84 results match your criteria: "Institute of Astronomy and Geophysics[Affiliation]"

This paper presents a thorough numerical investigation focused on optimizing the efficiency of quantum-well intermediate-band solar cells (QW-IBSCs) based on III-nitride materials. The optimization strategy encompasses manipulating confinement potential energy, controlling hydrostatic pressure, adjusting compositions, and varying thickness. The built-in electric fields in (In, Ga)N alloys and heavy-hole levels are considered to enhance the results' accuracy.

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This computational investigation delves into the electronic and optical attributes of InGaN/GaN nanostructures subjected to both harmonic and anharmonic confinement potentials, coupled with the influence of a nonresonant intense laser field (ILF). The theoretical framework incorporates higher-order anharmonic terms, specifically quartic and sextic terms. The solutions to the Schrödinger equation have been computed employing the finite element method and the effective mass theory.

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This paper presents a catalog of approximately 1800 Eclipsing W UMa systems (EWs) using parameters from LAMOST, VSX, ZTF and Gaia. Our detailed statistical analysis includes frequency distributions of parameters, confidence intervals, and hypothesis testing to provide deeper insights into the physical properties of this important eclipsing binary class. We focus on key parameters, including Period, Effective Temperature, Surface Gravity, metallicity, Radial Velocity, and spectral type of the systems.

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This work concerned the development of a unique reduced graphene oxide (rGO) nano-filler to provide innovative opportunities in enhancing the thermophysical performance of clay composite bricks. Whereas, a series of clay-rGO composite bricks were produced, doped with various levels of rGO nanosheets (i.e.

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The study aims to assess groundwater resources in Sinai's central area using remote sensing, geoelectric, and well-logging data, utilising techniques for modelling hydrogeological frameworks and evaluating desert regions' groundwater potential. Its utilized satellite image sources, soil maps, and geological maps to map the effects of various factors on groundwater potentiality recharge, dividing it into five zones. Eighteen deep VES stations were used to examine the upper part of the groundwater aquifer in Central Sinai, Egypt, comparing it with available borehole information (Well-1, and JICA-1) to establish subsurface geology and hydro-geology positioning.

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Nowadays, development projects are becoming so rapid in many developing countries worldwide. The study of interest focuses on Cairo-Suez District, which represents the most important location in Egypt for major infrastructure projects and urbanization expansion. Consequently, it is very important to reduce the hazards surrounding this area from natural disasters, so all information that supports geo-environmental hazards assessment is importantly needed.

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UBVRI night sky brightness at Kottamia Astronomical Observatory.

Sci Rep

October 2023

Astronomy, Space Science and Meteorology Department, Faculty of Science, Cairo University, Giza, Egypt.

Photoelectric observations of night sky brightness (NSB) at different zenith distances and azimuths, covering all the sky, at the Egyptian Kottamia Astronomical observatory (KAO) site of coordinates ϕ = 29° 55.9' N and λ = 31° 49.5' E, were done using a fully automated photoelectric photometer (FAPP).

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This work responds to what was reported in various audio-visual media channels and to queries and explanations from individuals and local residents on the causes of gaseous and thermal emissions from the Earth near the vicinity of the village of Al-Hindaw in Dakhla city, New Valley Governorate, Egypt. At the location of the fume exit area, magnetic, seismic, and electromagnetic geophysical investigations were carried out to identify the factor(s) responsible for the event in question. Rock samples were collected and studied geochemically and radiographically to assess their chemical compositions, as well as the quantity of organic chemicals that may have contributed to the burning and temperature increase.

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Analysis of the fractional relativistic polytropic gas sphere.

Sci Rep

August 2023

Department of Astronomy and Meteorology, Faculty of Science, Al-Azhar University, Nasr City, 11889, Cairo, Egypt.

Many stellar configurations, including white dwarfs, neutron stars, black holes, supermassive stars, and star clusters, rely on relativistic effects. The Tolman-Oppenheimer-Volkoff (TOV) equation of the polytropic gas sphere is ultimately a hydrostatic equilibrium equation developed from the general relativity framework. In the modified Riemann Liouville (mRL) frame, we formulate the fractional TOV (FTOV) equations and introduce an analytical solution.

