• Bulletin of the Korean Chemical Society
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• v.9 no.1
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• pp.36-40
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• 1988

The time correlation functions of concentration fluctuations due to the random forces near the steady state are evaluated for a general two-component nonlinear chemical system by solving the corresponding two dimensional Fokker-Planck equation. The approximate method of solving the Fokker-Planck equation is based on the eigenfunction expansion and the corresponding eigenvalues for both the linear and nonlinear Fokker-Planck operators are obtained near the steady state. The general results are applied to the Lotka model near the oscillatory marginal steady state and the comparison is made between linear and nonlinear cases.

• Atmosphere
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• v.21 no.3
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• pp.257-271
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• 2011

The aim of this study is to examine weather modification by urbanization and human activities. The characteristics of the urban heat island (UHI) and precipitation in Seoul metropolitan area of Korea are investigated to demonstrate that cities can change or modify local and nearby weather and climate, and to confirm that cities can initiate convection, change the behavior of convective precipitation, and enhance downstream precipitation. The data used in this study are surface meteorological station data observed in Seoul and its nearby 5 cities for the period of 1960 to 2009, and 162 Automatic Weather System stations data observed in the Seoul metropolitan area from 1998 to 2009. Air temperature and precipitation amount tend to increase with time, and relative humidity decreases because of urbanization. Similar to previous studies for other cities, the average maximum UHI is weakest in summer and is strong in autumn and winter, and the maximum UHI intensity is more frequently observed in the nighttime than in the daytime, decreases with increasing wind speed, and is enhanced for clear skies. Relatively warm regions extend in the east-west direction and relatively cold regions are located near the northern and southern mountains inside Seoul. The satellite cities in the outskirts of Seoul have been rapidly built up in recent years, thus exhibiting increases in near-surface air temperature. The yearly precipitation amount during the last 50 years is increased with time but rainy days are decreased. The heavy rainfall events of more than $20mm\;hr^{-1}$ increases with time. The substantial changes observed in precipitation in Seoul seem to be linked with the accelerated increase in the urban sprawl in recent decades which in turn has induced an intensification of the UHI effect and enhanced downstream precipitation. We also found that the frequency of intense rain showers has increased in Seoul metropolitan area.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.325-331
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• 2015

Purpose: This study was to find the correlation between exophthalmetry and visual functions. Methods: Exophthalmetry and visual functions of 200 adults without ophthalmophathy and general disease were examined. Exophthalmetry were measured with Hertel's exophthalmometer. Visual functions (myopia, distance exophoria, near exophoria, near point of convergence, near point of accommodation) were measured for three times. Results: The exophthalmetry was $13.59{\pm}1.10mm$. Myopia, distance exophoria, near exophoria, near point convergence, and near point accommodation were measured as $-2.48{\pm}1.91D$, $3.51{\pm}1.78{\Delta}$, $5.73{\pm}2.44{\Delta}$, $9.63{\pm}2.82cm$, and $21.73{\pm}10.28cm$. With increasing exophthalmetry, the unaided visual acuity, myopia and astigmatism were decreased. On the other hand, distance exophoria, distance esophoria, near exophoria, near point of convergence and near point of accommodation were significantly increased, while exophthalmetry was increased. Conclusions: The relationship between visual functions and exophthalmetry were found to be statistically significant. It could be used as the clinical criteria for prescription of binocular inspections.

• Atmosphere
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• v.18 no.3
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• pp.225-235
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• 2008

Sulfur hexafluoride ($SF_6$), man-made compound, has been paid attention as a potent greenhouse gas. After Kyoto Pototcol on Climate Change in 1997, nations established the policy aimed at minimizing release of $SF_6$ to atmosphere. We have developed and operated an automatic analytical system for monitoring atmospheric $SF_6$ using gas chromatography with electron capture detector (GC-ECD) and packed separate-column. Here, we report and discuss 4-month record of atmospheric $SF_6$ concentrations monitored at Seoul National University (SNU) pilot station near the Kwanak Mountain, Seoul. Most of observed $SF_6$ concentrations were excessively high compared with Northern Hemisphere (NH) background trend obtained from National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) monitoring stations. And the observed $SF_6$ showed extremely wide variability ranging from 4.6 pptv to $1.1{\times}10^3$ pptv, which may be affected by local sources placed nearby. Simultaneous wind data with $SF_6$ measurements show that relatively high values of $SF_6$ correspond to weak wind as well as southerly. There are many engineering installations to the south of the station. The regional value of the atmospheric $SF_6$ estimated from the data selection by wind conditions is about 6.8 pptv. This value, which is similar to concentrations of urban areas, is higher than NH background concentration.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.56.2-56.2
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• 2010

