Journal of Naval Sciences and Engineering

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.

12

Authors: Cüneyt EZGİ

Seawater is employed as the cooling media for a variety of heat exchanger applications on ships, offshore platforms, and at coastal locations. Although seawater is used extensively as a coolant medium, it has two main disadvantages: Corrosion and fouling. Selection of material must be met to ensure economical design and reliable performance.

16

Authors: Hüseyin Yavuz YÜCESOY, Prof. Dr. Murat VURAL

Beside the fact that austenitic stainless steels are used in various industrial applications, they are also widely used in naval applications. Especially, in shipbuilding sector, construction of corrugates and corrugate supports of tankers, chemical tankers, non-magnetic ships which are supposed to be working in polar areas and in construction of some naval war ships, as well as in piping systems of those, the need of having welded structures of non-magnetic stainless material has been increased. Within this scope, the prediction of the distortions of welded joints of austenitic stainless steel becomes more important and comes forward among the others. Most stainless steels are considered to have good weldability and may be welded by several processes including the arc welding processes, resistance welding, electron and laser beam welding, friction welding and brazing. For any of these processes, joint surfaces and any filler material must be clean. The coefficient of thermal expansion for the austenitic types is 50 % greater than that of carbon steel and this must be considered to minimize distortion. The low thermal and electrical conductivity of austenitic stainless steel is generally helpful in welding. Less welding heat is required to make a weld because the heat is not conducted away from a joint as rapidly as in carbon steel. In resistance welding, lower current can be used because resistivity is higher. Filler material for austenitic stainless steels should match or exceed the alloy content of the correct of the base metal. If a filler material of the correct match is not available, a filler metal with higher alloy content normally should be used. These filler metals can be in such a composition that a ferrite structure is obtained in order to prevent hot cracking. Filler metals for welding stainless steels are produced as coated electrodes, solid and metal cored wire and flux cored wire. In this study, it is aimed to analyze the welding distortions of austenitic stainless steels by using a sample steel (AISI 321 – 1.4541– UNS: S32100) and having it welded experimentally in two different positions (Butt Welding and Fillet Welding) and comparing the resulted deformations with Finite Element Method (FEM) modeling ones of the same joints.

20

Authors: Erinç DOBRUCALI

Computational fluid dynamics (CFD) is nowadays widely used to simulate smoke spread and temperature distribution as well as ventilation measures in a fire scenario. It allows improving fire fighting strategies and precaution measures in order to suppress the fire as fast as possible and help people to evacuate. In recent years, it has become apparent that computational fluid dynamics (CFD) can play an important and useful role in fire safety problems. The application of CFD to fire problems is also known as field modeling. Field modeling is based on the fundamental laws which govern the fire phenomena. Therefore, it is a valuable alternative for experimental investigations and empirical correlations and can be applied as a predictive tool. In this paper, field modeling is applied to tunnel fires in order to predict the critical ventilation velocity.