• Title, Summary, Keyword: Acceleration factor

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Estimation of Failure Rate and Acceleration Factor in Accelerated Life Testing under Type-I Censoring (정시중단 가속수명시험에서 고장률과 가속계수의 추정)

  • Kong, Myung Bock;Park, Il Gwang
    • Journal of Korean Institute of Industrial Engineers
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    • v.29 no.2
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    • pp.145-149
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    • 2003
  • We consider the estimation of failure rate and acceleration factor under type-I censoring without using acceleration model when testing is conducted in only one highly accelerated condition. Failure times of an item are assumed to be exponentially distributed. It is also assumed that the uncertainty about the acceleration factor, the failure time contraction ratio between accelerated condition and use condition, can be modeled by the uniform or gamma prior distribution of appropriate parameters. We respectively use Bayes and maximum likelihood approaches to estimate acceleration factor and failure rate in the use condition. An example is given to show how the method can be applied.

Investigation into the Worst Stress Condition for an Accelerated Life Test of a Compressor in Refrigerators - Acceleration Factor and the Reducible Test Time under Low Temperature - (냉장고용 압축기의 가속수명시험을 위한 가혹조건 탐색 - 저온 가혹조건에서의 가속계수와 단축 시험기간 -)

  • Jung, Y.M.;Joo, W.J.;Jeong, S.K.
    • Journal of Power System Engineering
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    • v.16 no.2
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    • pp.43-48
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    • 2012
  • Generally accelerated life test is well known as one method to reduce reliability qualification test period. This test is conducted under the higher stress condition than normal condition. So it can save the test time by calculating the acceleration factor from the relationship between the worst stress condition and normal condition. This paper investigates the worst stress condition for the accelerated life test to increase the acceleration factor. Especially, we focused on the method to obtain effective acceleration factors under the worst stress condition. Moreover, we considered how to decide the worst stress condition by looking for the operating limit of this system. The acceleration factor can be estimated from the ratio of the kinematic viscosity in the normal condition and the worst stress condition, the lowest temperature, by using Arrhenius relationship. Through some experiments for a refrigerator's compressor, we were able to confirm how to increase acceleration factors and how to reduce the reliability qualification test period with minimum samples.

A Study on the Convergency Improvement of Power Flow Calculation by Applying Acceleration Factor Evaluation (가속정수산정에 의한 전력조류계산의 수산특성개선에 관한 연구)

  • 김준현;박건수
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.36 no.6
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    • pp.390-395
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    • 1987
  • There is a variety not only of research topics but also of research techniques in electric power problems. It is well known that a significant increase in the rate of convergence can be obtained for the Gauss-Seidel method using the bus admittance matrix by applying acceleration factors determined empirically. The acceleration factor is calculated theoretically by using the bus voltage sensitivity (buses voltage interact each other) in this paper. It is observed that the proposed method using calculated acceleration factor gives better results than those of the method using calculated acceleration factor gives better results than those of the method using empirical one.

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Retrieving the Time History of Displacement from Measured Acceleration Signal

  • Han, Sangbo
    • Journal of Mechanical Science and Technology
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    • v.17 no.2
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    • pp.197-206
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    • 2003
  • It is intended to retrieve the time history of displacement from measured acceleration signal. In this study, the word retrieving means reconstructing the time history of original displacement signal from already measured acceleration signal not just extracting various information using relevant signal processing techniques. Unlike extracting required information from the signal, there are not many options to apply to retrieve the time history of displacement signal, once the acceleration signal is measured and recorded with given sampling rate. There are two methods, in general, to convert measured acceleration signal into displacement signal. One is directly integrating the acceleration signal in time domain. The other is dividing the Fourier transformed acceleration signal by the scale factor of - $\omega$$^2$and taking the inverse Fourier transform of it. It turned out both the methods produced a significant amount of errors depending on the sampling resolution in time and frequency domain when digitizing the acceleration signals. A simple and effective way to convert the time history of acceleration signal into the time history of displacement signal without significant errors is studied here with the analysis on the errors involved in the conversion process.

Recovery of spectral absolute acceleration and spectral relative velocity from their pseudo-spectral counterparts

  • Papagiannopoulos, George A.;Hatzigeorgiou, George D.;Beskos, Dimitri E.
    • Earthquakes and Structures
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    • v.4 no.5
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    • pp.489-508
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    • 2013
  • Design spectra for damping ratios higher than 5% have several important applications in the design of earthquake-resistant structures. These highly damped spectra are usually derived from a 5%-damped reference pseudo-acceleration spectrum by using a damping modification factor. In cases of high damping, the absolute acceleration and the relative velocity spectra instead of the pseudo-acceleration and the pseudo-velocity spectra should be used. This paper elaborates on the recovery of spectral absolute acceleration and spectral relative velocity from their pseudo-spectral counterparts. This is accomplished with the aid of correction factors obtained through extensive parametric studies, which come out to be functions of period and damping ratio.

Method of Predicting Thermal Fatigue Life of LED Traffic Signal Module (LED식 신호등의 열피로 수명의 예측법)

  • Park, Tae-Keun;Kim, Jin-Sun;Jung, Hee-Suk;Kim, Jung-Soo;Kim, Do-Hyong;Lee, Young-Joo
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.20-24
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    • 2006
  • In this paper we investigated the method of examining the accelerated life test on LED traffic signal module by the temperature. The longevity presumption of the LED type signal light by a general heat cycle test used and executed cycle when it was done to longevity by the heat cycle test number and the acceleration factor of a real system requirements of this heat cycle test. Therefore, it reports on the introduction of the acceleration type from which the LED traffic signal module is done here to clarify the above-mentioned acceleration factor with the object and the acceleration factor is requested the test atmosphere actually in the system requirements.

