• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.3
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• pp.31-41
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• 1988

Recently, the offshore structures are increasingly constructed to explore the natural resources. These offshore structures are to be designed to resist the repetitive wave forces. A probabilistic method for the fatigue analysis of offshore concrete structures is presented in this study. The present spectral fatigue analysis calculates wave forces first and then the transfer functions for unit waves from which stress spectra are determined. The calculated fatigue stresses may then be used to evaluate the fatigue damage of concrete structures. A simplified model for the estimation of fatigue damage of the structures, which employs only the probabilistic moments of the peak stress distribution without direct integration, is also proposed. The present study allows more realistic fatigue analysis of offshore concrete structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.655-669
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• 2018

In this study, we developed a hybrid forecasting model based on a four-parameter distribution which allows a simultaneous season-ahead forecasting for both seasonal rainfall and sub-daily rainfall in Han-River and Geum-River basins. The proposed model is mainly utilized a set of time-varying predictors and the associated model parameters were estimated within a Bayesian nonstationary rainfall frequency framework. The hybrid forecasting model was validated through an cross-validatory experiment using the recent rainfall events during 2014~2017 in both basins. The seasonal precipitation results showed a good agreement with the observations, which is about 86.3% and 98.9% in Han-River basin and Geum-River basin, respectively. Similarly, for the extreme rainfalls at sub-daily scale, the results showed a good correspondence between the observed and simulated rainfalls with a range of 65.9~99.7%. Therefore, it can be concluded that the proposed model could be used to better consider climate variability at multiple time scales.

• The KIPS Transactions:PartC
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• v.16C no.3
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• pp.373-382
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• 2009

we present more efficient method of a medium access for real-time ubiquitous sensor networks. Proposed MAC protocol is like the randomized CSMA/CA protocol, but unlike previous legacy protocols, it does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports from sensor nodes, we carefully decide to select a fixed-size contention window with non-uniform probability distribution of transmitting in each slot. We show that the proposed method can offer up to several times latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using a widely-used network simulation package, NS-2. We finally show that proposed MAC scheme comes close to meet bounds on the best latency being achieved by a decentralized CSMA-based MAC protocol for real-time ubiquitous sensor networks which is sensitive to latency.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.7
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• pp.9-16
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• 1999

We have investigated effects of local damage accumulation for ultra-low energy As and B ion implant using highly efficient molecular dynamics(MD) scheme. We simulated ion implantation by MD simulation using recoil ion approximation (RIA) method and local cell damage accumulation (LCDA) model proposed in the paper. Local damage accumulation probability function consisted of deposited energy in a unit cell, implant dose rate, target material, projectile atom, and recoil event number. The simulated results were good agreement with the experimental and other simulated results. The MDRANGE results without damage accumulation were different from SIMS data in the tail region. We also simulated 2 dimensional dopant and damage profiles using the local damage accumulation model and recoil ion approximation method.

• Korean Journal of Environment and Ecology
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• v.25 no.6
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• pp.903-910
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• 2011

The research was carried out in order to find climate factors which determine the distribution of Machilus thunbergii, and the potential habitats under the current climate and three climate change scenario by using classification tree (CT) model. Four climate factors; the minimum temperature of the coldest month (TMC), the warmth index (WI), summer precipitation (PRS), and winter precipition (PRW) : were used as independent variables for the model. The model of distribution for Machilus thunbergii (Mth-model) constructed by CT analysis showed that minimum temperature of the coldest month (TMC) is a major climate factor in determining the distribution of M. thunbergii. The area above the $-3.3^{\circ}C$ of TMC revealed high occurrence probability of the M. thunbergii. Potential habitats was predicted $9,326km^2$ under the current climate and $61,074{\sim}67,402km^2$(South Korea: $58,419{\sim}61,137km^2$, North Korea: $2,655{\sim}6,542km^2$) under the three climate change scenarios (CCCMA-A2, CSIRO-A2, HADCM3-A2). The Potential habitats was to predicted increase by 51~56%(South Korea: 49~51%, North Korea: 2~5%) under the three climate change scenarios. The potential expand of M. thunbergii habitats has been expected that it is competitive with warm-temperate deciduous broadleaf forest. M. thunbergii is evaluated as the indicator of climate change in Korea and it is necessary for M. thunbergii to monitor of potential habitats.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.337-349
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• 2006

Seven hundred and fifty one fractures of the rhyolitic tuffaceous rock masses were mapped using 6 scanlines placed on rock slope exposures that were within 8.02 km of Busan-Ulsan highway. These data were analyzed to find the number of fracture sets that exist in the rock slopes and the probability distributions of orientation, spacing, trace length and fracture size in 3-D for each of the fracture sets. All the fracture set orientation distributions exhibit high variability. The Fisher distributions were found to be unsuitable to represent the statistical distribution of orientation for most of the fracture sets. The probability distributions, gamma, exponential and lognormal were found to be highly suitable to represent the distribution of spacing and semi-trace length of fracture sets. In obtain-ing these distributions, corrections were applied for sampling biases associated with spacing and trace length. The generated fracture system in 3-D was used to make predictions of fracture traces for each fracture set on 2-D win-dows. Developed stochastic 3-D fracture network for the rock mass was validated by comparing statistical proper-ties of the observed fracture traces on scanlines with the predicted fracture traces on the scanlines. This exercise fumed out to be successful.

