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Archived Theses
Blind image quality metric for color images based on human vision system and deep CNN
In this study, a blind image quality metric (BIQM) for human vision system (HVS) has been developed by using deep convolutional neural network (CNN) for color images. The proposed quality metric consists of four stages. In the first stage, the colored image is transformed into YUV color space due to its compatibility with the HVS. In the second stage, pre-trained deep CNN is defined according to the noise type in the image (jpeg, gaussian, etc.). In the next step, the image whose quality is to be measured is denoised with deep CNN, and the image obtained as a result of this process is assumed to be the reference image. Thus, the problem is transformed into a full-reference quality measurement problem. In the last stage, each color channel (i.e., Y, U, and V) of the image whose quality is to be measured with the obtained reference image is measured by structural similarity (SSIM) method. The measurement results are weighted by considering the HVS. The experimental results show that the developed metric was able to sort the images that other quality metrics could not sort. Moreover, a survey was conducted with 100 participants to rank images in 3 different qualities, and the survey results support that the proposed method is compatible with the HVS. It also modified the SSIM which is normally a full-referenced method, to use as no-reference. Moreover, thanks to the proposed BIQM, more appropriate results are obtained compared to commonly used no-reference quality metrics. MATLAB codes and some images used for the proposed BIQM are available in the link: https://bit.ly/3NIrNBs
Interaction of parametrically designed low cavitated propeller and twisted rudder
Flow problems around objects are complex problems. These problems are solved using computational methods. The developing computer technology allows to verify expensive experiments using the finite element method. A certain part of the criteria in the design work of Naval Architecture is the field of hydrodynamics. Estimating the characteristics of the ship at the design stage that can be obtained by experimental analysis with the help of computational fluid dynamics (CFD) methods also contributes to the development of experimental methods. In ships, cavitation caused by the interaction of the propeller and rudder after a certain speed, reduces the hydrodynamic properties and working life of the propeller and rudder. In addition, cavitation is one of the main causes of vibration and noise in ships. The whole physics of cavitation cannot be revealed. Cavitation problems can be solved by utilizing numerical approaches. A cavitation flow solution can be made by making some assumptions and simplifications using the Computational Fluid Dynamics (CFD) method. Today, thanks to the rapidly developing technology, the transition of two-phase flow from the liquid phase to the vapor phase can be solved by modeling cavitation flow as a result of a bubble collapse using CFD analysis. The accuracy of the CFD method used in the study was obtained by comparing it with the current experimental results in the literature. The numerical analyses in the study were performed using the Reynolds Averaged Navier-Stokes (RANS) model in the Ansys CFX CFD software. The analyses were solved by using the simplified Rayleigh Plesset bubble equation based Zwart cavitation model added to the two-phase flow VOF (Volume of Fluid) method with the SST k-Omega turbulence model. In this study, the interaction of the rudder and the propeller was studied under the influence of cavitation. In this way, it is aimed to contribute to silence by reducing the cavitation caused by propeller – rudder interaction. In the study, it is aimed to minimize the cavitation caused by the Propeller-Rudder interaction in Naval Ships. For this purpose, CFD was validated by 6 different experiments in the literature. Calculations of the interaction of the low-cavitation propeller and the twisted rudder were performed using the obtained solution method. A 5-step improvement process was applied to the propeller geometry designed within the scope of the thesis. In terms of Blade Area Ratio (BAR), Pitch and Skewness of the propeller were improved. It was observed that cavitation decreased in the propeller blades as a result of reducing the pitch and increasing the skewness. The reduction of the propeller torque moment more than the thrust force helped to increase the propeller efficiency. With the improvement of the propeller made in the thesis, the cavitation rate in the existing propeller geometry was reduced compared to the original propeller geometry, and the efficiency was increased. The rudder geometry, which was passed through 4 different improvement stages, was positioned at downstream line of the resulting effective wake field of improved propeller Alternative rudders were positioned at downstream line of the improved propeller's effective wake field. When the literature is examined, the problem of course keeping is observed when using rudder geometries with increased maneuverability on ships. Due to the irregular flow from downstream line of the propeller, the rudder geometry generates lift force even in a straight position. This force creates cavitation on the rudder geometry. Cavitation was eliminated by twisting the rudder blade from middle of span. The lower chord of the rudder was twisted in the opposite direction in order to reduce the loss of maneuvering caused by twisting the rudder and the cavitation formed on its outer surface in the direction of twisting from the middle. It was seen that the double-twisted rudder at downstream line of the effective wake field of the propeller showed better performance in terms of maneuverability and cavity area than the non-twisted and single-twisted rudder.
