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Acoustic Analysis for Design Optimization of Hub-Blade Baffle in Liquid Rocket Engine (액체로켓엔진에서 음향해석을 통한 허브-블레이드 배플 형상의 최적화)

  • Kim, Hong-Jip;Kim, Seong-Ku;Seol, Woo-Seok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.8 s.227
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    • pp.945-952
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    • 2004
  • Acoustic characteristics of combustion chamber having various baffle configurations are numerically investigated by linear acoustic analysis to suggest reliable baffle specifications in first stage of KSLV-I. To determine the configuration of baffles, an acoustic modal analysis as well as the macroscopic analysis has been done. Hub has another effect of suppressing transverse acoustic mode by confining flow in baffled compartment over general effect of increase in acoustic damping of radial acoustic modes. So, a sufficient number of hub needs to be installed to obtain acoustic damping capacity. 3-blade configuration designed to suppress the first tangential mode has relatively low damping capacity, compared to 5 or 6-blade one. Optimum value of axial baffle length has been determined by comparing acoustic characteristics of combustion chamber having various baffle lengths.

A study on the Teflon crack Molding Method (테프론 균열 주형법 開發에 관한 硏究)

  • 최상인;최선호;황재석
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.6
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    • pp.945-952
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    • 1987
  • In this paper, Crack molding method called "Teflon crack Molding Method" is developed. With help of this method, we can mold a crack which is very similar to the natural crack, which has the tip radius of about 20.mu. the vertical and horizontal quality of crack excellent. In addition to these, by using this method in photoelastic experiment we can obtain the clear crack tip location and Isochromatic fringe pattern boundary, therefore the precise in the experimental data can be improved. improved.

A study on Yeosu area communication history in the old documents II (고문서에 나타난 여수지역 통신역사에 관한 고찰 II)

  • Kim, Chun-Suk
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.5
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    • pp.945-953
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    • 2012
  • Yeosu area from the old historical monuments and artifacts related communications signal station, directions display panels, lighthouse, Geomundo the first submarine cable installation, etc. That appears in old documents and communications of the area should check the history and development of communication in understanding the Yeosu area and communicate the need to identify resources historicity.

Failure prediction system based on expert knowledge (전문가 지식 기반 고장예측시스템)

  • Kim, Dohyeong;Lee, Sungyoung
    • Proceedings of the Korea Information Processing Society Conference
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    • 2017.04a
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    • pp.945-947
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    • 2017
  • 알람시스템은 효율적인 공장운영과 인력에 의한 설비진단 및 고장예방 활동을 돕기 위해 이용된다. 알람시스템은 설비진단과 고장예방 활동을 위해서 설비에 부착된 다양한 센서로 부터 발생하는 알람을 수집하고 설비관리자에게 제공하여 조기에 문제를 파악하고 조치할 수 있도록 하는 역할을 하고 있다. 하지만 알람시스템이 단순히 정보 수집을 목적으로 설계되어 현장전문가 처리할 수 없는 수준으로 알람을 대량 발생시킨다. 본 논문에서는 발생 알람으로부터 발생 가능한 고장을 예측하기 위해 현장 전문가의 경험 지식에 기반한 고장예측 시스템을 제안한다.

Research on In-vehicle, Real-time Measurement of Road Grades (도로 경사도의 실시간 측정 방법에 관한 연구)

  • Kim, Younggwan;Park, Jinil;Lee, Jonghwa
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.6
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    • pp.945-949
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    • 2013
  • By using information about specific road grades, one can predict the power required by a vehicle. The prediction of the required power enables the driver to choose the driving route with the best fuel economy, which results in cost and energy savings. A clinometer is one of the more simple tools used to measure road grades, but requires significant time and effort. In this paper, a new method for measuring road grades from within a vehicle is proposed and experimentally verified.

A Qualitative Study on University Students' Multicultural Competence - Focusing on the Cultural Cognition, Cultural Knowledge and Cultural Skill - (대학생의 다문화 역량에 관한 연구 - 문화적 인식, 지식, 기술을 중심으로 -)

  • Kim, Min-Kyeong
    • Korean Journal of Human Ecology
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    • v.19 no.6
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    • pp.945-965
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    • 2010
  • The present study examined the cultural competence of university students on migrants and multicultural society in Korea. A total of 11 university students living in Seoul, Gyeonggido and Chungcheondo, were selected for the interview. The participants provided their cultural cognition, cultural knowledge and cultural skill on a variety of issues related to migrants and multicultural society in Korea. Interview results indicated that participants perceived negative and positive affects to Korean society and prejudice about immigrants, thaught economic support as a emergent policy, and didn't experience multicultural society. They wanted to take a trip and learning foreign language. On the cultural skill participants had progressive perspectives about immigrants' right, discrimination and evaluation and had a multiculturism based on assimilation. Implications of the study and directions for future research were discussed. It is needed to educations and programs for development of university students' cultural competence.

Ω-RESULT ON COEFFICIENTS OF AUTOMORPHIC L-FUNCTIONS OVER SPARSE SEQUENCES

  • LAO, HUIXUE;WEI, HONGBIN
    • Journal of the Korean Mathematical Society
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    • v.52 no.5
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    • pp.945-954
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    • 2015
  • Let ${\lambda}_f(n)$ denote the n-th normalized Fourier coefficient of a primitive holomorphic form f for the full modular group ${\Gamma}=SL_2({\mathbb{Z}})$. In this paper, we are concerned with ${\Omega}$-result on the summatory function ${\sum}_{n{\leqslant}x}{\lambda}^2_f(n^2)$, and establish the following result ${\sum}_{\leqslant}{\lambda}^2_f(n^2)=c_1x+{\Omega}(x^{\frac{4}{9}})$, where $c_1$ is a suitable constant.

A New Robust Variable Structure Controller for Uncertain Affine Nonlinear Systems with Mismatched Uncertainties (부정합조건 불확실성을 갖는 비선형 시스템을 위한 새로운 강인한 가변구조제어기)

  • Lee, Jung-Hoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.5
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    • pp.945-949
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    • 2010
  • In this paper, a systematic design of a new robust nonlinear variable structure controller based on state dependent nonlinear form is presented for the control of uncertain affine nonlinear systems with mismatched uncertainties and matched disturbance. After an affine uncertain nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a new robust nonlinear variable structure controller is presented. To be linear in the closed loop resultant dynamics, the linear sliding surface is applied. A corresponding control input is proposed to satisfy the closed loop exponential stability and the existence condition of the sliding mode on the linear sliding surface, which will be investigated in Theorem 1. Through a design example and simulation study, the usefulness of the proposed controller is verified.

Experimental Study on Flow Noise Generated by Axisymmetric Boundary Layer ( I ) - Wall Pressure Fluctuations on Axisymmetric Noses and on a Cylinder in an Axial Flow - (축대칭 물체의 경계층 유동소음에 대한 실험적 연구 ( I ) - 축대칭 물체 전두부 및 실린더 벽면 섭동압력 -)

  • Lee, Seung-Bae;Kim, Hooi-Joong;Kwon, O-Sup;Lee, Sang-Kwon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.7
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    • pp.945-956
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    • 2000
  • The axisymmetric bodies considered in this study have hemispherical and ellipsoidal noses. The near-field pressure fluctuations over each nose model at $Re_D=2.43{\times}10^5$ were investigated in the laminar separation region and developing turbulent boundary layers using a 1/8' pin-holed microphone sensor. The wall pressure fluctuations were also measured in an axisymmetric boundary layer on a cylinder parallel to mean flow at a momentum thickness Reynolds number of 850 and a boundary layer thickness to cylinder radius ratio of 1.88.