Sezgisel Algoritmalarla Toplam Potansiyel Optimizasyonu (Sa-Tpo) Yöntemi İle Yapısal Analiz

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2013Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2013Yapı mühendisliğinde eniyileme yöntemleri genellikle tasarım konularında uygulanır. Literatürde bu yönde yapılmış pek çok çalışma bulmak kolaydır. Eniyileme yöntemlerinin yapı analizlerinde kullanılması ise, eniyilemede özellikle sezgisel algoritmalar kullanılıyorsa, çok alışılmış bir uygulama değildir. Bu çalışmada bu eksiklik vurgulanmakta ve kafes kirişler üzerinde yapılan uygulamalarla yöntemin sonlu elemanlar yöntemi de dahil bilinen metodlara üstünlüğü gösterilmektedir.Structural engineers are accustomed to see and to make applications of optimization techniques in design problems. Effectively there are countless studies in the literature in this direction. On the contrary, the works on structural analysis through optimization techniques are very limited in number, especially if metaheuristic algorithms are exploited in optimization. In this study, this gap is emphasized, and by way of examples on trusses, the superiority of the advanced method on classical methods including the well-known Finite Element Method is shown

Competing Ferromagnetic and Charge-Ordered States in Models for Manganites: the Origin of the CMR Effect

The one-orbital model for manganites with cooperative phonons and superexchange coupling $J_{\rm AF}$ has been investigated via large-scale Monte Carlo (MC) simulations. Results for two-orbitals are also briefly discussed. Focusing on electronic density $n$=0.75, a regime of competition between ferromagnetic (FM) metallic and charge-ordered (CO) insulating states was identified. In the vicinity of the associated bicritical point, colossal magnetoresistance (CMR) effects were observed. The CMR is associated with the development of short-distance correlations among polarons, above the spin ordering temperatures, resembling the charge arrangement of the low-temperature CO state.Comment: 4 pages, 4 figures, accepted for publication in the Phys. Rev. Let

Graphical modeling for item difficulty in medical faculty exams

Background: There are different indexes used in the evaluation of exam results. One important index is the difficulty level of the item that is also used in this study to obtain control charts. This article offers  some suggestions for the improvement of multiple-choice tests using item analysis statistics.Materials and Methods: The graphical modeling is important for the rapid and comparative evaluation of test results. The control chart is a tool that can be used to sharpen our teaching and testing skills by inspecting the weaknesses of measurements and producing reliable items. The research data for the application of control charts were obtained using the results of the fourth and fifth.grade studentfs exams at Ondokuz Mayis University, Faculty of Medicine. I.chart or moving range chart (MR) is preferred for whole variable data.Results: It is seen that all observations are within control limits for I.chart, but three points on MR.chart are settled on the LCL. Using x̄-chart with subgroups, it was determined that control measurements were within the upper and lower limits in both charts. The difficulty levels of items were examined by obtaining different variable control charts. The difficulty level of the two items exceeded the upper control limit in R-and S-charts.Conclusion: The control charts have the advantage for classifying items as acceptable or unacceptable based on item difficulty criteria.Key words: Item difficulty, quality control, statistical process control, variable control chart

Dönmeye Karşı Kontrol Altına Alınmış Basit Mesnetli Çubukların Stoke Dönüşümü Yardımıyla Burkulma Analizi

