• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.1
• /
• pp.53-59
• /
• 2021

The marine transport industry generally applies new technologies later than other transport industries, such as airways and railways. Vessels require efficient operation, and their performance and lifespan depend on the level of maintenance and management. Many studies have shown that corrective maintenance (CM) and time-based maintenance (TBM) have restrictions with respect to enabling efficient maintenance of workload and cost to improve operational efficiency. Predictive maintenance (PdM) is an advanced technology that allows monitoring the condition and performance of a target machine to predict its time of failure and helps maintain the key machinery in optimal working conditions at all times. This study presents the development of a marine predictive maintenance (MPdM; maritime predictive maintenance) method based on applying PdM to the marine environment. The MPdM scheme is designed by considering the special environment of the marine transport industry and the extreme marine conditions. Further, results of the study elaborates upon the concept of MPdM and its necessity to advancing marine transportation in the future.

• Journal of Advanced Navigation Technology
• /
• v.27 no.4
• /
• pp.382-390
• /
• 2023

The Korea market for LUAV (Light Unmanned Aerial Vehicle) weighing less than 150 kg is growing rapidly. As a result, the market for manufacturing and operating LUAV is expanding, and domestic development of parts and finished products is actively taking place. However, the flight control system and onboard software, which are key components of domestic LUAV, are largely dependent on overseas products due to the excessive cost and period required for development. This paper presented a domestic software development and certification procedure using DO-178C, a guideline for aircraft software development, and the Model-based Development method, and conducted a survey of those involved in the development, manufacturing, and certification of LUAV and analyzed the results. In addition, a case study was conducted to apply the software development plan to the helicopter FCC (Flight Control Computer).

• Journal of Korea Water Resources Association
• /
• v.44 no.7
• /
• pp.565-576
• /
• 2011

Within a basin, there are potentially multiple locations that can be used as a washland, given their relatively small size when compared with other hydraulic facilities such a dam. However, it is unreasonable to install washlands in all these potential locations due to economic and environmental considerations. In this study, a new methodology for determination of installation priority of washlands is presented. How to integrate the decision variables in this decision making problem has been a key issue in previous studies because a washland can provide many benefits such as flood reduction, agricultural benefit and recreational benefit. In particular, a methodology is needed to integrate all decision variables realistically, properly and reasonably, in situations where there is not sufficient data for direct integration of all these decision variables such as construction cost or benefits a washland can provide. This new methodology aims to suggest how to integrate methodologies used in previous studies. The suggested methodology uses four different rankings which are determined based on a flood reduction effect, a relative significance index, an economic analysis, and a space planning suitability index. These rankings are integrated to determine a final installation priority ranking of washlands by a multi-dimensional scaling method. The new methodology has been applied to the Anseong river basin, to show its applicability, and the application result compared with those of previous studies.

• Journal of Korea Game Society
• /
• v.7 no.3
• /
• pp.67-76
• /
• 2007

As the performance of game consoles is so highly progressed that services such as internet browsing become available on the consoles, the need for text input schemes on game consoles is rapidly raised. In this paper, we present a text input method of alphabet characters and several symbols using a gamepad, which is a widely used input device for most game consoles. Just like other text input methods using gamepad, our method allows users to enter texts by manipulating the gamepad with a user interface displayed on the screen of the console. A key idea of this paper is to present the user interface that is similar to the $4{\times}3$ keypad on mobile phones. The motivation of this idea is a principle that the experience of using a text input tool can be transferred to another tool that has similar interface. Another motivation is that the keyboard-based interface is too complex to be easily manipulated by simple input from a keypad, which is four orthogonal directions and several fire signals. Since most of keys on keypad of $4{\times}3$ keys are represented by a combination of two orthogonal directions, users feel easier in entering texts using keypad-based interface. We prove this argument in this paper by a user test of ten subjects. After about two experiment sessions, subjects reach 13 WPM in average, which proves that the proposed text input method enables much faster text input than the existing keyboard-based text input methods.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.4
• /
• pp.495-508
• /
• 2019

Tidal datums are key and basic information used in fields of navigation, coastal structures' design, maritime boundary delimitation and inundation warning. In Korea, the Approximate Lowest Low Water (ALLW) and the Approximate Highest High Water (AHHW) have been used as levels of tidal datums for depth, coastline and vertical clearances in hydrography and coastal engineering fields. However, recently the major maritime countries including USA, Australia and UK have adopted the Lowest Astronomical Tide (LAT) and the Highest Astronomical Tide (HAT) as the tidal datums. In this study, 1-hr interval 19-year sea level records (1999-2017) observed at 9 tidal observation stations along the west and south coasts of Korea were used to calculate LAT and HAT for each station using 1-minute interval 19-year tidal prediction data yielded through three tidal harmonic methods: 19 year vector average of tidal harmonic constants (Vector Average Method, VA), tidal harmonic analysis on 19 years of continuous data (19-year Method, 19Y) and tidal harmonic analysis on one year of data (1-year Method, 1Y). The calculated LAT and HAT values were quantitatively compared with the ALLW and AHHW values, respectively. The main causes of the difference between them were explored. In this study, we used the UTide, which is capable of conducting 19-year record tidal harmonic analysis and 19 year tidal prediction. Application of the three harmonic methods showed that there were relatively small differences (mostly less than ±1 cm) of the values of LAT and HAT calculated from the VA and 19Y methods, revealing that each method can be mutually and effectively used. In contrast, the standard deviations between LATs and HATs calculated from the 1Y and 19Y methods were 3~7 cm. The LAT (HAT) differences between the 1Y and 19Y methods range from -16.4 to 10.7 cm (-8.2 to 14.3 cm), which are relatively large compared to the LAT and HAT differences between the VA and 19Y methods. The LAT (HAT) values are, on average, 33.6 (46.2) cm lower (higher) than those of ALLW (AHHW) along the west and south coast of Korea. It was found that the S_a and N₂ tides significantly contribute to these differences. In the shallow water constituents dominated area, the M₄ and MS₄ tides also remarkably contribute to them. Differences between the LAT and the ALLW are larger than those between the HAT and the AHHW. The asymmetry occurs because the LAT and HAT are calculated from the amplitudes and phase-lags of 67 harmonic constituents whereas the ALLW and AHHW are based only on the amplitudes of the 4 major harmonic constituents.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.6
• /
• pp.35-40
• /
• 2020

