• Journal of the Korea Society of Computer and Information
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• v.10 no.1 s.33
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• pp.7-14
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• 2005

An OLAP(On-Line Analytical Processing) system is the decision support tool with which a user can analyze the information interactively in the various aspects. However, the traditional existing construction of an OLAP system has the inefficiency Problem of increasing the processing time and cost caused by the use of complex MDX(Multidimensional Expressions) queries. In an attempt to solve this problem, a new concept of data structuring technique, where a unit column whose elements are all 1 is added to the fact table, was suggested. With the data structuring technique, we can reduce the processing time and cost in OLAP systems.

• Defense and Technology
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• no.9 s.139
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• pp.40-53
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• 1990

세계시장에서 멜버른의 기록은 매우 인상적이다. 이곳 회사들은 국내외 보잉 747 창정비시설과 정비시설등을 공급하였고, 록히드사엔 항공기 격납고를, GE사엔 F404, T700 엔진을, NEC사엔 인공위성 부품을, 프랑스의 에이버스 항공사엔 기체구조물(Floor support structure), MD사엔 MDX헬기의 기체를, 보잉사엔 복합재료를 사용한 Rudder시스템을 공급하였다. 생산품의 3분의 1 이상은 해외수출을 하며, 이외의 많은 생산품과 부품은 미국, 유럽, 아시아지역등에 판매하고 있다.

• The KIPS Transactions:PartC
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• v.19C no.2
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• pp.91-98
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• 2012

OLAP(On-Line Analytical Processing) is a tool to satisfy the requirements of managing overflowing data analysis. OLAP can provide an interactive analytical processing environment to every end-user. Security policy is necessary to secure sensitive data of organization according to users direct access database. But earlier studies only handled the subject in its functional aspects such as MDX(Multidimensional Expressions) and XMLA(XML for Analysis). This research work is purported for solving such problems by designing and implementing an efficient data access control mechanism for the information security on OLAP. Experimental evaluation result is proposed and its efficiency and accuracy are verified through it.

• Kyungpook Mathematical Journal
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• v.28 no.2
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• pp.185-196
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• 1988

We study existence of polynomial integrating factors and solutions F(x, y)=c of first order nonlinear differential equations. We characterize the homogeneous case, and give algorithms for finding existence of and a basis for polynomial solutions of linear difference and differential equations and rational solutions or linear differential equations with polynomial coefficients. We relate singularities to nature of the solution. Solution of differential equations in closed form to some degree might be called more an art than a science: The investigator can try a number of methods and for a number of classes of equations these methods always work. In particular integrating factors are tricky to find. An analogous but simpler situation exists for integrating inclosed form, where for instance there exists a criterion for when an exponential integral can be found in closed form. In this paper we make a beginning in several directions on these problems, for 2 variable ordinary differential equations. The case of exact differentials reduces immediately to quadrature. The next step is perhaps that of a polynomial integrating factor, our main study. Here we are able to provide necessary conditions based on related homogeneous equations which probably suffice to decide existence in most cases. As part of our investigations we provide complete algorithms for existence of and finding a basis for polynomial solutions of linear differential and difference equations with polynomial coefficients, also rational solutions for such differential equations. Our goal would be a method for decidability of whether any differential equation Mdx+Mdy=0 with polynomial M, N has algebraic solutions(or an undecidability proof). We reduce the question of all solutions algebraic to singularities but have not yet found a definite procedure to find their type. We begin with general results on the set of all polynomial solutions and integrating factors. Consider a differential equation Mdx+Ndy where M, N are nonreal polynomials in x, y with no common factor. When does there exist an integrating factor u which is (i) polynomial (ii) rational? In case (i) the solution F(x, y)=c will be a polynomial. We assume all functions here are complex analytic polynomial in some open set.

• Progress in Medical Physics
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• v.5 no.1
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• pp.87-99
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• 1994

Purpose : The determination of electron beam output factor was investigated from individual applicator for various energy of ML-15MDX linear accelerator. The output factor of electron beam was extended from square to rectangular field in individual applicator size through with a least-square fit to a polynomial expression. Materials : In this experiments. the measurement of output was obtained from 2${\times}$cm$^2$ to 20${\times}$20cm$^2$ of field size in different applicator size for 4 to 15 MaV electron beam energy. The output factor was defined as the ratio of maximum dose output on the central axis of the field of individual applicator size to that of a given field size. Applicator factors were derived from comparing with the output dose of reference field size 10${\times}$10cm$^2$. The thickness of block was specially designed as 10mm in thickness of Lipowitz metal for field shaping in all electron energy. Two types of output curves are included as output factors versus side of square fields and that of variable side length for X and Y in one-dimensional to compare the expected values to that of experiments. Results : Expected output factors of rectangular which was derived from that of square fields in individual applicator size from 2${\times}$2cm$^2$ to 20${\times}$20cm$^2$ in different electron energy was very closed to that of experimental measurements within 2% uncertainty. However 1D method showed a 3% discrepancy in small rectangular field for low energy electron beam. Conclusion : Emperical non-linear polynomial regressions of square root and 1D method were performed to determin the output factor in various field size and electron energy. The expected output of electron beam of square root method for square field and 1D method for rectangular field were very closed to that of measurement in all selected electron beam energy.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.33-36
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• 2002

