• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.36-43
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• 2001

In Korea, we are absolutely short of earthquake data in good quality from moderate and large earthquakes, which are needed fur the study of strong ground motion characteristics. This means that the best use of the available data is needed far the time being. In this respect, several methods are suggested in this paper, which can be applied in the process of data selection and analysis. First, it is shown that the calibration status of seismic stations can be easily checked by comparing the spectra from accelerometer and velocity sensor both of which are located at the same location. Secondly, it is recommended that S/N ratio in the frequency domain should be checked before discarding the data by only look of the data in time domain. Thirdly, the saturated earthquake data caused by ground motion level exceeding the detection limit of a seismograph are considered to see if such data can be used for spectrum analysis by performing numerical simulation. The result reveals that the saturated data can still be used within the dominant frequency range according to the levels of saturation. Finally, a technique to minimize the window effect that distorts the low frequency spectrum is suggested. This technique involves detrending in displacement domain once the displacement data are obtained by integration of low frequency components of the original data in time domain. Especially, the low frequency component can be separated by using discrete wavelet transform among many alternatives. All of these methods mentioned above may increase the available earthquake data and frequency range.

• Journal of the Korean Society of Visualization
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• v.2 no.2
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• pp.8-15
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• 2004

With all the recent progresses in computer hardware and software technology, the animation of fluids in real-time is still among the most challenging issues of computer graphics. The fluid animation is carried out in two steps - the physical simulation of fluids immediately followed by the visual rendering. The physical simulation is usually accomplished by numerical methods utilizing the particle dynamics equations as well as the fluid mechanics based on the Navier-Stokes equations. Particle dynamics method is usually fast in calculation, but the resulting fluid motion is conditionally unrealistic. The methods using Navier-Stokes equation, on the contrary, yield lifelike fluid motion when properly conditioned, yet the complexity of calculation restrains this method from being used in real-time applications. This article presents a rapid fluid animation method by using the continuum-based fluid mechanics and the enhanced particle dynamics equations. For real-time rendering, pre-integrated volume rendering technique was employed. The proposed method can create realistic fluid effects that can interact with the viewer in action, to be used in computer games, performances, installation arts, virtual reality and many similar multimedia applications.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.913-920
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• 2005

Compared to previous in-vitro test, FE model showed reliable motion patterns. A finite element model of a 50th percentile male neck was developed to study the mechanics of whiplash injury while the rear impacts. The model was consisted of the whole cervical vertebrae including part of occipital, intervertebral discs. which were modeled using linear viscoelastic materials and posterior elements. The sliding interfaces were defined to simulate contact phenomena in facet joints and in odontoid process. All ligaments and atlanto-occipital membrane were modeled as nonlinear bar elements. Only muscle elements were not considered. Motion of each cervical vertebra was obtained from the dynamic simulation with a MADYMO model for 15 km/h $40\%$ rear end offset impacts. Soft tissue neck injury(STNI) was investigated with a developed FE model. In FE model analysis, the high stress was appeared at C3/C4 disc in offset impact. Further research is still needed in order to improve the developed neck FE model for many different crash patterns.

• Smart Structures and Systems
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• v.26 no.4
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• pp.419-433
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• 2020

Investigation of structural integrity has been a critical issue in the field of civil engineering for years. Visual inspection is one of the most available methods to explore deteriorative components in structures. Still, this method is not applicable to invisible damage of structures. Alternatively, system identification methods are capable of tracking modal properties of structures over time. The deviation of these dynamic properties can serve as indicators to access structural integrity. In this study, a modal tracking technique using frequency-domain system identification from seismic responses of structures is proposed. The method first segments the measured signals into overlapped sequential portions and then establishes multiple Hankel matrices. Each Hankel matrix is then converted to the frequency domain, and a temporal-average frequency-domain Hankel matrix can be calculated. This study also proposes the frequency band selection that can divide the frequency-domain Hankel matrix into several portions in accordance with referenced natural frequencies. Once these referenced natural frequencies are unavailable, the first few right singular vectors by the singular value decomposition can offer these references. Finally, the frequency-domain stochastic subspace identification tracks the natural frequencies and mode shapes of structures through quick stabilization diagrams. To evaluate performance of the proposed method, a numerical study is carried out. Moreover, the long-term monitoring strong motion records at a specific site are exploited to assess the tracking performance. As seen in results, the proposed method is capable of tracking modal properties through seismic responses of structures.

