Formally self-dual codes over F₂[u]/‹u⁴›

In this work, Gray images of formally self-dual codes over the ring S₄ = F₂[u]/‹u⁴› and some of their construction methods are considered. As a result, a considerable number of good formally self-dual binary codes with large automorphism groups have been obtained from the Gray images of formally self-dual codes over S₄. Some have better minimum distances than the best known binary self-dual codes of the same lengths.Publisher's Versio

Generalization of the lee weight to Ζpᵏ

We introduce a new extension of the Lee weight to Ζpᵏ and later to Galois rings GR(pᵏ,m). The weight we define is a non-homogeneous weight and is different than the one that is generally labeled as "generalized Lee weight". Unlike the case of generalized Lee weight, we define a distance-preserving Gray map from (Ζpᵏ, extended Lee distance)to (Fppᵏ⁻¹, Hamming distance), thus making our extension practical for coding theory purposes.Publisher's Versio

A systematic study on numerical simulation of electrified jet printing

In this paper, a systematic study on the numerical modeling for electrified jet printing is presented. The numerical tool is the Volume of Fluid (VOF) method which suits for modeling multiphase flows with a continuous interface. The surface tension force is calculated with the Continuum Surface Force (CSF) method and the electric forces are added to the momentum equation by taking the divergence of the Maxwell stress tensor. A systematic study is carried out by introducing three dimensionless numbers, Reynolds, Electro-Weber and Weber numbers. Employing these dimensionless numbers, the number of effective parameters is reduced, and a relative comparison on the importance of competing forces on the process becomes possible. It is observed that the electric forces contribute to the formation of the jet by acting on its tip, and by pulling the jet towards the deposition surface. The results show that increments of Reynolds and Electro-Weber numbers both lead to form a thinner jet. It is also seen that in larger Electro-Weber and Reynolds numbers, an unstable jet is obtained

A systematic study on numerical simulation of electrified jet printing

In this paper, a systematic study on the numerical modeling for electrified jet printing is presented. The numerical tool is the Volume of Fluid (VOF) method which suits for modeling multiphase flows with a continuous interface. The surface tension force is calculated with the Continuum Surface Force (CSF) method and the electric forces are added to the momentum equation by taking the divergence of the Maxwell stress tensor. A systematic study is carried out by introducing three dimensionless numbers, Reynolds, Electro-Weber and Weber numbers. Employing these dimensionless numbers, the number of effective parameters is reduced, and a relative comparison on the importance of competing forces on the process becomes possible. It is observed that the electric forces contribute to the formation of the jet by acting on its tip, and by pulling the jet towards the deposition surface. The results show that increments of Reynolds and Electro-Weber numbers both lead to form a thinner jet. It is also seen that in larger Electro-Weber and Reynolds numbers, an unstable jet is obtained

Elastic properties of coiled carbon nanotube reinforced nanocomposite: a finite element study

This paper presents modeling and analysis of coiled carbon nanotube (CCNT) reinforced polymer nanocomposites. A new algorithmic representative volume element (RVE) generation method and an RVE based finite element analysis are proposed to predict the elastic properties of CCNT nanocomposites. The elastic properties of CCNT polymer nanocomposites are studied with respect to their interphase, volume fraction, orientation, number of coils and geometrical variations such as tube diameter, coil diameter and helix angle using the proposed finite element analysis. The results show that the elastic moduli of randomly and unidirectionally dispersed CCNT nanocomposites decrease when the coil tube or the coil diameter increases. In addition, reinforcement ratio increases by increasing the number of coils. It was also observed that single walled carbon nanotube (SWCNT) fillers have better reinforcement compared to CCNT inclusions with the same volume to surface area ratio

Realtime localization and estimation of loads on aircraft wings from depth images

This paper deals with the development of a realtime structural health monitoring system for airframe structures to localize and estimate the magnitude of the loads causing deflections to the critical components, such as wings. To this end, a framework that is based on artificial neural networks is developed where features that are extracted from a depth camera are utilized. The localization of the load is treated as a multinomial logistic classification problem and the load magnitude estimation as a logistic regression problem. The neural networks trained for classification and regression are preceded with an autoencoder, through which maximum informative data at a much smaller scale are extracted from the depth features. The effectiveness of the proposed method is validated by an experimental study performed on a composite unmanned aerial vehicle (UAV) wing subject to concentrated and distributed loads, and the results obtained by the proposed method are superior when compared with a method based on Castigliano's theorem

Peridynamics topology optimization of three-dimensional structures with surface cracks for additive manufacturing

Additive manufacturing (AM) is an effective approach to fabricating intricate shapes obtained from topology optimization (TO). However, it may cause undesired manufacturing-induced defects/cracks due to high thermal residual stresses. This study proposes a PeriDynamics-enabled three-dimensional Topology Optimization method (PD-TO) for designing structures by considering surface cracks for the AM processes. The PD-TO approach employs a bi-directional evolutionary structural optimization method and uses particle discretization of geometry for mechanical analysis. Crack surfaces are generated by breaking three-dimensional nonlocal interactions of the particles, and thus, during the optimization process, complex multiple structural discontinuities can be diligently modeled. First, the proposed approach is validated by solving benchmark problems without cracks. For each benchmark geometry, the PD-TO analysis is then performed by considering different positions and numbers (single/multiple) of cracks. These analyses extensively investigate and demonstrate the effects of a priori knowledge of residual stress-induced damages/cracks on the optimum topology for additive manufacturing. Besides, the smoothing operation is applied to the optimum designs to transform voxel shapes into AM-friendly smooth surfaces. These geometries are manufactured by an extrusion-based AM process to demonstrate the practical engineering application of the proposed method. Finally, the comparison of numerical results is also supported by the experimental tests conducted on the optimized topologies. Overall, it is confirmed that the PD-TO approach is a viable and accurate optimization tool for additive manufacturing considering possible process-induced damages

Cumhuriyet sonrası Türkiye tarı

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2017.This work is a student project of the The Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.by Demirakın, Nahide Işık