• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.37 no.4
• /
• pp.82-89
• /
• 2014

Recently, the mineral resource protection policies and regulations in production countries of natural resources including rare metals are becoming more stringent. Such environment makes which market has malfunction. In other word, those are not perfect or pure market. Therefore because each market of natural resources have special or unique characters, it is difficult to forecast their market prices. In this study, we constructed several models to estimate prices of natural resources using statistical tools like ARIMA and their business indices. And for examples, Indium and Coal were introduced.

• ETRI Journal
• /
• v.24 no.3
• /
• pp.211-220
• /
• 2002

This study characterizes an oxide etching process in a magnetically enhanced reactive ion etching (MERIE) reactor with a $CHF_3/CF_4$ gas chemistry. We use a statistical $2^{4-1}$ experimental design plus one center point to characterize the relationships between the process factors and etch responses. The factors that we varied in the design include RF power, pressure, and gas composition, and the modeled etch responses were the etch rate, etch selectivity to TiN, and uniformity. The developed models produced 3D response plots. Etching of $SiO_2$ mainly depends on F density and ion bombardment. $SiO_2$ etch selectivity to TiN sensitively depends on the F density in the plasma and the effects of ion bombardment. The process conditions for a high etch selectivity are a 0.3 to 0.5 $CF_4$ flow ratio and a -600 V to -650 V DC bias voltage according to the process pressure in our experiment. Etching uniformity was improved with an increase in the $CF_4$ flow ratio in the gas mixture, an increase in the source power, and a higher pressure. Our characterization of via etching in a $CHF_3/CF_4$ MERIE using neural networks was successful, economical, and effective. The results provide highly valuable information about etching mechanisms and optimum etching conditions.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.16 no.4
• /
• pp.64-75
• /
• 2017

Previous count models using fixed parameter can not consider the unobserved heterogeneity, as the standard error of the count value is underestimated, excessive t-values are derived thereby reducing the reliability of the model. Also, the study of unsignalized intersections are inadequate because of the difficulty of collecting data and statistical limits for accurate analytical processes compared to the signalized intersections. The purpose of this study is to analyze the factors affecting traffic accidents by constructing the count model using random parameters, and it aimed to distinguish between existing studies based on the rural unsignalized intersections. As a result of the analysis, 7 variables were presented as significant variables, and 2 variables(presence of crosswalk, speed limit) were presented as random parameter.

• Journal of Korean Dental Science
• /
• v.7 no.2
• /
• pp.66-79
• /
• 2014

Purpose: To analyze the amount and pattern of tooth movement and the changes in arch dimension of mandibular dentition after orthodontic treatment using a new three-dimensional (3D)-indirect superimposition method. Materials and Methods: The samples consisted of fifteen adult patients with class I bialveolar protrusion and minimal anterior crowding, treated by extraction of four first premolars with conventional sliding mechanics. After superimposition of 3D-virtual maxillary models before and after treatment using best-fit method, 3D-virtual mandibular model at each stage was placed into a common coordinate of superimposition using 3D-bite information, which resulted in 3D-indirect superimposition for mandibular dentition. The changes in mandibular dental and arch dimensional variables were measured with Rapidform 2006 (INUS Technology). Paired t-test was used for statistical analysis. Result: The anterior teeth moved backward, displaced laterally, and inclined lingually. The posterior teeth showed statistically significant contraction toward midsagittal plane. The amounts of backward movement of anterior teeth and forward movement of posterior teeth showed a ratio of 6 : 1. Although the inter-canine width increased slightly (0.8 mm, P<0.05), the inter-second premolar, inter-first molar, and inter-second molar widths decreased significantly with similar amounts (2.2 mm, P<0.05; 2.3 mm, P<0.01; 2.3 mm, P<0.001). The molar depth decreased (6.7 mm, P<0.001) but canine depth did not change. Conclusion: A new 3D-indirect superimposition of the mandibular dentitions using best-fit method and 3D-bite information can present a guideline for virtual treatment planning in terms of tooth position and arch dimension.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.48 no.1
• /
• pp.157-165
• /
• 2011

It is challenging to detect foreground objects when background includes an illumination variation, shadow or structural variation due to its motion. Basically pixel-based background models including codebook-based modeling suffer from statistical randomness of each pixel. This paper proposes an algorithm that incorporates Markov random field model into pixel-based background modeling to achieve more accurate foreground detection. Under the assumptions the distance between the pixel on the input imaging and the corresponding background model and the difference between the scene estimates of the spatio-temporally neighboring pixels are exponentially distributed, a recursive approach for estimating the MRF regularizing parameters is proposed. The proposed method alternates between estimating the parameters with the intermediate foreground detection and estimating the foreground detection with the estimated parameters, after computing it with random initial parameters. Extensive experiment is conducted with several videos recorded both indoors and outdoors to compare the proposed method with the standard codebook-based algorithm.

