Journal of Naval Sciences and Engineering

217 - 239

Authors: Osman KABASAKAL, Alev MUTLU

In this study, we focus on the effect of word positions in unsupervised, graph-based keyword extraction. To this aim, we discuss the performance of four node-weighting procedures, namely Word Position (WP), Word Position Bidirectional (WPB), Sentence Position (SP), and Sentence Position Bidirectional (SPB). WP assigns higher weights to words that appear at the beginning of a text. WPB assigns higher weights to words that appear either at the beginning or end of a text. SP assigns higher weights to words that appear in the very first sentences of a text. SPB assigns higher weights to words that appear in sentences that are either close to the beginning or end of a text. Experiments conducted on six benchmark datasets show that WP and SP do not statistically differ. However, for datasets whose keywords appear early in the text WP performs better than SP with no statistical difference, while for datasets where keywords are evenly distributed in text SP statistically performs better than WP.

265 - 282

Authors: Özlem SEVİNÇ KAYA

In this study, the resonance production of the sextet scalar diquarks are studied for the FCC (Future Circular Collider) proton-proton collider with 100 TeV centre-of-mass planned to build at the European Organization for Nuclear Research, CERN. For the scalar diquarks, decay width and cross sections are calculated as a function of the diquark’s mass. Also, to separate the diquark’s signal from the background, the kinematic cuts are applied on diquarks mass and statistical significance calculations are obtained. As a result, at the FCC-pp, for the scalar diquark’s mass, discovery (5), observation (3) and exclusion (2) limit values are given. These mass limit values are compared with mass limit values of the Large Hadron Collider (LHC) with 7 TeV centre-of-mass energy and the High Luminosity-Large Hadron Collider (HL-HLC) with 14 TeV centre-of-mass energy.

309 - 341

Authors: Muhammet Ali YILMAZER, Burak YILDIZ

The second generation intact stability criteria (SGISC) have been developed by the International Maritime Organization’s (IMO) Subcommittee on Ship Design and Construction (SDC). The SGISC involve improving the current intact stability criteria by including dynamic movements of ships in waves. The criteria are structured around five failure modes, pure loss of stability being one of these. This paper presents sample calculations regarding the assessment of pure loss of stability for a Turkish navy tanker. The calculations involve two steps that this study explains: Level 1 and Level 2. In addition, Option A and Option B are used as solution methods for both levels. Minimum metacentric heights (GMmin) are calculated at the lowest draft (Option A) and at different wave crest locations alongside the ship (Option B) for Level 1. Values for the angle of vanishing stability, angle of loll, angle of stable equilibrium and maximum righting lever have been calculated from the GZ curves for Level 2. As a result, the subject ship was found not to be vulnerable to pure loss of stability. Level 1 results for both options are inconsistent due to Level 2 results being consistent.

377 - 393

Authors: Mehmet Burak KOÇAK, Barış BARLAS

Occupants in high-speed patrol boats are subject to impact forces due to various boat motions. These impact forces should be precisely calculated and accounted for when designing seats for occupants. Hull design and cruising speed are the most critical parameters that cause shock and impact on the boat during the journey. In addition, seat design and material also have a major effect on the impact level sensed by the occupant. In this study, Altair software (Hypermesh and Radioss) is used to build a sample Computer Aided Engineering (CAE) seat and occupant model for patrol boats. The occupant CAE model (50th percentile, Hybrid III) used in our study is already available in the software library and has been verified based on physical testing. During investigation, accelerations coming from reference studies are applied on the model and CAE results are investigated to understand occupant kinematics better. Different accelerations, seat foam thicknesses, and seat foam materials are tested numerically in CAE models. Based on the CAE results, strong relation between boat accelerations and impact level on occupant body regions are compared and verified. Acceleration levels and dummy kinematics was investigated with updates in seat foam design and materials. This study has been conducted in order to avoid injuries for patrol boat occupants and to shed a light on the importance of seat design.

