• 천문학회보
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• 제39권1호
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• pp.45.1-45.1
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• 2014

We present the results of a time series analysis of the long-term radio lightcurves of four blazars: 3C 279, 3C 345, 3C 446, and BL Lacertae. We exploit the data base of the University of Michigan Radio Astronomy Observatory (UMRAO) monitoring program which provides densely sampled lightcurves spanning 32 years in time in three frequency bands located at 4.8, 8, and 14.5,GHz. Our sources show mostly flat or inverted (spectral indices -0.5 < alpha < 0) spectra, in agreement with optically thick emission. All lightcurves show strong variability on all time scales. Analyzing the time lags between the lightcurves from different frequency bands, we find that we can distinguish high-peaking flares and low-peaking flares in accord with the classification of Valtaoja et al. (1992). The periodograms (temporal power spectra) of the observed lightcurves are consistent with random-walk powerlaw noise without any indication of (quasi-)periodic variability. The fact that all four sources studied are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권3호
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• pp.993-1014
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• 2021

This paper proposes a new image retrieval method called the 3D integrated multi-index to fuse SIFT (Scale Invariant Feature Transform) visual words with other features at the indexing level. The advantage of the 3D integrated multi-index is that it can produce finer subdivisions in the search space. Compared with the inverted indices of medium-sized codebook, the proposed method increases time slightly in preprocessing and querying. Particularly, the SIFT, contour and colour features are fused into the integrated multi-index, and the joint cooperation of complementary features significantly reduces the impact of false positive matches, so that effective image retrieval can be achieved. Extensive experiments on five benchmark datasets show that the 3D integrated multi-index significantly improves the retrieval accuracy. While compared with other methods, it requires an acceptable memory usage and query time. Importantly, we show that the 3D integrated multi-index is well complementary to many prior techniques, which make our method compared favorably with the state-of-the-arts.

• International Journal of Computer Science & Network Security
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• 제24권8호
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• pp.61-71
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• 2024

The dynamic nature of Online Social Networks (OSNs), especially on platforms like Twitter, presents challenges in identifying and responding to community attacks, particularly within Arabic content. The proposed integrated system addresses these challenges by achieving 91% accuracy in detecting real-time community event attacks while efficiently managing computational costs. This is accomplished through the use of specialized integrated approach clustering to detect both major and minor attacks. Additionally, the system leverages clustering algorithms, temporal modules, and social network graphs to identify events, map communities, and analyze online dynamics. An extensive parameter sensitivity analysis was conducted to fine-tune the algorithm, and the system's effectiveness was validated using a benchmark dataset, demonstrating substantial improvements in event detection.

• 정보과학회 논문지
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• 제42권3호
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• pp.390-398
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• 2015

공간 웹 객체는 웹 문서에 지리정보를 포함하고 있는 문서들을 말한다. 최근 스마트폰과 같은 장치의 발달로 인하여 공간 웹 객체를 생성하는 서비스가 많이 늘어났다. 트위터나 페이스북 같은 서비스에서는 사용자가 게시한 간단한 글이 게시한 위치정보와 함께 저장된다. 이러한 공간 웹 객체의 검색을 위해서는 공간 정보와 문자 정보를 동시에 이용하는 검색이 필요하다. 기존의 공간 웹 객체 검색 방식은 R트리와 역색인 파일(inverted file) 방법을 많이 사용했다. 하지만 이 방법은 인덱스를 구축하는데 많은 공간을 필요로 한다는 단점이 있다. 또한 검색하는 키워드가 많을 때는 효율적이지만, 검색하는 키워드가 적을 때는 비효율적이다. 본 논문에서는 쿼드 트리(quad-tree)와 패트리샤 트라이(patricia trie)를 이용하는 공간 웹 객체 검색 방식을 제안한다. 제안하는 기법은 검색하는 키워드가 적을 때 기존의 기법보다 좋다는 것을 보여준다. 또한 인덱스를 저장하는 공간이 기존의 기법보다 훨씬 적게 사용된다는 것을 실험을 통하여 증명하였다.

