• 제목/요약/키워드: principle of virtual work

검색결과 203건 처리시간 0.031초

가상세계의 재미노동과 사용자 정체성 (Fun Labor and User Identity of Virtual Worlds)

  • 류철균;신새미
    • 한국콘텐츠학회논문지
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    • 제7권8호
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    • pp.182-190
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    • 2007
  • 가상세계란 전자적 커뮤니케이션에 의해 네트워크화된 3차원 컴퓨터 그래픽 기반의 인터랙티브 환경을 말한다. 오늘날 구현된 가상세계는 기존의 매체에서는 볼 수 없었던 장시간의 몰입을 가능하게 했고, 현실의 노동에 필적할 만큼 힘들고 지루한 장시간의 플레이는 일과 놀이의 경계를 무화시키며 재미노동의 개념을 탄생시켰다. 이러한 재미노동을 '노동을 자연에 가함으로써 자연이 부여한 물리적 한계를 극복하고 자연을 자신에게 더 고유한 존재로 만드는' 인간의 본질로서의 노동으로 긍정한다면, 정보사회에서의 구조적 실업 문제를 해결할 수 있는 획기적인 거대 서비스 분야 중 하나라고 조심스럽게 가정할 수 있다. 또한 재미노동은 돈과 시간과 관심을 지불한 만큼 의미 있는 경험을 하기 원하는 사용자들의 지각 능력과 행위주체성에 부합하는 새로운 형태의 노동일 수 있다. 이러한 현상은 다양한 가상세계를 편력하는 사이버 산책자로서 정의되었던 기존의 사용자 정체성 개념에 반론을 제기하면서, 가상세계의 사용자들은 오히려 하나의 가상세계에 오래 머물며 지속적이고 발전적으로 재미노동을 행하는 존재, 즉 주민의 정체성을 형성하고 있음을 나타낸다. 이렇게 가상세계의 사용자들이 주민성을 형성함에 따라 단체 행동권과 시민참여의 새로운 양식이 확산되어 가고 있으며, 이러한 현상이 사회적으로 미치는 영향을 관찰하는 일이 매우 중요해질 것이다.

Non-stationary vibration and super-harmonic resonances of nonlinear viscoelastic nano-resonators

  • Ajri, Masoud;Rastgoo, Abbas;Fakhrabadi, Mir Masoud Seyyed
    • Structural Engineering and Mechanics
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    • 제70권5호
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    • pp.623-637
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    • 2019
  • This paper analyzes the non-stationary vibration and super-harmonic resonances in nonlinear dynamic motion of viscoelastic nano-resonators. For this purpose, a new coupled size-dependent model is developed for a plate-shape nano-resonator made of nonlinear viscoelastic material based on modified coupled stress theory. The virtual work induced by viscous forces obtained in the framework of the Leaderman integral for the size-independent and size-dependent stress tensors. With incorporating the size-dependent potential energy, kinetic energy, and an external excitation force work based on Hamilton's principle, the viscous work equation is balanced. The resulting size-dependent viscoelastically coupled equations are solved using the expansion theory, Galerkin method and the fourth-order Runge-Kutta technique. The Hilbert-Huang transform is performed to examine the effects of the viscoelastic parameter and initial excitation values on the nanosystem free vibration. Furthermore, the secondary resonance due to the super-harmonic motions are examined in the form of frequency response, force response, Poincare map, phase portrait and fast Fourier transforms. The results show that the vibration of viscoelastic nanosystem is non-stationary at higher excitation values unlike the elastic ones. In addition, ignoring the small-size effects shifts the secondary resonance, significantly.

Bending behavior of laminated composite plates using the refined four-variable theory and the finite element method

  • Bouazza, Mokhtar;Becheri, Tawfiq;Boucheta, Abderrahmane;Benseddiq, Noureddine
    • Earthquakes and Structures
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    • 제17권3호
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    • pp.257-270
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    • 2019
  • The purpose of this work is to analyze the bending behavior of laminated composite plates using the refined fourvariable theory and the finite element method approach using an ANSYS 12 computational code. The analytical model is based on the multilayer plate theory of shear deformation of the nth-order proposed by Xiang et al 2011 using the theory principle developed by Shimpi and Patel 2006. Unlike other theories, the number of unknown functions in the present theory is only four, while five or more in the case of other theories of shear deformation. The formulation of the present theory is based on the principle of virtual works, it has a strong similarity with the classical theory of plates in many aspects, it does not require shear correction factor and gives a parabolic description of the shear stress across the thickness while filling the condition of zero shear stress on the free edges. The analysis is validated by comparing results with those in the literature.

이동 하중의 질량효과를 고려한 보의 동적응답 (Dynamic Response of a Beam Including the Mass Effect of the Moving Loads)

  • 최교준;김용철
    • 대한기계학회논문집
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    • 제15권1호
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    • pp.61-68
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    • 1991
  • 본 연구에서는 스프링힌지, 클램프, 단순지지, 탄성지반, 다수의 병진 및 회 전스프링 그리고 중간지지점의 조합으로 구성되어 있는 보에 대하여 우선 Hamilton원 리에 의하여 정확한 보의 특성방정식을 유도하고 모든 경계조건을 만족하는 직교다항 식을 구한 후, 스프링, 댐퍼로 구성된 여러개의 질량이 일정한 속도로 이동할 경우에 대하여 Galerkin방법과 수치적분 방법을 사용하여 동적응답을 구하였다. 또한 구속 조건 및 경계조건이 변함에 따라 동적응답에 미치는 영향을 연구하였다.

