• Magazine of the Korea Concrete Institute
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• v.9 no.3
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• pp.157-166
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• 1997

The object of this study was invest, igat, ing the failure phenomenon in the contact zone of rcpnired concrete structures due to the external climate change(hygral transient condition). This study was carrie out by calculating the non-stationary moisture and stress distribution in the repaired concrete structures with the cement mortar. In this analysis, main variables were the overlay thickness (Do=0.5-2.5cm). and the pre-wetting time(tc= l-5days). and the cxtcrnal 1.~1ative humidity(Ho=50-80%). The results show that the minimum overlay thickness and the minimum pre-wetting time are necessary to k e ~ p compressive stresses in the contact zone for a relative humidity.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.5
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• pp.489-495
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• 2008

This paper offers a practical control scheme for driving mode transformation of a rescue robot already developed. The rescue robot, VSTR(Variable Single-Tracked Robot), has two driving modes, so can traverse untidy terrain and overcome obstacles such as stairs easily by use of timely driving mode transformation. Classical PI control scheme was used firstly for driving mode transformation, but stationary phenomenon, which might have a bad effect on the performance in real situation, came into existence. Therefore, we suggest a new controller, PI-based feedforward controller, which should be a good alternative for the problem, and compare it with other nonlinear control scheme.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.330-336
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• 2004

Fifty-two pathogenic Vibrio parahaemolyticus strains were isolated from the environments of Busan and Yeosu, Korea. Forty-three of these strains showed protease activities, whereas 4 strains showed $\alpha / \beta$ hemolysin activities and 6 strains had urease activities. Their pathogenic factors were not overlapping except one strain, which had both protease and hemolysin activities. The 6 urease-positive strains (V. parahaemolyticus YKB4, YKB14, S25, YFB20, YFO21, and YFO22) showed the same biochemical characteristics as a reference strain [V. parahaemolyticus KCTC 2471 (urease-negative)], except for urease production. The 6 urease-positive strains showed different urease activities in their culture supernatant during the growth. The urease activity of S25 increased sharply at the late exponential phase, and was the highest at the initial stationary phase and was kept until the late stationary phase. The other 5 isolates, except C25, showed urease activities at the mid-stationary phase and increased steadily until the late stationary phase, when the urease activity was maximal. To compare the degree of virulence of V. parahaemolyticus with different pathogenic factors, hemolysin, protease, or urease-positive strains were injected into groups of 10 each of ICR mice (7- to l0-week-old males). The lethal rates of urease-positive V. parahaemolyticus, YKB14, YKB4, and S25, were significantly high, being 50, 70, and 80%, respectively. Protease-positive V. parahaemolyticus strains FM39 and FM50 showed 40% and 60% of lethal rate, respectively. Hemolysin-positive V. parahaemolyticus strains S34 and S72 had no mortality, similar to nonpathogenic V. parahaemolyticus FM12.

• Proceedings of the Korea Water Resources Association Conference
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• 1998.05b
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• pp.3-3
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• 1998

In this pressentation it is argued that the heterogeneity of a hydrologic attribute which may seem to be nonstationary at one scale, may become stationary at a larger scale. The fundamental reason for transformation from nonstationarity to stationarity whith the increase in scale is the phenomenon of coarse-graining of the hydrologic processes with increasing scale. Due to the phenomenon of aliasing, a particular scale hydrologic process heterogeneity which is observed as a nonstationary process at that scale, may be observed as a stationary process at a higher(larger) scale whose size is bigger than the stationary extent of the lower scale heterogeneity. As one goes through a hierarchical sequence of larger and larger scales for observations, one would eliminate nonstationarities which emerge at some lower scales at the expense of losing information on the high frequency fluctuations of the lower scale heterogeneities which will no longer be observed at the larger sampling scales. We call this phenimenon as the "coarse-graining in hydrologic observations". In this presentation, it is also argued that by the coarse-graining of hydrologic processes due to the averaging and aliasing operations at increasing scales, the conservation laws corresponging to these scales may still be quite parsimonious, and need not be more complicated as the scales get larger. It is shown that shen a higher(larger) scale process is formed by averaging a lower(smaller) scale process in time or space, the high frequency components of the lower scale process will be eliminated by the averaging operation. Thereby, the resuliiting average hydrologic dynamics, free from the effects of the high frequency components of the lower scale process, can still be quite simple in form. This is demonstrated by means of some recent upscaling work on the solute teansport conservation equation for hetergeneous aquifers. By means of this solute transport example, it is also shown that for the ensemble average form of a hydrologic conservation equation to be equivalent to its volume-average form at any scale, the parameter functions of that conservation equation at the immediately lower scale must be ergodic.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.11
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• pp.31-43
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• 1996