• Clinics in Shoulder and Elbow
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• v.8 no.2
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• pp.181-186
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• 2005

An anterior dislocation of the elbow without a fracture of the olecranon is an extremely rare injury. This paper reports a 36-year-old male who stumbled and fell on his outstretched hand during a soccer game. The anteroposterior and lateral radiographs indicated a simple anterior dislocation of the elbow, which was reduced using a closed method. The elbow joint was stable in the range of motion, but the sensation of the two ulnar digits was still reduced. MRI was useful for the identification of the pathoanatomy. At the follow-up examination three months after the initial trauma, the hypesthesia has fully recovered and the patient regained the full range of the elbow and forearm motion without pain and instability. After 18 months, the patient had a normal elbow function, and could play various sports. If an anterior elbow dislocation is detected early, a closed reduction with careful pathoanatomical considerations would be successful.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.63-68
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• 2018

At present, ultra-precision cutting technology has been studied in Korean research institutes, focusing on development of ultra-precision cutting tool technology and ultra-precision control engineering. However, the developed technologies are still far behind advanced countries. It focuses on metals including aluminum, copper and nickel, and nonmetals including plastics, silicone and germanium which require high precision while using a lathe. It is hard to implement high precision by grinding the aforementioned materials. To address the issue, the ultra-precision cutting technology has been developing by using ultra-precision machine tools very accurate and strong, and diamond tools highly abrasion-resistant. To address this issue, this study aims to conduct ultra-precision cutting by using ECTS (Error Compensation Tool Servo) to improve motion precision of elements and components, and compensate for motion errors in real time. An IR camera is used for analyzing cutting accuracy differences depending on the heat generated in diamond tools in cutting to examine the heat generated in cutting to study cutting accuracy depending on generated heat.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.8
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• pp.729-734
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• 2015

Improvement in the control strategy for continuous casting is a crucial requirement to enhance the slab's quality and to increase productivity. The mold oscillator adopts the dual cylinders due to its heavy weight, so the synchronized motion of two cylinders is an important aspect when precise control is needed. The conventional method uses the master-slave control applied to the valve input reference, but the synchronization performance should still be improved. This paper proposes a novel synchronization algorithm for dual cylinders used in a mold oscillator. The master-slave concept is applied to the target reference position, that is, the slave target reference position is controlled to match the slave cylinder's position with the master cylinder's position. In the simulation based on a Simulink model, the proposed algorithm shows a better synchronization performance in aspect of the mean of the absolute error and the peak synchronization error.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.93-97
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• 2015

How high-mass stars form is currently unclear. Calculations suggest that the radiation pressure of a forming star can halt spherical infall, preventing further growth when it reaches $10M_{\odot}$. Two major theoretical models on the further growth of stellar mass have been proposed. One model suggests the merging of less massive stellar objects, and the other is through accretion, but with the help of a disk. Inflow motions are key evidence for how forming stars gain further mass to build up massive stars. Recent developments in technology have boosted the search for inflow motion. A number of high-mass collapse candidates were obtained with single dish observations, and mostly showed blue profiles. Infalling signatures seem to be more common in regions which have developed radiation pressure than in younger cores, which is the opposite of the theoretical prediction and is also very different from observations of low mass star formation. Interferometer studies so far confirm this tendency with more obvious blue profiles or inverse P Cygni profiles. Results seem to favor the accretion model. However, the evolution of the infall motion in massive star forming cores needs to be further explored. Direct evidence for monolithic or competitive collapse processes is still lacking. ALMA will enable us to probe more detail of the gravitional processes.

• Journal of Korea Multimedia Society
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• v.24 no.7
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• pp.890-902
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• 2021

Although the object detection accuracy with still images has been significantly improved with the advance of deep learning techniques, the object detection problem with video data remains as a challenging problem due to the real-time requirement and accuracy drop with occlusion. In this research, we propose a method in pig detection for video monitoring environment. First, we determine a motion, from a video data obtained from a tilted-down-view camera, based on the average size of each pig at each location with the training data, and extract key frames based on the motion information. For each key frame, we then apply YOLO, which is known to have a superior trade-off between accuracy and execution speed among many deep learning-based object detectors, in order to get pig's bounding boxes. Finally, we merge the bounding boxes between consecutive key frames in order to reduce false positive and negative cases. Based on the experiment results with a video data set obtained from a pig farm, we confirmed that the pigs could be detected with an accuracy of 97% at a processing speed of 37fps.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.233-242
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• 2019

Numerous space perception studies have shown that Euclidean 3-D structure cannot be recovered from binocular stereopsis, motion, combination of stereopsis and motion, or even with combined multiple sources of optical information. Humans, however, have no difficulties to perform the task-specific action despite of poor shape perception. We have applied humans skill and capabilities to artificial intelligence and computer vision but those machines are still far behind from humans abilities. Thus, we need to understand how we perceive depth in space and what information we use to perceive 3-D structure accurately to perform. The purpose of this paper was to review space perception literatures to apply humans abilities to artificial intelligence robots more advanced in future.