• 한국지반환경공학회 논문집
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• 제10권7호
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• pp.7-14
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• 2009

압축지수를 구하기 위해 경험적으로 제안되고 있는 상관관계식은 압밀실험 횟수가 작거나 분산이 심한 경우에 간단한 시험으로 획득할 수 있는 토질정수를 이용하여 간편하게 구할 수 있도록 제안되었으나 대부분은 분석대상지역이 국외나 국내의 특정지역에 국한되거나 여러 자료를 통합하여 사용한 경우가 많아 적용하는데 무리가 있다. 따라서 본 연구에서는 지반의 불확실성을 고려한 설계법의 새로운 정립을 목적으로 시험자료의 불확실성을 최대한 줄이기 위해 최근에 수집된 비교적 신뢰성이 큰 광양항 지역을 연구대상지로 선정하였다. 선정지역에서 획득된 압밀시험 자료에 대해 정규성 검증 및 변수 변환을 수행한 후 변수변환된 회귀모형을 통하여 예측식을 제안하였으며, 제안된 변수변환 회귀모형식을 기존의 경험식과 비교하여 제안모형식의 적합성을 검증하였다. 분석결과 Box-Cox 변수변환 후 결정계수가 증가하며 설명력이 향상되고 있음을 확인하였으며 평균제곱예측오차법을 통하여 제안된 모형식이 실험값과 가장 근접한 값을 나타내고 있음을 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권6호
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• pp.171-178
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• 2010

가스관, 송유관 등의 배관구조물은 주요자원의 수송을 책임지는 핵심 지하시설물 중 하나이다. 이들은 사고 및 자연적인 노후화로 인해 국부적인 손상이 발생할 위험에 노출 되어있다. 하지만 대부분의 배관구조물은 지하의 좁은 공간에 복잡하게 연결되어있기 때문에 구조물의 건전성을 지속적으로 모니터링 하는데 어려움이 있었다. 이러한 지금까지 관리방식의 한계점을 극복하기 위해 최근 유비쿼터스 센서 네트워크 기반의 온라인 방식의 상시적 구조물 건전성 평가방법에 대한 연구가 활발히 이뤄지고 있다. 본 논문에서는 전기-역학적 임피던스 기반의 실시간 배관 구조물 건전성 평가방법에 대하여 연구하였다. 배관 구조물에 발생하기 쉬운 볼트 풀림과 균열의 두 가지 국부손상을 가정하였고 압전효과를 가진 PZT와 MFC 센서를 이용하여 구조물의 상태에 따른 임피던스를 계측하여 손상탐색 실험을 수행하였다. 하나의 센서로 가진과 센싱을 동시에 수행할 수 있는 저비용 셀프센싱 기법을 사용하였고 배관 상태에 대한 객관적인 판단을 위해 손상지수인 RMSD 값을 사용하여 계측된 신호를 이용하여 손상의 정도를 정량화 시켰다. 손상여부의 판단을 위해 일반 극치 분포를 이용하여 최적화된 통계적인 정상상태의 임계값을 설정하였다. 위와 같은 실험적 연구과정을 통해 제안된 실시간 배관 구조물 건전성 평가 방법의 타당성과 효율성을 확인해 보았다.

• 문화기술의 융합
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• 제9권4호
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• pp.487-494
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• 2023

본 연구에서는 무료 딥러닝 도구인 R과 텐서플로우에 대한 성능 비교를 수행하였다. 실험에서는 각 도구를 사용하여 6종류의 심층 신경망을 구축하고 10년간의 한국 온도 데이터셋을 사용하여 신경망을 학습시켰다. 구축된 신경망의 입력층 노드 갯수는 10개, 출력층은 5개로 설정 하였으며, 은닉층은 5, 10, 20개로 설정하여 실험을 진행 하였다. 학습 데이터는 2013년 3월 1일부터 2023년 3월 29일까지 서울시 강남구에서 수집된 온도 데이터 3681건을 사용하였다. 성능 비교를 위해, 학습된 신경망을 사용하여, 5일간의 온도를 예측하고 예측된 값과 실제값을 사용하여 평균 제곱근 오차(root mean square error, RMSE)값을 측정하였다. 실험결과, 은닉층이 1개인 경우, R의 학습 오차는 0.04731176이었으며, 텐서플로우는 0.06677193으로 측정되었으며, 은닉층이 2개인 경우에는 R이 0.04782134, 텐서플로 우는 0.05799060로 측정되었다. 전체적으로 R이 더 우수한 성능을 보였다. 우리는 기계학습을 처음 접하는 사용자들에게 두 도구에 대한 정량적 성능 정보를 제공함으로써, 도구 선택에서 발생하는 어려움을 해소하고자 하였다.

