• IE interfaces
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• v.24 no.1
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• pp.78-86
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• 2011

To mitigate space restriction and to raise productivity, some shipbuilding companies use floating-docks on the sea instead of dry-docks on the land. In that case, a floating-crane that can lift very heavy objects (up to 3,600 tons) is used to handle the blocks which are the basic units in shipbuilding processes, and so, very large blocks (these are called the mega-blocks) can be used to build a ship. But, because these mega-blocks can be made only in the area near the floating-dock and beside the sea, the space is very important resource for the process. Therefore, our problem is to make an efficient spatial schedule for the mega-block assembly yard. First of all, we formulate this situation into a mathematical model and find optimal solution for a small problem using a commercial optimization software. But, the software could not give optimal solutions for practical sized problems in a reasonable time, and so we propose a GA-based heuristic algorithm. Through a numerical experiment, finally, we show that the spatial scheduling algorithm can provide a very good performance.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.12
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• pp.345-352
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• 2021

Guided by a resource-based theory, this study is the first one that takes a quantitative approach to identify determinants of competitiveness of women-owned small and medium enterprises (SMEs) in Vietnam. The study employs time series data of Vietnamese SMEs extracted from the Vietnam Small and Medium Enterprises Survey conducted biennially from 2005 to 2015 in ten Vietnamese provinces. Firm competitiveness hereby is indicated by revenue, market share, profitability, and export volume. The research reveals a number of determining factors, of all, research and development, labor skills, business environment, technology investment are the most important factors, followed by capital and headcount. It is indicated that the determining factors have different influences on competitiveness obtained by different measurements. Therefore, it is based on specific targets and situations to make wise business decisions. The authors also make comparisons among groups of women-owned enterprises divided by their firm age, location, ownership, export, age, and educational background of business owners. The findings serve as critical empirical evidence and provide policy recommendations for improving the competitiveness of women-owned SMEs in Vietnam. The recommendations range from technology support, education and professional support for female entrepreneurs, access to capital and human resources to business environment improvement.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.590-598
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• 2019

Today, satellites are widely used in many fields like communication and image recoding. The image acquired by satellites contains variety information of wide region. Therefore, they are used for agriculture, resource exploitation and management, and military purpose. The satellite is required to acquire images effectively in a given time period. Because the period that satellites can acquire images is very restrictive. In this study, the modeling of processing time and attitude maneuvering for satellite image acquisition is performed. From this modeling, mission planning algorithm using heuristic evaluation function is suggested and performance of the proposed algorithm is verified by numerical simulation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.47 no.2
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• pp.116-123
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• 2024

In the manufacturing industry, dispatching systems play a crucial role in enhancing production efficiency and optimizing production volume. However, in dynamic production environments, conventional static dispatching methods struggle to adapt to various environmental conditions and constraints, leading to problems such as reduced production volume, delays, and resource wastage. Therefore, there is a need for dynamic dispatching methods that can quickly adapt to changes in the environment. In this study, we aim to develop an agent-based model that considers dynamic situations through interaction between agents. Additionally, we intend to utilize the Q-learning algorithm, which possesses the characteristics of temporal difference (TD) learning, to automatically update and adapt to dynamic situations. This means that Q-learning can effectively consider dynamic environments by sensitively responding to changes in the state space and selecting optimal dispatching rules accordingly. The state space includes information such as inventory and work-in-process levels, order fulfilment status, and machine status, which are used to select the optimal dispatching rules. Furthermore, we aim to minimize total tardiness and the number of setup changes using reinforcement learning. Finally, we will develop a dynamic dispatching system using Q-learning and compare its performance with conventional static dispatching methods.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.6
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• pp.379-386
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• 2008

Calcined clay granules (pellet) have been used as a soil conditioner. The space among the pellets can secure drainage of water in soil and, simultaneously, can keep water for plants in the inner pore of that. However, the usage of the pellet has been restrained because fabrication of that requires a high energy and cost for heating over the temperate of $1000^{\circ}C$. Recently, SCS(Self-propagating Combustion and Sintering) method was developed and this method use the combustion energy of the preliminary mixed combustible. The SCS method is suitable to fabrication of small porous aggregate and requires a very low cost. This research applied the SCS method to coal refuses for fabrication of soil conditioner pellets. The coal refuses were pulverized under the size of $100{\mu}m$ and the pulverized powders were pelletized to the size of 4~6mm. The pellets were heated at the temperature of $1200^{\circ}C$ in the SCS furnace that was specially prepared for this research. Characteristics of the pellets were investigated and were compared with that of ordinary calcined clay pellet of kaolin; porosity, pore size distribution, bulk density, pH and etc.. Characteristics of the moisture retention in the pellets were measured by the centrifugal method: ASTM D425-88. The pellets of the coal refuses showed the higher values of the field capacity and the plant-available water than that of kaolin pellet. These results suggest the very low cost process that can utilize the coal refuses and can fabricate the lightweight porous soil conditioner of the very high plant-available water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.144-152
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• 2018

