• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.615-620
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• 2002

Probability distribution of the sea surface slope is estimated using sun glitter images derived from visible radiometer on Geostationary Meteorological Satellite (GMS) and surface vector winds observed by spaceborne scatterometers. The brightness of the visible images is converted to the probability of wave surfaces which reflect the sunlight toward GMS in grids of 0.25 deg $\times$ 0.25 deg. Slope and azimuth angle required for the reflection of the sun's ray toward GMS are calculated for each grid from the geometry of GMS observation and location of the sun. The GMS images are then collocated with surface wind data observed by three scatterometers. Using the collocated data set of about 30 million points obtained in a period of 4 years from 1995 to 1999, probability distribution function of the surface slope is estimated as a function of wind speed and azimuth angle relative to the wind direction. Results are compared with those of Cox and Munk (1954a, b). Surface slope estimated by the present method shows narrower distribution and much less directivity relative to the wind direction than that reported by Cox and Munk. It is expected that their data were obtained under conditions of growing wind waves. In general, wind waves are not always developing, and slope distribution might differ from the results of Cox and Munk. Most of our data are obtained in the subtropical seas under clear-sky conditions. This difference of the conditions may be the reason for the difference of slope distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.1 s.244
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• pp.52-59
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• 2006

The vibration of hydraulic piston pumps is induced by the periodically changing cylinder chamber pressure whose waveform is significantly influenced by valve plate geometry. In this study, the force input to the housing of a bent-axis type hydraulic piston pump was computed by deriving the dynamic equations of its piston and cylinder barrel. The vibration intensity of the pump was represented by the acceleration amplitude of its housing. In order to comparatively evaluate the influence of valve plate geometry on the vibration of pump housing, two different types of valve plate were tested. The computed results showed good agreement with the experimental data, indicating that the vibration acceleration of pump housing is rather dependent on the variation amplitude of balance coefficient than the changing slope or overshoot of cylinder chamber pressure. It was also confirmed that the design effect of valve plates could be directly examined out by monitoring the vibration acceleration of pump housing.

• The Journal of Engineering Geology
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• v.2 no.2
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• pp.131-140
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• 1992

GIS(Geographic Information System) technology was applied for analysis of the potential degree of regional geologic hazard, especially landslide hazards in the suburb of Seoul City, whereby a regional geologic hazard map was produced. The factors causing a landslide such as slope geometry, geology, groundwater, soil property, rainfall and vegetation were incorporated through GIS in order to predict the potential hazards in this area. Cartographic simulation was finally made with these factors to produce a regional geologic hazard map. For this study, ARC/INFO and ERDAS systems were used in SUN 4-390 workstation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.1
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• pp.13-18
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• 2009

Accurate solar radiation data are critical to evaluate major physiological responses of plants. For most upland crops and orchard plants growing in complex terrain, however, it is not easy for farmers or agronomists to access solar irradiance data. Here we suggest a simple method using a sun-slope geometry based topographical coefficient to estimate daily solar irradiance on any sloping surfaces from global solar radiation measured at a nearby weather station. An hourly solar irradiance ratio ($W_i$) between sloping and horizontal surface is defined as multiplication of the relative solar intensity($k_i$) and the slope irradiance ratio($r_i$) at an hourly interval. The $k_i$ is the ratio of hourly solar radiation to the 24 hour cumulative radiation on a horizontal surface under clear sky conditions. The $r_i$ is the ratio of clear sky radiation on a given slope to that on a horizontal reference. Daily coefficient for slope correction is simply the sum of $W_i$ on each date. We calculated daily solar irradiance at 8 side slope locations circumventing a cone-shaped parasitic volcano(c.a., 570m diameter for the bottom circle and 90m bottom-to-top height) by multiplying these coefficients to the global solar radiation measured horizontally. Comparison with the measured slope irradiance from April 2007 to March 2008 resulted in the root mean square error(RMSE) of $1.61MJ\;m^{-2}$ for the whole period but the RMSE for April to October(i.e., major cropping season in Korea) was much lower and satisfied the 5% error tolerance for radiation measurement. The RMSE was smallest in October regardless of slope aspect, and the aspect dependent variation of RMSE was greatest in November. Annual variation in RMSE was greatest on north and south facing slopes, followed by southwest, southeast, and northwest slopes in decreasing order. Once the coefficients are prepared, global solar radiation data from nearby stations can be easily converted to the solar irradiance map at landscape scales with the operational reliability in cropping season.

