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Perturbing the Stable Accretion Disk in Kerr and 4D Einstein-Gauss-Bonnet Gravities:Comprehensive Analysis of Instabilities and Dynamics

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Research in Astronomy and Astrophysics 2024年第8期24卷 1-19页

作者： orhan Donmez College of Engineering and Technology American University of the Middle EastEgaila 54200Kuwait

The study of a disturbed accretion disk holds great significance in the realm of astrophysics,as such events play a crucial role in revealing the nature of disk structure,the release of energy,and the generation of shock ***,they can help explain the causes of X-ray emissions observed in black hole accretion disk *** this paper,we perturb the stable disk formed by spherical accretion around Kerr and Einstein-Gauss-Bonnet(EGB)black *** perturbation reveals one-and two-armed spiral shock waves around the black *** find a strong connection between these waves and the black hole spin parameter(a/M)and the EGB coupling constant(α).Specifically,we find that asαincreases in the negative direction,the dynamics of the disk and the waves become more ***,we observe that the angular momentum of the perturbing matter significantly affects mass accretion and the oscillation of the arising shock *** allows us to observe changes in QPO frequencies,particularly,perturbations with angular momentum matching the observed C-type low-frequency QPOs of the GRS 1915+105 ***,we conclude that the possibility of the occurrence of shock waves within the vicinity of GRS 1915+105 is substantial.

关键词： accretion-accretion disks-black hole physics-hydrodynamics-shock waves-X-rays binaries

The changing world under the corona virus threat-from human needs to SDGs and what next?

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Geo-Spatial Information Science 2021年第1期24卷 50-57,I0008页

作者： orhan Altan Ian Dowman Department of Geomatics Istanbul Technical UniversityIstanbulTurkey Department of Civil Environmental and Geomatic EngineeringUniversity College LondonLondonUK

The COVID-19(coronavirus)disease has affected over 100 countries in a matter of *** way humans live and work on planet Earth has changed profoundly over the last *** lives and livelihoods have been *** of working,shopping,and social interactions are all vastly different for most of *** do not know when the current crisis will end,or how far we will“return”to the way things were before the *** world is experiencing one of the most transformative moments of the last 100 *** social,economic,and political influences of the COVID-19 crisis have already been hugely momentous,we do not utterly understand *** ahead,we have inevitably had to make important public health,economic,governance,and ecological decisions with less information than usual and to reverse recently adopted policies,which can lead to an era of disruptive transformations to *** these historic times,we must understand the hidden reality of the earth system and attempt to transform our needs so that we all have a sustained future on our planet.

关键词： COVID-19 human needs social and scientific response millennium development goals sustainable development goals UN

On optimal receiver buffer size in adaptive Internet video streaming

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第z1期7卷 112-118页

作者： ozbek Nukhet TUNALI E.Turhan International Computer Institute Ege University BornovaIzmir 35100Turkey

The effect of receiver buffer size on perceived video quality of an Internet video streamer application was examined in this work. Several network conditions and several versions of the application are used to gain understanding of the response to varying buffer sizes. Among these conditions local area versus wide area, bandwidth estimation based versus non-bandwidth estimation based cases are examined in detail. A total of 1000 min of video is streamed over Intemet and statistics are collected. It was observed that when bandwidth estimation is possible, choosing larger buffer size for higher available bandwidth yields quality increase in perceived video.

关键词： Video streaming, Receiver buffer size

Effect of Doping and High-Temperature Annealing on the Structural and Electrical Properties of Zn_(1-X)Ni_XO(0≤X≤0.15) Powders

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Journal of Materials Science & Technology 2011年第10期27卷 944-950页

作者： Hakan olak orhan Trkoglu Department of Chemistry Faculty of ScienceUniversity of Erciyes

