• 한국항공우주학회지
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• 제47권9호
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• pp.617-628
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• 2019

벤트홀로 연결된 두 개의 가변 체적 챔버를 가지고 있는 파이로테크닉 분리 너트는 복잡한 과정을 통해 분리를 수행하므로 많은 설계 인자를 가지고 있다. 접촉부의 각도, 구성품의 질량, 누름봉 돌출부 안쪽 지름, 환형 챔버의 초기 부피, 확장 챔버의 초기 부피, 화약질량, 벤트홀 지름과 같은 설계 인자들의 변화에 따라 분리 너트의 성능이 어떻게 달라지는지를 파악하면 설계 개선 방향을 결정하는데 도움이 될 수 있다. 이에, 선행 연구를 통해 개발한 파이로테크닉 분리 너트 거동 예측 모델을 이용하여 매개변수 연구를 수행하였다. 다른 설계 인자의 값은 고정한 상태에서 한 설계인자의 값을 독립적으로 변화시키며 분리 시간이 어떻게 달라지는지, 변화의 원인이 무엇인지를 분석하였다.

• 한국연안방재학회지
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• 제4권spc호
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• pp.245-253
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• 2017

In this study, surface currents measured by small lagrangian GPS drifters (Aquadrifter) in Anmok coastal waters were analysed to account for the variability of nearshore surface current and wave-induced current to understand sediment transport mechanism near the crescentic bars in the surf-zone and near Kangneung breakwater and submerged breakwater in Anmok. The 8 times lagrangian drifter experiments were conducted mostly during in 2nd, 3rd, 4th intensive measurements in winter, summer, and spring seasons with long-term wave observation at the station W1. The analysed surface currents near the breakwaters in Anmok show that wave-induced currents at the middle of the submerged breakwater were separated and flowed toward the shoreline but offshore currents were dominant through the channels between the breakwaters. The longshore currents near the shoreline were flowed to the northwest (southeast) depending on the incoming waves from ENE (NNE). The surface nearshore offshore currents were generated mostly by waves and winds in case of high and low wave energy environments. Using the small-size lagrangian surface drifter experiments, we successfully measured longshore and offshore wave-induced currents in the surf-zone and near submerged breakwater close to Kangneung breakwater. The drifter experiment results show the availability of direct observation of nearshore surface currents to understand the mechanism of sediment transport analysing observed wave-induced current and ebb-current in the surf-zone generated by incoming waves and local winds.

• 공연문화연구
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• 제18호
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• pp.201-221
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• 2009

본고는 중국 마임에 대해 역사적 고찰을 진행한 글이다. 중국 전통극에서의 마임이 어디에서 기원했는가 하는 문제는 대답하기 매우 어려운 문제이나, 고대 배우들의 행위를 통해서 대략적이나마 초기의 자취가 발견된다. 필자는 사기(史記) "골계(滑稽)열전"에 수록된 초(楚)나라 장왕(莊王: B.C.613-591) 때의 배우 우맹(優孟) 이야기 속에서 그 근거를 찾아 제시할 수 있었고, 이를 근거로 중국의 마임은 최소 2600년 이상의 역사를 지닌것으로 판단하였다. 중국의 마임은 전통극 중에서도 제의극을 통해 형성되었고, 그 발전은 각색행당제(脚色行當制)와 긴밀히 연계되어 진행되었다. 주(做)나 타(打)를 구성하는 대부분의 정식동작(程式動作)들은 최근 몇 세기에 걸쳐 구체화되었지만 그것들의 좀 더 먼 기원은 고대의 무(舞)라 할 수 있다. 그런데 고대의 무는 다시 문무(文舞)와 무무(武舞)로 나뉘어 전개되었으니, 현재의 주나 타에 더 직접적으로 연결된 것은 문무와 무무라 할 수 있다.

• 치위생과학회지
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• 제20권4호
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• pp.206-212
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• 2020

