• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1499-1507
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• 2017

This paper presents an impact-based piezoelectric vibration energy harvester using a freely movable metal sphere and a piezoceramic fiber-based MFC (Macro Fiber Composite) as piezoelectric cantilever. The free motion of the metal sphere, which impacts both ends of the cavity in an aluminum housing, generates power across a cantilever-type MFC beam in response to low frequency vibration such as human-body-induced motion. Impacting force of the spherical proof mass is transformed into the vibration of the piezoelectric cantilever indirectly via the aluminum housing. A proof-of-concept energy harvesting device has been fabricated and tested. Effect of the indirect impact-based system has been tested and compared with the direct impact-based counterpart. Maximum peak-to-peak open circuit voltage of 39.8V and average power of $598.9{\mu}W$ have been obtained at 3g acceleration at 18Hz. Long-term reliability of the fabricated device has been verified by cyclic testing. For the improvement of output performance and reliability, various devices have been tested and compared. Using device fabricated with anodized aluminum housing, maximum peak-to-peak open-circuit voltage of 34.4V and average power of $372.8{\mu}W$ have been obtained at 3g excitation at 20Hz. In terms of reliability, housing with 0.5mm-thick steel plate and anodized aluminum gave improved results with reduced power reduction during initial phase of the cyclic testing.

• Structural Engineering and Mechanics
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• v.51 no.5
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• pp.793-808
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• 2014

The goal of this study is to evaluate and design steel plates with optimal material distributions achieved through a specific material topology optimization by using a CCARAT (Computer Aided Research Analysis Tool) as an optimizer, topologically optimally updating node densities as design variables. In typical material topology optimization, optimal topology and layouts are described by distributing element densities (from almost 0 to 1), which are arithmetic means of node densities. The average element densities are employed as material properties of each element in finite element analysis. CCARAT may deal with material topology optimization to address the mean compliance problem of structural mechanical problems. This consists of three computational steps: finite element analysis, sensitivity analysis, and optimality criteria optimizer updating node densities. The present node density based design via CCARAT using node densities as design variables removes jagged optimal layouts and checkerboard patterns, which are disadvantages of classical material topology optimization using element densities as design variables. Numerical applications that topologically optimize reinforcement material distribution of steel plates of a cantilever type are studied to verify the numerical superiority of the present node density based design via CCARAT.

• Korean Institute of Interior Design Journal
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• no.13
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• pp.203-215
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• 1997

This Study typed the roof-design in analysis of structural design of the glulam architecture, developed worldwidely, nowaday. For this, it is studied the characters of glulam as the history of glulam architectures, manufacture of glulam, shapes and section of glulam, fireproof and combution of glulam. And it is studied roof-design according to structural type of glulam roof-structure. Conclusively, types of glulam roof design typied as 1)the Simple Beam str., 2)the Multi-Joints continous Beam str. 3)the Hinge str. 4)the Rahmen str. 5)the Archi str. 6)the Grid str. 7)etc str. (Folded-plate str., Radial str., Cylinder Shell str., Ring Dome str., Geodesic Dome str., Conic Coloid Shell str., H.P Shell str. Cantilever Shell str.)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2047-2054
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• 1997

This paper describes a measuring method of vibration mode shapes by the Electronic Shearography. This method called the speckle interferometer has many merits in practical use, such as low sensitivity to environmental noise, low limit of coherent-length and simple optical configuration. In this study, we developed Michelson-type shearing interferometer provided with a phase stepping mirror and with a bias modulation mirror to quantify the vibration gradient fields. Results of application to a simple cantilever plate show that the vibration amplitude fields obtained are in good agreement with those of the electronic speckle pattern interferometry (ESPI).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1064-1070
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• 2010

