• Title/Summary/Keyword: analysis and computation

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FLOW ANALYSIS AROUND THE ROTOR BLADE WITH TILT ANGLES (틸팅각에 따른 로터 블레이드 주위의 유동장 해석)

  • Yoo, Y.H.;Choi, J.W.;Kim, S.C.;Kim, J.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.166-170
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    • 2008
  • The changing process from hovering mode to transition one is of importance to determine a stability of tilt-rotor aircraft, which is utilized in UAV(Unmaned Aerial Vehicle). The analysis on fluid flows and aerodynamic characteristics according to variation of tilting angle of rotor is essential step in development of tilt-rotor. In the present study, the computation domain is divided into the rotating and stationary regions in order to consider the rotating blades. For the convenient realization of various tilting angle as well as application of boundary condition, the whole computation region is constructed into sphere domain. The near farfield boundary condition is adopted. The airfoil used in computation is NACA 0012. The computation results for the hovering mode are validated by comparing with previously conducted experimental results. From the results, the flow fields around rotor blade and the aerodynamic characteristics in transition mode are observed. The computational result will provide the basis for development and performance evaluation of tilt-type aircraft.

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New Higher-Order Differential Computation Analysis on Masked White-Box AES (마스킹 화이트 박스 AES에 대한 새로운 고차 차분 계산 분석 기법)

  • Lee, Yechan;Jin, Sunghyun;Kim, Hanbit;Kim, HeeSeok;Hong, Seokhie
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.30 no.1
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    • pp.1-15
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    • 2020
  • As differential computation analysis attack(DCA) which is context of side-channel analysis on white-box cryptography is proposed, masking white-box cryptography based on table encoding has been proposed by Lee et al. to counter DCA. Existing higher-order DCA for the masked white box cryptography did not consider the masking implementation structure based on table encoding, so it is impossible to apply this attack on the countermeasure suggested by Lee et al. In this paper, we propose a new higher-order DCA method that can be applied to the implementation of masking based on table encoding, and prove its effectiveness by finding secret key information of masking white-box cryptography suggested by Lee et al. in practice.

THE STUDY OF AERO-ACOUSTICS CHARACTERISTICS BY THE BOUNDARY CONDITIONS OF HIGH ORDER SCHEME (고해상도 수치기법의 경계조건에 따른 공력음향 특성에 관한 연구)

  • Lee, S.S.;Kim, J.S.
    • Journal of computational fluids engineering
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    • v.14 no.3
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    • pp.25-32
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    • 2009
  • The present paper focuses on the analysis of aero-acoustics characteristic by appling different four boundary conditions. The high-order and high-resolution numerical schemes are used for discrete accurate computation of compressible flow. The four boundary conditions include extrapolation, characteristic boundary condition, zonal characteristic boundary condition. These boundary conditions are applied to the computation of two dimensional circular cylinder flows with Mach number of 0.3 and Reynolds number of 400. The computation results are validated against measurement data and other computation results for the Strouhal frequency of vortex shedding, the mean drag coefficient and root-mean-square lift for the unsteady periodic flow regime. The characteristics of secondary frequency is predicted by three kinds of boundary conditions.

Development of 2-Dimensional Static-explicit Rigid-plastic Finite Element Method and Investigation of the Effect of Punch Stroke (2차원 정적-외연적 강소성 유한요소법의 개발 및 펀치 행정구간에 따른 영향분석)

  • Jung, Dong-Won;Lee, Seung-Hun
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.3 no.3
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    • pp.39-45
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    • 2004
  • In rigid-plastic finite element method, there is a heavy computation time and convergence problem. In this study, static-explicit rigid-plastic finite element method will be introduced. This method is the way that restrict the convergence interval. In result, convergence problem and computation time due to large non-linearity in the existing numerical analysis method were no longer a critical problem. It is expected that various results from the numerical analysis will give very useful information for the design of tools in sheet metal forming process.

