• Journal of the Society of Disaster Information
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• v.4 no.1
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• pp.154-174
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• 2008

Korean public power isn't currently performing its duties of crime prevention or public security services as effectively as the people expect from it due to excessive work load, insufficient budget, and equipment or work force problems, although it should protect the people from increasing crimes. The mutual cooperation between the police and the private security firms can' t be enhanced unless both parties are involved. Above all, the private security companies should secure superior security personnel and provide them with systematic education and training to improve their qualities. The police should also make an effort. In order to foster the private security firms soundly, the police should improve the system if necessary, and establish, guide and monitor the department wholly responsible for the private security affair. Both parties also should deal with crimes systematically by exchanging information for crime prevention, having informal meetings and introducing a joint patrol system. In order to cope with crimes threatening the livelihood of the people in our society, the public and private securities' mutual cooperation plans should be formulated. For this purpose to be achieved, the private security firms and the police should understand each other and bilateral efforts should be made. If both parties understand each other and make an effort, the relationship between them will be improved greatly and developmental plans for preventing crimes can be made.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.194-202
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• 2019

Reliability analysis of the components frequently starts with the data that manufacturer provides. If enough failure data are collected from the field operations, the reliability should be recomputed and updated on the basis of the field failure data. However, when the failure time record for a component contains only a few observations, all statistical methodologies are limited. In this case, where the failure records for multiple number of identical components are available, a valid alternative is combining all the data from each component into one data set with enough sample size and utilizing the useful information in the censored data. The ROK Navy has been operating multiple Patrol Killer Guided missiles (PKGs) for several years. The Korea Multi-Function Control Console (KMFCC) is one of key components in PKG combat system. The maintenance record for the KMFCC contains less than ten failure observations and a censored datum. This paper proposes a Bayesian approach with a Dirichlet mixture model to estimate failure time density for KMFCC. Trends test for each component record indicated that null hypothesis, that failure occurrence is renewal process, is not rejected. Since the KMFCCs have been functioning under different operating environment, the failure time distribution may be a composition of a number of unknown distributions, i.e. a mixture distribution, rather than a single distribution. The Dirichlet mixture model was coded as probabilistic programming in Python using PyMC3. Then Markov Chain Monte Carlo (MCMC) sampling technique employed in PyMC3 probabilistically estimated the parameters' posterior distribution through the Dirichlet mixture model. The simulation results revealed that the mixture models provide superior fits to the combined data set over single models.