• Journal of Multimedia Information System
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• v.4 no.4
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• pp.195-204
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• 2017

Mobile robots are used for years as a valuable research and educational tool in form of available open-platform designs and Do-It-Yourself kits. Rapid development and costs reduction of Unmanned Air Vehicles (UAV) and ground based mobile robots in recent years allowed researchers to utilize them as an affordable research platform. Despite of recent developments in the area of ground and airborne robotics, only few examples of Unmanned Surface Vehicle (USV) platforms targeted for research purposes can be found. Aim of this paper is to present the development of open-design USV drone with integrated multi-level control hardware architecture. Proposed catamaran - type water surface drone enables direct control over wireless radio link, separate development of algorithms for optimal propulsion control, navigation and communication with the ground-based control station. Whole design is highly modular, where each component can be replaced or modified according to desired task, payload or environmental conditions. Developed USV is planned to be utilized as a part of the system for detection and identification of marine and lake waste. Cameras mounted to the USV would record sea or lake surfaces, and recorded video sequences and images would be processed by state-of-the-art computer vision and machine learning algorithms in order to identify and classify marine and lake waste.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.911-916
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• 2012

The purpose of this study is to review and suggest coastal shipping policies for introduction of WIG craft into domenstic passenger shipping market. Two Korean companies are leading in the development of WIG craft as an innovative sea transportation vehicle, and it is awaiting for commercialization. WIG craft is expected to be commercialized from coastal passenger market and we used AHP method to investigate the major factors and its' priority for smooth market entry. The results shows that priorities are on the WIG craft legislation, dock installation and operation, port state control, and pilot hiring and training, craft maintenance, and ship's certification in order.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.597-599
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• 2010

In this paper, by considering the real UWA channel environments, the measured channel data is used to generate the UWA channel model and calculate the relative parameters for underwater OFDM systems. Practical least square (LS) based channel estimation with linear interpolation are adopted to obtain the channel state information (CSI) at receiver side. As multi-input multi-output (MIMO) processing techniques, Alamouti code is implemented and evaluated to perform for space time block coding (STBC) and space frequency block coding (SFBC) for UWA OFDM systems with the MIMO configuration of $2{\times}1$, at the same time, $1{\times}2$ maximum ratio combining (MRC) is performed for the purpose of comparison. The simulation results show that, with perfect channel estimation, SFBC failed to work duo to the serious frequency selectivity of UWA channel environments. When the practical channel estimation is applied, in the case of STBC, the proposed 4-column pilot pattern gives better performance about 7dB than SISO system.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.504-508
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• 2003

New banana-shaped achiral compounds, 4-chloro-1,3-phenylene bis [4-4(3-fluoro-9-alkenyloxy) phenyl-iminomethylbenzoate]s and 4-chloro-1,3-phenylene bis [4-4-(3-fluoro-10-alkanyloxy) phenyliminomethyl benzoate]s were synthesized by varying the substituent (X=H, F, or Cl); their electrooptical properties are described. The smectic phases, including a switchable chiral smectic C ($SmC^{\ast}$) phase, were characterized by differential scanning calorimetry, polarizing optical microscopy, and triangular method. The presence of vinyl end group at the terminals of linear side wings in the banana-shaped molecules induced a decrease in melting temperature. The smectic phase having the undecenyloxy group such $as-(CH_2)_9CH=CH_2$ showed ferroelectric switching, and its value of spontaneous polarization on reversal of an applied electric field was 2250 $nC/cm^2$, while the value of spontaneous polarization of the smectic phase having the decanyloxy group such as $-(CH2)_9CH_3$ was 3700 $nC/cm^2$. We could obtain the ferroelectric phase with low isotropic temperature by varying the end group at the terminals of linear side wings in the banana-shaped achiral molecules.

• Korean Journal of Construction Engineering and Management
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• v.13 no.2
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• pp.3-10
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• 2012

The current enforcement regulation of "Construction Technology Management Act" prescribes calculation standard of environmental preservation cost in construction site. According to this standard, environmental preservation cost is calculated by using the quantity-per-unit costing method or applied fixed rate on direct cost. However, when calculated by using the quantity-per-unit costing method it is few items to put in the budget according to standard of construction estimate and in the case of using the fixed rate on direct cost it is not considering various characteristics of the construction site. Therefore, it is needed a improvement plan of estimating method and management system for environmental preservation cost. In this study, it surveyed the actual state of the environmental preservation cost according to magnitude of project, site location, anti-pollution facilities and etc. over 38 road projects. The research reported in this paper environmental preservation cost was variously distributed over construction sites. Thus it needs to estimating method and management system to consider characteristics of construction site for environmental preservation cost.

