• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1219-1228
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• 2015

The Fixed Area ARFs (Area Reduction Factors) method has limitations in providing exact information about spatial distribution due to the lack of enough density of rain gauge stations. In this study the storm-centered ARF was evaluated between frontal and typhoon storm events utilizing radar precipitation. In estimating storm-centered ARFs, in order to consider the horizontal advection, direction, and spatial distribution of rain cells, the rotational angle of rainfall of each rainfall event and the optimum areal rainfall within the spatial rain cell envelope was taken into account. Compared with the frontal storm, the ARF of typhoon storm shows narrow range of variability. It is noted that the ARFs of frontal storm increases with the rainfall duration, but those of typhoon storm shows opposite pattern. As a result the typhoon ARFs appear greater than frontal ARFs for 1~3 hours of duration, but less for more than 6 hours of duration.

• Journal of the Korean Society of Clothing and Textiles
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• v.17 no.3
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• pp.470-474
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• 1993

This study carried out to get some fundamental data for designing lightweight bedding. In This study, the wool blanket, polyester/cotton blended blanket and down quilt were manufactured with a varied materials, structural factors such as yam count, fabric density respectivelyarn. And also, the thermal insulation value of the bedding were measured by warmth retaining tester. In addition, this paper examines the influence of varying materials, structural factors and blanket layers on the thermal insulation effect of the bedding. The main results obtained from this study are as follow : 1. The design of lightweight blankets make an attempting with a varying materials and structural factors such as yam count, fabric densityarn. 2. Almost, the design of lightweight blankets for polyester/cotton blended blanket and down quilt make an attempting without reduction in thermal insulation values. 3. The 6 layers of blanket have less thermal insulation value than the 6 times of blanket for under a layer have. About 27~32% decrease is observed in thermal insulation value of blanket for under 6 layer. 4. The thermal insulation value and areal weight of blankets have a positive relation between the thermal insulation value(Y) and areal weight(X) is based on the following equation. wool blanket : Y = 1.0850X + 0.4188 (r = 0.9992) PIC blended blanket : Y = 0.8845X + 0.3034 (r = 0.9999)

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.3-8
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• 2013

Bit patterned media (BPM) storage is one of the promising technologies to overcome the limitations of the conventional magnetic recording. However, there are some problems in a high areal density BPM storage, inter-track interference, inter-symbol interference and noise which are severely degrading performance of the system with reducing the bit error rate. In this paper, we present a simple iterative two-dimensional equalizer based on the contraction mapping theorem to mitigate these adverse effects. Furthermore, we examine that the channel characteristics of the proposed two-dimensional equalizer satisfies the convergence conditions. In the simulation we demonstrate the bit separation characteristics of the one-dimensional equalizer and the two-dimensional equalizer and evaluate the BER performance of the proposed equalizer comparing with the conventional equalizers. According to the results of experiments, the proposed equalizer is an promising equalizer with maintaining proper complexity for a high areal density BPM storage.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3855-3863
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• 2022

An evaluation of the radiation shielding performance of high-Z-particle-loaded polylactic acid (PLA) composite materials was pursued. Specimens were produced via fused deposition modeling (FDM) using copper-PLA, steel-PLA, and BaSO₄-PLA composite filaments containing 82.7, 75.2, and 44.6 wt% particulate phase contents, respectively, and were tested under broad-band flash x-ray conditions at the Sandia National Laboratories HERMES III facility. The experimental results for the mass attenuation coefficients of the composites were found to be in good agreement with GEANT4 simulations carried out using the same exposure conditions and an atomistic mixture as a model for the composite materials. Further simulation studies, focusing on the Cu-PLA composite system, were used to explore a shield design parameter space (in this case, defined by Cu-particle loading and shield areal density) to assess performance under both high-energy photon and electron fluxes over an incident energy range of 0.5-15 MeV. Based on these results, a method is proposed that can assist in the visualization and isolation of shield parameter coordinate sets that optimize performance under targeted radiation characteristics (type, energy). For electron flux shielding, an empirical relationship was found between areal density (AD), electron energy (E), composition and performance. In cases where ${\frac{E}{AD}}{\geq}2MeV{\bullet}cm{\bullet}g^{-1}$, a shield composed of >85 wt% Cu results in optimal performance. In contrast, a shield composed of <10 wt% Cu is anticipated to perform best against electron irradiation when ${\frac{E}{AD}}<2MeV{\bullet}cm{\bullet}g^{-1}$.

• Journal of Forest and Environmental Science
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• v.28 no.1
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• pp.56-62
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• 2012

There is little information about appropriate greenspace structures to satisfy aesthetic function in Korea. The purpose of this study was to analyze Korean's aesthetic preferences for greenspace structures concerned with urban tree plantings of an areal type to explore desirable greenspace landscapes. The study considered 5 structural variables of greenspace which were species composition, tree density, tree size, vertical and horizontal structure, and tree layout pattern. A photo-questionnaire was prepared through color simulations of different landscape types for each structural variable. Preference responses of an interval-scale rating from 214 respondents were statistically analyzed between landscape types and between respondent groups. Respondents preferred greenspace landscapes with diverse tree species to single species, higher tree density to lower density, larger trees to many smaller trees, multilayered and grouped plantings to single-layered and sparse plantings, and informal pattern to formal pattern. These preferences tended to be relatively higher for educated specialist and student groups than for other generalist group. Thus, multilayered and dense plantings in natural pattern including larger trees of diverse species, which are similar to ecological plantings, are recommended to increase aesthetic function of greenspace.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.68-69
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• 2009

