• Journal of the Korea Society for Simulation
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• v.9 no.4
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• pp.67-75
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• 2000

Often system analysts are interested in the estimation of percentile for system performance. For instance, in PERT network system, the percentile that the project. Typically the control variate method is used to reduce the variability of mean response using the correlation between the response and the control variates with a little additional cost during the course of simulation. In the same spirit, we apply this method to estimate the percentile of project completion time in PERT system, and evaluate the efficiency of the controlled estimator for its percentile.1 Simulation results indicate that the controlled estimators are more effective in reducing the variances of estimators than the simple estimators, however those tend to a little underestimate the percentiles for some critical values. We need more simulation experiments to examine such a kind of bias problem. We expect this research presents a step forward in the area of variance reduction techniques of stochastic simulation.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.129-135
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• 1996

In this paper, the hot carrier effect and device degradation of deep submicrometer SC-PMOSFETs have been measured and characterized. It has been shown that the substrate current of a 0.15$\mu$m PMOSFET increases with increasing of impact ionization rate, and the impact ionization rate is a function of the gate length and gate bias voltage. Correlation between gate current and substrate current is investigated within the general framework of the lucky-electron. It is found that the impact ionization rate increases, but the device degradation is not serious with decreasing effective channel length. SCIHE is suggested as the possible phusical mechanism for enhanced impact ionization rate and gate current reduction. Considering the hot carrier induced device degradation, it has been found that the maximum supply voltage is about -2.6V for 0.15$\mu$m PMOSFET.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.52
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• pp.347-354
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• 1999

Statistical Process Control(SPC) which uses control charts is widely used to inspect and improve manufacturing process as a effective method. A parametric method is the most common in statistical process control. Shewhart chart was made under the assumption that measurements are independent and normal distribution. In practice, this assumption is often excluded, for example, in case of (equation omitted) chart, when the subgroup sample is small or correlation, it happens that measured data have bias or rejection of the normality test. A bootstrap method can be used in such a situation, which is calculated by resampling procedure without pre-distribution assumption. In this study, applying bootstrap percentile method to (equation omitted) chart, it is compared and evaluated standard process control limit with bootstrap percentile control limit. Also, under the normal and non-normal distributions, where parameter is 0.5, using computer simulation, it is compared standard parametric with bootstrap method which is used to decide process control limits in process quality.

• Communications for Statistical Applications and Methods
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• v.22 no.5
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• pp.445-462
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• 2015

This article deals with the problem of estimation of the population mean in presence of multi-auxiliary information in two occasion rotation sampling. A multivariate exponential ratio type estimator has been proposed to estimate population mean at current (second) occasion using information on p-additional auxiliary variates which are positively correlated to study variates. The theoretical properties of the proposed estimator are investigated along with the discussion of optimum replacement strategies. The worthiness of proposed estimator has been justified by comparing it to well-known recent estimators that exist in the literature of rotation sampling. Theoretical results are justified through empirical investigations and a detailed study has been done by taking different choices of the correlation coefficients. A simulation study has been conducted to show the practicability of the proposed estimator.

• ETRI Journal
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• v.44 no.2
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• pp.244-259
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• 2022

Bicycle- or bike-sharing systems (BSSs) have received increasing attention as a secondary transportation mode due to their advantages, for example, accessibility, prevention of air pollution, and health promotion. However, in BSSs, due to bias in bike demands, the bike rebalancing problem should be solved. Various methods have been proposed to solve this problem; however, it is difficult to apply such methods to small cities because bike demand is sparse, and there are many practical issues to solve. Thus, we propose a demand prediction model using multiple classifiers, time grouping, categorization, weather analysis, and station correlation information. In addition, we analyze real-world relocation data by relocation managers and propose a relocation algorithm based on the analytical results to solve the bike rebalancing problem. The proposed system is compared experimentally with the results obtained by the real relocation managers.

• Journal of Astronomy and Space Sciences
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• v.33 no.2
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• pp.137-146
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• 2016

The correlation between meteorological data collected at the optical wide-field patrol network (OWL-Net) Station No. 1 and the seeing of satellite optical observation data was analyzed. Meteorological data and satellite optical observation data from June 2014 to November 2015 were analyzed. The analyzed meteorological data were the outdoor air temperature, relative humidity, wind speed, and cloud index data, and the analyzed satellite optical observation data were the seeing full-width at half-maximum (FWHM) data. The annual meteorological pattern for Mongolia was analyzed by collecting meteorological data over four seasons, with data collection beginning after the installation and initial set-up of the OWL-Net Station No. 1 in Mongolia. A comparison of the meteorological data and the seeing of the satellite optical observation data showed that the seeing degrades as the wind strength increases and as the cloud cover decreases. This finding is explained by the bias effect, which is caused by the fact that the number of images taken on the less cloudy days was relatively small. The seeing FWHM showed no clear correlation with either temperature or relative humidity.

