Thermo mechanical analysis of a ceramic coated piston used in a diesel engine

Ekrem Buyukkaya,Muhammet Cerit,Mehmet Coban 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.2

The aim of this paper is to determine temperature and stress distributions in a ceramic based on Partially Stabilized Zirconia coated steel piston crown by using plasma spraying for improving performance of a marine diesel engine. Effects of coating constituent and thickness on temperature and stress distributions were investigated including comparisons with results from an uncoated piston by means of finite element method namely ANSYS. Temperature developed at the coated surface is significantly higher than that of the uncoated piston. The maximum stress components occur between bond coat and adjacent ceramic layer. Provided that coating thickness is constant as 0.5 mm, when numbers of layers increase, magnitude of the normal stress decrease about 34.1% on the base metal surface according to uncoated piston, but the base metal surface temperature of the steel piston increase about 13.1%.

Effects of geometric parameters on in-plane vibrations of two-stepped circular beams

Ekrem Tufekci,Oznur Ozdemirci Yigit 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

In-plane free vibrations of circular beams with stepped cross-sections are investigated by using the exact analytical solution. The axial extension, transverse shear deformation and rotatory inertia effects are taken into account. The stepped arch is divided into a number of arches with constant crosssections. The exact solution of the governing equations is obtained by the initial value method. Several examples of arches with different step ratios, different locations of the steps, boundary conditions, opening angles and slenderness ratios for the first few modes are presented to illustrate the validity and accuracy of the method. The effects of the geometric parameters on the natural frequencies are investigated in details. Several examples in the literature are solved and the results are given in tables. The agreement of the results is good for all examples considered. The mode transition phenomenon is also observed for the stepped arches. Some examples are solved also numerically by using the commercial finite element program ANSYS.

Effects of Annealing on Irradiated SiC Piezoresistive Pressure Sensor

Ekrem Almaz,Thomas E. Blue 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.7

The effects of temperature on the annealing of a silicon carbide (SiC) piezoresistive pressure sensor exposed to high-fluence neutron irradiation were investigated. The, SiC piezoresistive sensor was irradiated with gamma rays with the ⁶⁰Co gamma-ray irradiator, and fast neutrons at Beam Port 1 (BP1) and at the Auxiliary Irradiation Facility (AIF) of Ohio State University’s Nuclear Reactor Laboratory (OSUNRL). Annealing temperatures up to 400 ℃ were applied to the pressure sensor. The pressure-output voltage results showed recovery after the SiC piezoresistive pressure sensor had been annealed. The bridge resistances of the SiC pressure sensor stayed at the same level for annealing temperatures up to 300 ℃. After annealing at 400 ℃, the resistance values of the sensor changed dramatically.

DOUBLE IDEAL LACUNARY STATISTICAL CONVERGENCE IN TOPOLOGICAL GROUPS

EKREM SAVAS 장전수학회 2018 Advanced Studies in Contemporary Mathematics Vol.28 No.4

In this paper, we introduce new notion, namely, I- la- cunary double statistical convergence in topological groups. We also investigate some inclusion relations between I- double statistical and I- lacunary double statistical convergence.

Secure Broadcasting Using Multiple Antennas

Ekrem, Ersen,Ulukus, Sennur The Korea Institute of Information and Commucation 2010 Journal of communications and networks Vol.12 No.5

We consider three different secure broadcasting scenarios: i) Broadcast channels with common and confidential messages (BCC), ii) multi-receiver wiretap channels with public and confidential messages, and iii) compound wiretap channels. The BCC is a broadcast channel with two users, where in addition to the common message sent to both users, a private message, which needs to be kept hidden as much as possible from the other user, is sent to each user. In this model, each user treats the other user as an eavesdropper. The multi-receiver wiretap channel is a broadcast channel with two legitimate users and an external eavesdropper, where the transmitter sends a pair of public and confidential messages to each legitimate user. Although there is no secrecy concern about the public messages, the confidential messages need to be kept perfectly secret from the eavesdropper. The compound wiretap channel is a compound broadcast channel with a group of legitimate users and a group of eavesdroppers. In this model, the transmitter sends a common confidential message to the legitimate users, and this confidential message needs to be kept perfectly secret from all eavesdroppers. In this paper, we provide a survey of the existing information-theoretic results for these three forms of secure broadcasting problems, with a closer look at the Gaussian multiple-input multiple-output (MIMO) channel models. We also present the existing results for the more general discrete memoryless channel models, as they are often the first step in obtaining the capacity results for the corresponding Gaussian MIMO channel models.