Background: A Teachable Machine is a kind of machine learning web-based tool for general persons. In this paper, the feasibility of Google's Teachable Machine (ver. 2.0) was studied in the diagnosis of the tooth-marked tongue. Methods: For machine learning of tooth-marked tongue diagnosis, a total of 1,250 tongue images were used on Kaggle's web site. Ninety percent of the images were used for the training data set, and the remaining 10% were used for the test data set. Using Google's Teachable Machine (ver. 2.0), machine learning was performed using separated images. To optimize the machine learning parameters, I measured the diagnosis accuracies according to the value of epoch, batch size, and learning rate. After hyper-parameter tuning, the ROC (receiver operating characteristic) analysis method determined the sensitivity (true positive rate, TPR) and specificity (false positive rate, FPR) of the machine learning model to diagnose the tooth-marked tongue. Results: To evaluate the usefulness of the Teachable Machine in clinical application, I used 634 tooth-marked tongue images and 491 no-marked tongue images for machine learning. When the epoch, batch size, and learning rate as hyper-parameters were 75, 0.0001, and 128, respectively, the accuracy of the tooth-marked tongue's diagnosis was best. The accuracies for the tooth-marked tongue and the no-marked tongue were 92.1% and 72.6%, respectively. And, the sensitivity (TPR) and specificity (FPR) were 0.92 and 0.28, respectively. Conclusion: These results are more accurate than Li's experimental results calculated with convolution neural network. Google's Teachable Machines show good performance by hyper-parameters tuning in the diagnosis of the tooth-marked tongue. We confirmed that the tool is useful for several clinical applications.

• 농업생명과학연구
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• 제53권3호
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• pp.147-157
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• 2019

In this study, we tried to find out the most appropriate pre-processing method and to verify the feasibility of developing a low-price sensing system for predicting the hardy kiwis sugar content based on VNIRS and subsequent spectral analysis. A total of 495 hardy kiwi samples were collected from three farms in Muju, Jeollabukdo, South Korea. The samples were scanned with a spectrophotometer in the range of 730-2300 nm with 1 nm spectral sampling interval. The measured data were arbitrarily separated into calibration and validation data for sugar content prediction. Partial least squares (PLS) regression was performed using various combinations of pre-processing methods. When the latent variable (LV) was 8 with the pre-processing combination of standard normal variate (SNV) and orthogonal signal correction (OSC), the highest R2 values of calibration and validation were 0.78 and 0.84, respectively. The possibility of predicting the sugar content of hardy kiwi was also examined at spectral sampling intervals of 6 and 10 nm in the narrower spectral range from 730 nm to 1200 nm for a low-price optical sensing system. The prediction performance had promising results with R2 values of 0.84 and 0.80 for 6 and 10 nm, respectively. Future studies will aim to develop a low-price optical sensing system with a combination of optical components such as photodiodes, light-emitting diodes (LEDs) and/or lamps, and to locate a more reliable prediction model by including meteorological data, soil data, and different varieties of hardy kiwi plants.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.236-245
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• 2021

In this study, direct numerical and large eddy simulations of transitional flows around studs were conducted to investigate the effectiveness of turbulence stimulators at very low speeds for the minimum propulsion power condition of four knots. For simplicity, the studs were assumed to be installed on a flat plate, while the wake was observed up to 0.23 m downstream behind the second stud. For applicability to a model ship, we also studied the flow characteristics behind the first and second studs installed on a curved plate, which was designed to describe the geometry of a bulbous bow. A laminar-to-turbulent transition was observed in the wake at Re_D ≥ 921 (U_∞≥0.290 m/s), and the wall shear stress at Re_D = 1162 (U_∞ = 0.366 m/s) in the second wake was similar to that of the fully developed turbulent boundary layer after a laminar-to-turbulent transition in the first wake. At Re_D = 581 (U_∞ = 0.183 m/s), no turbulence was stimulated in the wake behind the first and second studs on the flat plate, while a cluster of vortical structures was observed in the first wake over the curved plate. However, a cluster of vortical structures was revealed to be generated by the reattachment process of the separated shear layer, which was disturbed by the first stud rather than directly initiated by the first stud. It was quite different from a typical process of transition, which was observed at relatively high Re_D that the spanwise scope of the turbulent vortical structures expanded gradually as it went downstream.

• Journal of Periodontal and Implant Science
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• 제52권5호
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• pp.383-393
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• 2022

Purpose: Aloe-emodin (AE), a natural anthraquinone abundant in aloe plants and rhubarb (Rheum rhabarbarum), has long been used to treat chronic inflammatory diseases. However, AE's underlying mechanisms in periodontal inflammation have not been fully elucidated. Acidic mammalian chitinase (AMCase) is a potential biomarker involved in bone remodeling. This study aimed to evaluate AE's effect on periodontitis in rats and investigate AMCase expression. Methods: Eighteen Sprague-Dawley rats were separated into the following groups: healthy (group 1), disease (group 2), vehicle (group 3), AE high-dose (group 4), and AE low-dose (group 5). Porphyromonas gingivalis ligatures were placed in rats (groups 2-5) for 7 days. Groups 4 and 5 were then treated with AE for an additional 14 days. Saliva was collected from all groups, and probing pocket depth was measured in succession. Periodontal pocket tissues were subjected to histomorphometric analysis after the rats were sacrificed. Bone marrow-derived macrophages and murine macrophages were stimulated with receptor activator of nuclear factor-κB ligand (RANKL) and treated with different concentrations of AE. AMCase expression was detected from the analysis of saliva, periodontal pocket tissues, and differentiated osteoclasts. Results: Among rats with P. gingivalis-induced periodontitis, the alveolar bone resorption levels and periodontal pocket depth were significantly reduced after treatment with AE. AMCase protein expression was significantly higher in the disease group than in the healthy control (P<0.05). However, AE inhibited periodontal inflammation by downregulating AMCase expression in saliva and periodontal pocket tissue. AE significantly reduced RANKL-stimulated osteoclastogenesis by modulating AMCase (P<0.05). Conclusions: AE decreases alveolar bone loss and periodontal inflammation, suggesting that this natural anthraquinone has potential value as a novel therapeutic agent against periodontal disease.

