• Journal of Astronomy and Space Sciences
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• v.31 no.4
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• pp.335-340
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• 2014

There have been many suggestions and much debate about climate variability during the Holocene. However, their complex forcing factors and mechanisms have not yet been clearly identified. In this paper, we have examined the Holocene climate cycles and features based on the wavelet analyses of $^{14}C$, $^{10}Be$, and $^{18}O$ records. The wavelet results of the $^{14}C$ and $^{10}Be$ data show that the cycles of ~2180-2310, ~970, ~500-520, ~350-360, and ~210-220 years are dominant, and the ~1720 and ~1500 year cycles are relatively weak and subdominant. In particular, the ~2180-2310 year periodicity corresponding to the Hallstatt cycle is constantly significant throughout the Holocene, while the ~970 year cycle corresponding to the Eddy cycle is mainly prominent in the early half of the Holocene. In addition, distinctive signals of the ~210-220 year period corresponding to the de Vries cycle appear recurrently in the wavelet distribution of $^{14}C$ and $^{10}Be$, which coincide with the grand solar minima periods. These de Vries cycle events occurred every ~2270 years on average, implying a connection with the Hallstatt cycle. In contrast, the wavelet results of $^{18}O$ data show that the cycles of ~1900-2000, ~900-1000, and ~550-560 years are dominant, while the ~2750 and ~2500 year cycles are subdominant. The periods of ~2750, ~2500, and ~1900 years being derived from the $^{18}O$ records of NGRIP, GRIP and GISP2 ice cores, respectively, are rather longer or shorter than the Hallstatt cycle derived from the $^{14}C$ and $^{10}Be$ records. The records of these three sites all show the ~900-1000 year periodicity corresponding to the Eddy cycle in the early half of the Holocene.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.330-346
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• 1997

Korea Multi-Purpose Satellite I (KOMPSAT-I, the first multi-purpose Korean satellite) will be launched in the third quarter of 1999, which is operated on the sun-synchronous orbit for cartography, ocean color monitoring, and space environment monitoring. The main mission of Electro-Optical Camera(EOC) which is one of KOMPSAT-I sensors is to provide images for the production of scale maps of Korea. EOC collects panchromatic imagery with the ground sample distance of 6.6m at nadir through visible spectral band of 510~730nm. For determining KOMPSAT-I crossing time over Korea, this study examines the diurnal variation of solar and atmospheric variables that can exert a great influence on the EOC imagery. The results are as follows: 1) After 10:30 a.m. at the winter solstice, solar zenith angle is less than $70^{\circ}$ and expected flux of EOC spectral band over land for clear sky is greater than about $2.4mW/cm^2$. 2) For daytime the distribution of cloud cover (clear sky) shows minimum (maximum) at about 11:00 a.m. Although the occurrence frequency of poor visibility by fog decreases from early morning toward noon, its effect on the distribution of clear sky is negligible. From the above examination it is concluded that determining KOMPSAT-I crossing time over Korea between 10:30 and 11:30 a.m. is adequate.

• Proceedings of the KOR-KST Conference
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• 2003.02a
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• pp.127-150
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• 2003

This research presents a novel application of static traffic assignment methods, but with a variable time value, for estimating the market share of a high-speed rail (HSR) in the NW-SE corridor of Korea which is currently served by the airline (AR), conventional rail (CR), and highway (HWY) modes. The proposed model employs the time-space network structure to capture the interrelations among all competing transportation modes, and to reflect their supply- and demand-sides constraints as well as interactions through properly formulated link-node structures. The embedded cost function for each network link offers the flexibility for incorporating all associated factors, such as travel time and fare, in the model computation, and enables the use of a distribution rather than a constant to represent the time-value variation among all transportation mode users. To realistically capture the tripmakers' value-of-time (VOT) along the target area, a novel method for VOT calibration has been developed with aggregate demand information and key system performance data from the target area. Under the assumption that intercity tripmakers often have nearly "perfect" travel information, one can solve the market share of each mode after operations of HSR for each O-D pair under the time-dependent demand with state-of-the-art traffic assignment. Aside from estimating new market share, this paper also investigated the impacts of HSR on other existing transportation modes.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.133-142
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• 2012

The objective of this study was to correct the bias of the Representative Concentration Pathways (RCP)-based future precipitation data using a quantile mapping method. This method was adopted to correct extreme values because it was designed to adjust simulated data using probability distribution function. The Generalized Extreme Value (GEV) distribution was used to fit distribution for precipitation data obtained from the Korea Meteorological Administration (KMA). The resolutions of precipitation data was 12.5 km in space and 3-hour in time. As the results of bias correction over the past 30 years (1976~2005), the annual precipitation was increased 16.3 % overall. And the results for 90 years (divided into 2011~2040, 2041~2070, 2071~2100) were that the future annual precipitation were increased 8.8 %, 9.6 %, 11.3 % respectively. It also had stronger correction effects on high value than low value. It was concluded that a quantile mapping appeared a good method of correcting extreme value.

