• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.320-328
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• 2011

This research proposes comprehensive models for analyzing common cause failures (CCF) due to cumulative shocks and to assess system reliability under the CCF. The proposed cumulative shock models are based on the binomial failure rate (BFR) model. Six kinds of models are proposed so as to explain diverse cumulative shock phenomena. The models are composed of the initial failure probability, shape parameter, and the total shock number. Some parameters of the proposed models can not be explicitly estimated, so we adopt the Expectation-maximization (EM) algorithm in order to obtain the maximum likelihood estimator (MLE) for the parameters. By estimating the parameters for the cumulative shock models, the system reliability with CCF can be assessed sequentially according to the number of cumulative shocks. The result can be utilizes in dynamic probabilistic safety assessment (PSA), aging studies, or risk management for nuclear power plants. Replacement or maintenance policies can also be developed based on the proposed model.

• International Journal of Reliability and Applications
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• v.4 no.2
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• pp.71-77
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• 2003

We propose, in this paper, the discrete version of NBU$_{Mg}$and show that the NBU$_{Mg}$ class is preserved under both the non-homo geneous poisson shock model and the general shock model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.1
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• pp.81-87
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• 2012

This paper establishes a modeling and simulation procedure for structural response and reliability of a cylindrical array sensor on submarines under the shock generated by underwater explosion. The structural reliability of SONAR is important because the submarine could get out of combat ability by the structural damage of the SONAR upon explosion. A cylindrical array sensor was first modeled using the finite element method. Modal analysis was then performed for the check of the reliability of the modeling. The shock resistance simulations were performed for the responses to the structural shock waves and for the responses to the directly applied underwater shock waves, according to BV-043 and MIL-STD-901D, respectively. The stresses of the structure were evaluated with von-Mises scheme. Vulnerable regions were exposed through mapping the maximum stress to the structural model. Maximum stress of the SONAR was compared with the yield stress of the material to examine the structural reliability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.10
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• pp.1440-1447
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• 2015

This paper describes a study for anti high-shock design of MEMS vibrating ring gyroscope. Structure models was made by MEMS technology processing. MEMS Vibrating Ring Gyroscope mechanical structure were not only anti-high shock simulated with the LS Dyna Ver 971 software but also with mathematical analysis and the finite element method in order to confirm the shock reliability. Shock test result of a MEMS vibrating gyroscope being developed to have gun-hardened survivability while maintaining tactical grade navigation performance for application to various guided projectiles.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.152-159
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• 2007

When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between $-40^{\circ}C\;and\;+125^{\circ}C$ for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and $45^{\circ}$ lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.4
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• pp.467-478
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• 2003

Automotive shock absorber may not be regarded as only one(simple) damping machine because it is composed of many components, and shows non-linear damping characteristics. No matter how advanced form of shock absorber is developed, the oil shock absorber can not be neglected. because their structures are based on the oil shock absorber. Therefore it is essential to accurately analyze the dynamic characteristics of oil shock absorber. It stands mainly roi damper valve tuning which nowadays is still exhaustively done by means of ride work. In this study, damping mechanism and dynamic characteristics for oil shock absorber of twin tube type are analyzed, based on the mathematical model considering internal flow and pressure. For the reliability of numerical prediction. the database is constructed within the limit of adequate reliability. Finally, the programmed system that gives out necessary specification by inputting damping specification and tolerance is to be constructed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

• The Journal of Korean Academic Society of Nursing Education
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• v.25 no.1
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• pp.17-26
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• 2019

Purpose: This study was conducted to verify the validity and reliability of the modified Transition Shock Scale for use among nursing students. Methods: From March 8-April 3, 2018, 207 nursing students participated in this study and were asked to complete self-reported questionnaires, including transition shock, clinical stress, and adapting to clinical practicums. The IBM SPSS Win 18.0 and AMOS 18.0 programs were used for data analysis. Results: A confirmatory factor analysis supported good convergent and discriminant validities ($x^2/df=1.58$, TLI=.92, CFI=.95, RMSEA=.053, AVE=.51-.68, CR=.75-.68). Correlations among transition shock, clinical stress (r=.34, p<.001), and adapting to clinical practicums (r=-.54, p<.001) were significant. Cronbach's alpha for the overall scale was .85, and for the six subfactors it ranged from .65 to .75. Conclusion: The findings suggest that the 17-item transition shock questionnaire is an appropriate instrument for measuring nursing students' transition shock with good validity and reliability.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.181-187
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• 2017

Purpose: The purpose of this study is to estimate the lifetime of commercial passenger vehicles shock absorber using degradation test and data. Method: The degradation factor of shock absorber was determined to be a damping force using FMEA. Degradation test was performed on damping force under real world usage condition and analysed the degradation data. Results: To estimate the lifetime of shock absorber, a degradation model was developed and a numerical example was provided. Conclusion: Evaluation of the lifetime of commercial and military vehicles shock absorber will be possible by using the proposed degradation analysis method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.625-631
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• 2009

In this thesis, lateral thermosonic bonding with ACFs was investigated as a process to make high reliability joints for FPD fabrication. Conditions for thermosonic and thermocompression bonding with ACFs were determined and used to make specimens in a driving test jig for testing of bond reliability by thermal shock. The results showed that thermosonic bonding temperature of $199\;^{\circ}C$ and bonding time of 1s produced bonds with good reliability. Additionally, thermosonic bonding temperature and time were reduced and thermal shock test results compared to this proposed curing condition. It is concluded that theromosonic bonding with ACFs can be effectively applied to reduce bonding temperature and time compared with that of thermocompression bonding.