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The Gulf of Aqaba is known for its high seismic activity in Egypt and the Middle East. An inversion technique was applied to 113 earthquakes of magnitude 2.5 to 7.

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Solvothermally Synthesized Hierarchical Aggregates of Anatase TiO Nanoribbons/Nanosheets and Their Photocatalytic-Photocurrent Activities.

Nanomaterials (Basel)

June 2023

Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials (AIIM), University of Wollongong, North Wollongong, NSW 2500, Australia.

Hierarchical aggregates of anatase TiO nanoribbons/nanosheets (TiO-NR) and anatase TiO nanoparticles (TiO-NP) were produced through a one-step solvothermal reaction using acetic acid or ethanol and titanium isopropoxide as solvothermal reaction systems. The crystalline structure, crystalline phase, and morphologies of synthesized materials were characterized using several techniques. According to our findings, both TiO-NR and TiO-NP were found to have polycrystalline structures, with pure anatase phases.

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DFT and QSAR studies of PTFE/ZnO/SiO nanocomposite.

Sci Rep

June 2023

Molecular Spectroscopy and Modeling Unit, Spectroscopy Department, National Research Centre, 33 El-Bohouth St., Dokki, Giza, 12622, Egypt.

Polytetrafluoroethylene (PTFE) is one of the most significant fluoropolymers, and one of the most recent initiatives is to increase its performance by using metal oxides (MOs). Consequently, the surface modifications of PTFE with two metal oxides (MOs), SiO and ZnO, individually and as a mixture of the two MOs, were modeled using density functional theory (DFT). The B3LYPL/LANL2DZ model was used in the studies conducted to follow up the changes in electronic properties.

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Gold mining is an important strategic sector. The search for mineral reserves is moving deeper as more accessible shallow resources are discovered. Geophysical techniques are now being employed more frequently in mineral exploration because they are quick and can provide crucial subsurface information for discovering potential metal deposits, particularly in high-relief and inaccessible places.

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Ultrathin MoO semiconductor nanostructures have garnered significant interest as a promising nanomaterial for transparent nano- and optoelectronics, owing to their exceptional reactivity. Due to the shortage of knowledge about the electronic and optoelectronic properties of MoO/-Si via an ALD system of few nanometers, we utilized the preparation of an ultrathin MoO film at temperatures of 100, 150, 200, and 250 °C. The effect of the depositing temperatures on using bis(tbutylimido)bis(dimethylamino)molybdenum (VI) as a molybdenum source for highly stable UV photodetectors were reported.

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The use of electronic devices that incorporate multilayer ceramic capacitors (MLCCs) is on the rise, requiring materials with good electrical properties and a narrow band gap. This study synthesized yttrium-substituted barium titanate (Ba Y TiO, BYT) using a sol-gel process at 950 °C with varying concentrations of yttrium (0 ≤ ≤ 0.3).

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Tsunamis are commonly generated by earthquakes beneath the ocean floor, volcanic eruptions, and landslides. The tsunami following the Tonga eruption of 2022 is believed to have been excited by atmospheric pressure fluctuations generated by the explosion of the volcano. The first, fast-traveling tsunami was excited by Lamb waves; however, it has not been clarified observationally or theoretically which type of atmospheric fluctuations excited more prominent tsunami which followd.

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Nanostructured MoS and WS Photoresponses under Gas Stimuli.

Nanomaterials (Basel)

October 2022

Department of Physics, Faculty of Science, Islamic University of Madinah, P.O. Box 170, AlMadinah Almonawara 42351, Saudi Arabia.

This study was on the optoelectronic properties of multilayered two-dimensional MoS and WS materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO, and O environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS (n-type)/Si (p-type) and WS (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.

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In this work, orbits of Lorentz spacecrafts and satellites are investigated under the perturbation of solar radiation pressure. An attempt is made to control the perturbation of the solar radiation pressure using the effect of Lorentz force that affects an electrically charged spacecraft. The charge per unit mass is the controlling parameter in this process.

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Nile waterscapes facilitated the construction of the Giza pyramids during the 3rd millennium BCE.

