• The Korean Journal of Applied Statistics
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• v.21 no.5
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• pp.801-811
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• 2008

Modeling financial phenomena with diffusion processes is a commonly used methodology in the area of modern finance. Recently, various types of diffusion models have been suggested to explain the specific financial processes, and their related inference methodology have been also developed. In particular, likelihood methods for the efficient and accurate inference have been explored in various ways. In this paper, we review the mathematical properties of an approximated likelihood method, which is obtained by linearizing the drift coefficient of a diffusion process.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1982.05a
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• pp.13.1-13
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• 1982

Cysticercosis is not likely to be the first diagnosis the otologist has in the head and neck area. The fact that this disease may present a diagnostic and therapeutic problem is illustrated by one case, appearing in the face of right side. The local finding of a soft nontender mass, the typical calcifications in the soft tissues visible on roentgenograms, and the histopathological findings are described and illustrated. Attention is drawn to the fact that cerebral cysticercosis, which is a very grave disease, may cause tinnitus, nystagmus, and hearing disturbances. Recently, the authors have experienced a case of cysticercosis on the face in a 24-year-old male patient. We present this case with a brief review of the literatures.

• Clinical and Experimental Pediatrics
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• v.49 no.2
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• pp.208-211
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• 2006

Dyke-Davidoff-Masson Syndrome (DDMS) is a rare condition characterized by asymmetry of cerebral hemispheric growth with atrophy on one side, ipsilateral compensatory osseous hypertrophy, and contralateral hemiparesis. We experienced a 17 month-old male who presented with left focal clonic or tonic-clonic seizures accompanied by left hemiparesis and developmental delay. Brain MRIs demonstrated progressive atrophy of the right cerebral hemisphere with dilatation of the lateral ventricle, expansion of the ipsilateral frontal sinus with calvarial thickening, and elevation of the petrous pyramid and orbital roof. Brain SPECT showed a decreased volume of the right hemisphere with reduced blood flow. We therefore report a case of DDMS with a review of the literature.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.476-476
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• 2023

해저면에 놓인 물체는 주변의 국소 흐름 변화에 의해 해저면 전단응력이 국부적으로 변화하는 과정에서 침식과 퇴적이 발생하게 되면서 해저면 지형의 변화에 의해 움직임이 발생한다. 이때 물체의 크기, 무게, 밀도와 형상에 따라 구름, 미끄러짐, 액상화 현상 또한 동반 될 수 있다. 본 연구에서는 해저면에 놓인 물체의 시간변화에 따른 매몰심 변화를 예측하고자 하였다. 물체는 원형 단면의 실린더 형태로 고려했다. 시간변화에 따른 매몰심 변화를 평형 매몰심으로의 접근속도에 관련된 인수와 매몰심 변화량으로 기본방적식을 구성하였고, 이를 유한 차분식으로 수립하였다. 최종 평형 매몰심 계산은 Friedrichs et al.(2016)의 경험식을 사용하였다. 앞선 연구에서 김효섭 등(2016)은 시간에 따른 세굴심 변화 모델 STEP-K를 제시한 바 있다. 시간변화에 따른 연직방향 실린더 주변에서의 국소세굴심을 예측하는 기법으로, 해저면에 놓인 수평방향 물체 주변의 매몰심 발달을 예측하기 위해 매몰 발생에 대한 시간의 척도를 새롭게 제안하였다. STEP-K에서 사용했던 KC수를 대신해 흐름-단주기 파랑 공조시의 해저면의 전단응력을 대표할 수 있는 대표전단응력을 사용할 수 있게 하였다. 보정계수를 통해 현장 또는 실험실 단위의 자료가 가용한 경우 식을 보정할 수 있다. 제안한 매몰심 예측기법은 Elmore et al.(2007)의 매몰실험 관측자료를 활용하여 보정하였다. 결과적으로 보정자료에 대한 시간에 따른 매몰심의 변화양상을 잘 재현하였으며, 향후 우리나라 해양환경 자료를 활용한 보정을 통해 적용성을 높일 수 있을 것으로 기대된다.

• Journal of the Korean Society of Radiology
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• v.81 no.2
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• pp.418-422
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• 2020

Serous cystic neoplasms of the pancreas are usually benign, with a low malignant potential. Herein, we report a case of malignant serous cystic neoplasm of the pancreas treated with subtotal pancreatectomy, which progressed to local recurrence and metachronous hepatic metastasis during the regular follow-up period.

