• Proceedings of the Korean Society of Veterinary Clinics Conference
• /
• 2006.05a
• /
• pp.142-142
• /
• 2006

• Journal of the Earthquake Engineering Society of Korea
• /
• v.22 no.4
• /
• pp.253-259
• /
• 2018

Structure behaviors resulting from an earthquake are experimentally simulated mainly through a shaking table test. As for large-scale structures, however, size effects over a miniature may make it difficult to assess actual behaviors properly. To address this problem, research on the hybrid simulation is being conducted actively. This method is to implement numerical analysis on framework members that affect the general behavior of the structure dominantly through an actual scale experiment and on the rest parts by applying the substructuring technique. However, existing studies on hybrid simulation focus mainly on Slow experimental methods, which are disadvantageous in that it is unable to assess behaviors close to the actual level if material properties change depending on the speed or the influence of inertial force is significant. The present study aims to establish a Real-time hybrid simulation system capable of excitation based on the actual time history and to verify its performance and applicability. The hybrid simulation system built up in this study utilizes the ATS Compensator system, CR integrator, etc. in order to make the target displacement the same with the measured displacement on the basis of MATLAB/Simulink. The target structure was a 2-span bridge and an RC pier to support it was produced as an experimental model in order for the shaking table test and Slow and Real-time hybrid simulations. Behaviors that result from the earthquake of El Centro were examined, and the results were analyzed comparatively. In comparison with the results of the shaking table test, the Real-time hybrid simulation produced more similar maximum displacement and vibration behaviors than the Slow hybrid simulation. Hence, it is thought that the Real-time hybrid simulation proposed in this study can be utilized usefully in seismic capacity assessment of structural systems such as RC pier that are highly non-linear and time-dependent.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.04a
• /
• pp.681-688
• /
• 2009

This paper deals with a bearing faults localization technique based on holographic approach by visualizing sound radiated from the faults. The main idea stems from the phenomenon that bearing faults in a moving vehicle generate impulsive sound. To visualize fault signal from the moving vehicle, we can use the moving frame acoustic holography [H.-S. Kwon and Y.-H. Kim, "Moving frame technique for planar acoustic holography," J. Acoust. Soc. Am. 103(4), 1734-1741, 1998]. However, it is not easy to localize faults only by applying the method. This is because the microphone array measures noise (for example, noise from other parts of the vehicle and the wind noise) as well as the fault signal while the vehicle passes by the array. To reduce the effect of noise, we propose two ideas which utilize the characteristics of fault signal. The first one is to average holograms for several frequencies to reduce the random noise. The second one is to apply the partial field decomposition algorithm [K.-U. Nam, Y.-H. Kim, "A partial field decomposition algorithm and its examples for near-field acoustic holography," J. of Acoust. Soc. Am. 116(1), 172-185, 2004] to the moving source, which can separate the fault signal and noise. Basic theory of those methods is introduced and how they can be applied to localize bearing faults is demonstrated. Experimental results via a miniature vehicle showed how well the proposed method finds out the location of source in practice.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.145-154
• /
• 2003

In this study, the variation in excess pore pressure during dissipation is estimated by using successive cavity expansion theory and finite difference technique based on axisymmetric uncoupled linear consolidation theory with separate consideration of magnitude and initial distribution $\Delta{u}_{oct}$induced by changes of octahedral normal stress, and $\Delta{u}_{shear}$ induced by changes of octahedral shear stress. The coefficient of consolidation is also estimated by trial and error procedure until the predicted dissipation curve matches the measured curve at a typical degree of dissipation. The proposed method is applied to the results of miniature piezocone tests at Louisiana State University calibration chamber system. Based on the results of interpretation and the comparison with experimental measurements and those from other solutions, the prediction dissipation curves show a good match with those measured during dissipation tests and the values of coefficient of consolidation estimated by proposed method are more close to the range of laboratory measurements than those of other theories.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.1
• /
• pp.47-52
• /
• 2011

It is well known that stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates because the layup of composite laminates influences their properties. Ultrasonic NDE of composite laminates is often based on the backwall echoes of the sample. A pair of such transducers was mounted in a holder in a nose-to-nose fashion to be used as a scanning probe on composites. Miniature potted angle beam transducers were used (Rayleigh waves in steel) on solid laminates of composites. Experiments were performed to understand the behavior of the transducers and the nature of the waves generated in the composite (mode, wave speed, angle of refraction). C-scan images of flaws and impact damage were then produced by combining the pitch-catch probe with a portable manual scanner known as the Generic Scanner ("GenScan"). The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to fiber orientation of the CFRP composites, including low level porosity, ply waviness, and cracks. Therefore, it is found that the experimentally Rayleigh wave variation of pitch-catch ultrasonic signal was consistent with numerical results and one-side ultrasonic measurement might be very useful to detect the defects.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.2
• /
• pp.5-16
• /
• 2005

