Ultra-luminous X-ray sources as super-critical propellers

We study the evolution of newborn neutron stars in high-mass X-ray binaries interacting with a wind-fed super-Eddington disk. The inner disk is regularized to a radiation-dominated quasi-spherical configuration for which we calculate the inner radius of the disk, the total luminosity of the system and the torque acting on the neutron star accordingly, following the evolution of the system through the ejector and early propeller stages. We find that the systems with $B \gtrsim 10^{13}$ G pass through a short ($\sim 20\,{\rm yr}$) ejector stage appearing as supernova impostors followed by a propeller stage lasting $\sim 10^3\,{\rm yr}$. In the super-critical propeller stage the system is still bright ($L\sim 10^{40}\,{\rm erg\, s^{-1}}$) due to the spindown power and therefore appears as an ultra-luminous X-ray source (ULX). The system evolves into pulsating ULX (PULX) when the neutron star spins down to a period ($P\sim 1$ s) allowing for accretion onto its surface to commence. Systems with lower magnetic fields, $B \sim 10^{11}$ G, pass through a long ($10^5\,{\rm yr}$) super-critical propeller stage with luminosities similar to those of the ultra-luminous super-soft sources (ULS), $L \lesssim 10^{40}\,{\rm erg\, s^{-1}}$. The equilibrium periods of these systems in the accretion stage is about $10\,{\rm ms}$, which is much smaller than the typical period range of PULX observed to date. Such systems could have a larger population, but their pulsations would be elusive due to the smaller size of the magnetosphere. Our results suggest that the ULS and some nonpulsating ULX are rapidly spinning and highly magnetized young neutron stars at the super-critical propeller stage.Comment: ApJ in press. 9 pages, 4 figure

The anomalous x-ray pulsar 4U 0142+61: a neutron star with a gaseous fallback disk

The recent detection of the anomalous X-ray pulsar (AXP) 4U 0142+61 in the mid infrared with the Spitzer Observatory (Wang, Chakrabarty & Kaplan 2006) constitutes the first instance for a disk around an AXP. We show, by analyzing earlier optical and near IR data together with the recent data, that the overall broad band data can be reproduced by a single irradiated and viscously heated disk model