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Development of Accelerated Life Test Method for Constant Electrical Potential Electrolysis Gas Sensor (정전위 전해식 가스센서의 가속수명시험법 개발)

  • Yang, Il Young;Kang, Jun Gu;Yu, Sang Woo;Oh, Geun Tae;Na, Yoon Gyoon
    • Journal of Applied Reliability
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    • v.16 no.3
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    • pp.180-191
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    • 2016
  • Purpose: The purpose of this study was to develop the accelerated life test method for Constant Electrical Potential Electrolysis gas sensor (CEPE gas sensor). Methods: The parts and modules of CEPE gas sensor were analyzed by using Reliability Block Diagram (RBD). Failure Mode and Effect Analysis (FMEA) and Quality Function Deployment (QFD) methods were performed for each part to determine the most affecting stress factor in its life cycle. The long term testing was conducted at three different dry heat levels and the acceleration factor was developed by using Arrhenius relationship. Conclusion: The acceleration factor for CEPE gas sensor was developed by using FMEA, QFD, and statistical analysis for its failure data. Also qualification tests were designed to meet the target life.

Evaluation of the Acceleration-factor and Analysis of the Vibration Fatigue for the Connection-pipe to the Compressor under the Random Vibration (랜덤 진동 조건에서의 압축기 연결 파이프에 대한 가속 수명 팩터 선정 및 진동 피로 해석)

  • Han, Hyung-Suk;Jung, Woo-Seoung;Yoon, Kyung-Jong;Mo, Jin-Yong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.3
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    • pp.323-334
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    • 2008
  • According to the delivery condition, the breakage of a product occurs when it is delivered to the customers. Therefore product's makers evaluate the durability under the delivery process by accelerated life testing. In order to conduct this accelerated life testing accurately, it is very important to identify the acceleration-factor exactly between on-road and accelerated life test condition. In this paper, the acceleration-factor is identified by applying linear damage summation law, rain-flow cycle counting and Dirlik theory under the conditions of the random vibration. And approximated FEM model of the connecting-pipe to the compressor is developed for fatigue analysis. This model is finally verified by comparing the experiment results to the numerical analysis results.

Design Shear Force Reduction Factor of Upper Structure in Seismic Base-isolated System Considering Response Acceleration Decrement Effect (면진구조의 응답가속도 감소효과를 고려한 상부구조의 설계전단력 저감계수)

  • Chen, Hao;Oh, Sang-Hoon
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.7
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    • pp.165-170
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    • 2019
  • The structural damage caused by earthquake to the upper structure of seismic base-isolated system can be suppressed effectively because it is designed to concentrate the input energy on the seismic isolation floor. Further, the response acceleration of seismic base-isolated system can be greatly reduced compared to the seismic structure because of the long period, which means that the design shear force of the seismic base-isolated system can be reduced appropriately. However, when the design shear force is determined to be reduced, the design stiffness will decrease, and the response acceleration will increase oppositely. Therefore, for finding the extent to which the design shear force of the upper structure can be reduced, this paper considered the seismic base-isolated structure as the analytical model and proposed the design shear force reduction factor of the base-isolated structure through the dynamic response analysis, while considering the decrement effect of response acceleration. The research result shows that the response acceleration of the isolated the upper structure can be reduced by 50%~70% of the seismic structure under the same design conditions, and the design shear force can be reduced by up to 40%. By increasing the design stiffness over to 1.8 times of the original design value, the design shear force can be reduced to the same extent as the response acceleration can be reduced compared to the seismic structure.

Analysis of Braking Response Time for Driving Take Based on Tri-axial Accelerometer

  • Shin, Hwa-Kyung;Lee, Ho-Cheol
    • The Journal of Korean Physical Therapy
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    • v.22 no.6
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    • pp.59-63
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    • 2010
  • Purpose: Driving a car is an essential component of daily life. For safe driving, each driver must perceive sensory information and respond rapidly and accurately. Brake response time (BRT) is a particularly important factor in the total stopping distance of a vehicle, and therefore is an important factor in traffic accident prevention research. The purpose of the current study was (1) to compare accelerometer. BRTs analyzed by three different methods and (2) to investigate possible correlations between accelerometer-BRTs and foot switch-BRTs, which are measured method using a foot switch. Methods: Eighteen healthy subjects participated in this study. BRT was measured with either a tri-axial accelerometer or a footswitch. BRT with a tri-axial accelerometer was analyzed using three methods: maximum acceleration time, geometrical center, and center of maximum and minimum acceleration values. Results: Both foot switch-BRTs and accelerometer-BRTs were delayed. ANOVA for accelerometer BRTs yielded significant main effects for axis and analysis, while the interaction effect between axis and analysis was not significant. Calculating the Pearson correlation between accelerometer-BRT and foot switch-BRT, we found that maximum acceleration time and center of maximum and minimum acceleration values were significantly correlated with foot switch-BRT (p<0.05). The X axis of the geometrical center was significantly correlated with foot switch-BRTs (p<0.05), but Y and Z axes were not (p>0.05). Conclusion: These findings suggest that the maximum acceleration time and the center of maximum and minimum acceleration value are significantly correlated with foot switch-BRTs.