• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.2025-2033
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• 1999

In this paper, we forecast launching time of the commercial IMT-2000 service as feb. 2001, according to expert’s opinion, and most of they forecast rapid evolution. And, we propose two different models according to two cases for competition power of price for IMT-2000 service subscriber demand forecasting. In this paper, we combine the expert’s opinion method with the growth curve model for demand forecasting for new products in order to reduce error of the demand forecasting that haven’t past references. The estimation of needed coefficients for each growth curve model is based on experts’ subjective opinions.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1808-1813
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• 2007

하천유량은 수자원계획, 댐개발, 용수공급, 하천수질관리 등에 필요한 수자원 기본자료로서 정확도에 따라 국가 수자원계획이 좌우될 수 있는 중요한 자료이다. 본 연구는 낙동강 유역을 대상으로 7개 지점에 대한 2006년의 수문관측 자료 및 유량측정성과를 이용하여 유출특성을 분석하였다. 2006년도 낙동강 유역의 유량측정 지점 중 낙동강 본류에 해당하는 7개 지점에 대한 현장 유량측정 수행결과와 유량측정성과에 대한 수리특성 분석, 불확실도 분석 및 수위-유량관계곡선식을 개발하여 유량을 산정하였다. 산정된 유량에 대한 상 하류 유출 검토, 댐방류량과의 비교, 연유출률 검토, 주요 호우사상별 직접 유출률 검토, 평 저수시 동시유량 검토 등을 통하여 각 지점의 최종 유량을 확정하였다. 산정된 유출률은 대체로 양호한 결과를 보였으며, 부분적으로 계기수위가 불안정했던 지점들을 제외한 나머지 지점들의 유출률은 그 지점들의 특성을 감안할 경우 비교적 안정적인 범위 내의 유출특성을 보였다. 2005년도 유출률과 비교해 보면 전체적으로 다소 높게 나타났으나, 올해 장기간 집중된 강우 특성을 고려한다면 적절한 유출범위를 보인 것으로 판단된다. 향후 전문인력에 의한 현장 측정과 일상적인 검증과정을 통해서 정밀한 유량측정성과를 확보한다면, 보다 신뢰성있는 유량자료를 생산할 수 있을 것이며, 효과적인 치수 및 이수계획의 수립 등 수자원 개발을 위한 기반을 마련할 수 있을 것이다.

• Economic and Environmental Geology
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• v.23 no.4
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• pp.383-392
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• 1990

This study found that that dynamics of intensity of use and economic theory of derived demand can both be accommodated through an extensive translog demand model. The basic idea in this recognition is that the skewed life cycle empirical pattern of intensity of use plotted against per capita income is of lognormal form and this lognomal intensity of use model can be mathematically transformed into an eqivalent simple translog intensity of use model. Empirical results showed that this extensive traslog model, which is a flexible function and includes both the classical case of fixed coefficients and the dynamic case of varying coefficients of the explanatory variables, gave better forecasts than the original intensity of use model and other conventional models.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.397-404
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• 2012

Fragility curves show the probability of a system reaching a limit state as a function of some measure of seismic intensity. To obtain fragility curves of six and twelve story staggered wall structures with middle corridor, incremental dynamic analyses were carried out using twenty two pairs of earthquake records, and their failure probabilities for various intensity of seismic load were investigated. The performances of staggered wall structures with added columns along the central corridor and the structures with their first story walls replaced by columns were compared with those of the regular staggered wall structures. Based on the analysis results it was concluded that staggered wall structures with central columns have the largest safety margin for the same level of seismic load.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.95-109
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• 2018

Recently, GRS (Geosynthetic Retaining Segmental) wall has been widely used as a method to replace concrete retaining wall because of its excellent structural stability and economic efficiency. It has been variously applied for foundation, slope, road as well as retaining wall. The GRS wall system, however, has a weak point that is serious crack of wall due to stress concentration at curved part of it. In this study, therefore, behaviour of GRS wall according to shape of it, shich has convex and concave, are analysed and compared using Finite Element analysis as the fundamental study for design optimization. Results including lateral deflection, settlements of ground surface and wall obtained from 2D FE analysis are compared between straight and curved parts from 3D FE analysis.

