• KIPS Transactions on Software and Data Engineering
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• v.2 no.8
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• pp.579-588
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• 2013

This paper proposes an effective watermarking approach for copyright protection of fire video images. The proposed watermarking approach efficiently utilizes the inherent characteristics of fire data with respect to color and texture by using a gray level co-occurrence matrix (GLCM) and fuzzy c-means (FCM) clustering. GLCM is used to generate a texture feature dataset by computing energy and homogeneity properties for each candidate fire image block. FCM is used to segment color of the fire image and to select fire texture blocks for embedding watermarks. Each selected block is then decomposed into a one-level wavelet structure with four subbands [LL, LH, HL, HH] using a discrete wavelet transform (DWT), and LH subband coefficients with a gain factor are selected for embedding watermark, where the visibility of the image does not affect. Experimental results show that the proposed watermarking approach achieves about 48 dB of high peak-signal-to-noise ratio (PSNR) and 1.6 to 2.0 of low M-singular value decomposition (M-SVD) values. In addition, the proposed approach outperforms conventional image watermarking approach in terms of normalized correlation (NC) values against several image processing attacks including noise addition, filtering, cropping, and JPEG compression.

• Geophysics and Geophysical Exploration
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• v.6 no.3
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• pp.119-125
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• 2003

The small-loop electromagnetic (EM) technique has been used successfully for many geophysical investigations, particularly for shallow engineering and environmental surveys. In conventional small loop EM operating at small induction numbers, geometric sounding has been widely used because the depth of penetration of EM energy depends only on the source-receiver separation. Recently developed small loop EM system, however, measures the secondary magnetic field, $H^S$, at multiple frequencies with a fixed source-receiver separation and frequency sounding is tried actively. In this study, we analyzed the behavior of in-phase and quadrature components of ${H^S}_z$, for horizonal coplanar (HCP) configuration over two-layer models. Through this theoretical analysis, it was found that the in-phase component of ${H^S}_z$ is more suitable for frequency sounding than the quadrature component. But, the in-phase component of ${H^S}_z$ is too small to measure, especially in resistive and noisy environment like Korea. Using the fact that the quadrature component is much greater than the in-phase component and the difference of quadrature component of ${H^S}_z$ measured at two frequencies shows the same behavoir as the in-phase component, we suggested an alternative frequency sounding technique. Also, we defined an apparent conductivity, which reflects well the conductivity of subsurface layers.

• Journal of Oral Medicine and Pain
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• v.22 no.1
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• pp.31-44
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• 1997

저자들은 악관절내장증의 증상과 징후의 객관적 평가법을 개발하기 위하여 서울대학교치과 병원 구강진단과 악안면동통진료실을 내원한 환자중 좌우 양 관절중 한 관절 이상의 관절에 악관절내장이 있는 남자 8명(평균연령 19.9$\pm$2.9세), 여자 34명(평균연령:32.8$\pm$11.8세) 총 42명(84개 관절)에 대하여 VAS 및 압통역치 측정, 악관절조영술, 골신티그래피 검사 및 악관절 활액의 분석을 시행하였다. 악관절 동통의 심도는 VAS로 측정을 하였으며 PPT는 electronic algometer로 평가를 하였다. 악관절조영사진을 얻기 직전 활액을 채취하였으며 그 성분중 Hyaluronic acid, 총단백질, IgG, IgM과 albumin을 분석하여 그 상관관계를 분석한 결과 다음과 같은 결론을 얻었다. 1. 악관절 내장증으로 내원한 환자 42명, 총 84개 관절중, 무통성이고 관절잡음이 없는 경우가 7개 관절, 무통성이고 단순관절음만 존재하는 경우가 18개 관절, 동통 및 단순관절음이 존재하는 경우가 18개 관절, 간헐적인 폐구 과두걸림이 있는 경우가 11개 관절, 급성 폐구성 과두걸림의 경우가 11개 관절, 만성 폐구성 과두걸림의 경우가 3개 관절, 퇴행성 관절질환이 존재하는 경우가 16개 관절이었다. 2. 연구대상중 18명의 환자, 총 36개 관절에 대한 골 신티그래피 검사 결과, 활동성으로 나타난 경우가 33개 관절이었고 이중 23개 관절이 동통성이었으며, 활동 상태 관절의 VAS 항목과 압통역치 항목 및 여러 검사 항목들은 비활동 상태 관절의 항목과 유의한 차이를 나타내지 않았다. 3. 악관절내장의 진행정도에 따른 악관절부위의 동통의 측정에 있어서는 압통역치의 측정보다는 VAS에 의한 방법이 더 유용하며 특히, 후방부의 촉진시에 유의한 정보를 얻을 수 있었다. 4. 악관절 내장즈으이 진행 단계에 따라, VAS항목과 압통역치 항목을 비교해 본 결고, 주기적인 과두걸림(II) 단계에서 가장 높은 VAS 수치와 가장 낮은 압통역치를 나타내었으며 상방 촉진시 VAS 항목에서 주기적인 과두걸림(II) 단계와 증상 및 징후가 없는(0) 단계 사이와 후방 촉진시 VAS 항목에서 주기적인 과두걸림(II) 단계 및 퇴행성 관절 질환(V) 단계와 증상 및 징후가 없는(0) 단계 사이에서만 유의성을 나타내었다. 5. 활액내 총단백질량, albumin 량, IgG 및 IgM 농도는 악과？ㄹ 내장증의 진행에 따라 유의성을 나타내지는 않았으나 퇴행성 관절 질환(V) 단계에서 증가되는 양상을 나타내었다. 6. 활액내 hyaluronic acid의 농도는 악관절 내장증의 진행에 따라 유의성을 나타내지는 않았으나 만성 폐구성 과두걸림(IV) 단계에서 감소되는 양상을 나타내었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.1
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• pp.56-59
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• 2003

