• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.540-545
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• 2000

This paper presents the exact dynamic element for composite Timoshenko beam, which is inherently subject both to bending and torsional vibration. The coupling effect between bending and torsional vibrations is rigorouly considered in the derivation of the exact dynamic element. Two examples are provided to validate and illustrate the proposed exact dynamic element matrix for composite Timoshenko beam.

• 대한소아치과학회지
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• 제23권3호
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• pp.680-687
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• 1996

Surgical removal of impacted mesiodens can be performed easily when exact position of mesiodens is identified. This case report is argued about methodological approach of exact antero-posterior postioning of mesiodens using conventional cross-sectional occlusal film and periapical film. The author concludes, 1. Among various methods of positioning mesiodens, exact position of mesiodens can be determined with occlusal film and periapical film. 2. On operation, exact antero-posterior position of mesiodens can be determined with comparing occlusal images of adjacent teeth and anatomic structure to real ones. 3. It is important that exact removal course of mesiodens has to be determined in addition to exact determination of one's position, and that it has to be determined in regard to position, morphological basis, direction of impacted pattern of mesiodens and adjacent anatomic structure. 4. In 2 cases presented, both are mesiodens of inverted conical type, and impacted direction are class I and III respectively according to classification author suggested, and surgery can be perfomed with ease by different approach directions.

• ETRI Journal
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• 제43권3호
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• pp.483-510
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• 2021

In computational biology, desired patterns are searched in large text databases, and an exact match is preferable. Classical benchmark algorithms obtain competent solutions for pattern matching in O (N) time, whereas quantum algorithm design is based on Grover's method, which completes the search in $O(\sqrt{N})$ time. This paper briefly explains existing quantum algorithms and defines their processing limitations. Our initial work overcomes existing algorithmic constraints by proposing the quantum-based combined exact (QBCE) algorithm for the pattern-matching problem to process exact patterns. Next, quantum random access memory (QRAM) processing is discussed, and based on it, we propose the QRAM processing-based exact (QPBE) pattern-matching algorithm. We show that to find all t occurrences of a pattern, the best case time complexities of the QBCE and QPBE algorithms are $O(\sqrt{t})$ and $O(\sqrt{N})$, and the exceptional worst case is bounded by O (t) and O (N). Thus, the proposed quantum algorithms achieve computational speedup. Our work is proved mathematically and validated with simulation, and complexity analysis demonstrates that our quantum algorithms are better than existing pattern-matching methods.

• Steel and Composite Structures
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• 제28권5호
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• pp.589-606
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• 2018

The previous studies reflected the significant effect of neutral-axis position and coupling of in-plane and out-of-plane displacements on behavior of functionally graded (FG) nanobeams. In thin FG beam, this coupling can be eliminated by a proper choice of the reference axis. In shear deformable FG nanobeam, not only this coupling can't be eliminated but also the position of neutral-axis is dependent on through-thickness distribution of shear strain. For the first time, in this paper it is avoided to guess a shear strain shape function and the exact shape function and consequently the exact position of neutral axis for arbitrary gradation of higher order nanobeam are obtained. This paper presents new methodology based on differential transform and collocation methods to solve coupled partial differential equations of motion without any simplifications. Using exact position of neutral axis and higher order beam kinematics as well as satisfying equilibrium equations and traction-free conditions without shear correction factor requirement yields to better results in comparison to the previously published results in literature. The classical rule of mixture and Mori-Tanaka homogenization scheme are considered. The Eringen's nonlocal continuum theory is applied to capture the small scale effects. For the first time, the dependency of exact position of neutral axis on length to thickness ratio is investigated. The effects of small scale, length to thickness ratio, Poisson's ratio, inhomogeneity of materials and various end conditions on vibration and buckling of local and nonlocal FG beams are investigated. Moreover, the effect of axial load on natural frequencies of the first modes is examined. After degeneration of the governing equations, the exact new formulas for homogeneous nanobeams are computed.

• 한국의학물리학회지:의학물리
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• 제27권2호
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• pp.79-85
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• 2016

