• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.727-746
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• 2018

The hash function RIPEMD-160 is a worldwide ISO/IEC standard and the hash function HAS-160 is the Korean hash standard and is widely used in Korea. On the basis of differential meet-in-the-middle attack and biclique technique, a preimage attack on 34-step RIPEMD-160 with message padding and a pseudo-preimage attack on 71-step HAS-160 without message padding are proposed. The former is the first preimage attack from the first step, the latter increases the best pseudo-preimage attack from the first step by 5 steps. Furthermore, we locate the linear spaces in another message words and exchange the bicliques construction process and the mask vector search process. A preimage attack on 35-step RIPEMD-160 and a preimage attack on 71-step HAS-160 are presented. Both of the attacks are from the intermediate step and satisfy the message padding. They improve the best preimage attacks from the intermediate step on step-reduced RIPEMD-160 and HAS-160 by 4 and 3 steps respectively. As far as we know, they are the best preimage and pseudo-preimage attacks on step-reduced RIPEMD-160 and HAS-160 respectively in terms of number of steps.

• Journal of Plant Biotechnology
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• v.43 no.1
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• pp.125-131
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• 2016

Pueraria lobata is a perennial legume plant that produces a variety of isoflavones, such as puerarin, daidzin and daidzein. These are metabolized to equol via dihydrodaidzein and tetrahydrodaidzein by the bacterial fermentation of natural isoflavone sources in the human intestines. In this study, we described the growth and accumulation of isoflavone in the hairy root of the Korean wild arrowroot according to the culture period, as well as dihydrodaidzein biosynthesis in hairy root extracts fermented with Pediococcus pentosaceus. Daily proliferation was best in DY1 cultured for 1 week. DY1 showed significant differences in daily production of puerarin and daidzin+daidzein, as compared to DJ7; furthermore, both were best in DY1 cultured for 1 week. The hairy root extract was fermented successfully with P. pentosaceus with confirmed production of dihydrodaidzein, an equol precursor formed by biotransformation. The results indicated that the growth of hairy roots and isoflavone accumulation in the hairy roots is best 1 week after culture. These results are expected to contribute to the mass production of hairy root and isoflavones as equol precursors from the Korean wild arrowroot and provide a basis for equol production by biotransformation in vitro.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.77-84
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• 2011

Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach for determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.

• Journal of The Korean Association For Science Education
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• v.16 no.4
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• pp.410-416
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• 1996

The purpose of this study is to determine which variable is the best predictor of students' science-related attitudes. Three influential variables were tested : students' science achievement. students' science process skills, and teachers' attitudes toward science. This study has been made on the basis of questionnaire from 205 1st graders in 5 different middle schools in Seoul. The instruments used for measuring attitudes were TOSRA and the questionnaire developed by Sung-Jae Pak(1980). The instrument used for measuring science process skills was a standardized test developed by Youne-Woo Lee(1989). The results was analyzed by multiple-regression in the statistical packages SPSS/PC+. The major findings of this study are as follows. 1. The mean score of students' science-related attitudes was 66.8, and there was no significant difference according to gender of students and teachers(p> .05). 2. The mean score of students' science process skills was 61.1, and there was no significant difference according to gender of students and teachers(p> .05). 3. Students' science process skills was the best predictor of students' science-related attitudes among three variables(R=0.3102, p< .05). 4. The subjects were divided into 2 groups by students' science achievement. In the high score group, students' science achievement was the best predictor of students' science-related attitudes (R=0.3406, p<.05). And in the low score group, none of the variables was related to students' science-related attitudes (p> .05). 5. In students who has a male science teacher, students' science process skill was the best predictor of students' science-related attitudes (R=0.3220, p<.05). And in students who has a female science teacher, students' science achievement was the best predictor of students' science-related attitudes (R=0.3480, p<.05).

