Graphane Nanoribbons: A Theoretical Study

In this study, we investigate the electronic and magnetic properties of graphane nanoribbons. We find that zigzag and armchair graphane nanoribbons with H-passivated edges are nonmagnetic semiconductors. While bare armchair ribbons are also nonmagnetic, adjacent dangling bonds of bare zigzag ribbons have antiferromagnetic ordering at the same edge. Band gaps of the H-passivated zigzag and armchair nanoribbons exponentially depend on their width. Detailed analysis of adsorption of C, O, Si, Pt, Ti, V and Fe atoms on the graphane ribbon surface reveal that functionalization of graphane ribbons is possible via these adatoms. It is found that C, O, V and Pt atoms have tendency to replace H atoms of graphane. We showed that significant spin polarizations in graphane can be achieved through creation of domains of H-vacancies and CH-divacancies.Comment: Accepted for publication in Phys. Rev. B 81, xxxx (2010); http://link.aps.org/doi/10.1103/PhysRevB.81.20541

Magnetization of Graphane by Dehydrogenation

Each single hydrogen vacancy created at the surface of graphane gives rise to a local unpaired spin. For domains of hydrogen vacancies the situation is, however complex and depends on the size and geometry of domains, as well as whether the domains are single- or double-sided. In single-sided domains, hydrogen atoms at the other side are relocated to pair the spins of adjacent carbon atoms by forming pi-bonds. Owing to the different characters of exchange coupling in different ranges and interplay between unpaired spin and the binding geometry of hydrogen, vacancy domains can attain sizable net magnetic moments. Our results based on the first-principles calculations suggest that the size and ordering of magnetic moments of hydrogen vacancy domains with thin walls can be used for future data storage and spintronics applications.Comment: 4 pages, 3 figures (published in Applied Physics Letters

Ortalama-varyans portföy optimizasyonunda genetik algoritma uygulamaları üzerine bir literatür araştırması

Mean-variance portfolio optimization model, introduced by Markowitz, provides a fundamental answer to the problem of portfolio management. This model seeks an efficient frontier with the best trade-offs between two conflicting objectives of maximizing return and minimizing risk. The problem of determining an efficient frontier is known to be NP-hard. Due to the complexity of the problem, genetic algorithms have been widely employed by a growing number of researchers to solve this problem. In this study, a literature review of genetic algorithms implementations on mean-variance portfolio optimization is examined from the recent published literature. Main specifications of the problems studied and the specifications of suggested genetic algorithms have been summarized

The performance of the DC motor by the PID controlling PWM DC-DC boost converter

This paper presents the PID controlling direct current (DC) to the direct current boost converter feds DC motor which has a 3.68 kW and 240 V of DC voltage input on its characteristics. What is first formed is the boost converter mathematical model at the design stage. Secondly, a mathematical model of the DC motor is created so that the boost converter with the machine can be established and modeled at the Matlab Simulink. The PID controller is considered for arranging a pulse width modulation for a boost converter switch because the needed voltage is provided for a DC motor. After that, the PID controlling direct current (DC) to a direct current boost converter running the DC motor is implemented at the Matlab Simulink. In addition to that, the only constant source running the DC motor is simulated at the Matlab Simulink. The DC motor operated by the PID controlling converter that has a low input voltage is compared to the DC motor operated by the high constant DC voltage. A low voltage input converter controlling the DC motor has a high performance according to the high constant DC source running the DC motor

An Overview of Rare and Unusual Clinical Features of Bietti’s Crystalline Dystrophy

Bietti’s crystalline dystrophy (BCD) is a rare disease presenting with the appearance of intraretinal crystalline deposits and varying degrees of chorioretinal atrophy commencing at the posterior pole. Within time, intraretinal crystals gradually disappear and chorioretinal atrophy extends beyond the macula even resulting in complete chorioretinal atrophy. Concomitant corneal crystals can be noted in 1/2 - 1/3 of the patients, and the presence of corneal crystals is not a must for establishing the diagnosis. For the past decade, genetic evaluations and newer imaging modalities expand our knowledge about the disease. CYP4V2 gene is found to be the gene responsible for the disease process and new mutations are still being described. Modern imaging modalities, such as a spectral domain optical coherence tomography (SD-OCT) shed light on the anatomic features of the disease. By this, we reiterate the rare and unusual clinical features of BCD

“When a foreign language learner becomes a foreign language teacher…” – A cross-cultural study into the affective domain of teaching

The aim of this paper is to characterize early experiences of future teachers of English in Polish and Turkish contexts; describe their emotions and attitudes as well as analyze their evaluations of the past situations. When a foreign language learner becomes a foreign language teacher…, firstly s/he has to transform from a FL student to a FL teacher, develop the ability to talk about one’s early experiences and relate them to future growth. In this sense, narrative inquiry largely helps in contextualizing and transforming one’s experience. The data collected for the study involve narratives produced by Turkish and Polish teacher trainees

From Human Trafficking to Human Resources: Acquisition of Victims of Human Exploitation in Terms of Human Resources

Human exploitation is one of the most noncompliant and unacceptable invasion of human rights. Even though generally developed countries are interested in the effects on their own political and economical scheme, actually socio-psychological conditions of victims should be considered regarding the human exploitation. These people who are forced to be in a totally different environment are having a difficulty of integration. Integration and rehabilitation will be effective if applied in all areas with many extensions. In this paper, human exploitation in working places and human resources policies and strategies which would make the integration period shorter for refugee employees