• Bulletin of the Korean Chemical Society
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• 제35권4호
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• pp.1212-1214
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• 2014

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.583-603
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• 2015

There are so many applications of perforated pates with various penetration patterns. If they are penetrated regularly, it can be represented by solid plate with equivalent material properties, which has a benefit of finite element modelling and reducing computation time for the analysis. Because the equivalent material properties suggested already are not proper to be applicable for the dynamic analysis, it is necessary to extract the equivalent material properties for the dynamic analysis. Therefore, in this study, the equivalent modulus of elasticity are obtained for the perforated plate with a triangular penetration pattern by comparing the natural frequencies of the perforated plate with those of solid plate, which are represented with respect to the ligament efficacy. Using the equivalent material properties suggested, the modal analyses of the partially perforated rectangular plate with a triangular penetration pattern are performed and its applicability is shown by comparing natural frequencies of perforated and homogeneous solid plates from finite element method and analytical method.

• Journal of Mechanical Science and Technology
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• 제14권3호
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• pp.306-313
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• 2000

The homogenization method and the density function method are common approaches to evaluate the equivalent material properties for design cells composed of matter and void. In this research, using a new topology optimization method based on the homogenized material with a penalty factor and the chessboard prevention strategy, we obtain the optimal layout of a structure for the natural frequency of a designated mode. The volume fraction of nodes of each finite element is chosen as the design variable and a total material usage constraint is imposed. In this paper, the subspace method is used to evaluate the eigenvalue and its corresponding eigenvector of the structure for the designated mode and the recursive quadratic programming algorithm, PLBA algorithm, is used to solve the topology optimization problem.

• 대한의용생체공학회:의공학회지
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• 제32권3호
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• pp.251-256
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• 2011

Virtual colonoscopy is favored over conventional colonoscopy because its non-invasive procedure can avoid complications that may happen in a conventional approach and because it can cleanse colon electronically instead of uncomfortable conventional colon cleansing. Electronic Colon Cleansing(ECC) has to deal with not only removing tagged fecal material but also recovering Partial Volume Effect(PVE) due to tagging material. This paper proposes an ECC method restoring inherent natural PVE while previous approaches focused only on reducing PVE due to tagged fecal material. The proposed method reduces PVE using 3-dimensional adaptive density correction and then replaces tagged fecal material into air. Next, it generates natural PVE for the replaced air adjacent to soft tissue and finally makes smooth transition of gray values for soft tissue adjacent to the replaced air. The proposed method applied to eleven patient data, and showed promising results.

• 소음진동
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• 제11권2호
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• pp.323-328
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• 2001

The paper describes a theoretical study on the flexural vibration of an elastic rectangular plate with periodically nonuniform material properties. The approximate solution of the natural frequency and mode shape has been obtained using the perturbation technique for sinusoidal modulation of the flexural rigidity and mass density. It has been shown that distributed modes exist in the plate which Is a two-dimensional model of the flat panel speaker.

• 자연과학논문집
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• 제4권
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• pp.221-231
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• 1991

We have thought artistic charactics of modern form is abstract expression and purity and unity sight. Specially, modern sculpture form has strict geometrical form as showed in primitive art. In this circumstances, modern costume has stylized more artistic form in pure sight. Artistic characteristics showed in those collections are picturesque in material and sculpture in shillouette. Picturesque material pointed in decoretive function and simple shillouette pointed in sculpturesque body in modern costume.

• 한국구조물진단유지관리공학회 논문집
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• 제17권3호
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• pp.20-27
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• 2013

본 논문에서는 고유진동수를 구하기 Simple Iteration Method을 제시하였다. 이 방법은 임의의 단면과 지점을 갖고 임의의 하중을 받는 보나 탑의 진동모드와 관련된 고유진동수를 간편하면서도 정확하게 계산할 수 있는 획기적인 방법이다. 이 방법에는 공진상태에서 관성력에 기인한 부재의 처짐 모드를 구하게 된다. 진동해석을 위하여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 $D_{22}$ 휨강성의 영향을 철저하게 검토하였다. 본 논문에서는 구조 요소의 하중 분포 또는 상이한 단면에 따른 고유진동수에 대한 영향을 연구하였으며 그 결과를 제시하였다. 이 방법은 첨단복합재료를 포함한 2차원 문제에도 적용할 수 있다.

