• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.934-938
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• 2003

Flow analyses using FLUENT 5.4 code were performed to validate the application of the local bidirectional flow tube in case of water and air flow. In this study, sensitivity studies have been performed to optimize the design features of the bi-directional flow tube which can be applied for the various experimental conditions. 2-dimensional axisymmetric steady state flow analyses have been performed. By calculating the differential pressure at both the front and the rear hole of the flow tube, K values were evaluated. The K values show good linearity regardless of the tube sizes and the Re numbers in both water and air flow. And system pressure and water subcooling didn’'t affect the K values. Under the elevated pressure of 80bar with 80K water subcooling, the K value indicates a similar trend with the case of 2bar with 80K water subcooling.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.911-916
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• 2002

One of important roles of concrete track is to reduce vibration transmitting to subgrade. In this paper, a numerical method for evaluating the effects of vibration reduction of concrete track is presented. Using the method, high frequency dynamic analyses and track-tunnel-soil interaction analyses are carried out for three types of concrete track in order to investigate the vibration reduction effects compared with normal ballast track.

• 지역연구
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• 제11권1호
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• pp.21-30
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• 1995

This paper deals with the forecasting models for traffic accident by region. Its objectives are to develop the appropriate model for projecting the accident and to analyze the regional characteristics of the accident model. The main results are as follow. First, the literature review, statistical tests and sensitivity analyses show that the joint model combined both PTM and Exponential functions is appropriate to project the traffic accidents by region. Second, the statistical analyses by region. Second, the statistical analyses on the regional accident models indicate that the levels of significance in terms of t-value, $R^2$ and F-value are very high. Finally, the comparative analyses among regions show that the regional differences on the accident patterns can be explained by the joint models and the accident indices (parameters, $P_{max}$, 1/b, $\eta$ etc.) of each region.

• 전기학회논문지P
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• 제61권4호
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• pp.192-198
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• 2012

Switch losses directly affect the efficiency of power conversion systems and those have big differences according to the power consumed by load systems and the structures of power conversion circuits. In this paper, analyses for switch losses in DC link converter are performed based on the circuit structures of the DC/DC converter in photovoltaic generation system whose output power is varied according to the amount of solar radiation, temperature and partial shade on the solar modules. Boost converter is adopted as a DC link converter topology of the photovoltaic generation system and the loss analyses for the switches used in the boost converters are performed according to the circuit structures. Analyses like the things performed in this paper will be a prerequisite to designing the photovoltaic generation system whose output power is changed according to the environmental variations.

• Structural Engineering and Mechanics
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• 제8권1호
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• pp.1-18
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• 1999

Procedures are investigated by which nonlinear finite element shell analysis algorithms can be simplified to provide more cost effective approximate analyses of orthogonally-reinforced concrete flat plate structures. Two alternative effective stiffness formulations, and an unbalanced force formulation, are described. These are then implemented into a nonlinear shell analysis algorithm. Nonlinear geometry, three-dimensional layered stress analyses, and other general formulations are bypassed to reduce the computational burden. In application to standard patch test problems, these simplified approximate analysis procedures are shown to provide reasonable accuracy while significantly reducing the computational effort. Corroboration studies using various simple and complex test specimens provide an indication of the relative accuracy of the constitutive models utilized. The studies also point to the limitations of the approximate formulations, and identify situations where one should revert back to full nonlinear shell analyses.

• Structural Engineering and Mechanics
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• 제32권6호
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• pp.811-833
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• 2009

In the present article bending, buckling and vibration analyses of tapered beams using Eringen non-local elasticity theory are being carried out. The associated governing differential equations are solved employing Rayleigh-Ritz method. Both Euler-Bernoulli and Timoshenko beam theories are considered in the analyses. Present results are in good agreement with those reported in literature. Beam material is considered to be made up of functionally graded materials (fgms). Non-local analyses for tapered beam with simply supported - simply supported, clamped - simply supported and clamped - free boundary conditions are carried out and discussed. Further, effect of length to height ratio on maximum deflections, vibration frequencies and critical buckling loads are studied.

• Geomechanics and Engineering
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• 제5권4호
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• pp.313-329
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• 2013

Vetiver grass (Vetiveria zizanioides) is being effectively used in many countries to protect embankment and slopes for their characteristics of having long and strong roots. In this paper, in-situ shear tests of the ground with the vetiver roots have been conducted to investigate the stabilization properties corresponding to the embankment slopes. Numerical analyses have also been performed with the finite element method using elastoplastic subloading $t_{ij}$ model, which can simulate typical soil behavior. It is revealed from field tests that the shear strength of vetiver rooted soil matrix is higher than that of the unreinforced soil. The reinforced soil with vetiver root also shows ductile behavior. The numerical analyses capture well the results of the in-situ shear tests. Effectiveness of vetiver root in geotechnical structures-strip foundation and embankment slope has been evaluated by finite element analyses. It is found that the reinforcement with vetiver root enhances the bearing capacities of the grounds and stabilizes the embankment slopes.

• Structural Engineering and Mechanics
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• 제3권2호
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• pp.145-162
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• 1995

A damped trapezoidal rule method for numerical time-integration is presented, and its application in analyses of dynamic response of damped structures is discussed. It is shown that the damped trapezoidal rule method has features that make it an attractive approach for applications in dynamic analyses of structures. Accuracy and stability analyses are developed for the damped single-degree-of-freedom systems. Error analyses are also performed for the Newmark beta method and compared with the damped trapezoidal rule method as a basis for discussion of the relative merits of the proposed method. The procedure is fully explicit and easy to implement. However, since the method is an explicit method, it is conditionally stable. The methodology is applied to several example problems to illustrate its strengths, limitations and inherent simplicity.

• 한국국방경영분석학회지
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• 제34권1호
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• pp.47-59
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• 2008

본 연구는 방위산업체의 연구개발 투자활동이 경영성과에 대하여 어떠한 영향을 미치는지에 대하여 실증적 분석을 수행하였다. 연구의 주요 분석 결과에 대해서 살펴보면 다음과 같다. 첫째, 방위산업체의 성장성 증대를 위해서는 연구인력의 교육지원 기회 확대, 관련부서간의 긴밀한 협력이 필요한 것으로 나타났다. 둘째, 방위산업체의 생산성 증대를 위해서는 연구개발 투자비를 증대해야 하며, 셋째, 방위산업체의 수익성 증대를 위해서는 관련부서 간 협력강화가 정(+)의 영향을 미치는 것으로 나타났다.

• The Korean Journal of Ecology
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• 제9권4호
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• pp.225-230
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• 1986

The environmental gradient analyses and the continum analyses were applied for the ordinationa of forest vegetation in Seonunsan area. In the soil moisture gradient, mesic to xeric, Zelkova serrata, Carpinus tschonoskii, Quercus aliena, Carpinus laxiflora, Quercus serrata, Quercus variabilis and Pinus densiflora type were arranged as a series of sequence along the gradient. In two dimensional analyses of soil moisture and organic matter gradients seven vegetation types mentioned above were also separated one another. Especially Carpinus tschonoskii in mesic-fertile sites adn Pinus densiflora in xeric-sterile were noticeable. The results of continum analyses were corresponded to those of environmental gradient analses for the forest vegetation.