• Wind and Structures
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• 제28권2호
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• pp.89-97
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• 2019

The non-linear equations governing wind-induced internal pressures for a two-compartment building with background leakage are linearized based on some reasonable assumptions. The explicit admittance functions for both building compartments are derived, and the equivalent damping coefficients of the coupling internal pressure system are iteratively obtained. The RMS values of the internal pressure coefficients calculated from the non-linear equations and linearized equations are compared. Results indicate that the linearized equations generally have good calculation precision when the porosity ratio is less than 20%. Parameters are analyzed on the explicit admittance functions. Results show that the peaks of the internal pressure in the compartment without an external opening (Compartment 2) are higher than that in the compartment with an external opening (Compartment 1) at lower Helmholtz frequency. By contrast, the resonance peak of the internal pressure in compartment 2 is lower than that in compartment 1 at higher Helmholtz frequencies.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.465-470
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• 2001

This paper presents an algorithm which seeks steady-state equilibrium positions of constrained multibody systems driven by constant generalized speeds. Since the relative coordinates are employed, the constraint equations at cut joints are incorporated into the formulation. The proposed algorithm leads to nonlinear equations that need to be solved iteratively. This algorithm should satisfy both types of conditions: the force equilibrium equations and the kinematic constraint equations. To verify the effectiveness of the proposed algorithm, two numerical examples are solved and the results are compared with those of a commercial program. This method, compared to the conventional method of using dynamic analysis, has the advantage of computational efficiency and stability.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.267-270
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• 2001

A lot of efforts have been made to analyze the performance of the vehicle equipped with automatic transmission through simulation. It might be necessary to understand the different types of transmissions, i.e., different power flows, for different models. If there is a module that can be applied to different types of automatic transmission, it could be helpful to transmission-related engineers. This study has started up from this idea. The common bond graph has been obtained from several types of the automatic transmission. The overall generalized equations and kinematic constraint equations have been derived using virtual power sources on common bond graph. They are used to derive state equations and constraints. These equations have been applied as an application to the vehicle equipped with two simple planetary gear set type of Ravigneaux gear type automatic transmission. The state equation, kinematic constraints, and dynamic constraints have been derived in every gear and shift operation using overall generalized equations and kinematic constraint equations. Simulations for constraint speed running, standing-start running, rolling-start running, and LA-4 mode have been conducted to analyze the performance of the vehicle powertrain using GVPS(Generalized Vehicle Powertrain Simulation) program wit pull down menus.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.205-210
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• 2001

Cubic equations of state with two temperature dependent parameters are suggested and optimized using ASHRAE data for methane, propane, carbon dioxide, R-32 and R-134a. Appropriate simple functional forms are assumed for the temperature dependent parameters. The equations tested are Martin, Fuller, Harmens-Knapp, Schmidt-Wenzel. Among them modified Schmidt-Wenzel equation of state appears to be the choice for calculation of saturation properties such as vapor pressures, saturated liquid volumes, and saturated vapor volumes with an average absolute deviation of about one percent over the entire region excluding; the near cirtical.

• 대한수학회보
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• 제48권6호
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• pp.1271-1290
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• 2011

The purpose of this paper is to investigate the controllability of certain types of second order nonlinear impulsive systems with statedependent delay. Sufficient conditions are formulated and the results are established by using a fixed point approach and the cosine function theory Finally examples are presented to illustrate the theory.

• Coupled systems mechanics
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• 제8권2호
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• pp.147-168
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• 2019

This work aims to simulate three-dimensional heavy oil flow in a reservoir with heater-wells. Mass, momentum and energy balances, as well as correlations for rock and fluid properties, are used to obtain non-linear partial differential equations for the fluid pressure and temperature, and for the rock temperature. Heat transfer is simulated using a two-equation model that is more appropriate when fluid and rock have very different thermal properties, and we also perform comparisons between one- and two-equation models. The governing equations are discretized using the Finite Volume Method. For the numerical solution, we apply a linearization and an operator splitting. As a consequence, three algebraic subsystems of linearized equations are solved using the Conjugate Gradient Method. The results obtained show the suitability of the numerical method and the technical feasibility of heating the reservoir with static equipment.

• Tribology and Lubricants
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• 제11권5호
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• pp.10-14
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• 1995

Over 300 equations and models were found in the leterature on friction and wear. No single equation on limited group of equations could be found for general on practical use. Recommandations are offered for improving the future yield of useful equatio

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.787-813
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• 2014

Starting with Hamilton's variational principle, the governing field equations for the steady state response of thin-walled beams under harmonic forces are derived. The formulation captures shear deformation effects due to bending and warping, translational and rotary inertia effects and as well as torsional flexural coupling effects due to the cross section mono-symmetry. The equations of motion consist of four coupled differential equations in the unknown displacement field variables. A general closed form solution is then developed for the coupled system of equations. The solution is subsequently used to develop a family of shape functions which exactly satisfy the homogeneous form of the governing field equations. A super-convergent finite element is then formulated based on the exact shape functions. Key features of the element developed include its ability to (a) isolate the steady state response component of the response to make the solution amenable to fatigue design, (b) capture coupling effects arising as a result of section mono-symmetry, (c) eliminate spatial discretization arising in commonly used finite elements, (d) avoiding shear locking phenomena, and (e) eliminate the need for time discretization. The results based on the present solution are found to be in excellent agreement with those based on finite element solutions at a small fraction of the computational and modelling cost involved.

• 한국추진공학회지
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• 제26권5호
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• pp.24-34
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• 2022

초임계 영역에서 작동하는 탄화수소 연료를 사용하는 재생냉각채널의 냉각성능을 예측하기 위해서는 타당한 물성 예측이 필수이다. 본 연구는 고분자 탄화수소의 임계 압축인자에 따라 밀도와 비열을 적절하게 예측하기 위해 2-파라미터 상태방정식인 SRK(Soave-Redlich-Kwong) 및 PR(Peng-Robinson) 상태방정식과 이를 합한 3-파라미터 상태방정식인 RK-PR 상태방정식에 대한 비교 분석을 수행하였다. 대표적으로 낮은 임계압축 인자를 갖는 n-dodecane 연료와 높은 임계압축 인자를 갖는 JP-10 연료를 선정하여 두 연료의 열역학적 물성을 예측할 때 적합한 상태방정식을 제시하였다. 마지막으로 밀도와 비열의 예측 결과를 NIST REFPROP 데이터와 비교하여 검증하였다.

• 터널과지하공간
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• 제13권5호
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• pp.389-396
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• 2003

본 연구는 정상류 Navier-Stokes 방정식에 섭동(perturbation) 이론을 적용하여 주기함수 간극에 대한 삼승법칙의 수정에 대해 논하였다. 이를 위해, 주기함수를 진폭과 파장에 대한 무차원 함수로 전환한 뒤 미소 계수에 대한 무차원 유동함수와 연속 방정식을 적용하였다. 이러한 과정을 통해 정상류 Navier-Stokes 방정식의 섭동 근사해를 구하였으며 이를 유한 차분법에 적용하였다. 단일 절리 모델에 대한유한 차분 수치해석을 통해, 수정된 삼승 법칙이 주기함수 간극의 유체 유동에 대한 정상류 Navier-Stokes 방정식의 섭동 근사해와 잘 일치하는 것으로 나타났다. 이를 통해 본 연구에서 제시된 삼승 법칙이 간극 분포에 따른 유체 유동의 평가에 있어 유용하게 적용될 수 있는 것으로 나타났다.