• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.299-304
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• 2011

As more satellites are designed to downlink their observed image data through the X-band frequency band, it is inevitable that the occupied bandwidth of a target satellite will overlap with that of other X-band downlink satellites. For sun-synchronized low earth orbit satellites, in particular, it can be expected that two or more satellites be placed within the looking angle of a ground station antenna at the same time. Due to the overlapping in the frequency band, signals transmitted from the adjacent satellites act as interferers, leading to degraded link performance between target satellite and ground station. In this paper, link analysis was initiated by modeling the radiation pattern of ground station antenna through a validated Jet Propulsion Laboratory peak envelope model. From the relative antenna gain depending on the offset angle from center axis of maximum antenna directivity, the ratio of received interference signal level to the target signal level was calculated. As a result, it was found that the degradation increased when the offset angle was within the first point of radiation pattern. For a 7.3 m antenna, serious link degradation began at an offset angle of 0.4 degrees. From this analysis, the link performance of the coming satellite passes can be recognized, which is helpful to establish an operating procedure that will prevent the ground station from receiving corrupted image data in the event of a degraded link.

• Imaging Science in Dentistry
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• 제50권2호
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• pp.169-174
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• 2020

Purpose: Periodontal disease causes tooth loss and is associated with cardiovascular diseases, diabetes, and rheumatoid arthritis. The present study proposes using a deep learning-based object detection method to identify periodontally compromised teeth on digital panoramic radiographs. A faster regional convolutional neural network (faster R-CNN) which is a state-of-the-art deep detection network, was adapted from the natural image domain using a small annotated clinical data- set. Materials and Methods: In total, 100 digital panoramic radiographs of periodontally compromised patients were retrospectively collected from our hospital's information system and augmented. The periodontally compromised teeth found in each image were annotated by experts in periodontology to obtain the ground truth. The Keras library, which is written in Python, was used to train and test the model on a single NVidia 1080Ti GPU. The faster R-CNN model used a pretrained ResNet architecture. Results: The average precision rate of 0.81 demonstrated that there was a significant region of overlap between the predicted regions and the ground truth. The average recall rate of 0.80 showed that the periodontally compromised teeth regions generated by the detection method excluded healthiest teeth areas. In addition, the model achieved a sensitivity of 0.84, a specificity of 0.88 and an F-measure of 0.81. Conclusion: The faster R-CNN trained on a limited amount of labeled imaging data performed satisfactorily in detecting periodontally compromised teeth. The application of a faster R-CNN to assist in the detection of periodontally compromised teeth may reduce diagnostic effort by saving assessment time and allowing automated screening documentation.

• 한국실내디자인학회논문집
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• 제27권2호
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• pp.45-54
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• 2018

Immersive space is a new type of space, which is converged with other domains and expressed in various ways and here, a mutual exchange between space and participants is realized with active intervention of participants. The purpose of this study is to examine boundary changes and characteristics in virtual space and reality or inside and outside, focusing on immersive space. For this study, a case analysis was conducted, based on the key words regarding flow experience and boundary characteristics in immersive space. The boundary characteristics extracted are as follow. First, while immersive space is overlapped in many different ways, the boundary in space gradually changes and one unique and convergent space is formed. Also, a combination of overlap is made with internal and external physical force and a convergent boundary is created. Second, forms are mixed in diverse ways and an unrealistic boundary space is revealed. For new experience, it has familiar, but new experiential characteristics and also shows an expanded boundary by the medium of different domains. Third, a simultaneous space, based on variability of time and space, has an ambiguous boundary due to a meaningless physical boundary of space and changing into a space region constantly, it becomes an unlimited variable space. Fourth, a linear expansion-based emergent space has nonlinearity, which creates a meaningless boundary, recognized as an irregular, dynamic and transformative space and expands to a creative space. In conclusion, it is anticipated that based on diverse characteristics found in immersive space, this study would give unlimited inspiration to many design fields and art creation activities and contribute to a further development through continued research on immersive space.

