• 한국건축시공학회지
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• 제24권1호
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• pp.23-34
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• 2024

본 연구의 목적은 RC 구조물의 균열 보수용 폴리머 시멘트 복합체의 휨접착성능을 평가하기 위함이다. 시멘트 모르타르에 다양한 크기의 균열을 만들어 PCCs를 충전한 후, 소정의 양생을 거쳐 휨접착강도와 휨강도 개선 정도를 파악하였다. 연구결과, 균열보수용 PCCs의 휨접착강도는 시멘트의 종류, 폴리머 종류 및 폴리머 결합재비에 따라 영향을 받으며 실리카퓸을 혼입한 초조강시멘트를 사용한 경우가 보통시멘트를 사용한 경우에 비해 최대 19.0%의 휨접착강도 개선효과가 나타났다. PCCs로 충전된 시멘트 모르타르의 휨강도 개선 정도는 균열폭의 영향보다는 균열깊이에 따라 큰 차이를 보였으며 균열에 충전된 PCCs가 단순히 보수재료로서 기능뿐만 아니라 어느 정도 휨강도를 개선시키는 보강재료로서도 역할을 하였다. 본 연구결과, 초조강시멘트, 3종류의 폴리머 디스퍼전과 실리카퓸, 60%~80%의 높은 폴리머 결합재비로 제작한 PCCs가 균열을 충전하는 보수재료로서 현장에서 충분히 사용될 수 있을 것이다.

• 한국임상수의학회지
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• 제40권2호
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• pp.119-123
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• 2023

Although various imaging evaluation methods have been developed and utilized, thoracic radiography remains essential and is the top priority for diagnosing and managing cardiac diseases. Thoracic radiographic measurements associated with the vertebral heart scale (VHS) and caudal vena cava (CVC) can objectively diagnose cardiac disease in many animals. In particular, VHS measurement is primarily used to evaluate the dimensions of the heart size on thoracic radiographs and can measure cardiomegaly more objectively. Additionally, the value of the CVC compared with the aorta (Ao) and the length of vertebrae (VL) can be used as valuable parameters in right congestive heart failure. To describe the CVC/Ao and CVC/VL ratios in 10 long-tailed gorals (Naemorhedus caudatus) without subjective radiographic evidence of cardiac diseases. The VHS, CVC, Ao, and VL of gorals were measured in the right lateral (RL) view of the thoracic radiographs. In the RL view of 10 gorals, the VHS was 9.31 ± 0.55 vertebrae (v), the CVC/Ao ratio was 0.84 ± 0.13, and the CVC/VL ratio was 0.67 ± 0.09. Additionally, the thoracic morphology of gorals was determined to be intermediate (thoracic depth-to-width ratio, 1.04 ± 0.09, 0.75-1.25). This study confirmed that VHS was significantly correlated with CVC and Ao, and measuring and comparing each value would help diagnose cardiac diseases in gorals. The radiographic measurements in this study will allow veterinarians to diagnose several cardiac diseases in gorals.

• 농업과학연구
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• 제49권2호
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• pp.367-377
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• 2022

The purpose of this study was to analyze the deterioration of trail conditions and to obtain information for desirable maintenance and restoration of a trail in Deogyusan National Park. The physical characteristics of a trail were surveyed at a total of 412 sites over 79.8 km length. The average trail degree and width were found to be 14.31° and 1.60 m, respectively, while the average bare trail width was 1.40 m and the average maxim trail depth was 5.66 cm. Major deterioration types of trail were trail deepening (36.6%), rock exposure (33.9%), and root exposure (12.5%) in order of frequency. Deterioration classes of the trail were 0.626 km (0.8%), 3.110 km (3.9%) and 8.935 km (11.2%) for heavily, moderately, and lightly deteriorated, respectively, with a deterioration rate of 12.671 km (15.9%). Compared to other national parks, the ratio damaged trail to the total trail was 15.9%, which is slightly higher than other, including Jirisan National Park 9.6% (2019), Bukhansan National Park 13.6% (2019), Sokrisan National Park 11.7% (2019), Chiaksan National Park 12.3% (2015), and Woraksan National Park 10.5% (2015). The section of trail in Deokyusan National Park where the damage grade is analyzed as "Heavy" should therefore be restored in consideration of the field conditions. In particular, the damage status of the trail is expected to be greatly improved when the trail surface maintenance level is restored.