• 한국의상디자인학회지
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• 제21권2호
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• pp.95-108
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• 2019

This study aims to determine the characteristics of new senior women's torso shapes. The data was collected from the 7th Size Korea, which analyzed 412 women between the ages of 55-69. A factor analysis was performed based on 20 indices, including eight based on circumference, eight based on height and length measurements, and four based on torso flattening. The results of the factor analysis suggest five main factors: torso silhouette, longitudinal size of the body, torso flattening rate, abdominal shape, and posterior longitudinal size. The results of the cluster analysis suggest three overall types: Type 1 is the inverted triangular obese shape which is characterized by large breasts, small buttocks, a short height, and a forward-bending posture; Type 2 is the rectangular, slim shape which is characterized by a forward neck and a flat front and back of the torso, and is the most slender among the three types; Type 3 is the large rectangular, overall obese shape, which is characterized by a round shape with large breasts, waist, and buttocks, and a forward-bending posture with a protruding back, and this is the most obese type. According to the results of the cross-tabulation, women aged 55-59 showed no trend in body shape; women aged 60-64 showed an increases in the inverted triangular obese shape and the large rectangular, overall obese shape; women aged 65-69 showed an increase in the large rectangular, overall obese shape and a decrease in the rectangular slim shape. In summary, new senior women showed body shape characteristics of being short, more obese having, a bent over posture. As they grew older, the curves disappeared, and the body becomes rounder. The study found that variation in body shape exists among new senior women in the aged society.

• 천문학회보
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• 제41권2호
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• pp.33.1-33.1
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• 2016

We report detection of short-term flux variability in multi-epoch observations and intraday variability in polarized emission at millimeter-wavelength from S5 0716+714 using Korean VLBI Network (KVN) radio telescopes. Over the whole observation epochs, the source shows significant inter-month variations at K- and Q-band with modulation indices of 19% at K-band and 36% at Q-band. In each epoch, the source shows monotonic flux increase in Epoch 1 and 3, and monotonic flux decrease in Epoch 2 and 4. We found an inverted spectrum with mean spectral indices of -0.57 in Epoch 1 and -0.15 in Epoch. On the contrary, we found relatively steep indices of 0.24 and 0.17 in Epoch 2 and Epoch 4, respectively. In the study of intraday variability of polarization, we found significant variations in the degree of linear polarization at 86 GHz, and in polarization angle at 43 and 86 GHz during ~10 h. The spectrum of the source is quite flat with spectral indices of -0.07 to 0.07 at 22-43 GHz and -0.23 to 0.04 at 43-86 GHz. The measured degree of the linear polarization ranges from 2.3% to 3.3 % at 22 GHz, from 0.9% to 2.2 % at 43 GHz and from 0.4 % to 4.0 % at 86 GHz, yielding prominent variations at 86 GHz over 4-5 h. The linear polarization angle is in the range of 4 to $12^{\circ}$ at 22 GHz, -39 to $81^{\circ}$ at 43 GHz, and 66 to 119 at 86 GHz with a maximum rotation of $110^{\circ}$ at 43 GHz over ~4 h. We estimated the Faraday rotation measures (RM) ranging from -9200 to 6300 rad m-2 between 22 and 43 GHz, and from -71000 to 7300 rad m-2 between 43 and 86 GHz, respectively. The frequency dependency of RM was investigated, yielding a mean power-law index, a, of 2.0. This implies that the polarized emission from S5 0716+714 at 22-86 GHz moves through a Faraday screen in or near the jet of the source.

• 한국광학회지
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• 제8권6호
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• pp.445-449
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• 1997

비정질상과 결정상으로 가역변화하는 특성을 이용하여, 기존의 읽기전용 기록매체인 Compact Disk(CD)를 대체할 차세대 광기록매체로 주목받고 있는 Ge$_{2}$Sb$_{2}$Te$_{5}$(GST)의 상태변화에 따른 굴절율과 소광계수, 박막의 두께와 밀도 등 박막상수들을 구하였다. DC 스퍼터링방법으로 제작한 두꺼운 GST의 복소굴절율을 양자역학적 분산식을 이용한 모델링방법으로 구하고, 한편으로는 표면미시거칠기를 AFM(Atomic Force Microscopy)으로 결정한 다음, 타원해석 스펙트럼들을 수치해석적 역방계산하여 구한 복소굴절율과 비교하였다. 결정상과 비정질상일 때의 GST의 복소굴절율을 각각 구하고 이로부터 계산된 반사율을 측정된 반사율과 비교함으로써 수치해석적인 방법이 실제 GST의 복소굴절율과 더 일치하는 값ㅇㄹ 가지게 됨을 확인하였다. 이렇게 구한 GST의 복소굴절율을 기준데이터로 사용하여 실제 설계두께를 가지는 GST박막의 두께 및 표면거칠기층을 정량적으로 구하였다.다.

