• 소음진동
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• 제8권1호
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• pp.203-211
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• 1998

In order to find out relationship between hit probability and gun firing of a moving tank, a turret and flexible gun system model has been developed using a recursive flexible multibody dynamics. For a firing simulation model, nodal coordinates for a finite element model of a flexible gun have been employed to include transverse loads to the gun tube due to moving bullet and ballistic pressure. Modal coordinates are also used to represent the motion induced gun vibration before a firing occurs. An efficient switching technique from modal equations to nodal equation has been introduced for an entire gun firing simulation with a rotating turret.

• Nuclear Engineering and Technology
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• 제27권6호
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• pp.870-876
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• 1995

해석함수전개 노달방법에 기초한 새로운 3차원 노달확산 코드가 개발되었다. 이 방법은 균질화된 노드내의 해를 노드내에서 중성자확산방정식을 만족하는 해석적인 18개의 기저함수들과 1개의 상수로 전개한후 노달연관방정식을 노드에 대한 중성자의 균형, 경계면에서의 중성자류의 연속, 모서리주위의 무한히 작은 체적소에 대한 중성자누출의 균형이 만족되도록 유도한다. 이 코드의 정확성을 검증한기 위해 잘 알려진 LMW 표준문제와 IAEA 3차원 문제와 동일한 물질을 가지는 작은 노심문제에 적용하여 QUANDRY코드 및 VENTURE코드의 결과와 비교하였다. 계산결과들은 본 연구에서 개발된 코드가 출력분포 및 유효중배계수를 매우 정확하게 예측함을 보여준다.

• International Journal of Precision Engineering and Manufacturing
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• 제5권4호
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• pp.50-60
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• 2004

A very flexible beam can be used to model various types of continuous mechanical parts such as cables and wires. In this paper, the dynamic properties of a very flexible beam, included in a multibody system, are analyzed using absolute nodal coordinates formulation, which is based on finite element procedures, and the general continuum mechanics theory to represent the elastic forces. In order to consider the dynamic interaction between a continuous large deformable beam and a rigid multibody system, a combined system equations of motion is derived by adopting absolute nodal coordinates and rigid body coordinates. Using the derived system equation, a computation method for the dynamic stress during flexible multibody simulation is presented based on Euler-Bernoulli beam theory, and its reliability is verified by a commercial program NASTRAN. This method is significant in that the structural and multibody dynamics models can be unified into one numerical system. In addition, to analyze a multibody system including a very flexible beam, formulations for the sliding joint between a very deformable beam and a rigid body are derived using a non-generalized coordinate, which has no inertia or forces associated with it. In particular, a very flexible catenary cable on which a multibody system moves along its length is presented as a numerical example.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3213-3228
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• 2023

As an important part of the digital reactor, the pin-by-pin wise fine coupling calculation is a research hotspot in the field of nuclear engineering in recent years. It provides more precise and realistic simulation results for reactor design, operation and safety evaluation. CORCA-K a nodal code is redeveloped as a robust pin-by-pin wise neutronics and thermal-hydraulic coupled calculation code for pressurized water reactor (PWR) core. The nodal green's function method (NGFM) is used to solve the three-dimensional space-time neutron dynamics equation, and the single-phase single channel model and one-dimensional heat conduction model are used to solve the fluid field and fuel temperature field. The mesh scale of reactor core simulation is raised from the nodal-wise to the pin-wise. It is verified by two benchmarks: NEACRP 3D PWR and PWR MOX/UO₂. The results show that: 1) the pin-by-pin wise coupling calculation system has good accuracy and can accurately simulate the key parameters in steady-state and transient coupling conditions, which is in good agreement with the reference results; 2) Compared with the nodal-wise coupling calculation, the pin-by-pin wise coupling calculation improves the fuel peak temperature, the range of power distribution is expanded, and the lower limit is reduced more.

• Nuclear Engineering and Technology
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• 제27권3호
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• pp.374-384
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• 1995

해석함수 전개 노달방법의 수학적 수한해를 AFEN코드에 약간의 수정을통하여 AFEN노달 방정식의 전치행 렬 방정식을 풀어서 계산하였다. 또한 이 수반해를 사용하여 섭동이론(정확한 섭동이론과 일차근사 섭동이론)을 이용한 계산이 반응도 변화를 예측하기 위해 두개의 잘 알려진 표준문제를 통하여 수행되었다. 본 연구에서 수반해의 계산방법은 물리적 수반해 및 정방정식의 고유치를 필요로 하지 않는다. 계산결과들은 본 논문에서 계산된 수반해가 AFEN방법의 정화한 수학적 수반해임을 보여준다.

