Ortak Dersler Bölümü

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A New Estimation Technique for AR(1) Model with Long-Tailed Symmetric Innovations
(2017) Dener Akkaya, Ayşen; Türker Bayrak, Özlem; 56416
In recent years, it is seen in many time series applications that innovations are non-normal. In this situation, it is known that the least squares (LS) estimators are neither efficient nor robust and maximum likelihood (ML) estimators can only be obtained numerically which might be problematic. The estimation problem is considered newly through different distributions by the use of modified maximum likelihood (MML) estimation technique which assumes the shape parameter to be known. This becomes a drawback in machine data processing where the underlying distribution cannot be determined but assumed to be a member of a broad class of distributions. Therefore, in this study, the shape parameter is assumed to be unknown and the MML technique is combined with Huber’s estimation procedure to estimate the model parameters of autoregressive (AR) models of order 1, named as adaptive modified maximum likelihood (AMML) estimation. After the derivation of the AMML estimators, their efficiency and robustness properties are discussed through simulation study and compared with both MML and LS estimators. Besides, two test statistics for significance of the model are suggested. Both criterion and efficiency robustness properties of the test statistics are discussed, and comparisons with the corresponding MML and LS test statistics are given. Finally, the estimation procedure is generalized to AR(q) models.
A New Estimation Technique for AR(1) Model with Long-Tailed Symmetric Innovations
(Springer, 2018) Dener Akkaya, Ayşen; Türker Bayrak, Özlem; 56416
In recent years, it is seen in many time series applications that innovations are non-normal. In this situation, it is known that the least squares (LS) estimators are neither efficient nor robust and maximum likelihood (ML) estimators can only be obtained numerically which might be problematic. The estimation problem is considered newly through different distributions by the use of modified maximum likelihood (MML) estimation technique which assumes the shape parameter to be known. This becomes a drawback in machine data processing where the underlying distribution cannot be determined but assumed to be a member of a broad class of distributions. Therefore, in this study, the shape parameter is assumed to be unknown and the MML technique is combined with Huber’s estimation procedure to estimate the model parameters of autoregressive (AR) models of order 1, named as adaptive modified maximum likelihood (AMML) estimation. After the derivation of the AMML estimators, their efficiency and robustness properties are discussed through simulation study and compared with both MML and LS estimators. Besides, two test statistics for significance of the model are suggested. Both criterion and efficiency robustness properties of the test statistics are discussed, and comparisons with the corresponding MML and LS test statistics are given. Finally, the estimation procedure is generalized to AR(q) models.
A phenomenological study on ferroelastic KH3(SeO3)(2) and KD3(SeO3)(2)
(2021) Kiracı, Ali; 42475
The anomalous behavior of the Brillouin frequency shift omega of the soft acoustic mode for KH3(SeO3)(2) and KD3(SeO3)(2), and also the volume thermal expansion proportional to(V) and the specific heat C of KH3(SeO3)(2) have been analyzed for various temperature intervals close to the phase transition temperatures TC at around 211 K and 302 K, respectively. Our extracted values of the critical exponent from C and proportional to(V) of KH3(SeO3)(2) within the temperature intervals of vertical bar T -T-C vertical bar < 7 K are nearly zero, while the critical exponent extracted from the Brillouin frequency shift data of both KH3(SeO3)(2) and KD3(SeO3)(2) within the same temperature interval of vertical bar T -T-C vertical bar < 7 K decrease very rapidly toward to zero as the phase transition temperatures are approached. Our results indicate that the critical behavior of omega, proportional to(V) and C of both KH3(SeO3)(2) and KD3(SeO3)(2) can be described with the same critical exponent within the temperature interval of vertical bar T -T-C vertical bar < 2 K.
