• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.439-444
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• 2001

We provide methods to simulate noise propagation for an outdoor environment. Forward tracing method traces sound vectors from sources to receivers while geometry based computation finds all possible sound propagation between sources and receivers geometrically. We discuss defects in relying on a forward tracing method, and suggest a geometry based method. Geometry based method considers all possible direct and indirect(propagation via limited number of reflections) sound propagation saving computational time compared to forward sound tracing. Our simulation results are visualized using VRML(Virtual Reality Modeling Language).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.837-842
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• 2004

The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to do-Dopplerize the sound signals emitted from moving sources, two kinds of signal reconstruction methods were applied. One is the forward propagation method and the other is the backward propagation method. Forward propagation method analyze the source emission time based on the instantaneous distance between sensors and the assumed source position, then the signals are reconstructed with respect to the emission time. On the other hand, the backward method uses time delay to do-Dopplerize the acquired data for the received time of reference. In both techniques, the reconstructed signal data were processed using beamforming algorithm to produce power distributions at the frequency of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. Forward propagation method has shown better performance in locating source position than the backward propagation method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 학술대회 논문집 정보 및 제어부문
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• pp.323-324
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• 2008

In this paper, we present performance comparison of two methods to localize multiple robots. One is extended Kalman filter and the other is constraint propagation technique. Extended Kalman filter is conventional probabilistic method which gives the sub-optimal estimation rather than guarantee any boundary for true position of robot. In case of constraint propagation, it can give a boundary containing true robot position value. Especially, we deal with cooperative localization problem in outdoor environment for multiple robots equipped with GPS, gyro meter, wheel encoder. In simulation results, we present strength and weakness for localization methods based on extend Kalman filter and constraint propagation technique.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.882-886
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• 2005

As the TFT-LCD panels become larger and provide higher resolution, the distributed capacitive and resistive lines induce the propagation delay, reduce the TFT-on time and deteriorate the pixel chargingratio. A number of the compensation methods, like the H-LDC (Horizontal Line Delay Compensation), have been proposed to compensate the propagation delay of the large and high resolution panels [1]. These methods, however, require the comparatively accurate gate propagation delay estimates at each column driver. In this paper, by observing the actual gate and data waveform from 15-inch XGA TFT-LCD panels, we could predict the propagation delay along the row and column line.

• Geomechanics and Engineering
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• 제14권4호
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• pp.325-336
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• 2018

Deformation of rock masses is not only related to rock itself, but also related to discontinuities, the latter maybe greater. Study on crack propagation at discontinuities is important to reveal the damage law of rock masses. DDARF is a discontinuous deformation analysis method for rock failure and some modified algorithms are proposed in this study. Firstly, coupled modeling methods of AutoCAD-DDARF and ANSYS-DDARF are introduced, which could improve the modeling efficiency of DDARF compared to its original program. Secondly, a convergence criterion for automatically judging the computation equilibrium is established, it could overcome subjective drawbacks of ending one calculation by time steps. Lastly but not the least, relationship between the super relaxation factor and the calculation convergence is analyzed, and reasonable value range of the super relaxation factor is obtained. Based on these above modified programs, influences on crack propagation of joint angle, joint parameters and geo-stresses' side pressure are studied.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.101-104
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• 2000

In this paper, we analyze the propagation modeling methods to evaluate the IMT-2000 satellite RTT (Radio Transmission Technology). To generate Rayleigh random numbers having Jake's Doppler power density spectrum, the Rice's sum of sinusoids methods are used and their statistical characteristics are compared with each other.

• Smart Structures and Systems
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• 제23권2호
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• pp.185-194
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• 2019

The probabilistic tsunami risk assessment of large coastal areas is challenging because the inland propagation of a tsunami wave requires an accurate numerical model that takes into account the interaction between the ground, the infrastructures, and the wave itself. Classic mesh-based methods face many challenges in the propagation of a tsunami wave inland due to their ever-moving boundary conditions. In alternative, mesh-less based methods can be used, but they require too much computational power in the far-field. This study proposes a hybrid approach. A mesh-based method propagates the tsunami wave from the far-field to the near-field, where the influence of the sea floor is negligible, and a mesh-less based method, smooth particle hydrodynamic, propagates the wave onto the coast and inland, and takes into account the wave structure interaction. Nowadays, this can be done because the advent of general purpose GPUs made mesh-less methods computationally affordable. The method is used to simulate the inland propagation of the 2004 Indian Ocean tsunami off the coast of Indonesia.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.25-32
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• 2006

We present a imaging method of seismic sources by time reversal propagation of seismic waves. Time-reversal wave propagation is actively used in medical imaging, non destructive testing and waveform tomography. Time-reversal wave propagation is based on the time-reversal invariance and the spatial reciprocity of the wave equation. A signal is recorded by an array of receivers, time-reversed and then back-propagated into the medium. The time-reversed signal propagates back into the same medium and the energy refocuses back at the source location. The increasing power of computers and numerical methods makes it possible to simulate more accurately the propagation of seismic waves in heterogenous media. In this work, a staggered-grid finite-difference solution of the elastic wave equation is employed for the wave propagation simulation. With numerical experiments, we show that the time-reversal imaging will enable us to explore the spatio-temporal history of complex earthquake.

• 원예과학기술지
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• 제35권3호
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• pp.373-380
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• 2017

Amaryllis ($Hippeastrum{\times}johnsonii$) is commonly propagated by three methods: seeds, offset bulblets, and twin scaling. Since the number and size of bulblets produced by these methods are low, we conducted an experiment to evaluate different bulb cutting methods for propagation. For this purpose, bulbs (circumference of 30 - 35 cm) were sectioned or notched into 8, 12, or 16 segments or twin-scaled into 48, 72, or 96 segments for bulblet formation. Our results show that the largest number of bulblets was produced by the twin scaling method, but they take longer to grow to a final, commercial size. Sectioning and notching resulted in larger, but fewer bulblets than twin-scaling. Compared to notching, sectioning provided more space for the bulblets to grow, and is therefore the recommended method. While increasing the number of sections cut from a single bulb resulted in a larger number of bulblets, the diameter of the bulblets decreased. Therefore, sectioning the bulb into 8 segments was the best method for producing an acceptable number of vigorous bulblets.

• 한국산업보건학회지
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• 제32권2호
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• pp.111-115
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• 2022

Objectives: The purpose of this study is to verify whether droplet-induced propagation, the main route of infectious diseases such as COVID-19, can occur in semiconductor FAB (Fabrication), based on research results on general droplet propagation. Methods: Through data surveys droplet propagation was modeled through simulation and experimental case analysis according to general (without mask) and mask-wearing conditions, and the risk of droplet propagation was inferred by reflecting semiconductor FAB operation conditions (air current, air conditioning system, humidity, filter conditions). Results: Based on the results investigated to predict the possibility of spreading infectious diseases in semiconductor FAB, the total amount of droplet propagation (concentration), propagation distance, and virus life in FAB were inferred by reflecting the management parameter of semiconductor FAB. Conclusions: The total amount(concentration) of droplet propagation in the semiconductor fab is most affected by the presence or absence of wearing a mask and the line air dilution rate has some influence. when worn it spreads within 0.35~1m, and since the humidity is constant the virus can survive in the air for up to 3 hours. as a result the semiconductor fab is judged to be and effective space to block virus propagation due to the special environmental condition of a clean room.