• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.371-378
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• 2005

The objective or this paper is to measure the in-plane vibration intensity of a beam with a damped end that means the magnitude and direction of vibration power. Three experimental methods have been implemented to measure the in-plane vibration intensity over the beam. The first method is the accelerometer array method using two accelerometers. The second method is the frequency response function method using the only one accelerometer. The third method is the reference accelerometer method using a fixed reference accelerometer and another moving accelerometer. Those methods have been used to measure the spatial distribution of in-plane vibration intensity over the beam. The results obtained with those methods have been compared with each other. The results have been compared with an input power. It showed that the frequency response function method and the reference accelerometer method as well as the accelerometer array method can be effectively used to measure the in-plane vibration intensity in beams.

• Journal of the HCI Society of Korea
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• v.1 no.2
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• pp.27-33
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• 2006

This paper presents a new approach to translation and rotation invariant feature extraction for image texture retrieval. For the rotation invariant feature extraction, we invent angular projection along angular frequency in Polar coordinate system. The translation and rotation invariant feature vector for representing texture images is constructed by the averaged magnitude and the standard deviations of the magnitude of the Fourier transform spectrum obtained by the proposed angular projection. In order to easily implement the angular projection, the Radon transform is employed to obtain the Fourier transform spectrum of images in the Polar coordinate system. Then, angular projection is applied to extract the feature vector. We present our experimental results to show the robustness against the image rotation and the discriminatory capability for different texture images using MPEG-7 data set. Our Experiment result shows that the proposed rotation and translation invariant feature vector is effective in retrieval performance for the texture images with homogeneity, isotropy and local directionality.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.1
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• pp.70-75
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• 2007

In order to mitigate the problems in storage space and network bandwidth for the full CD quality audio with 44.1 kHz sampling rate, current existing digital audio is always restricted by sampling rate and bandwidth. This kind of restriction normally can be resolved by using low bit rate audio codec such as MP3, OGG, and AAC. However it suffers a major problem such as a loss of high frequency fidelity. This high frequency loss will reproduce only the band-limited low-frequency part of audio in the standard CD-quality audio. In general, the high frequency contents of audio have lots of information such as localization and ambient information, and bright nature of audio. The purpose of this paper is to implement on ARM platform system that can effectively estimate and compensate the missing high frequency contents of MP3 audio. From the experimental results with spectrum analysis and listening test, we confirm the superiority of the proposed algorithms for MP3 audio quality enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1622-1630
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• 2015

In this study, we used EBG(electromagnetic band gap) reflector to change bi-directional radiation of circular polarization into uni-directional radiation of equiangular spiral antenna. When the height of spiral arm from EBG reflector is 0.07 wavelength of the lowest operating frequency, the axial ratio of the circular polarization was deteriorated. In this paper, we analyzed the magnitude and the time phase difference of $E_{\theta},E_{\phi}$ that generates right hand circle polarization that is co-polarization at +z direction and proposed the improving condition for axial ratio at all related frequency range. As a result, we obtained that the axial ratio was below 3[dB] at range of 3 ~ 10[dB], the gain was improved about 3[dB] with comparison to bi-directional radiation at free space, and $S_{11}$ was below -10[dB] at all related frequency range.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.167-173
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• 2006

Ionosphere is the largest error source on propagation of GPS signals. Dual frequency (L1,L2) GPS receiver can be effectively able to eliminate the ionosphere error by using linear combination of two frequencies, but the single frequency receiver (L1) have to compute the ionosphere error. In this research, we developed the new ionospheric model with $1^{\circ}$ by $1^{\circ}$ spatial resolution based on the grid from using 9 GPS reference stations which have been operated by KASI (Korea Astronomy and Space Science Institute) and computed TEC (Total Electron Contents) over South Korea by epoch. This paper gives the positioning results of Klobuchar model with that of a newly developed KASI regional ionospheric model and shows the positioning precision of the KASI regional ionospheric model along with TEC variation of ionosphere.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1457-1467
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• 2015

Depending on the type of Tx-Rx pairs, VHF Data Exchange System (VDES) for maritime communication is expected to employ the different frequency channels. Load imbalance between the different channels turns out to be a critical problem for the multi-hop communication using Ad-hoc Self-Organizing TDMA (ASO-TDMA) MAC protocol, which has been proposed to provide the connectivity between land station and remote ship stations. In order to handle the inter-channel load imbalance problem, we consider a model of the stochastic geomety in this paper. After analyzing the spatial reuse efficiency in each hop region by the given model, we show that the resource utility can be maximized by balancing the inter-channel traffic load with optimal resource allocation in each hop region.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.70-75
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• 2000