In this work, a dynamic absorber with a plate-type cantilever using magnetic force is proposed to reduce the vibration of a compressor directly. The dynamic absorber using magnetic force has some advantages of easily tuning the control frequency by adjusting the magnet spacing and obtaining wider control frequency band. The dynamic absorber is designed theoretically and tested experimentally to estimate the control frequency band. When the compressor is equipped with the dynamic absorber, the vibration of compressor and the noise level of refrigerator are reduced by 30 % and 3.2 dB respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.432-438
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• 1994

This paper describes the measuring method of vibration mode shapes by the Electronic Shearography. Shearographic interferometer has many merits in practical use, that is low sensitive to the environmental noisy, liw limit of the coherent-length and simple optical configuration etc.. In this study, we developed Michelson-type shearing interferometer provided with a phase stepping mirror and with a bias modulation mirror to quantify the vibration gradient fields. As a results of application to a simple cantilever plate vibration amplitude fields were obtained by the proper integration technique, and their exprimental results were in good agreement with those of the ESPI experiment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.495-500
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• 2007

A Meshfree is a method used to establish algebraic equations of system for the whole problem domain without the use of a predefined mesh for the domain discretization. A point interpolation method is based on combining radial and polynomial basis functions. Involvement of radial basis functions overcomes possible singularity. Furthermore, the interpolation function passes through all scattered points in an influence domain and thus shape functions are of delta function property. This makes the implementation of essential boundary conditions much easier than the meshfree methods based on the moving least-squares approximation. This study aims to investigate a stress analysis of structural element between a meshfree method and the finite element method. Examples on cantilever type plate and stress concentration problems show that the accuracy and convergence rate of the meshfree methods are high.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.349-359
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• 2023

This paper presents a technique for determining the optimal number of elements in stochastic finite element analysis based on reliability analysis. Using the change-of-variable perturbation stochastic finite element approach, the probability density function of the dynamic responses of stochastic structures is explicitly determined. This method combines the perturbation stochastic finite element method with the change-of-variable technique into a united model. To further examine the relationships between the random fields, discretization of the random field parameters, such as the variance function and the scale of fluctuation, is also performed. Accordingly, the reliability index is calculated based on the explicit probability density function of responses with Gaussian or non-Gaussian random fields in any number of elements corresponding to the random field discretization. The numerical examples illustrate the effectiveness of the proposed method for a one-dimensional cantilever reinforced concrete column and a two-dimensional steel plate shear wall. The benefit of this method is that the probability density function of responses can be obtained explicitly without the use simulation techniques. Any type of random variable with any statistical distribution can be incorporated into the calculations, regardless of the restrictions imposed by the type of statistical distribution of random variables. Consequently, this method can be utilized as a suitable guideline for the efficient implementation of stochastic finite element analysis of structures, regardless of the statistical distribution of random variables.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1125-1132
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• 2009

The theory and a probe of the pilot hole wall deformation method, which is a 3-dimensional stress measurement method based on the stress relief principle, were developed. A pilot hole is drilled from the bottom of a borehole and the stress measurement probe is inserted into the pilot hole. The borehole is advanced as the overcoring and the changes in the radius of the pilot hole in three directions and in the axial lengths between the borehole bottom and the pilot hole wall along four axial lines are measured by cantilever type-displacement sensors. The differences between the displacements by the elastic stress analysis and those measured by using the probe were within 3% in the uniaxial compression test of an acrylic resin plate having a hole.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.3
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• pp.311-319
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• 2007

A Meshfree is a method used to establish algebraic equations of system for the whole problem domain without the use of a predefined mesh for the domain discretization. A point interpolation method is based on combining radial and polynomial basis functions. Involvement of radial basis functions overcomes possible singularity Furthermore, the interpolation function passes through all scattered points in an influence domain and thus shape functions are of delta function property. This makes the implementation of essential boundary conditions much easier than the meshfree methods based on the moving least-squares approximation. This study aims to investigate a stress analysis of structural element between a meshfree method and the finite element method. Examples on cantilever type plate, hollow cylinder and stress concentration problems show that the accuracy and convergence rate of the meshfree methods are high.