A phenomenological study on ferroelectric pyridinium tetrafluoroborate (C5NH6) BF4
(Elsevier, 2019) Kiracı, Ali; 42475
The temperature dependence of the specific heat C-V of (C5NH6)BF4 was analyzed according to a power law formula with a critical exponent alpha deduced from the compressible Ising model in the vicinity of the phase transition temperatures of T-C1 = 238 K and T-C2 = 204 K. The extracted values of the critical exponent alpha within the temperature intervals of vertical bar T - T-C1 vertical bar < 6 K and also T - T-C2 < 6 K were consistent with that predicted from the 3d-Ising model (alpha = 0.10) while obtained values of alpha within the temperature interval of T-C2 - T < 6 K were consistent with that predicted from 2-d potts model (alpha = 0.30). In addition, the thermodynamic quantities: the internal energy (U), the entropy (S) and the Helmholtz free energy (F) of this compound were calculated on the basis of the extracted values of the critical exponent a below and above the phase transition temperatures of T-C1 and T-C2.
A phenomenological study on ferroelectric β-glycine
(2021) Kiracı, A; 42475
The anomalous behavior of the specific heat for (Formula presented.) -glycine was analyzed in terms of the compressible Ising model approximately 5 K below and above the ferrelectric-paraelectric phase transition temperature of TC = 252 K. The obtained value of the critical exponent (Formula presented.) = 0.12 in the ferroelectric phase (T < TC) was consistent with that predicted from the 3-d Ising model ((Formula presented.) = 0.13), while the obtained value of (Formula presented.) = 0.32 in the paraelectric phase (T > TC) was consistent with that predicted from the 2-d potts model ((Formula presented.) = 0.30). Some thermodynamic quantities such as the internal energy, the entropy and the free energy of (Formula presented.) -glycine were then predicted in terms of these extracted values of the critical exponents close to the phase transition temperature of TC. Our calculated values of the thermodynamic quantities are in good agreement with the observed data.
A sign of the past: Aliye berger
(2015) Okur Tolun, Elif
Aliye Berger , who has a privileged place in The Turkish Painting Art , stayed away from the generation clash of her time and various groupings. She was an artist who had an aim to acquire a place in art community. Her privileged place in art , and her life without giving attention to social pressure has result as reflecting her own her life style to her works. She is one of the artists who acts as herself. Her artistic style is just like an action which has a fictional expression upon her own identity. Creation is not producing extraordinary things, creating shapes and strolling around the current time. Art has no gender, nationality and race. What is important is the necessity to do something real by feeling those deeply. People whom we can call genuine artists can easily assimilate polyphony in life and with some sensibility they can spend a whole life to reflect these with some bravery. Just as Aliye Berger, her art is also fed by her life. Her actions become a part of her life and create their own symbols. Thus, her works turn into their genuine feature. In this paper, it is aimed to understand the identity of Aliye Berger through her gravures. As a woman artist who has gone beyond her own age with an analysis through her art, it is aimed to investigate her artistic personality and extraordinary sensitivity. This study is neither a history of art nor a biography of literary agent; it is an approach with the artist’s eye Berger’s drawings. Trying to understand her through the fancy world she created, insight of beauty, a place of fiction, technical restructuring and critiques related to her art and the visual materials and by investigating her works we wanted to create a written portrait of Aliye Berger. Keywords: Aliye Berger, print making, identity, gravure, image.
A Study On How to Equip Students With Scientific Communication Skills
(Springer Verlag, 2018) Akkoyunlu, Buket; Akkoyunlu, Buket; 8539
The purpose of this study was to investigate the effects of scientific communication (SC) curriculum on blog writing skills of sixth-grade students, and opinions of the students and teachers about the curriculum. Through the curriculum, it was aimed to teach students the ability to access and evaluate information, organize information and share it by writing a blog. Students were given three different writing assignments and were asked to share them in their blogs. The first assignment was given for adapting to the writing process. The second and third assignments were assessed to determine the effect of SC curriculum on blog writing skills. At the end of the process, teachers and students were asked about their opinions on SC curriculum and blog writing. Study results revealed that SC curriculum had positive effects on research and writing skills development of the students, and showed that the curriculum was supportive in reaching the course-specific goals.