The ballast layers play a key role in distributing and supporting a trainload. On the other hand, it settles down by dynamic train loading due to large void ratios. Consequently, it requires continuous maintenance. In this paper, ballast layers mixed with three types of specially shaped artificial ballast (AB) (Rectangular, Tetrapod, Hexagonal) were modeled by using a two dimensional DEM (Discrete Element Method). Repeated loading tests were performed to evaluate the settlement behavior of the ballast layers. The smallest settlement was observed in the case of the ballast layer mixed with Tetrapod AB than in other cases, according to an analysis of the force transfer routes. In addition, contact force analysis showed that the Tetrapod AB, which has a concave shape, could easily make small and multi-channel force-transfer routes. This means that the stress in the ballast layer by the train loading transferred through the sleeper uniformly was distributed well by the AB. Therefore, the settlement of the ballast layer mixed with the concave-shaped Tetrapod AB could be reduced effectively under a repeated train loading. The effects of a decrease in settlement of the ballast layer highlight the possibility of a maintenance-free ballasted track.

• Journal of Digital Convergence
• /
• v.18 no.6
• /
• pp.531-540
• /
• 2020

The purpose of this study was to present ways and tasks for the successful settlement of community care that the korea government recently aimed to convert the care system of the vulnerable from the center of institutional care to the community-based care system. As a research method, we tried to find out the community care policies for foreign developmental disabilities and explore major issues and problems in the process. As a result of the study, de-institutionalization and maintenance and enactment of laws related to community-based care systems, the division of subjects and tasks in policy implementation, and above all, it is necessary to specify necessary financial estimation, procurement plan, and budget securing method. In addition, sincere deliberation on the form of living space for people with developmental disabilities after de-institution and clarification of the subjectivity of using the services provided Establish reliable statistics on the characteristics and degree of disability of people with developmental disabilities, worry about human rights violation factors that can occur in community residential facilities that will be provided after de-facility, and create consensus in the community was also analyzed as an important factor. I think it is a key factor to secure the success of the community care policy by carrying out the above multiple tasks simultaneously.

• Communications of Mathematical Education
• /
• v.28 no.1
• /
• pp.45-55
• /
• 2014

Lacan gives an explanation on our real actual world by the concepts the "Real", the "Imaginary" and the "Symbolic". Although this three registers are not far from each other, they never can be unified. Among animals, only human has interest in the "truth". The concept of truth is discussed and debated in several contexts, including philosophy and religion. Many human activities depend upon the concept, which is assumed rather than a subject of discussion, including science, law, and everyday life. Language and words are a means by which humans convey information to one another, and the method used to determine what is a "truth" is termed a criterion of truth. Accepting then that "language is the basic social institution in the sense that all others presuppose language", Lacan found in Ferdinand de Saussure's linguistic division of the verbal sign between signifier and signified a new key to the Freudian understanding that "his therapeutic method was 'a talking cure'". The purpose of this paper is to understand Lacan's psychology and psychoanalysis by using the mathematical concepts and mathematical models, especially geometrical and topological models. And re-explanation of the symbolic model and symbols can help students understand new ideas and concepts in the educational scene.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.18 no.3
• /
• pp.179-188
• /
• 2015

This study reviewed the type of the project and developmental plan related to ocean energy development in the coastal land boundaries and the ocean, and suggested the efficient scoping method through the diagnosis of the key items of environmental impact assessment (EIA) in the coastal area. The major projects are the construction of tidal power plant, tidal current power plant, and offshore wind power plant in the public water, and also those are the construction of solar power plants in the coastal land boundaries. While the project plans on a large scale such as the construction of tidal power plant, it is important to consider both property of usefulness of the designated areas and harmony analysis with marine space availability based on the adequacy of the site selection and relevance of plan with the master plan for reclamation and strategic environmental assessment (SEA). And also it needs to be considered the careful checkup on the EIA checklist referring to the type of project, effective post-monitoring, and suggestion of mitigating methods to minimize the environmental impacts during the stage of actual environmental impact assessment. Introduction of a system of integrated marine environmental impact assessment should be considered for reasonable and effective manage to developmental projects on the marine spatial area.

• The Journal of Engineering Geology
• /
• v.22 no.3
• /
• pp.275-281
• /
• 2012

Thermal distribution in soils must be considered in engineering designs and constructions, including estimates of frost heave and thaw settlement, infrastructure in cold regions, and geothermal systems. Because thermal conductivity is a key parameter for evaluation of thermal distribution in soils, it must be accurately estimated. The thermal conductivity of fine-grained soils has been widely studied in recent years; however, few studies have reported a reliable method for experimental measurement. The present study presents the results of an experimental investigation of the thermal conductivity of a saturated kaolinite-silica mixture with respect to the variation of dry density. Thermal conductivities were measured in Constant Rate of Strain (CRS) consolidation tests, and the experimental data were analyzed to evaluate the accuracy of the new measurement system. In addition, we present an evaluation method for predicting thermal conductivity in fine-grained soils.