• Korean Journal of Health Education and Promotion
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• v.30 no.1
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• pp.53-64
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• 2013

Objectives: In this study, a multilevel analysis model has been designed to investigate the effect of personal characteristics associated with smoking cessation on anti-smoking determinants with a goal of finding out the factors which have influence on smoking cessation among the entrants of smoking cessation clinic in a public health center. Methods: A total of 253,136 male smokers who received smoking cessation services for more than six(6) months in a smoking cessation clinic of public health center from July 16, 2007 to July 15, 2008 were examined. For technical analysis, SPSS Version 2.0 has been used. For multilevel analysis on smoking cessation determinants, in addition, HLM 7.0 has been adopted. Results: According to the unconditional model of multilevel analysis, the success rates of smoking cessation among the entrants of a smoking cessation clinic were 47.3%. In an unconditional slope model test to which regional variables were added, a negative effect was observed in average smoking amount, total smoking period, nicotine dependence and services while a positive effect was found in age, stress and type of social security in terms of the log of the odds of smoking cessation. In a conditional model test, a positive effect was observed in Non-Smoking Campaigns (NSC) and Frequency of Counseling (FC) in terms of the log of the odds of smoking cessation in regional variables. Conclusions: It is important to approach smokers individually and, at the same time, build healthy environment for a local community to increase smoking cessation rates among the entrants of smoking cessation clinic in a public health center.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.4
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• pp.37-45
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• 2003

Role-based Access Control(RBAC) model has advantage of easy management of access control with constraints such as permission inheritance and separation of duty in role hierarchy. However, previous RBAC studies could not properly reflect the real-world organization structure with its role hierarchy. User who is a member of senior role can perform all permissions because senior role inherits all permissions of junior roles in the role hierarchy. Therefore there is a possibility for senior role members to abuse permissions due to violation of the least privilege principle. In this paper, we present a new model of role hierarchy, which restricts the unconditional permission inheritance. In the proposed model, a role is divided into sub roles(unconditional inheritance. restricted inheritance, private role), keeping organization structure in corporate environment. With restricted inheritance, the proposed model prevents permission abuse by specifying the degree of inheritance in role hierarchy.

• Journal of Mechanical Science and Technology
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• v.15 no.1
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• pp.1-9
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• 2001

The recent spread of scaled telemanipulation into microsurgery and the nano-world increasingly requires the identification of the possible operation region as a main system specification. A teleoperation system is a complex cascaded system since the human operator, master, slave, and communication are involved bilaterally. Hence, a small time delay inside a master and slave system can be critical to the overall system stability even without communication time delay. In this paper we derive an upper bound of the scaling product of position and force by using Llewellyns unconditional stability. This bound can be used for checking the validity of the designed bilateral controller. Time delay from the sample and hold of computer control and its effects on stability of scaled teleoperation are modeled and simulated based on the transfer function of the teleoperation system. The feasible operation region in terms of position and force scaling decreases sharply as the sampling rate decreases and time delays inside the master and slave increase.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.530-545
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• 2023

As an alternative to conventional management options for a lot of concrete waste from decommissioning of nuclear power plants, a set of scenarios for controlled recycling of decommissioning concrete waste as engineered barriers of a radioactive waste repository was proposed, and a comprehensive safety assessment model and framework covering both pre-and post-closure phases was newly developed. The new methodology was applied to a reference vault-type repository, and the ratios of derived concentration limits to unconditional clearance levels of eighteen radionuclides for controlled recycling were provided for three sets of dose criteria (0.01, 1, and 20 mSv/y for the pre-closure and 0.01 mSv/y for the post-closure phases). It turns out that decommissioning concrete waste whose concentration is much higher than the unconditional clearance level can be recycled even when the dose criterion 0.01 mSv/y is applied. Moreover, a case study on ABWR bio-shield shows that the fraction of recyclable concrete waste increases significantly by increasing the dose criterion for the radiation worker in the pre-closure phase or the duration of storage prior to recycling. The results of this study are expected to contribute to demonstrating the feasibility of controlled recycling of a lot of decommissioning concrete waste within nuclear sectors.

• Journal of the Korean Society of Combustion
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• v.15 no.4
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• pp.15-21
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• 2010

The transported probability density function(PDF) model has been applied to simulate the turbulent nonpremixed piloted jet flame. To realistically account for the mixture fraction PDF informations on the turbulent non-premixed jet flame, the present Lagrangian PDF transport approach is based on the joint velocity-composition-turbulence frequency PDF formulation. The fluctuating velocity of stochastic fields is modeled by simplified Langevin model(SLM), turbulence frequency of stochastic fields is modeled by Jayesh-Pope model and effects of molecular diffusion are represented by the interaction by exchange with the mean (IEM) mixing model. To validate the present approach, the numerical results obtained by the joint velocity-composition-turbulence frequency PDF model are compared with experimental data in terms of the unconditional and conditional means of mixture fraction, temperature and species and PDFs.

