• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2768-2780
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• 2019

Ciphertext-policy attribute-based encryption (CP-ABE) is one of the practical technologies to share data over cloud since it can protect data confidentiality and support fine-grained access control on the encrypted data. However, most of the previous schemes only focus on data confidentiality without considering data receiver privacy preserving. Recently, Li et al.(in TIIS, 10(7), 2016.7) proposed a CP-ABE with hidden access policy and testing, where they declare their scheme achieves privacy preserving for the encryptor and decryptor, and also has high decryption efficiency. Unfortunately, in this paper, we show that their scheme fails to achieve hidden access policy at first. It means that any adversary can obtain access policy information by a simple decisional Diffie-Hellman test (DDH-test) attack. Then we give a method to overcome this shortcoming. Security and performance analyses show that the proposed scheme not only achieves the privacy protection for users, but also has higher efficiency than the original one.

• Journal of Information Processing Systems
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• v.3 no.1
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• pp.21-25
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• 2007

We propose several practical SMC protocols for privacy-preserving cooperative scientific computations. We consider two important scientific computations which involve linear equations: the linear systems of equations problem and the linear least-square problem. The protocols proposed in this paper achieve acceptable security in the sense of Du-Zhan's paradigm and t-wise collusion-resistance, and their communication complexity is O(tm), where t is a security parameter and m is the total number of participants. The complexity of our protocol is significantly better than the previous result O($m^2/{\mu}$) of [4], in which the oblivious transfer protocol is used as an important building block.

• The Mathematical Education
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• v.47 no.3
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• pp.239-259
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• 2008

This paper is to find and to suggest alternative ways of description on function chapters in the middle school mathematics so that the descriptions be more closely related to daily life. The research has two phases: one for belief on the usefulness, the other for cognitive ability to solve the practical problems. Results are as following. 1. Most descriptions of corresponding chapters have emphases on the usefulness of functions so as to enhance beliefs on the use of functions. 2. Most practical functions contain expressions of large constant term and large coefficients in magnitude while those are not in the descriptions of tektbooks, especially in case of using ruled papers. 3. For quadratic functions, most students do not detect the degree of the function from the data presented by pairs of values of x and y. And those are not dealt with in most of textbooks, which are given in the MIC textbook.

• Communications for Statistical Applications and Methods
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• v.25 no.4
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• pp.355-371
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• 2018

The two parameter negative exponential distribution has many practical applications in queuing theory such as the service times of agents in system, the time it takes before your next telephone call, the time until a radioactive practical decays, the distance between mutations on a DNA strand, and the extreme values of annual snowfall or rainfall; consequently, has many applications in reliability systems. This paper considers an estimation problem of stress-strength model with two parameter negative parameter exponential distribution. We introduce a maximum penalized likelihood method, Bayes estimator using Lindley approximation to estimate stress-strength model and compare the proposed estimators with regular maximum likelihood estimator for complete data. We also introduce a maximum penalized likelihood method, Bayes estimator using a Markov chain Mote Carlo technique for incomplete data. A Monte Carlo simulation study is performed to compare stress-strength model estimates. Real data is used as a practical application of the proposed model.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.2
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• pp.77-105
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• 2014

Medical imaging techniques have evolved to expand our ability to visualize new contrast information of electrical, optical, and mechanical properties of tissues in the human body using noninvasive measurement methods. In particular, electrical tissue property imaging techniques have received considerable attention for the last few decades since electrical properties of biological tissues and organs change with their physiological functions and pathological states. We can express the electrical tissue properties as the frequency-dependent admittivity, which can be measured in a macroscopic scale by assessing the relation between the time-harmonic electric field and current density. The main issue is to reconstruct spectroscopic admittivity images from 10 Hz to 1 MHz, for example, with reasonably high spatial and temporal resolutions. It requires a solution of a nonlinear inverse problem involving Maxwell's equations. To solve the inverse problem with practical significance, we need deep knowledge on its mathematical formulation of underlying physical phenomena, implementation of image reconstruction algorithms, and practical limitations associated with the measurement sensitivity, specificity, noise, and data acquisition time. This paper discusses a number of issues in electrical tissue property imaging modalities and their future directions.

