• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.21-32
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• 2019

Inspired by the social behavior models of a bird flock or fish school, particle swarm optimization (PSO) is a popular metaheuristic optimization algorithm and has been widely used from solving a complex optimization problem to learning a artificial neural network. However, PSO is difficult to apply to many real-life optimization problems involving stochastic noise, since it is originated in a deterministic environment. To resolve this problem, this paper incorporates a resampling method called the uncertainty evaluation (UE) method into PSO. The UE method allows the particles to converge on the accurate optimal solution quickly in a noisy environment by selecting the particles' global best position correctly, one of the significant factors in the performance of PSO. The results of comparative experiments on several benchmark problems demonstrated the improved performance of the propose algorithm compared to the existing studies. In addition, the results of the case study emphasize the necessity of this work. The proposed algorithm is expected to be effectively applied to optimize complex systems through digital twins in the fourth industrial revolution.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.90-94
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• 2000

In this paper, we propose an efficient method of estimating a critical threshold which is used to reject unreliable patterns in a HMM based recognition system. The rejection methods based on the anti-models which are formulated as the statistical hypothesis determine whether or not to accept an input pattern by comparing the likelihood ratio of HMM and anti-models to a critical threshold. It is quite difficult to fix a threshold for the probability of a HMM because the range of such probabilities varies severely depending on the chosen class model. We estimate the critical threshold, which is very class-dependent, using the likelihood scores for the training database. In our experiments, we applied the proposed estimating method of the threshold to the HMM based 3D hand gesture recognition system. We found that this method can be used successfully for rejecting unreliable input gestures regardless of the types of anti-models.

• Korea Journal of Hospital Management
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• v.23 no.1
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• pp.65-77
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• 2018

The purpose of this study is to examine the structural causal relationships between service image, service satisfaction, affective commitment, and customer loyalty to customers who have experienced hospital medical services, and to identifies the mediating effect of relationship proneness in explaining the effects of service image, service satisfaction, and affectivel commitment on customer loyalty. For this study, 250 respondents were surveyed and data were analyzed using SPSS 21.0 and AMOS 20.0 statistical package. Statistical analysis tools, such as SPSS 21.0 and AMOS 20.0 were utilized for ensuring the validity and the reliability, whereas the SEM method was used for testing the research hypothesis. The results of study are as follows. Service image had significant influence on service satisfaction and emotional commitment. First, Service satisfaction was significant for emotional commitment and customer loyalty, and emotional commitment had a significant effect on customer loyalty. Therefore, the path relations between variables were all statistically significant. Second, there was differences the moderating effect of the relationship proneness in the effects of service satisfaction, service image and affective commitment on customer loyalty. In other words, the moderating effect of the relationship tendency was consistent with the research hypothesis and the adjustment effect was significant in the relationship between service satisfaction and customer loyalty. However, there was no control effect in relation to service image and customer loyalty and affective commitment and customer loyalty. Therefore, In order to secure long-term and stable profits by establishing a relationship with their customers, the medical service marketing strategies of hospitals should be promoted to enhance customer loyalty by raising the level of service satisfaction to high relationship proneness group and by raising the the level of affective commitment to low relationship proneness group.

• The Korean Journal of Applied Statistics
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• v.24 no.4
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• pp.695-708
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• 2011

Image fusion is the process of combining multiple images of the same scene into a single fused image with application to many fields, such as remote sensing, computer vision, robotics, medical imaging and military affairs. The widely used image fusion rules that use wavelet transform have been based on a simple comparison with the activity measures of local windows such as mean and standard deviation. In this case, information features from the original images are excluded in the fusion image and distorted fusion images are obtained for noisy images. In this paper, we propose the use of a nonparametric squared ranks test on the quality of variance for two samples in order to overcome the influence of the noise and guarantee the homogeneity of the fused image. We evaluate the method both quantitatively and qualitatively for image fusion as well as compare it to some existing fusion methods. Experimental results indicate that the proposed method is effective and provides satisfactory fusion results.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.1
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• pp.133-140
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• 2011

Recently, Web applications, such as Stock Image and Image Library, are developed to provide the integrated management for user's images. Image hash techniques are used for the image registration, management and retrieval as the identifier and many researches have been performed to raise the hash performance. This paper proposes GLOCAL image hashing method utilizing the hierarchical histogram which based on histogram bin population method. So far, many researches have proven that image hashing techniques based on histogram are robust image processing and geometrical attack. We modified existing image hashing method developed by our research team. The main idea is that it makes more fluent hash string if we have histogram bin of specific length as shown in the body of paper. Finally, we can raise the magnitude of hash string within same context or feature and strengthen the robustness of hash.