• Structural Engineering and Mechanics
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• 제88권1호
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• pp.1-12
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• 2023

In this study, forced vibration behavior of a piezo magneto electric sandwich Timoshenko beam is investigated. It is assumed a sandwich beam with porous core and graphene platelet reinforced composite (GPLRC) in facesheets subjected to magneto-electro-elastic and temperature-dependent material properties. The magneto electro platelets are under linear function along with the thickness that includes a cosine function and magnetic and electric constant potentials. The governing equations of motion are derived using modified strain gradient theory for microstructures. The effects of material length scale parameters, temperature change, different distributions of porous, various patterns of graphene platelets, and the core to face sheets thickness ratio on the natural frequency and excited frequency of a sandwich Timoshenko beam are scrutinized. Various size-dependent methods effects such as MSGT, MCST, and CT on the natural frequency is considered. Moreover, the final results affirm that the increase in porosity coefficient and volume fractions lead to an increase in the amount of natural frequency; while vice versa for the increment in the aspect ratio. From forced vibration analysis, it is understood that by increasing the values of volume fraction and the length thickness of GPL, the maximum deflection of a sandwich beam decreases. Also, it is concluded that increasing the temperature, the thickness of GPL, and the initial force leads to a decrease in the maximum deflection of GPL. It is also shown that resonance phenomenon occurs when the natural and excitation frequencies become equal to each other. Outcomes also reveal that the third natural frequency owns the minimum value of both deflection and frequency ratio and the first natural frequency has the maximum.

• 한국정밀공학회지
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• 제12권1호
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• pp.87-96
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• 1995

A new fungivle material named Epoxy-Granite composite is applied to the column structure of drilling center in order to investigate the advanced dynamic charateristics comparing with a conventional cast iron material. The dimensions of new column structure are adjusted to keep the same stiffness (EI value) and the manufacturing conditions are formulated based on the preceeding research experience about the development of Epoxy-Granite structural material. The two kinds of experiments are set up, one of which is for the measurement of natural mode and frequency using experimental modal analysis, and the other one is for the measurement of vibration amplitude during idling operation of a machine tool. The comparison of maximum accelerance values at each natural frequency of bending mode shows a Epoxy-Granite column have larger modal damping ratios(over 2times) than a cast iron column. The vibration amplitude of Epoxy-Granite column measrued on the bed, motor base, and top of column are also much smaller (up to 12%) than the case of cast iron column. It is therefore confirmed that a Epoxy-Granite material exhibits a good anti- vibrational propderty even if it is used under the actual operational environments of machine tool as a practical structural element.

• 한국실내디자인학회논문집
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• 제22권5호
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• pp.367-375
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• 2013

Using the 'New material' concept has recently been introduced into the natural characteristics. In the course of such a, Janine M. Benyus has proposed to mimic the characteristics of natural ecosystems to mention the concept of Biomimicry. Process made engineered using technical elements for representing the material properties of Biomimicry such will be acting importantly, This study intends to analyze how new materials applied to 'Biomimicry' characteristics are processed in space. The results were as follows : 1) Processing methods of new materials resulted as 'Forming', 'Surface treatment', 'Bonding', 'Inserting'. These four were divided and analyzed into 'Form', 'System', 'Adaptation'. As a result of this analysis, such significances were shown as 'Forming/Surface treatment/Bonding' in 'Form', 'Bonding' in 'System' and 'Adaptation'. 2) 'Bonding' applied to 'System' of new material can be recycled to be combined with other materials through the existing adhesive material, and present as a solution of 'Sustainable development'. 3) 'Bonding' applied to 'Adaptation' of new material is to impart the ability to react to the environment through the joint, but is characteristic, at this time, using digital and other field technology. It appeared primarily that it can be known to meet the social trends and convergence between fields. Thus, as the finish that are friendly to the environment from the interior design, the results of the study are expected to be utilized in the study of new materials guidelines.