Cataclysmic Variables as Supernova Ia Progenitors

Kafka, Stella The Korean Space Science Society 2012 Journal of Astronomy and Space Sciences Vol.29 No.2

Although the identification of the progenitors of type Ia supernovae (SNeIa) remains controversial, it is generally accepted that they originate from binary star systems in which at least one component is a carbon-oxygen white dwarf (WD); those systems are grouped under the wide umbrella of cataclysmic variables. Current theories for SNeIa progenitors hold that, either via Roche lobe overflow of the companion or via a wind, the WD accumulates hydrogen or helium rich material which is then burned to C and O onto the WD's surface. However, the specifics of this scenario are far from being understood or defined, allowing for a wealth of theories fighting for attention and a dearth of observations to support them. I discuss the latest attempts to identify and study those controversial SNeIa progenitors. I also introduce the most promising progenitor in hand and I present observational diagnostics that can reveal more members of the category.

Effect of Heat Treatment Conditions and Densities on Residual Stresses at Hybrid (FLN2-4405) P/M Steels

Kafkas Firat,Karatas Cetin,Saritas Suleyman 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

The characteristics of residual stresses occurring in PM steel based nickel (FLN2-4405) was investigated. The measurements of residual stresses were carried out by electrochemical layer removal technique. The values and distributions of residual stresses occurring in PM steel processed under various densities and heat treatment conditions were determined. In most of the experiments, tensile residual stresses were recorded in surface of samples. The residual stress distribution on the surface of the PM steels is affected by the heat treatment conditions and density. Maximum values of residual stresses on the surface were observed sinter hardened condition and density. Minimum level of recorded tensile residual stresses are150 MPa and its maximum level is 370 MPa.

Physicochemical Characteristics and Fatty Acid Composition of Four Papaya Cultivars Grown under Plastic Greenhouse Conditions

Kafkas, Ebru,Gunes, Esma,Gubbuk, Hamide Korean Society of Horticultural Science 2012 원예과학기술지 Vol.30 No.4

Some physicochemical characteristics like nutritional values, sugar content, and fatty acid composition (FAs) in fruits of four papaya (Carica papaya L.) cultivars ('Red Lady', 'Sunrise Solo', 'Tainung', and 'BH-65') grown under plastic greenhouse conditions in the Mediterranean region of Turkey were evaluated. The chemical characteristics, except acidity in the fruits, significantly varied among the cultivars. Nitrogen (N) was the most abundant mineral in all papaya cultivars and ranged from $0.80\;g{\cdot}100\;g^{-1}$ in 'Red Lady' to $1.28\;g{\cdot}100\;g^{-1}$ in 'BH-65' in fresh weight. Potassium (K) and calcium (Ca) were found the highest amount in dry weight. Glucose and fructose were identified as the main sugars in all cultivars. Sucrose was in trace amounts in the three cultivars, but not detectable in cultivar 'Red Lady'. Twenty-five FAs were detected in the papaya fruits. Polyunsaturated fatty acids (PUFAs) were found to be in a highest amounts compared to the saturated fatty acid (SFAs) and monounsaturated fatty acids (MUFAs). Palmitic (C16:0), oleic (C18:1), and linoleic (C18:2n6) acids were the major fatty acids detected in all cultivars. The results of this study implied that dietary intake of papayas may supply substantial nutrient components necessary for human health.

Physicochemical Characteristics and Fatty Acid Composition of Four Papaya Cultivars Grown under Plastic Greenhouse Conditions

Ebru Kafkas,Esma Gunes,Hamide Gubbuk 한국원예학회 2012 원예과학기술지 Vol.30 No.4

Some physicochemical characteristics like nutritional values, sugar content, and fatty acid composition (FAs) in fruits of four papaya (Carica papaya L.) cultivars (‘Red Lady’, ‘Sunrise Solo’, ‘Tainung’, and ‘BH-65’) grown under plastic greenhouse conditions in the Mediterranean region of Turkey were evaluated. The chemical characteristics, except acidity in the fruits, significantly varied among the cultivars. Nitrogen (N) was the most abundant mineral in all papaya cultivars and ranged from 0.80 g·100 g-1in ‘Red Lady’ to 1.28 g·100 g-1 in ‘BH-65’ in fresh weight. Potassium (K) and calcium (Ca) were found the highest amount in dry weight. Glucose and fructose were identified as the main sugars in all cultivars. Sucrose was in trace amounts in the three cultivars, but not detectable in cultivar ‘Red Lady’. Twenty-five FAs were detected in the papaya fruits. Polyunsaturated fatty acids (PUFAs) were found to be in a highest amounts compared to the saturated fatty acid (SFAs) and monounsaturated fatty acids (MUFAs). Palmitic (C16:0), oleic (C18:1), and linoleic (C18:2n6) acids were the major fatty acids detected in all cultivars. The results of this study implied that dietary intake of papayas may supply substantial nutrient components necessary for human health.