• 한국의상디자인학회지
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• 제17권1호
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• pp.53-68
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• 2015

The purpose of this study is to analyze check pattern of nail art from 2011 to 2013. The results of this study are as follows; 1) Check pattern of nail art is total 257 patterns, and there are 84 argyle, 29 tartan, 24 harlequin, 24 over, 23 window-pane, 15 stitcheds, 13 hound tooth, 10 block, 10 madras, 8 gingham, 8 gradation, 7 shepherd, and 2 tattersall check patterns. Through this result, in nail art, the relatively simple patterns such as a vertical pattern, a horizontal pattern, and cross or overlap diagonal line are used more than elaborate and complex check patterns of a fibrous tissue from a weaving process. 2) In check pattern of nail art, N-affiliated color and R-affiliated color are remarkably well-used, because of the effects of argyle, tartan, window-pane, harlequin, stitched, over, and hound tooth check patterns used the most during the past three years. Especially, most tartan, harlequin, over, and hound tooth check patterns use their own special colors such as R-affiliated colors and N-affiliated colors as it is, and argyle, window-pane, stitched, and over check patterns use well by arranging N-affiliated colors and R-affiliated colors. 3) The most used expressive technique is hand painting to express check pattern in nail art, because new products related to UV gel are well launched. These materials can draw fine line that is hard to express by existing polish easily and simply, and not only have set quickly hard, so procedure time is very short, so it is compatible to draw check pattern personally, but also it is well covered, so check pattern is more clearly expressed.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.74-74
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• 2002

This paper describes a corner matching technique for automatic relative orientation. Automatically matched corner points from stereo aerial images are used to a data set and help to improve automation of relative orientation process. A general corner matching process of overall image to image has very heavy operation and repetitive computation, so very time-consuming. But aerial stereo images are approximately seventy percent overlapped and little rotated. Based this hypothesis, we designed a sectional corner matching technique calculating correlation section by section between stereo images. Although the overlap information is not accurate, if we know it approximately, the matching process can be lighter. Since the size of aerial image is very large, corner extraction process is performed hierarchically by creating image pyramid, and corners extracted are refined at the higher level image. Extracted corners at the final step are matched section by section. Matched corners are filtered using positional information and their relation and distribution. Filtering process is applied over several steps because the thing affecting to get good result-good relative orientation parameter- is not the number of matched corner points but the accuracy of them. Filtered data is filtered one more during the process calculating relative orientation parameters. When the process is finished, we can get the well matched corner points and the refined Von-Gruber areas besides relative orientation parameters. This sectional corner matching technique is efficient by decreasing unnecessarily repetitive operations and contributes to improve automation for relative orientation.

• 한국실내디자인학회논문집
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• 제11호
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• pp.57-63
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• 1997

In the early 20'c, scientific thoughts make a change the absolute and separate concept of space-time into relative concept of continual entity; a kind of ideal world. It suggests that the meaning of geometry as absolute truth with which has endowed human beings would changed to a relative meaning of accumulation in intellectual work on 'nature'. This cognitive changes appeared into absolute arts in 20'c like Cubism, Superematism or Constructivism. De Stijl movement which had recepted the relative concepts like Einstein's 'theory of relativity' as a developed thought from Newton-Cartesian cognition on the world. Abstration would be adequate method for expressing the dynamics and interrelationship between forms and for giving values to indivisual elements in a compositiov. This method had appeared Modern architectural form, as a common framework. The expression characteristics of geometrical design in Deconstructive and Experimental architecture were summerized in four features through the results of the analysis. First, the relation of architectural element and intertextuality is expressed in discontinuation of context and refusal of functional building. Second, the concept of trace expresses as connection of place, decomposing of excavation of trace, trace of axis, trace of fragments. Third, anti-gravity expression is there to express of open cubic, to outgrow of rectangular system, to outgrow of volume, to separate of ground connectiov. Fourth, the complex composition of abstracted geometric form is these to abstracted geometry about indefinite shape, to layer through the overlap and collage, to de-meaning and amusement of form through the pursuit of uncertainty, to indeterminate of formal meaning through operation and composition of similar form cause to the diverse of meaning.

• 정보처리학회논문지C
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• 제12C권4호
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• pp.481-488
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• 2005

현재 무선 네트워크 IP를 위한 이동성 자원의 표준인 Mobile IP는 이동 노드(Mobile Node, MN)의 접속에 관한 사용자 인증이 비효율적이다. 본 논문에서는 네트워크 구성원들의 상호 인증 및 보안 서비스를 위해서 인증(Authentication), 권한부여(Authorization) 및 과금(Accounting)을 지원하는 AAA 프로토콜에 기반하여 Mobile IP의 보안성을 유지하고 빠른 핸드오프를 수행하는 새로운 보안 핸드오프 방식을 제안한다. AAA 프로토콜은 QoS를 제한하는 비효율적인 인증 절차가 존재하여 MN이 핸드오프를 수행할 때마다 새로운 세션 키를 분배 받아야 한다. 본 논문에서는 MN이 핸드오프를 수행할 때 발생하는 지연 시간과 MN의 인증으로 인한 AAA 서버의 오버헤드를 줄이고자 공유(Overlap, 오버랩) 네트워크 구조 기반의 세션키 재사용 방법을 제안한다 본 방식에서는 MN의 보안성 향상을 위하여 공유 세션 키를 유선상에서 전달하는 방식에 기반하고, 그에 따라 신속하고 자연스러운 핸드오프 메커니즘을 제공한다. 분석적 모델링결과에 의하면 제안하는 방식은 기존 세션키 재사용 방식과 비교하여 핸드오프 시간을 고려하는 핸드오프 실패율에 있어서 $40\%$정도의 성능향상을 보인다.

