• Structural Engineering and Mechanics
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• v.30 no.6
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• pp.679-698
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• 2008

On marine vessels, delicate instruments such as navigation radars are normally mounted on ship masts. However the vibrations at the top of mast where the radar is mounted often cause serious deterioration in radar-tracking resolution. The most serious problem is caused by the rotational vibrations at the top of mast that may be due to wind loading, inertial loading from ship rolling and base excitations induced by the running propeller. This paper presents a method of semi-active vibration control using magneto-rheological (MR) dampers to reduce the rotational vibration of the mast. In the study, the classical optimal control algorithm, the independent modal space control algorithm and the double input - single output fuzzy control algorithm are employed for the vibration control. As the phenomenological model of an MR damper is highly nonlinear, which is difficult to analyse, a back- propagation neural network is trained to emulate the inverse dynamic characteristics of the MR damper in the analysis. The trained neural network gives the required voltage for each MR damper based on the displacement, velocity and control force of the MR damper quickly. Numerical simulations show that the proposed control methods can effectively suppress the rotational vibrations at the top of mast.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.638-645
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• 2020

The mast is the highest structure in a naval ship, and various communication and radar antennas are installed to achieve long-range communications and line of sight. The U.S. and European navy currently are adopting integrated mast to their new ships, as it can reduce the Radar Cross Section(RCS) of the new ships and thus improve survivability of the ship. In this paper, when other navies adopt integrated masts on new ships, types of antennas, according to the cases that the antennas are integrated on the integrated mast or not, are analyzed. Also the types of antennas and transmission techniques for the radio communication equipments of the Korean Navy are analyzed in various frequency bands. For adopting an integrated mast on Korean new ships, the effects of the ship RCS according to the types of antennas, the possibility of integration the antennas and the integrated mast and considerations were presented.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.50-60
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• 2019

Recently, problems with excessive vibration of the radar masts of large bulk carriers and crude oil tankers have frequently been reported. This paper explores a design method to avoid the resonance of a radar mast installed on a large ship using various design of experiment (DOE) methods. A local vibration test was performed during an actual sea trial to determine the excitation sources of the vibration related to the resonant frequency of the radar mast. DOE methods such as the orthogonal array (OA) and Latin hypercube design (LHD) methods were used to analyze the Pareto effects on the radar mast vibration. In these DOE methods, the main vibration performances such as the natural frequency and weight of the radar mast were set as responses, while the shape and thickness of the main structural members of the radar mast were set as design factors. From the DOE-based Pareto effect results, we selected the significant structural members with the greatest influence on the vibration characteristics of the radar mast. Full factorial design (FFD) was applied to verify the Pareto effect results of the OA and LHD methods. The design of the main structural members of the radar mast to avoid resonance was reviewed, and a normal mode analysis was performed for each design using the finite element method. Based on the results of this normal mode analysis, we selected a design case that could avoid the resonance from the major excitation sources. In addition, a modal test was performed on the determined design to verify the normal mode analysis results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.300-302
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• 2019

The mast, which is the highest structure in warships, as well as merchant ships, is mainly equipped with radars and navigation lights. Especially, due to the nature of the naval vessels that operate many communication equipment, various kinds of antennas such as communication antennas and TACAN for aircraft guiding are installed in the naval mast. In addition to the complex structure of the mast itself, the installed antenna is a factor that greatly increases the RCS. Therefore, the mast technology for reducing the RCS is being developed and applied in the United States and Europe.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.7
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• pp.625-630
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• 2009

In this paper, we introduce the analysis and counter-measure of signal distortion of search radar equipped on the ship. Using ShipEDF program, the search radar's main antenna and ship structures are modeled in the view of electromagnetism. Ray tracing method is used for analysis of the search radar's radiation patterns in free space and ship condition. From analyzed radiation patterns, we can conclude that the search radar's signal distortion is due to radiation pattern distortion. We also analyze the surface current distribution of the mast to propose the counter-measure to reduce electro-magnetic field reflection of mast.

