• Journal of The Korean Astronomical Society
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• v.47 no.4
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• pp.137-145
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• 2014

The astrophysical parameters of four unstudied open star cluster candidates; Ivanov 2, 7, 9, and Harvard 9; are estimated for the first time using the PPMXL database. The stellar density distributions and color-magnitude diagrams for each cluster are used to determine the geometrical structure (cluster center, limited radius, core and tidal radii, the distances from the Sun, from the Galactic center and from the Galactic plane). Also, the main photometric parameters (age, distance modulus, color excesses, membership, total mass, relaxation time, luminosity and mass functions) are estimated.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.2
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• pp.75-82
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• 2017

With the development of computational fluid dynamics (CFD), studies on shipbuilding and maritime issues including free-surface wave flow have been conducted. Although the volume of fluid (VOF) and level-set methods are widely used to study the free-surface wave flow, disadvantages exist. In particular, it takes a long time to obtain solutions. In this study, a free-surface capturing code is developed for ship and offshore structures. The developed code focuses on accuracy and computation time. Open source CFD libraries, termed OpenFOAM, are used to develop the code. The results obtained using the developed code are compared with those obtained using interFoam. The results show that the developed code could be used to capture the free-surface wave flow without numerical diffusion; moreover, the accuracy of the developed code is largely the same as that of interFoam.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.53.2-53.2
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• 2016

We present our experiences with open-source spatio-temporal database systems for managing and analyzing big astronomical data acquired by wide-field time-domain sky surveys. Considering performance, cost, difficulty, and scalability of the database systems, we conduct comparison studies of open-source spatio-temporal databases such as GeoMesa and PostGIS that are already being used for handling big geographical data. Our experiments include ingesting, indexing, and querying millions or billions of astronomical spatio-temporal data. We choose the public VVV (VISTA Variables in the Via Lactea) catalogs of billions measurements for hundreds of millions objects as the test data. We discuss issues of how these spatio-temporal database systems can be adopted in the astronomy community.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.88.3-89
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• 2017

We present our experiences with open-source NoSQL database systems in analyzing spatial and temporal astronomical data. We conduct experiments of using Redis in-memory NoSQL database system by modifying and exploiting its support of geohash for astronmical spatial data. Our experiment focuses on performance, cost, difficulty, and scalability of the database system. We also test OpenTSDB as a possible NoSQL database system to process astronomical time-series data. Our experiments include ingesting, indexing, and querying millions or billions of astronomical time-series measurements. We choose our KMTNet data and the public VVV (VISTA Variables in the Via Lactea) catalogs as test data. We discuss issues in using these NoSQL database systems in astronomy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.955-958
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• 2003

Strip top mark is one of the major problem areas in hot strip coiling operation. The key for good coiling is having a precise detection instrument of strip head end and an understanding of QOC(quick open control) control algorithm and mechanism. Therefore, this study aims at developing QOC monitoring system that is useful for avoiding strip top mark at coiling process. In this study, strip movement between mandrel and unit roll(wrapper roll) was thoroughly studied using high speed camera. The monitoring system was developed to calculate QOC open time and to estimate optimal open time values for good coiling operation. Its performance has been proven by extensive field tests on downcoiler of #2 Hot Strip Mill Line in Pohang Works.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.457-464
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• 2001

The aeroacoustic phenomena in the simple rectangular open cavity are well published by many researchers. But the geometry shapes of aircraft landing gear wells, weapon bays, etc. are more complicate than that of the simple retangular cavity. They are more similar to the cavity having cover-plates at adges, or Helmholtz resonator. Therefore, the effects of cover-plates existing on edges of rectangular open cavity are numerically investigated in this paper. The compressible Navier-Stokes equations are solved for two-dimensional cavities with laminar boundary layers upstream. The high-order and high-resolution numerical schemes are used for the evaluation of spatial derivatives and the time integration. Physically correct numerical boundary conditions and buffer zone techniques are implemented to produce time-accurate solutions in the whole computation domain. The computational domain is large enough to directly resolve a portion of the radiated acoustic field. Results show that the cover-plates existing on edges of cavity reduce the noise convected from cavity, make the frequency of noise become higher, and change the directivity pattern. So these results can be used in the design of a low noise cavity.

