• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.123-130
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• 1998

The probability of unseating failure of the bridge spans under earthquakes is investigated. Seismic excitations are simulated as nonstationary processes by combining a stationary process and an intensity function. For computational convenience, a simplified single-degree-of-freedom model is adopted, which retains the dynamic characteristics of the original brige motion in concern. The time history analysis for the developed single degree-of-freedom model are carried out to evaluate the response processes, and the probabilistic characteristics of response displacements are evaluated. The reliability analysis of the bridge against the unseating failure is performed with the statistical information of the maximum displacements of responses.

• Journal of Applied Reliability
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• v.18 no.1
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• pp.56-65
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• 2018

Purpose: The purpose of this study is to estimate shelf life of fuze MTSQ (Mechanical Time & Super Quick) KM577A1 from Ammunition Stockpile Reliability Program (ASRP) data. Methods: For many years, ammunition test data had been gathered from ASRP. In this study, lot selection criteria and reliability score of functioning time for fuze are proposed. Reliability score of functioning time and failure data are used to estimate shelf life. Results: The results of this study are as follows; The failure modes of fuze MTSQ KM577A1 are dud, inverse function and mechanical time functioning failure (not operating in intended time). Dud and inverse function are major failure modes. Fuze MTSQ KM577A1's shelf life ($B_5$) is estimated 18.2 years conservatively. Conclusion: Degradation of chemical components in fuze MTSQ KM577A1 is major factor for its reliability. And shelf life ($B_5$) of fuze MTSQ KM577A1 is estimated 18.2 years conservatively.

• Journal of Veterinary Clinics
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• v.23 no.4
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• pp.427-431
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• 2006

Pulse Doppler ultrasonographic evaluation was performed to investigate the resistive index (RI) of the Interlobar renal artery in 17 dogs (32 kidneys) which were diagnosed with an acute renal failure caused by ochratoxin-A and citrinin contaminated commercial diet. RI was investigated in 7 normal beagle dogs and recovered patients. The mean of RI was resulted as $0.69{\pm}0.04$ in normal dog, however, significantly (p<0.001) increased as $0.76{\pm}0.05$ in renal failure dog. But RI had no relationship with the results of blood chemistry, urine analysis, and excretory urographic image quality. From these results, even though the results of the renal function test were within a normal reference range, it was considered that RI index is more reliable to represent a damaged renal parenchyma, and may have the potential to be a useful clinical tool in monitoring of the renal function.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1159-1167
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• 2011

In this paper, we proposed and implemented an EPCglobal Reader Manegement (RM) based management protocol. Using RFID Reader's management function, we could diagnose an active RFID Reader concretely which was impossible with only using Reader protocols and check the problem quickly when the RFID Reader is in failure. When diagnosing RFID Readers using the proposed RM based management protocol, we can check on their failure in stages and specifically, and can estimate range of failure. This helps RFID Reader's fast recovery, reduce loss of failure and improve QoS. We could get reader information with almost same overhead compared with the management message in LLRP. And we could get more information about RFID Reader's operation status.

• Convergence Security Journal
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• v.10 no.1
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• pp.55-61
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• 2010

It is of great practical interest to deciding when to stop testing a software system in development phase and transfer it to the user. This decision problem called an optimal release policies. In this paper, because of the possibility of introducing new faults when correcting or modifying the software, we were researched release comparative policies which based on infinite failure NHPP model and types of interval failure times. The policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement can optimal software release times. In a numerical example, applied data which were patterns, if intensity function constant or increasing, decreasing, estimated software optimal release time.

• Tunnel and Underground Space
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• v.15 no.3 s.56
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• pp.228-235
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• 2005

Friction angle and cohesion of rock masses can be estimated from Hoek and Brown failure criterion and then plastic corrections can be applied using Mohr-Coulomb yield function. This study finds that this estimation procedure would not be appropriate for weak rock masses and for cases where low confining stress is expected to develop. A procedure is outlined in this paper for estimating plastic corrections directly from Hoek and Brown material model. Comparative study shows that direct procedure would simulate non-linear failure surface better than indirect procedure especially in the low confining stress regime.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.595-603
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• 2019

A modified model combining Kriging and Monte Carlo method (MC) is proposed for probabilistic estimation of tunnel face stability in this paper. In the model, a novel uniform design is adopted to train the Kriging, instead of the existing active learning function. It has advantage of avoiding addition of new training points iteratively, and greatly saves the computational time in model training. The kinematic approach of limit analysis is employed to define the deterministic computational model of face failure, in which the Hoek-Brown failure criterion is introduced to account for the nonlinear behaviors of rock mass. The trained Kriging is used as a surrogate model to perform MC with dramatic reduction of calls to actual limit state function. The parameters in Hoek-Brown failure criterion are considered as random variables in the analysis. The failure probability is estimated by direct MC to test the accuracy and efficiency of the proposed probabilistic model. The influences of uncertainty level, correlation relationship and distribution type of random variables are further discussed using the proposed approach. In summary, the probabilistic model is an accurate and economical alternative to perform probabilistic stability analysis of tunnel face excavated in spatially random Hoek- Brown media.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.655-667
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• 2018

To evaluate the stability of a rock slope with one pre-exiting vertical crack, this paper performs corresponding probabilistic stability analysis. The existence of cracks is generally ignored in traditional deterministic stability analysis. However, they are widely found in either cohesive soil or rock slopes. The influence of one pre-exiting vertical crack on a rock slope is considered in this study. The safety factor, which is usually adopted to quantity the stability of slopes, is derived through the deterministic computation based on the strength reduction technique. The generalized Hoek-Brown (HB) failure criterion is adopted to characterize the failure of rock masses. Considering high nonlinearity of the limit state function as using nonlinear HB criterion, the multivariate adaptive regression splines (MARS) is used to accurately approximate the implicit limit state function of a rock slope. Then the MARS is integrated with Monte Carlo simulation to implement reliability analysis, and the influences of distribution types, level of uncertainty, and constants on the probability density functions and failure probability are discussed. It is found that distribution types of random variables have little influence on reliability results. The reliability results are affected by a combination of the uncertainty level and the constants. Finally, a reliability-based design figure is provided to evaluate the safety factor of a slope required for a target failure probability.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.28-34
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• 2012

In this study, the reliability-based design optimization of the airfoil was performed. PARSEC function was used to consider the uncertainty of the aerodynamic shape for the reliability-based shape optimization of airfoils. Among various reliability analysis methods, the moment method was used to compute the probability of failure of the aerodynamic performance. The accuracy of the reliability analysis was compared with other methods and it was found that the moment method predicts the probability of failure accurately. Deterministic and reliability-based optimizations were performed for the shape of the airfoil and it was demonstrated that reliability-based optimum assures the aerodynamic performances under uncertainties of the shape of the airfoil.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.90-96
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• 2000

The technology of preventive maintenance and corrective maintenance is widely applied to ships in order to maintain the good voyageable condition. One of the most important fields of marine engineering is to seek the maximum availability and to solve the stochastic maintenance problem such that the cost for corrective maintenance is minimized. Accordingly, for the purpose of making the most suitable maintenance schedule which minimizes the expected cost function, this paper suggests the method to grasp the failure characteristics by the ship's maintenance data that are collected from the past. And, suggests the method to estimate the optimal maintenance interval by using the dynamic programming and the cumulative hazard rate function attained from the maintenance data.