In this paper, we propsoe an encryption algorithm of image information using a mass transfer function (MTF). The algorithm is based on a diffusion phenomenon of black ink when black ink dropped in the stationary water. We mathematically analyze the phenomenon, in consideration of characteristics of image information, and apply the results of analysis to the security of image transfer phenomenon. The cryptosystem proposed in this paper enables the security services of information in narrow-band channel communication network to be provided. And in transmission of important information, it can secure against intentional disturbance and violation. Also, it can guarantee the safe flow of information.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.121-129
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• 1996

본 연구에서는 대기 습도변화에 의한 콘크리트 보수체(기층 콘크리트/보수 모르터)의 파괴현상을 조사하기 휘해서 보수체내의 비정상적인 습도분포를 계산하였다. 계산된 습도분포에 의해서 기층과 보수층 경계면 부위의 습도차이가 보수층 두께(0.5~2.5cm)와 보수작업전 기층 콘크리트 표면의 습윤처리시간(0~72hr)을 주요 변수로 하여 조사되었고, 이는 주로 시멘트 모르터로 보수된 접촉면이 없는 보수체에서 수행되었다. 계산 및 조사결과 보수층 두께가 감소하고 습윤 처리시간이 증가할수록 경계면 부위의 습도차이는 감소하는 경향을 보였고, 특히 보수후 습도차이가 음수값이 될 때의 시간을 하나의 수식으로 표시하였다.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.284-287
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• 2008

Flow over a sphere under forced oscillation at Re=300 is simulated for various frequency ratios which are defined as excitation frequency over natural frequency of stationary sphere. The results of oscillating sphere are compared with those of stationary sphere and an oscillating cylinder. Detailed vortical structures, hydrodynamic forces and frequencies of the wake are prescribed as a function of frequency ratio. For oscillating sphere, planar symmetry of the wake is kept and two nearly symmetric hair pin vortices are induced by oscillation for one period of oscillation when the frequency ratio is bigger than 0.5. Modulation phenomenon which can be found in an oscillating cylinder were not seen for an oscillating sphere.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.179-183
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• 1999

Rubbing occurs when a rotating element comes in contact with a stationary element. In the steam turbines, the rotating element is the rotor while the stationary elements are usually the oil deflectors and packing seals. Rubbing phenomenon may be often obseued on a new or rebuilt machine rather than on a machine that has been operating for several months or years. Rubbing in the turbine has been classified into two modes by the operating conditions: 1) start up or shut down, 2) steady state. At start up or shut down operation, rubbing produces synchronous whirl vibration, which are caused by thermal bow of the shaft due to localized heating on the shaft surface. While subsynchronous whirl vibration is caused by partial rubbing during the steady state operation. In this paper, the two case studies of troubleshooting for excessive vibration caused by rubbing in the actual steam turbines are investigated.

• The Korean Journal of Applied Statistics
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• v.25 no.4
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• pp.543-552
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• 2012

Parrondo paradox is a counter-intuitive phenomenon where two losing games can be combined to win or two winning games can be combined to lose. When we trade stocks with a history-dependent Parrondo game rule (where we buy and sell stocks based on recent investment outcomes) we found Parrondo paradox in stock trading. Using stock data of the KRX from 2008 to 2010, we analyzed the Parrondo paradoxical cases in the Korean stock market.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.30.4-31
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• 2008

Formation of longitudinally wave-like plasma density structure in the low-latitude F region is now a well-known phenomenon from the extensive studies in recent years. Observations of plasma density from multiple satellites have shown that the locations of the crests of the plasma density that are seen to be stationary during daytime are shifted after sunset. This phenomenon has been understood to be caused by eastward drift of the ionosphere at night. However, the eastward drift velocity of the ionosphere after sunset is not sufficiently large enough to explain the day-night difference in the longitudinal density structure. The just after sunset and the nighttime ionospheric morphologymay be affected by this drift after sunset. In this study, we will investigate the temporal variation of the phase of the longitudinal density structure and vertical plasma drift by analyzing the ROCSAT-1, TIMED/GUVI, and DMSP data and verify the role of the vertical drift after sunset in the change of the phase of the longitudinal density structure.