• Korean Journal of Food Science and Technology
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• v.52 no.6
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• pp.661-669
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• 2020

Samgak-Kimbap is a popular ready-to-eat (RTE) food at convenience stores, in Korea. Although Samgak-Kimbap is distributed through the cold chain supply system, inappropriate temperature storage conditions prior to consumption are a cause of concern. The objective of this study was to evaluate the risk of Staphylococcus aureus growth in Samgak-Kimbap in the retail market. The prevalence and contamination levels of S. aureus in Samgak-Kimbap (n=170) were monitored, and the predictive growth model of a five-strain cocktail of enterotoxin-producing S. aureus (SEA, SEB, SEC, SED, and SEE) was developed in Samgak-Kimbap as a function of temperature (4, 10, 11, 20, 25, and 37℃). We could not observe the growth of S. aureus and enterotoxin-producing S. aureus in Samgak-Kimbap at temperatures below 10℃. The probability of illness with S. aureus per serving of Samgak-Kimbap was 1.44×10-10 per day. The most influential factor in increasing the risk of foodborne illnesses was the contamination level of S. aureus in Samgak-Kimbap.

• Korean Journal of Agricultural and Forest Meteorology
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• v.26 no.1
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• pp.31-52
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• 2024

Considering the significant relationship between a tree's branch structure and physiology, understanding the detailed branch structure is crucial for fields such as species classification, and 3D tree modelling. Recently, terrestrial laser scanning (TLS) and quantitative structure model (QSM) have enhanced the understanding of branch structures by capturing the radius, length, and branching angle of branches. Previous studies examining branch structure with TL S and QSM often relied on mean or median of branch structure parameters, such as the radius ratio and length ratio in parent-child relationships, as representative values. Additionally, these studies have typically focused on the relationship between trunk and the first order branches. This study aims to explore the distribution of branch structure parameters up to the third order in Aesculus hippocastanum, Ginkgo biloba, and Prunus yedoensis. The gamma distribution best represented the distributions of branch structure parameters, as evidenced by the average of Kolmogorov-Smirnov statistics (radius = 0.048; length = 0.061; angle = 0.050). Comparisons of the mode, mean, and median were conducted to determine the most representative measure indicating the central tendency of branch structure parameters. The estimated distributions showed differences between the mode and mean (average of normalized differences for radius ratio = 11.2%; length ratio = 17.0%; branching angle = 8.2%), and between the mode and median (radius ratio = 7.5%; length ratio = 11.5%; branching angle = 5.5%). Comparisons of the estimated distributions across branch orders and species were conducted, showing variations across branch orders and species. This study suggests that examining the estimated distribution of the branch structure parameter offers a more detailed description of branch structure, capturing the central tendencies of branch structure parameters. We also emphasize the importance of examining higher branch orders to gain a comprehensive understanding of branch structure, highlighting the differences across branch orders.

• Korean Journal of Construction Engineering and Management
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• v.11 no.1
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• pp.113-121
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• 2010

Since the cut-down of the purchasing price of the feed in tariff(FIT) in 2008, the numbers of photovoltaic projects get decreased, contrary to investment expansion policy of government on renewable energy. The root cause of the decrease is the irrationality of the current purchasing price structure of FIT as well as the adversity of fund raising due to the global financial crisis. This study proposes the FIT calculating model (Cost & Benefit Risk Based Purchase Price Process : CBRP3) reflecting the fluctuation of cost and benefit risks. The first step is to establish the photovoltaic generation alternatives, and to calculate each distribution data of the investment and the power generation quantity. The FIT for each alternative is, then, assessed through simulations. Finally the proposed FIT scheme is compared to the present FIT scheme and future study subjects are derived.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.36-42
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• 1996

In this paper, we have proposed the robust estimation of HMM parameters which is based on CDDN(codeword dependent distance normalization)and codeword weighting by distance. The proposed method has used a distance normalization based on the characteristics of a codeword dependent distribution and have computed fuzzy contributions of codeword to a input vector with a fuzzy objective function. From experimental results, we have shown the effectiveness of the proposed method in that the correction rate of the proposed method is improved 4.5% over the conventional FVQ based method. Especially, the application of distance weighting to smoothing of output probability is improved the performance of 2.5% compared to distance based codeword weighting.