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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Engineering
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Journal DOI :
Korean Society of Marine Engineers
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Volume & Issues
Volume 39, Issue 10 - Dec 2015
Volume 39, Issue 9 - Nov 2015
Volume 39, Issue 8 - Oct 2015
Volume 39, Issue 7 - Sep 2015
Volume 39, Issue 6 - Jul 2015
Volume 39, Issue 5 - Jun 2015
Volume 39, Issue 4 - May 2015
Volume 39, Issue 3 - Mar 2015
Volume 39, Issue 2 - Feb 2015
Volume 39, Issue 1 - Jan 2015
Selecting the target year
A Study on the Measurement and Analysis of Whirling Vibration Behavior of Marine Propulsion Shafting System using Gap-sensors
Sun, Jin-Suk ; Han, Tae-Min ; Lee, Kang-Ki ; Kim, Ue-Kan ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 130~135
DOI : 10.5916/jkosme.2015.39.2.130
Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational rpm range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering from operating rpm up to target rpm, however, the range is un-measurable generally. In order to resolve the measurement issue, this study shows the measuring method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration.
A Study on Velocity Profiles between Two Baffles in a Horizontal Circular Tube
Chang, Tae-Hyun ; Lee, Chang-Hoan ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 136~142
DOI : 10.5916/jkosme.2015.39.2.136
The shell and tube heat exchanger is an essential part of a power plant for recovering transfer heat between the feed water of a boiler and the wasted heat. The baffles are also an important element inside the heat exchanger. Internal materials influence the flow pattern in the bed. The influence of baffles in the velocity profiles was observed using a three-dimensional PIV (Particle Image Velocimetry) around baffles in a horizontal circular tube. The velocity of the particles was measured before the baffle and between them in the test tube. Results show that the velocity vectors near the front baffle flow along the vertical wall, and then concentrate on the upper opening of the front baffle. The velocity profiles circulate in the front and rear baffle. These profiles are related to the Reynolds number (Re) or the flow intensity. Velocity profiles at lower Re number showed complicated mixing to obtain the velocities and concentrate on the lower opening of the rear baffle as front wall. Numerical simulations were performed to investigate the effects of the baffle and obtain the velocity profiles between the two baffles. In this study, a commercial CFD package, Fluent 6.3.21 with the turbulent flow modeling, k-
are adopted. The path line and local axial velocities are calculated between two baffles using this program.
A Study on Power Performance of a 1kW Class Vane Tidal Turbine
Yang, Changjo ; Nguyen, Manh Hung ; Hoang, Anh Dung ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 143~151
DOI : 10.5916/jkosme.2015.39.2.143
Recently, tidal current energy conversion is a promising way to harness the power of tides in order to meet the growing demands of energy utilization. A new concept of tidal current energy conversion device, named Vane Tidal Turbine (VTT), is introduced in this study. VTT has several special features that are potentially more advantageous than the conventional tidal turbines, such as propeller type tidal turbines. The purpose of this study on VTT is to analyze the possibility of extracting the hydrokinetic energy of tidal current and converting it into electricity, and evaluate the performance of turbines for various numbers of blades (six, eight and twelve) using Computational Fluid Dynamics (CFD). At various tip-speed ratios (TSR), the six-bladed turbine obtains the highest power and torque coefficients, power efficiency is up to 28% at TSR = 1.89. Otherwise, the twelve blade design captures the smallest portion of available tidal current energy at all TSRs. However, by adding more blades, torque extracted from the rotor shaft of twelve-bladed turbine is more uniform due to the less interrupted generation of force for a period of time (one revolution).