• Tribology and Lubricants
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• 제14권4호
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• pp.15-22
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• 1998

Recently, the importance of variable displacement piston pump is increasing in industrial world. Especially, most consumers require various range of pressures and flow rates. Pressure compensator is a system controlling flow rate in piston pump at low cost and, therefore, satisfies the need of consumers. However, the system has serious problems, such as response and leakage. The response and leakage are affected by clearance between actuator piston and cylinder, roughness of surface, and spool overlap. In this paper, these effects are investigated experimentally, and optimal clearance and chamfer is obtained. While diameter of cylinder is fixed and diameter of actuator piston is changed in this experiment, response and leakage are measured. Also parameters such as roughness and processing accuracy are changed for piston of fixed clearance. Experimental setup modelled into several parts of actuator piston, cylinder, spool, and swash plate. Input pressure is changed by function generator and proportional valve. The result of this experiment shows that leakage increases very much in proportion to the increase of clearance, and especially leakage occurs enormously when clearance is more than 0.002. The response is not good because as clearance increases leakage increases and as clearance decreases viscous damping effect increases. Accordingly, it is found out that optimal clearance range exists for tile response, within about 0.0012∼0.0014, at this time. Futhermore, the better roughness and geometrical accuracy of actuator piston are, the smaller are leakage and friction. The paper informs that response and leakage are influenced by and geometrical accuracy of actuator piston, roughness of surface, and the clearance between actuator piston and cylinder, and that optimal design of actuator piston in the pressure compensator is possible.

• 한국멀티미디어학회논문지
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• 제13권11호
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• pp.1698-1705
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• 2010

본 논문에서는 자기 공명 영상에서 고속의 간 분할 기법을 제안한다. 제안 기법은 MR 영상을 정규화된 기울기 크기 정보를 바탕으로 효율적으로 객체와 경계로 구분한다. 다음으로 간 영역에 해당하는 객체를 직전에 분할된 슬라이스의 간 영역에서 추출된 씨앗점들로 2차원 씨앗점 영역 성장법을 이용하여 검출한다. 마지막으로 롤링 볼 알고리즘과 연결 요소 분석 기법을 사용하여 간 경계 부근의 위양성 오차를 최소화한다. 20명의 환자 데이터에 대하여 제안 기법으로 분할한 결과와 수작업으로 분할한 결과를 비교하여 정확성을 검증하였다. 평균 볼륨 오버랩 오차 5.2%였고, 평균 절대값 볼륨 측정 오차는 1.9%였다. 제안 기법으로 한 환자 데이터를 분할하는 데 소요되는 평균 시간은 약 3초 정도였다. 제안 기법은 빠르고, 정확한 간 분할을 필요로 하는 컴퓨터 보조 간 진단 기법에 사용될 수 있다.

• Earthquakes and Structures
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• 제14권5호
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• pp.399-409
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• 2018

The dynamic response and seismic damage of single-layer reticulated shells in the near field of a rupturing fault can be different from those in the far field due to the different characteristics in the ground motions. To investigate the effect, the dynamic response and seismic damage of this spatial structures subjected to two different ground motions were numerically studied by nonlinear dynamic response analysis. Firstly, twelve seismic waves with an apparent velocity pulse, including horizontal and vertical seismic waves, were selected to represent the near-fault ground motion characteristics. In contrast, twelve seismic records recorded at the same site from other or same events where the epicenter was far away from the site were employed as the far-fault ground motions. Secondly, the parametric modeling process of Kiewitt single-layer reticulated domes using the finite-element package ANSYS was described carefully. Thirdly, a nonlinear time-history response analysis was carried out for typical domes subjected to different earthquakes, followed by analyzing the dynamic response and seismic damage of this spatial structures under two different ground motions based on the maximum nodal displacements and Park-Ang index as well as dissipated energy. The results showed that this spatial structures in the near field of a rupturing fault exhibit a larger dynamic response and seismic damage than those obtained from far-fault ground motions. In addition, the results also showed that the frequency overlap between structures and ground motions has a significant influence on the dynamic response of the single-layer reticulated shells, the duration of the ground motions has little effects.