• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.385-389
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• 2000

A phase-retardation function which was derived from Wigner distribution function (WDF) is used to increase a focal depth of a radially symmetric optical system. The WDF for one-dimensional signal is represented as a two-dimensional function of phasespace ($\chi,\zeta$), and a normalized irradiance is described as a form of the Strehl ratio (SR). The increase in the focal depth is accomplished by delivering a shearing tilt a that represents a characteristic of free space propagation with simple manipulation in the WDF space. In this paper we propose a method for evaluating the focal depth quantitatively by representing the phaseretardation function in terms of the focal depth term. In order to verify the validity of the proposed method, we compared the numerically analyzed result with that of J. Sochki's study. study.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.100-102
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• 2005

유비쿼터스는 현재의 제한된 컴퓨팅 환경을 떠나서 시간과 장소에 구애받지 않는 자유로운 컴퓨팅 환경을 제공함으로서 각광받고 있다. 그 중 언제어디서나 정보를 주고받을 수 있으며 가격과 성능 면에서 단연 뛰어난 RFID(Radio Frequency Identification)의 중요성은 점점 증가되고 있는 추세이다. 그러나, 이와 같은 우수성에도 불구하고, 정보 유출의 위험성을 내포하고 있으며, 개인의 위치 추적이나, 비 접근 권한자의 위장행세 등의 사용자 프라이버시 보호에 대한 많은 문제점들을 수반한다. 현재까지 이와 관련된 연구들이 활발히 진행되고 있다. 특히 그 중, Ohkubo의 해시함수를 이용한 프로토콜은 프라이버시 보호 측면에서 위치추적 공격(location tracking), 전방위보안성(forward security)과 같은 문제들에 대한 해결책을 제시하고 있으나, 해시함수를 태그에 직접 구현하는 것은 현재까지는 불가능한 상태이다. 또한, Martin Feldhofer는 대칭키 암호 알고리즘인 AES(Advanced Encryption Standard)를 태그에 구현을 함으로서 암호학적인 강도를 높였으나, 위치추적 공격에 대한 문제정과 물리적 공격에 대한 가정을 하지 않은 단점을 가지고 있다. 본 논문에서는 기존연구에서의 문제점들을 보완하고자 현실적으로 구현 가능한 AES를 사용하고, 위치추적 공격, 비권한자 접근(unauthorized access) 공격과 물리적 공격으로부터 안전하며 전방위보안성을 제공하는 기법을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.12 no.1 s.45
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• pp.17-24
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• 2007

Critical practicality problems are cause to search the presentation and contents according to user request and purpose in previous internet system. Recently, there are a lot of researches about dynamic adaptable ontology based system. We designed ontology based educational system which uses discrete probability and user profile. This system provided advanced usability of contents by ontology and dynamic adaptive model based on discrete probability distribution function and user profile in ontology educational systems. This models represents application domain to weighted direction graph of dynamic adaptive objects and modeling user actions using dynamically approach method structured on discrete probability function. Proposed probability analysis can use that presenting potential attribute to user actions that are tracing search actions of user in ontology structure. This approach methods can allocate dynamically appropriate profiles to user.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.129-140
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• 2007

The planning procedure of a transit operation consists of design, operation, and evaluation according to the research characteristics. There are some review studies on the operation and evaluation procedure, but the research on the design procedure has not yet been organized systematically. In this study, the research on transit system design was reviewed and the model structure and its solution method were arranged. The decision variables of the design procedure are network structure, line spacing or position, stop spacing, dispatching headway, and fleet size. In the analytical research on design procedure, system total cost is generally used as the objective function. System total cost is comprised of user cost, which is the sum of user access, waiting, and travel cost, and operating cost. Total cost of the transit system, used as the objective function, has the unique minimum because it is differentiable. There is a certain decision variable that makes the derivative of the objective function equal to zero and the second derivative of the objective function is positive. Therefore the decision variable that makes the first derivative of the objective function zero is the optimum that minimizes the objective function, and each of the cost components of the objective function become the same. This study is expected to help understanding about the research on the design procedure of transit operation planning and to help be a catalyst for relevant research.

• The Journal of the Korea Contents Association
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• v.7 no.7
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• pp.60-67
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• 2007

The spectrum sensing is important for decision of using frequency band. It checks the frequency band for cognitive radio system. In this paper, we apply autocorrelation function to the energy detection method. We use the autocorrelation function to improve the performance of spectrum sensing method based on the energy detection method. This method is different from cyclostationary process method where parameters such as the mean or the autocorrelation function are time-varying periodically. And we propose improved method that is robust in poor radio environment. If the proposed method applies for sensing in the cognitive radio system, it will have the structural simplicity and the fast computation of spectrum sensing.