• East Asian Economic Review
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• v.23 no.4
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• pp.409-427
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• 2019

This paper sets up a new Keynesian model with external habit to explore the role of each shock over business cycles in Korea. The estimated model via maximum likelihood shows that the productivity shock plays a pivotal role in explaining the output variations before and after the financial crisis since mid-1970s. It also shows that the model with external habit is more successful in explaining the business cycles in Korea after the Asian financial crisis than the model without habit. The monetary policy shock which dominates by accounting for more than 70 percent of the unconditional variance of the inflation rate before the financial crisis is less important in the inflation rate fluctuations after the financial crisis. This partly reflects the regime change of the monetary policy to the inflation targeting rule after the financial crisis.

• Communications for Statistical Applications and Methods
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• v.21 no.6
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• pp.501-512
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• 2014

Stylized facts on asset return are fat-tail, asymmetry, volatility clustering and structure changes. This paper simultaneously captures these characteristics by introducing a multi-regime models: Finite mixture distribution and regime switching GARCH model. Analyzing the daily KOSPI return from $4^{th}$ January 2000 to $30^{th}$ June 2014, we find that a two-component mixture of t distribution is a good candidate to describe the shape of the KOSPI return from unconditional and conditional perspectives. Empirical results suggest that the equality assumption on the shape parameter of t distribution yields better discrimination of heterogeneity component in return data. We report the strong regime-dependent characteristics in volatility dynamics with high persistence and asymmetry by employing a regime switching GJR-GARCH model with t innovation model. Compared to two sub-samples, Pre-Crisis (January 2003 ~ December 2007) and Post-Crisis (January 2010 ~ June 2014), we find that the degree of persistence in the Pre-Crisis is higher than in the Post-Crisis along with a strong asymmetry in the low-volatility (high-volatility) regime during the Pre-Crisis (Post-Crisis).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.78-85
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• 2002

This paper deals with the finite element model of the monitor for the simulation of directional free drop tests such as backward, sideward, edge and vertex drop. The model was made for an unconditional stable solution for the explicit integration algorithm. The general behaviors at the time of impact were found to well correlate with the actual situation in terms of acceleration, displacement, contact force and stress of monitor components even though the experiment of the associated drop is performed for the validity of the model.

• Journal of Korea Port Economic Association
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• v.31 no.1
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• pp.1-14
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• 2015

The standard GARCH model imposing symmetry on the conditional variance, tends to fail in capturing some important features of the data. This paper, hence, introduces the models capturing asymmetric effect. They are the EGARCH model and the GJR model. We provide the systematic comparison of volatility models focusing on the asymmetric effect of news on volatility. Specifically, three diagnostic tests are provided: the sign bias test, the negative size bias test, and the positive size bias test. This paper shows that there is significant evidence of GARCH-type process in the data, as shown by the test for the Ljung-Box Q statistic on the squared residual data. The estimated unconditional density function for squared residual is clearly skewed to the left and markedly leptokurtic when compared with the standard normal distribution. The observation of volatility clustering is also clearly reinforced by the plot of the squared value of residuals of export volume and values. The unconditional variance of both export volumes and export value indicates that large shocks of either sign tend to be followed by large shocks, and small shocks of either sign tend to follow small shocks. The estimated export volume news impact curve for the GARCH also suggests that $h_t$ is overestimated for large negative and positive shocks. The conditional variance equation of the GARCH model for export volumes contains two parameters ${\alpha}$ and ${\beta}$ that are insignificant, indicating that the GARCH model is a poor characterization of the conditional variance of export volumes. The conditional variance equation of the EGARCH model for export value, however, shows a positive sign of parameter ${\delta}$, which is contrary to our expectation, while the GJR model exhibits that parameters ${\alpha}$ and ${\beta}$ are insignificant, and ${\delta}$ is marginally significant. That indicates that the asymmetric volatility models are poor characterization of the conditional variance of export value. It is concluded that the asymmetric EGARCH and GJR model are appropriate in explaining the volatility of export volume, while the symmetric standard GARCH model is good for capturing the volatility.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5553-5571
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• 2016

In this paper, we introduce a new concept called generalized ring signcryption (GRSC), which can achieve ring signature and ring signcryption functions with only one key pair and one algorithm. It is very useful for a system which has a large number of users, or has limited storage space, or whose function requirements may be changed later. We give a formal definition and a security model of GRSC and propose a concrete scheme based on bilinear pairings. In the random oracle model, the scheme's confidentiality can be proved under the GBDH assumption, and its unforgeability can be proved under GDH' assumption, and what is more, this scheme also allows unconditional anonymity. Compared with other identity-based ring signcryption schemes that use bilinear pairings as well, our scheme is a highly efficient one.