• Knowledge Management Research
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• v.19 no.1
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• pp.119-132
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• 2018

Many advanced products and services are emerging in the market thanks to data-based technologies such as Internet (IoT), Big Data, and AI. The construction of a system for data processing under the IoT network environment is not simple in configuration, and has a lot of restrictions due to a high cost for constructing a high performance server environment. Therefore, in this paper, we will design a development environment for large data analysis computing platform using open source with low cost and practicality. Therefore, this study intends to implement a big data processing system using Raspberry Pi, an ultra-small PC environment, and open source API. This big data processing system includes building a portable server system, building a web server for web mining, developing Python IDE classes for crawling, and developing R Libraries for NLP and visualization. Through this research, we will develop a web environment that can control real-time data collection and analysis of web media in a mobile environment and present it as a curriculum for non-IT specialists.

• Journal of Chest Surgery
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• v.22 no.6
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• pp.996-1000
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• 1989

Open heart surgery begun at 1959 in Korea. From that time to 1979, the surgery was performed below 100 cases in a year. However,that was performed above, 1,000 cases in a year from 1981. During the recent three years, i.e., 1985, 1986, and 1987, the annual operative cases were 3614,4503, and 4906, and then the mortality rates were progressively decreased to 6.2%, 5.3 %, and 5.0 %. In these time, overall mortality rate above 1 year old was 5.0 % versus that below 1 year old 17.9 9o in congenital heart diseases. These results are statistically different between two groups. Of the valvular heart disease cases, which occupied 97 % of total acquired heart disease, individual incidence was in mitral 68 %, and aortic 28%. The operative method was mainly valve replacement. Operative mortality for valve surgery in total was 4.4 %. Until 1985, bioprosthetic valve was frequently implanted but mechanical valve has been done more frequently in these days. Coronary artery bypass graft was large portion [67 * 75 %] of open heart surgery in western, but was below 1 % in Korea. However our diet patterns have been changed. Therefore we think the incidence of coronary artery disease will be increased. So we will be familiar to this field.

• Journal of Chest Surgery
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• v.13 no.1
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• pp.41-47
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• 1980

Fifty one consecutive patients undergoing open heart surgery, twenty eight congenital and twenty three acquired heart disease, were studied between May and August 1979 in Dept. of Thoracic and Cardiovascular Surgery SNUH. During the same time 10 patients of PDA were included in this study as control group. Four out of fifty one OHS patients, two ASD and two pulmonic stenosis patients, were operated without aortic cross-clamp. In all patients, serial determination of total level of creatine phosphokinase [CPK], lactic dehydrogenase [LDH], glutamic oxaloacetic transaminase [SGOT] were made preoperatively, operative day [immediate post-op], and post-operative days up to 7th day. Electrocardiograms were also evaluated serially. Open heart surgery patients were divided into two groups; Group A was aorta clamp time beyond SO minutes, and Group B was below 50 minutes. The peak level of each enzyme was compared, and electrocardiographic changes were also compared between groups. Although the electrocardiographic changes were more frequent in Group A [50%] than Group B [24%], the peak levels of each enzymes were almost same in Group A and Group B.

• Journal of Communications and Networks
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• v.16 no.4
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• pp.436-446
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• 2014

The high intensity of research and modeling in fields of mathematics, physics, biology and chemistry requires new computing resources. For the big computational complexity of such tasks computing time is large and costly. The most efficient way to increase efficiency is to adopt parallel principles. Purpose of this paper is to present the issue of parallel computing with emphasis on the analysis of parallel systems, the impact of communication delays on their efficiency and on overall execution time. Paper focuses is on finite algorithms for solving systems of linear equations, namely the matrix manipulation (Gauss elimination method, GEM). Algorithms are designed for architectures with shared memory (open multiprocessing, openMP), distributed-memory (message passing interface, MPI) and for their combination (MPI + openMP). The properties of the algorithms were analytically determined and they were experimentally verified. The conclusions are drawn for theory and practice.