Scientific Bulletin of Naval Academy

6

Authors: Sorin Draghici, Gabriel Jiga, Sebastian Vintila, Radu Mihalache, Horia Alexandru Petrescu and Anton Hadar

The steady increase in the use of composites has brought benefits in many areas. Polymer Matrix Composite (PMC) is a material consisting polymer (resin) matrix combined with a fibrous reinforcing dispersed phase. Polymer Matrix Composites are very popular due to their low cost and simple fabrication methods. This paper aims to validate thru finite element method the structural integrity of a composite gas turbine rotor and establish its benefits and disadvantages compared to a steel alternative. Composites provide the advantages of lower weight, greater strength and higher stiffness and the advantage of prepreg technology.

7

Authors: Vlad Mocanu, Petrica Popov and Vasile Dobref

In this paper, the authors present new ways of using drones in the marine and offshore environments. The article includes the presentation of the main constructive electrical elements of a marine floating buoy, which play the role of charging base for an unmanned aerial drone. Also, are highlighted the main losses of the system’s components, what should have been taken into account when choosing the size of such an independent energy source, as well as the main steps for energy source design.

7

Authors: Simona-Vasilica Oprea and Adela Bâra

Blockchain is a promising technology for local trading of the electricity. It has specific components, such as smart contracts, data ledger, consensus, and provides many benefits for both buyers and sellers because they are obtaining/generating electricity at better prices compared with the electricity from the public grid. This practice leads to a better integration of renewable energy sources, increasing the appetite for new local generation sources and storage facilities, transparency and trading opportunities for all market players. Grid operators also benefit from blockchain since the grid loading will be reduced as the grid does not have to transmit or distribute electricity from large power plants located far away from consumption place. In the end, the market players will benefit from reducing the grid loading and alleviating the congestions as onerous investment in grid infrastructure is avoided. In this paper, we will analyse the advantages of different electricity market mechanisms for trading and settlement. Several auction mechanisms such as pay-as-bid, uniform price, generalised second price or Vickrey-Clarke-Groves are taken into account as feasible options for local markets and peer-to-peer trading.

8

Authors: Mircea Dorin Vasilescu

The purpose scope of this paper is to analyse the economic aspects of making 3D printing components for the development of machine for experimental devices or stands used in laboratory or industrial activity. The author of this paper intends to make a clarification related to the approach of the productive economic aspects through the production of components through the additive technology of SLA type. The work is structured in 5 chapters. For the generation of the constructive elements, a laser printer will be used, where the components will be generated on the bottom-up principle. The analysis will be carried out both from a constructive and functional point of view, taking into account possibilities of component design and their realization. The next chapter is allocated to analysing how to perform the printer's command program and to check the part structure. Part of this chapter is devoted to the way and role of the elements of orientation and support of the component that is being made. The fourth chapter presents the economic calculation program made with practical applications related to the parts generated in the previous chapter. The last chapter is allocated to the conclusions and comparisons from the technological-economic point of view compared with other specific technologies for generating the analysed parts.

8

Authors: Deniz Ünsalan, Kunsel Izet-Ünsalan and K. Turgut Gürsel

The long existent worldwide trend for large scale hydroelectric power plants, relying on dams are now under severe criticism for the large areas their reservoirs occupy, which are often fertile agricultural areas and sometimes flood cultural heritage sites. However, there are also environment-friendly alternatives for hydroelectric power production, which are capable to obtain energy from small scale streams with relatively low heads. Such smaller scale sources with low cost facilities can be used for electric production by alternative schemes that use small streams, irrigation canals and divertions from rivers, tidal pools, overtopping wave energy converters and urban wastewater. One of the recent types of such plants are the gravity vortex turbines that use the naturally occurring “sink vortex” draining such water. They are highly efficient and able to obtain energy from sources with flow rates as low as 1 m3/s and heads as low as 0.80 m. Such water sources are abundant in most of the rural areas and it is possible to obtain either an important part or the total need of the energy requirement of the nearby communities with such systems. Gravity vortex turbines have low costs due to their simple structure and are easy to maintain. They can also be implemented for overtopping wave energy and tidal energy systems, as well as recovery units of pumped energy storage schemes. The purpose of this paper is to propose relations for the design and parametric analysis to size the relevant parts of the plant- the pool and the turbine. Potential flow is assumed throughout the analysis. Attempts to obtain optimized relations between the relative sizes and rotational speeds for the pool, water source, turbine are made and inputs for preliminary design are obtained.

