• Title/Summary/Keyword: Matrix structures

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Studies of the $TiO_2-Si$ Interface Bombarded by $Ar^+$ Ion Beam

  • Zhang, J.;Huang, N.K.;Lu, T.C.;Zeng, L.;Din, T.;Chen, Y.K.
    • Journal of the Korean Vacuum Society
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    • v.12 no.S1
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    • pp.63-66
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    • 2003
  • It is experimentally shown that a $TiO_2$ film on Si(111) substrate was prepared by using the technique of D.C. reaction sputter deposition with $Ar^{+}$ ion beam bombardment, and a layer-like structure was observed from the depth profile of the interface between $TiO_2$ film and Si substrate with Scanning Electron Microscopy and Electron Probe. It was also surprisingly discovered that Ti atoms could be detected at about 9 $\mu$m depth. The $TiO_2$-Si interface bombarded by $Ar^{+}$ ion beams revealed multi-layer structures, a mechanism might be caused by defect diffusion, impurity and matrix relocation. Multi-relocations of impurity and matrix atoms were as a result of profile broadening of the $TiO_2$-Si interface, and the spread due to matrix relocation in this system is shown to exceed much more the spread due to impurity relocation.

Analysis of Practical Dynamic Force of Structure with Inverse Problem (역문제에 의한 구조물의 실동하중 해석)

  • 송준혁;노홍길;김홍건;유효선;강희용;양성모
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.13 no.2
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    • pp.75-80
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    • 2004
  • Vehicle structures are composed of many substructure connected to one another by various types of mechanical joints. In vehicle engineering it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. It is difficult to obtain the accurate load history of specified positions because of the errors such as modeling, measurement and etc. In the beginning of design exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic force determination is developed by the combination of the principal stresses of F. E. Analysis and experiment. Least square pseudo inverse matrix is adopted to obtain in inverse matrix of analyzed stresses matrix. The error minimization method utilizes the inaccurate measured error and the shifting error that the whole data is stiffed over real data. The least square criterion is adopted to avoid these non. Finally, to verify the proposed procedure, a bus is analyzed. This measurement and prediction technology can be extended to the structural modification of any geometric shape in complex structure.

Dynamic Stress Analysis of joint by Practical Dynamic Load History (실하중 이력에 의한 조인트의 동적강도해석)

  • ;;;Akira Simamoto
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.5
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    • pp.118-123
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    • 2001
  • Most structures of automobile are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic farces for the evaluations of fatigue life and stress concentration exactly. It is rarely obtained the accurate load history of specified positions because of the errors such as modeling, measurement, and etc. In the beginning of design, exact load data are actually necessary for the fatigue strength and life analysis to minimize the cost and time of designing. In this paper, the procedure of practical dynamic load determination is developed by the combination of the principal stresses of F.E. analysis and experiment. Inverse problem and least square pseudo inverse matrix are adopted to obtain an inverse matrix of analyzed stresses matrix. Pseudo-Practical dynamic load was calculated for Lab. Test of sub-structure. GUI program(PLODAS) was developed for whole of above procedure. This proposed method could be extended to any geometric shape of structure.

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Exact natural frequencies of structures consisting of two-part beam-mass systems

  • Su, H.;Banerjee, J.R.
    • Structural Engineering and Mechanics
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    • v.19 no.5
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    • pp.551-566
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    • 2005
  • Using two different, but related approaches, an exact dynamic stiffness matrix for a two-part beam-mass system is developed from the free vibration theory of a Bernoulli-Euler beam. The first approach is based on matrix transformation while the second one is a direct approach in which the kinematical conditions at the interfaces of the two-part beam-mass system are satisfied. Both procedures allow an exact free vibration analysis of structures such as a plane or a space frame, consisting of one or more two-part beam-mass systems. The two-part beam-mass system described in this paper is essentially a structural member consisting of two different beam segments between which there is a rigid mass element that may have rotatory inertia. Numerical checks to show that the two methods generate identical dynamic stiffness matrices were performed for a wide range of frequency values. Once the dynamic stiffness matrix is obtained using any of the two methods, the Wittrick-Williams algorithm is applied to compute the natural frequencies of some frameworks consisting of two-part beam-mass systems. Numerical results are discussed and the paper concludes with some remarks.

Identification of Stiffness and Damping Matrix of Building Structures using Modal Characteristics (모드 특성을 이용한 건축 구조물의 강성 및 감쇠 행렬식별)

  • 강경수
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.2
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    • pp.45-53
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    • 2004
  • In this paper, the stiffness and damping matrix are experimentally constructed using the structural modal information on frequencies, damping ratio and modal vectors, which are obtained by shaking table tests. Free vibration, harmonic and white noise vibration tests are performed. The acceleration of the shaking table was used as the input signal, and the corresponding accelerations of each floor were measured as output signals. The characteristics and limitations of modal information from each test are compared. The results of this study would be a basic resource of the analytical and experimental studies on the system identification of structures.