• 콘크리트학회논문집
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• 제26권3호
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• pp.299-306
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• 2014

콘크리트 구조물의 철근 부식 문제를 해결하기 위하여 코팅철근이 사용된다. 에폭시 코팅 철근에 비해 아연코팅철근의 콘크리트 보의 휨 거동 영향에 대한 자료는 거의 없는 실정이다. 이 연구의 목적은 아연코팅철근이 콘크리트 보의 휨 거동에 미치는 영향을 파악하는 데 있다. 아연코팅철근을 사용한 부재와 일반철근을 사용한 부재의 구조실험을 통하여 휨 거동 특성을 비교하였다. 실험변수로써 철근의 아연코팅 유무, 사용 철근비와 피복 두께를 고려하였다. 아연코팅철근 콘크리트 보의 균열패턴, 균열폭, 처짐 및 변형률 특성을 파악하였다. 아연코팅철근 콘크리트 보의 휨강도는 일반철근 콘크리트 보의 휨강도와 거의 차이가 나지 않는다. 철근표면의 아연코팅은 처짐, 균열폭 비교 결과에도 뚜렷한 영향을 미치지 않는다. 또한, 아연코팅철근 보와 일반철근 보의 하중-변형률 곡선은 비슷한 결과를 나타낸다. 따라서, 전반적으로 아연코팅철근의 사용은 일반철근을 사용할 때에 비해 콘크리트 보의 휨 거동에 악영향을 미치지는 않는 것으로 나타난다.

• 한국지진공학회논문집
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• 제10권3호
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• pp.113-123
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• 2006

콘크리트 부재의 내진설계에 있어 강도와 더불어 변형 능력은 중요한 요소이다. 연결보는 전단 지배 부재임에도 항복 이후 소성 변형을 요구하는 부재인데 본 연구에서는 연결보의 변형 능력에 대한 실험을 통해 변형 모형을 제시하였다. 일반적인 배근 형태를 가진 철근 콘크리트 연결보를 대상으로 단조하중실험을 수행하였다. 경간-깊이비, 휨 철근비, 전단 철근비를 변수로 하여 연결보의 거동을 평가하였다. 전단 지배 부재인 연결보는 아치작용과 트러스 작용으로 전단력에 대해 저항하는데 실험 결과를 통해 전단력을 두 작용의 구분과 항복 강도 발현 이후 소성 변형에 따른 두 작용의 구성비 변화에 대해 분석하였다. 실험결과에 기초한 전단 철근과 휨 철근의 변형률 분포 모형을 이용하여 휨 철근의 응력 상태를 산정하였다. 휨 철근의 부착-미끄러짐에 의해 결정되는 균열폭을 고려하는 연결보의 변형 모형을 제시하였다. 항복 상태는 휨 철근의 항복 시점으로 정의하였고, 극한 상태는 변형 증가에 따른 스트럿의 압축 강도 저하에 의해 결정되었다. 이 변형 모형은 변위기초설계에 활용될 수 있을 것으로 기대된다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.464-471
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• 2002

Porosity formation in partial penetration welds by high power lasers is a serious problem in industry. There are two main causes that induce porosity formation. One form of porosity is due to gases (e.g. hydrogen, oxygen) dissolving into the weld pool because of the high temperature and then the rapid solidification traps gases as a bubble in the weld metal. The second problem is voids formed by the keyhole collapsing due to unstable keyhole fluid dynamics. The voids that form at the bottom of the keyhole are relatively large and irregular in shape compared to the gas bubbles; this void formation is the primary concern in this paper. The reduction of voids formed by keyhole collapse is achieved by improving the stability of keyhole. Two methods to improve keyhole stability are discussed in this paper: pulse modulation and beam incident angle. Pulse modulation of the laser beam was performed between 100 Hz and 500 Hz to find out the optimum frequency for the keyhole dynamics. The incident beam angle changed the impact angle of the laser beam to the work surface in a range of 0 to 25 degrees. Glycerin in a semi-solidified state is used as a medium for performing the welding because its transparency allows of visualization of the keyhole.

