• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.4
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• pp.191-199
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• 2013

It is estimated and analyzed that the design wave height and the confidence interval (hereafter CI) according to the return period using the fourteen-year wave data obtained at Pusan New Port. The functions used in the extreme value analysis are the Gumbel function, the Weibull function, and the Kernel function. The CI of the estimated wave heights was predicted using one of the Monte-Carlo simulation methods, the Bootstrap method. The analysis results of the estimated CI of the design wave height indicate that over 150 years of data is necessary in order to satisfy an approximately ${\pm}$10% CI. Also, estimating the number of practically possible data to be around 25~50, the allowable error was found to be approximately ${\pm}$16~22% for Type I PDF and ${\pm}$18~24% for Type III PDF. Whereas, the Kernel distribution method, a typical non-parametric method, shows that the CI of the method is below 40% in comparison with the CI of the other methods and the estimated design wave height is 1.2~1.6 m lower than that of the other methods.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.394-404
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• 2013

In the present study, the characteristics of spectral peakedness parameter $Q_p$, bandwidth parameter ${\varepsilon}$, and spectral width parameter ${\nu}$ were analyzed as a first step to define the swell waves quantitatively. For the analysis, the joint probability density function of significant wave heights and peak periods were newly developed. The MCMC(Markov Chain Monte Carlo) simulations have been performed to generate the significant wave heights and peak periods from the developed probability density functions. Applying the simulated significant wave heights and peak periods to the theoretical wave spectrum models, the spectral shapes parameters were obtained and analyzed. Among the spectral shape parameters, only the spectral peakedness parameter $Q_p$, is shown to be independent with the significant wave height and peak wave period. It also best represents the peakedness of the spectral shape, and henceforth $Q_p$ should be used to define the swell waves with a wave period. For the field verification of the results, wave data obtained from Hupo port and Ulleungdo were analyzed and results showed the same trend with the MCMC simulation results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.73-80
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• 2005

This paper addresses a newly proposed start-up method of the HAUSAT-2 momentum wheel. The HAUSAT-2 is a 25kg class nanosatellite which is stabilized to earth pointing by 3-axis active control method. A momentum wheel performs two functions. It provides a pitch-axis momentum bias while measuring satellite pitch and roll attitude. Pitch control is accomplished in the conventional way by driving a momentum wheel in response to pitch attitude errors. Precession control and nutation damping are provided by driving the pitch axis magnetic torquer. A momentum wheel is nominally spinning at a particular rate and changes speed. This simulation study investigates the feasibility and performance of a proposed strategy for starting-up the wheel. A proposed strategy to start-up the wheel shows that a pitch momentum wheel can be successfully started-up to its nominal speed from rest and be stabilized to nadir pointing.

• Progress in Medical Physics
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• v.13 no.4
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• pp.187-194
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• 2002

In this work we investigated through Monte Carlo calculations the physical characteristics of the absorbed dose from the Ir-192 source used in brachytherapy The Monte Carlo calculations were performed using the code EGS4, which was extensively modified in order to handle cylindrical sources, phantoms, and energy distributions to suit out own purpose. From the results of the calculations for the $\beta$ -rays, it was found that they contribute on the average 0.02% to The total absorbed dose in the distance range of 0.5-5.0 cm from the source. This is due to the face that, although most of the primary $\beta$ -rays are absorbed in the source and encapsulation material, the resulting low energy braking radiation from them contribute to such a distance. The absorbed dose in the encapsulation material varied on the average from 2.8% for platinum down to 1.1% for iron. The radial dose functions obtained by our Monte Carlo calculations were consistent within $\pm$3% with those of the TG-43 report for the radial distance interval 0.5-10.0 cm from the source. The user code we wrote in this work can be used for other sources of different sizes and so it can be very useful in designing and producing the sources for brachytherapy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.169-177
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• 2017

In this paper, classification of spall and crack faults of gear teeth is studied by applying the ensemble empirical mode decomposition(EEMD) for the gear transmission error(TE). Finite element models of the gears with the two faults are built, and TE is obtained by simulation of the gears under loaded contact. EEMD is applied to the residuals of the TE which are the difference between the normal and faulty signal. From the result, the difference of spall and crack faults are clearly identified by the intrinsic mode functions(IMF). A simple test bed is installed to illustrate the approach, which consists of motor, brake and a pair of spur gears. Two gears are employed to obtain the TE for the normal, spalled, and cracked gears, and the type of the faults are separated by the same EEMD application process. In order to quantify the results, crest factors are applied to each IMF. Characteristics of spall and crack are well represented by the crest factors of the first and the third IMF, which are used as the feature signals. The classification is carried out using the Bayes decision theory using the feature signals acquired through the experiments.

• The Korean Journal of Applied Statistics
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• v.33 no.1
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• pp.25-46
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• 2020

This paper presents ordinal probit semiparametric regression models using Bayesian Spectral Analysis Regression (BSAR) method. Ordinal probit regression is a way of modeling ordinal responses - usually more than two categories - by connecting the probability of falling into each category explained by a combination of available covariates using a probit (an inverse function of normal cumulative distribution function) link. The Bayesian probit model facilitates posterior sampling by bringing a latent variable following normal distribution, therefore, the responses are categorized by the cut-off points according to values of latent variables. In this paper, we extend the latent variable approach to a semiparametric model for the Bayesian ordinal probit regression with nonparametric functions using a spectral representation of Gaussian processes based BSAR method. The latent variable is decomposed into a parametric component and a nonparametric component with or without a shape constraint for modeling ordinal responses and predicting outcomes more flexibly. We illustrate the proposed methods with simulation studies in comparison with existing methods and real data analysis applied to a Korean National Health and Nutrition Examination Survey (KNHANES) 2016 for investigating nonparametric relationship between smoking behavior and coffee intake.

