• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4123-4144
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• 2016

Vehicular Ad Hoc Networks (VANETs) utilize radio propagation models (RPMs) to predict path loss in vehicular environment. Modern urban vehicular environment contains road infrastructure units that include road tunnels, straight roads, curved roads flyovers and underpasses. Different RPMs were proposed in the past to predict path loss, but modern road infrastructure units especially flyovers and underpasses are neglected previously. Most of the existing RPMs are computationally complex and ignore some of the critical features such as impact of infrastructure units on the signal propagation and the effect of both static and moving radio obstacles on signal attenuation. Therefore, the existing RPMs are incapable of predicting path loss in flyovers and underpass accurately. This paper proposes an RPM to predict path loss for vehicular communication on flyovers and inside underpasses that considers both the static and moving radio obstacles while requiring only marginal overhead. The proposed RPM is validated based upon the field measurements in 5 GHz frequency band. A close agreement is found between the measured and predicted values of path loss.

• 경영과학
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• 제22권1호
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• pp.15-26
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• 2005

The bootstrap is a method of computational inference that simulates the creation of new data by resampling from a single data set. We propose a new job for the bootstrap: generating inputs from one historical trace using Threshold Bootstrap. In this regard, the most important quality of bootstrap samples is that they be functionally indistinguishable from independent samples of the same stochastic process. We describe a quantitative measure of difference between two time series, and demonstrate the sensitivity of this measure for discriminating between two data generating processes. Utilizing this distance measure for the task of generating inputs, we show a way of tuning the bootstrap using a single observed trace. This application of the threshold bootstrap will be a powerful tool for Monte Carlo simulation. Monte Carlo simulation analysis relies on built-in input generators. These generators make unrealistic assumptions about independence and marginal distributions. The alternative source of inputs, historical trace data, though realistic by definition, provides only a single input stream for simulation. One benefit of our method would be expanding the number of inputs achieving reality by driving system models with actual historical input series. Another benefit might be the automatic generation of lifelike scenarios for the field of finance.

• 한국농공학회지
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• 제17권4호
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• pp.4001-4008
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• 1975

The economic evaluation of the feasibility of expanding fully irrgated agriculture in the Ogseo project must consider preproject yields of rice under rainfed and partially irrigated paddy cultivation in order to assess incremental incomes from irrigation. Statistical data on yields available from official sources and field surveys conducted in the project area do not specify whether given unit yields refer to actually cropped or potentially cropped lands. This latter factor obviously affects any evaluation of marginal benefits to be derived from irrigation as the extent of rainfed areas actually cropped varies from year to year according to rain fall at the critical growth periods for low land rice. Although less dependent on direct rainfall, yields from partially irrigated lands are also highly affected by seasonal rainfalls. In this paper on attempt has been made to determine average yield under rainfed and partially irrigated conditions by relating yields to a available water. For rainfed paddy cultivation, the analysis discriminates between effects of rain deficiencies during transplanting and subsquent growth periods. For partially irrigated paddy cultivation, seasonal rainfalls have been considered, implying sufficient storage capacity for supplementary irrigation. The average yield of rainfed paddy has been calculated as 2.11 t/ha and that of partially irrigated paddy as 2.8 t/ha. Assuming even division between these two water supply patterns of areas not fully irrigated, a composite yield of 2.46 t/ha is oftained. This figure will be adopted as the basis for the on-going studies and project evaluation.

• Journal of Species Research
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• 제6권spc호
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• pp.185-214
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• 2017

The genus Phyllopodopsyllus T. Scott, 1906 is nearly cosmopolitan and contains around 60 valid species, but has not been previously recorded in Korea. One of the reasons is probably the paucity of research in marginal habitats, such as marine interstitial. I describe two new species here. Numerous specimens of both sexes of P. kitazimai sp. nov. were collected from a beach near Yeongdeok, while only two females of P. busanensis sp. nov. were collected from a beach near Busan. The new species differ in numerous macro-morphological characters, such as the segmentation and armature of the antennula, armature of the mandibula, maxillula, maxilliped, and the first three swimming legs, as well as the shape of the caudal rami and the female genital field. However, they show very little difference in the number and position of cuticular organs (pores and sensilla) on all somites, which might prove these rarely used micro-characters to be useful in the reconstruction of phylogenetic relationships in this group of harpacticoids. Both species have their closest relatives in Japan. Phyllopodopsyllus kitazimai is morphologically most similar to P. punctatus Kitazima, 1981, but can be distinguished by much longer third exopodal segments of the third and fourth swimming legs. Phyllopodopsyllus busanensis shares the largest number of morphological similarities with P. setouchiensis Kitazima, 1981, but can be distinguished by shorter caudal rami. A key to species is also provided.

• 천문학회보
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• 제39권2호
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• pp.53.2-53.2
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• 2014

Radial color gradient of early type galaxies (ETGs) is a key tool for studying the evolution of these galaxies. In this work, we investigated whether ETGs having negative or positive color gradients show any distinguishable characteristics in the galaxy properties. We selected sample of 211 ETGs at 0.01 < z < 0.5 in the Spitzer FLS field, then we constructed u-R color gradients. We obtained the stellar mass, specific star formation rate and fluxes of emission lines of each ETG from MPA-JHU DR7 catalog. Spitzer IRAC and MIPS 24 micron data were used to detect dust emission from the ETGs. Preliminary result shows that less massive galaxies are likely to have positive color gradients, which is probably due to the ongoing star formation in the galaxy core. Almost all AGNs have negative color gradients. This probably is because AGNs are located in relatively massive galaxies with little ongoing star formation. There exists a marginal difference in the percentage of galaxies with PAH emission between ETGs having positive color gradient and negative color gradient. This also supports that ETGs with positive color gradient are galaxies having enhanced star formation.

