• Title/Summary/Keyword: 근사작도

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Derivation of Coherent Reflection Coefficient at Mid and Low Frequency for a Rough Surface (불규칙 경계면에 대한 중저주파수 간섭 반사 계수 유도)

  • Chu, Young-Min;Seong, Woo-Jae;Byun, Sung-Hoon;Kim, Sea-Moon
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.3
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    • pp.174-186
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    • 2009
  • When we apply a propagation model to the ocean with boundaries, we can calculate reflected wave using reflection coefficient suggested by Rayleigh assuming the boundaries are flat. But boundaries in ocean such as sea surface and sea bottom have an irregular rough surface. To calculate the reflection loss for an irregular boundary, it is needed to compute the coherent reflection coefficient based on an experimental formula or scattering theory. In this article, we derive the coherent reflection coefficients for a fluid-fluid interface using perturbation theory, Kirchhoff approximation and small-slope approximation respectively. Based on each formula, we can calculate coherent reflection coefficients for a rough sea surface or sea bottom, and then compare them to the Rayleigh reflection coefficient to analyze the reflection loss for a random rough surface. In general, the coherent reflection coefficient based on small-slope approximation has a wide valid region. Comparing it with the coherent reflection coefficients derived from the Kirchhoff approximation and perturbation theory, we discuss a valid region of them.

Throughput Approximation Method for Assembly/Disassembly Production Systems with Finite Buffer (유한용량을 갖는 조립/분해 생산시스템의 산출율 근사적 방법)

  • 백천현;김호균;조형수
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2000.04a
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    • pp.257-260
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    • 2000
  • 본 연구에서는 유한용량을 갖는 조립/분해 생산시스템의 산출율분석을 위한 근사적 방법을 제시한다. 유한용량을 갖는 조립/분해 생산시스템은 상태공간이 매우 크기 때문에 효율적으로 분석하기가 어렵다. 따라서 근사적 방법에서는 조립/분해 생산시스템을 비교적 작은 규모의 상태공간을 갖도록 단순 조런/분해 시스템과 단일 직렬시스템을 갖는 각각의 부분시스템으로 분해한다. 각 부분시스템은 2차 모멘트가 고려된 PH/Ph/1/C 시스템으로 기술되고 수리적 방법에 의해 분석되어진다. 실험결과는 시뮬레이션과 비교되고, 제시된 근사적 방법이 효과적이라는 것을 보여준다.

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도서 지하매질내 해수침입 예측 : Ghyben-Herzberg 근사식의 한계

  • 박주완;최희주;이명찬
    • Proceedings of the Korean Nuclear Society Conference
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    • 1996.05c
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    • pp.589-594
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    • 1996
  • 도서지역에서의 해수침입에 의한 해수-담수 경계면의 예측은 담수의 이용측면에서 뿐만 아니라 방사성폐기물 영구처분장과 같은 시설을 지하동굴을 이용하여 건설할 경우 설계개념의 설정 및 처분시설의 성능평가 측면에서도 중요한 사항이다. 해수침입의 예측에 널리 사용되어 온 Ghyben-Herzberg 근사식을 자연수위면의 경사가 급한 도서 지하매짙에 적용할 경우 야기되는 문제점을 지적하고, 보다 신뢰성이 향상된 방법인 염분 이동식에 근거한 수치해를 이용하여 해수-담수 경계면을 예측하였다. 경사도가 다른 두 가지 가상 처분시스템에 대한 정상상태에서의 해수침입 해석 결과, Ghyben-Herzberg 근사식은 담수지역에서의 수직 수두구배가 작은 경우에만 적용되며 국내에서 방사성폐기물 처분부지로 고려하였던 굴업도와 같은 작은 도서의 지하매질에서의 해수-담수 경계면 예측시 오류를 범할 수 있으므로 단순 적용은 피해야 할 것으로 판단되었다.

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Harmonic Wavelet Method for Minimizing Relative Error (상대 오차의 최소화를 위한 조화 웨이블릿 기법)

  • Ham, Sung-Ho;Kang, Seong-Goo;Lee, Suk-Ho
    • Proceedings of the Korean Information Science Society Conference
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    • 2005.07b
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    • pp.91-93
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    • 2005
  • 대용량 데이타에 대한 복잡한 질의 처리가 요구되는 응용에서 빠른 시간 안에 응답을 돌려주기 위해, 데이타를 작은 크기로 근사하여 질의를 처리하는 방법이 연구되고 있다. 빠른 응답을 위해 주어진 저장 공간의 제약 하에서 얼마나 원본 데이타와 유사하게 근사할 수 있는지가 데이타 근사의 성능을 결정한다. 본 논문에서는 데이타 근사에서 유사도의 척도 중 하나인 최대 상대 오차를 줄이기 위하여 Haar 웨이블릿을 변형한 조화 웨이블릿 기법을 제안한다. 조화 웨이블릿은 데이타 변환 과정 중 조화평균을 이용하여 상대 오차 정보를 손쉽게 얻어낼 수 있어 근사 데이타의 상대 오차를 최소화하는 데 적합한 기법이다.