• Journal of Korea Technology Innovation Society
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• v.11 no.3
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• pp.376-399
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• 2008

Science and technology (S&T) is one of the most important elements in a nation's competitiveness. In an effort to strengthen their national competitiveness, all countries are focusing on upgrading the level of eir S&T. With these factors in mind, Korea has increased its support of national research and development (R&D). In recent years, this added support has resulted in an increased interest in the effectiveness of R&D. We have made continuous efforts to enhance the accountability and effectiveness of R&D by strengthening performance evaluation and considering R&D evaluation results during the budget review (appropriation) process. In order to change to a performance based system, we need to develop objective and scientific indicators to measure and evaluate the quality of the research performance of R&D programs. One of the primary research outcomes is publications. The impact factor of publications is widely used to evaluate overall journal quality and the quality of the papers published therein. However, the use of impact factors has been criticised because they can vary greatly when works from different subject areas are compared. In order to overcome this limitation, we have developed three kinds of qualitative indicators, which are functions of the impact factor. Two of these qualitative indicators, Modified Rank Normalized Impact Factor and Ordinal Rank Normalized Impact Factor, are based on order statistics (rank) for all journals from a specific specialty. The third qualitative indicator, Relative Field Impact Factor, uses the average impact factor of all journals within a subject category. We also suggest a quantitative indicator, Percentage of Contribution. In this study, we suggest 4 indicators and use them to evaluate the performance of outcomes from three R&D programs supported by the Ministry of Education, Science & Technology. We also perform a simulation study to verify the effectiveness of the proposed indicators. It can be shown that the proposed Ordinal Rank Normalized Impact Factor is the most reliable and effective indicator for comparing research performance across subject categories. However, we recommend using previous indicators in combination with the proposed indicators in this study for the research evaluation of R&D programs.

• Spatial Information Research
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• v.5 no.2
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• pp.161-175
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• 1997

In spite of intense advances in the economy and technological progress which include massive and high-rise developments, landscape resources have either been destroyed or left to deteriorate. In recent years, efforts towards landscape management have emerged in the form of legislation and policies. However, relevant computer tools have unfortunately been insufficient in the field of landscape management. In addition, although there has been much research conducted for urban landscape management, pertinent information has not been recorded or managed efficiently. Therefore, this study developed a Landscape Information System for the purpose of managing urban landscape infOlmation and analyzing visual impacts in relation to urban development projects. Main functions of the Landscape Information System consist of the following: inputting and managing the attribute data as well as graphic data, querying attributes of urban landscape, and analyzing landscape impacts of developments. A case study was conducted for downtown Seoul. Using the system, a series of visual impact analyses were implemented at major viewpoints in the area. The results have shown that valuable landscape resources could be damaged by proposed development projects. Thus, the Landscape Information System developed in this study can be used as a major tool to manage urban landscape information efficiently and as the basis for decision-making regarding landscape simulation and visual impact analysis.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.12
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• pp.91-97
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• 2000

With the brilliant development of information communication and the rapid spread of internet, current network communication is carrying several up-to-date functions such as electronic commerce, activation of electro currency or electronic signature and will produce more advanced services in the future. Information communication network such as that electronic commerce would demand the more safe and transparent guard of network, and anticipate the more fast performance of network. In this paper, in order to meet the several demands, DES(data encryption standard) with parallel feistel structure, which feistel structure of the basic structure of DES is transformed into in parallel, is proposed. The existing feistel structure can't use pipeline method for the structural problem of DES itself-the propagation of error. therefore, this modified parallel feistel structure could improve largely the performance of DES which had to have the trade-off relation between data processing speed and data security and in addition a method proposed in SEED having adopted the modified parallel feistel structure shows more excellent secure function and/or fast processing ability. The used CAD Tool use Synopsys Ver. 1999. 10 in both of synthesis and simulation.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.276-285
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• 2020

In this study, accelerated chloride diffusion tests were performed on OPC(Ordinary Portland Cement) and FA(Fly Ash) concrete considering three levels o f W/B(Water to Binder) ratio o n 1,095 curing days. The accelerated chloride diffusion coefficient and the passed charge were evaluated in accordance with Tang's method and ASTM C 1202, and the resistance performance to chloride attack improved over time. FA concrete showed excellent resistance performance against chloride penetration with help of pozzolanic reaction. As the result of the passed charge, FA concrete showed durability improvement, "low" grade to "very low" grade, but OPC concrete changed "moderate" grade to "low" grade at 1,095 curing days. After assuming the design variables used for durability design as normal distribution functions, the service life of each case was evaluated by the probabilistic analysis method based on MCS(Monte Carlo Simulation). In FA concrete, the increase of probability of durability failure was lower than that of OPC concrete with increasing time, because the time-dependent coefficient of FA concrete was up to 3.2 times higher than OPC concrete. In addition, the service life by probabilistic analysis was evaluated lower than the service life by deterministic analysis, since the target probability of durability failure was set to 10%. It is considered that more economical durability design will be possible if the mo re suitable target probability of durability failure is set for various structures through researches on actual conditions and indoor tests under various circumstances.