• The Journal of Sustainable Design and Educational Environment Research
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• v.9 no.2
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• pp.1-8
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• 2010

This study is to present an engineering solution for the repair frequency and repair rates of a building. The existing data for the repair frequency and repair rates are used to draw the probability distribution for the generalized repair frequency and repair rate in a building. The suggested methodology can be widely used for most buildings to estimate the legal repair frequency and repair rates. Also, the methodology can be applied to resolve the risks on the maintenance costs in LC (Life Cycle) plans or LCC (Life Cycle Cost) analysis. As the future studies, there are the multiple regression analysis including the parameters on incurred costs and the decision methods on efficient repair and replacement.

• Journal of Communications and Networks
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• v.12 no.1
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• pp.30-42
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• 2010

In this work we consider the problem of downlink resource allocation for proportional fairness of long term received rates of data users and quality of service for real time sessions in an OFDMA-based wireless system. The base station allocates available power and subchannels to individual users based on long term average received rates, quality of service (QoS) based rate constraints and channel conditions. We formulate and solve a joint bandwidth and power optimization problem, solving which provides a performance improvement with respect to existing resource allocation algorithms. We propose schemes for flat as well as frequency selective fading cases. Numerical evaluation results show that the proposed method provides better QoS to voice and video sessions while providing more and fair rates to data users in comparison with existing schemes.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.12
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• pp.985-992
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• 2001

This paper proposes a self-organizing fuzzy modeling(SOFUM)which an create a new hyperplane shaped cluster and adjust parameters of the fuzzy model in repetition. The suggested algorithm SOFUM is composed of four steps: coarse tuning. fine tuning cluster creation and optimization of learning rates. In the coarse tuning fuzzy C-regression model(FCRM) clustering and weighted recursive least squared (WRLS) algorithm are used and in the fine tuning gradient descent algorithm is used to adjust parameters of the fuzzy model precisely. In the cluster creation, a new hyperplane shaped cluster is created by applying multiple regression to input/output data with relatively large fuzzy entropy based on parameter tunings of fuzzy model. And learning rates are optimized by utilizing meiosis-genetic algorithm in the optimization of learning rates To check the effectiveness of the suggested algorithm two examples are examined and the performance of the identified fuzzy model is demonstrated via computer simulation.

• Journal of Communications and Networks
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• v.4 no.3
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• pp.189-198
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• 2002

Precoder has been shown to be able to provide source diversity and design flexibility. In this paper we employ precoding techniques for block transmission based on a multirate filterbank structure. To accommodate multiuser communication with variable data rates, different precoders with corresponding coefficients and up/down sampling rates are used. However, due to unknown multipath distortion, different interferences may exist in the received data, such as multiuser interference, intersymbol interference and interblock interference. To estimate channel parameters for a desired user, we employ all structured signature waveforms associated with different symbols of that user and apply subspace techniques. Therefore better performance of channel estimator can be achieved than the conventional subspace method based only on the signature of the current symbol. The delay for that user can also be jointly estimated. Channel identifiability conditions and asymptotic channel estimation error are investigated in detail. Numerical examples are provided to justify the proposed method. gest either multicode (MC) or multiple processing gain (MPG) mechanism [2], while requiring data rates to be integral multiples of some basic low-rate. In order to support variable rate transmission however, a comprehensive scheme needs to be investigated.

• ETRI Journal
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• v.39 no.2
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• pp.234-244
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• 2017

Research interest in three-dimensional multiple-input multiple-output (3D-MIMO) beamforming has rapidly increased on account of its potential to support high data rates through an array of strategies, including sector or user-specific elevation beamforming and cell-splitting. To evaluate the full performance benefits of 3D and full-dimensional (FD) MIMO beamforming, the 3D character of the real MIMO channel must be modeled with consideration of both the azimuth and elevation domain. Most existing works on the 2D spatial channel model (2D-SCM) assume a wide range for the distribution of elevation angles of departure (eAoDs), which is not practical according to field measurements. In this paper, an optimal FD-MIMO planar array configuration is presented for different practical channel conditions by restricting the eAoDs to a finite range. Using a dynamic network level simulator that employs a complete 3D SCM, we analyze the relationship between the angular spread and sum throughput. In addition, we present an analysis on the optimal antenna configurations for the channels under consideration.

• Communications for Statistical Applications and Methods
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• v.26 no.3
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• pp.325-336
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• 2019

In this article we extend the discrete Weibull regression model in the presence of missing data. Discrete Weibull regression models can be adapted to various type of dispersion data however, it is not widely used. Recently Yoo (Journal of the Korean Data and Information Science Society, 30, 11-22, 2019) adapted the discrete Weibull regression model using single imputation. We extend their studies by using multiple imputation also with several various settings and compare the results. The purpose of this study is to address the merit of using multiple imputation in the presence of missing data in discrete count data. We analyzed the seventh Korean National Health and Nutrition Examination Survey (KNHANES VII), from 2016 to assess the factors influencing the variable, 1 month hospital stay, and we compared the results using discrete Weibull regression model with those of Poisson, negative Binomial and zero-inflated Poisson regression models, which are widely used in count data analyses. The results showed that the discrete Weibull regression model using multiple imputation provided the best fit. We also performed simulation studies to show the accuracy of the discrete Weibull regression using multiple imputation given both under- and over-dispersed distribution, as well as varying missing rates and sample size. Sensitivity analysis showed the influence of mis-specification and the robustness of the discrete Weibull model. Using imputation with discrete Weibull regression to analyze discrete data will increase explanatory power and is widely applicable to various types of dispersion data with a unified model.