413 - 428

Authors: Fatih ERDEN, Ayşe YAVUZ ERKAN, Ahmet Arda ÇOŞAN, Serkan AKSOY

The purpose of this study is analytical studying Initial-Boundary-Value Problem for the novel format of Maxwell’s equations in SI units. A modified version of the Evolutionary Approach to Electromagnetics (EAE) used herein. The problem is considered for the causal electromagnetic oscillations excited by a given external rectangular pulse signal, J(r,t) , in a hollow cavity with lossy metallic walls. The cavity volume V is finite and closed by a singly connected surface S with none of its inner angles exceeds π. Physically, cavity walls are lossy (completely or partially). Graphical results are exhibited demonstrating that the electromagnetic oscillations inside the cavity with metallic surface satisfy the causality principle.

1-25

Authors: Emre LEBLEBİCİOĞLU, Egemen SULUKAN, Tanay Sıdkı UYAR

Decreasing the usage of fossil fuels in the electricity production is a tough challenge for countries. The world is still depended on fossil fuels to generate electricity. Increasing the share of renewable energy systems in electricity production is significant in many aspects such as lower CO2 emissions, grid flexibility, decentralizing, etc. Nowadays, many countries shape their energy policies and strategies to use more renewable and indigenous resources. Turkey is one of these countries and has ambitions goals to use more domestic sources to produce electricity. Turkey generally aims to reduce the usage of imported energy sources in electricity generation. Thus this paper investigates the share of 50% renewable energy system (RES) simulation in the electricity production via the EnergyPLAN model. An energy system analysis was conducted in a 50% renewable scenario in 2023. The main target of this scenario is to perform a 50% renewable energy system in electricity production. A reference year is 2018 and the results of the 50% RES scenario were compared with a reference scenario. A main focus of this study is to investigate aspects of carbon emissions, RES share, and costs between the scenarios for the years 2018 and 2023.

43-75

Authors: Hülya CENGİZ, Eda TURAN

Coronavirus (COVID-19) pandemic has affected whole world in terms of health and global economics. As in all sectors, global maritime industry which comprises many work expertise and provides international work space for the employees, has also been stressed. For this importance, COVID-19 business impact survey on global maritime industry has been conducted during the first wave of the pandemic. Respondents of the research survey were working in a wide range of position and job alignments in the sector that are located in 21 countries all over the World. The purpose of this study is to determine the business effect of pandemic on global maritime industry. For this aim, a survey that consists of 36 questions has been conducted. These questions were initially related with descriptive ones that are firm characteristics and expertise. Then, ability of the companies while executing business operations under these situation has been investigated and the problems about financial structure as of liquidity, government & institutions assistance, transaction strategies, the actions of second wave, changes of employee, concern about future for company has been determined.

103-129

Authors: Tufan DEMİREL

Mobile Commerce is any transaction that involves the transfer of ownership or rights to use goods and services, which is initiated and/or completed by using mobile access to computer-mediated networks via an electronic device. Selection among m-commerce technologies is a multi-criteria evaluation problem having many conflicting and interactive criteria. In this study, 4 main criteria, which are economic trends, social trends, technological possibilities and data security and IT security, and 14 subcriteria are determined to evaluate m-commerce standards and technologies. Choquet integral is used to evaluate mobile commerce technologies with multiple criteria. The accuracy of the obtained results is examined through a sensitivity analysis

165-180

Authors: Zeynep Cansu TÜRKSELÇİ, Adnan AKKURT

Exoskeletons are technologies that are constantly developed to be used in different areas to reduce pain and periodic deformation felt under heavy loads. A great number of researchers and technology companies have been working on developing exoskeleton systems that augment human mobility to achieve several benefits in human life. This study includes current studies of passive exoskeletons which are specifically tested. The effects of passive exoskeleton systems reducing the load on the spine have been investigated for various lifting positions. In addition, reducing the biomechanical loads affecting the user's joints, muscles and soft tissues have been mentioned. In the conclusions section, the importance of researchers from the different branches to work on exoskeleton technology is emphasized.