Energy-efficiency for MISO-OFDMA based user-relay assisted cellular networks

The concept of improving energy-efficiency (EE) without sacrificing the service quality has become important nowadays. The combination of orthogonal frequency-division multiple-access (OFDMA) multi-antenna transmission technology and relaying is one of the key technologies to deliver the promise of reliable and high-data-rate coverage in the most cost-effective manner. In this paper, EE is studied for the downlink multiple-input single-output (MISO)-OFDMA based user-relay assisted cellular networks. EE maximization is formulated for decode and forward (DF) relaying scheme with the consideration of both transmit and circuit power consumption as well as the data rate requirements for the mobile users. The quality of-service (QoS)-constrained EE maximization, which is defined for multi-carrier, multi-user, multi-relay and multi-antenna networks, is a non-convex and combinatorial problem so it is hard to tackle. To solve this difficult problem, a radio resource management (RRM) algorithm that solves the subcarrier allocation, mode selection and power allocation separately is proposed. The efficiency of the proposed algorithm is demonstrated by numerical results for different system parameter

A DIFFERENT APPROACH TO THE SCIENTIFIC RESEARCH METHODS COURSE: EFFECTS OF A SMALL-SCALE RESEARCH PROJECT ON PRE-SERVICE TEACHERS

Selecting and applying appropriate research techniques, analysing data using information and communication technologies, transferring the obtained results of the analysis into tables and interpreting them are the performance indicators evaluated by the Ministry of National Education under teacher competencies. At the beginning of the courses that can meet pre-service teachers’ needs of these knowledge and skills, there is undoubtedly the course of scientific research methods. The scientific research methods course (SRMC) has an important mission in the upbringing of tomorrow's researcher pre-service teachers. However, this mission is not possible by considering only theoretical knowledge. At this point, practical-based the research project gains importance. The purpose of this study was to reveal the thoughts of pre-service teachers about a small-scale research project (SSRP) in the scope of a SRMC. The study was carried out with 61 pre-service teachers from the faculty of education of a state university in the north of Turkey. 32 of them were from the department of primary mathematics education and 29 studied in the department of Turkish language education. A five-point Likert-type questionnaire was administered and the participants’ responses were evaluated by means of a software for quantitative analysis. The results of the study revealed that doing a SSRP had many positive effects on the pre-service teachers. Indeed, the SSRP provided them the opportunity to transform the theoretical content of course into practice, to understand the nature of scientific research and respect for them, and to gain the courage to do scientific research and to pursue graduate education.  Article visualizations

Iterative channel estimation techniques for multiple input multiple output orthogonal frequency division multiplexing systems

Thesis (Master)--Izmir Institute of Technology, Electronics and Communication Engineering, Izmir, 2007Includes bibliographical references (leaves: 77-78)Text in English; Abstract: Turkish and Englishxii, 78 leavesOrthogonal frequency division multiplexing (OFDM) is well-known for its efficient high speed transmission and robustness to frequency-selective fading channels. On the other hand, multiple-input multiple-output (MIMO) antenna systems have the ability to increase capacity and reliability of a wireless communication system compared to single-input single-output (SISO) systems. Hence, the integration of the two technologies has the potential to meet the ever growing demands of future communication systems. In these systems, channel estimation is very crucial to demodulate the data coherently. For a good channel estimation, spectral efficiency and lower computational complexity are two important points to be considered. In this thesis, we explore different channel estimation techniques in order to improve estimation performance by increasing the bandwidth efficiency and reducing the computational complexity for both SISO-OFDM and MIMO-OFDM systems. We first investigate pilot and Expectation-Maximization (EM)-based channel estimation techniques and compare their performances. Next, we explore different pilot arrangements by reducing the number of pilot symbols in one OFDM frame to improve bandwidth efficiency. We obtain the bit error rate and the channel estimation performance for these pilot arrangements. Then, in order to decrase the computational complexity, we propose an iterative channel estimation technique, which establishes a link between the decision block and channel estimation block using virtual subcarriers. We compare this proposed technique with EM-based channel estimation in terms of performance and complexity. These channel estimation techniques are also applied to STBC-OFDM and V-BLAST structured MIMO-OFDM systems. Finally, we investigate a joint EM-based channel estimation and signal detection technique for V-BLAST OFDM system

PUBLIC PERSONNEL SELECTION EXAMINATION USED IN TEACHER APPOINTMENTS IN TURKEY: THROUGH THE EYES OF PRIMARY SCHOOL PROSPECTIVE TEACHERS

In recent years, some factors such as the number of graduates from the faculties of education is more than that of the positions declared by Ministry of National Education (MoNE); appointment in some branches is limited; candidates should get high scores from the Public Personnel Selection Examination (PPSE, it is known “KPSS” in Turkish) to be appointed, cause increasing prospective teachers’ anxieties and make the PPSE as a hyper important exam. The aim of this study is to examine primary school prospective teachers’ perspectives of the PPSE. The research group involved 108 prospective teachers in the last year of the department of primary school education at a public university in the north of Turkey. There were 78 females and 30 males. Data for this study was collected via a questionnaire in which the items were measured using a five-point Likert-type scale. An exploratory factor analysis was used to convert the numerous variables into limited number of meaningful and independent factors. At the end of this analysis, seven factors were determined. The data collected for the research were analysed with the help of a quantitative software. The arithmetic mean values of the items were calculated and used in the comments. The significant results of the study revealed that the anxiety about not being able to be appointed as a teacher was an important psychological pressure on the prospective teachers. In this context, the lower rate of appointment to a teaching post, the idea of failure in the PPSE, the high sense of responsibility towards their family negatively affected them in the preparation process to the PPSE.   Article visualizations