• 대한기계학회논문집A
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• 제41권1호
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• pp.31-40
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• 2017

1990년대 중반에 개발된 절대절점좌표는 탄성체 동역학 해석에 활용되고 있다. 운동방정식을 유도하는 과정에서 변위장을 이루는 다항식의 차수가 증가하면 필연적으로 자유도가 증가하게 되고, 이는 해석 시간의 증가로 이어진다. 따라서 본 연구에서는 차원 운동방정식을 무차원 운동방정식으로 전환함으로써 해석 시간을 단축시키고자 하였다. 위치 벡터를 이루는 형상 함수는 무차원으로, 절점 좌표는 길이 차원으로 정리한 후 무차원화하는 변수를 통해 무차원 질량행렬, 무차원 선형 강성행렬 및 무차원 보존력을 유도하였다. 무차원 운동방정식의 검증과 효율성은 정적 처짐에 대한 정해가 존재하는 외팔보 및 단진자 예제를 통해 제시하였다.

• 호남수학학술지
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• 제43권3호
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• pp.561-570
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• 2021

In this paper, applying the bifurcation method and topological analysis, we investigate the global structures of solutions for one-dimensional Minkowski-curvature problems under certain behavior of nonlinear term near zero.

• 한국가스학회지
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• 제22권3호
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• pp.65-73
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• 2018

석탄층 메탄가스는 압력에 따라 비선형적인 탈착곡선을 보이므로 이를 고려하여 적절한 생산시스템이 구성되어야 한다. 석탄층 메탄가스 생산설비의 용량 및 규격은 시스템의 경계조건인 탄층 내 가스 유량과 압력조건에 의해 결정되며 이러한 특성을 분석하는 것은 가스 생산 증진을 위해 필수적이다. 본 연구를 위해 대표적인 미국 CBM 상용가스전인 San Juan 지역의 저류전산 모델을 구성하여 가스 유입방정식을 산출하였고, 이를 전체 생산시설의 경계조건으로 활용하였다. 또한 생산시설 내 가스 유량에 따른 압력감소의 영향을 분석하기 위해 생산설비 유동 분석시뮬레이터를 이용하여 노달분석을 수행하여 생산시설의 적정 규격 및 운영조건을 결정하였다. 이를 통해 석탄층 메탄가스 가스전의 최적 수송, 생산 및 포집시스템 설계 기준을 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제5권1호
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• pp.20-27
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• 1981

The alignment of propulsion shaft systems by the fair curve method has been developed over the past twenty years and in recent years its basic problems have been almost solved. At the present time, studies on introducing actual conditions are being undertaken. In a fair curve alignment, its aim is to achieve a stable shaft system which will be relatively insensitive to misalignment or the influence of external factors such as thermal variations due to the sunshine, speed change, etc. The key point of fair curve alignment is the calculations of reactions in the straight support and reaction influence numbers. The present authors have developed those calculating method by the matrix method of the three-moment theorem. The fair curve alignment is based on the analysis of propulsion shaft system which is assumed as a continous beam on multiple support points. The propeller shaft is divided into several elements. For each element, the nodal point equation is derived by the three-moment theorem. Reaction of supporting points of straight shaft and reaction influence numbers are calculated by the matrix calculation of each nodal point equation. It has been found that results of calculation for the model shaft agree well with those of experiment which had been measured by the strain gauge method. Results of calculation for the actual propulsion shafting of the steam turbine had been compared also with those of Det norske Vertas.

• 대한조선학회논문집
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• 제47권1호
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• pp.47-57
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• 2010

This study analyzes the dynamic response of a floating crane with a cargo considering an elastic boom to evaluate(or for evaluation of) its flexibility effect on their dynamic response. Flexible multibody system dynamics is applied in order to establish a dynamic equation of motion of the multibody system, which consists of flexible and rigid bodies. In addition, a floating reference frame and nodal coordinates are used to model the boom as a flexible body. The study also simulates the coupled surge, pitch, and heave motions of the floating crane carrying the cargo with three degrees of freedom by numerically solving the equation. Finally, the simulation results of the elastic and rigid booms are comparatively analyzed and the effects of the flexible boom are discussed.