• Journal for History of Mathematics
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• v.22 no.2
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• pp.81-98
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• 2009

Probability plays a very important role in modern society as an essential tool for solving various kinds of problems from our real life or scientific province. However, most of precedent studies on probability pointed out that many students had difficulties in understanding the nature of it, and that probability teaching method in the classroom is easily led only to calculation system, which is isolated from practical applications. In this paper, I make a close study further onto these themes, by analyzing the 8th grade textbooks through these following questions; how do the textbooks deal with calculation of probability that certain two events occur at the same time? On the practical basis, how do they make use of probability as a problem-solving instrument in both actual life and scientific fields? After these, I try to extract some features and issues of probability teaching method in current Korean textbooks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.2
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• pp.13-24
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• 2006

We consider a privacy-preserving cooperative computation protocol evaluating a beneficial function of all participants' secret inputs, such that each party finally holds a share of the function output. We propose a practical privacy-preserving cooperative computation protocol for solving the linear system of equations problem md the linear least-squares problem. Solutions to these problems are widely used in many areas such as banking, manufacturing, and telecommunications. Our multi-party protocol is an efficiently extended version of the previous two-party model.

• Journal of the Korean School Mathematics Society
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• v.23 no.1
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• pp.159-177
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• 2020

Education researchers have been continuously interested in the teacher's ability to design lessons and conducted various studies in order to improve the teacher's professionalism in determining the quality of school instruction. So, this study explored the change of instructional design through the lesson reflection of pre-service mathematics teachers who participated in practicum settings. As a result, in the lesson plan prepared by pre-service mathematics teachers, the motivation to induce learning in the introduction stage, to present the learning contents in the development stage, and to reconstruct the formative evaluation of the closing stage was the highest rate. And the categories of the reconstructed contents appeared intensively in terms of curriculum contents and teaching and learning methods. This result can be attributed to the lack of experience in designing and performing lessons by pre-service mathematics teachers, so it suggests that the opportunity to design and conduct classes that take into account the practical aspects of education should be provided in the preparation process for pre-service mathematics teachers.

• School Mathematics
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• v.11 no.3
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• pp.527-546
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• 2009

This study was designed to gain insights into instrumental genesis process of CAS in Korean high school students and to explore its practical potentials in secondary mathematics education. Two activities, such as Concept-Centered Mathematics Activity based on CAS and Problem Solving Activities, were constructed and executed to 10th Grade seven students for twelve class hours. The finding on the students' activities are as follows : it is meaningful in mathematics education, especially in algebra education, in that the CAS based concept centered mathematics activity offers great opportunities to deal with high-qualified application problems. The problem solving activities based on the instrumented CAS may have an influence on the sequence of mathematics curriculum, e.g. the optimization problems may precede the calculus problems such as derivatives in high school. The results of this study to investigate the instrumental genesis of CAS in mathematical activities will give insights into the secondary mathematics curriculum to prepare the CAS in Korea.

• School Mathematics
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• v.18 no.4
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• pp.857-880
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• 2016

The development of teacher's professionalism through teacher education is a key element in the improvement of school education. However, there has been criticism that the mathematics teacher education in Korea do not provide given enough opportunities for the classroom experience during preservice teacher education period. For development of inservice mathematics teachers and preservice teachers' teaching professionalism, this study develops a research community for mathematics classroom consisting of experts, inservice mathematics teachers, and preservice teachers. And the study explores the possibilities of the model as an educational space for inservice teachers and preservice teachers by participating in a series of courses such as task development and revision, and observation and analysis of classes. As results, inservice teachers and preservice teachers were able to enhance the practical experience and understanding necessary for the class, and they were also positively influenced in teacher efficacy and view of teaching on the model. Based on this, we suggest the possibility of the model as a teacher education system.