Erden F.,Turkish Naval Academy
Turkish Journal of Physics | Year: 2017
The energetic characteristics of cylindrical medium-free time-domain waveguide fields are solved within the framework of the evolutionary approach to electromagnetics. Solving the boundary-eigenvalue problem for transverse Laplacian yields a configurational basis in the waveguide cross section. Elements of the basis depend on transverse coordinates, whereas the modal amplitudes depend on the longitudinal coordinate, z; and time, t. Solving the resulted Klein-Gordon equation yields a basis for analysis of the modal amplitudes. Exact solutions for the amplitudes of TE-modes are obtained, and the energetic field characteristics are derived in accordance with the causality principle. © 2017 Tübitak.
Mutlu A.,Middle East Technical University |
Senkul P.,Middle East Technical University |
Kavurucu Y.,Turkish Naval Academy
Knowledge-Based Systems | Year: 2012
Due to the increase in the amount of relational data that is being collected and the limitations of propositional problem definition in relational domains, multi-relational data mining has arisen to be able to extract patterns from relational data. In order to cope with intractably large search space and still to be able to generate high-quality patterns, ILP-based multi-relational data mining and concept discovery systems employ several search strategies and pattern limitations. Another direction to cope with the large search space is using parallelization. By parallel data mining, improvement in time efficiency and scalability can be provided without further limiting the language patterns. In this work, we describe a method for concept discovery with parallelization on an ILP-based concept discovery system. The non-parallel algorithm, namely Concept Rule Induction System (CRIS), is modified in such a way that the parts that involve high amount of query processing, which causes bottleneck, are reorganized in a data parallel way. The resulting algorithm is called, Parallel CRIS (pCRIS). A set of experiments is conducted in order to evaluate the performance of the proposed method. © 2011 Elsevier B.V. All rights reserved.
Gonca G.,Yildiz Technical University |
Dobrucali E.,Turkish Naval Academy
Renewable Energy | Year: 2016
This study reports the effects of engine load and biodiesel percentage on the performance of a diesel engine fueled with diesel-biodiesel blends by experiments and a new theoretical model based on the finite-time thermodynamics (FTT). In recent years, biodiesel utilization in diesel engines has been popular due to depletion of petroleum-based diesel fuel. In this study, performance of a single cylinder, four-stroke, direct injection (DI) diesel engine fueled with diesel-biodiesel mixtures has been experimentally and theoretically investigated. The simulation results agree with the experimental data. After model validation, the effects of engine load and biodiesel percentage on engine performance have been parametrically investigated. The results showed that, effective power increases constantly, effective efficiency increases to a specified value and then starts to decrease with increasing engine load at constant biodiesel percentage and compression ratio. However, effective efficiency increases, effective power decreases to a certain value and then begins to increase with increasing biodiesel percentage at constant equivalence ratio and compression ratio. © 2016 Elsevier Ltd.
Ezgi C.,Turkish Naval Academy
International Journal of Refrigeration | Year: 2014
Absorption heat pump (AHP) systems are cleaner and more efficient energy solutions than vapour-compression heat pump systems for heating and cooling on board naval surface ships. Thermal management is a critical requirement for naval surface ships and submarines as well as commercial vessels and land-based industrial plants. Approximately 25% of a ship's thermal load is removed through the heating, ventilation and air conditioning (HVAC) system. In this study, design and thermodynamic analysis of a water-lithium bromide (H2O-LiBr) AHP as an HVAC system for a naval surface ship application are presented and compared with those of a vapour-compression heat pump. © 2014 Elsevier Ltd and IIR. All rights reserved.
Fuzzy AHP based decision support system for technology selection in abrasive water jet cutting processes [Sustav potpore neizrazitom AHP utemeljenom odluĉivanju u izboru tehnologije u procesu rezanja abrazivnim vodenim mlazom]
Tozan H.,Turkish Naval Academy
Tehnicki Vjesnik | Year: 2011
Due to its remarkable abilities, the studies about abrasive water jet cutting process are rapidly increased in recent years. One of the main problems about this brilliant technology is to find the appropriate technology to use in cutting processes to increase surface quality. In this paper a fuzzy/crispAHPbased decision support system is proposed for the selection of appropriate technology for the cutting process of titanium. An application of the proposed models and their results are presented with comparisons. The results illustrated that both methods used in decision support pointed out the same technology with similar weights.