The incident of false aneurysm of internal maxillary artery in the oral and maxillofacial region is known to be very rare. One case of false aneurysm in the internal maxillary artery is presented, which was experienced in our department. The etiology of this case is regarded as the mandibular condyle fracture, and/or iatrogenic trauma during open reduction. Clinically, there were systolic bruit on auscultation, pulsation and massive bleeding during operation. The lesion was finally diagnosed with angiography and treated by embolization procedure. False aneurysm can cause so massive bleeding as to threat the life of the patients. Therefore accurate diagnosis and treatment is very important. Angiography enables the solid diagnosis for the clinical one. And as the embolization has many advantages over the ligation, it can be a good treatment method.

• Korean Journal of Optics and Photonics
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• v.31 no.2
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• pp.59-70
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• 2020

We discuss a modified numerical model based on the Monte Carlo radiative transfer (MCRT) method, i.e., the MCRT matrix method, for the analysis of atmospheric scattering effects in three-dimensional flash LIDAR systems. Based on the MCRT method, the radiative transfer function for a LIDAR signal is constructed in a form of a matrix, which corresponds to the characteristic response. Exploiting the superposition and convolution of the characteristic response matrices under the paraxial approximation, an extended computer simulation model of an overall flash LIDAR system is developed. The MCRT matrix method substantially reduces the number of tracking signals, which may grow excessively in the case of conventional Monte Carlo methods. Consequently, it can readily yield fast acquisition of the signal response under various scattering conditions and LIDAR-system configurations. Using the computational model based on the MCRT matrix method, we carry out numerical simulations of a three-dimensional flash LIDAR system operating under different atmospheric conditions, varying the scattering coefficient in terms of visible distance. We numerically analyze various phenomena caused by scattering effects in this system, such as degradation of the signal-to-noise ratio, glitches, and spatiotemporal spread and time delay of the LIDAR signals. The MCRT matrix method is expected to be very effective in analyzing a variety of LIDAR systems, including flash LIDAR systems for autonomous driving.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.342-347
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• 1999

As the waveguide width and the radius of curvature get smaller for the effort of monolithic fabrication of integrated photonic devices, the waveguide characteristics change significantly according to the change of the waveguide width or the radius of curvature. Especially, variation of the waveguide width due to fabrication process errors induces a phase error for each waveguide from the change of the propagation constant. Therefore, it is important to quantify these variation effects on the device characteristics for the design and fabrication of highly integrated photonic devices. Here, we analyze four different types of waveguides to get general characteristics in propagation constant change by utilizing the effective index method and the analytic solution method. Futhermore, the output characteristics of two AWG(Arrayed Waveguide Grating) devices are simulated by a highly-functional computer code. The simulated results have been found to be similar to the realistic device characteristics. The required fabrication error limit for the ridge-type InP-AWG device should be smaller than 0.02 ${\mu}{\textrm}{m}$ to get better channel crosstalk than-25 dB, while the required fabrication error limit for rib-type silica-AWG devices may be allowed up to 0.1 ${\mu}{\textrm}{m}$ to obtain better crosstalk than -30 dB.

• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.64-73
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• 2015

Recently, hydraulic fracturing is used in various fields and microseismic monitoring is one of the best methods for judging where hydraulic fractures exist and how they are developing. When locating microseismic events using single vertical well data, distances from the vertical array and depths from the surface are generally decided using time differences between compressional (P) wave and shear (S) wave arrivals and azimuths are calculated using P wave hodogram analysis. However, in field data, it is sometimes hard to acquire P wave data which has smaller amplitude than S wave because microseismic data often have very low signal to noise (S/N) ratio. To overcome this problem, in this study, we developed a grid search algorithm which can find event location using all combinations of arrival times recorded at receivers. In addition, we introduced and analyzed the method which calculates azimuths using S wave. The tests of synthetic data show the inversion method using all combinations of arrival times and receivers can locate events without considering the origin time even using only single phase. In addition, the method can locate events with higher accuracy and has lower sensitivity on first arrival picking errors than conventional method. The method which calculates azimuths using S wave can provide reliable results when the dip between event and receiver is relatively small. However, this method shows the limitation when dip is greater than about $20^{\circ}$ in our model test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.103-112
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• 2010

In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3GPP(3rd Generation Partnership Project) LTE(Long Term Evolution) FDD(Frequency Division Duplexing) / TDD(Time Division Duplexing) dual mode system. In general, PSS(Primary Synchronization Signal) correlation based estimation method and CP(Cyclic Prefix) correlation based tracking loop are applied for coarse and fine frequency synchronization in 3GPP LTE OFDMA(Orthogonal Frequency Division Multiple Access) system, respectively. However, the conventional coarse frequency synchronization method has performance degradation caused by fading channel and squaring loss. Also, the conventional fine frequency synchronization method cannot guarantee stable operation in TDD mode because of signal power difference between uplink and downlink subframe. Therefore, in this paper, we propose enhanced coarse and fine frequency synchronization methods which can estimate more accurately in multi-path fading channel and high speed channel environments and has stable operation for TDD frame structure, respectively. By computer simulation, we show that the proposed methods outperform the conventional methods, and verify that the proposed frequency synchronization method can guarantee stable operation in 3GPP LTE FDD/TDD dual mode downlink receiver.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.13-19
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based chemical sensor was developed on a $41^{\circ}YX\;LiNbO_3$ piezoelectric substrate for simultaneous measurement of $CO_2$ gas and relative humidity (RH) using a reflective delay line pattern as the sensor element. The reflective delay line is composed of an interdigital transducer (IDT) and several shorted grating reflectors. A Teflon AF 2400 and a hydrophilic $SiO_2$ layer were used as $CO_2$ and water vapor sensitive films. The coupling of mode (COM) modeling was conducted to determine optimal device parameters prior to fabrication. According to simulation results, the device was fabricated and then wirelessly measured using the network analyzer. The measured reflective coefficient $S_{11}$ in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. In the $CO_2$ and humidity testing, high sensitivity ($2^{\circ}/ppm$ for $CO_2$ detection and $7.45^{\circ}/%$RH for humidity sensing), good linearity and repeatability were observed in the $CO_2$ concentration ranges of $75{\sim}375ppm$ and humidity levels of $20{\sim}80%$RH. Temperature and humidity compensations were also investigated during the sensitivity evaluation process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2715-2720
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• 2014

Median filtering is very effective to remove impulse type noises, so it has been widely used in many signal processing applications. However, due to the time complexity of its non-linearity, median filtering is often used using a small filter window size. A lot of work has been done on devising fast median filtering algorithms, but most of them can be efficiently applied to input data with finite integer values like images. Little work has been carried out on fast 2-d median filtering algorithms that can deal with real-valued 2-d data. In this paper, a fast and simple median 2-d filter is presented, and its performance is compared with the Matlab's 2-d median filter and a heap-based 2-d median filter. The proposed algorithm is shown to be much faster than the Matlab's 2-d median filter and consistently faster than the heap-based algorithm that is much more complicated than the proposed one. Also, a more efficient median filtering scheme for 2-d real valued data with a finite range of values is presented that uses higher-bit integer 2-d median filtering with negligible quantization errors.