Lunar exploration, which was led by the United States and the former Soviet Union, ceased in the 1970s. On the other hand, since massive lunar ice deposits and rare resources were found in 1990s, European Union, China, Japan, and India began to participate in lunar exploration to secure future lunar resource as well as to construct a lunar base. In the near future, it is expected that national space agencies and private industries will participate in the lunar exploration together. Their missions will include the exploration and sample return of lunar resources. Lunar resources have a close relationship with the lunar in-situ resource utilization (ISRU). To construct a lunar base, it is inevitable to bring huge amounts of resources from Earth. Water and oxygen, however, will need to be produced from local lunar resources and lunar terrain feature will need to be used to construct the lunar base. Therefore, in this paper, the global trends on lunar exploration and lunar construction technology are investigated and compared along with the ISRU technology to support human exploration and construct a lunar base on the Moon's surface.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.541-550
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• 2015

The importance of efficient enterprise network management has been emphasized continuously because of the rapid utilization of Internet in a limited resource environment. For the efficient network management, the management policy that reflects the characteristics of a specific network extracted from long-term traffic analysis is essential. However, the long-term traffic data could not be handled in the past and there was only simple analysis with the shot-term traffic data. However, as the big data analytics platforms are developed, the long-term traffic data can be analyzed easily. Recently, enterprise network resource efficiency through the long-term traffic analysis is required. In this paper, we propose the methods of collecting, storing and managing the long-term enterprise traffic data. We define several classification categories, and propose a novel network resource efficiency through the multidirectional statistical analysis of classified long-term traffic. The proposed method adopted to the campus network for the evaluation. The analysis results shows that, for the efficient enterprise network management, the QoS policy must be adopted in different rules that is tuned by time, space, and the purpose.

• Membrane Journal
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• v.22 no.1
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• pp.23-34
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• 2012

In this study, we investigated the permeation property of single gases ($N_2$, $O_2$, $SF_6$, $CF_4$ through hollow fiber polymeric membrane (PSF, PC, PI) as a function of pressure and temperature to decide operating condition for $SF_6$ gas separation process. The results showed the gas permeation varied differentlydepending on the properties of gases and membrane. When permeance of each gases was represented as a function of temperature and pressure in 3 dimensional space, the surface of permeance was shown approximately flat. Thus, we established permeance models with forms of first-and second-order polynomial. These two models showed high goodness of fit. This indicates that the two polynomial models have enough applicability to predict the gas separation process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.630-637
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• 2019

The scientific, economical and industrial values of the Moon have been increased, as massive ice-water and rare resource were founded from the lunar exploration missions. Korea and other major space agencies in the world are competitively developing the ISRU (In Situ Resource Utilization) technology to secure future lunar resource as well as to construct the lunar base. To prepare for the lunar construction, it is essential to develop the rover based construction spatial information technology to provide a decision-making aided information during the lunar construction process. Thus, this research presented the construction spatial information technology based upon rover's camera system. Specifically, the conceptual design of rover based camera system was designed for acquisition of a rover's navigation image, and lunar terrain and construction images around the rover. The reference architecture of the rover operation system was designed for computation of the lunar construction spatial information. Also, rover's localization and terrain reconstruction methods were introduced considering the characteristics of lunar surface environments. It is necessary to test and validate the conceptual design of the construction spatial information technology. Thus, in the future study, the developed rover and rover operation system will be applied to the lunar terrestrial analogue site for further improvements.

• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.237-255
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• 2021

Lychnis wilfordii (Regel) Maxim. is one of the wetland specialists mainly distributed in peatlands at high latitudes. In Korea, it is isolated in two regions. This study investigated habitats, growth traits, and self-compatibility of L. wilfordii and assessed the internal dynamics of its population persistence. Its population has remained stable in the Yongneup Wetland Protected Area (YWPA). There was a clear difference in vegetation environment between YWPA and the distribution area in Daegwallyeong (DWL), Pyeongchang-gun. It has self-compatibility while pollinators facilitate its seed production. It produces a large number of hibernacles and bears the maximum number of branches and fruits in soil with rich organic contents. However, it grows and bears fruits even under the condition of low organic contents. In YWPA, L. wilfordii is not distributed in high moor but widely distributed in low moor where tussocks by Carex thunbergii var. appendiculata are developed. It is mainly distributed on the top of tussocks also. Therefore, it is judged that the formation, growth, and extinction of tussocks by C. thunbergii var. appendiculata is closely related to the establishment, growth, and extinction of plants distributed in this space. It is assessed that the current YWPA has well-developed tussocks in which L. wilfordii is widely distributed, and extinction and re-establishment progress well. Accordingly, the L. wilfordii population is expected to be sustainable in the long term given if its current ecological process is maintained well.