Türkiye’de kurumlar vergisinin ekonomik etkileri ve değerlendirilmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Tüzel kişiliğe sahip olan bazı kuruluşların kazançları üzerinden alınan kurumlar vergisi, Birinci Dünya Savaşı'ndan sonra artan kamu harcamalarının finansmanını sağlamak amacıyla gelir vergisinden bağımsız bir şekilde ortaya çıkmış ve gelişme göstermiştir.Kurumlar vergisinin gelir vergisinden ayrı bir uygulama alanı bulması tartışılsa da kurumlar vergisi mükellefi olmanın sağladığı ayrıcalıklar kurumlar vergisinin gelir vergisinden ayrı bir şekilde uygulama alanı bulmasına neden olmuştur. Kurumlar vergisi ilk ortaya çıktığı yıllarda mükelleflerine sağladığı ayrıcalıklardan dolayı tartışılsa da günümüzde bu tartışmalar yerini ülkeler arasındaki ilişkilerin artmasıyla birlikte kurumlar vergisinin nasıl uygulanacağı konusuna bırakmıştır. OECD ülkelerine bakıldığında bu ülkeler yatırımların önünü açıp yeni istihdam alanları yaratmak için kurumlar vergisi oranını yıllar itibariyle düşürme yoluna gitmişlerdir.Kurumlar vergisi alanında dünyada yaşanan gelişmelere paralel olarak Türkiye'de de bazı gelişmeler yaşanmış ve yıllar itibariyle kurumlar vergisi oranları düşmüştür. Kurumlar vergisinin ilk ortaya çıktığı yıllarda oranı %50'lerde iken günümüzde bu oran %20'lere düşürülmüştür. Kurumlar vergisi oranı düştükçe mükelleflerinin ödeyeceği vergi miktarı da azalacağı için kurumlar vergisinin mükellefleri üzerindeki olumsuz etkileri de azalacaktır. Ancak vergi oranı ne kadar düşürülürse düşürülsün kurumlar vergisinin mükellefleri üzerinde bir takım ekonomik etkileri bulunmaktadır. Bu etkiler uygulamada; tasarruf, maliyet, harcama, yatırım, borçlanma alanında yoğunlaşmıştır.Çalışmada, gelir vergisinden ayrı bir uygulama alanı bulan kurumlar vergisi kavramına ve konudaki bazı teorik görüşlere, kurumlar vergisinin bazı OECD ülkelerindeki uygulama biçimlerine, kurumlar vergisinin Türkiye'deki uygulama biçimlerine ve mali fonksiyonlarına değinilerek, kurumlar vergisi uygulamasının mükellefleri üzerindeki ekonomik etkileri ortaya koymak amaçlanmıştır. Kurumlar vergisinin ekonomik etkilerini ortaya koymak amacıyla Sakarya ilini kapsayan bir anket çalışması da yürütülmüştür.Çalışmada mümkün olduğunca kurumlar vergisi uygulamasının ekonomik etkilerini ölçmek ve bu alandaki temel sorunları ortaya koymak amacıyla gerekli görüldüğü ölçüde konulara değinilmiştir. Tez konusuyla ilgili Türkçe literatürde fazla çalışmanın yapılmamış olması ve yapılanların da kurumlar vergisinin ekonomik etkilerini tespit etmeye yönelik olmaması dikkate alındığında çalışmanın önemi literatüre sağlayacağı katkı açısından daha da artmaktadır. Kurumlar vergisinin ekonomik etkilerini ölçmek amacıyla konu ile ilgili eleştirel kaynak incelemesi yapılmış, internet üzerinden yapılan Türkçe ve İngilizce literatür taraması vasıtasıyla elde edilen kaynaklar kullanılarak genel hatlarıyla çalışma ortaya konulmaya çalışılmıştır. Ayrıca yapılan alan araştırması ile çalışma desteklenmiş ve alan araştırmasının bulguları ayrıntılı olarak çalışmaya değerlendirilmiştir.Corporation tax is a tax type receiving from the profit of the corporations which has corporation identity. Corporation tax emerged and improved after First World War to finance the increasing public expenditures.The fact that corporation tax has a different area from income tax caused a discussion among many economists; however corporation tax?s benefits for taxpayers made possible the application of corporate tax as independent sphere from income tax. In those days, the discussion replaced another one, a question which application is the best for the corporation tax. The application of corporation tax has triggered another discussion because it causes same problems such as the justice in tax and decreasing of foreign investments. OECD countries decided to decrease corporate tax rate to get rid of those problems.Those effects can be mostly seen in the area of saving, cost, expense, investment and debt. The discussions mentioned above have occurred in Turkey as well. The most important one among those discussions was decreasing the corporate tax rate. Despite the fact that its rate was %50 when it was applied firstly, today its rate has decreased by %20. Because the most decrease corporate tax rate the most lessen the burden of taxpayers, this new tax rate has got rid of negative effects of corporate tax on taxpayers. However, it is not possible to get rid of all negative effects because corporate tax is a finally tax.In the first chapter of the dissertation, it will be analyzed the concept of corporation tax, its theoretical foundations, historical evolution and its application in same OECD countries. Later, it will be analyzed application types of corporation tax and its historical evolution in Turkey in the second chapter. It will be analyzed the effects of corporation tax on Turkish economy and the behavior of taxpayers and also tested the arguments in the dissertation with the survey realized in Sakarya in the last chapter.In this work, same theoretical arguments will be analyzed to make strong the arguments reached by evaluating the effects of the application and illustrating the main problems resulting from the application. This work?s contribution is also great because there is no important book and article about corporation tax in Turkish literature and also none of them analyze economic effect of this tax type it is. With the aim of determining the effects of corporation tax, it is examined the critical sources, scanned Turkish and English literature in internet. Also, the argument is supported by an area research conducted in Sakarya

Comparison of Alternative Sowing Methods in Hungarian Vetch and Triticale Cultivation in Terms of Yield and Weed Biomass

This study aimed to compare alternative sowing methods i.e., sole, mix and intercrops sown in alternative and perpendicular rows on the productivity of Hungarian vetch-triticale farming. Similarly, the effects of these sowing methods were also inferred on weed infestation. This study was conducted during the vegetation periods of 2018-19 and 2019-20 in terrestrial climate conditions. Sowing in perpendicular rows proved more effective in suppressing weed infestation than alternative rows and increased yield by reducing weed biomass. Sowing Hungarian vetch in mixed and perpendicular rows observed the highest weed infestation and biomass along with low green herbage and dry matter yield. However, Hungarian vetch-triticale mixture (50-50%) sowed in perpendicular rows made the best use of available land, resulted in the lowest weed infestation and biomass and recorded the highest green herbage and dry matter yield. In conclusion, the sowing Hungarian vetch-triticale mixture (50-50%) in perpendicular rows was the most suitable sowing method for improving productivity and suppressing weed infestation in Hungarian vetch-triticale intercropping

A natural limit on the observable periods of anomalous x-ray pulsars and soft gamma-ray repeaters