This paper reported the synthesis, crystal structure and electrical conductivity properties of Ni-doped ZnO powders （i.e. Zn1-xNixO binary system, X=0, 0.0025, 0.005, 0.0075 and in the range 0.01≤X〈0.15）. I- phase samples, which were indexed as single phase with a hexagonal （wurtzite） structure in the Zn1-xNixO binary system, were determined by X-ray diffraction （XRD）. The widest range of the I-phase was determined as 0≤X≤0.03 at 1200℃; above this range the mixed phase was observed. The impurity phase was determined as NiO when compared with standard XRD data, using the PDF program. We focused on single f-phase ZnO samples which were synthesized at 1200℃ because of the widest range of solubility limit at this temperature. It was observed that the lattice parameters a and c of the I-phase decreased with Ni doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied by using the four-probe dc method at temperatures between 100 and 950℃ in air atmosphere. The electrical conductivity values of pure ZnO and 3 mol% Ni-doped ZnO samples at 100℃C were 2×10^-6 and 4.8×10^-6 Ω-***^-1, and at 950℃ they were 1.8 and 3.6 Ω-1cm-1, respectively. In other words, electrical conductivity increased with Ni doping concentration.

关键词： Ⅱ-Ⅵ semiconductors Zinc oxide and doped zinc oxide Four point probe method

Synthesis,Crystal Structural and Electrical Conductivity Properties of Fe-Doped Zinc Oxide Powders at High Temperatures

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Journal of Materials Science & Technology 2012年第3期28卷 268-274页

作者： Hakan Çolak orhan TÜrkoglu Department of Chemistry Science of FacultyUniversity of ErciyesKayseri38039Turkey Deparment of Chemistry Science of FacultyUniversity of C ank r KaratekinBall ca CampusC ank r18200Turkey

The synthesis,crystal structure and electrical conductivity properties of Fe-doped ZnO powders（in the range of 0.25-15 mol%） were reported in this paper.I-phase samples,which were indexed as single phase with a hexagonal（wurtzite） structure in the Fe-doped ZnO binary system,were determined by X-ray diffraction（XRD）.The solubility limit of Fe in the ZnO lattice is 3 mol% at 950℃.The above mixed phase was *** the impurity phase was determined as the cubic-ZnFe 2 O 4 phase when compared with standard XRD data using the PDF *** study focused on single I-phase ZnO samples which were synthesized at 950℃ because the limit of the solubility range is the widest at this *** lattice parameters a and c of the I-phase decreased with Fe-doping *** morphology of the I-phase samples was analyzed with a scanning electron *** grain size of the I-phase samples increased with heat treatment and doping *** electrical conductivity of the pure ZnO and single I-phase samples was investigated using the four-probe dc method at 100-950℃ in air *** electrical conductivity values of pure ZnO,0.25 and 3 mol% Fe-doped ZnO samples at 100℃ were 2×10-6,1.7×10-3 and 6.3×10-4 ***-1,and at 950℃ they were 3.4,8.5 and 4 ***-1,respectively.

关键词： II-VI semiconductors Zinc oxide and doped zinc oxide Four point probe method

A review of the day-ahead natural gas consumption in Denmark:starting point towards forecasting accuracy improvement

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International Journal of Coal Science & Technology 2021年第1期8卷 1-22页

作者： orhan AltuğKarabiber George Xydis Department of Business Development and Technology Aarhus UniversityBirk Centerpark 157400HerningDenmark

Natural gas consumption forecasting is crucial for transmission system operators,distribution system operators,traders,and other players in the *** work collects natural gas forecasting scientific works in accordance with the forecasting tool used by Energinet,the Danish transmission system *** work provides an analytical description on the long-term stability and security of the natural gas transmission system in *** work offers a detailed scientific directory on natural gas forecasting,presenting the so far vaguely described market in a more structured *** paper was focused on presenting the latest findings on identifying the selection each time of the appropriate prognostic model for each application based on:①the option for supporting double seasonality,②various exogenous variables,③suitability for day-ahead forecasting,and④ease of use and all these versus Energinet’s current model.

