• Journal of The Korean Astronomical Society
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• v.35 no.3
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• pp.143-149
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• 2002

In this paper we present a methodology to derive the temporal change of the magnetic shear angle from a series of vector magnetograms, with a high time cadence. This method looks for the minimum change of the shear angle between a pair of magnetograms, free from the $180^{\circ}$ ambiguity, and then accumulates this change over many successive pairs to derive the temporal change of magnetic shear. This methodology will work well if only the successive magnetograms occurred in an active region are well aligned and its helicity sign is reasonably determined. We have applied this methodology to a set of vector magnetograms of NOAA Active Region 9661 on October 19, 2001 by the new digital magnetograph at the Big Bear Solar Observatory (BBSO). For this work we considered well aligned magnetograms whose cross-correlation values are larger than 0.95. As a result, we have confirmed the recent report of Wang et al. that there was the abrupt shear change associated with the X1.6 flare. It is also demonstrated that the shear change map can be an useful tool to highlight the local areas that experienced the abrupt shear change. Finally, we suggest that this observation should be a direct support of the emergence of sheared magnetic fields.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.14-14
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• 2022

홍수시 하천의 유량측정은 매우 어렵고 위험하며 많은 노력과 비용이 드는 작업이다. 이러한 홍수시 유량측정을 위해 영상을 이용하여 하천의 표면유속을 측정하고 여기서 유량을 산정하는 기술은 하천 유량 측정의 자동화와 안전한 유량 측정을 위한 대안으로 크게 주목받고 있다. 그런데, 유속측정을 위해 20~40초 정도의 영상의 평균유속을 구하고자 하면, 방대한 양의 영상처리에 많은 시간이 소요되어 실시간 측정이나 분석이 어렵게 된다. 본 연구는 영상을 이용하여 홍수시 하천의 유량을 실시간으로 측정하기 위해 투영변환과 시공간영상 분석법을 적용하여 실용적인 표면영상유속계를 개발하기 위한 것이다. 이를 위해, 3차원 투영변환(11변수 변환)을 적용하여 측정선과 유속측정점의 위치를 영상내에 특정하고 이 부분만을 추출하여 시공간 영상(spatio-temporal images)으로 구성하고, 이 시공간 영상을 분석하여 유속과 유량을 산출하는 기법을 개발하였다. 즉, 하천의 주흐름 방향의 유속만을 산정하도록 하여 영상의 분석에 소요되는 계산량과 계산시간을 단축하였다. 또한, 시공간 분석과정도 기존의 CASTI (Correlation Analysis of Spatio-Temporal Images)를 훨씬 간단하고 빠르게 계산할 수 있도록 개량하였다. 그 결과 영상의 유속분석 및 유량산정에 소요되는 시간을 획기적으로 줄일 수 있었으며, 실시간으로 유량 측정이 가능하게 되었다.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.661-666
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• 2000

Near-wake flow field of a circular cylinder is studied by means of a cinematic PIV system with high sampling rate and large internal memory block. Experiments are conducted in a closed-cycle water tunnel system and a cross-correlation algorithm in conjunction with FFT (Fast Fourier Transform) analysis and an offset correlation technique is used for vector processing. With the help of very high sampling frequency compared to the shedding frequency, it is possible to obtain phase-averaged information of the three-dimensional wake, even though the shedding is not forced but natural. Phase-locked vortical structures observed simultaneously from the spanwise and cross-stream planes are displayed in the wake-transition regime where fine-scale secondary vortices have a spanwise wavelength or around one diameter. Spatial relations and temporal evolutions of the primary Karman vortex and the secondary vortex are also discussed schematically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.945-950
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• 2001

Floor impact noise has been evaluated by investigating the temporal and spectral characteristics of the noise. The noises generated by different impactors were analyzed to find out whether there is any correlation with the factors of ACF /IACF (Autocorrelation Function/Inter-aural Cross-correlation Function) [1] and Zwicker parameters [2]. Experiments were undertaken to compare the objective and subjective parameters of the floor impact noises generated by a bang/tapping machine, a rubber ball [3], and a walker. As a result, it was found that $\phi$ (0) and IACC extracted from ACF/IACF, and Loudness, Unbiased Annoyance from Zwicker parameters showed high correlation with subjective evaluations of loudness concerning floor impact noises. In addition, it was revealed that jumping is similar to the ball.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.26-31
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• 2001

