• 센서학회지
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• 제30권2호
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• pp.88-93
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• 2021

In this paper, a folding sensor based on capacitance is proposed. The sensor was developed to sense the length and angle data for the milli-scale actuators without causing any interference to the actuating joints. For the sensing and testing the robotic joint with reducing the cost and complexity aspects of manufacturing, a simple composition was adopted. The sensor comprises a pair of copper tapes, papers, and wires. The complete sensing unit is constructed by bonding the tapes with the papers and soldering the wire to the copper parts. For accuracy, a teensy 4.0 board, which has a 12-bit ADC resolution, is employed. Furthermore, the sensed analog data is not translated into the unit of capacitance for accuracy; however, it is filtered using a low-pass filter and subsequently, a Butter-worth filter. The data obtained demonstrate a periodic waveform, which implies that the data are in good agreement with the hypothesis set prior to the experiments. Compared to other milli-scale sensors, this could be a better option for sensing the length and angle data for milliscale actuators.

• Steel and Composite Structures
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• 제42권4호
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• pp.489-499
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• 2022

This paper proposes a numerical optimization method to design the mesoscale architecture of textile composite for simultaneously enhancing mechanical and thermal properties, which compete with each other making it difficult to design intuitively. The base cell of the periodic warp and fill yarn system is served as the design space, and optimal fibre yarn geometries are found by solving the optimization problem through the proposed method. With the help of homogenization method, analytical formulae for the effective material properties as functions of the geometry parameters of plain-woven textile composites were derived, and they are used to form the inverse homogenization method to establish the design problem. These modules are then put together to form a multiobjective optimization problem, which is formulated in such a way that the optimal design depends on the weight factors predetermined by the user based on the stiffness and thermal terms in the objective function. Numerical examples illustrate that the developed method can achieve reasonable designs in terms of fibre yarn paths and geometries.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.267-280
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• 2022

Multiscale structure has attracted significant interest due to its high stiffness/strength to weight ratios and multifunctional performance. However, most of the existing concurrent topology optimization works are carried out under deterministic load conditions. Hence, this paper proposes a robust concurrent topology optimization method based on the bidirectional evolutionary structural optimization (BESO) method for the design of structures composed of periodic microstructures subjected to uncertain dynamic loads. The robust objective function is defined as the weighted sum of the mean and standard deviation of the module of dynamic structural compliance with constraints are imposed to both macro- and microscale structure volume fractions. The polynomial chaos expansion (PCE) method is used to quantify and propagate load uncertainty to evaluate the objective function. The effective properties of microstructure is evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The proposed method is a non-intrusive method, and it can be conveniently extended to many topology optimization problems with other distributions. Several numerical examples are used to validate the effectiveness of the proposed robust concurrent topology optimization method.

• International Journal of Internet, Broadcasting and Communication
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• 제15권2호
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• pp.60-72
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• 2023

The purpose of this study is to measure the change in evacuation time at high schools according to the change in hallway width using an evacuation simulation program and to analyze the result of such change. In order to measure the evacuation time according to the change in the hallway width according to the 「Rules on the Standards for Evacuation and Fire Protection Structures of Buildings」 and to analyze the change in evacuation time resulted from the increase in the number of occupants, a scenario was constructed by applying the 「performance-oriented design method and standard for firefighting facilities, etc.」. As a result of the experiment, it was found that the evacuation time was the shortest when the width of the hallway was the widest, which was 3m. On the other hand, the evacuation time took the longest at 1.8m, which was the width of the second narrowest hallway. For the safety of high school students who spend a lot of time at school, it is necessary to secure a wide hallway width when building a new school or to provide periodic safety education in the case of an existing school whose hallways are considered narrow.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.390-391
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• 2022

최근 미국에서는 민간 우주개발업체인 스페이스 x가 스타링크 사업을 통해 저궤도 위성을 발사할 계획이며, 현재까지는 900여개의 위성을 발사하였다. 구체적으로는 Ku 대역과 ka 대역을 갖는 위성을 운용할 계획이며 광대역 신호의 전송을 위해 V 대역을 갖는 7518개 위성을 고도 340 km에 발사할 계획이다. 따라서, 운항중인 선박에서도 저궤도 위성을 통한 무선통신이 가능하게 되며, 다양한 솔루션이 제공될 계획이다. 본 연구에서는 3차원 결합구조를 가지는 코프레너 선로 구조에 대한 RF 특성을 연구하였으며, 이를 통해 완전집적형 해양무선통신 반도체 SoC (System on Chip)를 구현하기 위한 RF소자의 개발가능성을 검토하였다.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.199-204
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• 2023

Periodic assessment of reservoir capacity is essential for better water resources management and planning for the future water use. Reservoirs and water storage structures raised on the rivers are subjected to sedimentation and he sedimentation is caused by deposition of eroded sediment particles carried by the streams. Knowledge of reservoir sedimentation is important to estimate avaliable storage capacity for optimum reservoir operation and scheduling water release. In recent years, remote sensing and GIS techniques have emerged as an important tool in carrying out reservoir capacity analysis and water management. The reduction in storage capacity as compared to the original capacity at the time of reservoir impounding is indicative of sediment deposition. In this study, the application of GIS and remote sensing techniques were applied to assess the sediment deposition, losses in the reservoir storage and the revised cumulative capacity. Satellite images covering Pyodongdong reservoir were analyzed using Erdas Imagine and ArcGIS softwares.Cumulative capacities at different levels were also calculated and we estimated that the revised live storage was 84.2Mft3 in 2021 and 64.3Mft3 in 2022 while the original capacity was 22.8 and 53.6Mft3 in 2021 and 2022.

