M. Yilmazlar

The influence of cooling rates on microstructure and mechanical properties of Bi1,6Pb0,4Sr2Ca2Cu3Oy superconductors

We investigated the effect of cooling rates on the microstructure and mechanical properties of Bi1,6Pb0,4Sr2Ca2Cu3Oy superconductors prepared by standard solid state reaction methods. The samples were annealed under identical condition and cooled with different cooling rates. The investigations consisted of Vickers microhardness, SEM and XRD measurements. XRD examination of the samples showed that high percentage of Bi-2212 phase was observed and low-Tc phase increased with increasing the cooling rates. From SEM analysis, flake-like grains were more pronounced with increasing cooling rates. The indentation load versus diagonal length of the samples under different indentation loads in the range of 0.245-2.940 N were presented. We calculated Vickers hardness, Youngs modulus, yield strength, fracture toughness values. These mechanical properties of the samples were found to be load and cooling rate dependent. In addition, we calculated the load independent microhardness, Youngs modulus, and yield strength and fracture toughness of the samples using different models. The possible reasons for the observed changes in microstructure and mechanical properties of the samples due to cooling rates were discussed.

Fen Bilgisi Öğretiminde Programlı Öğretimin Öğrenci Başarısı ve Tutumu Üzerindeki Etkisi

The purpose of this study is to examine the impact of the method of programmed instruction in teaching science on student achievement and attitude. Pre-test and post-test control group experimental study was carried out in the pattern. The study group is 58 students attending primary school in the sixth grade. Five- week-long course is an experimental science and technology in the experimental group during the processing of transactions processed course the traditional method has been used with the programmed instruction. In the control group lecture, question-and-answer, and practice methods course taught by the application. Force and motion studies were performed to collect data validity and reliability of the achievement test and the attitude scale used in science and technology. Data analysis, independent samples t-test, ANCOVA and related samples t-test was used. Programmed instruction printed course material, used in conjunction with results of the study than the control group significantly enhances student achievement and attitudes. Time students in science teaching force and motion, and similar matters, and class / school environment, regardless of programmed teaching materials are developed and recommended for use.Bu calismanin amaci fen ogretiminde programli ogretim yonteminin ogrenci basarisi ve tutumu uzerindeki etkisini incelemektir. Arastirma on test-son test deney kontrol gruplu deneysel desende yurutulmustur. Calisma grubunu ilkogretim altinci sinifta okuyan 58 ogrenci olusturmaktadir. Bes hafta suren deneysel islemler sirasinda deney grubunda fen ve teknoloji dersinin islenmesinde geleneksel islenen dersle birlikte programli ogretim yontemi kullanilmistir. Kontrol grubunda ise duz anlatim, soru-cevap ve alistirma uygulama yontemleriyle ders islenilmistir. Verilerin toplanmasinda gecerlik ve guvenirlik calismalari yapilmis kuvvet ve hareket konusu basari testi ve fen ve teknoloji tutum olcegi kullanilmistir. Verilerin analizinde iliskisiz orneklemler t testi, ANCOVA ve iliskili orneklemler t-testi uygulanmistir. Arastirma sonuclari dersle birlikte kullanilan programli ogretim basili materyalinin kontrol grubuna gore ogrenci basarisini ve tutumunu anlamli olarak arttirdigini gostermektedir. Fen ogretiminde kuvvet ve hareket ve benzeri konularda ogrencilerin zamandan ve sinif/okul ortamindan bagimsiz olarak kullanabilecekleri programli ogretim materyallerinin gelistirilmesi ve kullanilmasi onerilmektedir.