• Spatial Information Research
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• v.1 no.1
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• pp.89-94
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• 1993

GIS was appl ied for analysis of the potfnt ial degree of regional geologic hazard, expecially landslide, in the suburb of Seoul city. Potential elements causing a landslide are geology, slope geometry, groundwater, soil property, rainfall and vegetation etc. These factors were incorporated through GIS in order to predict the potential hazards, and to produce a regional geologic hazard map in the study area, For this study, ARC/INFO and ERDAS systems were used in SUN4-390 workstation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.231-237
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• 2007

The torque ripple of the hydraulic pumps for the Electro-hydrostatic Actuators can disturb the cylinder position control under slewing speed operation condition. In principle, the periodic change of the reaction torque generated by a piston type pump is highly dependent on the waveform of its cylinder chamber pressure. In case of uni-directional pumps operating at constant speed, the transient overshoot and rising slope of the cylinder pressure can be adjusted by the precompression angle and notch shape of their valve plates. Therefore, the influence of the valve plate geometry on the torque ripple magnitude of a bent-axis type piston pump for EHA application was investigated in this study. The results showed that any improvement of the torque ripple of such a bi-directional pump can not be achieved by modifying the valve plate geometry, regardless of its operation speed.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.1
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• pp.43-47
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• 2003

Air temperature was continuously measured in hilly pear orchards at 4 sites with elevations of 10, 49, 104 and 253 m above sea level. The mean air temperature, averaged over the 10-month period from August 2001 to June 2002, decreased as the site elevation increased by 0.2$^{\circ}C$ per 100 m. This weak lapse condition was amplified during daytime by sun-slope geometry. But on most days an inversion condition began by sunset and persisted until the next sunrise. During the observation period, daily minimum temperature at the valley bottom was lower than that of the hilltop on 67% of the days, and the average temperature difference was 1.4$^{\circ}C$. Inversion of daily minimum temperature under clear sky conditions was stronger in spring and autumn than in winter with a maximum of 6$^{\circ}C$. Lapse condition was predominant in daily minimum temperature on rainy days, and the lapse rate was strongest in winter.

• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.2
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• pp.95-102
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• 2002

Spatial interpolation has become a common procedure in converting temperature forecasts and observations at irregular points for use in regional scale ecosystem modeling and the model based decision support systems for resource management. Neglection of terrain effects in most spatial interpolations for short term temperatures may cause erroneous results in mountainous regions, where the observation network hardly covers full features of the complicated terrain. A spatial interpolation model for daytime hourly temperature was formulated based on error analysis of unsampled site with respect to the site topography. The model has a solar irradiance correction scheme in addition to the common backbone of the lapse rate - corrected inverse distance weighting. The solar irradiance scheme calculates the direct, diffuse and reflected components of shortwave radiation over any surfaces based on the sun-slope geometry and compares the sum with that over a reference surface. The deviation from the reference radiation is used to calculate the temperature correction term by an empirical conversion formula between the solar energy and the air temperature on any sloped surfaces at an hourly time scale, which can be prepared seasonally for each land cover type. When this model was applied to a 14 km by 22 km mountainous region at a 10 m horizontal resolution, the estimated hourly temperature surfaces showed a better agreement with the observed distribution than those by a conventional method.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.1
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• pp.41-46
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• 2011

Reliable information on the surface solar radiation is indispensable for rebuilding food production system in the famine plagued North Korea. However, transfer of the related modeling technology of South Korea is not possible simply because raw data such as solar radiation or sunshine duration are not available. The objective of this study is restoring solar radiation data at 27 synoptic stations in North Korea by using satellite remote sensing data. We derived relationships between MODIS radiation estimates and the observed solar radiation at 18 locations in South Korea. The relationships were used to adjust the MODIS based radiation data and to restore solar radiation data at those pixels corresponding to the 27 North Korean synoptic stations. Inverse distance weighted averaging of the restored solar radiation data resulted in gridded surfaces of monthly solar radiation for 4 decadal periods (1983-1990, 1991-2000 and 2001-2010), respectively. For a direct application of these products, we produced solar irradiance estimates for each sub-grid cell with a 30 m spacing based on a sun-slope geometry. These products are expected to assist planning of the North Korean agriculture and, if combined with the already prepared South Korean data, can be used for climate change impact assessment across the whole Peninsula.