• Advances in Computational Design
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• 제5권2호
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• pp.127-146
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• 2020

Building Information Modeling (BIM) is increasingly used throughout the facility's life cycle for various applications, such as design, construction, facility management, and maintenance. For existing buildings, the geometry of as-built BIM is often constructed using dense, three dimensional (3D) point clouds data obtained with laser scanners. Traditionally, as-built BIM systems do not contain the material and textural information of the buildings' elements. This paper presents a semi-automatic method for generation of material and texture rich as-built BIM. The method captures and integrates material and textural information of building elements into as-built BIM using thermal infrared sensing (TIS). The proposed method uses TIS to capture thermal images of the interior walls of an existing building. These images are then processed to extract the interior walls using a segmentation algorithm. The digital numbers in the resulted images are then transformed into radiance values that represent the emitted thermal infrared radiation. Machine learning techniques are then applied to build a correlation between the radiance values and the material type in each image. The radiance values were used to extract textural information from the images. The extracted textural and material information are then robustly integrated into the as-built BIM providing the data needed for the assessment of building conditions in general including energy efficiency, among others.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1721-1729
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• 2001

The performance of gas turbines is decreased as their operating hours increase. Fouling in the axial compressor is one of main reasons for the performance degradation of gas turbine. Airborne particles entering with air at the inlet into compressor adhere to the blade surface and result in the change of the blade shape, which is closely and sensitively related to the compressor performance. It is difficult to exactly analyze the mechanism of the compressor fouling because the growing process of the fouling is very slow and the dimension of the fouled depth on the blade surface is very small compared with blade dimensions. In this study, an improved analytic method to predict the motion of particles in compressor cascades and their deposition onto blade is proposed. Simulations using proposed method and their comparison with field data demonstrate the feasibility of the model. It if found that some important parameters such as chord length, solidity and number of stages, which represent the characteristics of compressor geometry, are closely related to the fouling phenomena. And, the particle sloe and patterns of their distributions are also Important factors to predict the fouling phenomena in the axial compressor of the gas turbine.

• 한국의학물리학회지:의학물리
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• 제26권1호
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• pp.36-41
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• 2015

정위체부방사선수술(SBRT) 환자의 선량분포를 계산하기 위해 전산모사 방식을 이용한 응용프로그램을 개발 하였다. 본 소프트웨어는 최근 이용이 활발하게 증가하고 있는 Geant4를 기반으로 개발 하였다. 환자에 조사하기 위한 광자선 스펙트럼은 이전 연구에서 구한 선형가속기 스펙트럼 자료를 사용하였다. 치료계획시스템과 유사한 조사면을 구현하기 위하여 PrimaryGeneratorAction 클래스에서 MLC 조사면 형태를 반영하도록 하였다. 본 연구에서는 8개 조사면에 대한 계산을 수행하였으며 이 때 갠트리의 각도는 PrimaryGeneratorAction 클래스에서 회전 매트릭스를 사용하여 선원의 위치를 변경하는 방법을 사용하였다. 환자에 대한 물질 자료는 CT의 dicom 파일에서 픽셀 크기, 매트릭스 크기 등의 정보와 픽셀의 HU를 밀도로 변환한 파일을 생성한 다음 이 파일을 이용 환자의 모델링에 이용 하였다. 환자의 물질 구성과 기하학적 자료의 입력에 있어 EGSnrc 코드와의 비교를 통하여 계산의 효율성을 비교하였다.

• 한국해양환경ㆍ에너지학회지
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• 제12권1호
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• pp.9-14
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• 2009

2차원 비정상의 RANS 방정식을 이용하여 피치가 고정된 3개 혹은 4개의 날개(hydrofoil)를 가지는 조류발전용 수직축 터빈주위의 비정상 유동장 해석을 수행하였다. 상용수치해석코드인 Fluent를 이용하여, 균일류에 놓인 $NACA65_3$-018날개에 대하여 받음각(angle of attack)의 변화를 주며 계산되는 유체력을 실험값과 비교하였고, 이를 바탕으로 대표적인 수직축 조류발전 터빈의 특성을 2차원적으로 고찰하였다. 사용된 수치해법은 대상 유동을 효과적으로 모사할 수 있음을 확인 하였고, 터빈의 최적 효율은 날개수 및 유속 대비 회전수 등의 적절한 조합으로 실현 될 수 있음을 파악하였다.

• International Journal of Aeronautical and Space Sciences
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• 제16권3호
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• pp.437-444
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• 2015

Satellite selection and exclusion techniques have been applied to the global navigation satellite system (GNSS) with the aim of achieving a balance between navigational performance and computational efficiency. Conventional approaches to satellite selection based on the best dilution of precision (DOP) are excessively computational and complicated. This paper proposes a new method that applies a geometric sensitivity index of individual GNSS satellites. The sensitivity index is derived using the inner product of the line of sight (LOS) vector of each satellite. First, the LOS vector is computed, which accounts for the geometry between the satellite and user positions. Second, the inner product of each pair of LOS vectors is calculated, which indicates the proximities of the satellites to one another. The proximity can be determined according to the sensitivity of each satellite. A post-processing test was conducted to verify the reliability of the proposed method. The proposed index and the results of a conventional approach that measures the dilution of precision (DOP) were compared. The test results demonstrate that the proposed index produces results that are within 96% of those of the conventional approach and reduces the computational burden. This index can be utilized to estimate the sensitivity of individual satellites, obtaining a navigation solution. Therefore, the proposed index applies to satellite selection and exclusion as well as to the sensitivity analyses of multiple GNSS applications.