• Journal of Environmental Health Sciences
• /
• v.45 no.6
• /
• pp.613-621
• /
• 2019

Objectives: This study was performed to examine the relationship between health behaviors, living environment, and asthma in adolescents in Korea. Methods: Information on adolescents' characteristics, including demographic factors, health behaviors, and doctor's diagnosis of asthma was obtained from the Korean Youth Risk Behavior Web-based Survey (2015). In total, 68,043 middle and high school students participated. Environmental characteristics, including city park area and outdoor PM₁₀ concentrations in 2015 were obtained from the Korean Statistical Information Service. The adolescents' and environmental characteristics were merged by local information. Multiple logistic regression models were used to investigate the risk factors affecting asthma in adolescents. Results: The prevalence of asthma in adolescents in 2015 was 8.8%. In the multiple logistic regression analysis, adolescents who were male, attended middle school, suffered obesity, experienced tobacco smoking, had physical activity levels of 2 to 4 days, had higher stress levels, and lived in areas with outdoor PM₁₀ concentrations more than 47 ㎍/㎥ were more likely to have asthma, while adolescents who had middle levels of family economic status were less likely to do so. Conclusions: The fact that PM₁₀ concentration can affect asthma is an important point in this study. Risk factors identified in this study could be used as basic data for the prevention and management of asthma in Korea.

• Journal of Applied Tourism Food and Beverage Management and Research
• /
• v.12 no.2
• /
• pp.59-78
• /
• 2001

The domestic food service industry has established its industrial basis since the overseas brands were introduced and international events were held in Korea. It also has showed a prominent growth rate as consumers began to show more interests in leisure and quality of working life(QWL) At this, the employees, constituting Points of contacts with consumers of the food service industry, have emerged as a Primarily critical concern in order for the food service industry, which can affect people in various ways, to adopt our own food culture and develop its business quality. In the food service industry, as a relatively labour-intensive industry, the manpower service is considered very important. Whether the industry succeeds or not depends on the role of employees as the quality of service of employees can decide the quality of the industry itself. In spite of the importance of employees in the food service industry, not many researches have been Performed on the personnel management of the industry, as Koreans traditionally have hold a prejudiced view on the food service industry and it is only a short time since the food business began to be considered as an industry. This thesis aims at research on the factors affecting job satisfaction of the employees by dealing with the importance and characteristics of the role of employees of the food service industry and theoretical background of the job satisfaction. The presumable factors affecting the job satisfaction are divided into several groups ; characteristics of organization, working condition, human relationship, psychological factors, and its reputation in the labour market. Hypotheses and models, where those factors affect the employees, are formed. Statistical methods such as correlation analysis and multiple regression are used in order to verify those hypotheses. Alternatives to improve job satisfaction of employees are suggested based on the analysis. It is expected that there will be more active researches on employees of the food service industry, as this thesis has selected employees of the food service industry as its subjects while subjects of similar researches have been mainly hotel employees so far.

• Journal of the Korean Data and Information Science Society
• /
• v.26 no.6
• /
• pp.1377-1386
• /
• 2015

GDP gap is closely related with economic activity of a country as a whole, especially with the economic fluctuations which is called business cycle. GDP gap is regarded as an important variable for the monetary policy of the central bank because it provides information on the excess demand pressures and employment matters. However, GDP gap may not provide enough information of the effect of recent economic structural change or the environmental change of domestic and external economic condition. In this paper, the GDP is decomposed by statistical filtering techniques and various models are fitted to estimate the influence of GDP gap on Inflation and see if it has been changed. Analysis results show that the influence of GDP gap on inflation decreased in the 2000s while that of global GDP gap increased. These results also support that recent low inflation rate is due to the change of overseas economic condition, such as a slowdown in exports resulting from the global recession, as well as domestic factors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.11
• /
• pp.1272-1279
• /
• 2012

In this paper, models for the average-year rain rate distribution and the correlation between the worst-month and the average-year rain rate distribution in domestic environment were proposed, using the rainfall measurement data with 1-minute integration time of Korea Meteorological Administration. Comparison of the proposed model with the existing ITU-R model showed that the average rain rate of the proposed model for the exceed time rate of 0.01 % is about 28 % higher than that of the ITU-R recommendation. In addition, the correlation model between the worst-month and the average-year rain rate distribution was quite different from the ITU-R model. It is recommended that the domestic rain rate distribution model should be used for calculation of the statistical characteristics of rain attenuation(exceeded-time-rate distribution of rain attenuation) which is essential for the design of wireless communication systems in domestic environment.

• Korean Institute of Interior Design Journal
• /
• v.23 no.4
• /
• pp.220-230
• /
• 2014

As office workers tend to spend more time indoors nowadays, the importance of physical environments has been emphasized. Those who work longer hours in the office are likely to get more stress from the environments. A number of studies have proved that the plants (natural elements) were effective in relieving stress. Therefore, it is concluded that interior landscape is effective on enhancing the psychological wellbeing of office workers. The purposes of this study were as follows: (1) to determine the best modulized designs through rating psychological indices, and (2) to prove its effectiveness by applying those designs onto actual office environments. This study was conducted from April, 2012 to November, 2012. The subjects of the study were comprised of 154 juniors and seniors in Seoul Women's University. They are university students who are seeking jobs upon graduation. To this end, field investigations, surveys, and literature reviews were conducted. The results of the study indicated as follows: First, the most optimal models for psychological wellbeing have been derived. Second, the interior landscape had a positive effect on the psychological wellbeing of the office workers. On the basis of these findings, interior landscape with greens plays a big role in promoting the psychological wellbeing of the office workers. Also, its effect can be maximized when modulized design is combined with interior landscape. The limit of this study lies in its simplicity of design elements as emotional design aspects were quantified for statistical processing. In the near future, further studies focusing on various design elements need to be carried out. To sum up, the researcher hopes that these findings contribute to psychological recovery of the office workers, and interior landscape becomes more prevalent in the workplace.