• Earthquakes and Structures
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• v.12 no.2
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• pp.153-163
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• 2017

The underlying goal of the present paper is to investigate soil and structural uncertainties on impedance functions and structural response of soil-shallow foundation-structure (SSFS) system using Monte Carlo simulations. The impedance functions of a rigid massless circular foundation resting on the surface of a random soil layer underlain by a homogeneous half-space are obtained using 1-D wave propagation in cones with reflection and refraction occurring at the layer-basement interface and free surface. Firstly, two distribution functions (lognormal and gamma) were used to generate random numbers of soil parameters (layer's thickness and shear wave velocity) for both horizontal and rocking modes of vibration with coefficients of variation ranging between 5 and 20%, for each distribution and each parameter. Secondly, the influence of uncertainties of soil parameters (layer's thickness, and shear wave velocity), as well as structural parameters (height of the superstructure, and radius of the foundation) on the response of the coupled system using lognormal distribution was investigated. This study illustrated that uncertainties on soil and structure properties, especially shear wave velocity and thickness of the layer, height of the structure and the foundation radius significantly affect the impedance functions, and in same time the response of the coupled system.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.287-294
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• 2004

To predict the temperature distribution around a underground rock storage cavern, two- and three- dimensional numerical analysis using FLAC was conducted. The effects of groundwater and latent heat on thermal properties were considered in numerical calculation. The temperature estimated by FLAC are compared with the temperature measured for 5-year operation at Gonjiam storage cavern. Estimated and measured temperatures showed great discrepancy when thermal properties from laboratory tests were used and showed good agreement when the effects from 20% of volumetric water fraction and latent heat were considered. However, the discrepancy still increased with operation time due to the heat flow from ground surface. Three-dimensional numerical models were established to closely approximate the boundary condition of the test site, and numerical results better agreement when groundwater and latent heat effects were considered.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.58-65
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• 2009

The paper identifies noise characteristics of a nonliner image sensor model which reflects a saturation effect of each detector pixel and extends the result to estimate an image SNR (Signla-to-Noise Ratio) distribution over all the pixels in a detector. In particular, nonlinearity of a pixel is studied from two perspectives of including asymmetry of a noise PDF (Probability Distribution Function) and enhancing a pixel SNR value, in comparison to a linear model. It is noted that the proposed image SNR distribution function is useful to effectively select new optimal operation parameter values: an integration time and an pixel-summing number, even after a launch campaign, assuming sensor gain degradation in orbit or inevitable modification of some operation parameter values due to space contingency.

• Journal of the Korean housing association
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• v.23 no.1
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• pp.19-26
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• 2012

This study examines how fence demolition may change the thermal environments of external spaces of houses and suggests what factors need to be considered when a fence is demolished. The results of the research are summarized as follows. In terms of the surface temperature, there was no significant difference in all time plots after the removal of all materials. However, applying greening methods (changing the surface materials, planting trees, and building a green roof following fence demolition) could lower the surface temperatures, calling for proper plans for various greening methods. The MRT results indicates that walls block solar radiation and provide shade, reducing radiant heat from roads and surrounding structures during the daytime when solar radiation directly effects surface temperatures. Also, the application of greening methods such as planting vegetation and trees could have shading and evapotranspiration effects, leading to a lower temperature distribution. The HIP results were similar to the MRT results. They indicated that walls block solar radiation within the residential sections and provide shade, resulting in a lower temperature distribution during the daytime. However, areas where greening methods such as a green roof or tree planting were applied showed $1{\sim}2^{\circ}C$ difference in temperature distribution.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.995-1001
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• 2010

Biogeography is the study of the distribution of biodiversity over space and time. We report the development of a prototype database that maps of microbial diversity in the context of the geochemical and geological environment and geographic location. It aims to reveal where organisms live, and at what abundance in nation wide. Microbial data collected from agricultural land during 1999 to 2007 were categorized for mapping with ArcGIS program. Distribution maps of bacteria, fungi, Bacillus and gram negative bacteria of agricultural land showed different patterns from each other. Microbial biomass content investigated in year of 2007 was higher than in 1999.

• Journal of Information Processing Systems
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• v.15 no.4
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• pp.820-832
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• 2019

Estimation of accurate blood volume flow in ultrasound Doppler blood flow spectrograms is extremely important for clinical diagnostic purposes. Blood volume flow measurements require the assessment of both the velocity distribution and the cross-sectional area of the vessel. Unfortunately, the existing volume flow estimation algorithms by ultrasound lack the velocity space distribution information in cross-sections of a vessel and have the problems of low accuracy and poor stability. In this paper, a new robust ultrasound volume flow estimation method based on multigate (RMG) is proposed and the multigate technology provides detail information on the local velocity distribution. In this method, an accurate double iterative flow velocity estimation algorithm (DIV) is used to estimate the mean velocity and it has been tested on in vivo data from carotid. The results from experiments indicate a mean standard deviation of less than 6% in flow velocities when estimated for a range of SNR levels. The RMG method is validated in a custom-designed experimental setup, Doppler phantom and imitation blood flow control system. In vitro experimental results show that the mean error of the RMG algorithm is 4.81%. Low errors in blood volume flow estimation make the prospect of using the RMG algorithm for real-time blood volume flow estimation possible.