In the seismic migration, Kirchhoff and reverse time migration are used in general. In the reverse time migration using wave equation, two-way and one-way wave equation are applied. The approach of one-way wave equation uses approximately computed downward continuation extrapolator, it need tess amounts of calculations and core memory in compared to that of two-way wave equation. In this paper, we applied one-way wave equation to pre-stack reverse time migration. In the frequency-space domain, forward propagation of source wavefield and back propagration of measured wavefield were executed by using monochromatic one-way wave equation, and zero-lag cross correlation of two wavefield resulted in the image of subsurface. We had implemented prestack migration on a massively parallel processors (MPP) CRAYT3E, and knew the algorithm studied here is efficiently applied to the prestck migration due to its suitability for parallelization.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.1
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• pp.100-108
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• 2008

This paper proposes a method of adaptively generating a gait pattern of biped robot. The gait synthesis is based on human's gait pattern analysis. The proposed method can easily be applied to generate the natural and stable gait pattern of any biped robot. To analyze the human's gait pattern, sequential images of the human's gait on the sagittal plane are acquired from which the gait control values are extracted. The gait pattern of biped robot on the sagittal plane is adaptively generated by a genetic algorithm using the human's gait control values. However, galt trajectories of the biped robot on the sagittal Plane are not enough to construct the complete gait pattern because the bided robot moves on 3-dimension space. Therefore, the gait pattern on the frontal plane, generated from Zero Moment Point (ZMP), is added to the gait one acquired on the sagittal plane. Consequently, the natural and stable walking pattern for the biped robot is obtained.

• Journal of Soil and Groundwater Environment
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• v.9 no.3
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• pp.1-11
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• 2004

To evaluate the applicability of dielectric constant measurement method on the geoenvironmental investigation of subsurface contaminated by landfill leachate, the analysis on dielectric characteristics of sand containing contaminated pore water by landfill leachate was performed. The separate real and imaginary parts of dielectric constant were investigated in the frequency range of 75kHz to 12MHz. The real part of dielectric constant increased at the lower frequency wherea the real part of dielectric constant decreased at the higher frequency as the concentration of leachate increased. These results can be explained by the frequency dependence of space charge polarization and orientation polarization. The imaginary part of dielectric constant on the contaminated sand with leachate increased with their concentration for whole frequency range. These results are caused by the increase of energy loss due to the enhancement of conduction in soil with leachate concentration. The results in this study indicate that the dielectric constant measurement method has potential in evaluating the contaminated soil and pore water by landfill leachate.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.447-454
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• 2007

본 논문에서는 사용자의 가상환경 내의 위치 정보에 대한 감각을 향상시키는 방법론으로서 햅틱 피드백(haptic feedback)과 사운드 피드백(sound feedback)의 모달리티를 활용한 그리드(grid)를 제안한다. 제안된 그리드는 사용자의 3차원 공간 내의 움직임(explorative procedure)에 추가적인 비 시각적인(non-visual) 위치정보 피드백을 부여하는데 그 목적을 두고 있다. 햅틱 모달리티를 활용한 3차원 그리드는 SensAble사의 PHANTOM(R) Omni$^{TM}$ 를 활용하여 설계되었으며, 사운드 모달리티를 활용한 경우 저주파 배경음의 주파수 특성(frequency characteristics of sound source)을 사용자 손의 공간 좌표값에 근거하여 재생 시의 표본 추출 비율(sampling rate)를 연속적으로 바꾸는 방식으로 설계되었다. 이러한 공간 그리드는 두 모달리티 각각의 독립적인 제시 및 동시 제시/제거를 통해 평가되었으며, 동시 제시의 경우 두 모달리티간의 어긋남(cross-modal asynchrony)이 없도록 설계되어 사용자의 공간 작업 시 모달리티간의 조화 (manipulating congruency)를 확보할 수 있도록 하였다. 실험을 통해 얻어진 결과는 그것의 통계적 유의미성을 분석하기 위해 다원변량분석과 사후검증(Turkey. HSD)을 거쳐 해석이 되었다. 공간 내 특정 좌표 선택을 기준으로 하는 그리드의 사용자 평과 결과, 3차원 내의 움직임에 대해 햅틱 및 사운드 피드백의 비 시각적 피드백은 사용자의 공간 작업의 오차를 줄여 주고 있음이 확인되었다. 특히 시각적인 정보만으로 확인하기 어려운 Z축 상의 움직임은 그리드의 도움으로 그 오차정도가 50% 이상 줄어 드는 것으로 확인되었다(F=19.82, p<0.01). 이러한 시각적 정보를 보존하는 햅틱, 사운드 피드백 방식을 HCI의 중요한 요소인 사용성과 유용성과 연관시켜 MMHCI(multimodal human-computer interaction) 방법론으로의 적용 가능성을 검토해 본다.