A Study on Effects of Partial Shading on PV System applied to the Offshore Plant
Lee, Ji Young ; Yang, Hyang Kweon ; Oh, Jin Seok ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 152~158
DOI : 10.5916/jkosme.2015.39.2.152
Unlike photovoltaic systems installed on land, photovoltaic systems applied to the offshore plant have the characteristic that is installed in a limited space. For single point mooring plant, it is advantageous in terms of a reliable power supply to be installed in different directions of photovoltaic panels, because it is not possible to identify the position of the sun by rotation of the plant itself. Differences of installation angle between photovoltaic panels make a difference of the intensity of radiation irradiated on each photovoltaic panel, and it brings loss of generation quantity due to the partial shading. In order to provide a photovoltaic system suitable for offshore plant, the modeling which contains multiple photovoltaic panels controlled by single controller is performed. Then, it was examined how the output characteristics of the photovoltaic system change about the difference of the intensity of radiation that varies depending on the altitude of the sun. Finally, through the simulation, a development model of the photovoltaic system which is suitable for offshore plant is suggested.
Stability Analysis for the Deployment of Unmanned Surface Vehicles
Dharne, Avinash G. ; Lee, Jaeyong ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 159~165
DOI : 10.5916/jkosme.2015.39.2.159
Motion control schemes are generally classified into three categories (point stabilization, trajectory tracking, and path following). This paper deals with the problem which is associated with the initial deployment of a group of Unmanned Surface Vehicle (USVs) and corresponding point stabilization. To keep the formation of a group of USVs, it is necessary to set the relationship between each vehicle. A forcing functions such as potential fields are designed to keep the formation and a graph Laplacian is used to represent the connectivity between vehicle. In case of fixed topology of the graph representing the communication between the vehicles, the graph Laplacian is assumed constant. However the graph topologies are allowed to change as the vehicles move, and the system dynamics become discontinuous in nature because the graph Laplacian changes as time passes. To check the stability in the stage of deployment, the system is modeled with Kronecker algebra notation. Filippov's calculus of differential equations with discontinuous right hand sides is then used to formally characterize the behavior of USVs. The stability of the system is analyzed with Lyapunov's stability theory and LaSalle's invariance principle, and the validity is shown by checking the variation of state norm.
Wireless Ultrasonic Anemometer and Anemoscope Data-Logger System based on the Web
Yim, Jae-Hong ; Kang, Young-Gwan ; Lee, Woo-Jin ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 166~171
DOI : 10.5916/jkosme.2015.39.2.166
Recently, the international standard RS-422 serial communication, which was primarily designed for the communications between micro-controllers, has been used as a communication method on the ship. However, as the NMEA (National Marine Electronics Association) 2000 standardization progresses recently, a high-speed Ethernet-based communication environment is expected to be an alternative communication method instead of the RS-422 gradually. In addition, the ship's main instrumentation equipment with versatility and convenience is implemented to control devices as monitoring and controlling tools. This paper describes an implementation of wireless ultrasonic anemometer and anemoscope data processing and logger system using PC network, where the control processing equipment such as a separate operational console, data-logger, and indicator is required for the system. For these, the related element technologies to implement ultrasonic anemometer and anemoscope data processing system are expressed as a functional modules, and the NMEA 2000 standard certified data-logger system is implemented without the separate operational console.
Analyzing Errors in Bilingual Multi-word Lexicons Automatically Constructed through a Pivot Language
Seo, Hyeong-Won ; Kim, Jae-Hoon ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 172~178
DOI : 10.5916/jkosme.2015.39.2.172
Constructing a bilingual multi-word lexicon is confronted with many difficulties such as an absence of a commonly accepted gold-standard dataset. Besides, in fact, there is no everybody's definition of what a multi-word unit is. In considering these problems, this paper evaluates and analyzes the context vector approach which is one of a novel alignment method of constructing bilingual lexicons from parallel corpora, by comparing with one of general methods. The approach builds context vectors for both source and target single-word units from two parallel corpora. To adapt the approach to multi-word units, we identify all multi-word candidates (namely noun phrases in this work) first, and then concatenate them into single-word units. As a result, therefore, we can use the context vector approach to satisfy our need for multi-word units. In our experimental results, the context vector approach has shown stronger performance over the other approach. The contribution of the paper is analyzing the various types of errors for the experimental results. For the future works, we will study the similarity measure that not only covers a multi-word unit itself but also covers its constituents.
