80% in 2019 with respect to 2012. In the span of the dataset, a steady and continuous increase has been observed throughout all cities of the country. On the other hand, Dark Sky Park locations, East and Southeast Anatolian regions and mostly rural areas around the cities kept their AL level constant. Four demographic parameters have been studied and they were found to be correlated very well with AL: Population (R≃ 0.90); GDP (R≃ 0.87); Total Power Consumption (R≃ 0.66) and Outdoor Lightening (R≃ 0.67). Contrary to countries acting to prevent AL increases, Turkey seems to be at the beginning of an era where AL will arithmetically increase throughout the country and enormous amount of energy will continuously escape to space and therefore will be wasted. Therefore, a preventive legislation, especially for invaluable astronomical site locations such as TURAG, TUG, DAG and ÇAAM where each is counted as a truly dark site due to their SQM values, has to be enacted in Turkey, in very near future
Citizen Science Time Domain Astronomy with Astro-COLIBRI
Astro-COLIBRI is an innovative tool designed for professional astronomers to
facilitate the study of transient astronomical events. Transient events - such
as supernovae, gamma-ray bursts and stellar mergers - are fleeting cataclysmic
phenomena that can offer profound insights into the most violent processes in
the universe. Revealing their secrets requires rapid and precise observations:
Astro-COLIBRI alerts its users of new transient discoveries from observatories
all over the world in real-time. The platform also provides observers the
details they need to make follow-up observations.
Some of the transient phenomena available through Astro-COLIBRI are
accessible by amateur astronomers and citizen scientists. A subset of the
features dedicated to this growing group of users are highlighted here. They
include the possibility of receiving only alerts on very bright events, the
possibility of defining custom observer locations, as well as the calculation
of optimized observation plans for searches for optical counterparts to
gravitational wave events.Comment: Proceedings Atelier Pro-AM Gemini, Journ\'ees SF2A 2023. arXiv admin
note: text overlap with arXiv:2308.0704
Dynamical analysis of a weakly coupled nonlinear dielectric waveguide -- surface-plasmon model as a new type of Josephson Junction
We propose that a weakly-coupled nonlinear dielectric waveguide --
surface-plasmon system can be formulated as a new type of Josephson junction.
Such a system can be realized along a metal - dielectric interface where the
dielectric medium hosts a nonlinear waveguide (e.g. fiber) for soliton
propagation. We demonstrate that the system is in close analogy to the bosonic
Josephson-Junction (BJJ) of atomic condensates at very low temperatures, yet
exhibits different dynamical features. In particular, the inherently dynamic
coupling parameter between soliton and surface-plasmon generates self-trapped
oscillatory states at nonzero fractional populations with zero and time
averaged phase difference. The salient features of the dynamics are presented
in the phase space.Comment: 9 pages, 7 figure
oxygen K-edge X-ray absorption and emission spectroscopy on micro-jets
Oxygen K-edge X-ray absorption, emission, and resonant inelastic X-ray
scattering spectra were measured to site selectively gain insights into the
electronic structure of aqueous zinc acetate solution. The character of the
acetate ion and the influence of zinc and water on its local electronic
structure are discussed
Parameter estimation for biochemical reaction networks using Wasserstein distances
We present a method for estimating parameters in stochastic models of
biochemical reaction networks by fitting steady-state distributions using
Wasserstein distances. We simulate a reaction network at different parameter
settings and train a Gaussian process to learn the Wasserstein distance between
observations and the simulator output for all parameters. We then use Bayesian
optimization to find parameters minimizing this distance based on the trained
Gaussian process. The effectiveness of our method is demonstrated on the
three-stage model of gene expression and a genetic feedback loop for which
moment-based methods are known to perform poorly. Our method is applicable to
any simulator model of stochastic reaction networks, including Brownian
Dynamics.Comment: 22 pages, 8 figures. Slight modifications/additions to the text;
added new section (Section 4.4) and Appendi
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