A unified formulation for static behavior of nonlocal curved beams

Ekrem Tufekci,Serhan A. Aya,Olcay Oldac 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3

Nanobeams are widely used as a structural element for nanodevices and nanomachines. The development of nano-sized machines depends on proper understanding of mechanical behavior of these nano-sized beam elements. Small length scales such as lattice spacing between atoms, surface properties, grain size etc. are need to be considered when applying any classical continuum model. In this study, Eringen’s nonlocal elasticity theory is incorporated into classical beam model considering the effects of axial extension and the shear deformation to capture unique static behavior of the nanobeams under continuum mechanics theory. The governing differential equations are obtained for curved beams and solved exactly by using the initial value method. Circular uniform beam with concentrated loads are considered. The displacements, slopes and the stress resultants are obtained analytically. A detailed parametric study is conducted to examine the effect of the nonlocal parameter, mechanical loadings, opening angle, boundary conditions, and slenderness ratio on the static behavior of the nanobeam.

Analytical solutions of in-plane static problems for non-uniform curved beams including axial and shear deformations

Ekrem Tufekci,Alaeddin Arpaci 국제구조공학회 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.2

Analytical solutions of in-plane static problems for non-uniform curved beams including axial and shear deformations

Tufekci, Ekrem,Arpaci, Alaeddin Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.2

Exact analytical solutions for in-plane static problems of planar curved beams with variable curvatures and variable cross-sections are derived by using the initial value method. The governing equations include the axial extension and shear deformation effects. The fundamental matrix required by the initial value method is obtained analytically. Then, the displacements, slopes and stress resultants are found analytically along the beam axis by using the fundamental matrix. The results are given in analytical forms. In order to show the advantages of the method, some examples are solved and the results are compared with the existing results in the literature. One of the advantages of the proposed method is that the high degree of statically indeterminacy adds no extra difficulty to the solution. For some examples, the deformed shape along the beam axis is determined and plotted and also the slope and stress resultants are given in tables.

Secure Broadcasting Using Multiple Antennas

Ersen Ekrem,Sennur Ulukus 한국통신학회 2010 Journal of communications and networks Vol.12 No.5

We consider three different secure broadcasting scenarios:i) Broadcast channels with common and confidential messages (BCC), ii) multi-receiver wiretap channels with public and confidential messages, and iii) compound wiretap channels. The BCC is a broadcast channel with two users, where in addition to the common message sent to both users, a private message, which needs to be kept hidden as much as possible from the other user, is sent to each user. In this model, each user treats the other user as an eavesdropper. The multi-receiver wiretap channel is a broadcast channel with two legitimate users and an external eavesdropper,where the transmitter sends a pair of public and confidential messages to each legitimate user. Although there is no secrecy concern about the public messages, the confidential messages need to be kept perfectly secret from the eavesdropper. The compound wiretap channel is a compound broadcast channel with a group of legitimate users and a group of eavesdroppers. In this model, the transmitter sends a common confidential message to the legitimate users, and this confidential message needs to be kept perfectly secret from all eavesdroppers. In this paper, we provide a survey of the existing information-theoretic results for these three forms of secure broadcasting problems, with a closer look at the Gaussian multiple-input multiple-output (MIMO) channel models. We also present the existing results for the more general discrete memoryless channel models, as they are often the first step in obtaining the capacity results for the corresponding Gaussian MIMO channel models.

Effects of geometric parameters on in-plane vibrations of two-stepped circular beams

Tufekci, Ekrem,Yigit, Oznur Ozdemirci Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

In-plane free vibrations of circular beams with stepped cross-sections are investigated by using the exact analytical solution. The axial extension, transverse shear deformation and rotatory inertia effects are taken into account. The stepped arch is divided into a number of arches with constant cross-sections. The exact solution of the governing equations is obtained by the initial value method. Several examples of arches with different step ratios, different locations of the steps, boundary conditions, opening angles and slenderness ratios for the first few modes are presented to illustrate the validity and accuracy of the method. The effects of the geometric parameters on the natural frequencies are investigated in details. Several examples in the literature are solved and the results are given in tables. The agreement of the results is good for all examples considered. The mode transition phenomenon is also observed for the stepped arches. Some examples are solved also numerically by using the commercial finite element program ANSYS.