Tn this study, model soil deposits are prepared in large test chambers to minimize the scale effects. Also, slurry of mixture containing 50 percent kaolin clay and 50 percent silica has been consolidated to simulate the process of natural soil deposit formation and to reduce the consolidation time. To provide a more detailed description of varying soil properties along the soil profile of model clay deposits and to compare the in-situ test results with those from prototype tests, miniature in-situ tests, including vane shear, piezoprobe, and cone penetration tests were conducted in each of the clay deposits. The current results indicate that consistent soil deposits were prepared for the current and previous test programs. Also, reasonable predicting methods of prototype behavior based on model in-situ test results were suggested in this study by examining differences between the test results from both the model and prototype tests.

• Journal of the Korean Geosynthetics Society
• /
• v.10 no.4
• /
• pp.81-92
• /
• 2011

In order to understand evaluation of the seismic stability of a fill dam, we made chambers of 1:100, 1:70, and 1:50 (the ratio of the miniature), considering the law of similarity based on drawings of three representative cross sections. And we measured an increase in acceleration, excess pore water pressure, and vertical/horizontal displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the stability and interaction between the ground, the structure, and fluids based on the measurements. As a result, we could observe that displacement of the target cross section was relatively small compared to the allowed level of 30 cm, ensuring proper stability for an earthquake. Regarding the acceleration measurements, the increase rate was 20% for Hachinohe wave and Ofunato wave but 30% for the artificial wave. With respect to the excess pore water pressure, it was lower than 1 (which is the permissible ratio for liquefaction) ensuring proper stability as well.

• Journal of the Korean Geosynthetics Society
• /
• v.10 no.4
• /
• pp.49-59
• /
• 2011

In order to understand evaluation of the seismic stability of a reinforced earth retaining, we made chambers of 1:10 (the ratio of the miniature), considering the law of similarity based on drawings of representative cross sections. And we measured an increase in acceleration, earth pressure, and displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the external stability of the reinforced earth retaining wall during earthquake based on the measurements. As a result, the unreinforced earth retaining wall collapsed at 2 g of seismic acceleration. But the reinforced earth retaining wall was evaluated to ensure proper stability as well, with respect to the earth pressure gauge, the increments of earth pressure tend to be raised significantly in the upper than the lower and showed a similar characteristic of behavior in previous theory.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.5
• /
• pp.76-82
• /
• 2001

Because the biological tissue with inhomogeneous acoustic properties does not keep a particular shape, the measurement of propagation characteristics of ultrasonic fields by the conventional scanning method with a miniature hydrophone is difficult. In this study, a two-dimensional may hydrophone was fabricated using the PVDF (Polyvinylidene fluoride) piezo-electric film and a ultrasonic field measurement system with it was established. For the acoustic field produced by a circular plan transducer with center frequency of 2.25㎒ and 13㎜ in diameter, it was possible to make a fairly accurate field measurement using the hydrophone system. The attenuation coefficients at 2.25 ㎒ for biological tissues were 0.7∼1.3 dB/cm(average; 1.0 dB/cm) in bovine liver, 1.0∼1.8 dB/cm (average; 1.6 dB/cm) in pig liver, 0.9∼2,9 dB/cm(average: 2.1 dB/cm) in bovine muscles, 1.7∼3.3 dB/cm (average; 2.5 dB/cm) in pig muscles.

• Journal of Korea Multimedia Society
• /
• v.11 no.9
• /
• pp.1245-1257
• /
• 2008

The establishment of a production pipeline imported 30 computer graphics is suggested in this paper to improve the efficiency of existing production pipeline of clay animation. The point is that the process of building clay characters that remains labor intensive among the existing procedures is replaced by the process of creating computer generated characters. In order to create characters out of clay by means of 30 computer graphics, a diffuse map and displacement map are made of an oil-based clay according to the UVW coordination of polygon modeling, which is the same color and kind of clay used to make a clay character. In addition, a panoramic HDRI recording system is developed to record the lighting information of shooting environment for miniature sets, which is imported in 3D computer graphic tools as digital light source. On account of the new production pipeline, a hyper realistic rendering image can be produced, and at the same time it improves the traditional pipeline of stop motion animation that is know-how based procedure of a complete artist by the engineering approach to the automatic process.