• Communications for Statistical Applications and Methods
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• v.15 no.1
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• pp.125-136
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• 2008

In many practical engineering design problems, the form of objective functions is not given explicitly in terms of design variables. Given the value of design variables, under this circumstance, the value of objective functions is obtained by real/computational experiments such as structural analysis, fluid mechanic analysis, thermodynamic analysis, and so on. These experiments are, in general, considerably expensive. In order to make the number of these experiments as few as possible, optimization is performed in parallel with predicting the form of objective functions. Response Surface Methods (RSM) are well known along this approach. This paper suggests to apply Support Vector Machines (SVM) for predicting the objective functions. One of most important tasks in this approach is to allocate sample data moderately in order to make the number of experiments as small as possible. It will be shown that the information of support vector can be used effectively to this aim. The effectiveness of our suggested method will be shown through numerical example which is well known in design of engineering.

• Journal of Korea Game Society
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• v.19 no.6
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• pp.99-106
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• 2019

This paper addresses a method to compute the closest approach distance between two ellipsoids in their inter-center direction. This is the key technique for collision detection and response between ellipsoids. We formulate a set of conditions with the inter-center distance, the contact point and the contact normal vector of the two externally-contacting ellipsoids. The equations are solved robustly and efficiently using a hybrid of Newton's method and the bisection method with root bracketing. We demonstrate the robustness and efficiency of the proposed method in various experiments.

• Proceedings of The KACE
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• 2017.08a
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• pp.131-134
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• 2017

이 연구에서 엔트리 명령 블록을 이용하여 보편적 프로그래밍 언어를 개발하고 검증하였다. 그래서 이 연구를 통해 블록형 프로그래밍 언어의 접근 수월성을 이용하여 절차적 사고력 향상을 위한 아이디어를 제공하고자 하였다. 새로운 프로그래밍 언어를 만들어 알고리즘을 적용하여 함수화된 사칙연산 프로그램을 만들면서, 다양한 알고리즘을 적용하면 엔트리에서 제시하는 모든 명령 블록을 만들 수 있음을 증명하였다. 이 연구를 통해 1)프로그래밍 언어에 포함된 다양한 기능의 명령어들도 함수화되어 있음을 증명하고 재생산 가능함을 경험할 수 있는 아이디어를 제공하고, 2)초보 프로그래머들이 프로그래밍 언어 개발에 대한 흥미와 관심을 갖게 되는 방안을 제시하며, 3)알고리즘을 경험하면서 절차적 사고력을 향상시킬 수 있는 다른 방향의 SW 교수 학습 방법과, 4)프로그래밍 언어를 미시적으로 탐구하면서 SW 교육 관점을 다양화하는 방법을 제시하였다. 이 연구에서 제시한 방안으로 학생들이 절차적 사고력 향상과 프로그래밍 언어의 다양성 인식, 프로그램을 심층적으로 분석하는 태도 등의 SW 교육에 대한 긍정적 변화를 기대한다.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.91-98
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• 2009

In this paper, this model ensures confidentiality and integrity of mandatory access cotrol policy which based on fuzzy function with importance of information. And it solves authorization abuse problem through role graph creation algorithm and flowing policy that security grade is applied. Because this model composes role hierarchy which bind similar role concept to apply to commercial environment, it has expansile advantage by large scale security system as well as is easy that add new role.

• Environmental and Resource Economics Review
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• v.20 no.1
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• pp.119-153
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• 2011

This study reviews various aspects of model formulating processes of dichotomous choice responses of the contingent valuation method (CVM), which has been increasingly used in the preliminary feasibility test of Korea public investment projects. The theoretical review emphasizes the consistency between WTP estimation process and WTP measurement process. The empirical analysis suggests that two common parametric models for dichotmous choice responses (RUM and RWTP) and two commonly used probability distributions of random components (probit and logit) resulted in all most the same empirical WTP distributions, as long as the WTP functions are specified to be a linear function of the bid amounts. However, the efficiency gain of DB response compared to SB response were supported on the ground that the two CV responses are derived from the same WTP distribution. Moreover for the exponential WTP function which guarantees the non-negative WTP measures, sample mean WTP were quite different from median WTP if the scale parameter of WTP function turned out to be large.