• 한국ITS학회 논문지
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• 제18권3호
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• pp.58-67
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• 2019

한전의 저압전송전선로로 이용되고 있는 지중저압접속함은 지중선로의 분기나 접속을 목으로 하고 있다. 지중저압접속함은 거리의 미관을 고려하는 효용성에 비하여 여름철 집중호우나 도로의 침수에 의하여 감전사고가 발생하는 등 안전대책이 필요하다. 본 논문에서는 지중저압접속함 내부에 온습도, $CO_2$, 수위, 가속도, 진동 센서를 장착하고 센서 데이터를 지그비모듈을 이용하여 지상으로 데이터를 전송한다. 지상과의 통신을 위한 안테나(볼티드 안테나)를 제안하여 이를 통한 데이터 수신을 확인하였다. 전송된 데이터는 LF 모드 및 HEX모드에서 완벽한 수신 성공률이 확인되었으며, 볼티드 안테나는 난환경 사태에서 실험한 결과 지중상태와 수중상태의 차이는 보이고 있으나, 지중저압접속함으로부터 10m 정도 떨어진 지상과의 통신에는 충분히 수신감도라고 판단되었다. 수신된 데이터는 PC기반의 GUI를 통해 확인할 수 있었다.

• Earthquakes and Structures
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• 제15권6호
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• pp.639-654
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• 2018

Rocking motion have been used for achieving the 'resilient buildings' against earthquakes in recent studies. Low-rise buildings, unlike the tall ones, because of their small aspect ratio tend to slide rather than move in rocking mode. However, since rocking is more effective in seismic response reduction than sliding, it is desired to create rocking motion in low-rise buildings too. One way for this purpose is making the building's structure rock on its internal bay(s) by reducing the number of bays at the lower part of the building's skeleton, giving it a mushroom form. In this study 'mushroom skeleton' has been used for creating multi-story rocking regular steel buildings with square plan to rock on its one-by-one bay central lowest story. To show if this idea is effective, a set of mushroom buildings have been considered, and their seismic responses have been compared with those of their conventional counterparts, designed based on a conventional code. Also, a set of similar buildings with skeleton stronger than code requirement, to have immediate occupancy (IO) performance level, have been considered for comparison. Seismic responses, obtained by nonlinear time history analyses, using scaled three-dimensional accelerograms of selected earthquakes, show that by using appropriate 'mushroom skeleton' the seismic performance of buildings is upgraded to mostly IO level, while all of the conventional buildings experience collapse prevention (CP) level or beyond. The strong-skeleton buildings mostly present IO performance level as well, however, their base shear and absolute acceleration responses are much higher than the mushroom buildings.

• 한국구조물진단유지관리공학회 논문집
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• 제23권5호
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• pp.118-125
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• 2019

이 연구에서는 풍력-태양광 하이브리드 가로등 구조물에 대한 동적 응답을 계측하여, 서로 다른 터빈을 적용하였을 때의 진동 특성 및 공진현상을 비교하였다. 2엽 및 3엽 풍력터빈을 적용하였으며, 하이브리드 가로등이 가지고 있는 진동 특성은 가동 중인 조건에서의 동특성과 가진력을 비교하여 분석하였다. 최근 제안된 방법을 통해 가속도 계측자료를 이용하여 변위 응답을 추정하였고, 2엽 풍력터빈을 적용한 경우 동적 변위 응답의 진폭은 공진 하의 조건에서 4~6cm 범위에 있고, 3엽 풍력터빈을 적용한 경우에는 공진이 발생하지 않아 변위는 2mm 이내로 제한됨을 알 수 있었다.

• 한국융합학회논문지
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• 제10권8호
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• pp.145-151
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• 2019

본 연구에서는 고층아파트 승강로 근접세대에 대한 진동 및 소음저감대책의 일환으로 승강기 가이드 레일 브라켓에 방진라이너를 적용하여 그 효과들을 분석하였다. 방진라이너 성능 분석결과, 카 측에서는 65.49%, 카운터 측에서는 90.05%의 방진성능을 확인할 수 있었다. 그러므로, 엘리베이터 가이드 레일 브라켓의 방진라이너의 진동저감 효과를 상당히 가지고 있다. 방진라이너 적용의 경우 제진빔 적용에 비해 승강기 운행통로(승강로) 면적은 7.26 ~ 22.22% 감소, 재료비와 설치비는 3,840,000원 ~ 9,780,000원의 절감효과를 확인할 수 있었다. 또한, 중량물인 제진빔에 비해 경량물인 방진라이너를 적용할 경우, 설치현장의 안전사고 예방에 효과가 클 것으로 사료된다.