• Journal of Korean Neurosurgical Society
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• v.63 no.5
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• pp.550-558
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• 2020

To perform a systematic review of the data collected from case-control studies conducted earlier to investigate the correlation between E-selectin S128R polymorphism and ischemic stroke (IS) risk among the Chinese population. The PubMed, Web of Science, Chinese biomedical literature database (CBM), Chinese databases China National Knowledge Infrastructure (CNKI), WanfangData knowledge service platform (Wanfang Data), and information resource integration service platform (VIP) Databases were searched to retrieve case-control studies on the correlation between E-selectin gene S128R polymorphism and IS from the inception of the database till June 2019. The literature was screened, data were extracted, the risk of bias was reviewed, and the studies included were assessed independently by two reviewers. Stata ver. 12.0 software (Stata Corp LLC, College Station, TX, USA) was used to perform the meta-analysis. A total of 2907 cases from eight case-control studies involving 1478 IS patients and 1429 controls were included in this study. The R allele and RS genotype in E-selectin were found to be associated with the risk of IS as per the results of the meta-analysis (R vs. S : odds ratio [OR], 2.75; 95% confidence interval [CI], 2.15-3.51; p<0.00001; RS vs. SS : OR, 2.50; 95% CI, 1.95-3.19; p<0.00001; RR+RS vs. SS : OR, 2.85, 95% CI, 2.21-3.67; p<0.00001). The E-selectin gene S128R polymorphism is likely related to IS based on the results of a meta-analysis in the Chinese population, and the R allele and RS genotype of E-selectin may be IS risk factors.

• Journal of Korean Society for Quality Management
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• v.42 no.4
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• pp.647-664
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• 2014

Purpose: The purpose of this study was to evaluate administrative efficiency of the Korean university and to identify the factors which may affect on the efficiency of universities. In addition, last purpose of this study was to compare correlation among administrative, research and education model. Methods: The collected data through Higher Education in Korea were analysed using DEA (Data Envelopment Analysis). Furthermore, in order to provide the better accurate results by removing the bias of the results, this paper implements Bootstrap DEA. It also analyzed the causes of efficiency by Tobit Regression after setting the dependent variable as a proposed efficiency score and compared correlation analysis results between other models. Results: The results of this study are as follows; First, the Korean universities showed low administrative efficiencies. Second, efficiency of national universities are higher than it of private universities. Finally, the administrative and research education model have statistically significant correlation. However, usually many Korean universities focus their resources on education performance such as employment and rates to attract new students than research performances. Conclusion: This study shows that the administrative efficiency positively affects both research and educational efficiency. Approximately 70% of the Korean universities needs to improve their administrative efficiencies and to pay attention to enhance their poor services, low-level performances.

• Journal of Korean Elementary Science Education
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• v.39 no.4
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• pp.506-521
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• 2020

This study aims to develop a scientific creativity task which science-gifted elementary students can conduct on a field trip to a botanical garden, and to analyze the results from conducting the task. For this, 38 science-gifted fifth-graders from the Science-Gifted Education Center, located at the Office of Education, participated in a field trip to a botanical garden, as a part of their program. Prior to the program, researchers developed a scientific creativity task for outdoor education program, along with science education specialists and teachers. The tasks were to observe plants, and to create something new and useful, or, in other words, scientifically creative, based on the plants' characteristics. The students could submit at most three ideas. Also, they assessed their own ideas, and selected an idea that they thought was the most creative. The results were analyzed by using the scientific creativity formula. The main findings from this study are as follows. First, it was found that the scientific creativity formula had an upward bias in assessing originality. Second, the students tended to assess the usefulness of their own ideas more generously. Third, the correlation between self-assessment results and scores from the scientific creativity formula for originality was r=.43. Fourth, in formula-based assessments, the correlation between originality scores and usefulness scores was relatively high, at r=.56. Fifth, the correlation between a student's scientific creativity score and the number of his or her ideas was very low, at r=.23. Sixth, when the ideas chosen as the most creative by students were compared with the ideas that had the highest scores in formula-based assessments, it was shown that 8 out of 19 students (42.1%) did not choose the idea that appeared to be the most creative when graded by the formula. This study is concluded by discussing the lessons from the scientific creativity task analysis for primary science education and gifted education.

• Korean Journal of Health Education and Promotion
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• v.30 no.5
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• pp.201-210
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• 2013

Objectives: The public relies on the news media to understand health risks. To examine the surveillance function of Korean health journalism, this study compared the rank-order of the 10 most frequently diagnosed cancers with that of the 10 cancers most frequently covered by three major Korean newspapers. Methods: News stories published between 1999 and 2010 by the Chosun-Ilbo, Joong-Ang-Ilbo, and Dong-A-Ilbo were examined. Data on cancer incidence were collected using the epidemiological data published by a governmental public health institution. To compare the level of the crude rates and the amount of news coverage, rank-order correlation tests and regression analyses were employed. Results: A reduction in the rank-ordered correlation coefficient was observed despite an increase in the overall number of cancer news stories released. The significance of the correlation disappeared after 2006. The big difference of the rank order between the crude rate and the amount of news coverage was observed in the cancer of breast, uteri, thyroid, and gallbladder/biliary. Finally, the three newspapers did not follow the amount change in stomach, lung, liver, and uterine cervix cancer. The four cancers' rank orders of crude rate were lowering, signifying a reduction of the comparative dangerousness of the four cancers. Conclusions: The news media's customization of news content and the negative bias in journalism are suggested as possible influences on the news media's inaccurate representation of cancer risk.