DETERMINATION OF UNIVERSITY STUDENTS' METAPHORICAL PERCEPTIONS ABOUT THE CONCEPT OF CLIMATE CHANGE

This study aims to reveal the metaphor that Turkish university students have about the concept of "climate change". The research was carried out with the students at Necmettin Erbakan University, Ahmet Keleşoğlu Faculty of Education (Geography 17, Biology 26, History 47) and Faculty of Health Sciences (Nutrition and Dietetics Department 74) in the spring term of 2021-2022 academic year. The research group consisted of a total of 164 students (124 female, 40 male). The data of the research were collected by qualitative research method and the research was organized in a phenomenological design. To determine the perceptions of the students about the concept of climate change, a semi-structured form containing the expression "climate change is like............because........." was prepared and the students were asked to complete the sentence given in the form. The data obtained were subjected to content analysis. Tables were created by calculating the number of metaphors in each category, how many students repeated the metaphor (frequency), and percentage values. When the findings of the research are evaluated, it is seen that a total of 96 valid metaphors were produced by the students. These metaphors were coded by considering their common features and 8 different conceptual categories were formed. Some of these categories are "Climate change leading to uncertainty", "Climate change as a symptom of danger/worry", "Climate change as the beginning of change", "Climate change as the work of insensitivity", "Climate change as a factor forcing to get used to the new situation", "Climate change with a disruptive effect", "Climate change as a cause of despair", "Climate change as a source of different thoughts", and the number of metaphor and frequencies of these categories are calculated and given in tables. When the findings obtained are analyzed, it is seen that the most recurrent metaphor for climate change includes concepts such as human (f=5), mental state (f=4), life (f=3), a sick body (f=3), disappointment (f=3), cancer (f=3), extinction (f=4), moving (f=4), disaster (f=3), end of the world (f=3), and chaos (f=2). When the metaphor produced by the students in this study are analyzed, it is seen that the perceptions of university students about the concept of climate change are diverse and rich.  Article visualizations

Determination of high school students’ cognitive structures related to the atmosphere and climate

The aim of this study was to determine the cognitive structures of high school students related to the atmosphere and climate. The study group consists of 70 students in the 10th grade of a state high school affiliated to Konya Provincial Ministry of National Education. In this study, a survey model, which allowed us to determine the current situation, was used. Data were collected using the word association test (WAT). The key concepts related to the subject were climate, atmosphere, temperature, pressure, wind, humidity, and precipitation. A frequency calculation, a descriptive analysis technique, was used to analyze the data. The obtained data were subjected to evaluation, and a frequency table was prepared. Among the key concepts, the most response words were related to climate (n=20). The others were the atmosphere (n=14), temperature (n=14), humidity (n=11), precipitation (n=11), pressure (n=10) and wind (n=8). The answer word rain (n=49) was written for the key concept of precipitation and had the highest frequency value. The answer words for the key concepts were analyzed in detail, and concept networks were created using the cut-off point technique. Thus, it was attempted to reveal the cognitive structures of the students regarding the subject. In addition, sentence examples were analyzed and classified according to their characteristics and a scientific content table was created

Expression of calretinin, marker of mesothelial differentiation, in pancreatic ductal adenocarcinoma: A potential diagnostic pitfall

Objective: Pancreatic ductal adenocarcinoma is one of the most common causes of "peritoneal carcinomatosis" and has an insidious growth pattern. Thus, it falls into the differential diagnosis of other peritoneal malignancies including malignant mesothelioma. Recently, we have encountered an undifferentiated pancreatic carcinoma presenting with peritoneal disease and exhibiting immunoreactivity to calretinin, mimicking mesothelioma. In this study, we explored the incidence of calretinin expression in pancreatic ductal adenocarcinoma. Materials and Methods: Calretinin immunohistochemical staining was performed on the tissue microarrays (TMAs), which were created using three 0.6 mm diameter punches per tumor (n=113). Distribution and intensity of expression were evaluated. Results: The TMAs contained 86 well/moderately differentiated and 27 poorly differentiated/undifferentiated carcinomas. Calretinin was positive in nine tumors (8%); six with diffuse and strong staining, three with focal and/or weak staining. The incidence of calretinin expression was 15% in poorly differentiated/undifferentiated carcinomas (vs. 6% in well/moderately differentiated carcinomas, p=0.03). Conclusions: Pancreatic ductal adenocarcinomas, especially when poorly differentiated/undifferentiated, may be diffusely and strongly positive for calretinin creating a potential diagnostic challenge with malignant mesothelioma. Therefore, caution should be exercised when using this marker to explore a diagnosis of malignant mesothelioma. Tumors expressing calretinin without other mesothelial markers should prompt a careful evaluation of the morphologic and immunohistochemical features to exclude other malignancies. If the diagnosis of pancreatic ductal adenocarcinoma is considered, ductal differentiation can be demonstrated by using additional immunohistochemical markers such as mucin-related glycoproteins (MUC1, MUC5AC) and/or oncoproteins (CEA, B72.3, CA125)