본 연구는 방사선치료에서 방사선 선량전달의 정확도를 높이기 위해 두 종류의 치료테이블 6D robotic couch (BrainLab, Feldkirchen, Germany)와 Standard exact couch (Varian Exact couch$^{TM}$, Varian Medical Systems, Milpitas, CA, USA)를 이용하여 Rail의 위상(In-Out)에 따른 상대선량을 측정하여, 선량감쇠율을 계산하였다. 치료테이블을 투과하는 조사에너지의 조사각 $0^{\circ}$에서 $360^{\circ}$까지의 상대 선량을 각각 측정하였으며, 조사각이 $0^{\circ}$일 때 측정된 선량을 기준으로 하여 $5^{\circ}$ 간격으로 선량의 변화를 측정하고 선량 감쇠율을 계산하였다. Standard exact couch의 광자선 에너지는 6 MV와 10 MV를 사용하였으며 치료테이블의 Rail 위상(In position, Out position)에 따른 상대 선량을 측정하였다. 6D robotic couch는 6 MV와 15 MV의 광자선 에너지를 사용하였다. Standard exact couch의 광자선의 최대 선량차이는 Rail In position에서 6 MV ($175^{\circ}$), 10 MV ($175^{\circ}$)일 때, 선량차이는 각각 16.53%, 12.42%, Out position에서 6 MV ($225^{\circ}$), 10 MV ($225^{\circ}$)일 때, 선량차이는 각각 15.15%, 9.96%였다. 6D robotic couch에서는 6 MV ($130^{\circ}$)와 15 MV ($130^{\circ}$)일 때, 선량차이는 각각 6.82%, 4.92%였다. 본 연구를 통해, 치료테이블의 종류에 따른 선량 감쇠율은 6D robotic couch가 Standard exact couch보다 6 MV에서 조사각 $180^{\circ}$ 기준 약 1% 더 발생함을 확인하였고, Stnadard exact couch인 경우, Sliding rail의 위상(In position, Out position)에 따라 선량 감쇠가 급격히 변화하는 것을 확인하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제24권1호
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• pp.21-24
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• 1985

• 대한기계학회논문집A
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• 제20권6호
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• pp.1773-1783
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• 1996

Finite element method(FEM) is one of the most popularly used method analyzing the dynamic behaviors of structures. But unless number of finite elements is large enough, the results from FEM some what different from exact analytical solutions, especially at high frequency range. On the other hand, as the spectral analysis method(SAM) deals directly with the governing equations of a structure, the results from this melthod cannot but be exact regardless of any frequency range. However, the SAM can be applied only to the case where a structure is subjected to the concentrated loads, despite a structure could be unddergone distributed loads more generally. In this paper, therefore, new spectral analysis algorithm is introduced through the spectral element method(SEM), so that it can be applied to anlystructures whether they are subjected to the concentrated loads or to the distributed loads. The results from this new SEM are compared with both the results from FEM and the exact analytical solutions. As expected, the results from new SEM algorithm are found to be almost identical to the exact analytical solutions while those from FEM are not agreed well with the exact analytical solutions as the mode number increases.

• 한국정밀공학회지
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• 제18권8호
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• pp.87-95
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• 2001

Although asymmetric beams are widely used in industry, few research results are available on the dynamic modeling and analysis of structure including asymmetric beams. Asymmetric beams cause complicated vibration phenomena due to the inherent bending-torsion coupled vibration. In this paper, an exact dynamic element matrix for the bending-torsion coupled vibration of asymmetric beam is derived. The application of the derived exact dynamic element matrix is demonstrated by some illustrative examples wherein the natural frequencies by the proposed modeling method are compared with those available in the literature. Another numerical example is also illustrated which deals with a general beam with joints. The numerical study shows that the exact dynamic element model is useful for the dynamic analysis of asymmetric bending-torsion coupled beams.

• Structural Engineering and Mechanics
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• 제35권2호
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• pp.205-215
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• 2010

Recently, earthquake proof technology has been widely applied to both new and existing structures and bridges. The analysis of bridge systems equipped with structural control devices, which possess large degrees of freedom and nonlinear characteristics, is a result in time-consuming task. Therefore, a piecewise exact solution is proposed in this study to simplify the seismic mitigation analysis process for bridge systems equipped with sliding-type isolators. In this study, the simplified system having two degrees of freedom, to reasonably represent the large number of degrees of freedom of a bridge, and is modeled to obtain a piecewise exact solution for system responses during earthquakes. Simultaneously, we used the nonlinear finite element computer program to analyze the bridge responses and verify the accuracy of the proposed piecewise exact solution for bridge systems equipped with sliding-type isolators. The conclusions derived by comparing the results obtained from the piecewise exact solution and nonlinear finite element analysis reveal that the proposed solution not only simplifies the calculation process but also provides highly accurate seismic responses of isolated bridges under earthquakes.

• Steel and Composite Structures
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• 제44권4호
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• pp.531-543
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• 2022

An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eigenfrequencies obtained by this method is significantly improved, especially for higher order modes, compared to the existing methods where the rotary angles of both sub-beams are assumed to be equal irrespective of the differences in the shear stiffness of each sub-beam. Furthermore, the solutions obtained by the proposed method are exact owing to no introduction of approximated displacement and force fields in the derivation. In addition, an exact analytical solution for the case of simply supported is obtained. Based on this, an approximate expression for the fundamental frequency of continuous partial-interaction composite beams is also proposed, which is useful for practical engineering applications. Finally, the practicability and effectiveness of the proposed method and the approximate expression are explored using numerical and experimental examples; The influence factors including the interfacial interaction, shear modulus ratio, span-to-depth ratio, and side-to-main span length ratio on the eigenfrequencies are presented and discussed in detail.