8

Authors: K. Izet-Ünsalan and Melisa Ünsalan

The data used in this paper were collected by the participants of the first MOOC (Massive Open Online Course) “GPS: An Introduction to Satellite Navigation, with an interactive Worldwide Laboratory using Smartphones”, offered by Stanford University through Coursera, taught by professors Per Enge and Frank van Diggelen. More than 1000 users worldwide determined their position in open and urban areas and submitted their results, which were compared with the claimed accuracy. Additionally, the authors of the MOOC have proposed the “Law of Urban Multipath” that predicts GNSS position accuracy based on heights of buildings in the proximity. In this study, the aforementioned data was analysed to obtain practical results that can be used to improve the accuracy of simple smartphone and tablet based GNSS measurements. In the undergraduate course taught by the first author, this methodology was used as a laboratory tool for the improvement of navigation and positioning skills of the students.

8

Authors: Dumitru Iorgulescu and Gheroghe Samoilescu

The paper presents the advantages and disadvantages of the electric propulsion and the speed adjustment of the electric motors used for it. Using the speed regulation methods of D.C. and C.A. motors, we analyze the role of physical size that appear in mathematical relations. The speed adjustment methods for three-phase asynchronous motors are: changing the number of pairs of poles; alteration the frequency of the supply voltage; turning of the slip that is realized by the variation of the rotor resistance and alteration of the supply voltage. The voltage alteration is only effective during the load operation. The speed control is analyzed by modifying the number of pairs of poles, adjusting the speed by changing the frequency of the supply voltage, adjusting the speed by modifying the supply voltage, and adjusting the speed by rheostat adjustment. The speed adjustment of synchronous motors can only be done by varying the frequency of the supply voltage or by changing the number of pairs of poles. The role of adjusting the speed of the electric motors in propulsions is presented .

8

Authors: Olha Dimoglova , Sergiy Maksymov and Leonid Herhanov

Strategic approaches to the professional image formation of water transport professionals should be considered using a defined model of economic development for water transport companies, followed by a description of the recommended measures. The algorithm of transport company development model, as a rule, has its economic sectoral features where the company operates. However, in this approach, important elements of the participation of human resources in the implementation of the company development strategy, which, in particular, suggest possible variations of combinations of managerial decisions. Thus, the transport industry is no exception. The authors of the article propose the procedure and main stages in the strategy development for the professional image formation in terms of introduction of the model of water transport companies development, and introduce new definition of the concept "strategic role of professional image in the model of water transport companies development " and use it as a tool for internal analysis of transport company as a significant complement to the definition of the term "transport company development strategy". The existing experience of research on the problems of professional image influence on the final results of activity in the maritime industry companies taking into account differences of transport services are considered in the article. It is clarified that the analysis of the market in which the transport company operates is determined by the definition of the company's field of activity, research of competitors in this field, strategic assets and strategic competence. Considering that the strategy of transport company development is the mutualism of the main goals of the company and the system of management decisions, the authors of the research have identified the main stages of strategic analysis of the transport company activity, the main ways and requirements for the acquisition of strategic competence.

9

Authors: Dragoș Simion, Alexandra Purcărea, Alexandru Cotorcea and Florin Nicolae

The importance and the role of the maintenance process are based on keeping the equipment and systems in an operative state of readiness. On the other hand, the knowledge of legislative framework, as well as the learning the practical skills lead to the successful application of the maintenance programs within the organizations. Regarding these aspects, the present paper addresses the topic of maintenance onboard ships. The general legislative framework for management and execution of the maintenance process specific to the maritime domain is presented, as well as the methods implemented onboard ships. It is described how to perform the maintenance of the equipment for a special ship using a computer maintenace management softwere. The study takes into account the constructive features, the equipment and the missions of the ship.

12

Authors: Dmytro Kachur, Vladimir Golikov, Sharai Natalia and Vitaly Smolets

Every day people try to find the cheapest and fastest type of transport, that can bring them or their goods from one place to another in shortest time. This article consist of showing the difference in usage efficiency between WIG crafts, airplane and bus on the way from Odessa to Istanbul and efficiency, which based on economic model, of transferring different types of cargoes on different types of transports depends of the time of the year.