• Journal of Preventive Medicine and Public Health
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• v.38 no.2
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• pp.132-140
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• 2005

Objectives: To propose a risk-adjustment model from insurance claims data, and analyze the changes in cesarean section rates of healthcare organizations after adjusting for risk distribution. Methods: The study sample included delivery claims data from January to September, 2003. A risk-adjustment model was built using the 1st quarter data, and the 2nd and 3rd quarter data were used for a validation test. Patients' risk factors were adjusted using a logistic regression analysis. The c-statistic and Hosmer-Lemeshow test were used to evaluate the performance of the risk-adjustment model. Crude, predicted and risk-adjusted rates were calculated, and compared to analyze the effects of the adjustment. Results: Nine risk factors (malpresentation, eclampsia, malignancy, multiple pregnancies, problems in the placenta, previous Cesarean section, older mothers, bleeding and diabetes) were included in the final risk-adjustment model, and were found to have statistically significant effects on the mode of delivery. The c-statistic (0.78) and Hosmer-Lemeshow test ($x^2$=0.60, p=0.439) indicated a good model performance. After applying the 2nd and 3rd quarter data to the model, there were no differences in the c-statistic and Hosmer-Lemeshow $x^2$. Also, risk factor adjustment led to changes in the ranking of hospital Cesarean section rates, especially in tertiary and general hospitals. Conclusion: This study showed a model performance, using medical record abstracted data, was comparable to the results of previous studies. Insurance claims data can be used for identifying areas where risk factors should be adjusted. The changes in the ranking of hospital Cesarean section rates implied that crude rates can mislead people and therefore, the risk should be adjusted before the rates are released to the public. The proposed risk-adjustment model can be applied for the fair comparisons of the rates between hospitals.

• Health Policy and Management
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• v.33 no.1
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• pp.85-106
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• 2023

Background: The Korean government has established Health Plan and reinforced tobacco control policies step by step according to Framework Convention on Tobacco Control (FCTC). This study aims to investigate yearly smoking and secondhand smoking (SHS) exposure rates adjusted by demographic and socioeconomic factors. Methods: Multiple logistic regression analysis was conducted about the smoking experience, current smoking, and exposure to SHS at home, at work, and in public places using data from the 6th to 8th Korea National Health and Nutrition Examination Survey (2015-2020). Results: Comparing 2015 with other years, smoking experience rates significantly decreased from 2015 to 2018 in men and significantly increased from 2018 to 2020 in women. Compared to 2015, current smoking rates significantly decreased only in 2020 for men and significantly increased in 2018 and 2019 for women. The rate of exposure to SHS at home significantly decreased until 2018. Rates of exposure to SHS in the workplace and public places were significant all year. Conclusion: There were a slowly decreasing trend in men and an increasing trend in women at current smoking rates. It was found that there were significant decreasing trends at exposure to SHS. There is a need to set policies that reduce current smoking rates and especially to set a customized program to lower women's smoking rates.

• The Korean Journal of Applied Statistics
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• v.21 no.6
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• pp.1045-1063
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• 2008

This paper derives conversion formulas from yearly-based absolute rates of decrements to monthly-based rates of decrement due to cause j under FI (fractional age independence) assumption that is a generalization of UDD assumption. Next, it suggests conversion formulas from monthly-based absoluterates of decrements to monthly-based rates of decrement due to cause j under FI assumption. In addition, it calculates conversion formulas from yearly-based rates of decrement due to cause j to the corresponding monthly-based absolute rates of decrements under FI assumption. Some numerical examples are discussed.

• The Korean Journal of Food And Nutrition
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• v.26 no.3
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• pp.329-338
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• 2013

This study is conducted to compare the problems affecting dietary habits and health status between a long-term exercise group and non-exercise group of males older than 50 years. Most subjects of the two groups consider regular exercise to be the most important factor for maintaining health, and recognize hypertension as the number one concern. The most common nutritional supplement among subjects is multiple vitamins, and sleeping time range from 6~8 hours. Breakfast fasting rate was 15.9% among non-exercise group (NEG), where overeating and eating out rates were higher among exercise group (EG) when comparing to NEG. Fasting rates of breakfast, and consumption rates of milk and dairy products, vegetables such as kimchi, and fruits and fruit juices are higher among the EG. Overeating and eating out rates are lower among NEG, whereas eating rates of proteins like meat, fish, eggs, beans, fried foods, high-fat meats carbonated drinks, ice cream, and salt intakes are higher. Rates of health, dietary habits, and nutrient intakes are higher among EG. Energy intakes among the two groups were below the standard level, Vitamin $B_2$ intake is low in EG, and folic acid and calcium intakes were higher in NEG. The exercising group care more about health, eating habits and nutrient intakes, and low smoking rates are being observed. Thus, specific dietary improvement programs for adult men, are required, and it is necessary to consider the practice of nutrition education.