Comprehensive analysis of integrated maritime spatial planning requirements in Black Sea
Human beings benefit from the oceans and seas in a wide variety of areas. Ocean and sea ecosystems provide many environmental, social and economic values and benefits with their biodiversity, resources and services. For this reason, it is very important to ensure the continuity of the life-supporting capacities of the marine realm. Today, however, the health of the oceans and seas is deteriorating rapidly. The oceans and seas are under the combined pressure of many impacts from human activities, ranging from overfishing to pollution, from climate change to acidification. We are doing tremendous damage to the oceans and seas that are the common property of all humanity and future generations, and if the current trend continues, the consequences for the planet will inevitably be disastrous. This trend can only be prevented by starting the responsible management and protection of marine areas and marine life. In this context, the concept of protection of the marine environment has undergone a significant transformation in recent years. Instead of the traditional approach focusing on a single sector such as pollution prevention or protection of a particular species, ecosystem-based approaches and integrated marine management tools have come to the fore, which include a broader conservation approach, take into account the unique characteristics of each marine area, and aim to protect the entire marine ecosystem. Maritime Spatial Planning (MSP) is one of these integrated planning tools and has been attracting more and more attention recently. Currently, around 100 countries are implementing MSP initiatives at different levels, from the initial phase to the evaluation and adaptation phase. In this study, the issues of who the stakeholders might be, in case of decision taken to implement MSP in the Turkish Black Sea marine areas, the conflict among the stakeholders, Türkiye's current legal and administrative infrastructure regarding the marine management were examined. Within the scope of the study, interviews with representatives of the maritime sector and a survey with 158 participants were conducted. As a result of the study, the maritime sector's approach and perception towards the holistic planning for management of Türkiye's Black Sea marine areas, the stakeholder engagement in a planning work, the conflict areas to be managed by planning, the authority to be assigned for planning and the spatial scale of the area to be covered by the plan were determined.
Dynamical analysis of chaotic circuits with computational algebra method
This study analyses a novel autonomous non- linear continuous-time system derived from Bao's simple third-order inductor-free memristive chaotic circuit for chaotic dynamics via computer algebra. Bao et al. designed the Chua memristor emulator with resistors, capacitors, and opamps to avoid the negative effects of the inductor [1]. This simple third-order inductor-free chaotic circuit utilizes reasonably functional discrete components, which are significant with the number of dynamically simplified elements for mathematical representation of chaotic behaviour. Our proposed model aims to overcome the negative long-term effects on the electrical properties of the capacitor and reveal experimental results depending on an additional variable that behaves like an electrical inductor. Numerical examples are given to study bifurcation properties in the modified chaotic circuit concerning the results with Lyapunov regimes and also to identify limit cycles of period-1, period-2, period-4, and chaotic attractors in the proposed circuit.
Developing a model to minimize repair dwell time based on condition monitoring system for major engine failure warning
Major engine failure may result in unwanted and unpredictable huge amounts of loss of income for the shipping companies. When the operation of the ship is limited or disabled as a result of a major engine failure, serious income loss occurs due to dwell time. The most prominent loss of the shipping company is the loss of rent income. As the repair period extends the economic loss of the shipping company gets bigger and bigger. Because time equals money for shipping companies in such a competitive market. Therefore, the most logical course of action is to handle repair activities in the operation area by having the repair done at the most available and nearest shipyard and acquiring the spare part from the nearest supplier. In case of failure that hampers the operation of the ship, the most crucial issue is to eliminate it as soon as possible. In this thesis, an integrated and systematic model is developed as a decision support tool to minimize dwell time for the repair activity based on condition monitoring system in case of major engine failure that the ship encounters at sea. In essence, the main objective of the model is to minimize repair dwell time. The study starts with a literature review and structured interviews carried out with experienced professionals in the shipping sector. To reach an optimal solution, a model is designed to handle the repair and spare part ordering processes jointly in the context of condition-based replacement with the help of Condition Based Monitoring (CBM) and Internet of Things (IoT) technologies. To achieve this an algorithm is developed and mathematically formulated. To simulate and verify the model a new software is developed by implementing this algorithm. Following the statistical analysis of the collected data, test input data is generated for input parameters for the test and verification of the model. Test runs are carried out with generated input data to evaluate the outputs of the model via developed simulation software. As a result of the test and verification process, it is confirmed that the model works as it is expected and the outputs and the results are reliable. Keywords: Maritime, shipping, repair, shipyard, spare part lead time, spare part ordering, Condition Based Monitoring (CBM), Internet of Things (IoT).
