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박철희,송석홍,신현재,홍성철 한국소음진동공학회 1993 소음 진동 Vol.3 No.2
The conventional dynamic vibration absorber is very efficient in inhibiting the vibration of a machine. This is accomplished by 'tuning' the absorber to the frequency of the harmonic disturbing force. If, however, the frequency of the disturbing force varies over a tuning frequency range in the normal operation of the system, the linear dynamic absorber may become inoperative and might aggravate matters particularly. This study is to endow the dynamic absorber with greater flexibility in suppressing vibrations throught a range of frequencies of the disturbing force. By introducing springs with nonlinear characteristics into its design, the results can be obtained. In this paper, the machine and the absorber were modelled as a nonlinear two-degree-of freedom system. And the concepts of nonlinear normal mode were adopted to obtain this purpose.s purpose.
선형모드에서 작동하는 Microchannel Plate 증폭특성의 실험분석
박철희,송현석 崇實大學校 生産技術硏究所 2002 論文集 Vol.32 No.-
In order to understand the repetitive multiplication process in a continuous dynode operated in linear mode, we have measured the pulse height distribution of a Microchannel Plate operating in linear mode in response to a single incident electron. Contrary to the current understanding, we observed that the pulse height distribution not only has a long negative-exponential tail but a peak clearly separated from background nosie even when only one input electron. We set up a Monte Carlo simulation of the repetitive multiplication precess in a microchannel. The simulation parameters were adjusted to best fit the experimental results. The results of the simulation were compared with the experimental data. We observed that the pulse height distribution of a Microchannel Plate with an electron as an input particle differ from that with a ultraviolet photon due to the fact that an electron can create more than one secondary electron in its first collision.
박철희 崇實大學校 2000 論文集 Vol.30 No.1
We present a preliminary measurement of the rate of gluon splitting into bottom quarks, g→b□ , in hadronic Z0 decays collected by SLD between 1996 and 1998. The analysis was performed by looking for secondary bottom production in 4-jet events of any primary flavor. 4-jet events were identified, and a topological vertex-mass technique was applied to each jet in order to identify b or □ jets. The upgraded CCD based vertex detector gives very high B-tagging efficiency, especially for B hadrons of the low energies typical of this process. The two most nearly collinear b/□ jets were tagged as originating from g→bb. We measured the rate of secondary b/□ production per hadronic event, gb□, to be (3.07 ± 0.71(stat.) ± 0.66(syst.)) x10³ (preliminary).
박철희,홍성철,박용석 한국소음진동공학회 1994 소음 진동 Vol.4 No.2
This paper deals with the dynamic stability and the nonlinear behavior of a check valve system. The nonlinear equations of motion of fluid-valve interation model are derived, which are composed of the unsteady Bernoulli's equation included the jet flow mechanism and equation of motion of a check valve formulated by one degree of freedom. Also, the derived equations of motion are nondimensionalized. According to the change of the nondimensional parameters, the stabilities of the system are analyzed, and the nonlinear interaction responses of the check valve and the passing flow rate are obtained. As the results, the stability charts are constructed for the variation of nondimensional parameters. It is shown that self-excited vibrations exist in a check valve system. And also the Hopf bifurcation and the periodic doubling are found. The presented theoretical model of a check valve system can be utilized to the design and operation of a piping system with the check valve.
일제강점기 중등학생의 일기를 통해 본 식민교육(학술대회지)
박철희 한국교육사회학회 2016 한국교육사회학회 학술대회 발표 자료 Vol.2016 No.-
우리 세대에게 학창시절 일기를 쓰고, 선생님이 일기장을 검사하는 일은 흔한 일이었지 만, 요즘 학교현장에서는 이와 같이 일이 흔치는 않은 것 같다. 교사가 학생일기를 검사하 는 것이 학생들을 이해하는데 도움이 되고, 학생들에게 일기 쓰는 습관을 길러줌으로써 글쓰기와 자신의 생활을 돌아보는데 도움이 된다는 긍정적 의견도 있지만, 학생들의 사생 활과 인권을 침해하는 행위라는 부정적 의견도 있다.