Alankaya V.,Turkish Naval Academy
Medziagotyra | Year: 2016
Establishing the survivability for armed forces and police teams, attentive solutions are needed owing to the damage mechanism of fragments that have more kinetic energy than traditional bullets. Nevertheless, determining the damage capability of composite laminates against fragment impact at ballistic velocities is a challenging issue because of the difficulty in determining elastic stiffness of the armor due to the complex damage modes, which can occur in composites through impact phenomenon. Fire tests are generally considered to be the best validation method for procurement transactions of customers. This study presents the effects of impact velocities for rubberized aramid plates on the basis of computerized tomography scans taking into consideration composite failure modes. Additionally, the impact damage of plates at different ballistic velocities is presented, supported by real test reports focusing on the penetrating prevention capability and a predictive equation of ballistic limit velocity for rubberized aramid plates resisting. 30 caliber FSP is developed. © Kauno Technologijos Universitetas. All rights reserved.
Erden F.,Turkish Naval Academy
2015 23rd International Conference on Software, Telecommunications and Computer Networks, SoftCOM 2015 | Year: 2015
Goal of this study is to present an evolutionary approach for the analysis of waveforms which can be excited by a pulse signal in a rectangular cavity filled with a plasma and bounded by perfect electric conductor surfaces. Maxwell's equations with time-derivative supplemented with initial conditions have been solved under the principle of causality. Dynamic version of the Ohm's law for plasma was involved in the system of Maxwell's equations as the constitutive relation between the plasma current vector and the electric field. Solutions have been obtained explicitly in the form of convolution integrals. © 2015 University of Split, FESB.
Kavurucu Y.,Turkish Naval Academy
International Journal of Data Mining and Bioinformatics | Year: 2015
Subgraphs that occur in complex networks with significantly higher frequency than those in randomised networks are called network motifs. Such subgraphs often play important roles in the functioning of those networks. Finding network motifs is a computationally challenging problem. The main difficulties arise from the fact that real networks are large and the size of the search space grows exponentially with increasing network and motif size. Numerous methods have been developed to overcome these challenges. This paper provides a comparative study of the key network motif discovery algorithms in the literature and presents their algorithmic details on an example network. Copyright © 2015 Inderscience Enterprises Ltd.
Dobrucali E.,Turkish Naval Academy
Energy | Year: 2016
In this paper, a thermodynamic analysis for an irreversible Otto-Miller Cycle (OMC) has been presented by taking into consideration heat transfer effects, frictions, time-dependent specific heats, internal irreversibility resulting from compression and expansion processes. In the analyses, the influences of the engine design parameters such as cycle temperature ratio, cycle pressure ratio, friction coefficient, engine speed, mean piston speed, stroke length, inlet temperature, inlet pressure, equivalence ratio, compression ratio, and bore-stroke length ratio on the effective power, effective power density and effective efficiency have been investigated relations with efficiency in dimensionless form. The dimensionless power output and power density and thermal efficiency relations have been computationally obtained versus the engine design parameters. The results demonstrate that the engine design and running parameters have considerable effects on the cycle thermodynamic performance. of a OMC. The results showed that the cycle efficiency increased up to 50%, as cycle temperature ratio increases from 6 to 8, the effective power raised to 11 kW from 5 kW at this range. Other parameters such as engine speed, mean piston speed, cycle pressure ratio affected the performance up to 30%, positively. However, friction coefficient and inlet temperature have negative effect on the performance. As the friction coefficient increases from 12.9 to 16.9, a performance reduction was seen up to 5%. Increase of the inlet temperature abated the performance by 40%. © 2016 Elsevier Ltd.
Ergul E.,Turkish Naval Academy |
Arica N.,Turkish Naval Academy
Proceedings - International Conference on Pattern Recognition | Year: 2010
We propose a scene classification method, which combines two popular methods in the literature: Spatial Pyramid Matching (SPM) and probabilistic Latent Semantic Analysis (pLSA) modeling. The proposed scheme called Cascaded pLSA performs pLSA in a hierarchical sense after the soft-weighted BoW representation based on dense local features is extracted. We associate spatial layout information by dividing each image into overlapping regions iteratively at different resolution levels and implementing a pLSA model for each region individually. Finally, an image is represented by concatenated topic distributions of each region. In performance evaluation, we compare the proposed method with the most successful methods in the literature, using the popular 15-class-dataset. In the experiments, it is seen that our method slightly outperforms the others in that particular dataset. © 2010 IEEE .