• 대한소아치과학회지
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• 제39권4호
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• pp.390-396
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• 2012

저위교합이란 치아가 출은 이후 유착 등의 원인으로 맹출이 정지되어 주위조직이 정상적으로 성장함에 따라 정상교합보다 낮아진 상태를 말한다. 저위교합을 방치하는 경우 이환치의 만기잔존과 대합치의 정출 및 인접치의 경사에 따른 공간상실, 교합압과 식편압입으로 인한 인접치의 치주 조직 파괴와 치아우식 감수성의 증가, 계승치의 맹출경로 변위 또는 매복과 같은 문제점이 발생할 수 있으므로 정기검진을 통한 진단과 이에 따른 적절한 치료가 필요하다. 저위교합을 보이는 유구치의 치료방법으로는 후속 영구치의 유무, 저위교합의 발생 시기 및 진단 시기, 저위교합의 정도 등에 따라서 주기적인 관찰, 보존적 접근 방법, 수복치료, 교정적 방법을 통한 공간확장술과 발치 등이 있다. 본 증례에서는 상악 제2유구치의 저위교합 및 제2소구치 치배의 변위를 보이는 3명의 환아를 대상으로 가철성 교정장치를 이용한 공간확장술 및 유구치의 발치를 시행함으로써 변위되었던 제2소구치 치배의 정상 맹출을 유도하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제35권3호
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• pp.167-173
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• 2013

Purpose: The aim of this study is to analyze the series of panoramic radiograph of implant patients using the system to measure peri-implant crestal bone loss according to the elapsed time from fixture installation time to more than three years. Methods: Choose 10 patients having 45 implant fixtures installed, which have series of panoramic radiograph in the period to be analyzed by the system. Then, calculated the crestal bone depth and statistics and selected the implant in concerned by clicking the implant of image shown on the monitor by the implemented pattern recognition system. Then, the system recognized the x, y coordination of the implant and peri-implant alveolar crest, and calculated the distance between the approximated line of implant fixture and alveolar crest. By applying pattern recognition to periodic panoramic radiographs, we attained the results and made a comparison with the results of preceded articles concerning peri-implant marginal bone loss. Analyzing peri-implant crestal bone loss in a regression analysis periodic filmed panoramic radiograph, logarithmic approximation had highest $R^2$ value, and the equation is as shown below. $y=0.245Logx{\pm}0.42$, $R^2=0.53$, unit: month (x), mm (y) Results: Panoramic radiograph is a more wide-scoped view compared with the periapical radiograph in the same resolution. Therefore, there was not enough information in the radiograph in local area. Anterior portion of many radiographs was out of the focal trough and blurred precluding the accurate recognition by the system, and many implants were overlapped with the adjacent structures, in which the alveolar crest was impossible to find. Conclusion: Considering the earlier objective and error, we expect better results from an analysis of periapical radiograph than panoramic radiograph. Implementing additional function, we expect high extensibility of pattern recognition system as a diagnostic tool to evaluate implant-bone integration, calculate length from fixture to inferior alveolar nerve, and from fixture to base of the maxillary sinus.

• 한국인터넷방송통신학회논문지
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• 제16권6호
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• pp.141-146
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• 2016

굴착 현장 인접 구조물의 안정성을 확보하기 위해 현장 주변 지반의 변형을 모니터링하는 것은 중요하다. 지반특성과 굴착 깊이에 따라 굴착 중 벽체의 변형이 다르게 발생하며, 이를 정확하게 예측하는 것은 불가능하다. 따라서 굴착지지 벽체 후방에 인클리노미터를 탑재한 센서를 설치하여 이를 모니터링한다. 본 논문에서는 굴착과정에서 벽체의 변형을 모니터링하기 위해 무선 센서 노드를 사용한 모니터링 시스템을 설계하였다. 또한 배터리 기반의 센서 노드의 수명을 연장하기 위해 굴착 진행 과정과 인클리노미터의 계측 값에 따라 위험도 등급을 설정하고 해당 등급에 따라 활성/휴면 구간을 적응적으로 변경하는 기법을 제안하였다. 지연시간 분석을 통해 제안기법은 굴착현장과 같이 위험도가 다른 데이터가 동적으로 발생하는 환경에서 고정 듀티사이클링 기법에 비해 지연시간을 크게 줄일 수 있음을 확인한다.

• 한국전자파학회논문지
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• 제26권3호
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• pp.311-316
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• 2015

본 논문에서는 저항성 sheet를 이용한 광대역 박형 흡수체 설계법을 제안한다. 제안된 흡수체의 등가회로는 직렬 RLC 공진회로와 종단이 단락된 전송선으로 이루어진다. 이 등가회로를 바탕으로 임의의 설계주파수에서 흡수체가 ${\lambda}/4$보다 얇은 두께를 가지면서도, 광대역 흡수율 특성을 가지는 세가지 조건을 정리하였다. 수치해석을 통해 이를 동시에 만족하는 R, L, C 소자 값을 구했다. 구한 등가 R, L, C값은 특정한 chip 저항이나 표면저항을 가지는 십자 모양의 구조로써 구현이 가능하다. 이러한 설계법을 설계 중심주파수 3 GHz에서 적용해서 두께가 18.75 mm(전기적 길이 $67.5^{\circ}$)이고, 90 % 흡수율 기준으로 116 % 대역폭을 갖는 광대역 흡수체를 설계하였다.