• 한국도로학회논문집
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• 제20권4호
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• pp.73-84
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• 2018

PURPOSES : Most of the traffic surveys are carried out by an inspection method by the manpower. In some cases, the video equipment is used only in some regions when the traffic volume is surveyed. In this case, there is environmental restriction that the road equipment to fix the video equipment should exist. Also, in areas where information such as digital maps and satellite photographs is old or not provided, they are forced to rely on manpower research, but it is difficult to put huge amounts of time and money into the research in places where labor supply and demand is difficult. This difficulty is particularly pronounced in overseas business. METHODS : The purpose of this study is to improve the efficiency of business by using the drones in the traffic investigation through analysis of the cost reduction effect between the existing method and the proposed method in the overseas business traffic survey. The scope of the research is limited to the scope of research, and based on the case of overseas projects, the method of using drone for each research sector is suggested. RESULTS : In the traffic condition survey section, we propose the use of drone for traffic survey and queue length survey, and it is confirmed that there is a cost saving effect of 16% ~ 27% compared with the existing method. In the road condition survey, we propose the use of drones for road surface linear survey, geometry survey, and obstacle survey, and it was confirmed that the cost reduction effect is 39% ~ 93% compared to the existing method. CONCLUSIONS : In addition to overseas business, it is expected that it will have a positive effect on research time and cost reduction by using drone in traffic survey in domestic area where labor supply is not easy or basic data is insufficient.

• 한국정밀공학회지
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• 제15권3호
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• pp.18-23
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• 1998

This paper describes a research work of developing a computer-aided design of blanking and piercing for irregular-shaped sheet metal products. An approach to the CAD system is based on the knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoLISP on the AutoCAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, production feasibility check, and strip layout module. Based on knowledge-based rules, the system is designed by considering several factors, such as radius and angle of bend. material and thickness of product, complexities of blank geometry and punch profile, and availability of press. This system is capable of unfolding a formed sheet metal part to give flat pattern and automatically account for the adjustment of bend allowances to match tooling requirements by checking the dimensions and relationships of parts of the folded product. Also this system can carry out a process planning which is obtained from results of irregular shape of product that was successful in production feasibility check module according to flat pattern layout and generate strip layout drawing in graphic forms. The developed system provides its efficiency for flat pattern layout, and strip layout for the irregularly shaped sheet metal products.

• 한국지반공학회지:지반
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• 제10권2호
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• pp.69-84
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• 1994

본 연구에서는 불안정한 사면의 효율적 보강을 위해 앵커 또는 폐타이어 벽체 공법의 적용성을 설계측면에서 검토하였다. 이를 위해, 앵커 또는 폐타이어 벽체가 설치된 보강사면의 외적안정해석법 제시가 우선 이루어졌으며, 또한 Meyerhof 지지력 이론 및 횡하중을 받는 말뚝단면의 발생응력분포 실험결과를 토대로 벽체 자체의 내적안정에 관련된 앵커 또는 폐타이어에서 발휘되는 수동저항력 예측을 위한 이론식을 제시하였다. 본 연구에서 제시된 수동저항력 계산식의 적합성 검토를 위해 Murray 인발실험결과와의 비교가 이루어졌으며, 아울러 강재보강띠를 적용하는 일반 보강토벽체 공법과 설계상의 장점 등에 관해 비교도 이루어졌다. 최종적으로는 앵커 또는 폐타이어 벽체가 설치된 보강사면 설계예를 제시하여 이에 대한 안정검토 및 겨로가분석이 수행되었으며, 기존 불안정한 사면의 경사도를 낮추어 안정성을 확보하는 공법과의 비교를 통해 앵커 또는 폐타이어 벽체공법의 효율성 검토도 이루어졌다.

• 한국입자에어로졸학회지
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• 제12권4호
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• pp.115-126
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• 2016

Numerical analysis was done to evaluate the movement of the particles and the fluid inside of the cyclone-bag hybrid dust collector. Flow discharged from the cyclone in the hybrid particle collector has swirl pattern, and it results in the biased flow to the bag filters and deteriorates the collection performance of the bag filter. The current study is to evaluate the effect of the duct lengths and the baffle arrays in the connection duct by the computational methods. Main concerns of the analysis are how to improve the uniformity of the internal flow between the cyclone and the bag filter. Numerical analysis was done to check the particle removal efficiencies of the system with respect to the flow characteristics which is expressed in RMS values of the upward flow inside of the connection duct. The flow pattern inside of the connection duct is evaluated under different the duct lengths and the baffle arrays. In case of the reference geometry the RMS value of inside flow was 56.7%, and the value was decreased to 30.1% by controlling the lengths of duct. The effects of baffle was also evaluated, the RMS value of flow could be decreased 55.2% and so on. But the pressure drop across the baffles becomes high and the system efficiency becomes lower.

• 한국통신학회논문지
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• 제40권7호
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• pp.1457-1467
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• 2015

해양 통신을 위한 VHF 대역 데이터 통신 시스템(VHF Data Exchange System: VDES)은 송수신단의 종류에 따라 서로 다른 주파수 대역을 사용하도록 설계되어 있으며, 육상국으로부터 멀리 떨어진 선박국에게 육상국과 연결성을 보장하기 위해 제안된 ASO-TDMA (Ad-hoc Self-Organizing TDMA) MAC 프로토콜을 이용하여 다중-홉 통신을 수행하는 경우에 주파수 채널간 부하 불균형 문제가 발생한다. 본 논문에서는 이러한 주파수 채널간 부하 불균형 문제를 해결하기 위해 통계적 기하(stochastic geometry) 모델링을 도입한다. 이를 기반으로 동일 홉 영역에서의 공간적 자원 재사용률을 분석하고, 각 홉 영역 별로 최적의 자원 할당을 통해 채널간의 부하 불균형 문제를 해결하여 자원 활용도를 극대화하는 것을 보인다.