• Bulletin of the Korean Mathematical Society
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• v.38 no.1
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• pp.157-161
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• 2001

In this paper, we prove that an affine manifold M is finitely covered by a manifold $\overline{M}$ where $\overline{M}$ is radiant or the tangent bundle of $\overline{M}$ has a conformally flat vector subbundle of the projective holonomy group of M admits an invariant probability Borel measure. This implies that$x^M$is zero.

• The Pure and Applied Mathematics
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• v.21 no.4
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• pp.271-279
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• 2014

Let $T_l$ be a transformation on the interval [-1, 1] defined by Chebyshev polynomial of degree $l(l{\geq}2)$, i.e., $T_l(cos{\theta})=cos(l{\theta})$. In this paper, we consider $T_l$ as a measure preserving transformation on [-1, 1] with an invariant measure $\frac{1}{\sqrt[\pi]{1-x^2}}dx$. We show that If f(x) is a nonconstant step function with finite k-discontinuity points with k < l-1, then it satisfies the Central Limit Theorem. We also give an explicit method how to check whether it satisfies the Central Limit Theorem or not in the cases of general step functions with finite discontinuity points.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.3
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• pp.29-36
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• 2007

Let T be an ergodic measure preserving transformation on (X, B, ${\mu}$). It is called 2-simple if every 2-fold ergodic joining is either a product measure or an off-diagonal measure. In general, factors of simple maps are not simple. So far, there has been no characterization of the factor of simple maps. In this paper, we give a joining characterization of factors of simple maps.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.4
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• pp.53-68
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• 2008

We study on the practical privacy-preserving techniques by matrix-based randomization approach. We clearly examine the relationship between the two parameters associated with the measure of privacy breach and the condition number of matrix in order to achieve the optimal transition matrix. We propose a simple formula for efficiently calculating the inverse of transition matrix which are needed in the re-construction process of random substitution algorithm, and deduce some useful connections among standard error and another parameters by obtaining condition numbers according to norms of matrix and the expectation and variance of the transformed data. Moreover we give some experimental results about our theoretical expressions by implementing random substitution algorithm.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.262-269
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• 2000

One of the way of the preserving environment is the circulation of materials. Japan's cereal food self-sufficiency rate is less than 30%. Japan imports more than 30 million tons of food every year. Japanese are afraid of international food trade giving damages to environment. Advanced farm mechanization integrated with precision farming is an answer to solve these problems. Crop scientists, soil scientists and agricultural engineers at Kyoto University cooperate together in studying precision agriculture for paddy rice since 1996. Automatic follow-up combine and autonomous vehicle have been developed. Remotely sensing by using machine vision has been studied to measure nitrogen contents. Field map i.e. soil, growth and yield, in paddy field of 0.5 ha has been made. In this report the concept and objectives of advanced farm mechanization and precision agriculture research at Kyoto University are introduced.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.5
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• pp.1187-1199
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• 2015

Recently, as high-quality sensors are being developed, it is available to conveniently measure any kind of data. Healthcare services are being combined with Internet of things (IoTs). And applications that use user's data which are remotely measured, such as heart rate, blood oxygen level, temperature are emerging. The typical example is applications that find ideal spouse by using a user's genetic information, or indicate the presence or absence of a disease. Such information is closely related to the user's privacy, so biometric information must be protected. That is, service provider must provide the service while preserving user's privacy. In this paper, we propose a scheme which enables privacy-preserving outlier detection in Healthcare Service.

• The KIPS Transactions:PartC
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• v.14C no.5
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• pp.439-452
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• 2007

We study on the privacy preserving data mining, PPDM for short, by using randomization. The theoretical PPDM based on the secure multi-party computation techniques is not practical for its computational inefficiency. So we concentrate on a practical PPDM, especially randomization technique. We survey various privacy measures and study on the privacy preserving mining of association rules by using randomization. We propose a new randomization operator, binomial selector, for privacy preserving technique of association rule mining. A binomial selector is a special case of a select-a-size operator by Evfimievski et al.[3]. Moreover we present some simulation results of detecting an appropriate parameter for a binomial selector. The randomization by a so-called cut-and-paste method in [3] is not efficient and has high variances on recovered support values for large item-sets. Our randomization by a binomial selector make up for this defects of cut-and-paste method.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.41-51
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• 2018

Format preserving encryption(FPE) performs encryption with preserving the size and format of plain-text. Therefore, it is possible to minimize the structural change of the database before and after the encryption. For example, when encrypting data such as credit card number or social security number, it is possible to maintain the existing database structure because FPE outputs the same form of cipher-text as plain-text. Currently, the National Institute of Standards and Technology (NIST) recommends FF1 and FF3 as standards for FPE. Recently, in Korea, FEA, which is a very efficient FPE algorithm, has been adopted as the standard of FPE. In this paper, we analyze FEA and measure the performance of FEA by optimizing it in various environments.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.6
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• pp.1401-1414
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• 2018

The k-means clustering algorithm groups input data with the number of groups represented by variable k. In fact, this algorithm is particularly useful in market segmentation and medical research, suggesting its wide applicability. In this paper, we propose a privacy-preserving clustering algorithm that is appropriate for outsourced encrypted data, while exposing no information about the input data itself. Notably, our proposed model facilitates encryption of all data, which is a large advantage over existing privacy-preserving clustering algorithms which rely on multi-party computation over plaintext data stored on several servers. Our approach compares homomorphically encrypted ciphertexts to measure the distance between input data. Finally, we theoretically prove that our scheme guarantees the security of input data during computation, and also evaluate our communication and computation complexity in detail.

• Journal of the Korean Data and Information Science Society
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• v.14 no.1
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• pp.131-141
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• 2003

In this paper, we prove that multi-variate fuzzy polynomials are universal approximators for multi-variate fuzzy functions which are the extension principle of continuous real-valued function under $T_W-based$ fuzzy arithmetic operations for a distance measure that Buckley et al.(1999) used. We also consider a class of fuzzy polynomial regression model. A mixed non-linear programming approach is used to derive the satisfying solution.