• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.4
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• pp.265-269
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• 2009

A conference key agreement system is a scheme to generate a session key in a contributory manner in order to communicate with each other securely among participants. In this paper an efficient conference key agreement system is proposed by employing symmetric balanced incomplete block design(SBIBD), one class of block designs. The protocol presented not only minimizes the message overhead and message exchanging rounds but also makes every participant contribute evenly for generating a conference key. Our protocol constructs a conference key which takes modified Diffe-Helman form of ${\prod}_{i=0}^{v-1}R_i$, where v is the number of participants and $R_i$ is a random number generated from member i. In a special class of SBIBD, it takes only 3 rounds message exchange and message overhead is $O(v{\sqrt{v}})$. Our protocol can be proved as computationally difficult to calculate as discrete logarithms.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.6
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• pp.646-650
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• 2014

In this paper, in order to avoid the deterioration of the pattern classification performance which results from the curse of dimensionality, we propose a new feature selection method. The newly proposed feature selection method is based on Fuzzy C-Means clustering algorithm which analyzes the data points to divide them into several clusters and the concept of a function with fuzzy numbers. When it comes to the concept of a function where independent variables are fuzzy numbers and a dependent variable is a label of class, a fuzzy number should be related to the only one class label. Therefore, a good feature is a independent variable of a function with fuzzy numbers. Under this assumption, we calculate the goodness of each feature to pattern classification problem. Finally, in order to evaluate the classification ability of the proposed pattern classifier, the machine learning data sets are used.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.653-662
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• 2014

The data repositories for structural experiment information needs to be efficient to use in order to allow structural engineers and researchers to store and retrieve easily the information involved in the structural experiments. The data repositories can be evaluated in terms of the organization of the data repositories themselves and of the organization of the actual experiment information in the data repositories, which can be represented using classes and objects with their attributes. This paper proposes the evaluation criteria of attributes of the classes and objects. The evaluation criteria of the attributes of the classes, such as the number of attributes in class and the numbers of the data-valued and object entity-valued attributes, are used for understanding the complexity of the organization of the data repositories. The evaluation criteria of the attributes of the objects, such as the number of valued attributes in object, are used for describing how the actual experiment information is stored through the levels in the data repositories for the structural experiment information.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.3
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• pp.172-182
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• 2013

In this study we consider a flow line CONWIP system in which two types of product are produced. The processing times of each product type at each station follow an independent exponential distribution and the demands for the finished products of each type arrive according to a Poisson process. The demands that are not satisfied instantaneously are either backordered or lost according to the number of unsatisfied demands that exist at their arrival instants. For this system we develop an approximation method to obtain the performance measures such as steady state probabilities of the number of parts of each product type at each station, mean waiting times of backordered demands and the proportion of backordered demands. For the analysis of the proposed CONWIP system, we model the CONWIP system as a two class closed queueing network with a synchronization station and analyze the closed queueing network using a product-form approximation method for multiple classes developed by Baynat and Dallery. In the approximation method, each subsystem is analyzed using a matrix geometric method. Comparisons with simulation show that the approximation method provides fairly good results for all performance measures.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.7
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• pp.327-332
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• 2016

This study is a leading research project to develop an automatic grade decision making algorithm of a 6-years-old fresh ginseng. For this work, we developed a Ginseng image acquiring instrument which can take 4-direction's images of a Ginseng at the same time and obtained 245 jingen images using the instrument. The 12 parameters were extracted for each image by a manual way. Lastly, 4 parameters were selected depending on a Ginseng grade classification criteria of KGC Ginseng research institute and a survey result which a distribution of averaging 12 parameters. A pattern recognition classifier was used as a support vector machine, designed to "k-class classifier" using the OpenCV library which is a open-source platform. We had been surveyed the algorithm performance(Correct Matching Ratio, False Acceptance Ratio, False Reject Ratio) when the training data number was controlled 10 to 20. The result of the correct matching ratio is 94% of the $1^{st}$ ginseng grade, 98% of the $2^{nd}$ ginseng grade, 90% of the $3^{rd}$ ginseng grade, overall, showed high recognition performance with all grades when the number of training data are 10.

• Korean Journal of Remote Sensing
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• v.19 no.2
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• pp.170-179
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• 2003

In order to classify Land Use/Land Cover using multispectral images, we have to give consequence to defining proper classes and selecting training sample with higher class separability. The process of satellite hyperspectral image which has a lot of bands is difficult and time-consuming. Furthermore, classification result of hyperspectral image with noise is often worse than that of a multispectral image. When selecting training fields according to the signatures in the study area, it is difficult to calculate covariance matrix in some clusters with pixels less than the number of bands. Therefore in this paper we presented an overview of feature extraction methods for classification of Hyperion data and examined effectiveness of feature extraction through the accuracy assesment of classified image. Also we evaluated the classification accuracy of optimal meaningful features by class separation distance, which is also a method for band reduction. As a result, the classification accuracies of feature-extracted image and original image are similar regardless of classifiers. But the number of bands used and computing time were reduced. The classifiers such as MLC, SAM and ECHO were used.