• 대한치과교정학회지
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• 제51권2호
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• pp.86-94
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• 2021

Objective: This study aimed to investigate the effect of micro-osteoperforations (MOPs) on external apical root resorption (EARR) during the initial orthodontic alignment phase of maxillary anterior crowding. Methods: Thirty patients (25 females, 5 males; mean age, 22.66 ± 3.27 years) who presented with moderate crowding of the upper labial segment and underwent extraction-based fixed appliance treatment were recruited. They were randomly allocated to receive adjunctive therapy with MOPs (n = 15) or treatment with fixed appliances only (control group; n = 15). EARR was measured from long-cone periapical radiographs taken at the start and the sixth month of treatment. A correction factor for the enlargement difference was used to calculate EARR. Data were analyzed with descriptive statistics and repeated-measures analysis of variance. Results: The mean root lengths of 168 teeth were measured and showed no statistically significant difference (p > 0.05) after six months of fixed appliance treatment in the MOP (mean difference [MD] = 0.13 mm; 95% confidence interval [CI] = -0.10-0.35) and control group (MD = 0.14 mm; 95% CI = -0.10-0.37). Most of the roots in the MOP and control groups (42.86% and 52.38%, respectively) showed only mild resorption. Less than 8% of the roots in both groups (7.14% in the MOP group and 4.76% in the control group) showed moderate resorption. Conclusions: Acceleration of orthodontic tooth movement with adjunctive MOPs therapy during the alignment phase does not exacerbate EARR in patients with moderate crowding of the upper labial segment in comparison with controls.

• 방송공학회논문지
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• 제26권6호
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• pp.778-789
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• 2021

최근 다양한 분야에서 뛰어난 성능을 나타내는 Convolutional Neural Network(CNN)모델을 모바일 기기에서 사용하기 위한 다양한 연구가 진행되고 있다. 기존의 CNN 모델은 모바일 장비에서 사용하기에는 가중치의 크기가 크고 연산복잡도가 높다는 문제점이 있다. 이를 해결하기 위해 가중치의 표현 비트를 낮추는 가중치 양자화를 포함한 여러 경량화 방법들이 등장하였다. 많은 방법들이 다양한 모델에서 적은 정확도 손실과 높은 압축률을 나타냈지만, 대부분의 압축 모델들은 정확도 손실을 복구하기 위한 재학습 과정을 포함시켰다. 재학습 과정은 압축된 모델의 정확도 손실을 최소화하지만 많은 시간과 데이터를 필요로 하는 작업이다. Weight Quantization이후 각 층의 가중치는 정수형 행렬로 나타나는데 이는 이미지의 형태와 유사하다. 본 논문에서는 Weight Quantization이후 각 층의 정수 가중치 행렬을 이미지의 형태로 비디오 코덱을 사용하여 압축하는 방법을 제안한다. 제안하는 방법의 성능을 검증하기 위해 ImageNet과 Places365 데이터 셋으로 학습된 VGG16, Resnet50, Resnet18모델에 실험을 진행하였다. 그 결과 다양한 모델에서 2%이하의 정확도 손실과 높은 압축 효율을 달성했다. 또한, 재학습 과정을 제외한 압축방법인 No Fine-tuning Pruning(NFP)와 ThiNet과의 성능비교 결과 2배 이상의 압축효율이 있음을 검증했다.

• Structural Engineering and Mechanics
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• 제78권2호
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• pp.125-134
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• 2021

In this paper, the effects of Tuned Mass dampers (TMDs) on the reduction of the vertical vibrations of a real horizontally curved steel box-girder bridge due to different traffic loads are numerically investigated. The performance of TMDs to reduce the bridge vibrations can be affected by the parameters such as dynamic characteristics of TMDs, the location of TMDs, the speed and weight of vehicles. In the first part of this study, the effects of mass ratio, damping percentage, frequency ratio, and location of TMDs on the performance of TMDs to decrease vertical vibrations of different sections of bridge deck are evaluated. In the second part, the performance of TMD is investigated for different speeds and weights of traffic loads. Results show that the mass ratio of TMDs is the more effective parameter in reducing imposed vertical vibration in comparison with the damping ratio. Furthermore, it is found that TMD is very sensitive to its tuned frequency, i.e., with a little deviation from a suitable frequency, the expected performance of TMD significantly decreased. TMDs have a positive and considerable performance at certain vehicle speeds and this performance declines when the weight of traffic loads is increased. Besides, the results reveal that the highest impact of TMD on the reduction of the vertical vibrations is when free vibrations occur for the bridge deck. In that case, maximum reductions of 24% and 59% are reported in the vertical acceleration of the bridge deck for the forced and free vibration amplitudes, respectively. The maximum reduction of 13% is also obtained for the maximum displacement of the bridge deck. The results are mainly related to the resonance condition.