• The Journal of Advanced Prosthodontics
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• 제14권2호
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• pp.70-77
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• 2022

PURPOSE. This study evaluated screw loosening and 3D crown displacement after cyclic loading of implant-supported incisor crowns cemented with original titanium bases or with three compatible, nonoriginal components. MATERIALS AND METHODS. A total of 32 dental implants were divided into four groups (n = 8 each): Group 1 used original titanium bases, while Groups 2-4 used compatible components. The reverse torque value (RTV) was evaluated prior to and after cyclic loading (1,200,000 cycles). Samples (prior to and after cyclic loading) were scanned with a microcomputed tomography (micro-CT). Preload and postload files were superimposed by 3D inspection software, and 3D crown displacement analysis was performed using root-mean-square (RMS) values. All datasets were analyzed using one-way ANOVA and Tukey's post hoc analysis. RESULTS. Significant variations were observed in the postload RTV, depending on the titanium base brand (P < .001). The mean postload RTVs were significantly higher in Groups 1 and 2 than in the other study groups. While evaluating 3D crown displacement, the lowest mean RMS value was shown in the original Group 1, with the highest RMS value occurring in Group 4. CONCLUSION. Within the limitations of this in vitro study and under the implemented conditions, it was concluded that the manufacturer brand of the titanium base significantly influenced screw loosening following the fatigue test and influenced 3D crown displacement after cyclic loading.

• The Journal of Advanced Prosthodontics
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• 제10권3호
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• pp.245-251
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• 2018

PURPOSE. To evaluate the accuracy of a model made using the computer-aided design/computer-aided manufacture (CAD/CAM) milling method and 3D printing method and to confirm its applicability as a work model for dental prosthesis production. MATERIALS AND METHODS. First, a natural tooth model (ANA-4, Frasaco, Germany) was scanned using an oral scanner. The obtained scan data were then used as a CAD reference model (CRM), to produce a total of 10 models each, either using the milling method or the 3D printing method. The 20 models were then scanned using a desktop scanner and the CAD test model was formed. The accuracy of the two groups was compared using dedicated software to calculate the root mean square (RMS) value after superimposing CRM and CAD test model (CTM). RESULTS. The RMS value ($152{\pm}52{\mu}m$) of the model manufactured by the milling method was significantly higher than the RMS value ($52{\pm}9{\mu}m$) of the model produced by the 3D printing method. CONCLUSION. The accuracy of the 3D printing method is superior to that of the milling method, but at present, both methods are limited in their application as a work model for prosthesis manufacture.

• 소성∙가공
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• 제26권6호
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.

• 한국세라믹학회지
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• 제44권6호
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• pp.313-318
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• 2007

ITO (Indium-tin oxide) thin films have been prepared by a sol-gel spinning coating method and fired and annealed in the temperature range of $450-600^{\circ}C$. The XRD patterns of the films indicated the main peak of (222) plane and showed higher crystallinity with increasing an annealing temperature. The surface of the ITO thin films were treated with 0.1 N HCl 20% solution at room temperature. The effects of surface treatment on electrical properties and surface morphologies of the ITO films were investigated with the results of sheet resistance and FE-SEM, AFM images. The samples, subsequently treated with acidic solution for 40 sec showed the sheet resistance of $0.982\;k{\Omega}/square$. The surface treatment using acidic solution diminished the RMS (root mean square) value and the residual carbon content of the ITO films. It seemed that the acid-cleaning of the ITO thin films lead to the decrease of surface roughness and sheet resistance.

• KIEE International Transactions on Power Engineering
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• 제3A권3호
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• pp.130-138
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• 2003

This paper presents a discrete wavelet transform approach for determining the beginning and end times of voltage sags. Firstly, investigations in the use of some typical mother wavelets, namely Daubechies, Symlets, Coiflets and Biorthogonal are carried out and the most appropriate mother wavelet is selected. The proposed technique is based on utilizing the maximum value of Dl (at scale 1) coefficients in multiresolution analysis (MRA) based on the discrete wavelet transform. The results are compared with other methods for determining voltage sag duration, such as the Root Mean Square (RMS) voltage and Short Time Fourier Transform (STFT) methods. It is shown that the voltage sag detection technique based on the wavelet transform is a satisfactory and reliable method for detecting voltage sags in power quality disturbance analysis.

• 대한임베디드공학회논문지
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• 제12권2호
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• pp.79-88
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• 2017

One of the important applications of activity sensing in the home is energy monitoring. Many previous methodologies for detecting and recognizing household appliances have been proposed. This paper presents an approach that uses an energy metering circuit (EMC) to classify and identify the various electrical devices in home based on root-mean-square (RMS) consumed current value. EMC gathers the RMS current values created by appliance state transition (e.g., on to off) and apparatus operating process. In this paper, an identification algorithm is proposed to detect a change in current levels using the standard deviation of current signals and their average values. In addition, characteristic of the appliance is extracted concerning four feature parameters concerning the number of current levels, the minimum level, the maximum level, and signal-to-noise ratio (SNR) of them. Experiment results validate the reliable performance of the proposed identification method for 11 representative appliances.

• 대한기계학회논문집
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• 제17권9호
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• pp.2214-2222
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• 1993

With the use of the NC machine tool, the unmanned production system has been growing recently in the manufacturing field. This there are problems with monitoring adequate tool fracture during the cutting process efficiently. This study was planned and carried out to discover a way of monitoring tool condition in NO-LINE systems during the cutting process. The acquisition of data in cutting force and tool wear has been made in the section examined, to extract the RMS value of the cutting force as specific factors in the cutting process. The fluctuation of the RMS characteristics. From the results, it has been shown that the fluctuation of the RMS values for the cutting force has a close relation to flank wear.