Journal of Naval Sciences and Engineering

159-178

Authors: Gökhan ALTIN

In this study, spatial modulation (SM), which is an interesting and new approach for 5G and beyond communication systems, and deep neural network (DNN), which have also received great attention recently, are discussed, and a DNN-based receiver architecture for SM systems is proposed. Since the DNN will not be retrained until the channel change after training, it requires less processing, so it will be a potential receiver architecture for next-generation wireless communication and therefore SM systems. In this paper, a new DNN-based SM receiver is proposed to detect the transmitted symbols and the activated antenna index at the same time, and its performance is examined. As can be seen from the computer simulations, the DNN-based receiver offers low error performance with a small number of hidden layers and a low number of neurons in these layers. At the same time, even when the data rate is increased, the same DNN structure (without increasing the processing load) shows better/same performance than the receivers in the literature.

205-230

Authors: Özlem AKGÜN

The effect of field of view (FOV) angle on the positioning performance in a visible light positioning (VLP) system utilizing light-emitting diodes (LEDs) is examined. Due to its simplicity and low cost, the received signal strength indication (RSSI) technique with trilateration is used for distance measurement. Since being robust to noise sources, the optical code division multiple access (CDMA) is preferred for broadcasting the unique identification and location information of each LED at the same time. LEDs are deployed on the ceiling of a highly reflective room with the aim of providing homogenous and suitable lighting. The varying angle of FOV - 30o up to 88o with 2o increments - is considered in the photodetector (PD) to obtain the effect of FOV on six different VLP scenarios with respect to the number of LEDs. All scenarios have the non-line of sight (NLOS) channel models up to three reflections. Simulation results show that increasing the number of transmitters (Txs) decreases the distance error sensitivity to the changes in the ???????????????????????? angle. Consequently, indoor scenarios with increased Txs allow the use of low ???????????????????????? angles. Acceptable distance errors are obtained even in harsh conditions, i.e., near the corner of the room.

251-279

Authors: Gökay SEVGİ; Barış BARLAS; Uğur Oral ÜNAL

In this study, the viscous flow field around the mainsail of the DARPA Suboff AFF8 generic submarine fitted with two flow regulators in tandem configuration was investigated by means of computational fluid dynamics. An effective solution for the improvement of the mainsails of some of the current submarine classes of the Turkish Navy was aimed by covering the prepositioned periscopes by the flow regulators to avoid drag and vorticity increases due to the complex flow structure generated by these appendages and to provide a smoother flow topology. Three different NACA profiles with the same chord and span lengths were specified for regulating the flow. The effect of the NACA profile geometries on the hydrodynamic resistance and the flow field characteristics around the sail was demonstrated. It was shown that different profiles selected for the flow regulators considerably affect the computed resistance, velocity, pressure and vorticity characteristics of the flow field around the flow regulators. However, the flow structure at the side zones of the mainsail was not affected by the flow regulators. The profiles selected from NACA 6-digit and NACA 16-digit series give better hydrodynamic performance than their classical NACA 4-digit equivalent.

305-332

Authors: Tolga ÖNEL; Elif BOZKAYA

Network-Centric Warfare (NCW) envisions taking the advantage of information technology developments by replacing traditional war management strategies. It affects both the fast and accurate decision-making process by providing organization and information exchange between military forces in geographically different locations. Combat management systems help to manage and maintain components such as sensors, weapons, platforms to create the tactical picture. As a result of the threat evaluation with a network-centric approach, effective defense strategies can be developed through the problem of weapon assignment and sensor allocation among military forces. In this paper, threat evaluation concept and parameters are firstly explained, and the static and dynamic target-based weapon assignment and sensor allocation problem are defined. We also simulate a scenario for weapon target assignment (WTA) problem and compare different approaches. Then, the concept of NCW and the problems that may be encountered are detailed.

363-385

Authors: Beste DESTİCİOĞLU TAŞDEMİR

Project management is the process of planning activities in the project, estimating time and cost, assigning resources, making schedules, and performing controls. Project planning methods are used in project management to make time estimations. CPM, PERT, Gantt Charts, Fuzzy CPM, Fuzzy PERT are project planning methods. The CPM method is used when the activity durations are known certainly. However, in a project implemented for the first time, the duration of activity cannot be estimated certainly. In order to take this variability into account, the PERT method, which calculates the optimistic, probable and pessimistic durations of the activities, is used. Defence industry projects are of great importance as they are related to the defence of the country. In order for defence industry projects to be successful, the projects must be planned effectively. In this study, the planning process of a project realized for the first time by a company serving in the defence industry was examined. In the study, first of all, the activities of the project, their previous activities and duration are defined. In the study, the completion time of the project was calculated using CPM and PERT methods and the results were compared. In the last part of the study, the completion time of the project was calculated under different probabilities by using the PERT method.