Journal of Naval Sciences and Engineering

10

Authors: Hakan UÇAR

Accurate prediction of the vibration responses is an essential requirement during the design and optimization stages of mechanical structures. For this reason, a vibration response prediction (VRP) methodology, based on a set of frequency response functions (FRF) and operational responses, is established. In this methodology, defining the sources and transmission paths of the structure accurately is critical. Since it is based on the FRFs of the system, unconsidered sources and/or missing path result in inaccurate predictions. The goal of this paper is to present the effect of a missing path on the prediction results. In accordance with this purpose, a three degree-of-freedom system will be investigated analytically and VRP methodology will be applied along with the calculated receptances and displacements of the system.

15

Authors: Cengiz ERDÖNMEZ

Meshless methods are became an alternative to most popular numerical methods used to solve engineering problems such as Finite Difference and Finite Element Methods. Because of element free nature, problems are solved using meshless methods depending on the general geometry and conditions of the problem. Mixed Meshless Local Petrov-Galerkin (MLPG) approach is based on writing the local weak forms of PDEs. Moving least squares (MLS) is used as the interpolation schemes. In this study contact analysis problem is modelled using Meshless Finite Volume Method (MFVM) with MLS interpolation and solved for beam contact problem. Meshless discretization and linear complementary equation of the 2-D frictionless contact problems are described first. Then the problem is converted to a linear complementary problem (LCP) and solved using Lemke’s algorithm. An elastic cantilever beam contact to a rigid foundation is considered as an example problem.

18

Authors: Yusuf KAVURUCU, Ömer SEVER

As a solution to fair exchange problem, non-repudiation protocols are being widely used over digital environment. Applications of non-repudiation protocols are spreaded over Electronic Contract Signing, Certified E-mail, electronic payment and e-commerce. In this paper we present a strong fair hybrid non-repudiation protocol which works with all types of pairings. The protocol is modeled with an on-line TTP in the first round and then works optimistic in next rounds. The protocol offers stronger security by integration of Joux tri-partite key exchange and uses certificateless ID based signature and encryption methods. All the cryptographic methods used in the protocol are based on pairing based cryptography which can be implemented on all three types of pairings.

29

Authors: Emrah ERGÜL, Mehmet KARAYEL, Oğuzhan TİMUŞ, Erkan KIYAK

Attribute based approaches are commonly used in recent years instead of low level features for image classification which is one of the most important problems in the field of computer vision. The most important advantage of attribute based approach is that learning can be performed similar to human by using attributes which makes sense for people. In this study, unsupervised attributes are developed in order to avoid human related problems in supervised attribute learning. In our proposed work, the attributes are generated as random binary and relative definitions. The process of random attribute generation simplifies the data modeling when compared to other work in the literature. In addition, a major problem which is the increasing the numbers of attributes in attribute based approaches is eliminated owing to the increasing the numbers of attributes easily. Furthermore, attributes are selected more wisely using simple applicable algorithm to improve the discriminative capacity of randomly generated attribute set for image classification. The proposed approaches are evaluated with the other similar attribute based studies comparatively in the literature based on the same data set (OSR-Open Scene Recognition). Experiments show that noteworthy performance increase is achieved.

13

Authors: Tacettin Sercan PEKİN, Veysi İŞLER, Banu GUNEL

In computer graphics, proposing efficient and usable human-computer interaction design solutions is a challenging task. Well defined guidelines and principles are very useful for designers to design new solutions for systems. To create these guidelines and principles, firstly differences among systems should be identified. In this study, we focused on comparing large screen systems and mobile-size/desktop-size screen systems by observing users while they interact with all three different size screens. We noticed that there are physical differences between these systems such as viewing distance, pixel count and weight. We also noticed that there are different applications for different usage areas. According to this, eight types of differences are defined and usability differences are categorized into these difference types. As a result, we conclude that large touchscreen systems need separate interaction design guidelines and principles.

18

Authors: Ahmet DENKER

Reconstructions of the past with the advent of 3D computer graphics and high resolution rendering are increasingly produced and maintained in digital form, thus creating a legacy: Digital cultural heritage. Digital cultural heritage requires serious attention and is the subject of this paper. The reconstruction of the lost Ionic temples of the western shores of Aegean Sea is the main focus. The history of their construction, destruction and reconstruction loops are traced. The exceptional architects who had worked out the style and the principles of construction are looked into. Superstructures they created are studied with the aid of the accounts of the ancient writers, fragments in museums and surviving portions. Finally, their 3D reconstructions are realized so far as possible.

33

Authors: Yekta KILIÇ, Gürkan KOLDAŞ, Şafak Burak ÇEVİKBAŞ

The importance of data distribution increases in Multi-User Distributed Virtual Environments (DVEs) in parallel to both the complexity of virtual scenes and the number of clients. Main challenges are to load the relevant part of the scene, estimate and render visible primitives by keeping the frame rate fluent, since each user sees different part of the shared scene. In order to achieve the frame rate goal, data distribution should be well managed and optimization approaches based on network and visibility should be applied according to the requirements of each DVE. This is substantially handled by considering the area of interest for each user and estimating visible primitives as early as possible. This paper surveys the research on visibility culling, data management based on area of interest in DVEs and consequently summarizes thirteen implementations in the literature.