Improved Adaptive Smoothing Filter for Indoor Localization Using RSSI
Kim, Jung-Ha ; Seong, Ju-Hyeon ; Ha, Yun-Su ; Seo, Dong-Hoan ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 179~186
DOI : 10.5916/jkosme.2015.39.2.179
In the indoor location estimation system, which has recently been actively studied, the received signal strength indicator contains a high level of noise when measuring the signal strength in the range between two nodes consisting of a receiver and a transceiver. To minimize the noise level, this paper proposes an improved adaptive smoothing filter that provides different exponential weights to the current value and previous averaged one of the data that were obtained from the nodes, because the characteristic signal attenuation of the received signal strength indicator generally has a log distribution. The proposed method can effectively decrease the noise level by using a feedback filter that can provide different weights according to the noise level of the obtained data and thus increase the accuracy in the distance and location without an additional filter such as the link quality indicator, which can verify the communication quality state to decrease the range errors in the indoor location recognition using ZigBee based on IEEE 802.15.4. For verifying the performance of the proposed improved adaptive smoothing filter, actual experiments are conducted in three indoor locations of different spatial sections. From the experimental results, it is verified that the proposed technique is superior to other techniques in range measurement.
Robust Relative Localization Using a Novel Modified Rounding Estimation Technique
Cho, Hyun-Jong ; Kim, Won-Yeol ; Joo, Yang-Ick ; Seo, Dong-Hoan ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 187~194
DOI : 10.5916/jkosme.2015.39.2.187
Accurate relative location estimation is a key requirement in indoor localization systems based on wireless sensor networks (WSNs). However, although these systems have applied not only various optimization algorithms but also fusion with sensors to achieve high accuracy in position determination, they are difficult to provide accurate relative azimuth and locations to users because of cumulative errors in inertial sensors with time and the influence of external magnetic fields. This paper based on ultra-wideband positioning system, which is relatively suitable for indoor localization compared to other wireless communications, presents an indoor localization system for estimating relative azimuth and location of location-unaware nodes, referred to as target nodes without applying any algorithms with complex variable and constraints to achieve high accuracy. In the proposed method, the target nodes comprising three mobile nodes estimate the relative distance and azimuth from two reference nodes that can be installed by users. In addition, in the process of estimating the relative localization information acquired from the reference nodes, positioning errors are minimized through a novel modified rounding estimation technique in which Kalman filter is applied without any time consumption algorithms. Experimental results show the feasibility and validity of the proposed system.
CFD Approach on Gas Explosion for SIL in Gas Fuelled Ship
Kim, Ki-Pyoung ; Kim, You-Taek ; Kang, Ho-Keun ;
Journal of the Korean Society of Marine Engineering, volume 39, issue 2, 2015, Pages 195~200
DOI : 10.5916/jkosme.2015.39.2.195
It is envisaged that the effect of increasingly stricter air emissions legislation implemented through IMO Annex VI and other local air quality controls, together with favorable financial conditions for the use of natural gas instead of liquid fuel oil as a bunker fuel, will see an increasing number of DF engine and single gas fuel engine applications to LNG carriers and other vessel types. As part of provision for the current international movements in the shipping industry to reduce GHG emission in air, new design concepts using natural gas as an alternative fuel source for propulsion of large commercial vessels, have been developed by shipyards and research institutes. In this study, an explosion analysis for a gas supply machinery room of LNG-fuelled container ship is presented. The gas fuel concept is employed for the high pressure ME-GI where a leakage in the natural gas double supply pipe to the engines is the subject of the present analysis. The consequences of a leak are simulated with computational fluid dynamics (CFD) tools to predict typical leak scenarios, gas cloud sizes and possible explosion pressures. In addition, capacity of the structure which is subject to explosion loads has been assessed.