A Theoretical Investigation: Effect of Structural Modifications on Molecular, Electronic, and Optical Properties of Phosphonate Substituted BODIPY Dyes
(2021) Tasgin, Dilek Isik; Sirin, Pınar Seyitdanlioglu; 169107
Phosphonates are important organophosphorus compounds which exhibit versatile properties in organic chemistry, medicinal chemistry, materials and biological applications. Phosphonate groups have appeared in a very few examples of BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) compounds that are important florescent dyes in these areas. The deficiency in the area motivated us to investigate how the phosphonate substituent(s) affect the structural, electronic, and optical properties of meso, α, or α, α′-substituted BODIPYs using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. We have identified the suitable method as HSEH1PBE functional in combination with the basis set 6-31+G** by comparing the theoretical results with the experimental studies. Structural, electronic and optical parameters of a series of designed phosphonate substituted 12 BODIPYs (1-4) have been investigated. The α, and α, α′-vinyl phosphonate substituted BODIPYs (3,4) compared to meso-substituted BODIPYs (1,2) have both lower HOMO/LUMO electronic energies [(−5.57)-(−6.19)/(−3.16)-(−3.91)] and lower electronic energy gaps (Egap) (2.11–2.42). Electrostatic potential analysis was performed for all BODIPYs to characterize their electron distribution and TD-DFT analysis was used for the absorption spectral analysis. The presented theoretical approach can be a practical guide for experimental studies for the design of new BODIPY compounds with desired properties.
A Thermodynamic Study On Pbzr0.52Ti0.48O3 Ceramic Close to the Tetragonal-Cubic Transition
(Springer, 2020) Kiracı, Ali; 42475
The isobaric Grüneisen parameter and the wavenumber (frequency) of various Raman modes in PbZr1-xTixO3 (PZT x = 0.48) ceramic were calculated by means of the unit cell volume of this crystal. In addition, the damping constant (linewidth) of the Raman modes studied was computed from the pseudospin-phonon coupled and from the energy fluctuation models close to the tetragonal-cubic transition temperature of TC = 650 K. This calculation of the damping constant performed in terms of the order parameter (spontaneous polarization), which was associated with the wavenumbers of the Raman modes studied. Furthermore, the inverse relaxation time of the Raman modes in this ceramic calculated and the values of the activation energy were deduced in terms of the Arrhenius plot close to the tetragonal-cubic transition in PZT (x = 0.48) ceramic. Finally, the temperature dependence of some thermodynamic quantities, such as the isothermal compressibility and the specific heat of this ceramic, was predicted.
Adaptation of the Student Expectations of Online Learning Survey Revised (SEOLS-R) into Turkish
(2020) Akkoyunlu, Buket; Dağhan, Gökhan; Akkoyunlu, Buket; 8539
The aim of this study is to adapt the Student Expectations of Online Learning Survey Revised [SEOLS-R] developed by Harris, Larrier and Castano-Bishop (2011) into Turkish. For this purpose, the adaptation process of the scale, which consists of 7 factors and 43 items in the 5-point Likert structure, started first with the necessary permissions, and then a translation and cultural adaptation process was carried out. After the cultural adaptation process, the construct validity of the scale was tested with 411 students who study in distance education programs of Amasya University. After the construct validity findings, the reliability values of the scale were examined. In line with the findings, it was concluded that the Turkish version of the SEOLS-R scale is a valid and reliable measurement tool suitable for Turkish culture.