Proc Natl Acad Sci U S A

September 2022

Aix Marseille Université, CNRS, IRD, INRA, Collège de France, CEREGE, 13545 Aix-en-Provence Cedex 04, France.

Article Synopsis
  • The pyramids of Giza were once near a channel of the Nile called the Khufu branch, which allowed boats to transport materials to the Pyramid Harbor complex.
  • Researchers studied pollen patterns to understand the environmental history of the area over the last 8,000 years, revealing how water levels changed.
  • Their findings indicate that while the Nile's water levels were high during the time of the pyramid builders, they gradually decreased due to drying conditions in East Africa, reaching their lowest during the Dynastic Period.
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Urban areas’ pollution, which is owing to rapid urbanization and industrialization, is one of the most critical issues in densely populated cities such as Cairo. The concentrations and the spatial distribution of fourteen potentially toxic elements (PTEs) in household dust were investigated in Cairo City, Egypt. PTE exposure and human health risk were assessed using the USEPA’s exposure model and guidelines.

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Structure of the magma plumbing system beneath Semisopochnoi Island (Aleutian Arc) inferred from seismic tomography.

Sci Rep

June 2022

Chair of Natural Hazards and Mineral Resources, Geology and Geophysics Department, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.

Semisopochnoi Island is a remote and little-studied volcanic island in the western part of the Aleutian Arc. The existence of several active volcanic centers and a 5000-7000-year-old large caldera makes this island an important site for volcanic hazard assessment in the Northern Pacific. Based on local seismicity data recorded by six permanent seismic stations, we created the seismic tomography model, including the 3D distributions of Vp, Vs, and Vp/Vs ratios to a depth of 10 km.

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This paper studied the constraint mechanism for power device design based on perovskite quantum dots pumped by an electron beam. Combined with device designing, an experimental system of self-saturation luminescence and aging failure was designed for CsPbBr films. On this basis, we further completed the self-saturation luminescence and aging failure experiment and constructed a model of self-saturation luminescence and aging failure for CsPbBr device designing.

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Numerical modeling analysis was used to assess the suitable electrical resistivity arrays for the characterization of geological structures, including dyke, horst, graben, sub-vertical, and vertical structures. These geological structures usually make up the aquifers interested in the hydrogeological evaluation of crystalline basement terrains. Six electrode configurations, including Wenner alpha (α), Wenner beta (β), Wenner gamma (γ), Schlumberger array, dipole-dipole array, and pole-dipole array, were used to assess the geological structures for groundwater exploration.

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One- and Two-Sample Predictions Based on Progressively Type-II Censored Carbon Fibres Data Utilizing a Probability Model.

Comput Intell Neurosci

May 2022

Department of Statistics and Operation Research, College of Science, Qassim University, P.O. Box 6644, Buraydah 51482, Saudi Arabia.

New Weibull-Pareto distribution is a significant and practical continuous lifetime distribution, which plays an important role in reliability engineering and analysis of some physical properties of chemical compounds such as polymers and carbon fibres. In this paper, we construct the predictive interval of unobserved units in the same sample (one sample prediction) and the future sample based on the current sample (two-sample prediction). The used samples are generated from new Weibull-Pareto distribution due to a progressive type-II censoring scheme.

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In this applied research work, the risk of rock instability in the Aqabat Al-Sulbat road section located in the north-west area of Aseer Province in Saudi Arabia was evaluated, and the primary natural trigger factors of rock slope instability on further environmental components (rock slope stability, road network, and urban areas) were estimated using satellite images (Landsat8), digital terrain models, and geoprocessing in geographical information systems software (classification, overlapping algorithms and production thematic mapping in Arctoolbox). Additionally, field geotechnical investigations testing and over-coring drilling sampling allowed the characterization of the section of road in terms of geological structure and environmental components (geology, morphology, road network, lineaments, and hydrology). As a result, rock slope instability vulnerability mapping was simulated using satellite imagery and geographical information systems (GIS) and ranking natural trigger factors using the combined fuzzy Delphi analytical hierarchic process with the technique for order performance by similarity to ideal solution (TOPSIS) as multiple-criteria decision-making (MCDM) techniques.

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