• 한국광학회지
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• 제15권3호
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• pp.278-284
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• 2004

지속시간이 펨토초 수준에 이르는 빛펄스의 전기장 및 위상의 시간적 변화를 잴 수 있는 "이차조화파 발생 프로그(SHG FROG: Second Harmonic Generation Frequency Resolved Optical Gating)" 장치 및 소프트웨어를 개발하고 성능을 확인하였다. 이 장치를 써서 잰 실험값으로부터 빛펄스를 복원하는데는 "주요성분 일반 투영(PCGP: Principal Component Generalized Projection)" 방식에 더하여 프로그 궤적의 주파수 및 시간지연 "한계값(marginal)"과 이차조화파의 분광분포에 대한 조건을 덧붙임으로써 복원과정의 안정성과 수렴속도를 개선하였다.

• Journal of the Korean Wood Science and Technology
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• 제27권4호
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• pp.15-19
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• 1999

Three wood coffins of Chosun Dynasty period buried about 450 years ago were excavated in the sound condition in Andong area in the early 1998. The proprietors of wood coffins were grandparents, Mr. Myoung Jong Lee and Mrs. Mun, and their grandson, Mr. Eung Tae Lee, and the social standing of their family was known to belong to the nobility in those days by the clan genealogy. All the wood coffins investigated through light microscopy had same anatomical characteristics as follows: abrupt to somewhat abrupt tracheid transition from earlywood to latewood; normal longitudinal and horizontal resin canals with thin-walled epithelium; tylosoids in resin canals; bordered pits frequently in 1 row on radial walls of tracheids; 1 or 2 window-like pits per cross-field; uniseriate and fusiform rays; heterogeneous rays composed of body ray parenchyma cells and marginal ray tracheids or homgeneous rays composed of only ray tracheids; dentate ray tracheids; occasional trabeculae traversing tracheids in radial direction. Based on theses microscopic characteristics, all the wood coffins were identified to be Korean red pine (Pinus densiflora) or Korean black pine (Pinus thunbergii). Korean black pine growing naturally in coastal area might not be probable because the site of excavation, Andong area, was mountainous and inland area of Korea Thus, Korean red pine was thought to be the possible species for the wood coffins because of its natural distribution through the Korean Peninsula and the easy availability.

• 한국지구과학회지
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• 제23권1호
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• pp.15-29
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• 2002

Bayesian inversion for gravity and resistivity data was performed to investigate the cavity structure appearing as a lava tunnel in Cheju Island, Korea. Dipole-dipole DC resistivity data were proposed for a prior information of gravity data and we applied the geostatistical techniques such as kriging and simulation algorithms to provide a prior model information and covariance matrix in data domain. The inverted resistivity section gave the indicator variogram modeling for each threshold and it provided spatial uncertainty to give a prior PDF by sequential indicator simulations. We also presented a more objective way to make data covariance matrix that reflects the state of the achieved field data by geostatistical technique, cross-validation. Then Gaussian approximation was adopted for the inference of characteristics of the marginal distributions of model parameters and Broyden update for simple calculation of sensitivity matrix and SVD was applied. Generally cavity investigation by geophysical exploration is difficult and success is hard to be achieved. However, this exotic multiple interpretations showed remarkable improvement and stability for interpretation when compared to data-fit alone results, and suggested the possibility of diverse application for Bayesian inversion in geophysical inverse problem.

• 지역연구
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• 제11권1호
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• pp.61-78
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• 1995

This study begins with a question of what spatial impact international trade policy would have following the Uruguay Round, particularly focusing on agricultural trade liberalization in Korea. Based upon the neoclassical urban economic model, it first identifies the channel in which agricultural market opening can ultimately affect both rural and urban are as; $\circled1$ Free trade will depress domestic price of agricultural products, $\circled2$ which will in turn depreciate agricultural land price. $\circled3$ The decrease in marginal supply cost for urban land will then facilitate urban sprawl, provided that the government relaxes restrictions on urban-rural land conversion. Theoretical analysis is further refined by empirical considerations that distinguish agricultural land value solely for production purpose from that for future urban, uses, and that distinguish the urbanization effect caused by the fall in the supply cost of urban land from that caused by the existing high level of demand. Utilizing the estimate of bid-price for paddy field derived from the revenue-cost relationship of rice production, simulation results show that the urban-rural boundary under trade liberalization can expand outward up to 70-85km radius in the Seoul metropolitan area, suggesting the emergency of a metropolis or even a megalopolis which extends from Seoul to the central part of the country. Since the geographic extent of urbanization effect can vary depending upon the urban spatial structure, however, it is recommended that the redevelopment option in the built - up area should always be tied up with the issue of whether to deregulate rural-to-urban land conversion.

• 한국태양에너지학회 논문집
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• 제27권2호
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• pp.61-69
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• 2007

The final energy consumption in the building sector in Korea represents almost 20% of the total energy consumption. Besides, Space heating and hot water generation in Korea are based on fossil fuels, with a serious environmental impact. Despite the popularity of simple solar domestic hot water systems, active solar space heating remains, for various reasons, marginal. And thus, the aim of this paper is to demonstrate potentialities of solar assisted space heating systems, both technically and economically. From this study found that the solar heating system with CPC solar collectors integrated the roof of a single-story residential building shares $50{\sim}55%$ of the annual heating load.