• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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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.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.434-442
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• 2003

Taking advantage of the probability function, we have analyzed the localization phenomenon of the solution of a propagating function under the condition that the propagation constants are randomly distributed. For example, we have investigated the localization phenomenon of the voltage wave for a transmission line in which the characteristic impedance is randomly distributed. We have confirmed that the localized solution is in existence on the random lossless transmission line. Even in the case that the voltage wave is impulsively excited by the current source, the voltage wave is localized. Because the light wave is seriously affected at the localized position in the lossy transmission line, we have determined that the light wave localization phenomena are generated by multi-reflection.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.13 no.3
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• pp.148-156
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• 1984

The effect of inclination on the steady, two-dimensional, laminar natural convection in rectangular enclosures with localized heating from below has been investigated numerically. The enclosure was uniformly heated with a partial heat source at the center of the bottom wall and cooled from the upper wall while the other walls were insulated. The governing equations were solved numerically by using the ADI finite difference method with the SOR method. The computations were carrid out with air, Pr =0.733, in the Grashof number range, $1\times10^4\~3\times10^4$, for the inclination of the enclosures was varied from $0^{\circ}\;to\;90^{\circ}$. The effects of Grashof number and aspect ratio on the inclination for the transition of the flow pattern in enclosures were determined. From the results, it was found that the transition angles of the flow in the enclosures were greater in localized heating than in uniform heating from below, and that the inclination was to strongly effect on the heat transfer and the flow pattern within the enclosure.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.73.1-73.1
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• 2010

We use three-dimensional hydrodynamic simulations to investigate the characteristics of turbulence driven in rotating, vertically-stratified disk. Our models are isothermal, and local in the in-plane direction while global in the vertical direction. We allow localized regions with density larger than the threshold value to explode and inject kinetic energy to the surrounding medium in the real space rather than Fourier space, mimicking supernova explosions thought to be the dominant turbulence source. This work extends our previous study where we studied turbulence in a non-rotating, uniform environment. We find that the galaxy rotation does not make a significant difference in the turbulence level at saturation, since the associated shear velocity is much smaller than the explosion velocity. We analyze the properties of turbulence in our models and compare them with those from the uniform-density models. We also discuss the astrophysical implication of our findings.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.18-20
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• 1994

The axisymmetric variational approach employing localized functional is applied to calculate the leakage magnetic field from an induction heating system consisting of an exciting coil and a conducting circular plate. The open boundary is treated by introducing the exterior functional which is representated using the spherical fundamental solutions. For the application to the voltags source problems, the currents on the exciting coil is treated as unknowns. Our results are compared with the previous results, which showed good agreements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.200-204
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• 2005

The use of beamforming method and de-Dopplerization technique was applied in studying the rotating sound sources. Acoustic analysis of a moving sound source required that the measured sound signals be do-Dopplerized and restored as of the original emission signals. Two main issues of the signal reconstruction in time domain are addressed herein: First, to remove Doppler effect from the measured data and to restore the original emission data of the moving source. The difference of the time domain beamforming from the frequency domain beamforming was mentioned. Also, the time domain beamforming method is deployed in the test and the comparisons were made to the frequency domain results. The time domain signal reconstruction was numerically simulated prior to the application. To validate the de-Dopplerization Performance, the rotating Point sources were examined and localized by the use of a phased array of microphone. The application of prop-rotor was conducted in a hovering condition. The results of reconstructing time signals of rotating sources and its locations were shown in the power distribution maps. In the prop-rotor measurements, the acoustic source locations were successfully verified in varying positions for different frequencies of interest.

• Smart Structures and Systems
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• v.29 no.6
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• pp.777-783
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• 2022

Even though several deep learning-based methods have been applied in the field of acoustic source localization, the previous works have only been conducted using the two-dimensional representation of the beamforming maps, particularly with the planar array system. While the acoustic sources are more required to be localized in a spherical microphone array system considering that we live and hear in the 3D world, the conventional 2D equirectangular map of the spherical beamforming map is highly vulnerable to the distortion that occurs when the 3D map is projected to the 2D space. In this study, a 3D deep learning approach is proposed to fulfill accurate source localization via distortion-free 3D representation. A target function is first proposed to obtain 3D source distribution maps that can represent multiple sources' positional and strength information. While the proposed target map expands the source localization task into a point-wise prediction task, a PointNet-based deep neural network is developed to precisely estimate the multiple sources' positions and strength information. While the proposed model's localization performance is evaluated, it is shown that the proposed method can achieve improved localization results from both quantitative and qualitative perspectives.

• Journal of Korea Multimedia Society
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• v.3 no.6
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• pp.633-642
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• 2000

This paper proposes a dominant source-based tree (DSBT) that constructs a localized multicast routing tree for dynamic multicasting without rerouting. To constrain end-to-end delays a multicast tree needs to be reconstructed when a new node joins the group due to additive tree constraint. In DSBT, a multicast group G is expressed by a (DS, NCM) pair, where DS is a dominant source address and NCM is a normalized cost margin. A node wishing to participate in a group selects a path that complies with NCM toward DS such that the end-to-end cost is constrained without any rerouting. Simulation results show that the proposed method performed better in terms of the overall tree cost compared with the Nave algorithm and in terms of the end-to-end delays between any two members compared with the Greedy algorithm.

• Journal of the Korean Professional Engineers Association
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• v.45 no.3
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• pp.36-39
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• 2012

Roof gardens/Rooftop farm are most often found in urban environments. Plants have the ability to reduce the overall heat absorption of the building which then reduces energy consumption. Plant surfaces however, as a result of transpiration do not rise more than $4-5^{\circ}C$ above the ambient and are sometimes cooler. As Urban agriculture in an accessible rooftop farm, space becomes available for localized small-scale urban agriculture, a source of local food production. An urban garden can supplement the diets of the community it feeds with fresh produce and provide a tangible tie to food production.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.12
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• pp.1338-1346
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• 2004

The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to de-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 frequencies of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. It is shown that the forward propagation method gives better performance in locating source position than the backward propagation method.