Adaptive Estimation of Autoregressive Models Under Long-Tailed Symmetric Distribution
(Association for Computing Machinery, 2019) Yengür, Begüm; Bayrak, Özlem Türker; Dener Akkaya, Ayşen; 56416
In this paper, we consider the autoregressive models where the error term is non-normal; specifically belongs to a long-tailed symmetric distribution family since it is more relevant in practice than the normal distribution. It is known that least squares (LS) estimators are neither efficient nor robust under non-normality and maximum likelihood (ML) estimators cannot be obtained explicitly and require a numerical solution which might be problematic. In recent years, modified maximum likelihood (MML) estimation is developed to overcome these difficulties. However, this method requires that the shape parameter is known which is not realistic in machine data processing. Therefore, we use adaptive modified maximum likelihood (AMML) technique which combines MML with Huber’s estimation procedure so that the shape parameter is also estimated. After derivation of the AMML estimators, their efficiency and robustness properties are discussed through a simulation study and compared with MML and LS estimators.
An Exploration of the Landscape of Instructional Design: Understanding Changes and Pandemic Effects (2017-2022)
(2024) Akkoyunlu, Buket; Akkoyunlu, Buket; Yelbay Yılmaz, Yasemin; 8539
The purpose of this study is to examine the scope of the field of instructional design and technology, along with the working area (desk) of the expert in this field, in the context of the effects of the pandemic. The study is a bibliographic mapping research. The data set includes bibliographic records of 2.397 scientific texts retrieved from the WOS Core Collection within the time range of 2017-2022 using search terms instructional design or instructional designer. Co-occurrence analyses encompassing author keywords were conducted on the data. As a result, maps and related outputs were obtained that reveal the concepts that the field focused on before and after the pandemic, as well as the relationships between these. Additionally, attempts were made to identify emerging concepts for both periods based on the outputs. According to the results, there has been a significant expansion in the concepts falling within the scope of instructional design and technology, and consequently in the roles and responsibilities of designers, in conjunction with the 2020s and the Covid-19 pandemic. Design concepts and variables, context, human factors, and research methodology are enriched within this expansion. This enrichment shifts the design process from a micro perspective focusing on learning environment and environmental variables to a macro perspective that emphasizes instructors, educational institutions, and culture. Within this perspective, while the weight of real instructional problems increases, the emphasis on theory, approach, and models significantly decreases.
An Investigation of the Digital Footprint Awareness and Experiences of Secondary School Students
(2021) Akkoyunlu, Buket; Demiröz, Seva; Akkoyunlu, Buket; 8539
The aim of this study is to examine the digital footprint awareness of middle school students according to grade level, gender, time spent on electronic devices and media. First of all, the digital footprint scale developed for secondary school students was evaluated in terms of its psychometric properties. Then, the digital footprint awareness of the participants was examined according to the variables mentioned above. Participants consisted of 204 female and 189 male students. In addition to the Digital Footprint Scale, participants were given a form containing questions about students' gender, age, grade levels, and time spent with a mobile phone, internet, social media, and online game playing. The results indicated that the Digital Footprint Scale is a valid and reliable tool for the use of researchers, educators, administrators, and parents.
Analysis and mathematical computation of some dynamic function for strontium stannate
(2021) Aşkun, Ali Rıza; 56475
The frequency and full width at half maximum (FWHM) data of the Ag Raman modes (95.4, 231.4 and 263.2 cm−1) in strontium stannate crystal have been analyzed using the Balkanski model and the fitting parameters were determined. Also, the isobaric Grüneisen parameter of Ag Raman modes studied here was computed below the room temperature. This computation was performed from the unit cell volume and the observed frequency data of this crystal. Finally, values of the activation energy were extracted close to the structural phase transition temperatures of 160 and 265 K using the observed FWHM data of strontium stannate.
Analysis and mathematical computation of some dynamic functions for the guanidine zinc sulfate
(2021) Aşkun, A.R.; Kiraci, A.; 56475
A power-law formula with a critical exponent (Formula presented.) was used to analyze the anomalous behavior of the specific heat for guanidine zinc sulfate (GZS) crystal close to the phase transition temperature of TC = 178.4 K. The obtained values of 0.13 and 0.14 for (Formula presented.) below (T < TC) and above (T > TC) the phase transition temperature, respectively, were almost the same value of 0.13 (1/8) that predicted from the 3-D Ising model. Also, the internal energy (Formula presented.) the entropy (Formula presented.) and the free energy (Formula presented.) of this crystal were calculated as a function of temperature close to the phase transition temperature of TC = 178.4 K.