전류가 관통하는 원통형 자성체에 미치는 전자기력식의 통일성에 대한 고찰 (An Observation of Unified Force Expression in The Cylindrical Magnetic Material with a Vertical Current Running Through Its Center)

  • 최홍순
    • 한국자기학회지
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    • 제21권5호
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    • pp.174-179
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    • 2011
  • 지금까지 자성체에 미치는 전자기력을 계산하기 위해서는, 맥스웰 응력법, 가상변위법, 자하법, 자화전류법등이 널리 사용되어 왔으며, 이들은 자성체 덩어리 전체에 미치는 전자기력을 계산하는 데 있어 모두 정당한 결과를 가져온다고 보고 있다. 그러나 전자기력 밀도식의 완전한 형태에 대해서는 아직 까지도 논란이 있으며, 각 방법에 의한 표면 전자기력 밀도는 식과 수치해석 모두 다른 결과를 보인다. 본 연구는 전자기력밀도를 체적력으로 국한하여 가상공극법을 적용하였을 때, 모두 같은 형태의 식으로 도출이 됨을 해석식이 존재하는 모델을 통하여 보여준다. 즉, 가상공극 개념을 적용할 경우, 체적력 전자기력 밀도식의 통일 가능성을 보여 주는 것이다.

회전(回轉) SHELL의 좌굴(挫屈) 해석(解析) (The Buckling Analysis of Shells of Revolution)

  • 임상전;장창두;윤장호
    • 대한조선학회지
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    • 제21권2호
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    • pp.19-27
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    • 1984
  • An extension of the finite element method to the stability analysis of shells of revolution under static axisymmetric loading is presented in this paper. A systematic procedure for the formulation of the problem is based upon the principle of virtual work. This procedure results in an eigenvalue problem. For solution, the shell of revolution is discretized into a series of conical frusta. The buckling mode in the circumferential direction is assumed, this assumption makes the problem economical for the computing time. The present method is applied to a number of shells of revolution, under axial compression or lateral pressure, and comparision are made with other theoretical results. The results show good agreement each other. The effects of aspect ratio, boundary conditions and buckling modes on the buckling strength of shells of revolution are studied. Also the optimum shape of cylindrical shell under uniform axial compression is obtained from the view point of structural stability.

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Bending analysis of thick functionally graded piezoelectric rectangular plates using higher-order shear and normal deformable plate theory

  • Dehsaraji, M. Lori;Saidi, A.R.;Mohammadi, M.
    • Structural Engineering and Mechanics
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    • 제73권3호
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    • pp.259-269
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    • 2020
  • In this paper, bending-stretching analysis of thick functionally graded piezoelectric rectangular plates is studied using the higher-order shear and normal deformable plate theory. On the basis of this theory, Legendre polynomials are used for approximating the components of displacement field. Also, the effects of both normal and shear deformations are encountered in the theory. The governing equations are derived using the principle of virtual work and variational approach. It is assumed that plate is made of piezoelectric materials with functionally graded distribution of material properties. Hence, exponential function is used to modify mechanical and electrical properties through the thickness of the plate. Finally, the effect of material properties, electrical boundary conditions and dimensions are investigated on the static response of plate. Also, it is shown that results of the presented model are close to the three dimensional elasticity solutions.

Detection of a concentrated damage in a parabolic arch by measured static displacements

  • Greco, Annalisa;Pau, Annamaria
    • Structural Engineering and Mechanics
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    • 제39권6호
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    • pp.751-765
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    • 2011
  • The present paper deals with the identification of a concentrated damage in an elastic parabolic arch through the minimization of an objective function which measures the differences between numerical and experimental values of static displacements. The damage consists in a notch that reduces the height of the cross section at a given abscissa and therefore causes a variation in the flexural stiffness of the structure. The analytical values of static displacements due to applied loads are calculated by means of the principle of virtual work for both the undamaged and damaged arch. First, pseudo-experimental data are used to study the inverse problem and investigate whether a unique solution can occur or not. Various damage intensities are considered to assess the reliability of the identification procedure. Then, the identification procedure is applied to an experimental case, where displacements are measured on a prototype arch. The identified values of damage parameters, i.e., location and intensity, are compared to those obtained by means of a dynamic identification technique performed on the same structure.

Dynamic responses of a riser under combined excitation of internal waves and background currents

  • Lou, Min;Yu, Chenglong
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제6권3호
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    • pp.685-699
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    • 2014
  • In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-${\beta}$ method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode.

회전하는 환상 디스크의 면내 고유진동 해석 (In-Plane Natural Vibration Analysis of a Rotating Annular Disk)

  • 김창부;송승관
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2008년도 추계학술대회 논문집
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    • pp.1379-1388
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    • 2008
  • In this paper, we present the equations of motion by which the natural vibration of a rotating annular disk can be accurately analyzed. These equations are derived from the theory of finite deformation and the principle of virtual work. The radial displacements of annular disk which is rotating at constant angular velocity are determined by non-linear equations formulated using 1-dimensional finite elements in radial direction. The equations of the in-plane vibrations at disturbed state are also formulated using 1-dimensional finite elements in radial direction along the number of nodal diameters. They are expressed as in functions of the radial displacements at the steady state and the disturbed displacements about the steady state. In-plane static deformation modes of the annular disk are used as the interpolation functions of 1-dimensional finite elements in radial direction. The natural vibrations of an annular disk with different boundary conditions are analyzed by using the presented model and the 3-dimensional finite element model to verify accuracy of the presented equations of motion. Its results are compared and discussed.

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