Konferans Bildirisi -- Teorik ve Uygulamalı Mekanik Türk Milli Komitesi, 2015Conference Paper -- Theoretical and Applied Mechanical Turkish National Committee, 2015Bu çalışmada eksenel yüklenmiş basit mesnetli bir kirişin burkulma yüklerinin tespiti için yerel bir analitik yöntem geliştirilmiştir. Ayrıca kiriş uçlarından dönmeye karşı engelleyici yaylar ile sabitlenmiştir. Çalışmada Euler-Bernoulli kiriş teorisi kullanılmıştır. İlk olarak literatürde çok iyi bilinen Euler-Bernoulli kiriş teorisinin denklemi eksenel yükler altında verilmiştir. Analitik genel çözümlerin elde edilmesi için yer değiştirme fonksiyonu Fourier sinüs serisi seçilmiştir. Fourier sinüs serisinin seçilmesinin kirişin basit mesnetli olması ile bir ilgisi bulunmamaktadır. Literatürdeki çalışmalarda basit mesnetli kirişlerin sınır koşullarını sağladığı için genellikle Fourier sinus serileri kullanılmaktadır. Mesnetlerde dönmeye karşı yaylar kullanıldığı için; sınır koşullarında serbestlik sağlaması bakımından Stoke dönüşümü uygulanmıştır. Bu dönüşümün yapılmasının temel amacı yay sabitlerine verilecek değerlerde esneklik sağlamasıdır.This paper presents an analytical method for buckling analysis of simply supported beam with rotational restraints at both ends. Euler Bernoulli theory is used. The lateral displacement function is sellected by a Fourier sine series. Stokes’ transformation is applied to boundary conditions in order to construct the coefficient matrix. This application gives more flexibility for buckling analysis of beams with different boundary conditions. Comparisons are performed to validate present analytical method

Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites

The metal-insulator transition, and the associated magnetic transition, in the colossal magnetoresistance (CMR) regime of the one-orbital model for manganites is here studied using Monte Carlo (MC) techniques. Both cooperative oxygen lattice distortions and a finite superexchange coupling among the $t_{\rm 2g}$ spins are included in our investigations. Charge and spin correlations are studied. In the CMR regime, a strong competition between the ferromagnetic metallic and antiferromagnetic charge-ordered insulating states is observed. This competition is shown to be important to understand the resistivity peak that appears near the critical temperature. Moreover, it is argued that the system is dynamically inhomogeneous, with short-range charge and spin correlations that slowly evolve with MC time, producing the glassy characteristics of the CMR state. The local density-of-states (LDOS) is also investigated, and a pseudogap (PG) is found to exist in the CMR temperature range. The width of the PG in the LDOS is calculated and directly compared with recent scanning-tunneling-spectroscopy (STS) experimental results. The agreement between our calculation and the experiment suggests that the depletion of the conductance at low bias observed experimentally is a reflection on the existence of a PG in the LDOS spectra, as opposed to a hard gap. The apparent homogeneity observed via STS techniques could be caused by the slow time characteristics of this probe. Faster experimental methods should unveil a rather inhomogeneous state in the CMR regime, as already observed in neutron scattering experiments.Comment: 13 pages, 10 figure

PHOTOGRAMMETRIC WIREFRAME AND DENSE POINT CLOUD 3D MODELLING OF HISTORICAL STRUCTURES: THE STUDY OF SULTAN SELIM MOSQUE AND YUSUF AGA LIBRARY IN KONYA, TURKEY

The photogrammetry enables to getting high accuracy measurement with low-cost and easy application in documentation of historical structures. The object details are signified with lines in cultural heritage documentation by photogrammetry. The combination of all the lines create 3D wireframe model of the measurement object. In addition, patch surfaces of the wireframe are mapped with the texture from the images for more realistic visualization. On the other hand, the progress on computer vision and image processing techniques is allowing automatically perform the photogrammetric process. A large number of points that are called dense point cloud can be measured from coverage area of multi view images. The dense point cloud represents the object shape with small space measured points while the wireframe photogrammetry is representing the object with lines. In this study these two photogrammetric methods were evaluated with respect to visualization, cost, labour and measurement time through 3D modelling of historical structures of Sultan Selim Mosque and Yusuf Aga Library

Effect of Preform Thickness and Volume Fraction on Injection Pressure and Mechanical Properties of Resin Transfer Molded Composites

An experimental study is performed to characterize the effect of the thickness of random preforms on injection pressure and mechanical properties of resin transfer molded (RTM) parts. Center-gated, disk-shaped parts are molded using two different chopped-strand glass fiber preforms. Both preforms have random microstructure but different planar densities (i.e., different uncompressed layer thicknesses). Tensile strength, short-beam shear strength, and elastic modulus are measured for parts molded with each preform type at three different fiber volume fractions of 6.84, 15.55, and 24.83%. Although mechanical properties are found to increase linearly with volume fraction, significant difference is not observed between disks containing thick and thin mats at equivalent fiber volume fraction.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline