• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1391-1402
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• 2021

The aim of this work is to prepare a neutron noise calculator based on the second order of average current nodal expansion method (ACNEM). Generally, nodal methods have the ability to fulfill the neutronic analysis with adequate precision using coarse meshes as large as a fuel assembly size. But, for the zeroth order of ACNEM, the accuracy of neutronic simulations may not be sufficient when coarse meshes are employed in the reactor core modeling. In this work, the capability of second order ACNEM is extended for solving the neutron diffusion equation in the frequency domain using coarse meshes. For this purpose, two problems are modeled and checked including a slab reactor and 2D BIBLIS PWR. For validating of results, a semi-analytical solution is utilized for 1D test case, and for 2D problem, the results of both forward and adjoint neutron noise calculations are exploited. Numerical results indicate that by increasing the order of method, the errors of frequency dependent coarse mesh solutions are considerably decreased in comparison to the reference. Accordingly, the accuracy of second order ACNEM can be acceptable for the neutron noise calculations by using coarse meshes in the nuclear reactor core.

• 소음진동
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• 제10권3호
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• pp.523-530
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• 2000

In this paper we present an efficient method for finite element vibration analysis of a structure with cyclic symmetry and applied it to calculating the natural vibration characteristics for a blower impeller. Blower impeller having a cyclically symmetric structure is composed of circumferentially repeated substructures., The whole-structure is partitioned into substructures and then finite element vibration analysis is performed for a substructure using transformed equations for each number of nodal diameter which are derived from discrete Fourier transform in consideration of the cyclic symmetry. natural vibration characteristics for three kinds of models which are blower impeller without support ring with small support ring and with large support ring are numerically analyzed and compared. Accuracy and efficiency of the present method are verified by comparison of results of the analysis with substructure and with whole-structure. Also the results of the analysis by cyclic symmetry module(SOL 115) of MSC/NASTRAN are presented and compared.

• 한국정밀공학회지
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• 제17권2호
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• pp.201-210
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• 2000

The large deflection of plate is analyzed by co-rotational formulations using small local displacements and rotating unit vectors on the nodal points. The rotational degrees of the freedom are represent ed by the unit vectors1 In the nodal points, and the equilibrium equations are formulated by using small deflection theories of the plates by assuming that the directions of the unit vectors of the nodal points are known apriori. The translational degrees of freedom are independently solved from the rotational degrees of freedom in the equilibrium equations, and the correct directions of the unit vectors are computed by the iterative scheme by imposing the moment equilibrium constraint. The equilibrium equations and the associated solution procedure are explained, and the verification problems are solved.

• Structural Engineering and Mechanics
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• 제36권1호
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• pp.95-110
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• 2010

Two-dimensional elastic contact problems, including normal, tangential, and rolling contacts, are treated with the finite element method in this study. Stress boundary conditions and kinematic conditions are transformed into multiple point constraints for nodal displacements in the finite element method. Upon imposing these constraints into the finite element system equations, the calculated nodal stresses and nodal displacements satisfy stress and displacement contact conditions exactly. Frictional and frictionless contacts between elastically identical as well as elastically dissimilar materials are treated in this study. The contact lengths, sizes of slip and stick regions, the normal and the shear stresses can be found.

• 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.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.514-519
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• 2006

This paper presents a new nonlinear analysis algorithm which uses the equivalent nodal load for the element stiffness. The equivalent nodal load represents the influence of the stiffness change such as the addition of elements, the deletion of elements, and/or the partial change of element stiffness. The nonlinear analysis of structures using the equivalent load improves the efficiency very much because the inverse of the structural stiffness matrix, which needs a large amount of computation to calculate, is reused in each loading step. In this paper, the concept of nonlinear analysis using the equivalent load for the element stiffness is described and some numerical examples are provided to verify it.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2006년도 춘계 학술발표회 논문집 제3권1호(통권3호)
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• pp.170-174
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• 2006

This paper presents a new nonlinear analysis algorithm which uses the equivalent nodal load for the element stiffness. The equivalent nodal load represents the influence of the stiffness change such as the addition of elements, the deletion of elements, and/or the partial change of element stiffness. The nonlinear analysis of structures using the equivalent load improves the efficiency very much because the inverse of the structural stiffness matrix, which needs a large amount of computation to calculate, is reused in each loading step. In this paper, the concept of nonlinear analysis using the equivalent load for the element stiffness is described and some numerical examples are provided to verify it.