• Journal of Ocean Engineering and Technology
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• v.30 no.1
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• pp.57-67
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• 2016

As a new technical approach, an attempt was made to realize a photovoltaic system for an eco-environmental leisure ship by simultaneously actuating nine photovoltaic solar panels in association with the application of a sail-controlling system using wind energy. In this approach, the photovoltaic system consisted of a solar module, an inverter, a battery, and the relevant components, while the sail-controlling device was equipped with sail up/down and mast turning systems. The previously mentioned eco-environmental leisure ship utilizes a photovoltaic hybrid system that uses solar and wind energy as renewable energy sources. Furthermore, this research included a performance evaluation of the manufactured prototype, the acquisition of the purposed quantity values, and development of the purposed items. The significant items, including the sail up/down speed (seconds) and mast turning angle (degrees) were evaluated for a performance test. A wind direction sensitivity of 90% and maximum instant charging power of 900 W were also obtained in the process of the performance evaluation. In addition, the maximum sail time was also evaluated in order to acquire the optimum value. The performance evaluation showed that the prototype with a photovoltaic hybrid system was suitable for sailing an eco-environmental leisure ship using solar and wind energy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.843-850
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• 2012

To satisfy the operational requirements of surveillance radar and the operational concept of a ship combat system, an active-array-type antenna was designed using solid-state transmitters and receivers. The arrangement of the constituent electronic components of the antenna system, considerably large in size, and therefore, the antenna needs to be housed in a box. The rotational antenna system installed on a ship mast is installed in a sealed housing to protect the interior equipment from environmental conditions. The outer shape of the housing is that the antenna should be capable of rotating normally despite strong winds. Furthermore, in recent times, designs with low radar cross section (RCS) have attracted attention from the viewpoint of improving the stealth of the ship. In this light, four types of models are proposed for the outer shape design of the antenna system, and they are investigated from the viewpoint of low RCS design as well as wind load.

• Journal of IKEEE
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• v.24 no.2
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• pp.453-460
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• 2020

This paper, UHF band integrated communication antenna for ship communication is designed as a flat type that can be mounted on the integrated mast among integrated communication antennas such as integrated communication, ship communication, broadcasting, and telephone of the ship. The unified mast mounted antenna is an integrated communication antenna applied to the Navy's KDDX, which is an optimized type of integrated communication antenna including a 'composite slope' structure including operational capability, survivability, and improved operability and maintainability. The existing rotary radar and a plurality of monopole-type communication antennas were changed from an irregularly attached shape to the mast exterior to an integrated mast shape including a flat-type integrated communication antenna. the radar reflection area index (RCS) is significantly lowered and compared to overseas products. The goal is to develop a gain broadband antenna.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.117-122
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• 2020

In this paper, we study the electromagnetic interference in adjacent antenna aperture of multi-function radar for Integrated MAST of naval ship, which is operating plural radars, with test result of two different X-band antennas. Two antennas is placed in the test fixture copying the part of Integrated MAST for the experiment. The test figure is modeled to see the electromagnetic interference when antenna beam is steered by using electromagnetic analysis tool. Also, 6 test scenarios is determined to verify experimentally and each test scenario is run in an anechoic chamber. At the test antenna #1 radiates a pulse signal and the signal from the antenna #2 is stored and analyzed in the optic data format through a receiving device. Based on the result, the effect of electromagnetic interference is suggested when multi-function radars in the Integrated MAST are operating in adjacent distance.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.5
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• pp.703-708
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• 2010

Recently, the development of the Marina port is determined as a national plan, and a variety of leisure boats and facilities on the field has been of critical interest. In particular, yachts are designed and produced mostly at small shipbuilding companies and research institute. The regulation and historic data, however, about the safety of structure are not readily available. Therefore, it is required to evaluate the strength of ship structure. This paper deals with the estimation of local strength of 40 feet sailing yacht by using finite element analysis. The forebody, mast and connection parts of a FRP yacht structure are evaluated. In addition, the results are compared with the regulation of Lloyd's register and Korean register.