• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1017-1026
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• 2009

The solar cell system operates by facing the sun-light. Minor cracks, static discharge, and thermal shock that can happen during production/testing phase can lead to degradation in performance during operation, since solar cells are exposed to extreme thermal/mechanical environment in space. In order to detect small cracks and internal damages in the solar cells due to thermal shocks, which are the core units of a solar cell system, expensive equipment, complicated test process, and much time are required. Therefore, a qualitative method for easily and quickly testing the 'health' of solar cell functionality is required. This dissertation describes a theoretical and technical grounds for quickly and easily evaluating the health of solar cells using electroluminescence effect of Gallium-Arsenide solar cells that are most widely used by spacecrafts in recent years. Also described in the dissertation is the technical issues and constraining factors for applying the proposed method to actual space-rated solar cell systems.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.295-304
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• 2006

Java has been established as one of the most widely-used languages owing to its support of object-oriented concepts, safety, and flexibility. Garbage collection in the Java virtual machine is a core component that relieves application programmers of difficulties related to memory management. In this paper, we propose a memory manager and a garbage collector that is implemented on a embedded java virtual machine. The memory manager divide a heap into various-sized cells and manages it as blocks of same-sized cells. So it is possible to allocate and free memory fast. We adopted the 3-color based Mark & Sweep garbage collector as our base algorithm and we propose 4-color based Mark & Sweep garbage collector for supporting multi-threaded program. The proposed garbage collector occurs memory fragmentation but we show through a experiment that the fragmentation ratio is almost fixed according as we create objects continuously.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.1
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• pp.89-98
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• 2002

Optical current sensor and optical voltage sensor modules were designed and fabricated to improve measurement error and insulation in automatic power distributor By using Faraday effect, optical current sensor with an $\alpha$-iron core was designed and fabricated to minimize current induction of the other phase and was optimized to maintain linearity. Optical voltage sensor was fabricated owing to the pockets effect and adopted spatial electric field type because of small room in an automatic power distributor. To connect a distributor with an external terminal for signal processing, optical multi connector was designed, fabricated and tested for coupling loss and gas leakage. The linearity of optical current sensor for applied current maintains variation of smaller than 2.5% for applied current range from 20A to 700A. The linearity of optical voltage sensor was smaller than 1% for appling voltage from 6.6kV to 19.8kV. Since the measured characteristics are good, these devices can be considered as being applicable in practice.

• Journal of the Korean Institute of Navigation
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• v.14 no.4
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• pp.53-70
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• 1990

Much efforts have been made to improve the training education system for last decades. however, it still leaves much room form improving the system. The reason for this is that the have been many changes in given educational conditions, national and international, and that there existed the lack of training facilities on shore and the limits of capacity on the training ship. The existing program adopts a straight-through system of which the course has to be completed at same time, and also forces students to study the course, disregarding their aptitude for sea life. Consequently, the program resulted in frustrating the learning desire of some students and, as a consequence, in deteriorating the quality of the entire training education. This paper aims to develop an efficient training program including curriculla by the literature survey and the teaching and sea experiences on the training ship "HANBADA" and merchant ships, where the authors have been for many years. Compared with the existing one, the new training model suggested in this paper has some advantages as follows : First, the new model adopts multi-state system which consists of various short-term training courses according to each purpose. This system will be helpful for student to find their aptitude for sea life earlier and to understand classes of major subjection shore. Second, the model includes new curriculla which consist of core subjects (for example, navigation, marine operation, marine transportation, watch keeping and nautical English for deck cadets and internal and external combustion engine, auxiliary machinery, electric and electronics and engine maintenance for engine cadets), by incorporating existing 20 subjects in 5 subjects. These curriculla may contribute to embodying the characteristics of training education where the above mentioned subjects must be linked with each other. In order to implement this new training model efficiently and effectively, the following prerequisties must be prepared : $\circled1$ The contents of each subject included in the new model should be systematically developed. $\circled2$ The educational schedule should be adjusted according to the new model.new model.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.12
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• pp.439-446
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• 2016

In this paper, an efficient prediction accuracy enhancement strategy is proposed for improving the performance of the prediction-based parallel event-driven gate-level timing simulation. The proposed new strategy adopts the static double prediction and the dynamic prediction for input and output values of local simulations. The double prediction utilizes another static prediction data for the secondary prediction once the first prediction fails, and the dynamic prediction tries to use the on-going simulation result accumulated dynamically during the actual parallel simulation execution as prediction data. Therefore, the communication overhead and synchronization overhead, which are the main bottleneck of parallel simulation, are maximally reduced. Throughout the proposed two prediction enhancement techniques, we have observed about 5x simulation performance improvement over the commercial parallel multi-core simulation for six test designs.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.84-89
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• 2013

