• Steel and Composite Structures
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• 제34권2호
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• pp.289-297
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• 2020

In the present research post-buckling of a cut out plate reinforced through carbon nanotubes (CNTs) resting on an elastic foundation is studied. Material characteristics of CNTs are hypothesized to be altered within thickness orientation which are calculated according to Mori-Tanaka model. For modeling the system mathematically, first order shear deformation theory (FSDT) is applied and using energy procedure, the governing equations can be derived. With respect to Rayleigh-Ritz procedure as well as Newton-Raphson iterative scheme, the motion equations are solved and therefore, post-buckling behavior of structure will be tracked. Diverse parameters as well as their reactions on post-buckling paths focusing cut out measurement, CNT's volume fraction and agglomeration, dimension of plate and an elastic foundation are investigated. It is revealed that presence of a square cut out can affect negatively post-buckling behavior of structure. Moreover, adding nanocompsits in the matrix leads to enhancement of post-buckling response of system.

• Advances in nano research
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• 제7권6호
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• pp.405-417
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• 2019

This research is devoted to study post-buckling analysis of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) micro plate with cut out subjected to magnetic field and resting on elastic medium. The basic formulation of plate is based on first order shear deformation theory (FSDT) and the material properties of FG-CNTRCs are presumed to be changed through the thickness direction, and are assumed based on rule of mixture; moreover, nonlocal Eringen's theory is applied to consider the size-dependent effect. It is considered that the system is embedded in elastic medium and subjected to longitudinal magnetic field. Energy approach, domain decomposition and Rayleigh-Ritz methods in conjunction with Newton-Raphson iterative technique are employed to trace the post-buckling paths of FG-CNTRC micro cut out plate. The influence of some important parameters such as small scale effect, cut out dimension, different types of FG distributions of CNTs, volume fraction of CNTs, aspect ratio of plate, magnitude of magnetic field, elastic medium and biaxial load on the post-buckling behavior of system are calculated. With respect to results, it is concluded that the aspect ratio and length of square cut out have negative effect on post-buckling response of micro composite plate. Furthermore, existence of CNTs in system causes improvement in the post-buckling behavior of plate and different distributions of CNTs in plate have diverse response. Meanwhile, nonlocal parameter and biaxial compression load on the plate has negative effect on post-buckling response. In addition, imposing magnetic field increases the post-buckling load of the microstructure.

• Computers and Concrete
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• 제13권3호
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• pp.343-359
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• 2014

In this work a numerical method to simulate the response of reinforced concrete structures subject to cyclically imposed displacements is proposed. The method consists of a combination of a displacement and load controlled version of the Newton-Raphson iterative technique, used for the loading and the unloading part of the cycles respectively. The whole procedure is combined with a relatively simple concrete model whose only material parameter is its uniaxial compressive strength. The proposed methodology may realistically simulate, in an easy way, the physical process of any experimentally tested RC structure under imposed displacements cycles. The efficiency of the approach is demonstrated through a series of analyses of experimentally tested specimens reported in the literature.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.906-909
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• 2005

In this study, the dynamic flying characteristics of the worn head sliders are investigated theoretically due to the change in head geometry caused by head and disk contact. The film shapes can be approximated as taper- truncated cycloidal-flat film. Two-dimensional time dependent modified Reynolds equation included molecular slip effect are formulated with neglected the roughness effect. The motion of head slider was assumed to have two degree of freedom in this work. Finite difference approximation with Newton Raphson iterative technique and the fourth order Runge-Kutta method were implemented to obtain the transient response of the slider head with various change in head geometry numerically and compared with the transient response of the IBM3380 type head slider. The simulation results show the film shape has affects significantly on the static and dynamic characteristic of slider head in magnetic storage systems.

• 전기의세계
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• 제29권3호
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• pp.193-200
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• 1980

A new algorithm for power system stability calculations is developed which considers the nonlinear state equations of 8 state variables for each generator dynamics, expollential load models in respect to bus voltages for nonlinear loads, network equations expressed in terms of bus-injected current sources, various kinds of generator and transmission line outages, abrupt changes in loads, and operations of various kinds of portective relaying systems such as distance relaying, reclosing load shedding by under-frequency relays. In the algorithm are included efficient and reliable schemes for solving network equations by means of the Newton-Raphson iterative method and the Optimally-Ordered Triangular Factorization Technique, and simple procedures for determining fault-point negative and zero sequence impedances for unbalanced line faults. An application of the Optimally-Ordered Triangular Factorization Techniques results in remarkable savings in computing time and memory requirements.

