Yazar "Demirtaş, Hasan" seçeneğine göre listele

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    6061 alüminyum alaşımlarında ara verilerek yapılan yaşlandırma işleminin malzeme mekanik özelliklerine etkisinin incelenmesi
    (Niğde Üniversitesi, 2009) Demirtaş, Hasan; Alkan, Mahmut
    Alüminyum-Magnezyum-Silisyum (Al-Mg-Si) alaşımları 6XXX serisi alaşımlar olarak da adlandırılmakta olup orta mukavemetli ısıl işlemle mukavemet kazanan malzemelerdir. Şekillendirme kabiliyetleri ve korozyona karşı dayanımları iyidir. Yaygın olarak ekstrüzyon ürünlerinde kullanılırlar. Bu seri içerisinde en yaygın kullanım alanına sahip alaşım ise 6061 alüminyum alaşımıdır.Bu çalışmada, 6061 alüminyum alaşımının ara verilerek yaşlandırma uygulanarak mekanik özelliklerindeki değişim gözlemlenmiş ve bu değerler normal yaşlandırma değerleri ile karşılaştırılmıştır.90 dk. deney şartlarında malzemenin mekanik özelliklerinde önemli ölçüde bir değişim gözlemlenmemiştir. Elde edilen değerler doğrultusunda 20 dk. deney şartlarında toplam uzama miktarlarında %100'e yakın artışlar elde edilmiştir.
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    A validity and reliability study for the school climate scale
    (Ankara University, 2018) Canlı, Suzan; Demirtaş, Hasan; Özer, Niyazi
    The purpose of this study is to develop a valid and reliable school climate scale that is based on the perceptions of the teachers employed in schools. For the purposes of establishing the exploratory and confirmatory factor analyses and test-retest correlations of the scale, the study was conducted on three different study groups. The study groups in question consisted of 264 teachers for the exploratory factor analysis; 242 teachers for the confirmatory factor analysis and 28 teachers for the test-retest correlations. The content and structural validity was reviewed as part of the validity studies. In order to achieve the validity of content, interviews were conducted with school principles and teachers, and the literature was reviewed, and the statements included in the assessment tool were presented to the opinions of experts and teachers. Exploratory and confirmatory factor analyses were conducted for establishing the structural validity. For the reliability study, however, the Cronbach Alpha reliability and item-total correlations were employed for the internal consistency, while the test-retest correlation was used for the internal consistency against time. It was established that the final version of the scale was of five factor structure consisting of a total of 23 items. The compliance index values obtained from confirmatory factor analysis were determined as ? 2 /Sd= 3.080, GFI= .910, AGFI = .886, NNFI (TLI)= .926, CFI = .937, RMSEA = .059, RMR = .057.The values obtained from the confirmatory factor analysis showed that the model-data conformity was at an acceptable level for the scale. As a result of the analyses conducted within the scope of the scale reliability studies, the Cronbach Alpha internal consistency coefficient was calculated as ".908" for the dimension of being democratic and dedicated to the school, as ".897" for the dimension of leadership and interaction, as ".753" for the dimension of success factors, as ".852" of the dimension of sincerity and as ".730" for the dimension of conflict. The test-retest reliability coefficient (Pearson correlation) of the school climate scale was calculated as ".923" for the dimension of being democratic and dedicated to the school, as ".962" for the dimension of leadership and interaction, as ".826" for the dimension of success factors, as ".914" of the dimension of sincerity and as ".946" for the dimension of conflict. The findings obtained as a result of the validity and reliability studies suggest that the scale is a valid and reliable measuring tool that can be used in identifying the perceptions of primary, secondary and high school teachers towards the school climate. © 2019, Ankara University. All rights reserved.