• 한국정보기술학회 영문논문지
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• 제10권1호
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• pp.71-83
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• 2020

In this paper, we propose a system that can detect the shape of a hand at high speed using an FPGA. The hand-shape detection system is designed using Verilog HDL, a hardware language that can process in parallel instead of sequentially running C++ because real-time processing is important. There are several methods for hand gesture recognition, but the image processing method is used. Since the human eye is sensitive to brightness, the YCbCr color model was selected among various color expression methods to obtain a result that is less affected by lighting. For the CbCr elements, only the components corresponding to the skin color are filtered out from the input image by utilizing the restriction conditions. In order to increase the speed of object recognition, a median filter that removes noise present in the input image is used, and this filter is designed to allow comparison of values and extraction of intermediate values at the same time to reduce the amount of computation. For parallel processing, it is designed to locate the centerline of the hand during scanning and sorting the stored data. The line with the highest count is selected as the center line of the hand, and the size of the hand is determined based on the count, and the hand and arm parts are separated. The designed hardware circuit satisfied the target operating frequency and the number of gates.

• 한국정보통신학회논문지
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• 제26권7호
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• pp.1060-1070
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• 2022

정보 기술의 발달로 시스템의 규모는 대형화되고 역할의 종류도 다양해져서 기존의 역할기반 접근제어로는 확장성, 호환성, 복잡성 등의 한계에 부딪히게 되었다. 블록체인 기술은 기존 보안 취약점에 새로운 해법을 제시하며 다양한 분야에서 활용되고 있다. 본 논문에서는 저장소의 접근 빈도와 저장 용량에 따라 요구되는 가스 및 처리 시간이 달라지는 블록체인 환경에서 효율적인 역할기반접근제어를 제안하였다. 제안하는 방식은 재사용 가능한 단위의 역할을 재정의하고, 동적인 상태를 효율적으로 반영할 수 있는 계층적 구조를 도입하여 복잡성을 해결하고 효율성 및 확장성을 강화하였고, 암호화폐 연동이 가능할 수 있도록 사용자 중심의 인증기능을 포함하였다. 제안하는 모델은 마르코프체인을 이용하여 이론적으로 먼저 검증하고, 이더리움 프라이빗 네트워크에서 구현하여 대표함수에 대한 비교 실험을 실행하여 사용자 추가 및 트랜잭션 등록 시에 요구되는 시간과 가스 효율성에 대하여 검증하였다. 향후 이를 기반으로 예외 상황 등을 고려한 구조 확장 및 실험 등이 요구된다.

• 한국시뮬레이션학회논문지
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• 제19권1호
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• pp.133-141
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• 2010

본 연구는 층화추출법과 통제변수기법을 시뮬레이션 실험설계에서 동시에 사용하여 파라미터의 추정 효율성을 개선하는 방법을 제안하였다. 시뮬레이션을 수행하는 도중에 수집한 표준화 부가변수를 통제변수기법에 활용하여 파라미터 추정을 위한 반응변수의 오차를 줄이도록 하였으며 통제변수 구성에 사용되지 않은 부가변수를 층화변수로 활용하는 층화추출기법을 적용하여 통제반응변수의 변이성을 추가로 감소하였다. 반응변수와 통제변수 사이의 공분산 관계가 알려진 경우에 두 방법을 동시에 활용하여 파라미터를 추정하는 기법의 시뮬레이션 효율성을 이론적으로 도출하였다. 반응변수와 통제변수 사이의 상관관계 구조가 알려지지 않은 경우 선택된 모형의 시뮬레이션 결과는 제안된 층화 통제 추정기법이 층화추출법이나 통제변수기법을 개별적으로 적용하여 파라미터를 추정하는 것보다 우수한 것으로 나타나고 있다.