• Journal of applied mathematics & informatics
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• 제37권3_4호
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• pp.251-257
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• 2019

We study the orbit behaviours of recurrent, uniformly recurrent and Poisson stable points. we give conditons that a point is to be recurrent or uniformly recurrent by analyzing the behaviours of their orbits. Also, we study dynamical properties of equicontinuous points and points of characteristic $0^+$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.103-110
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• 2003

This study is as for shale that attract recently geotechnical engineer more and more. like sedimentary rocks and metamorpic rocks, shales have many problem with anisotropy for stength and deformation and they have many problems with quick weathering progress and differential weathering of alternate bedding. In foreign countries, many renowned schalors, like Jaeger(1960),McLamore,Gray(1967),Donath(1972),Nova(1980),Hoek&Brown(1980),Ranamurthy(1985), have already studied for a variety of characteristic and announced high level results of their studies. In domestic also, there are many scholars who have announced high level research papers for shale. this study is a part of these stream. and this study not only analyzed strength anisotropy characteristic along with direction of testing(two-direction) by using point-load test(log-log method) but also compared uniaxial strength between the maximum saturated and dried condition. In this study, we also conducted slaking test. these results of slaking test show weathering characteristic of shales. also, we made the most of field data that obtained during slope stability project and we noticed that RQD measured in the field is much differ from drilled core RQD. In order to come close two different value or access to reality, we suggest new RQD method that artificially reduce RQD by separating core with light hand force.

• 대한기계학회논문집
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• 제16권7호
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• pp.1285-1293
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• 1992

본 연구에서는 glass/epoxy 직조된 복합재료에 있어서 원공 및 판폭의 크기가 노치강도에 미치는 영향을 명확히 하고, 또한 노치강도 및 파괴조건과 위에서 언급한 특성길이와의 관계를 검토하였다.

• 한국전산유체공학회지
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• 제5권1호
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• pp.43-59
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• 2000

Characteristic boundary conditions are discussed in conjunction with a flux-difference splitting formulation as modified from Roe's linearization. Details of how one can implement the characteristic boundary conditions which are made compatible with the interior point formulation are described for different types of boundaries including subsonic outflow and adiabatic wall. The validity of boundary conditions are demonstrated through computation of transonic airfoil, supersonic ogive-cylinder, hypersonic cylinder, and S-duct internal flows. The computed wall pressure distributions are compared with published experimental and computed data. Objectives of this paper are thus to give insight of formulation procedure of a flux-difference splitting method and to pave ways for other users to adopt present boundary procedure on their numerical methods.

• 한국안전학회지
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• 제18권4호
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• pp.8-15
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• 2003

A study on predicting the joint strength of mechanically fastened woven glass/epoxy composite has been performed. An experimental and numerical study were carried out to determine the characteristic length and joint strength of composite joint. The characteristic lengths for tension and compression were determined from the tensile and compressive test with a hole respectively. The characteristic lengths were evaluated by applying the point stress failure criterion to a specimen containing a hole at the center subjected to tensile loading and a specimen containing a half circular notch at the center subjected to compressive load. The joint strength was evaluated by the Tsai-Wu and Yamada-Sun failure criterion on the characteristic curve. The predicted results of the joint strength were compared with experimental results.

• 대한토목학회논문집
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• 제28권1A호
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• pp.125-133
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• 2008