• 한국광학회지
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• 제8권4호
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• pp.277-282
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• 1997

광학소자나 전자소자의 코팅에 많이 이용되고 있는 Diamond-like Carbon(DLC) 박막의 복소굴절율을 광학적 방법을 사용하여 구하였다. PECVD(Plasma enhanced CVD)법에 의해 Si(100)기판과 비정질실리카 기판위에 각각 성장시킨 DLC 박막을 분광타원해석기와 분광광도계를 이용하여 타원해석 스펙트럼과 광투과율 스펙트럼을 측정하고, Sellmeier 분산관계식과 양자역학적 진동자 모델을 이용하여 분석하였다. 비정질실리카 위에 증착된 DLC 박막의 광투과영역에서 분광타원해석분석으로 굴절률 및 박막의 유효두께를 구하고 광흡수영역에서 투과스펙트럼을 역방계산하여 소광계수를 구한 뒤, 이 소광계수 스펙트럼에 최적 근사하는 양자역학적 분산식의 계수들을 회귀분석법으로 결정하여 복소굴절율을 구하였다. 그리고 모델링방법을 타워해석 스펙트럼에 적용하여 Si기판과 비정질이산화규소 기판위에 증착된 DLC 박막의 조밀도, 표면거칠기 등 박막상수를 박막의 성장조건에 따라 분석하였다.

• Journal of Chest Surgery
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• 제23권2호
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• pp.316-324
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• 1990

This study is a review of the early postoperative results in fifteen patients who diagnosed funnel chest and underwent the corrective surgical procedure by the sternal turnover[STO] or the sternocostal elevation[SCE] between January 1988 and February 1990. Thirteen among fifteen patients were male. Early eight patients were corrected by the STO and late seven patients by the SCE. Cosmetic result was excellent in one, fair in five, poor in two patients who received the STO and excellent in all patients corrected by the SCE. This unfavorable postoperative result in the STO group was due to the protrusion of inverted xiphisternal joint, the depression along the rejoined costal cartilages and forward tilting of the distal sternum. The lower vertebral indices measured on the lateral chest film were improved postoperatively from 0.42\ulcorner0.08 to 0.30\ulcorner0.05 in the STO group and from 0.31\ulcorner0.05 to 0.24\ulcorner0.03 in the SCE group. There was significant improvement in lower vertebral index in both groups, but it was difficult to compare the postoperative improvement between groups due to the different preoperative status. In the SCE group, the funnel index and the degree of depression measured on the computed tomography were significantly improved from 5.29\ulcorner1.72 and 3.11\ulcorner0.71 to 2.77\ulcorner0.46 and 1.63\ulcorner0.19[P<0.05], but there was no significant change in the degree of flatness postoperatively. This results suggest that sternocostal elevation is more cosmetic procedure than sternal turnover in children and in young adolescents whose funnel index measured on the computed tomography is low.

• 한국멀티미디어학회논문지
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• 제1권1호
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• pp.1-17
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• 1998

비디오 정보는 전자 도서관이나 WWW 및 주문형 비디오 (VOD) 시스템과 같은 다양한 응용분야에서 중요한 요소로 부각되고 있다. 비디오 정보는 특성상 계층적으로 구조화된 문서 형태를 가지기 때문에 본 논문에서는 이를 “구조화된 비디오 문서”라 부른다. 본 논문에서는 구조화된 비디오 문서를 데이터베이스에 효율적으로 저장하고, 검색하기 위한 데이터 모델과 질의어 및 색인 기법을 제안한다. 구조화된 비디오 문서는 논리적인 계층 구조 특성을 지니기 때문에, 본 논문에서는 객체 지향 데이터 모델을 이용하여 비디오 문서를 복합 객체로 모델링하고, 이를 저장하기 위한 객체 타입들을 정의한다. 또한 본 논문에서는 비디오 데이터의 캡션이나 주석을 기반으로 한 내용 기반 검색과 비디오 문서의 논리적 구조를 기반으로 한 구조 기반 검색을 제공하며, 비디오 문서의 시공간 관계 연산을 이용한 검색도 지원한다. 그리고, 구조화된 비디오 문서의 효율적인 질의와 색인 공간의 오버헤드를 줄이기 위해 최적화된 역 색인 기법을 제시한다.