关键词： Natural gas Forecasting Natural gas supply chain Gas infrastructure

A Survey on Belief Propagation Decoding of Polar Codes

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China Communications 2021年第8期18卷 133-168页

作者： Ahmet Cagrı Arlı orhan Gazi Digital Design and Verification Engineering Department Electra ICAnkaraTurkiye Electronic and Communication Engineering Cankaya UniversityAnkaraTurkiye

The increasing data traffic rate of wireless communication systems forces the development of new technologies *** high data rate,extremely low latency and improvement on quality of service are the main subjects of next generation 5G wireless communication systems which will be in the people’s life in the years of *** the newest and first mathematically proven forward error correction code,polar code is one of the best candidates among error correction methods that can be employed for 5G wireless *** aim of this tutorial is to show that belief propagation decoding of polar codes can be a promising forward error correction technique in upcoming 5G ***,we survey the novel approaches to the belief propagation based decoding of polar codes and continue with the studies about the simplification of these ***,early detection and termination methods and concept of scheduling are going to be presented throughout the ***,polar construction algorithms,error types in belief propagation based decoders and hardware implementations are going to be ***,this tutorial proves that the BP based decoding of polar codes has a great potential to be a part of communication standards.

关键词： polar codes belief propagation 5G

Binding energy of the donor impurities in GaAs-Ga_(1-x)Al_xAs quantum well wires with Morse potential in the presence of electric and magnetic fields

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Chinese Physics B 2016年第10期25卷 39-44页

作者： Esra Aciksoz orhan Bayrak Asim Soylu Department of Physics Akdeniz University Department of Physics Nigde University

The behavior of a donor in the GaAs–GaAlAs quantum well wire represented by the Morse potential is examined within the framework of the effective-mass approximation. The donor binding energies are numerically calculated for with and without the electric and magnetic fields in order to show their influence on the binding energies. Moreover, how the donor binding energies change for the constant potential parameters(De, re, and a) as well as with the different values of the electric and magnetic field strengths is determined. It is found that the donor binding energy is highly dependent on the external electric and magnetic fields as well as parameters of the Morse potential.

关键词： Morse potential electric field magnetic field the donor atom quantum well wire

Seasonal size-segregated PM10 and PAH concentrations in a rural area of sugarcane agriculture versus a coastal urban area in Southeastern Florida, USA

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Particuology 2016年第5期14卷 52-59页

作者： orhan Sevimoglu Wolfgang F. Rogge Department of Civil and Environmental Engineering Florida International University 10555 W. Flagier Street Miami FL 33174 USA School of Engineering and Sierra Nevada Research Institute University of California at Merced 5200 North Lake Road Merced CA 95343 USA

Airborne particulate matter （PM） is of health and environmental concern not only in highly urbanized areas, but also in rural areas that are used for intensive agricultural purposes, In this study, PM size- segregated samples were collected simultaneously for 12 months in a small town （Belle Glade, Florida）, which is the center of a vast sugarcane growing area and at Delray Beach, a coastal city in Palm Beach County, Florida. During the winter sampling period, when sugarcane foliage is burned just before harvest- ing to reduce the amount of plant matter to be handled, PM10 levels were 50% or higher than otherwise measured, indicating that sugarcane harvesting and processing is a major local source for PM10. For the rest of the year, PM10 levels at both sites are similar, suggesting that ambient PM levels at both sites are impacted by the major urban centers in Southern Florida. During late July and early August, the PM10 levels at both sites were substantially elevated and revealed the typical red-brownish color of Saharan dust. This has been reported to occur frequently with suitable meteorological conditions over the Atlantic Ocean coupled with a Sahara dust storm event. During the sugarcane harvesting season at Belle Glade, the concentrations of PAHs associated with PM10 were up to 15 times higher than those measured during the summer growing season, indicating a substantially higher exposure of the rural population to these often mutagenic and carcinogenic compounds.

关键词： Size segregated ambient particles PM10 PAHs Biomass burning Rural versus urban Saharan dust