• Proceedings of the Korea Information Processing Society Conference
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• 2024.05a
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• pp.749-752
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• 2024

연합학습은 클라이언트가 중앙 서버에 원본 데이터를 주지 않고도 학습할 수 있도록 설계된 분산된 머신러닝 방법이다. 그러나 클라이언트와 중앙 서버 사이에 모델 업데이트 정보를 공유한다는 점에서 여전히 추론 공격(Inference Attack)과 오염 공격(Poisoning Attack)의 위험에 노출되어 있다. 이러한 공격을 방어하기 위해 연합학습에 차분프라이버시(Differential Privacy)를 적용하는 방안이 연구되고 있다. 차분 프라이버시는 데이터에 노이즈를 추가하여 민감한 정보를 보호하면서도 유의미한 통계적 정보 쿼리는 공유할 수 있도록 하는 기법으로, 노이즈를 추가하는 위치에 따라 전역적 차분프라이버시(Global Differential Privacy)와 국소적 차분 프라이버시(Local Differential Privacy)로 나뉜다. 이에 본 논문에서는 차분 프라이버시를 적용한 연합학습의 최신 연구 동향을 전역적 차분 프라이버시를 적용한 방향과 국소적 차분 프라이버시를 적용한 방향으로 나누어 검토한다. 또한 이를 세분화하여 차분 프라이버시를 발전시킨 방식인 적응형 차분 프라이버시(Adaptive Differential Privacy)와 개인화된 차분 프라이버시(Personalized Differential Privacy)를 응용하여 연합학습에 적용한 방식들에 대하여 특징과 장점 및 한계점을 분석하고 향후 연구방향을 제안한다.

• Korean Journal of Cognitive Science
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• v.11 no.2
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• pp.53-58
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• 2000

This paper reconstructs local region of a facial expression image from extracted feature points of facial expression image using FCM(Fuzzy C-Meang) clustering algorithm with Gabor wavelets. The feature extraction in a face is two steps. In the first step, we accomplish the edge extraction of main components of face using average value of 2-D Gabor wavelets coefficient histogram of image and in the next step, extract final feature points from the extracted edge information using FCM clustering algorithm. This study presents that the principal components of facial expression images can be reconstructed with only a few feature points extracted from FCM clustering algorithm. It can also be applied to objects recognition as well as facial expressions recognition.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.97-102
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• 2003

Multi-channel images of 11-MUA(11-Mercaptoundecanoic acid) and 11-MUOH(11-Mercaptoundecanol) self-assembled monolayers were obtained by using two-dimensional surface plasmon resonance (SPR) absorption. The patterning process was simplified by exploiting direct photo-oxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter in the visible region, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each point on the sensor surface (at a fixed incident angle) enables us to discriminate the monolayer thickness in nanometer scale. Furthermore, there is no signal degradation such as photo bleaching or quenching, which are common in the detection methods based on fluorescence.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.3
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• pp.96-104
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• 2009

In this paper, we propose a no-reference objective Quality assessment metrics of image. The blockiness and blurring of edge areas which are sensitive to the human visual system are modeled as step functions. Blocking and blur metrics are obtained by estimating local visibility of blockiness and edge width, For the blocking metric, horizontal and vertical blocking lines are first determined by accumulating weighted differences of adjacent pixels and then the local visibility of blockiness at the intersection of blocking lines is obtained from the total difference of amplitudes of the 2-D step function which is modelled as a blocking region. The blurred input image is first re-blurred by a Gaussian blur kernel and an edge mask image is generated. In edge blocks, the local edge width is calculated from four directional projections (horizontal, vertical and two diagonal directions) using local extrema positions. In addition, the kurtosis and SSIM are used to compute the blur metric. The final no-reference objective metric is computed after those values are combined using an appropriate function. Experimental results show that the proposed objective metrics are highly correlated to the subjective data.

• Korean Journal of Biological Psychiatry
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• v.10 no.2
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• pp.168-176
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• 2003

Objectives:We investigated the characteristics of P300 generators in obsessive-compulsive disorder(OCD) patients by using voxel-based statistical parametric mapping of current density images. Methods:P300 generators, produced by a rare target tone of 1500Hz under a frequent non-target tone of 1,000Hz, were measured in 15 right-handed OCD patients and 15 controls. Low Resolution Electromagnetic Tomography(LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Statistical parametric mapping(SPM) was applied for the statistical analysis. Results:We found that both groups had the mean current density of P300 in the parietal, temporal and prefrontal lobe. There was a trend for decreased current density in the prefrontal area in OCD patients. The statistical comparison showed current density increase in the supraparietal area, a statistically significant longer P300 latency and a trend for reduced P300 amplitude in OCD patients. Conclusion:It suggests that P300 source of both groups exists in multiple brain regions at the same time. And both groups had no statistically significant differences in the current density of P300 except for increased current density in the supraparietal area in OCD patients. But, considering the statistically significant longer P300 latency, a trend for reduced P300 amplitude and relative mean current density reduction in the prefrontal area in OCD patients, this study suggests that the frontal lobe may have a reduced normal inhibitory process in OCD patients.