사장교의 장대화로 주탑 및 보강형과 더불어 사장 케이블의 동적 안정화에 많은 노력이 요구된다. 사장 케이블에서 동적 불안정은 주로 대칭 1모드와 역대칭 1모드에서 발생되며 대칭 1모드는 역대칭 1모드와 다르게 새그의 영향이 명확하게 나타나므로 기본진동수는 팽팽한 스트링으로부터 얻은 것과 상이한 결과를 제공하게 된다. 이러한 현상에 관해 Irvine, Triantafyllou, 안상섭 등은 해석적 기법을 통해 동적거동 분석을 수행하였다. 이들의 연구는 광범위한 영역의 Irvine Parameter에 대해 중요한 결과를 제시하였으나 특성점(Cross-Over Point 혹은 복합모드 형성점) 이후 영역에 대해서는 상이한 결과를 제시하였고 진동수방정식의 높은 비선형성으로 인해 해가 매우 민감한 난점이 있다. 본 연구는 사장 케이블 동적안정 문제에 주요한 모드들 중 새그의 영향이 가장 높은 대칭 1모드의 기본진동수에 초점을 맞추었으며 일반화된 역학적에너지에 경계조건을 만족시키는 진동형상을 적용하고 Rayleigh-Ritz 방법으로 해석적인 해를 제시하였다. 선행연구들과 다르게 본 연구는 선형적인 해를 제공하며 이에 따른 오차는 특성점 이내에서 3% 미만의 오차를 보였다. 또한, 사장 케이블이나 이에 준한 케이블은 특성점을 넘지 않으므로 공학적으로 충분한 가치를 갖는다고 볼 수 있다. 더불어 대칭 1모드에서 발생되는 갤로핑과 Parametric 공진대역을 분석하여 연구의 활용성을 확인하였다.

• 조명전기설비학회논문지
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• 제21권3호
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• pp.62-68
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• 2007

최근 전력 전자 응용 기기의 사용증가로 비선형 특성 부하에 의한 고조파가 상당히 발생하고 있으며, 이에 의한 영향으로 배전시스템의 변압기 열화, 소자의 고장, 통신 간섭 등의 여러 가지 문제를 발생시키고 있다. 따라서 배전 시스템에서의 고조파 수준과 전달특성을 정확하게 분석하기 위하여 배전시스템의 효과적인 실측정과 모델링에 관한 연구가 필요한 실정이다. 본 논문에서는 고조파 관리기준 IEC61000-3-6 토대로 배전 시스템의 고조파 특성을 해석하기 위하여 공통 결합점(Point of Common Coupling : PCC)을 선택하였다. 실 배전 시스템의 PCC 지점에서 고조파 전압, 전류를 측정하여, 고조파 분포, 비선형 부하 성분 및 고조파 전압, 전류 왜형률 (Voltage/Current Total Harmonic Distortion: VTHD/ITHD)을 분석하였다. 또한 정상상태에서 고조파 임피던스, 전압, 전류을 해석을 통하여 실 배전시스템을 효과적이고 정확하게 모델링 되었을 확인하였다. 또한 고조파 전류원 발생시에 고조파 전압, 전류를 비교 분석하여 고조파 전달특성을 조사하였다.

• 한국해양공학회지
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• 제7권2호
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• pp.57-67
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• 1993

The fracture behavior of plain woven glass/epoxy composite plates with a crack is investigated under static tensile loading. It is shown in this paper that the characteristic length associated with the point stress criterion depends on the crack length. To predict the not ched tensile strength, the point stress criterion proposed by Whitney and Nuismer are modified. An excellent agreement is found between the experimental results and the analytical prediction of the modified point stress criterion. The condition of unstable crack growth in the presence of a per-existing flaw(machined notch) is examined by means of the maximum stress intensity factor $K_max$ using maximumload P$_max$. The values of $K_max$ evaluated from energy release rate G$_max$(the compliance me thod) indicate a wide difference. Therefore in regard to anisotropy and heterogeneity of the composite materials studied, the modified shape correction factor f(a/W) is obtained. $K_max$evaluated by the compliance method a little or insignificantly depends on the initial crack length a, the specimen thickness B, the crack angle .theta. and the specimen geometry.

• Journal of applied mathematics & informatics
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• 제10권1_2호
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• pp.17-26
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• 2002

A stability analysis of a non-linear prey-predator system under the influence of one dimensional diffusion has been investigated to determine the nature of the bifurcation point of the system. The non-linear bifurcation analysis determining the steady state solution beyond the critical point enables us to determine characteristic features of the spatial inhomogeneous pattern arising out of the bifurcation of the state of the system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.277-280
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• 2002

This paper analyze the characteristics of three multipliers in finite fields GF(2m) from the point of view of processing time and area complexity. First, we analyze structure of three multipliers; 1) LSB-first systolic array, 2) LFSR structure, and 3) CA structure. To make performance analysis, each multiplier was modeled in VHDL and was synthesized for FPGA implementation. The simulation results show that LFSR structure is best from the point of view of area complexity, and LSB systolic array is best from the point of view of processing time per clock.