ABSTRACT.During the last decade, learning theories have undergone some considerable changes based on the scientific developments about cognitive processes. In consideration of constructivist learning and process of abstraction, which came up as a result of such developments, this study investigates high schools students' skills of acquiring knowledge of the greatest integer function. It was carried out using the case study method as a group work with two volunteer high school students. In conformity with the principles of constructivist learning, the students were asked to solve three sequential problems which are suitable for observing the actions in abstraction processes and giving students the chance to use their previous experiences and knowledge as much as possible. It was observed that the students used the knowledge they had gained from the first problem to solve the others and they properly acquired the knowledge of piecewise continuous function and the greatest integer function. Another finding is that the use of cases and problems from real life to teach about functions can make a strong contribution to the use of abstraction. SUMMARY Purpose and Significance:This study reports about a teaching experiment done in consideration of the constructivist theory and the process of knowledge construction during that experiment. The subject matter was chosen as "the greatest integer function" and besides the basic principles of constructivism; the conduct of the study was predicated on the perception of mathematics as the knowledge and skills acquired in problem-solving processes based on modelling of reality (De Corte, 2004) and the definition of mathematics as an abstracted form of life. The major aim of the study was to design a learning environment where students can acquire meaningful mathematical knowledge and discover clues that can be used to enhance the quality of teaching throughout the process.

Mindset is the belief of whether people's abilities can be improved or not. It has been an essential phenomenon in education, and the value of this concept cannot be ignored in teachers' educational career. Teachers' mindset plays a pivotal role in learner achievement and building up self-esteem. On the other hand, there has not been much research that examines teachers' mindset and teacher efficacy in instructional strategies. Thus, this study aims to investigate the relationship between in-service teachers' mindset types and their efficacy in instructional strategies. 130 EFL instructors teaching at the English Preparatory Programs from both state and foundation universities in Turkey participated in this research. Teachers' Self-Efficacy Scale (TSES) and Teachers' Mindset Instrument (TMI) were used as data collection tools. TSES and TMS were found to be the most trustable and valid tools to measure teachers' instructional strategies and their mindset. The reliability of the Teacher Mindset Instrument was measured as = .79. The reliability of Teachers' Self-Efficacy Scale was measured as = .86 for efficacy in instructional strategies. Pearson Correlation Analysis and Regression Analysis was conducted to reveal the relationship between teachers' mindset and teacher efficacy in instructional strategies. The results of the study indicate that there is a significant difference between teachers who have a growth mindset and a fixed mindset in terms of using instructional strategies. The teacher efficacy in the instructional strategies is more powerful when the teachers adopt growth mindsets. Researching these two concepts might contribute to teachers' success in the future. Also, this study will shed light on the teacher development programs that universities will offer to their teachers.

Deveci pear (Pyrus communis L. cv. Deveci) slices, whose initial moisture content is 5.24 ± 0.003 kgsu kgKM-1 (%83.95 ± 0.01 w.b), were dried by shade drying and hot-air drying at 60, 80 and 100°C until the final moisture reached 0.13 ± 0.001 kgsu kgKM-1 (%11.40 ± 0.06 w.b), and the drying processes of these methods were completed in 11150, 437, 252, and 148 minutes, respectively. In the study, experimentally obtained time-dependent moisture ratios were modeled using twenty different thin-layer drying equations. Accordingly, the model that gives the closest results to experimental data for 60°C and 100°C was the Modified Henderson & Pabis's equation. On the other hand, Alibas equation and Jena & Das equation were found to be the best models in shade drying and hot-air drying at 80°C, respectively. Despite no energy consumption in the shade drying method, some reasons such as this method being quite long and causing negative effects on the quality parameters of the product revealed that the shade drying method was not suitable for drying of Deveci pear. It was observed that total energy consumption increased with the increase of the drying temperature. Also, it was determined that the increase in temperature negatively affected the quality parameters. It was found to be a suitable method for drying the Deveci pear of the hot-air drying at 60°C due to the operating parameters such as drying time and specific energy consumption, as well as quality parameters such as brightness, redness, yellowness, chroma, hue angle, total color change and browning index were very close to the fresh product.