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Reduction of Dimension of HMM parameters in MLLR Framework for Speaker Adaptation (화자적응시스템을 위한 MLLR 알고리즘 연산량 감소)

  • Kim Ji Un;Jeong Jae Ho
    • Proceedings of the KSPS conference
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    • 2003.05a
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    • pp.123-126
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    • 2003
  • We discuss how to reduce the number of inverse matrix and its dimensions requested in MLLR framework for speaker adaptation. To find a smaller set of variables with less redundancy, we employ PCA(principal component analysis) and ICA(independent component analysis) that would give as good a representation as possible. The amount of additional computation when PCA or ICA is applied is as small as it can be disregarded. The dimension of HMM parameters is reduced to about 1/3 ~ 2/7 dimensions of SI(speaker independent) model parameter with which speech recognition system represents word recognition rate as much as ordinary MLLR framework. If dimension of SI model parameter is n, the amount of computation of inverse matrix in MLLR is proportioned to O($n^4$). So, compared with ordinary MLLR, the amount of total computation requested in speaker adaptation is reduced to about 1/80~1/150.

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Automatic Generation of Effective Length Factor of Elastic and Inelastic Column in the Finite Element Analysis (유한요소해석에서 탄성 및 비탄성 기둥에 대한 유효길이 계수의 자동산정)

  • 이성우;이선구;이형우
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1993.10a
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    • pp.24-31
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    • 1993
  • In the design of column, computation of effective length factor for calculation of allowable compressive stress is inevitable. In this study. computer code which automatically generates effective length factor in the finite element analysis is developed. The program is developed to be used for orthogonal and nonorthogonal frame structure. Some i1lustrative examples verify that the computation results we correct for various cases.

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Finite element analysis of welding process by parallel computation (병렬 처리를 이용한 용접 공정 유한 요소 해석)

  • 임세영;김주완;최강혁;임재혁
    • Proceedings of the KWS Conference
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    • 2003.11a
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    • pp.156-158
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    • 2003
  • An implicit finite element implementation for Leblond's transformation plasticity constitutive equations, which are widely used in welded steel structure is proposed in the framework of parallel computing. The implementation is based upon the multiplicative decomposition of deformation gradient and hyper elastic formulation. We examine the efficiency of parallel computation for the finite element analysis of a welded structure using domain-wise multi-frontal solver.

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효율적인 회전기계 불균형 응답 계산 방법

  • 박종혁;홍성욱
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.04a
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    • pp.615-619
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    • 1995
  • The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in ortor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an exact condensation procedure is introduced to easily take into account bearing parameters in computation of unbalance responses for rotor bearing systems. The present method is illustrated through a numerical example and compared with the conventional method.

A Study on Improvement of Inflow/Infiltration Computation and Application Method in Sewer Rehabilitation Project (하수관거정비사업의 침입수/유입수 산정 및 활용방법 개선방안에 관한 연구)

  • Kim, Jong-Oh;Jeong, Dong-Gi;An, Dae-Hoon
    • Journal of Korean Society of Water and Wastewater
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    • v.28 no.1
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    • pp.33-45
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    • 2014
  • In this study, current sewer infiltration/Inflow(I/I) computation and application method was examined about improvement and adequacy relating to the main issues raised by the field for practitioners. The results of review about infiltration calculation method were considered to be in need of improvement at 'standards of minimum sewage calculation'. Furthermore, the results of review about I/I application method were considered to be in need of improvement at 'standards of seasonal infiltration application' and 'the relative decrease in the Annual evaluation standards'. In addition, annual I/I analysis at JC County for the four years(2009~2012) in respect of operation flow and rainfall data was conducted. The result of annual infiltration analysis, compared average daily sewage generated average infiltration rate was found in 21.95 %, infiltration by unit was found in $0.31m^3/day/cm/km$ and $0.12m^3/day/day$, respectively. The result of annual inflow analysis, average rainfall - Inflow equations was found $y=5.499{\times}$($R^2$ 0.793), and the average Inflow quantity by sewer extension was predicted to $0.66m^3/mm-km$.

Finite Element Analysis of Auto-body Panel Stamping (리어 힌지 패널 스템핑의 유한요소해석)

  • 정동원;이장희;양동열
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1996.06a
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    • pp.97-109
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    • 1996
  • In the present work computations are carried out for analysis of complicated sheet metal forming process such as forming of a rear hinge. Finite element formulation using dynamic explicit time integration scheme and step-wise combined Implicit/Explicit scheme are introduced for numerical analysis of sheet metal forming process. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. The explicit scheme in general use is based on the elastic-plastic modelling of material requiring large computation time. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implicit/explicit scheme has been developed.