• The Journal of the Acoustical Society of Korea
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• v.18 no.3E
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• pp.30-36
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• 1999

In this paper, we develop a hybrid speaker recognition system [1] enhanced by pre-recognizer and post-recognizer. The pre-recognizer consists of general speech recognition systems and the post-recognizer is a pitch detection system using adapted continuous wavelet transform (ACWT) to improve the performance of the hybrid speaker recognition system. Two schemes to design ACWT is considered. One is the scheme to search basis library covering the whole band of speech fundamental frequency (speech pitch). The other is the scheme to determine which one is the best basis. Information cost functional is used for the criterion for the latter. ACWT is robust enough to classify the pitch of speech very well, even though the speech signal is badly damaged by environmental noises.

• ETRI Journal
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• v.22 no.2
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• pp.1-10
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• 2000

Pattern recognition is one of the most common problems encountered in engineering and scientific disciplines, which involves developing prediction or classification models from historic data or training samples. This paper introduces a new approach, called the Representational Capability (RC) algorithm, to handle pattern recognition problems using radial basis function (RBF) models. The RC algorithm has been developed based on the mathematical properties of the interpolation and design matrices of RBF models. The model development process based on this algorithm not only yields the best model in the sense of balancing its parsimony and generalization ability, but also provides insights into the design process by employing a design parameter (${\delta}$). We discuss the RC algorithm and its use at length via an illustrative example. In addition, RBF classification models are developed for heart disease diagnosis.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.432-437
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• 2004

In this study, Pavement Management System(PMS) was developed to overcome the unscientific pavement management limitations of the past. PMS program is economic, efficient and scientific. Also, it produces the best maintenance method through exact judgement and logical analysis of pavement condition. First of all, the logical algorithm, that is such as investigation and analysis of pavement, detailed naked eye investigation and the estimation for whole system etc., was composed on the basis of the domestic and the outside data on PMS and pavement condition data of Seoul metropolitan. And then it was verified that this algorithm is suitable through the research examples of PMS data and the results of detailed naked eye investigation. Also, Geographic Information System(GIS) was integrated on PMS program. Therefore, PMS program was developed so as to use easily on the basis of the logical algorithm.

• Journal of the Korean Operations Research and Management Science Society
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• v.12 no.2
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• pp.42-50
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• 1987

This objective of this paper is to develop an efficient method with small memory requirement for a feed-mixing problem on a micro computer. First this method uses the decomposition principle to reduce the memory requirement. Next, the decomposition principle is modified to fit the problem. Further four different variations in solving subproblems are designed in order to improve efficiency of the principle. According to the test with respect to the processing time, the best variation is such that the dual simplex method is used, and the optimal basis of a previous subproblem is used as an initial basis, and the master problem is (M +1) dimensional. In general, the convergence of solution becomes slower near the optimal value. This paper introduces a termination criterion for a sufficiently good solution. According to the test, 5%-tolerence is acceptable with respect to the relation between the processing time and optimal value.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.6
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• pp.986-991
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• 2002

This paper presents off-line handwritten numeral recognition method by using Eigen-Vectors. In this method, numeral features are extracted statistically by using Eigen-Vectors through KL transform and input numeral is recognized in the feature space by the nearest-neighbor classifier. In our feature extraction method, basis vectors which express best the property of each numeral type within the extensive database of sample numeral images are calculated, and the numeral features are obtained by using this basis vectors. Through the experiments with the unconstrained handwritten numeral database of Concordia University, we have achieved a recognition rate of 96.2%.

• Structural Engineering and Mechanics
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• v.29 no.2
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• pp.117-134
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• 2008

A new adaptive dual reciprocity boundary element method for dynamic analysis of 3-D structures is presented in this paper. It is based on finding the best approximation function of a radial basis function (RBF) group $f=r^n+c$ which minimize the error of displacement field expansion. Also, the effects of some parameters such as the existence of internal points, number of RBF functions and position of collocation nodes in discontinuous elements are investigated in this adaptive procedure. Three numerical examples show improvement in dynamic response of structures with adaptive RBF in dual reciprocity with respect to ordinary BEM.