• Atmosphere
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• v.23 no.4
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• pp.453-470
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• 2013

As a part of the KIAPS Observation Processing System (KOPS), we have developed the modules of satellite radiance data pre-processing and quality control, which include observation operators to interpolate model state variables into radiances in observation space. AMSU-A (Advanced Microwave Sounding Unit-A) level-1d radiance data have been extracted using the BUFR (Binary Universal Form for the Representation of meteorological data) decoder and a first guess has been calculated with RTTOV (Radiative Transfer for TIROS Operational Vertical Sounder) version 10.2. For initial quality checks, the pixels contaminated by large amounts of cloud liquid water, heavy precipitation, and sea ice have been removed. Channels for assimilation, rejection, or monitoring have been respectively selected for different surface types since the errors from the skin temperature are caused by inaccurate surface emissivity. Correcting the bias caused by errors in the instruments and radiative transfer model is crucial in radiance data pre-processing. We have developed bias correction modules in two steps based on 30-day innovation statistics (observed radiance minus background; O-B). The scan bias correction has been calculated individually for each channel, satellite, and scan position. Then a multiple linear regression of the scan-bias-corrected innovations with several predictors has been employed to correct the airmass bias.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.423-429
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• 2016

A study was conducted to analyze the oil spill dynamic state using system dynamics method, and to developed regional risk program based on oil spill history for better judgement of the situation at the early stage of oil spill. Results were obtained as follows: Firstly, various variables were calculated by a score based on raw data of oil spill history in Korea. Regional oil spill risk was also calculated in a quantitative way. Secondly, calculated regional oil spill risk was analyzed and programmed with a help of smart-device for better use. Thirdly, comparison of oil spill risk between regions became possible and regional oil spill risk program proved to be useful in prompt decision under urgent situation in response to oil spill at sea. Convenient and quick oil spill risk without special restrictions have been able to determine. and it can help in anticipative preparation (strategy) for oil spills.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.23-28
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• 2007

This study estimated the behavior(movement) characteristics of floating marine debris flowing in the Nakdong River Estuary using a simple numerical particle-tracking model. This numerical experiment considered the maximum water discharge outflow from the Nakdong River barrage during the passage of typhoon Maemi in 2003. The simulation showed that the particle distribution and movement of floating marine debris in the Nakdong River Estuary reached a stable state at 72 hours after the typhoon had passed, during the flαxl period of river discharge. The quantity of floating particles distributed on the east coast of Gadeok and Jinu Islands increased by 40% at 33 hours after starting the model, while the change in other sea areas was $20{\sim}40%$.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.6
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• pp.471-477
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• 2015

When a ship sails in a seaway, the resistance on a ship increases due to incident waves and winds. The magnitude of added resistance amounts to about 15–30% of a calm-water resistance. An accurate prediction of added resistance in waves, therefore, is essential to evaluate the performance of a ship in a real sea state and to design an optimum hull form from the viewpoint of the International Maritime Organization (IMO) regulations such as Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI). The present study considers added resistance problem of AFRAMAX-class tankers with the conventional bow and Ax-bow shapes. Added resistance due to waves is successfully calculated using 1) a three-dimensional time-domain seakeeping computations based on a Rankine panel method (three-dimensional panel) and 2) a commercial CFD program (STAR-CCM+). In the hydrodynamic computations of a three-dimensional panel method, geometric nonlinearity is accounted for in Froude-Krylov and restoring forces using simple wave corrections over exact wet hull surface of the tankers. Furthermore, a CFD program is applied by performing fully nonlinear computation without using an analytical formula for added resistance or empirical values for the viscous effect. Numerical computations are validated through four degree-of-freedom model-scale seakeeping experiments in regular head waves at the deep towing tank of Hyundai Heavy Industries.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.1
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• pp.67-75
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• 2010

Submarine and deep sea diving structures are generally designed based on their ultimate strength. Fatigue strength at welded joint must be also taken into account because working stress is increased due to the increasing of diving depth and using high yield steel. The pressure hulls of submarine are subjected to fluctuating compressive loading. But in addition to the calculated stresses, high residual tensile stresses at welded part have to be considered. The state of stress level of pressure hull is tensile at surface and compressive at deep diving depth. This paper presents the results of an experimental investigation on the crack initiation and growth at the weld toe of T welded joints of HY-100 steel plate under constant amplitude loading. It is also investigated the phenomenon of the fatigue failure and test methods. Fatigue tests have been using real scaled local structural models of full penetration T-welded joint, which is a part of the cylindrical shell structures reinforced by ring stiffeners. Several load ratios under constant amplitude loading are considered in the tests. Crack initiation and growth characteristics are examined based on the beach marks of the cracked section of the test specimens. A design stress-life curve including the design formula is suggested according to tested data.