21 research outputs found

    Quantum fluctuations in high field magnetization of 2D square lattice J1-J2 antiferromagnets

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    The J1-J2 square lattice Heisenberg model with spin S=1/2 has three phases with long-range magnetic order and two unconventionally ordered phases depending on the ratio of exchange constants. It describes a number of recently found layered vanadium oxide compounds. A simple means of investigating the ground state is the study of the magnetization curve and high-field susceptibility. We discuss these quantities by using the spin-wave theory and the exact diagonalization in the whole J1-J2 plane. We compare both results and find good overall agreement in the sectors of the phase diagram with magnetic order. Close to the disordered regions the magnetization curve shows strong deviations from the classical linear behaviour caused by large quantum fluctuations and spin-wave approximation breaks down. On the FM side (J1<0) where one approaches the quantum gapless spin nematic ground state this region is surprisingly large. We find that inclusion of second order spin-wave corrections does not lead to fundamental improvement. Quantum corrections to the tilting angle of the ordered moments are also calculated. They may have both signs, contrary to the always negative first order quantum corrections to the magnetization. Finally we investigate the effect of the interlayer coupling and find that the quasi-2D picture remains valid up to |J_\perp/J1| ~ 0.3.Comment: 13 pages, 6figure

    Bilayer Manganites

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    Contribution to art education of the university community association (An example of the art for all project)

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    Bu araştırmada, Üniversite Toplum Derneği (ÜTD)' ne bağlı Herkes İçin Sanat projesi altında yürütülen Resim Eğitimi programı incelenerek Üniversite Toplum Derneği' nin sanat eğitimine katkılarının tespit edilmesi amaçlanmıştır. Araştırma, konuyla ilgili kavramsal bilgilerin verilmesinin ardından; Herkes İçin Sanat Projesi Resim Eğitimi programının incelenmesini; görüşmeler, gözlemler, araştırmalar ve öğrenci çalışmalarının değerlendirilmesi sonucunda Üniversite Toplum Derneği' nin sanat eğitimine katkılarına ilişkin elde edilen bulguları ve sonuçları içermektedir. Konu kapsamında; gözlem, görüşme, başarı testi, literatür taraması ve doküman analizi gibi veri toplama tekniklerinin kullanıldığı; durum tespiti yapmaya yönelik betimsel bir yol izlenmiştir. Konuyla ilgili fotoğraflara da araştırmada yer verilmiştir. Herkes İçin Sanat projesindeki Resim Eğitimi etkinliklerinin öğrenciler ve programa katılan gönüllüler açısından yararlı olduğu gözlemlenmiştir. Araştırma sonunda Herkes İçin Sanat projesinin, sanat eğitimi açısından çeşitli sorunların yaşandığı Türkiye'de; önemli ve özgün bir proje olduğu tespit edilmiş ve Türkiye genelinde bu tip projelerin yaygınlaştırılması ve bu alanda çalışan sivil toplum kuruluşlarının desteklenmesi önerilmiştir.In this research, it is aimed to be confirmed of University Community Association's contributions to the Arts Education by analysing the Art Training program which is running under Arts for All Project connected to University Community Association (UTD) in art education. The research, after the conceptual information about the topic has been given, includes the analysis of the Art Training in Arts for All Project; findings and results which are related to the contributions of University Community Association to the Arts Education as a result of thesis meetings, observations and researches. A descritive path directed at conducting case determination using data collection techniques such as observation, interview, achievement test, literature scan, document analysis has been used within the topic. Photographs regarding to the topic have been used in the research. It is observed that the Art Training in Arts for All Project is beneficial to the students and volunteers who are attended the program. As a result of the research it has been determined that the Arts for All is an important and unique project in Turkey where there are problems present regarding the Art Training. It has been proposed to be spread out of this and this kind of projects and support civil organizations working in this field around Turkey
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