Analysis of the specific heat and the free energy and calculation of the entropy and the internal energy of [N(CH3)(4)](2)MnBr4 close to the phase transition
(2021) Kiracı, Ali; 42475
The critical behavior of the specific heat and the Gibbs free energy of [N(CH3)(4)](2)MnBr4 was analyzed using the 'sing model close to the phase transition temperature of T-c = 276.5 K. Obtained value of alpha=0.02 from the Gibbs free energy and from the specific heat approximately 2.0 K and 1.4 K, respectively, below Tc (ferroelastic phase) and also deduced value of alpha= 0.04 from the specific heat approximately 0.3 K above T-c (paraelastic phase) can be compared with that predicted from mean field theory (alpha = 0). Also, the entropy and the internal energy of this crystal were predicted.
Analysis of the Specific Heat and the Free Energy of [N(Ch 3 ) 4 ] 2 Znbr 4 Close to the Ferro-Paraelastic Phase Transition
(Taylor&Francis LTD, 2019) Kiracı, Ali; 42475
A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat C p and the Gibbs free energy G of [N(CH 3 ) 4 ] 2 ZnBr 4 compound in the vicinity of the phase transition temperature of T C = 287.2 K. Obtained values of the critical exponents α from the Gibbs free energy were consistent with that predicted from 2-d potts model (α = 0.3), while obtained values of α from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory (α = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH 3 ) 4 ] 2 ZnBr 4 compound undergoes a second order type phase transition. Also, the enthalpy (H) and the entropy (S) of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.
Analysis of the specific heat and the free energy of [N(CH3)(4)](2)ZnBr4 close to the ferro-paraelastic phase transition
(2019) Kiracı, Ali; 42475
A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat and the Gibbs free energy of [N(CH3)(4)](2)ZnBr4 compound in the vicinity of the phase transition temperature of T-C = 287.2 K. Obtained values of the critical exponents from the Gibbs free energy were consistent with that predicted from 2-d potts model ( = 0.3), while obtained values of from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory ( = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH3)(4)](2)ZnBr4 compound undergoes a second order type phase transition. Also, the enthalpy () and the entropy () of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.
Analysis of the specific heat and the free energy of [N(CH3)(4)](2)ZnBr4 close to the ferro-paraelastic phase transition
(Taylor&Francis LTD, 2019) Kiracı, Ali; 42475
A power-law formula deduced from the Ising model was used to analyze the temperature dependence of the specific heat and the Gibbs free energy of [N(CH3)(4)](2)ZnBr4 compound in the vicinity of the phase transition temperature of T-C = 287.2 K. Obtained values of the critical exponents from the Gibbs free energy were consistent with that predicted from 2-d potts model ( = 0.3), while obtained values of from the specific heat in both ferroelastic and paraelastic phases were consistent with that predicted from the mean field theory ( = 0) in the vicinity of the phase transition temperature. This is an indication of that [N(CH3)(4)](2)ZnBr4 compound undergoes a second order type phase transition. Also, the enthalpy () and the entropy () of this crystal were calculated in terms of the extracted values of the critical exponent in both ferroelastic and paraelastic phases.
Assessment of the Use of AutoCAD in Mechanical Engineering Technical Drawing Education
(2017) Akyürek, Turgut
: AutoCAD is one of the widely used software tools in engineering education. In this study, a general assessment of AutoCAD for the usage in the mechanical engineering technical drawing education is made. AutoCAD is assessed in terms of the fulfilment of the requirements defined for the main two technical drawing courses. AutoCAD is assessed in terms of its capability in meeting the requirements of the technical drawing courses

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