• Journal of Korea Trade
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• v.23 no.4
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• pp.80-102
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• 2019

Purpose - This paper aims to articulate relationship about factors influencing FTA utilization by dividing them into company's external and internal factors and performing investigation on the relationship between FTA utilization and export performance. Design/methodology - This study verified factors influencing FTA utilization by dividing them into company's external and internal factors and performing investigation on the relationship between FTA utilization and export performance. Empirical analysis was performed by setting internal and external factors required for FTA utilization as variables. To achieve this, research model was established based on previous study, hypothesis was deduced, and statistical program were used to test the hypothesis. This study performed empirical analysis using statistical program of SPSS 18.0 and AMOS 18.0 for the research model. Findings - Empirical analysis was performed regarding the effect of the FTA utilization on export performance and previous study defined export performance as the company's increased economy benefits through export and increase in new transactions. Analysis was also performed for factors affecting the FTA utilization by the company and through management and response of external factors and internal factors it was confirmed that the FTA utilization by the company led to increase in the company's export performance as a result. This study proposes a method to achieve export performance based on this. Originality/value - Companies seeking to utilize the FTA sign the Contract for the International Sale of goods and there are many conditions to meet in order to receive trade preferences during the transaction process. Existing trade order and order in the FTA have to be followed. Country of origin can be seen as key in the FTA. The Rule of Origin becomes the most important evaluation standard in applying preferential tariff in the FTA. Such regulations can be seen as external factors which cannot be controlled by the company. Internal factors are capabilities owned before that can be controlled by the company. The study sought to test the variables regarding factors centered on such capability. This study verified factors influencing FTA utilization by dividing them into company's external and internal factors and performing investigation on the relationship between FTA utilization and export performance.

• The Korean Journal of Applied Statistics
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• v.32 no.1
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• pp.1-13
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• 2019

An adaptive seamless Phase II/III clinical trial design enables a reduction in the sample size (in comparison to a conventional design) that also shortens the clinical development time. It is also very effective in clinical trials since it can have higher statistical power than Phase III alone. In this study, we use extensive simulation studies to compare several multiple hypothesis testing methods that can help select the best doses in a Phase II study along with several methods to combine p-values of the Phase II and Phase III study.

• Tunnel and Underground Space
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• v.12 no.1
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• pp.19-30
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• 2002

Rock joint orientation is one of important geometric attributes that have an influence on the stability of rock structures such as rock slopes and tunnels. Especially, statistical models of the geometric attributes of rock joints can provide a probabilistic approach of rock engineering problems. The result from probabilistic modeling relies on the choice of statistical model. Therefore, it is critical to define a representative statistical model for joint orientation data as well as joint size and intensity and build up a series of modeling procedure including analytical validation. In this paper, we have examined a theoretical methodology for the statistical estimate and hypothesis analysis based upon Fisher distribution and bivariate normal distribution. In addition, we have proposed the algorithms of random number generator which is applied to the simulation of rock joint networks and risk analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.643-650
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• 2014

Gear transmission system is widely applied in engineering. As the problem of contact fatigue, wear, lubrication failure etc, the condition of gear teeth contacts will be worse. The vibration and sound signals in the gear system will be affected by the some failures like scuffing, abrasive wear and spalling due to the deterioration of gear teeth surface. By studying the estimation of specific film thickness, measurement of reduction in tooth thickness, visual examination of wear mechanisms on the gear teeth and their effects on the statistical parameters of vibration and sound signals, the research obtained the satisfactory results on accessing the surface fatigue wear in a spur gear system. The paper utilizes the relationship between statistical parameters obtained from sound signals and Stribeck curve to confirm the hypothesis of dependency of surface fatigue wear, specific film thickness.

• Communications for Statistical Applications and Methods
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• v.24 no.5
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• pp.519-531
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• 2017

We consider goodness-of-fit test statistics for Weibull distributions when data are randomly censored and the parameters are unknown. Koziol and Green (Biometrika, 63, 465-474, 1976) proposed the $Cram\acute{e}r$-von Mises statistic's randomly censored version for a simple hypothesis based on the Kaplan-Meier product limit of the distribution function. We apply their idea to the other statistics based on the empirical distribution function such as the Kolmogorov-Smirnov and Liao and Shimokawa (Journal of Statistical Computation and Simulation, 64, 23-48, 1999) statistics. The latter is a hybrid of the Kolmogorov-Smirnov, $Cram\acute{e}r$-von Mises, and Anderson-Darling statistics. These statistics as well as the Koziol-Green statistic are considered as test statistics for randomly censored Weibull distributions with estimated parameters. The null distributions depend on the estimation method since the test statistics are not distribution free when the parameters are estimated. Maximum likelihood estimation and the graphical plotting method with the least squares are considered for parameter estimation. A simulation study enables the Liao-Shimokawa statistic to show a relatively high power in many alternatives; however, the null distribution heavily depends on the parameter estimation. Meanwhile, the Koziol-Green statistic provides moderate power and the null distribution does not significantly change upon the parameter estimation.