• Journal of Internet Computing and Services
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• v.19 no.5
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• pp.55-66
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• 2018

Since existing server-based authentications use vulnerable password-based authentication, illegal leak of personal data occurs frequently. Since this can cause illegal ID compromise, alternative authentications have been studied. Recently token-based authentications like OAuth 2.0 or JWT have been used in web sites, however, they have a weakness that if a hacker steals JWT token in the middle, they can obtain plain authentication data from the token, So we suggest a new authentication method using the verification token of authentic code to encrypt authentication data with effective time. The verification is to compare an authentication code from decryption of the verification-token with its own code. Its crypto-method is based on do XOR with ECDH session key, which is so fast and efficient without overhead of key agreement. Our method is outstanding in preventing the personal data leakage.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.296-303
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• 2014

Recently a system is being required to replace ILS due to increasing air traffic. In this paper, Curved approach is applied to an airport where ILS approach cannot be applied due to its geographical condition and restricted aerospace condition, and verified by flight test. After analysing conditions of Tae-an airfield of Hanseo University with virtual ILS approach, airfield applicability was evaluated by Curved approach using by GPS. Normally simulation is performed after establishing approach procedure using electric map, but recently verification is being performed by flight test without simulation because accuracy and reliability are increased. In this paper, established procedure is verified modified by flight test with Pilot Test and Auto Pilot test and controllability and passenger's stability were also checked.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.6 no.1_2
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• pp.49-57
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• 1973

Based on the fork length data of 1960 and on the fishery statistical data of 1968, 1970 and 1971, a research was made on the migration of the Pacific saury in the waters off the eastern coast of Korea. The population is divided into four groups in terms of size as shown in Fig. 5. The four groups demonstrate more or less different pattern of migration, both temporally and spatially. Northward migration is brought out in order of size, i. e., the smaller move northward earlier than the larger do, and the order is reverse in the case of southward migration. The migration routes of each size group are presented in Fig. 8. Whether the fish takes its course to the north or the south, its distribution centroid within the fishing grounds is traced in general following the line between $130^{\circ}$ and $130^{\circ}$130^{\circ$x. long., although longitudinally a pronounced annual bias is found in its month position. The moving pattern of the distribution centroid is assumed to be related with the abundance of each group to a considerable extent.

• Journal of the Korean Geotechnical Society
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• v.37 no.1
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• pp.17-27
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• 2021

It takes a long period to conduct the test on soil water retention curve (SWRC) in unsaturated soils. To improve such a problem, the high air entry disk has been replaced by micro-membrane. After the soil water retention test, the results by the micro-membrane were compared with those by the ceramic disk. Multiple samples in 5 regions were used to validate that SWRCs by micro-membrane are equivalent to those by ceramic disk. Therefore, a quick procedure based on micro-membrane has been developed, which makes it available to acquire much soil water retention data. The data of SWRCs were obtained for total 29 samples using ceramic disk or micro-membrane. For Korean weathered soils, the unsaturated hydraulic characteristics are sorted by three groups. Based on van Genuchten model, the group is divided by the parameter n, and the value of n could be correlated to the void ratio as each function.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.387-393
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• 2010

This paper studies static crack growth of asphalt pavement using the extended finite element method (XFEM). To consider nonlinear characteristics of asphalt concrete, a viscoelastic constitutive equation using the Maxwell chain is used. And a linear cohesive crack model is used to regularize the crack. Instead of constructing the viscoelastic constitutive law from the Prony approximation of compliance and retardation time measured experimentally, we use a smooth log-power function which optimally fits experimental data and is infinitely differentiable. The partial moduli of the Maxwell chain from the log-power function make analysis easy because they change more smoothly in a more stable way than the ordinary method such as the least square method. Using the developed method, we can simulates the static crack growth test results satisfactorily.