• 품질경영학회지
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• 제44권4호
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• pp.935-949
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• 2016

Purpose: This study attempts to find out the optimum condition of the rotary cutter making pellet in the footwear outsole process. The pellets are used in the process of outsole rubber fabrication to reduce cycle time and save raw material. Methods: Computer simulations are used to analyze the maximum stress in the rotary cutter after designing a variety of cutter shapes. Taguchi method is used to identify the robust condition of the cutter. In $L_{18}$ orthogonal array, the control factors such as knife width, twisted angle, number of knives, diameter, knife depth and supported angle are considered and noise factors like assembly tolerance and amount of antifriction are allocated. Results: It is found that the most important factors to reduce maximum stress in the cutter are supported angle and diameter. Using Tacuchi's results, we can reduce 70% cycle time and 9% raw material compared to the traditional method using cutting die. Conclusion: When designing the rotary cutter, the best conditions are the diameter at its maximum allowable value and supported angle in the boundary of machine inner space.

• International Journal of Computer Science & Network Security
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• 제23권12호
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• pp.213-219
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• 2023

In recent years, popularity of deep learning (DL) is increased due to its ability to extract features from Hyperspectral images. A lack of discrimination power in the features produced by traditional machine learning algorithms has resulted in poor classification results. It's also a study topic to find out how to get excellent classification results with limited samples without getting overfitting issues in hyperspectral images (HSIs). These issues can be addressed by utilising a new learning network structure developed in this study.EfficientNet-B4-Based Convolutional network (EN-B4), which is why it is critical to maintain a constant ratio between the dimensions of network resolution, width, and depth in order to achieve a balance. The weight of the proposed model is optimized by Search and Rescue Operations (SRO), which is inspired by the explorations carried out by humans during search and rescue processes. Tests were conducted on two datasets to verify the efficacy of EN-B4, with Indian Pines (IP) and the University of Pavia (UP) dataset. Experiments show that EN-B4 outperforms other state-of-the-art approaches in terms of classification accuracy.

• 한국해양학회지:바다
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• 제27권1호
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• pp.33-47
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• 2022

다중빔측심자료를 이용하여 우리나라 전 연안 해역에 발달한 해저 사퇴의 분포를 확인하고, 해역별 지형 특성을 파악하고자 하였다. 이를 위하여 국립해양조사원의 황해와 대한해협 수심자료를 이용하여 DEM 자료를 작성한 후 TPI 기법을 적용하여 사퇴의 경계를 정밀하게 추출하였다. 그 결과 우리 해역에 분포하는 총 200개의 사퇴를 확인하였으며, 그들의 규모(폭, 길이, 둘레, 면적, 높이)와 형태(폭/길이 비율, 높이/폭 비율, 선형·분기형, 노출·비노출형)에 대한 통계분석을 실시하여 사퇴의 지역별 특성을 분석하였다. 이러한 연구 결과는 연안 항해안전은 물론 해양지명 선정 지원, 해사골재자원 파악, 수산자원 관리 등에 활용될 수 있다.

• Journal of Welding and Joining
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• 제14권6호
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• pp.93-100
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• 1996

Effect of a flux composition on weld metal toughness in submerged arc welding with 60kgf/$\textrm{mm}^2$ grade C-Mo type wires was investigated and interpreted in terms of weld metal microstructure and hardenability. Flux workability was also studied by characterizing a weld bead profile. Compared to other weld metals, .weld metal used alumina basic flux with nickel showed lowest oxygen content, highest hardenability and the most acicular ferrite. The highest impact toughness of that weld metal, however, was attributed to the tough matrix due to the nickel rather than to the larger amount of acicular ferrite. Manganese silicate flux had better workability than alumina basic flux, showing broader welding conditions resulting in a depth-to-width ratio of 0.5. The composition of oxides in the weld metal was dependent on the flux composition, showing MnO-SiO$_2$-TiO in manganese silicate flux and MnO-SiO$_2$-Al$_2$O$_3$-TiO in alumina basic flux. MnO-SiO$_2$composition in both oxides was similar to a tephroite.