Buckling analysis of perforated nano/microbeams with deformable boundary conditions via nonlocal strain gradient elasticity

Ugur Kafkas,Yunus Unal,M. Ozgur Yayli,Busra Uzun Techno-Press 2023 Advances in nano research Vol.15 No.4

This work aims to present a solution for the buckling behavior of perforated nano/microbeams with deformable boundary conditions using nonlocal strain gradient theory (NLSGT). For the first time, a solution that can provide buckling loads based on the non-local and strain gradient effects of perforated nanostructures on an elastic foundation, while taking into account both deformable and rigid boundary conditions. Stokes' transformation and Fourier series are used to realize this aim and determine the buckling loads under various boundary conditions. We employ the NLSGT to account for size-dependent effects and utilize the Winkler model to formulate the elastic foundation. The buckling behavior of the perforated nano/microbeams restrained with lateral springs at both ends is studied for various parameters such as the number of holes, the length and filling ratio of the perforated beam, the internal length, the nonlocal parameter and the dimensionless foundation parameter. Our results indicate that the number of holes and filling ratio significantly affect the buckling response of perforated nano/microbeams. Increasing the filling ratio increases buckling loads, while increasing the number of holes decreases buckling loads. The effects of the non-local and internal length parameters on the buckling behavior of the perforated nano/microbeams are also discussed. These material length parameters have opposite effects on the variation of buckling loads. This study presents an effective eigenvalue solution based on Stokes' transformation and Fourier series of the restrained nano/microbeams under the effects of elastic medium, perforation parameters, deformable boundaries and nonlocal strain gradient elasticity for the first time.

Cataclysmic Variables as Supernova Ia Progenitors

Stella Kafka 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.2

Although the identification of the progenitors of type Ia supernovae (SNeIa) remains controversial, it is generally accepted that they originate from binary star systems in which at least one component is a carbon-oxygen white dwarf (WD); those systems are grouped under the wide umbrella of cataclysmic variables. Current theories for SNeIa progenitors hold that, either via Roche lobe overflow of the companion or via a wind, the WD accumulates hydrogen or helium rich material which is then burned to C and O onto the WD’s surface. However, the specifics of this scenario are far from being understood or defined, allowing for a wealth of theories fighting for attention and a dearth of observations to support them. I discuss the latest attempts to identify and study those controversial SNeIa progenitors. I also introduce the most promising progenitor in hand and I present observational diagnostics that can reveal more members of the category.

[짧은 소설 긴 생각] <율법 앞에서>

프란츠 카프카(Franz Kafka) (주)유레카엠앤비 2021 유레카 Vol.- No.455

RINGS AND MODULES CHARACTERIZED BY OPPOSITES OF FP-INJECTIVITY

Buyukasik, EngIn,Kafkas-DemIrcI, GIzem Korean Mathematical Society 2019 대한수학회보 Vol.56 No.2

Let R be a ring with unity. Given modules $M_R$ and $_RN$, $M_R$ is said to be absolutely $_RN$-pure if $M{\otimes}N{\rightarrow}L{\otimes}N$ is a monomorphism for every extension $L_R$ of $M_R$. For a module $M_R$, the subpurity domain of $M_R$ is defined to be the collection of all modules $_RN$ such that $M_R$ is absolutely $_RN$-pure. Clearly $M_R$ is absolutely $_RF$-pure for every flat module $_RF$, and that $M_R$ is FP-injective if the subpurity domain of M is the entire class of left modules. As an opposite of FP-injective modules, $M_R$ is said to be a test for flatness by subpurity (or t.f.b.s. for short) if its subpurity domain is as small as possible, namely, consisting of exactly the flat left modules. Every ring has a right t.f.b.s. module. $R_R$ is t.f.b.s. and every finitely generated right ideal is finitely presented if and only if R is right semihereditary. A domain R is $Pr{\ddot{u}}fer$ if and only if R is t.f.b.s. The rings whose simple right modules are t.f.b.s. or injective are completely characterized. Some necessary conditions for the rings whose right modules are t.f.b.s. or injective are obtained.

[짧은 소설, 긴 여운] <율법 앞에서> 프란츠 카프카

편집부(편집자),카프카(Franz Kafka) (주)유레카엠앤비 2016 유레카 Vol.- No.394

Rings and modules characterized by opposites of FP-injectivity

Engin Buyukasik,Gizem Kafkas-Demirci 대한수학회 2019 대한수학회보 Vol.56 No.2

Let $R$ be a ring with unity. Given modules $M_R$ and $_RN$, $M_R$ is said to be absolutely $_RN$-pure if $M \otimes N \to L \otimes N$ is a monomorphism for every extension $L_R$ of $M_R$. For a module $M_R$, the subpurity domain of $M_R$ is defined to be the collection of all modules $_RN$ such that $M_R$ is absolutely $_RN$-pure. Clearly $M_R$ is absolutely $_RF$-pure for every flat module $_RF$, and that $M_R$ is FP-injective if the subpurity domain of $M$ is the entire class of left modules. As an opposite of FP-injective modules, $M_R$ is said to be a \emph{test for flatness by subpurity $($or t.f.b.s.~for short$)$} if its subpurity domain is as small as possible, namely, consisting of exactly the flat left modules. Every ring has a right $t.f.b.s.$~module. $R_R$ is t.f.b.s.~and every finitely generated right ideal is finitely presented if and only if $R$ is right semihereditary. A domain $R$ is Pr\"{u}fer if and only if $R$ is t.f.b.s. The rings whose simple right modules are t.f.b.s.~or injective are completely characterized. Some necessary conditions for the rings whose right modules are t.f.b.s.~or injective are obtained.