긍/부정 선택 실험에서 나타나는 뇌파 변화를 연구하였다. 서로 다른 위치에서 측정된 뇌파의 시공간적 상호관계를 정량화하는 변수로, 시간영역에서 계산하기 용이한 동기율(synchronization rate), 편향성(synchronization rate), 편향성(polarity), 상호상관(cross-correlation) 등의 변수를 도입하여, 긍/부정 선택 순간의 뇌파 변화를 살펴보았다. 좌우 전전두엽(Fp1, Fp2)에서 특정된 뇌파를 사용하여 계산한 동기율, 편향성의 평균과 요동폭, 상호상관 등은, 선택 순간 근처에서, 평상시에 뇌파와 통계적으로 유의미한 차이를 보였다.

• The Journal of Korea Robotics Society
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• v.6 no.1
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• pp.18-26
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• 2011

This paper presents a method, Exposure Controlled Temporal Filtering (ECF), applied to visual motion tracking, that can cancel the temporal aliasing of periodic vibrations of cameras and fluctuations in illumination through the control of exposure time. We first present a theoretical analysis of the exposure induced image time integration process and how it samples sensor impingent light that is periodically fluctuating. Based on this analysis we develop a simple method to cancel high frequency vibrations that are temporally aliased onto sampled image sequences and thus to subsequent motion tracking measurements. Simulations and experiments using the 'Center of Gravity' and Normalized Cross-Correlation motion tracking methods were performed on a microscopic motion tracking system to validate the analytical predictions.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.12-14
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• 2005

In this paper, we proposed an temporal error concealment (EC) using the proposed boundary matching method and the adaptive block matching method. The proposed boundary matching method improves the spatial correlation of the macroblocks (MBs) by reusing the pixels of the concealed MB to estimate a motion vector of a error MB. The adaptive block matching method inspects the horizontal edge and the vertical edge feature of a error MB surroundings, and it conceals the error MBs in reference to more stronger edge feature. This improves video quality by raising edge connection feature of the error MBs and the neighborhood MBs. In particular, we restore a lost MB as the unit of 8${\times}$16 block or 16${\times}$8 block by using edge feature from the surrounding macroblocks. Experimental results show that the proposed algorithm gives better results than the conventional algorithms from a subjective and an objective viewpoint.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.11
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• pp.673-679
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• 2005

This Paper presents the 3D wavelet transformation based video compression system, which possesses the capability of progressive transmission by increasing resolution and increasing rate for multimedia applications. The 3D wavelet packet based video compression system removes the temporal correlation of the input sequences using the motion compensation filter and decomposes the spatio-temporal subband using the spatial wavelet packet transformation. The proposed system allocates the higher bit rate to the low frequency image of the 3D wavelet sequences and improves the 0.49dB PSNR performance of the reconstructed image in comparison with that of H.263. In addition to the limitation on the propagation of the motion compensation error by the 3D wavelet transformation, the proposed system progressively transmits the input sequence according to the resolution and rate scalability.

• Journal of radiological science and technology
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• v.27 no.3
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• pp.13-18
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• 2004

In most patients with facial palsy after temporal bone injury, temporal bone High Resolution CT revealed direct or indirect facial nerve canal involvement, and in complete palsy severe degeneration groups, there were direct findings in most cases. Author believe that meticulous analysis and symptom correlation of the fracture patterns seen in facial canal injury in patients with traumatic facial nerve palsy is helpful for treatment planning and prognosis.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.163-167
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• 2003

Based on the transient finite difference solution of Richards' equation, an infiltration model is developed to analyze temporal variation of precipitation recharge in the region of monsoon climates. Simulation results obtained by using time series data of 20-year daily precipitation and pan evaporation indicate that a linear relationship between the annual precipitation and the annual recharge holds for the soils under the monsoon climates with varying degrees of the correlation coefficient depending on the soil types. A sensitivity analysis reveals that the water table depth has little effects on the recharge for the sandy soil, whereas, for the loamy and silty soils, rise of the water table at shallow depths causes increase of evaporation by approximately 100㎜/yr and a corresponding decrease in recharge. A series of simulations for two-layered soils illustrate that the amount of recharge is dominantly determined by the soil properties of the upper layer, although the temporal variation of recharge is affected by both layers.