The demand of LNG tank and the constituting material, i.e., the Al5083 thick plate, increased due to the rapid growth LNG market. To weld the Al5083 thick plate, the gas metal arc welding (GMAW) of high current is necessary to increase manufacturing productivity incurred by the multi pass welding. However, the arc welding vaporizes the volatile element such as magnesium (Mg). This phenomenon changes the Mg composition of the weld metal and the mechanical properties. The study investigated the weldability of Al5083 alloys after conducting high current GMAW. The Al5083 alloy was welded by using different size of welding wires and high current (800-950A). As the arc current increased from 800A to 950A, the mechanical strength decreased and the secondary dendrite arm spacing (SDAS) increased. Even though the arc current increased SDAS, the mechanical strength decreased due to the Mg loss in the weldment. The large diameter of welding wire decreased the dilution of the weld, therefore increasing the Mg content and the strength of the weld. For the reason, the content of Mg in welds was a major parameter to determine the mechanical property for the high current GMAW. For the arc current between 800A and 950A, the yield strength of the weldments showed a relationship with the weight percent of Mg content ($X_{Mg}$): Y.S = 27.9($X_{Mg}$)-11.

• Journal of Fashion Business
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• v.4 no.1
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• pp.73-85
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• 2000

The purpose of this study is for considering about Zen fashion in the point of view of culture transition. Through this research, the Far-East including Korea will be confirmed as a center of fashion culture in 21st century. The contents are the meaning of culture transition in Post Modern period, the meaning of Zen and changing of fashion trend as the background of Zen Fashion, and the characteristics of Zen fashion design. The results are as follows: Anti-western movement or dismantlement of culture has been represented the limitation of western centered culture. So the interesting about East means the changing to east from west in ideas. To make new creation in fashion field, the comprehension about the western fashion which has been preceeded and new trials using the our tradition will be needed. Zen is a kind of Buddhism and the essence of it is to find myself and express individual experiences. The change of one's sens of value, new age movement and concerning of environment and ecology make more comfortable, simple and healthy elements in clothing. The fusion style is under a vogue in life style and Zen is the core of this trend. The characteristics of Zen fashion are flat dismantlement which has been know as a Japanese style, oriental minimalism and nature beauty of ecology. This characteristics are found not only the shape, color but the will of the behind. The pursing temperance and naturalism are represented the fashion culture transition from the West to Far-East. Therefore multi points of fashion research is very important and the identify about Korean fashion is required in lately for new fashion paradigm.

• Journal of KIISE
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• v.42 no.7
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• pp.840-845
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• 2015

In recent years, Big Data has been a topic of great interest for the production and operation work of offshore plants as well as for enterprise resource planning. The ability to predict future equipment performance based on historical results can be useful to shuttling assets to more productive areas. Specifically, a centrifugal compressor is one of the major piece of equipment in offshore plants. This machinery is very dangerous because it can explode due to failure, so it is necessary to monitor its performance in real time. In this paper, we present stream data processing architecture that can be used to compute the performance of the centrifugal compressor. Our system consists of two major components: a virtual tag stream generator and a real-time data stream manager. In order to provide scalability for our system, we exploit a parallel programming approach to use multi-core CPUs to process the massive amount of stream data. In addition, we provide experimental evidence that demonstrates improvements in the stream data processing for the centrifugal compressor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.544-549
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• 2017

This paper aims to examine the effect of rotational fluid motion about the efficiency of the gas - liquid ejector, which is a core unit in a ship equilibrium water treatment system. The ejector is a device for injecting ozone into ship equilibrium by the negative pressure generated by exchange of momentum between water and ozone. The existing ejector ejects the driving fluid with a simple form. In this paper, however, a rotation induction device is applied to the driving nozzle so that the driving fluid can be rotated and injected. To investigate the flow characteristics by the rotational movement of the driving fluid, CFD was used. The pressure and flow rate of the driving fluid, the negative pressure and suction flow rate of the suction fluid in the suction part, and the discharge pressure were predicted. On the basis of the results, the efficiency of the ejector using the rotation induction system was 22.25%, which was about 1.7% better than that of the existing ejector. Finally, to verify the feasibility of the CFD, an experiment was conducted on the ejector using the rotation induction device and the results were similar to those of the CFD.

• Computers and Concrete
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• v.25 no.4
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• pp.311-325
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• 2020

In this research work, the hygrothermal and mechanical buckling responses of simply supported FG sandwich plate seated on Winkler-Pasternak elastic foundation are investigated using a novel shear deformation theory. The current model take into consideration the shear deformation effects and ensures the zero shear stresses on the free surfaces of the FG-sandwich plate without requiring the correction factors "Ks". The material properties of the faces sheets of the FG-sandwich plate are assumed varies as power law function "P-FGM" and the core is isotropic (purely ceramic). From the virtual work principle, the stability equations are deduced and resolved via Navier model. The hygrothermal effects are considered varies as a nonlinear, linear and uniform distribution across the thickness of the FG-sandwich plate. To check and confirm the accuracy of the current model, a several comparison has been made with other models found in the literature. The effects the temperature, moisture concentration, parameters of elastic foundation, side-to-thickness ratio, aspect ratio and the inhomogeneity parameter on the critical buckling of FG sandwich plates are also investigated.