• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.837-838
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.621-622
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• 2012

• Smart Structures and Systems
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• v.13 no.6
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• pp.959-974
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• 2014

Hand-Arm Vibration Syndrome (HAVS) is a group of diseases caused by exposure of the hands to vibration while operating the hand held power tools such as road breaker, drilling machine, demolition hammer in construction works. In this paper, area-changed capacitive micro-accelerometer is designed to measure the vibration exposure on worker's hand when operating a drilling machine on various blocks such as clay block, paver block and solid cement block. The design process includes mathematical modelling of micro-accelerometer and simulations are done using INTELLISUITE 8.6. Experimental results are taken for various blocks surfaces using conventional and micro-accelerometer. Comparisons show that usage of area-changed micro-accelerometer for Hand-arm vibration monitoring provides better sensitivity, which in turn reduces the risk of HAVS in workers.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.2
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• pp.159-167
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• 2020

In actual battlefield environment, IFF radar plays an important role in distinguishing friend or foe targets and assigning unique identification code to management. Performance of IFF radar is greatly affected by radio environment including atmosphere and terrain, target maneuvering and operation mode. In this paper, M&S tool is consisted of interrogator(IFF radar) and answering machine(target) for radar performance analysis. The wave propagation model using APM(Advanced Propagation Model) and radar actuator system were modeled by considering beam waveform of individual operation beam mode. Using this tool, IFF radar performance was analyzed through two experimental results. As a result, it is expected that performance of IFF radar can be predicted in the operational environment by considering target maneuvering and operation beam mode.

• Journal of the Korea Convergence Society
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• v.11 no.2
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• pp.17-22
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• 2020

In this paper, we measured the user's EEG signal and classified the EEG signal using the Support Vector Machine algorithm and measured the accuracy of the signal. An experiment was conducted to measure the user's EEG signals by separating men and women, and a single channel EEG device was used for EEG signal measurements. The results of measuring users' EEG signals using EEG devices were analyzed using R. In addition, data in the study was predicted using a 80:20 ratio between training data and test data by applying a combination of specific vectors with the highest classifying performance of the SVM, and thus the predicted accuracy of 93.2% of the recognition rate. This paper suggested that the user's EEG signal could be recognized at about 93.2 percent, and that it can be performed only by simple linear classification of the SVM algorithm, which can be used variously for biometrics using EEG signals.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.729-735
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• 2000

Moisture loss of fresh fruits and vegetables is a main cause of deterioration. It resulted not only in the direct quantitative loss, but also in change in appearance, texture and nutrition. To reduce the loss of moisture content during the distribution in the market, fresh products are packaged using plastic films. But, most of the fresh products are packaged manually in Korea. In order to minimize the labor requirement, the packaging machine for fruits and vegetables was developed and tested. Prototype was composed of film feeding unit, bag former, products feeding conveyor, film feeding roller, center sealer, end sealer and discharge conveyor. Green peppers, carrots and perilla leaves were tested with prototype. Prototype could pack 1780, 1390, 1780 bags per hour at the feeding speed of 0.08m/s respectively and 2250, 1810, 2640bags per hour at the feeding speed of 0.10m/s respectively. And packaging speed of green peppers and carrots was improved by 3.7 and 3.4 times compared with manual packaging. The packaging condition with the prototype was good and the products had almost no damages.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.154-161
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• 1995

In order to analysis of the stress distribution around flaws and the interaction effects between fatigue cracks, stress around micro hole was analyzed by Finite Element Method(F.E.M.) and micro hole specimens were tested using rotary bending fatigue machine and twisting fatigue machine to identify stress effects for fatigue cracks initiating from micro holes and interaction effects between micro holes. The results are as follows : Interaction effects of .sigma. $_{y}$for the micro hole side is larger than the large micro hole side when the interval between micro holes is near. Stress concentration factor increase as the diameter of micro hole becomes smaller. But, stress field of micro hole is smaller than that of large micro hole at h .leq. r (h:depth of micro hole, r:radius of micro hole) and that of large hole is larger than that of small micro hole at h >r expect the small range from micro hole.e.

• Journal of Korean Association for Spatial Structures
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• v.23 no.3
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• pp.87-94
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• 2023

Chloride is one of the most common threats to reinforced concrete (RC) durability. Alkaline environment of concrete makes a passive layer on the surface of reinforcement bars that prevents the bar from corrosion. However, when the chloride concentration amount at the reinforcement bar reaches a certain level, deterioration of the passive protection layer occurs, causing corrosion and ultimately reducing the structure's safety and durability. Therefore, understanding the chloride diffusion and its prediction are important to evaluate the safety and durability of RC structure. In this study, the chloride diffusion coefficient is predicted by machine learning techniques. Various machine learning techniques such as multiple linear regression, decision tree, random forest, support vector machine, artificial neural networks, extreme gradient boosting annd k-nearest neighbor were used and accuracy of there models were compared. In order to evaluate the accuracy, root mean square error (RMSE), mean square error (MSE), mean absolute error (MAE) and coefficient of determination (R2) were used as prediction performance indices. The k-fold cross-validation procedure was used to estimate the performance of machine learning models when making predictions on data not used during training. Grid search was applied to hyperparameter optimization. It has been shown from numerical simulation that ensemble learning methods such as random forest and extreme gradient boosting successfully predicted the chloride diffusion coefficient and artificial neural networks also provided accurate result.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.211-217
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• 2021

To predict mechanical properties of secondary hardening martensitic steels, a machine learning ensemble model was established. Based on ANN(Artificial Neural Network) architecture, some kinds of methods was considered to optimize the model. In particular, interaction features, which can reflect interactions between chemical compositions and processing conditions of real alloy system, was considered by means of feature engineering, and then K-Fold cross validation coupled with bagging ensemble were investigated to reduce R2_score and a factor indicating average learning errors owing to biased experimental database.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.321-324
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• 2023

본 연구는 광역시와 광역도 간의 개인적 요인과 건강수준 정도가 우울경험 여부에 영향을 미치는 변수의 중요도를 파악하고자 시도되었다. 본 연구의 자료는 질병관리청의 2021년 지역사회건강조사 데이터를 활용하였다. 광역시의 데이터는 4,602건을 이용하였고, 광역도는 19,545건의 데이터를 이용하였다. 자료 분석에 활용된 빅데이터는 R 4.3.0 for Windows를 활용하여 단어 빈도 분석과 machine learning기법인 Random Forest분석을 실시하였다. 연구결과, train 데이터와 test 데이터의 과적합(overfitting)의 문제는 발생하지 않았으며, machine learning 기법의 분류모델은 약 94% 수준으로 나타났다. 분석 결과 광역시와 광역도 간의 우울경험여부에 미치는 중요도가 각각 다르게 나타났다. 두 지역의 시민에게 미치는 우울경험의 원인을 다르게 접근함으로써 보다 더 효율적인 정책수립이 가능 할 것으로 판단된다.