We investigate the dependence of the evolution of neutron stars with fallback disks on the strength of the magnetic dipole field of the star. Using the same model as employed by Ertan et al. (2009), we obtain model curves for different dipole fields showing that the neutron stars with magnetic dipole fields greater than ∼ 1013 G on the surface of the star are not likely to become anomalous X‐ray pulsars (AXPs) and soft gamma‐ray repeaters (SGRs). Other sources with conventional dipole fields evolve into the AXP phase if their disk can penetrate the light cylinder. The upper limits to the observed periods of AXP and SGRs could be understood if the disk becomes inactive below a low temperature around 100 K. We summarize our present and earlier results indicated by the evolutionary model curves of these sources with an emphasis on the importance of the minimum disk temperature and the X‐ray irradiation in the long‐term evolution of AXPs and SGRs with fallback disks

On fallback disks and magnetars

The discovery of a disk around the anomalous X-ray pulsar 4U 0142+61, has rekindled the interest in fallback disks around magnetars. We briefly review the assumptions of fallback disk models and magnetar models. Earlier data in optical and near IR bands combined with new Spitzer data in the mid-IR range are compatible with a gas disk. Higher multipole fields with magnetar strengths together with a dipole field of 1012-1013 G on the neutron star surface are compatible with the presence of a disk around the neutron star. The possible presence and properties of a fallback disk after the supernova explosion is a likely initial condition to complement the initial rotation period and initial dipole field in determining the evolutionary paths and different types of isolated neutron stars

WAVE FIELD GENERATED BY FINITE-SPAN HYDROFOILS OPERATING BENEATH A FREE SURFACE

The present paper focuses on the numerical investigation of the flow around the fully submerged 2D and 3D hydrofoils operating close to a free surface. Iterative boundary element method is implemented to predict the flow field. This study aims to investigate the aspect ratio effect on the free surface interactions and hydrodynamic performance of the hydrofoils under a free surface by using potential flow theory. Three different submergence depths and aspect ratios are studied in the wide range of Froude Numbers. In 3D cases, spanwise width of the numerical wave tank model is selected both equal and wider to the foil span, to observe the sidewall effects. Wave field seems to be two dimensional at low Froude numbers. On the other hand, signs of three dimensionalities are observed on the free surface structure for higher Fn, even the predicted wave elevations are very close to 2D calculations in the midsection. Increment in the Fn give a rise to the amplitude of the generated waves first, however a further increase in Fn has a lowering effect with the beginning of waves spill in the spanwise direction in the form of Kelvin waves. Free surface proximity and resultant wave field are also seeming to be linked with the lift force on the hydrofoil. As aspect ratio of the foil increase, 3D lift values are getting closer to those of 2D calculations. However, it is seen that, 3D BEM predictions of a hydrofoil under free surface effect cannot be considered two-dimensional even the aspect ratio is equal to 8

Öğretmen Niteliklerinin TIMSS 2011 Fen Başarısına Çok Düzeyli Etkileri

The purpose of this study is to determine the effects of 54 teacher and school characteristics including gender, job satisfaction, self-confidence, professional development, affective characteristics, work conditions, science teaching methods, college that the teacher graduated from and years of experience on Turkish students’ TIMSS 2011 science achievement. Furthermore, it is aimed is to determine the teacher characteristics that best explains the achievement differences that are observed among schools using two-level Hierarchical Linear Modeling (HLM). It is found that participation to professional development programs regarding information technologies and increased school emphasis on academic success as perceived by teachers have statistically significant effects on schools mean science achievements. Similarly, it is found that collaboration among teachers and teachers’ gender have statistically significant effects on schools mean science achievements.Bu çalışmanın amacı, mesleki gelişim, duyuşsal özellikler, çalışma koşulları, fen öğretim yöntemleri, mezun olunan fakülte, cinsiyet, mesleki memnuniyet, özgüven, mesleki deneyim gibi toplamda 54 öğretmen niteliği ve okul özelliğinin Türkiye’deki öğrencilerin TIMSS 2011 fen başarısına etkilerini belirlemektir. İki düzeyli Hiyerarşik Lineer Modelinin (HLM) kullanıldığı bu çalışmada ayrıca okullar arası başarı farkını en çok açıklayan öğretmen niteliklerinin belirlenmesi amaçlanmıştır. Bilgi teknolojileri ile ilgili hizmet içi eğitim programlarına katılımın ve öğretmenlerin okulun akademik başarıya verdiği önem algılarındaki artışın okulların fen başarı ortalamalarına istatistiksel olarak manidar etki ettikleri bulunmuştur. Benzer şekilde öğretmenlerin cinsiyetlerinin ve çalıştıkları okullardaki öğretmenler arası işbirliğinin okulların fen başarı ortalamalarına etkileri istatistiksel olarak manidar bulunmuştur