Heat Assisted Magnetic Recording (HAMR) is one of the most promising candidates for high density magnetic storages over 1 Tb/$in^2$ areal density. Since the precise light delivery to the head is a key factor to realize HAMR application, it is required to establish the light delivery using micro laser module and micro actuator. For the careful control of micro actuator, a laser module was designed including laser diode, optical fiber, collimating lens, and fabricated V-groove substrate. In addition, the basic aligning method between the laser module and HAMR head was studied by the detection of current change in photo diode due to the amount of reflected light from the head.

• Journal of the Korean Geographical Society
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• v.46 no.1
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• pp.67-80
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• 2011

Choropleth mapping of population distribution is based on the assumption that people are uniformly distributed throughout each enumeration unit. Dasymetric mapping technique improves choropleth mapping by refining spatially aggregated data with residential information. Further, pycnophylactic interpolation can upgrade dasymetric mapping by considering population distribution of neighboring areas, while preserving the volumes of original units. This study proposed a combined solution of dasymetric mapping and pycnophylactic interpolation to improve the accuracy of population density distribution. Specifically, the dasymetric method accounts for the spatial distribution of population within each census unit, while pycnophylactic interpolation considers population distribution of neighboring area. This technique is demonstrated with 1990 census data of the Athens, GA. with land use land cover information derived from remotely-sensed imagery for the areal extent of populated areas. The results are evaluated by comparison between original population counts of smaller census units (census block groups) and population counts of the grid map built from larger units (census tracts) aggregated to the same areal units. The estimated populations indicate a satisfactory level of accuracy. Population distribution acquired by the suggested method can be re-aggregated to any type of geographic boundaries such as electoral boundaries, school districts, and even watershed for a variety of applications.

• Journal of Preventive Medicine and Public Health
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• v.37 no.1
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• pp.72-79
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• 2004

Objectives : This cross-sectional study aimed to quantify the relationship between the bone mineral density at the os calcis and the body mass composition in healthy children. Methods : The areal bone mineral density was measured at the os calcis with peripheral dual energy X-ray absorptiometry. The fat free mass, fat mass and percentage fat mass were measured using bioelectric impedance, in 237 Korean children, aged 9 to 12 years. The sexual maturity was determined by self assessment, using standardized series of the 5 Tanner stage drawings, accompanied by explanatory text. Results : From multiple linear regression models, adjusted for age, sexual maturity and height, the fat free mass was found to be the best predictor of the calcaneal bone mineral density in both sexes. About 15 and 20% variabilities were found in the calcaneal bone mineral densities of the boys and girls, respectively, which can be explained by the fat free mass. After weight adjustment, the percentage fat mass was negatively associated with the calcaneal bone mineral density in both sexes. Conclusions : The findings of this study suggest that the fat free mass, among the body compositions, is the major determinant of bone mineral density at the os calcis in Korean children aged 9 to 12 years. Obesity, defined as the percentage fat mass, is assumed to have a negative effect on the calcaneal bone density in children of the same weight.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.129-138
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• 2007

The cases of drunk driving accidents have been steadily increasing every year. The number of accidents was quadrupled from 7,303 cases in 1990 to 25,150 cases in 2004. In addition, the proportion of drunk driving accidents to total traffic accidents was 2.9% in 1990 but it increased to 13.0% in 2003. Studies of drunk driving accidents have been focusing on analyzing psychological decisive factors, classifying drivers' individual characters and types of drunk driving accidents by considering the location of drunk driving accidents. This study assumed that drunk driving accidents would have regular characteristics in respect to spatiality and analyzed its relation with spatial factors such as, accident black spot, the location of bars, the distance of drivers' houses, and spatio-temporal distributional characteristics through drawing density distribution and connecting the time of accidents. In order to achieve the goal of this study, the individual location information was organized and drawn as types of GIS data. From the result of density distribution using Kernel Density Mapping and analysis through the coefficient of areal correspondence, it was understood that drunk driving accidents correlates with some spatial factors.

• Journal of Korea Water Resources Association
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• v.35 no.3
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• pp.307-319
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• 2002

This study used the WGR model to generate the rainfall input and the modified Clark method to estimate the runoff with the aim of investigating how the errors from the areal average rainfall propagates to runoff estimates. This was done for several cases of raingauge density and also by considering several storm directions. Summarizing the study results are as follows. (1) Rainfall and runoff errors decrease exponentially as the raingauge density increases. However, the error stagnates after a threshold density of raingauges. (2) Rainfall errors more affect to runoff estimates when the density of raingauges is relatively low. Generally, the ratio between estimation errors of rainfall and runoff volumes was found much less than one, which indicates that there is a smoothing effect of the basin. However, the ratio between estimation errors of rainfall to peak flow becomes greater than one to indicate the amplification of rainfall effect to peak flow. (3) For the study basin in this studs no significant effect of storm direction could be found. However, the runoff error becomes higher when the storm and drainage directions are identical. Also, the error was found higher for the peak flow than for the overall runoff hydrograph.