• Journal of Korean Society of Transportation
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• v.11 no.1
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• pp.87-103
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• 1993

The subject this paper is the signal control strategy under oversaturated conditions. The nature of traffic control for oversaturation is essentially different from the standard control modes. While under non-saturated situation traffic control is needed for the sake of safety and efficiency, the throughput is essential under oversaturated conditions. Therefore berth objective and strategies differ. For an oversaturated stream the cycle time and the signal offset are thought to be of rather secondary importance. For this case the green split may well be the most important control variable to serve the excessive demand. Up to now, however, most efforts have concentrated on the strategy with the concept which lies just on the extension of Webster's. "Green-split Coordination Strategy for Over-Saturated Networks", presents newly contrived three types of strategies named Forward-coordination, Backward-coordination and Network-coordination respectively and describes the algorithms with the evaluations. The forward coordination strategy treats the forward wave of flow between two signals. The aim is to prevent the outbreak of queue due to the accumulation of temporary excess of demand in near-saturation or saturation flow. The backward coordination strategy treats the backward rave of flow between two signals. The goal is to prevent the waste of green time caused by the exit block at the upstream signal. for this purpose a feedback regulation is provided of the upstream green-split so that the inflow-outflow balance is kept zero. The resultant surplus of green time is alloted to other signal stages. Also here the examination is made of the appropriate value of the feedback control parameter. The network coordination strategy is operated to maximize the network throughput in a specific direction applying a bang-bang control at the bottleneck intersection. This is a type of intervenient control for policy reasons. For this strategy the green-split coordinations, particuarly the backward coordination, are essential as the tactical elements. In order to evaluate the preposed strategies those are compared with the latest existing strategy called saturation-degree-ratio control by the simulation experiments in an assumed 4$\times$4 grid network. The results are satisfactory showing a 10-15% reduction in delays and a 15% increase in network capacity.

• Journal of Environmental Health Sciences
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• v.41 no.2
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• pp.90-101
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• 2015

Objective: This study was conducted to develop a chemical oxygen demand (COD) regression model using water quality monitoring data (January, 2014) obtained from the Han River auto-monitoring stations. Methods: Surface water quality data at 198 sampling stations along the six major areas were assembled and analyzed to determine the spatial distribution and clustering of monitoring stations based on 18 WQPs and regression modeling using selected parameters. Statistical techniques, including combined genetic algorithm-multiple linear regression (GA-MLR), cluster analysis (CA) and principal component analysis (PCA) were used to build a COD model using water quality data. Results: A best GA-MLR model facilitated computing the WQPs for a 5-descriptor COD model with satisfactory statistical results ($r^2=92.64$,$Q{^2}_{LOO}=91.45$,$Q{^2}_{Ext}=88.17$). This approach includes variable selection of the WQPs in order to find the most important factors affecting water quality. Additionally, ordination techniques like PCA and CA were used to classify monitoring stations. The biplot based on the first two principal components (PCs) of the PCA model identified three distinct groups of stations, but also differs with respect to the correlation with WQPs, which enables better interpretation of the water quality characteristics at particular stations as of January 2014. Conclusion: This data analysis procedure appears to provide an efficient means of modelling water quality by interpreting and defining its most essential variables, such as TOC and BOD. The water parameters selected in a COD model as most important in contributing to environmental health and water pollution can be utilized for the application of water quality management strategies. At present, the river is under threat of anthropogenic disturbances during festival periods, especially at upstream areas.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.607-613
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• 2009