10

Authors: Mümtaz KARATAŞ, Gülşen AKMAN

Countering submerged targets using bistatic and multistatic sonobuoy systems is a fundamental problem in Anti-Submarine Warfare. A key question is: what is the best deployment geometry of sensors to successfully detect a submarine threat in a field of interest? The unique properties of these systems distinguish this problem from the conventional ones. This paper examines the optimum deployment strategies of bistatic sonobuoys against stationary or low speed targets.

18

Authors: Özgün SELVİ, Hasan AL-DULAİMİ

This study deals with one of the applications of parallel manipulator as a rehabilitation robot. This device is an over –constrained parallel manipulator 5 degree of freedom with 3 legs. This manipulator consists of a moving platform which is connected to a fixed base via three legs. Each leg is made of RRR(RR) (revolute) joints where the first three joint in all legs are parallel and the recent two joint are intersecting .Inverse kinematics of this device is solved by dividing manipulator into two sub-manipulators with the help of three imaginary joints placed at the intersection of platform joints with a direction parallel to base joints.

27

Authors: Özer ÖĞÜÇLÜ

A thermodynamic model has been developed and applied to predict the emission levels and performance of a spark ignition engine with using Exhaust Gas Recirculation (EGR) gas. The model simulates the full thermodynamic cycle of the engine and includes heat transfer, combustion, gas exchange process, thermal dissociation of water and carbon dioxide, and chemical equilibrium.

14

Authors: Cihan BAYINDIR

In order to maintain average power levels as well as high range resolution, phasecoded signals are used in radar and sonar signal processing. One of the most commonly used phase-coded signals is the linear frequency modulated chirp waveform. Various nonlinear frequency-modulated chirps are offered as alternatives to linear frequency modulated chirp. In this paper a new nonlinear frequency modulated chirp waveform is proposed. Properties like bandwidths, point spread functions and Fourier transforms are given for the proposed chirp signal. Synthetic imagery for spotlight imaging geometry is reconstructed by using the polar format and Stolt format processing techniques using the linear frequency-modulated (LFM) and proposed nonlinear frequency modulated chirp. Comparisons are presented, and it is shown that proposed waveform can improve the sonar image resolution.

15

Authors: İbrahim GİRGİN, Cüneyt EZGİ

Numerical methods are commonly used in engineering where the analytical results are not reached or as a support of experimental studies. Various techniques are being used as a numeritical method as finite difference, finite volume or finite elements, etc. In this study, numerical solutions are obtained for a circular fin of rectangular profile using finite difference method, and the results are compared to the analytical solutions. It is seen that the analytical solution and numerical results are found to be compatible.

19

Authors: Kerim GOZTEPE, Muammer KARAMAN, Hayrettin CATALKAYA

The integration of ERP systems is a primary issue for management and operation of enterprises. An enterprise resource planning (ERP) system is regarded a solution approach for any organization. Future operation and profitability of the enterprise or organization usually depends on selection most suitable ERP system. ERP is an information system and arrange different tools for management. This paper focuses on the ERP software selection procedure for any governmental organization applying fuzzy rule based decision making. Fuzzy rule based system depends on a rule depository and components for accessing and running the rules of proposed model. A governmental organization may request different solution approaches for its requirements. This research proposes an effective process to exploit what issues should be considered for ERP software selection in order to enhance enterprise competitive advantages.

18

Authors: H.Kemal ŞENYILMAZ, Gökhan CEYLAN, Veysel ALANKAYA, Alper KURULTAY

Light-weighted armor plates as being a discrete application of composite materials, are usually designed by finite elements programs such as ANSYSAUTODYN, and proven by real fire tests before procurement. In this study, effect of material model choose to the numerical results is presented. Considering the material data as an important function of the analysis, a standard material model is selected and AISI 4340 steel is used for all analyses. Besides the material deformation and crater dimensions on the impact area, heat as appearing of thermal energy and yield stress dissipation on the completed analyses, is presented to the readers.

24

Authors: Dr.Kerim GOZTEPE, Recep KILIC, Dr.Alper KAYAALP

With the increase of mobile devices and the implementation of the concept of “internet of things”, human beings began to live entirely in a cyberworld besides physical world. This unexpected expansion of cyberspace has caused a vulnerability to all kinds of cyber-attacks. Today, the number of attackers and correspondingly the number of attacks are increasing, but the attackers’ knowledge levels are diminishing. This inverse ratio in cyber threats force organizations and states to take more comprehensive security measures. Developed countries have begun to accept cyber space as a fifth operational domain after land, sea, air and space. The study reveals that designing cyber security agency for Turkey is a crucial issue in terms of cyber defense in depth for an effective homeland cyber security. In this paper, we suggest eight layered “defense in depth architecture” that is proposed “cyber security agency organization” for Turkey. We believe this structure provide more effective real-time information sharing between governmental organizations also.

26

Authors: Güzide Öncü E. PEKTAŞ

In the new century, the value and perception of the enterprises have changed due to the changes in consumers’ demands and needs. By virtue of this evolution, the enterprises have begun to attach importance to the value-satisfaction-royalty connection in the new contemporary merchandising concept. The retailers must promote their customers with this connection model and ensure creating satisfaction while meeting their needs. Regarding the marketing activities which enterprises follow in their changing retailing and store management, one of the most important factors that influence the customers’ buying behavior is the store atmosphere and pop advertising activities. In the literature section of this this study, store properties and pop advertising activities are analyzed; and in the application section, the impact of store atmosphere and pop advertising activities on buying behavior of consumers are analyzed with supermarket application in Istanbul.