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A Study on Constructions of the Polygons by Albrecht Dürer for Mathematics Education (알브레히트 뒤러의 정다각형 작도법 고찰)

  • Cho, Youngmi
    • Journal of Educational Research in Mathematics
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    • v.27 no.3
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    • pp.581-598
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    • 2017
  • The early Renaissance artist Albrecht $D{\ddot{u}}rer$ is an amateur mathematician. He published a book on geometry. In the second part of that book, $D{\ddot{u}}rer$ gave compass and straight edge constructions for the regular polygons from the triangle to the 16-gon. For mathematics education, I extracted base constructions of polygon constructions. And I also showed how to use $D{\ddot{u}}rer^{\prime}s$ idea in constructing divergent forms with compass and ruler. The contents of this paper can be expected to be the baseline data for mathematics education.

Variance Mismatched Quantization of a Generalized Gamma Source (일반화된 감마 신호원의 분산 불일치된 양치화)

  • 구기일
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.10A
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    • pp.1566-1575
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    • 2000
  • This paper studies mismatched scalar quantization of a generalized gamma source by a quantizer that is optimally (in the mean square error sense) designed for another generalized gamma source. Specifically, it considers variance-mismatched quantization which occurs when the variance of the source to be quantized differs from tat of the designed-for source. The main result is the two distortion formulas derived from Bennett's integral. The first formula is an approximation expression that uses the outermost threshold of an optimum scalar quantizer, and the second formula, in turn, uses an approximation formula for this outermost threshold. Numerical results are obtained for Laplacian sources, which are example of a generalized gamma source, and comparisons are made between actual mismatched distortions and the two formulas. These numerical results show that the two formulas become more accurate, as the number of quantization points gets larger and the ratio of the source variance to that of the designed-for source gets bigger. For example, the formulas are within 2~4% of the actual distortion for approximately 64 quantization points or more. In conclusion, the proposed approximation formulas are considered to have contribution as closed formulas and for their accuracy.

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Precise Max-Pooling on Fully Homomorphic Encryption (완전 동형 암호에서의 정밀한 맥스 풀링 연산)

  • Eunsang Lee
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.33 no.3
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    • pp.375-381
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    • 2023
  • Fully homomorphic encryption enables algebraic operations on encrypted data, and recently, methods for approximating non-algebraic operations such as the maximum function have been studied. However, precise approximation of max-pooling operations for four or more numbers have not been researched yet. In this study, we propose a precise max-pooling approximation method using the composition of approximate polynomials of the maximum function and theoretically analyze its precision. Experimental results show that the proposed approximate max-pooling has a small amortized runtime of less than 1ms and high precision that matches the theoretical analysis.

3-D Crosshole EM Modeling by the Extended Born Approximations (확장된 Born근사법에 의한 시추공간 3차원 전자탐사 모델링)

  • Cho, In-Ky;Choi, Kyoung-Hwa
    • Geophysics and Geophysical Exploration
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    • v.2 no.3
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    • pp.142-148
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    • 1999
  • Three-dimensional electromagnetic modeling algorithm in homogeneous half-space was developed using the extended Born approximation to an electric field integral equation. To examine the performance of the extended Born approximation algorithm, the results were compared with those of the full integral equation results. For a crosshole source-receiver configuration, the agreement between the integral equation and the extended Born approximation was remarkable when the source frequency is lower than 20 kHz and conductivity contrast lower than 1:10. Beyond this conductivity contrast, the simulated results by the extended Born approximation exhibit a difference with respect to those by the integral equation. Therefore, the limit of accuracy lies below contrast of 1:10 in the extended Born approximation. Since for the source frequency range from 20 kHz to 100 kHz, however, the difference is relatively small, the extended Born approximation could be used for a reasonable 3-D EM modeling algorithm.

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Study on the characteristic Impedance of Biconical antenna Consisting of 4m conical wires (다소선 Biconical antenna 특성 임피던스)

  • 박정기;이두수
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.11 no.2
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    • pp.27-32
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    • 1974
  • The characteristic impedance of a biconical antenna which is the conical cage consisting of 4m conical wires is obtained analytically under some assumption. The effect of the number of the elements on the characteristic impedance is observed according to the equation of the characteristic impedance derived in this paper. The equation is not convenient for practical use. However, a compact form of the equation is obtained by assuming that the apexangle is not very large. The numerical solution of this approximate equation is found to show errors no more than 2% over a wide range of the apex angle .

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Sensitivity Analyses on Breakdown Voltage of Cylindrical PN Junctions to the Doping Concentrations (원통형 PN접합의 항복전압의 농도에 대한 민감도)

  • Seo, Hyun-Seok;Jo, Jung-Yol;Ahn, Hee-Tae;Choi, Yearn-Ik
    • Proceedings of the KIEE Conference
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    • 2006.10a
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    • pp.59-60
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    • 2006
  • 원통형 PN접합의 Baliga의 해석적인 항복전압에 대한 근사식을 유도하였다. 근사식은 접합길이, $r_j$와 공핍층 깊이, $W_{pp}$의 비 ($r_i/W_{pp}$)가 0.1보다 작은 경우 Baliga식과 잘 일치하였다. 농도에 대한 원통형 접합의 항복전압의 민감도를 유도하였으며, 근사식을 사용한 경우가 Baliga식의 경우보다 민감도식이 더 간단하기 때문에, 민감도를 고려한 소자 설계 시 활용될 수 있으리라 기대된다. 민감도 식을 이용하여 설계한 결과 항복전압의 편차가 10% 이내로 제어하기 위해서는 도핑농도가 $10^{15}cm^{-3}$이고 접합깊이가 $5{\mu}m$ 인 원통형 접합인 경우 농도 편차가 12.8%이내 이어야한다.

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