In this paper, we made a simple paper feeding system which is one of MTS (media transport system) and controllers. The plant has a flexible paper and two driving rollers and two driven rollers. The control system has two conventional PID controllers. Skew angle and feeding speed of MTS deteriorate the quality of feeding system. In order to control a feeding speed and skew of feeding paper, we control rotational velocity of two driving rollers. Therefore, this controller has two inputs and two outputs as MIMO (multi-input and multi-output) system. The control inputs were the feeding speed and the skew displacement of the paper. The control outputs were the rotational velocity to each driving roller. To find appropriate PID gains of two controllers, we proposed an optimization technique. We assume the system variables and performance of a whole system as follows. PID gains of two controllers for skew and feeding speed are system variables. System performance is both skew and feeding speed. We simulates to making mathematical correlation using global Kriging interpolation. To find appropriate value of system variables, optimization method is simulation in sequence as following method. First, the optimization solver simulates with DOE (design of experiment) tables to find correlation equation of both system variable and performances. Then, the solver guesses the appropriate values and simulates if the system variables are appropriate or not. If the result of validation doesn't satisfy the convergence and iteration tolerance, the solver makes a new Kriging models and iterates this sequence until satisfy the tolerances.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.683-690
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• 2012

In this work, the semi-active control of a large-sized bus suspension system with an MR damper was studied. An MR damper model that can aptly describe the hysteretic characteristics of an MR damper was adopted. Parameter values of the MR damper model were suitably modified by considering the maximum damping force of a passive damper used in the suspension system of a real large-sized bus. In addition, a fuzzy logic controller was developed for semi-active control of a suspension system with an MR damper. The vertical acceleration at the attachment point of the MR damper and the relative velocity between sprung and unsprung masses were used as input variables, while voltage was used as the output variable. Straight-ahead driving simulations were performed on a road with a random road profile and on a flat road with a bump. In straight-ahead driving simulations, the vertical acceleration and pitch angle were measured to compare the riding performance of a suspension system with a passive damper with that of a suspension with an MR damper. In addition, a single lane change simulation was performed. In the simulation, the lateral acceleration and roll angle were measured in order to compare the handling performance of a suspension system using a passive damper with that of a suspension system using an MR damper.

• Neonatal Medicine
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• v.25 no.3
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• pp.102-108
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• 2018

Purpose: Congenital diaphragmatic hernia (CDH) is rare but potentially fatal. The overall outcome is highly variable. This study aimed to identify a simple and dynamic parameter that helps predict the mortality of CDH patients in real time, without invasive tests. Methods: We conducted a retrospective chart review of 59 CDH cases. Maternal and fetal information included the gestational age at diagnosis, site of defect, presence of liver herniation, and lung-to-head ratio (LHR) at 20 to 29 weeks of gestational age. Information regarding postnatal treatment, including the number of days until surgery, the need for inhaled nitric oxide (iNO), the need for extracorporeal membrane oxygenation (ECMO), and survival, was collected. The highest respiratory severity score (RSS) within 24 hours after birth was also calculated. Results: Statistical analysis showed that a younger gestational age at the initial diagnosis (P<0.001), a lower LHR (P=0.001), and the presence of liver herniation (P=0.003) were prenatal risk factors for CDH mortality. The RSS and use of iNO and ECMO were significant factors affecting survival. In the multivariate analysis, the only remaining significant risk factor was the highest preoperative RSS within 24 hours after birth (P=0.002). The area under the receiver operating characteristic curve was 0.9375, with a sensitivity of 91.67% and specificity of 83.87% at the RSS cut-off value of 5.2. The positive and negative predictive values were 82.14% and 92.86%, respectively. Conclusion: Using the RSS as a prognostic predictor with simple calculations will help clinicians plan CDH management.

• Fire Science and Engineering
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• v.29 no.5
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• pp.29-33
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• 2015

In this study, the relations of flow rate, discharging distance and droplet size are measured in accordance with the nozzle shape. The dual type nozzles of LPN142 and LPN148, which have identical core diameter (6.0 mm) and the different radial injection angles (${\theta}_2=142^{\circ}$ and $148^{\circ}$), are manufactured. The distribution diameters with discharging distance are quantified by UL2167 test standard. The relations between discharging angle and droplet sizes, which are measured by the method of Helium-Neon laser equipment, are obtained by the empirical correlation as working pressure increase. Moreover, the extinction coefficient, which is major parameter of the radiative transport equation (RTE) is analyzed with variable droplet sizes. Thus, it is possible to opt the nozzle's shape by analyzing the relations of working pressure, spray distance, droplet size and fire characteristics at minimum allowable flow rate.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.5
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• pp.1356-1361
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• 2004