Identifying knowledge gaps in master level bridge team andresource management
Bridge team and resource management trainings and evaluations have been a hot topic for the maritime domain for a while. However, studies regarding these topics have largely been about methods of training and/or evaluation, as well as the effectiveness of these methods. A literature review was conducted and a research gap on evaluation results, and as such the knowledge gaps, of today's seafarers was identified. In this dissertation, a method of evaluation is proposed, prepared and carried out utilizing a maritime simulator complex. Firstly, the key topics of bridge team and resource management are identified. Then, simulator scenarios are prepared in order to test the performances of oceangoing masters in these key topics. After this, these scenarios are carried out by participants of oceangoing master rank. Following the simulator applications, a one way analysis of variation is done. This method is chosen due to the nature of the data being one independent variable with multiple dependent variables, and the one way analysis of variation lets us see any relationship between these. The results are then examined in order to determine the knowledge gaps of the participants. It is found that the participants have knowledge gaps in topics of communication, collision prevention and emergency handling. These topics are then more closely examined, and further research is suggested.
Chaotic system analysis with genetic algorithm approach
Dynamical analysis of epidemiological models gained significant attention from applied mathematicians after the Covid-19 pandemic caused a global catastrophe. Although studies involving the decision of the suitable model to describe the epidemiologic data and the predictive analysis of the disease spread have been carried out in-depth during this phase, studies that will expose the unrecognized dynamics through predictive analysis by investigating the algebraic properties of the models such as the invariant spaces, the center manifolds, and the Lyapunov functions in the general parameter space, still have the potential to contribute vastly to comprehending the spread dynamics. This work implements the triangular probabilistic distribution to an epidemic delay differential equation as a distributed continuous delay to determine the recovery rate based on characteristic model parameters. In this way, we propose a way to reduce the model parameters that need to be obtained during model fitting by defining generic coefficients derivable from field research and population characteristics.
Effects of organization culture and working conditions on job satisfaction and turnover rate in shipyards
According to recent studies, this high turnover rate has a devastating effect on workplace efficiency. In addition, the company will struggle to develop its corporate culture without its former trained and experienced employees. Thus, their existence in the market will become troubled. This institution becomes more vital especially in sector with challenging working conditions such as shipyards and where the cost of employee loss is high. However, according to literature "Working Conditions", "Intention to quitting job", "Organization Culture" and "Job Satisfaction" seem to be among the issues that institutions frequently have skipped in the last decades. Consequently, there has been a lack of research into how different forms of work motivation affect worker profiles in the shipbuilding industry. The goal of this research is to learn more about how shipyards' organizational culture and working conditions contribute to dissatisfaction among workers and the problem of excessive turnover. This study also aimed to identify the primary type of work motivation and explore relationships between types of job satisfaction and worker profile in shipyard workers. The research was conducted in shipyards located in two main shipyard industrial zones. Within the scope of the research, survey data were collected from 402 people by interview method. The hypotheses created were analysed with the Jamovi program. Among the most notable discoveries are the gender differences in job satisfaction and the predominance of a clan culture in the workplace at a Turkish shipyard.
Investigation of sound absorption properties of ethylene -vinyl acetate polymer based fiber-reinforced composites
For sound absorption materials to be effective in controlling underwater noise, they must have good sound absorption performance. Recently, materials based on polymers have been used to build submersible vessels that go through the deep ocean. Investigated are the sound-absorbing qualities of composite materials reinforced with fibers made of polymers. The solution processing technique is used to create ethylene-vinyl acetate (EVA) as a polymer material. EVA was prepared before being used as a ply inside a fiber-reinforced composite material made using the hand-lay-up method. In the 30 mm impedance tube, the sound absorption coefficient and sound transmission loss of EVA and polymer-based fiber-reinforced composite materials were determined in accordance with ASTM E2611-19/Transfer Matrix Method) and TSE ISO 10534-2(Transfer Function Method).
A model and simulation of a marine two stroke diesel engine with exhaust gas recirculation
The marine transportation industry covers the majority of the goods and commodity shipment around the globe in efficacious way, though it is operating in very demanding and challenging environments. Emissions from vessels is one of the key concerns especially coastal operation are involves hence, power production systems onboard vessels are now more in focus for the after treatments system. In addition to that from January 1st, 2023 the EEOI will be calculated on new and existing vessels to control and comply carbon footprint from operating vessels. As an emission abatement system in our focus was the exhaust gas recirculation (EGR) application on a marine two stroke engine. A Suez-max Crude Oil Tanker was considered as a subject in this study. Main propulsion engine was endeavo