• The Journal of Advanced Prosthodontics
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• 제14권6호
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• pp.360-368
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• 2022

PURPOSE. This study assessed the physical and mechanical properties of interim crown materials fabricated using various digital techniques after accelerated aging. MATERIALS AND METHODS. Three groups of interim dental restorative materials (N = 20) were tested. The first group (CO) was fabricated using a conventional manual method. The second group (ML) was prepared from prefabricated resin blocks for the milling method and cut into specimen sizes using a cutting disc. The third group (3D) was additively manufactured using a digital light-processing (DLP) 3D printer. Aging acceleration treatments using toothbrushing and thermocycling simulators were applied to half of the specimens corresponding to three years of usage in the oral environment (N = 10). Surface roughness (Ra), Vickers microhardness, 3-point bending, sorption, and solubility tests were performed. A 2-way analysis of variance (ANOVA) and Fisher's multiple comparison test were used to compare the results among the groups. RESULTS. The mean surface roughness (Ra) of the resin after accelerated aging was significantly higher in the CO and ML groups than that before aging, but not in the 3D group. All groups showed reduced hardness after accelerated aging. The flexural strength values were highest in the 3D group, followed by the ML and CO groups after accelerated aging. Accelerated aging significantly reduced water sorption in the ML group. CONCLUSION. According to the tested material and 3D printer type, both 3D-printed and milled interim restoration resins showed higher flexural strength and modulus, and lower surface roughness than those prepared by the conventional method after accelerated aging.

• Smart Structures and Systems
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• 제29권1호
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• pp.77-91
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• 2022

Various monitoring systems have been implemented in civil infrastructure to ensure structural safety and integrity. In long-term monitoring, these systems generate a large amount of data, where anomalies are not unusual and can pose unique challenges for structural health monitoring applications, such as system identification and damage detection. Therefore, developing efficient techniques is quite essential to recognize the anomalies in monitoring data. In this study, several machine learning techniques are explored and implemented to detect and classify various types of data anomalies. A field dataset, which consists of one month long acceleration data obtained from a long-span cable-stayed bridge in China, is employed to examine the machine learning techniques for automated data anomaly detection. These techniques include the statistic-based pattern recognition network, spectrogram-based convolutional neural network, image-based time history convolutional neural network, image-based time-frequency hybrid convolution neural network (GoogLeNet), and proposed ensemble neural network model. The ensemble model deliberately combines different machine learning models to enhance anomaly classification performance. The results show that all these techniques can successfully detect and classify six types of data anomalies (i.e., missing, minor, outlier, square, trend, drift). Moreover, both image-based time history convolutional neural network and GoogLeNet are further investigated for the capability of autonomous online anomaly classification and found to effectively classify anomalies with decent performance. As seen in comparison with accuracy, the proposed ensemble neural network model outperforms the other three machine learning techniques. This study also evaluates the proposed ensemble neural network model to a blind test dataset. As found in the results, this ensemble model is effective for data anomaly detection and applicable for the signal characteristics changing over time.

• Earthquakes and Structures
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• 제24권1호
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• pp.37-51
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• 2023

Türkiye has made significant changes and updates in both seismic risk maps and design codes over time, as have other countries with high seismic risk. In this study, the last two seismic design codes and risk maps were compared for the Aegean Region (Western Türkiye) where the earthquake risk has once again emerged with the 2020 Izmir Earthquake (Mw=6.9). In this study, information about the seismicity of the Aegean Region was given. The seismic parameters for all provinces in the region were compared with the last two earthquake risk maps. The spectral acceleration coefficients of all provinces have increased and differentiated with the current seismic hazard map as a result of the design spectra used on a regional basis have been replaced by the geographical location-specific design spectra. In addition, section damage limits were obtained for all provinces within the scope of the last two seismic design codes. Structural analyses for a sample reinforced-concrete building were made separately for each province using pushover analysis. The deformations in the cross-sections were compared with the limit states corresponding to the damage levels specified in the last two seismic design codes for the region. Target displacement requests for all provinces have decreased with the current code. The differentiation of geographical location-specific design spectra both in the last two seismic design code and between provinces has caused changes in section damages and building performance levels. The main aim of this study is to obtain and compare both seismic and structural analysis results for all provinces in the Aegean Region (Western Türkiye).