Sustainable housing in island conditions using Alker-gypsum-stabilized earth: A case study from northern Cyprus

The materials and energy sources needed for construction are limited by island conditions. Until recent decades, earth was widely used as a construction material in northern Cyprus due to its abundance and many technical advantages, however, as a construction material, earth is vulnerable to moisture. Ongoing research into gypsum-stabilized earth (known as Alker) at Istanbul Technical University since 1978 demonstrates the superior physical properties, increased durability, and human health benefits of this improved earthen material.     

Effect of source spectral shape on task-based assessment of detection and resolution in optical coherence tomography

We demonstrate the effect of the spectral shape of broadband light sources in a task-based approach for assessment of signal detection and resolution in optical coherence tomography. We define two binary tasks: The signal is either present or absent and the signal can be either resolved or not. In a transparent sample bounded by two uniform interfaces we study the minimum detectable change in the index of refraction as well as the minimum resolvable distance between the layers in correlation with the source spectral shape and power. Results show that the area under the receiver operating curve (AUC) for a signal-detection task is not affected by the shape of the spectrum but solely by its optical power, whereas spectral shaping has an effect, which we quantify, on the AUC for the resolution task. Moreover, the AUC is demonstrated in relation to the concept of system sensitivity for a signal-detection task.     

Analysis of spiral metamaterials by use of group theory

Monofilar, bifilar, trifilar and quadrifilar Archimedean spiral metamaterial particles are analyzed by using point group symmetry and the methods of crystallography. From the symmetry properties electromagnetic response is determined. Magnetic, electric and magnetoelectric modes of the particles are identified along with their isotropy characteristics. Theoretical methods show that all the particles, except monofilar spiral, are non-bianisotropic. Numerical simulation results are presented to verify the analysis. Finally, effective medium theory is applied to extract the effective permeability of the spiral medium. The results indicate negative values for permeability in certain frequency ranges.     

Finite element analysis of GTAW arc under different shielding gases

The aim of this work is to use COMSOL software as a tool for solving the 2-D Magnetohydrodynamics (MHD) problem in the Gas Tungsten Arc Welding (GTAW) arc under the shielding gases argon, helium, nitrogen and argon + 10% hydrogen. COMSOL 3.5a worked perfectly for solving multiphysics phenomena, including the Navier-Stokes flow equation, the heat transfer equation and the Maxwell Equation. COMSOL software can be utilized to simulate the temperature and velocity profile in the GTAW arc after some validation procedures. Cumbersome experimental work can be avoided by using this numerical instrument.For our study, we compared the numerically calculated temperature profile and maximum plasma velocity under argon shielding gas and maximum temperature of a nitrogen arc with experimental results found in the literature. We also compared the numerically calculated velocity profile with another numerical solution found in the literature. Our comparisons showed good agreement. The highest temperature was in the nitrogen arc, while the highest voltage was in the helium arc. The highest total energy was in the helium arc similar to the voltage value. The highest plasma velocity values were obtained in the nitrogen and helium arcs. The most constricted arc was calculated in the nitrogen arc.