• Structural Engineering and Mechanics
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• 제34권1호
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• pp.97-107
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• 2010

Nonlinear thermoelastic static response characteristics of laminated composite conical panels are studied employing finite element approach based on first-order shear deformation theory and field consistency principle. The nonlinear governing equations, considering moderately large deformation, are solved using Newton-Raphson iterative technique coupled with the adaptive displacement control method to efficiently trace the equilibrium path. The validation of the formulation for mechanical and thermal loading cases is carried out. The present results are found to be in good agreement with those available in the literature. The adaptive displacement control method is found to be capable of handling problems with multiple snapping responses. Detailed parametric study is carried out to highlight the influence of semicone angle, boundary conditions, radius-to-thickness ratio and lamination scheme on the nonlinear thremoelastic response of laminated cylindrical and conical panels.

• Steel and Composite Structures
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• 제32권3호
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• pp.293-304
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• 2019

In the present paper, the element free Galerkin (EFG) method is developed for geometrically nonlinear analysis of deep beams considering small scale effect. To interpret the behavior of structure at the nano scale, the higher-order gradient elasticity nonlocal theory is taken into account. The radial point interpolation method with high order of continuity is used to construct the shape functions. The nonlinear equation of motion is derived using the principle of the minimization of total potential energy based on total Lagrangian approach. The Newmark method with the small time steps is used to solve the time dependent equations. At each time step, the iterative Newton-Raphson technique is applied to minimize the residential forces caused by the nonlinearity of the equations. The effects of nonlocal parameter and aspect ratio on stiffness and dynamic parameters are discussed by numerical examples. This paper furnishes a ground to develop the EFG method for large deformation analysis of structures considering small scale effects.

• 한국연소학회지
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• 제3권1호
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• pp.21-29
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• 1998

Mathematical modeling of combustion characteristics in HVOF thermal spray processes was carried out on the basis of equilibrium chemistry. The main objective of this work was the development of a computation code which allows to determine chemical composition of combustion products, adiabatic flame temperature, thermodynamic and transport properties. The free energy minimization method was employed with the descent Newton-Raphson technique for numerical solution of systems of nonlinear thermochemical equations. Adiabatic flame temperature was calculated by using a Newton#s iterative method incorporating the computation module of chemical composition. The performance of this code was verified by comparing computational results with data obtained by ChemKin code and in the literature. Comparisons between the calculated and measured flame temperatures showed a deviation less than 2%. It was observed that adiabatic flame temperature augments with increase in combustion pressure; the influence was significant in the region of low pressure but becomes weaker and weaker with increase in pressure. Relationships of adiabatic flame temperature, dissociation ratio and combustion pressure were also analyzed.

• 한국재난정보학회 논문집
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• 제16권4호
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• pp.832-841
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• 2020

연구목적: 본 연구에서는 고차전단변형이론을 적용한 등기하해석 방법을 이용하여 기능경사복합재 판의 휨에 의한 역학적 거동을 해석하고자 하였다. 연구방법: 기능경사복합재 판의 역학적 거동을 보다 더 정확하게 해석하기 위해서 전단보정계수를 도입할 필요가 없는 기하학적 비선형을 고려한 고차전단변형이론을 이용하여 휨을 받는 기능경사복합재 판의 평형방정식과 지배방정식을 도출하였으며, 등기하 해석방법에 의한 수정된 Newton-Raphson 반복법을 이용하여 방정식들을 풀었다. 연구결과: 판의 용적비, 길이-두께 비 및 경계조건은 기능경사복합재 판의 휨 거동에 상당한 영향을 미치는 것을 알 수 있었다. 결론: 제안된 등기하해석 방법은 휨을 받는 기능경사복합재 판의 역학적 거동을 해석하는데 있어 정확하고 효과적인 수치해석 방법임을 확인하였다.

• 대한기계학회논문집
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• 제16권12호
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• pp.2298-2305
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• 1992

본 연구에서는 보의 종방향 강성치를 실제보다 훨씬 작은 횡방향 강성치 수준 으로 낮추어 시간 적분을 수행하는 대신, 종방향에 작용하는 힘을 분산시켜서 계산시 종방향 상대 변형을 억제하는 기법을 사용하였다. 또 여러개의 물체가 조인트에서 서로 연결되어 이루어진 다물체 도역학의 해는 운동 방정식과 기구학적 제한조건을 모 두 만족시켜야 하며, 상미분 방정식 해법용 시간 적분을 바로 적용할 수는 없다. 본 논문에서는 참고문헌(13)과 (14)에 소개된 반복계산법 및 계산가속기법에 의하여 Lag- range multiplier를 운동 방정식에서 소거한 후 시간 적분을 수행하는 방법을 사용한 다.