MESFET was fabricated using 4H-SiC substrates and epitaxy The DC characteristics of 0.5 urn gate length, 400 urn gate width MESFET had $I_{dss}$=200 ㎃/mm, maximum transconductance of 12 ㎳/mm at Vrs=-4 V, V, Is=27 V. Thc device had an fT of 2.5 GHz and $f_{mdx}$ of 13.3 GHz at $V_{ds}$ =27 V and $V_{g}$=-4 V. The fabrication and characterization of this device are discussed.d.d.d.

• Communications of the Korean Mathematical Society
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• v.18 no.1
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• pp.65-73
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• 2003

In this paper we seek a positive, radially symmetric and energy minimizing solution of an m-Laplacian equation, -div$($\mid${\nabla}u$\mid$^{m-2}$\mid${\nabla}u)\;=\;h(u)$. In the variational sense, the solutions are the critical points of the associated functional called the energy, $J(v)\;=\;\frac{1}{m}\;\int_{R^N}\;$\mid${\nabla}v$\mid$^m\;-\;\int_{R^N}\;H(v)dx,\;where\;H(v)\;=\;{\int_0}^v\;h(t)dt$. A positive, radially symmetric critical point of J can be obtained by solving the constrained minimization problem; minimize{$\int_{R^N}$\mid${\nabla}u$\mid$^mdx$\mid$\;\int_{R^N}\;H(u)d;=\;1$}. Moreover, the solution minimizes J(v).

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1211-1214
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• 2011

OLAP(On-Line Analytical Processing) 툴은 조직 운영에서 발생하는 데이터의 양이 많아짐에 따라 분석 수요도 함께 급증하며 전문 분석가의 역량만으로는 처리할 수 없는 분석 요구 사항을 충족시키기 위한 툴이다. OLAP 에서는 다양한 사용자가 직접 데이터베이스에 접근하여 대화식으로 질의를 던지고 응답을 받아 분석 업무를 진행할 수 있다. 이렇게 많은 사용자들이 데이터베이스에 직접 접근을 하게 됨에 따라 조직의 민감한 데이터를 지키기 위한 보안 정책이 필수가 되었다. 하지만 기존 연구에서는 OLAP 의 기능적인 분석에 치중하여 MDX(Multidimensional Expressions)와 XMLA(XML for Analysis) 등의 기법으로 기능을 구현하는 것에 그치고 있다. 이에 본 연구에서는 OLAP 보안 관련 연구를 분석하고 보안 모듈을 설계하여 효율적인 정보 보호를 위한 데이터 접근 제어 방법을 제시한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.1120-1123
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• 2008

단방향 암호화 함수인 해쉬 함수는 2005년 Wang의 새로운 공격법이 발표되면서 안전성에 대한 문제점이 조금씩 드러나기 시작하고 있다. Wang의 새로운 차분 공격법은 현재 가장 널리 사용하고 있는 해쉬 알고리즘인 SHA-1을 이론적으로 $2^{69}$의 계산으로 충돌을 찾을 수 있다고 하였다. 본 논문에서는 차분 공격이 이루어지는 방법과 Wang의 차분 공격이 지니는 두 가지 특성에 대해서 연구하였고, MDx계열의 해쉬 함수의 안전성에 대한 기존의 제시된 해결책과 다른, 한 블록의 모든 워드 값을 변형 처리한 방식을 제안한다.

• Progress in Medical Physics
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• v.14 no.2
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• pp.99-107
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• 2003

This study was performed to prepare the verification film for localizing beam-target position with the Photon Knife radiosurgery system (PKRS) using linear accelerator(Mitsubishi, Model ML-15MDX). We developed a laser calibration system using a reticle of transparent lucite to detect Inlet and outlet beams. We verified fixation of the second collimator with film mounted on a holder in the shape of an octagon block 5cm apart from the isocenter. The film was exposed to photon beams of linear accelerator at an interval of 45 degrees during the gantry movement. There were no shifts in the beam of the second collimator during gantry movement. We used a position marker which is designed a head-shaped small lead block and a 10 mm in diameter of steel bead in the plastic tube. The position marker helped to verify the beam directions with patient position in multi-arc and trans-multi-arc of PKRS The verification of beam alignments showed an average 0.8$\pm$0.26 mm discrepancy in LINAC-gram images of PKRS. In our study, the couch movement was $\pm$5 mm laterally, while it shook $\pm$ 2 mm toward the couch axis. The couch, however, was immediately returned to the initial site after shaking. Thus, we postulate that the beam-target position(s) should be verified with LINAC-gram in a stereotactic radiosurgery system to achieve the accuracy of beam-target alignment.