• Journal of Advanced Marine Engineering and Technology
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• 제18권4호
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• pp.69-76
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• 1994

Thermal elasto-plastic analysis of axi-symmetric body by the finite element method is presented in this paper for analyzing the process of upset forming of circular section extruded bar. The example of calculation for upset forming of Nimonic extruded bar is also presented. It is shown that remeshing of quadrilateral finite element is necessary because the very highly distorted element by plastic deformation disturbs the calculation. Calculated values for nodal points in new mesh are obtained from nodal points of old mesh by linear interpolation method. The experimental results are compared with calculated values. The appearance of upsetupset forming obtained by experimental method is very similar to that obtained by calculations. So, it is proved that the thermal elasto-plastic analysis of axi-symmetric body by the finite element method is very useful for finding the optimum upsetting condition.

• 한국자원공학회지
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• 제55권6호
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• pp.635-648
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• 2018

본 연구는 탄성파 탐사 수진기의 특허동향을 분석하였다. 또한 수진기 제조사인 페어필드, 서셀, 와이어리스 사이스믹 등 3개 주요 기업의 탄성파 탐사 수진기 특허동향 및 핵심특허의 기술특징을 분석하여 각 기업의 기술개발 세부분야를 살펴보았다. 탄성파 수진기의 특허동향은 2000년 초 중반 이후로 출원 증가율이 지속적으로 높아지고 있으며 최근 더욱 높은 증가율을 보여 동 분야의 성장세를 확인하였다. 동 기간에 주요기업의 특허 출원증가율은 글로벌 동향보다 높게 나타났으며 특허침해소송 사례를 확인하여 동 분야의 활발한 시장경쟁을 확인하였다. 핵심특허 33건의 기술특징을 분석한 결과 주요기업은 대체로 탄성파 신호감지 분야에 집중하여 특허를 보유하는 것으로 나타났다. 세부기술은 자료획득의 신뢰도 향상, 자료전송 효율 향상, 무선수진기의 운용 시스템 개량기술 분야로 구분되었다. 시장이 성장하고 있는 동 분야의 기술개발 및 제조 관련 신규 진입자는 향후 발생할 수 있는 특허분쟁 또는 중복연구 등을 미연에 방지하기 위하여 주요 기업의 제품 및 특허의 청구항을 면밀하게 분석할 필요가 있겠다.

• 한국해안·해양공학회논문집
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• 제28권2호
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• pp.101-108
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• 2016

해상풍력 발전시설은 국제적인 설계기준조위로 최고천문조위(highest astronomical tide, HAT)와 최저천문조위(lowest astronomical tide, LAT) 기준을 요구하고 있다. 우리나라는 설계기준조위로 약최고고조위(AHHW)와 약최저저조위(ALLW) 기준을 사용하여 왔기 때문에 국제적인 설계기준을 만족하기 위해서는 해상풍력 발전시설 후보 해역인 위도에서의 HAT, LAT 추정이 필요하다. 본 연구에서는 위도에서 가용한 31년 조위자료를 이용하여 HAT, LAT 기준조위를 추정하였으며, 추정에 사용한 자료의 신뢰수준을 검토하기 위하여 장기 태음분조에 해당하는 18.61년 주기의 Nodal 변동 특성 분석을 수행하였다. Nodal 보정을 고려하지 않은 연간 $M_2$, $O_1$, $K_1$ 분조의 진폭변화는 뚜렷한 18.61년 주기를 보여 조화분석 결과가 적절하게 추정된 것으로 파악되고 있는 것으로 파악되었다. 한편 조위자료를 이용하여 추정한 HAT, LAT 신뢰구간의 상한 및 하한으로 최종 추정한 HAT, LAT 조위는 AHHW, ALLW 기준조위에 비하여 각각 +40 cm, -35 cm 정도로 파악되었다.