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다채널 음향방출 신호에 대한 딥러닝을 통한 3차원 위치 표정
임소영(Soyoung Lim),서호건(Hogeon Seo),이항로(Hang-Lo Lee),김진섭(Jin-Seop Kim) 한국비파괴검사학회 2022 한국비파괴검사학회지 Vol.42 No.1
본 연구에서는 다채널 음향방출 신호로부터 발진 위치 좌표를 예측하는 딥러닝 모델을 활용함에 있어서 손실함수 및 데이터 전처리 조건에 따른 성능을 평가했다. 7 채널의 음향방출 신호를 이미지 형태로 모델의 입력으로 활용하였고, 출력은 X, Y, Z 좌표를 각각 출력하는 경우와 한 번에 출력하는 경우를 고려하였다. 딥러닝 모델로는 EfficientNet B3을 활용했으며, 평가지표는 평균 절대 오차를 채택했다. 손실함수로는 평균제곱오차와 평균절대오차, 시계열 데이터 전처리 기법으로는 스케일링(MinMaxScaler, StandardScaler, MaxAbsScaler), 신호 전처리(Abs, MA, LPF), 샘플링 길이(1024, 512, 342)에 따른 위치 표정 성능을 비교했다. 그 결과, 손실함수로는 평균제곱오차를 사용하는 것이 유리했고, 스케일링으로는 MaxAbsScaler가 효과적이었다. MaxAbsScaler 적용 후, 절대값을 취해준 후 저역통과필터나 이동평균을 적용한 데이터의 단순화는 성능에 악영향을 미쳤다. MaxAbsScaler 적용 후, 512 개만 샘플링 했을 때 더 좋은 성능을 보였고, X, Y, Z의 각 좌표를 개별적으로 추정하는 방식이 최고 성능을 보였다. This study evaluated source localization performance based on the loss function and preprocessing conditions when using a deep learning model that predicts the source coordinates from multi-channel acoustic emission signals. Signals of seven channels were fed as input into a model in the form of an image, and two output cases were considered: outputting X, Y, and Z coordinates one at a time and outputting them at the same time. EfficientNet B3 was used as the model, and the mean absolute error was adopted as the performance index. Mean square error and mean absolute error were used as loss functions. The performance was compared with respect to scaling (MinMaxScaler, StandardScaler, MaxAbsScaler), preprocessing (Abs, MA, LPF), and sampling length (1024, 512, 342). The results show the advantage of using the mean squared error and the effectiveness of MaxAbsScaler. After applying MaxAbsScaler, the simplification of the data, such as taking the absolute value, and applying a low-pass filter or moving average method, had an adverse effect on the performance. The MaxAbsScaler exhibited better performance when 512 samples were input, and each coordinate of X, Y, and Z was separately estimated.
위상잠금 중파장 적외선 열화상 기법에 의한 결함 계측에서 측정 대상체의 재질에 따른 위상잠금 주파수 연구
박일철(Il-Chul Park),김상채(Sang-Chae Kim),이항서(Hang-Seo Lee),김한섭(Han-Sub, Kim),정현철(Hyun-Chul Jung),김경석(Kyeong-Suk Kim) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.9
Three types of samples with defects were measured by lock-in med-IR (infrared) thermography with various lock-in frequencies for different materials. The lock-in method can be used to detect defects when an external energy source is applied to the object, the non-uniformity of the incident thermal energy distribution is eliminated, and the camera"s measurement cycle is synchronized with the load cycle of the incident energy source. For inspecting samples with defects, results of thermal images are analyzed when three types of materials, i.e., SM45C, STS316L, and AL6061 are tested and three lock-in frequencies, i.e., 0.08, 0.1, and 0.12 Hz are applied. In this study, the optimal lock-in frequencies were determined by comparing the results of each material and lock-in frequency measured using the mid-IR camera.
듀얼 빔 전단간섭계를 이용한 압연방향에 따른 기계구조용 탄소강의 면내 변위 정량적 측정에 대한 연구
강찬근(Chan-Geun Kang),김상채(Sang Chae Kim),김한섭(Han-Sub Kim),이항서(Hang-Seo Lee),정현일(Hyun-il Jung),정현철(Hyun-Chul Jung),송재근(Jae-Geun Song),김경석(Kyeong-suk Kim) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.4
In this paper, an in-plane deformation measuring system using a dual-beam shear interferometer was constructed to measure the in-plane deformation of the measuring object. The in-plane deformation of the object was quantitatively measured according to the load and surface treatment conditions of the object. We also verified the reliability of the proposed technique by simultaneously performing the technique with an electronic speckle pattern interferometry system (ESPI), which is another laser application measurement technology. Digital shearography directly measures the deformation gradient or strain components and has the advantages of being full-field, noncontact, highly sensitive, and robust. It offers a much higher measurement sensitivity compared with noncoherent measurement methods and is more robust and applicable to in-field tests.
Ju-Yeop Shin(신주엽),Hyeong-Jong Lim(임형종),Hang-Seo Lee(이항서),Han-Sub Kim(김한섭),Hyun-Chul Jung(정현철),Kyeong-suk Kim(김경석) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.1
The spacer, which is located between the bucket and the arm of an excavator, has a role in preventing damage to the excavator arm during excavation work. When the durability of the spacer is increased, the lifetime of the arm can be extended and the processing costs can be reduced. To increase the durability of the spacer, tungsten carbide (WC) coating was applied on the surface of a spacer using the plasma transferred arc (PTA) process. The confirm the durability, a wear test using a pin-on disk type of wear testing machine was done under the given conditions and the wear amount on the surface of a tested specimen was measured using reflective digital holography. The results were compared with that of ALPHA-STEP.
들소(Bos javanicus)로 밝혀진 호랑이 기념품: DNA 염기서열 분석에 의한 종 확인
이서진,현지연,민미숙,이무영,이항,Lee, Seo-Jin,Hyun, Jee Yun,Min, Mi-Sook,Lee, Mu-Yeong,Lee, Hang 대한수의학회 2013 大韓獸醫學會誌 Vol.53 No.4
Tigers are one of the most endangered species over the world and protected internationally or locally. However, they are still traded illegally for the Traditional East Asia Medicine or souvenirs / mementos as well as fake products. In the present study, to identify the species of the specimen known as the tiger's genitalia that was sold for mementos in China, two approaches of genetic tools and morphological comparisons were applied. On the basis of the entire sequences of mitochondrial cytochrome b gene (1,140 bp), the result of nucleotide comparisons showed that the specimen examined here is matched with banteng, Bos javanicus (Identities = 1,138/1,140; 99%). In addition, the examination of external morphological characters revealed that the genitalia of the specimen is much more similar to the one of cows, not to tigers. The outcomes highlighted that there are still some fake products of tigers traded in market and molecular genetic tools could help identifying species of wildlife products.