Covariance-driven wavelet technique for structural damage assessment

  • Sun, Z.;Chang, C.C.
    • Smart Structures and Systems
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    • v.2 no.2
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    • pp.127-140
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    • 2006
  • In this study, a wavelet-based covariance-driven system identification technique is proposed for damage assessment of structures under ambient excitation. Assuming the ambient excitation to be a white-noise process, the covariance computation is shown to be able to separate the effect of random excitation from the response measurement. Wavelet transform (WT) is then used to convert the covariance response in the time domain to the WT magnitude plot in the time-scale plane. The wavelet coefficients along the curves where energy concentrated are extracted and used to estimate the modal properties of the structure. These modal property estimations lead to the calculation of the stiffness matrix when either the spectral density of the random loading or the mass matrix is given. The predicted stiffness matrix hence provides a direct assessment on the possible location and severity of damage which results in stiffness alteration. To demonstrate the proposed wavelet-based damage assessment technique, a numerical example on a 3 degree-of-freedom (DOF) system and an experimental study on a three-story building model, which are all under a broad-band excitation, are presented. Both numerical and experimental results illustrate that the proposed technique can provide an accurate assessment on the damage location. It is however noted that the assessment of damage severity is not as accurate, which might be due to the errors associated with the mode shape estimations as well as the assumption of proportional damping adopted in the formulation.

Hybrid Type Vibration Power Flow Analysis Method Using SEA Parameters

  • Park, Young-Ho;Hong, Suk-Yoon
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.4E
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    • pp.164-169
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    • 2002
  • This paper proposes a hybrid method for vibration analysis in the medium to high frequency ranges using Power Flow Analysis (PFA) algorithm and Statistical Energy Analysis (SEA) coupling concepts. The main part of the developed method is the application of coupling loss factor (CLF) suggested in SEA to the power transmission, reflection coefficients in PI' A boundary conditions. The developed hybrid method shows very promising results with regard to the applications for the various damping loss factors in wide frequency ranges. And also this paper presents the applied results of Power Flow Finite Element Method (PFFEM) by forming the new joint element matrix with CLF to analyze the various plate structures in shape. The analytical results of automobile, complex plate structures show good agreement with those of PFFEM using the PFA coefficients.

Advanced Geometrically Nonlinear FE Analysis of PSC Shell Structures (프리스트레스트 콘크리트 첼 구조물의 개선된 기하비선형 유한요소해석)

  • Oh Byung Hwan
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.195-200
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    • 2001
  • Numerical procedures for the geometrically nonlinear finite element analysis of prestressed concrete shell structures under tendon-induced nonconservative loads have been presented. The equivalent load approach is employed to realize the effect of prestressing tendon. In this study, the tendon-induced nonconservative loads are rigorously formulated into the load correction stiffness matrix(LCSM) taking the characteristics of Present shell element into account. Also, improved nonlinear formulations of a shell element are used by including second order rotations in the displacement field. Numerical example shows that beneficial effect on the convergence behavior can be obtained by the realistic evaluation of tangent stiffness matrix according to the present approaches.

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Dynamic Instability of Lattice-Dome Structures by Lyapunov Concept

  • Han, Sang-Eul;Hou, Xiao-Wu
    • Architectural research
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    • v.10 no.1
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    • pp.25-32
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    • 2008
  • Stability is a very important part which we must consider in structural design. In this paper, we take advantage of finite element method to study parametrical instability of lattice dome structures, which is subjected to harmonically pulsating load. We consider elastic stiffness and geometrical stiffness simultaneously during the calculation of stiffness matrix, and adopt consistent mass matrix to make the solution more correct. In order to obtain instability regions, we represent displacements and accelerations in dynamic equation by trigonometric series expansions, and then obtain Hill's infinite determinants. After first order approximation, we can get first and second order dynamic instability regions eventually. Finally, we take 24-bar star dome and 90-bar lamella dome as examples to investigate dynamic instability phenomena.

JORDAN HIGHER DERIVATIONS ON TRIVIAL EXTENSION ALGEBRAS

  • Vishki, Hamid Reza Ebrahimi;Mirzavaziri, Madjid;Moafian, Fahimeh
    • Communications of the Korean Mathematical Society
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    • v.31 no.2
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    • pp.247-259
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    • 2016
  • We first give the constructions of (Jordan) higher derivations on a trivial extension algebra and then we provide some sufficient conditions under which a Jordan higher derivation on a trivial extension algebra is a higher derivation. We then proceed to the trivial generalized matrix algebras as a special trivial extension algebra. As an application we characterize the construction of Jordan higher derivations on a triangular algebra. We also provide some illuminating examples of Jordan higher derivations on certain trivial extension algebras which are not higher derivations.