Moxa-combustion therapy make use of heat stimulus and chemicals result form when cauterize the skin with moxa cones to medical cares. However, recently moxibustion have been utilized less than acupuncture for treatment of disease in a practicing oriental physicians. To determine variable parameters (the numbers, the times, the quantities, the locations) affected moxibustion's effects, the gastrin serum level in rats were observed. In experiment, male Spraque-Dawley rats (body wt. 140-160g) were selected. Anything is performed to normal group. Control group were only anesthetized with inhalation in normal group. Experimental group were anesthetized and cauterized with moxa at BL21 by way of direct moxibustion. The size of moxa cone is 1.6±0.2㎎. The moxibustion as 5 times a day for five days has shown most significant effects and the moxibustion as a aquantity of 1, 5, 10 times moxa united one respectly, inverse to quantity in effects. The moxibustion for five days has also shown an most significant effects. The moxibustion at unilateral acupoints BL21 have less effects than bilateral one and these effects had no difference between control group after vagotomy. This results indicate that moxibustion's effects are not direct proportion to moxa cone size and frequency but imply that there is adequate value of moxibustion.

• The Korean Journal of Applied Statistics
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• v.14 no.1
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• pp.39-57
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• 2001

Categorical data has sometimes misclassification errors. If this data will be analyzed, then estimated cell probabilities could be biased and the standard Pearson X2 tests may have inflated true type I error rates. On the other hand, if we regard wellclassified data with misclassified one, then we might spend lots of cost and time on adjustment of misclassification. It is a necessary and important step to ask whether categorical data is misclassified before analyzing data. In this paper, when data is misclassified at one of two variables for two-dimensional contingency table and marginal sums of a well-classified variable are fixed. We explore to partition marginal sums into each cells via the concepts of Bound and Collapse of Sebastiani and Ramoni (1997). The double sampling scheme (Tenenbein 1970) is used to obtain informations of misclassification. We propose test statistics in order to solve misclassification problems and examine behaviors of the statistics by simulation studies.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.505-519
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• 2006

We consider zero-inflated count data, which is discrete count data but has too many zeroes compared to the Poisson distribution. Zero-inflated data can be found in various areas. Despite its increasing importance in practice, appropriate statistical inference on zero-inflated data is limited. Classical inference based on a large number theory does not fit unless the sample size is very large. And regular Poisson model shows lack of St due to many zeroes. To handle the difficulties, a mixture of distributions are considered for the zero-inflated data. Specifically, a mixture of a point mass at zero and a Poisson distribution is employed for the data. In addition, when there exist meaningful covariates selected to the response variable, loglinear link is used between the mean of the response and the covariates in the Poisson distribution part. We propose a Bayesian inference for the zero-inflated Poisson regression model by using a Markov Chain Monte Carlo method. We applied the proposed method to a Korean oral hygienic data and compared the inference results with other models. We found that the proposed method is superior in that it gives small parameter estimation error and more accurate predictions.

• Journal of Korean Society of Transportation
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• v.26 no.1
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• pp.113-126
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• 2008

This research aims to explore the effects of multicollinearity on the reliability and goodness of fit of logit model. To investigate the effects of multicollinearity on the multinominal logit model, numerical experiments are performed. The exploratory variables(attributes of utility functions) which have a certain degree of correlations from (rho=) 0.0 to (rho=) 0.9 are generated and rho-squares and t-statistics which are the indices of goodness of fit and reliability of logit model are traced. From the well designed numerical experiments, following findings are validated : 1) When a new exploratory variable is added, some of rho-squares increase while the others decrease. 2) The higher relations between generic variables lead a logit model worse with respect to goodness of fit. 3) Multicollinearity has a tendency to produce over-evaluated parameters. 4) The reliability of the estimated parameter has a tendency to decrease when the correlations between attributes are high. These results suggest that we have to examine the existence of multicollinearity and perform the proper treatments to diminish multicollinearity when we develop logit model.