• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4529-4548
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• 2016

DDoS attacks have had a devastating effect on the Internet, which can cause millions of dollars of damage within hours or even minutes. In this paper we propose a practical dynamic defense approach that overcomes the shortage of static defense mechanisms. Our approach employs a group of SDN-based proxy switches to relay data flow between users and servers. By substituting backup proxy switches for attacked ones and reassigning suspect users onto the new proxy switches, innocent users are isolated and saved from malicious attackers through a sequence of remapping process. In order to improve the speed of attacker segregation, we have designed and implemented an efficient greedy algorithm which has been demonstrated to have little influence on legitimate traffic. Simulations, which were then performed with the open source controller Ryu, show that our approach is effective in alleviating DDoS attacks and quarantining the attackers by numerable remapping process. The simulations also demonstrate that our dynamic defense imposes little effect on legitimate users, and the overhead introduced by remapping procedure is acceptable.

• Communications of the Korean Mathematical Society
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• v.13 no.3
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• pp.629-634
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• 1998

As most of distributions appearing in applications are finite but with the unknown domain of finiteness, we propose to use the robust minimax approach for the determination of the boundaries of this domain. The obtained least favorable distribution minimizing Fisher information over the class of the approximately Gaussian finite distributions gives the reasonable sizes of the domain of finiteness and the thresholds of truncation.

• Research in Mathematical Education
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• v.6 no.1
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• pp.81-96
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• 2002

This article describes a research project that examined the impact of hand-held technology on students' understanding linear equations and graphs in multiple representations. The results indicated that students in the graphing-approach classes were significantly better at the components of interpreting. No significant differences between the graphing-approach and traditional classes were found fur translation, modeling, and algebraic skills. Further, students in the graphing-approach classes showed significant improvements in their attitudes toward mathematics and technology, were less anxious about mathematics, and rated their class as more interesting and valuable.

• East Asian mathematical journal
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• v.36 no.1
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• pp.55-60
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• 2020

We study a probabilistic approach for valuing an exchange option with default risk. The structural model of Klein [6] is used for modeling default risk. Under the structural model, we derive the closed-form pricing formula of the exchange option with default risk. Specifically, we provide the pricing formula of the option with the bivariate normal cumulative function via a change of measure technique and a multidimensional Girsanov's theorem.

• Research in Mathematical Education
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• v.7 no.1
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• pp.1-10
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• 2003

This research reviewed literatures on proof in mathematics education. Several views of proof can be classified (and identified) such as psychological approach (Platonism, empiricism), structural approach (logicism, formalism, intuitionism) and social approach (ontology, axiomatic systems). All these views of proof are valuable in mathematics education society. The concept of proof can be found in the form of analytic knowledge not of constructive knowledge. Human beings developed their knowledge in the sequence of constructive knowledge to analytic knowledge. Therefore, in mathematics education, the curriculum of mathematics should involve the process of cognitive knowledge development.

• Korean Journal of Childcare and Education
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• v.19 no.4
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• pp.29-52
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• 2023

Objective: This research aims to examine the effect of a young children's engineering-focused STEAM program based on the project approach - a program that constructs components aligned with children's interests in their play through an engineering design process - on their scientific inquiry ability, mathematical problem-solving ability, and creativity. Methods: In this research, 42 five-year-old children from a public kindergarten in S district, I city, were randomly divided into experimental and comparative groups, each with 21 children. The engineering-focused STEAM program was conducted from April 18 to June 10, 2022, with the experimental group exploring the 'car' theme and the comparison group focusing on a different theme. The study employed an independent sample t-test and analysis of covariance(ANCOVA), using the pretest as a covariate to control variables. Results: The children-selected 'cars' themed engineering-focused STEAM program was effective in enhancing their scientific inquiry ability, mathematical problem-solving ability and creativity. Conclusion/Implications: The engineering-focused STEAM program, which emerges from young children's interesting daily play, had positive effects on enhancing their scientific inquiry ability, mathematical problem-solving ability, and creativity. This research can serve as fundamental data for developing education programs focused on engineering within the STEAM framework, guided by children's emergent play.

• Bulletin of the Korean Mathematical Society
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• v.51 no.1
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• pp.43-54
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• 2014

This paper is concerned with nonlinear evolution differential equations with infinite delay in Banach spaces. Using Kato's approximating approach, existence and uniqueness of strong solutions are obtained.

• East Asian mathematical journal
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• v.16 no.2
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• pp.251-266
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• 2000

The problem of solution uniqueness to the task of determining unknown parameters of mathematical models from input-output observations is studied. This problem is known as structural identifiability problem. We offer a new approach for testing structural identifiability of linear state space models. The approach compares favorably with numerous methods proposed by other authors for two main reasons. First, it is formulated in obvious mathematical form. Secondly, the method does not involve unfeasible symbolic computations and thus allows to test identifiability of large-scale models. In case of non-identifiability, when there is a set of solutions to the task, we offer a method of computing functions of the unknown parameters which can be determined uniquely from input-output observations and later used as new parameters of the model. Such functions are called parametric functions capable of estimation. To develop the method of computation of these functions we use Lie group transformation theory. Illustrative example is given to demonstrate applicability of presented methods.

• Research in Mathematical Education
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• v.10 no.3 s.27
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• pp.151-167
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• 2006

The open approach to teaching school mathematics in the United States is an outcome of the collaboration of Japanese and U. S. researchers. We examine the approach by illustrating its three aspects: 1) Open process (there is more than one way to arrive at the solution to a problem; 2) Open-ended problems (a problem can have several of many correct answers), and 3) What the Japanese call 'from problem to problem' or problem formulation (students draw on their own thinking to formulate new problems). Using our understanding of the Japanese open approach to teaching mathematics, we adapt selected methods to teach mathematics more effectively in the United States. Much of this approach is new to U. S. mathematics teachers, in that it has teachers working together in groups on lesson plans, and through a series of discussions and revisions, results in a greatly improved, effective plan. It also has teachers actively observing individual students or groups of students as they work on a problem, and then later comparing and discussing the students' work.

• Bulletin of the Korean Mathematical Society
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• v.14 no.1
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• pp.1-8
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• 1977