The SPICA (SPace Infrared Telescope for Cosmology & Astrophysics) project is a next-generation astronomical mission optimized for mid- and far-infrared observation with a cryogenically cooled 3m-class telescope. Due to its high angular resolution and unprecedented sensitivity, SPICA will enable us to resolve many key issues in the present-day astronomy. As an international collaboration, KASI proposed the near-infrared instrument which is composed of two parts; (1) science observation with the capability of imaging and spectroscopy covering $0.7{\mu}m$ to $5{\mu}m$ (FPC-S) (2) fine guiding to stabilize and improve the attitude (FPC-G). Here, we introduce the science programs proposed for SPICA/FPC-S.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.147-155
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• 2004

Self-excited noise generation from laminar flames in thin annular jets of methane/air premixture has been investigated experimentally. Various flames were observed in this flow configuration, including conical shape flames, ring shape flames, steady crown shape flames, and oscillating crown shape flames. Self-excited noise with the total sound pressure level of about 70dB was generated from the oscillating crown shape flames for the equivalence ratio larger than 0.95. Sound pressure and $CH^*$ chemiluminescence were measured by using a microphone and a photomultiplier tube. The frequency of generated noise was measured as functions of equivalence ratio and premixture velocity. A frequency doubling phenomena have also been observed. The flame shape during flame oscillation was reconfirmed by a synchronized PIV experiment. The velocity and pressure field were obtained from PIV. The minimum pressure was formed near the edge of flame representing circulation. By comparing the results of sound pressure, flame luminosity and PIV, the noise source can be attributed to the flame front fluctuation near the edge of the oscillating crown-shape flames.

• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.129-141
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• 2018

This paper proposes a unified framework that overcomes four motion constraints including joint limit, kinematic singularity, algorithmic singularity and obstacles. The proposed framework is based on our previous works which can insert or remove tasks continuously using activation parameters and be applied to avoid joint limit and singularity. Additionally, we develop a method for avoiding obstacles and combine it into the framework to consider four motion constraints simultaneously. The performance of the proposed framework was demonstrated by simulation tests with considering four motion constraints. Results of the simulations verified the framework's effectiveness near joint limit, kinematic singularity, algorithmic singularity and obstacles. We also analyzed sensitivity of our algorithm near singularity when using closed loop inverse kinematics depending on magnitude of gain matrix.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.503-505
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• 2015

The galaxy cluster is an important object for investigating the large scale structure and evolution of galaxies. Recent wide and deep near-IR surveys provide an opportunity to search for galaxy clusters in the high redshift universe. We have identified candidate clusters of 0.8< z <1.2 from the $25deg^2$ SA22 field using an optical-near-IR dataset from merged UKIDSS DXS, IMS and CFHTLS catalogs. Using these candidates, we investigate the star forming activity of member galaxies. Consequently, at z ~1, the star forming activity of cluster galaxies is not distinguishable from those of field galaxies, which is different from members in local clusters. This means the environmental effect becomes more important for $M_{\ast}>10^{10}M_{\odot}$ galaxies at z <1.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.4
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• pp.382-390
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• 2009

The submerged body near the free surface is disturbed by the 1st and 2nd order wave forces, which results in unstable movements when no control is applied. In this paper, the vertical motions of the submerged body are analyzed, and the time-variant nonlinear system for the vertical motions of the submerged body is transformed to the time-invariant linear system in state space. Next, depth controller of the submerged body is designed by using LQR control, one of the modern optimal control technique. Numerical simulation shows that effective depth controls can be achieved by LQR control.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.108.2-109
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• 2003

The Gyeonggi-do Agricultural Research and Extension Services has developed a web-site (www.epilove.com) in collaboration with EPINET to provide information on agricultural weather and rice disease and insect pest management in Gyeonggi-do. Weather information includes near real-time weather data monitored by automated weather stations (AWS) installed at rice paddy fields of 11 Agricultural Technology Centers (ATC) in Gyeonggi-do, and weekly weather forecast by Korea Meteorological Administration (KMA). Map images of hourly air temperature and rainfall are also generated at 309m x 309m resolution using hourly data obtained from AWS installed at 191 locations by KMA. Based on near real-time weather data from 11 ATC, hourly infection risks of rice blast, sheath blight, and bacterial grain rot for individual districts are estimated by disease forecasting models, BLAST, SHBLIGHT, and GRAINROT. Users can diagnose various diseases and insects of rice and find their information in detail by browsing thumbnail images of them. A database on agrochemicals is linked to the system for disease and insect diagnosis to help users search for appropriate agrochemicals to control diseases and insect pests.