• The Mathematical Education
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• v.58 no.3
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• pp.383-401
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• 2019

This study started with the idea that it is necessary to focus on common concepts and ideas among the subjects when conducting integrated education in high school. This is a preliminary study for developing materials that can be taught in mathematics in the context of already learning scientific concepts in high school. For this purpose, Mendel 's law of genetics was studied among the contents of biological subjects which are known to have relatively little connection with mathematics. The more common links between the two subjects are, the better, in order to integrate math and other subjects and develop materials for teaching. Therefore, in this study, we investigated not only the probability domain but also the concept of statistical domain. We have been wondering if there is a more abundant idea to connect between 'Mendel's law' and 'probability and statistics'. Through these anxieties, we could find that concepts such as 'likely equality' and 'permutation and combination' including 'a large number of laws' can be a link between two subjects. Based on this, we were able to develop class materials that correspond to classes. This study is expected to help with research related to development of integrated education support materials, focusing on mathematics.

• Human Ecology Research
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• v.56 no.6
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• pp.573-588
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• 2018

This study analyzed per capita consumption expenditure by the consumption quintile of Middle and Older Elderly Households and the variables that affected it. Sample of 2,983 households was collected from the 6th KLoSA in 2016. First, when comparing the HH's living expenses by the number of family members, two persons to a person ratio, more than six persons to a person ratio were 2.007 and 4.148, respectively. The ratio increased as the number of family member increased; however, the rate of ratio increase decreased. Second, the per capita living expenses for the first and fifth quintile were 5.11 million won and 16.93 million won at the per capita living expenses that applied the OECD's equivalence scale to the HH's living expenses. The per capita living expenses for the fifth quintile was 3.31 times higher than in the first quintile. Third, among the variables influencing per capita living expenses by the consumption quintile, the marital status was the significant for all consumption quintiles; however, HH's income, HH's total asset, HH's financial asset, pension, subjective perception of the economy class, home ownership, residence (metropolitan or small city), education (elementary school), participation groups were significant in some quintiles among all quintiles. Fourth, of the significant variables influencing per capita living expenses, the most influential variables were first quintile followed by second quintile, third quintile, fourth quintile, marital status, HH's income, home ownership, HH's total asset, participation groups, residence (metropolitan), subjective perception of the economy class, in order.

• Computers and Concrete
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• v.28 no.5
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• pp.521-532
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• 2021

Present paper focuses on the modeling of size effect on the compressive strength of normal concrete with the application of Discrete Element Method (DEM). Test specimens with different size and shape were cast and uniaxial compressive strength test was performed on each sample. Five different concrete mixes were used, all belonging to a different normal strength concrete class (C20/25, C30/37, C35/45, C45/55, and C50/60). The numerical simulations were carried out by using the PFC 5 software, which applies rigid spheres and contacts between them to model the material. DEM modeling of size effect could be advantageous because the development of micro-cracks in the material can be observed and the failure mode can be visualized. The series of experiments were repeated with the model after calibration. The relationship of the parallel bond strength of the contacts and the laboratory compressive strength test was analyzed by aiming to determine a relation between the compressive strength and the bond strength of different sized models. An equation was derived based on Bazant's size effect law to estimate the parallel bond strength of differently sized specimens. The parameters of the equation were optimized based on measurement data using nonlinear least-squares method with SSE (sum of squared errors) objective function. The laboratory test results showed a good agreement with the literature data (compressive strength is decreasing with the increase of the size of the specimen regardless of the shape). The derived estimation models showed strong correlation with the measurement data. The results indicated that the size effect is stronger on concretes with lower strength class due to the higher level of inhomogeneity of the material. It was observed that size effect is more significant on cube specimens than on cylinder samples, which can be caused by the side ratios of the specimens and the size of the purely compressed zone. A limit value for the minimum size of DE model for cubes and cylinder was determined, above which the size effect on compressive strength can be neglected within the investigated size range. The relationship of model size (particle number) and computational time was analyzed and a method to decrease the computational time (number of iterations) of material genesis is proposed.

• Health Policy and Management
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• v.33 no.2
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• pp.166-172
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• 2023

Background: To improve the support low-income individuals' medical expenses, it is necessary to think about ways to enhance the Catastrophic Health Expenditure Support Program. This study proposes expanding support criteria and changing the income standard. Methods: This study conducted simulations using national data from the National Health Insurance Service. Simulations performed for people who have used health services (n=172,764) in 2022 to confirm the Catastrophic Health Expenditure Support Program's size based on changes to the subject selection criteria. Results: As a result of the simulation with expanded criteria, the expected budget was estimated to increase between Korean won (KRW) 13.2 (11.5%) and 138.6 billion (37.4%), and the number of recipients increased between 41,979 (48.9%) and 150,317 (76.1%). The results of the simulation for the change in income criteria (applied to health insurance levels below the 50th percentile) estimated the expected budget to increase between KRW -8.9 (-7.8%) and 55.6 billion (15.0%) and the number of recipients to increase between -8,704 (-10.1%) and 41,693 (21.1%) compared to the current standard. Conclusion: The 2023 Catastrophic Health Expenditure Support Program's criteria were expanded as per the 20th Presidential Office's national agenda to alleviate the burden of medical expenses on the low-income class. In addition, The Catastrophic Health Expenditure Support Program needs to be integrated with other medical expense support policies in the mid- to long-term, and a foundation must be prepared to ensure the consistency of each system.