• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.2011-2014
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• 2005

The purpose of this study is to compare the modal parameters of a newly developed soft golf club prototype, which is designed to be lighter than regular golf clubs, with those of a regular commercial golf club. The modal tests were performed with two kinds of boundary conditions. The first condition was free-free condition and the second was fixed-free condition. An impact hammer and a Fast Fourier Transform analyzer were used to obtain modal data. From the results, it was found out that the modal characteristics of the soft golf club prototype were close to those of the regular golf club although the weight of the soft club was lighter. Therefore, the soft golf club is expected to be able to convey similar feel to the golfers even with lighter weight. This would enable elderly golfers to swing easily with the soft golf club with same skill which they acquired with regular golf clubs but with reduced load to their muscles.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.1
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• pp.1-6
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• 2017

Surge pressure is created by rapid change of flow rate due to operation of hydraulic component or accident of pipeline. Proper control of surge pressure in distribution system is important because it can damage pipeline and may have the potential to degrade water quality by pipe leakage due to surge pressure. Surge relief valve(SRV) is one of the most widely used devices and it is important to determine proper parameters for SRV's installation and operation. In this research, determining optimum parameters affecting performance of the SRV were investigated. We proposed the methodology for finding combination of parameters for best performance of the SRV. Therefore, the objective function for evaluate fitness of candidate parameters and surge pressure simulation software was developed to validate proposed parameters for SRV. The developed software was integrated into genetic algorithm(GA) to find best combination of parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.457-462
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• 2006

This paper is concerned with the active vibration control experiment on cylindrical shell equipped with Macro Fiber Composite(MFC) actuators. The MFC actuators were glued to the cylindrical shell in circumferential directions. To verify the theoretical result, vibration test using impact hammer and accelerometer was carried out. It was found from experiments that theoretical result predicts experimental result to some extent. The positive position feedback controllers were designed and applied to the test article. It was observed that the resonant amplitude of the fundamental mode was reduced by 20dB thus achieving active vibration control. The active vibration control of the response subject to non resonant excitation has been of interest. We developed the combination of the positive position feedback controller which can cope with the fundamental mode and the positive position feedback controller which can counteract the external disturbance with non resonant frequency. It was found from experiments that the hybrid controller can suppress the vibration amplitude successfully.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.129-139
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• 2005

In this paper, the behaviors of tunnel damaged by fire, the diagnostic techniques for evaluating tunnel stability are presented. Also two fireproof construction methods are recommended. Three tunnels damaged by fire were analyzed to evaluate the structural stability. From the these analyzed, it is recommended that surface checking, rebound number of concrete by Schmidt Hammer, and carbonation of concrete are essential to evaluate the engineering properties of concrete in tunnel structure damaged by fire. On the basis of case studies of tunnel fire collected by ITA, the change of concrete and steel strengths by fire are explained, and numerical analysis, which was performed on culvert and circle tunnel, shows that distribution of temperature in the tunnel is dependant upon tunnel shape. Two fireproof construction methods using panel and punching metal are introduced to protect the tunnel by fire.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.317-321
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• 2003

A conventional typewriter types letters by hammering a carbon ribbon which is attached at a paper. The laser typing process which write a micro pattern of Chrome on a silicon wafer has been developed. A glass that is coated with 100 nm Chrome (Carbon ribbon) is attached on a silicon wafer (paper). An Nd-Yag laser (hammer) is irradiated on the glass, and the Chrome is transferred on the silicon wafer. Micro patterns are made by controlling laser beam trajectory. The suggested micro pattering can be used at the high density data storage of TeraBit/in$^2$ or at the improvement of productivity of semiconductor manufacturing procedure.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.805-811
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• 2016

Prior to installation in a navy ship, shipboard equipment should be qualified by shock test requirements. The multi-function console mounted on the elastic platform of the ship should also withstand given shock loads. In this study, both real shock test methods, as well as numerical computer simulations using the finite element method were used to verify structural durability under shock load conditions. First, we used domestic test facilities to perform possible shock tests, including an impact hammer test, a drop table test and a shaker shock test. Full model tests satisfying the shock response spectrum level were performed. Thereafter, an analytical model of the complex console structure was built by the finite element method. Finally, numerical results were verified by modal test results of the real product and an FEA analysis was also performed with a full model transient response analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1885-1895
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• 1997

As track density needs to increase to the order of 10, 000 tpi, the suspension has become a critical component in hard disk drives. One of the main obstacles to attain high track density is the structural resonances of the suspension in lateral direction. We investigate the suspension dynamics through the experimental modal analysis and the finite element method. An LDV (Laser Doppler Vibrometer) is employed to measure the response of the suspension which is excited by a shaker and an inpulse hammer for the free condition and the loaded condition, respectively. After comparing the experimental and numerical results, we study how the initial geometry of the bend region affects the suspension dynamics. It is found that the natural frequency of the sway mode decreases as the bend ratio and the bend angle increase. The shape of torsional mode changes as the mass of a slider increases, resulting in a local decrease in the natural frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.5-13
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• 2017

Noise complaints among neighbors in apartment building are mainly caused by floor impact noise that is structure born noise due to occupant induced floor vibration. To control this noise problems many researchers have investigated floor systems and finishing materials. Light-weight impact noise affects by finishing materials, but heavy-weight impact noise induced by heel impacts during normal walking or jumping of children is concerned with structural system and floor vibration. To figure out the characteristics of floor impact noise and transmission of floor vibration due to human activities, vibration tests were conducted in apartment buildings. Impact hammer, heel drop and walking activities were loaded at center of upstairs living room, and accelerations of slabs for both upstairs and downstairs and sound pressure levels for downstairs were measured. The acceleration ratio of transmitted floor vibration to downstairs and human induced vibration in upstairs was between 0.5 and 1.0 according to slab size, wall, and load type. And floor impact noise occurred in the range of natural frequency of slab.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.186-194
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• 2004

Experiments were conducted to determine the structural static and dynamic characteristics of air foil bearings. The housing of the bearing on the journal was driven by an impact hammer which was used to simulate dynamic forces acting on the bump loll with various leading condition. Two different bump foils (Cu-coated bump and viscoelastic bump) were tested and the static and dynamic coefficients of two bump foils compared, based on the experimental measurements for a wide range of operating conditions. The static and dynamic characteristics of air foil bearings were extracted 0rpm the frequency response function by least square method and IV(Instrumental Variable) method. The experiment was tested at 0rpm and $10,000\~16,000rpm$, and loaded on $50\~150N$. From the test results, the possibility of the application of high load and high speed condition is suggested.

• Economic and Environmental Geology
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• v.17 no.1
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• pp.57-78
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• 1984

The object of this study is to offer the standarized data for the design and calculating engineering cost of the rock excavation an the construction of the 3rd and 4th Seoul Subway lines From Jnauary to March in 1983, this study was carried out by the both methods of the field and laboratary studies. In the field, the geological survey in the entire area of Seoul City and sites on the subway lines were carried out and also a site measure of uniaxial compressional strength of rock masses by using Schmidt hammer was done. The labartory studies were carsied out by a study of preuions surveyes, microscopic studies of the mineral composition and degree of weathering of rocks, and measure of uniaxial compressional strengths Finally an engineering classification of each rock masses of South Africa council for Scientific and Industrial Research, CSIR, after Bieniawski, 1974. was done. In this method of classification 6 parameters such as strength of intact rock material, rock quality designation, spacing of fractures, condition of fractures, groundwater conditions, and the effect of fracture strike and dip orientation in tunnelling were used to evaluate rating of each rock mass.