• Korea journal of population studies
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• v.21 no.1
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• pp.162-183
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• 1998

This study examines the sampling bias that may have resulted from the large number of missing observations. Despite well-designed and reliable sampling procedures, the observed sample values in DSFH(Demographic Survey on Changes in Family and Household Structure, Japan) included many missing observations. The head administerd survey method of DSFH resulted in a large number of missing observations regarding characteristics of elderly non-head parents and their children. In addition, the response probability of a particular item in DSFH significantly differs by characteristics of elderly parents and their children. Furthermore, missing observations of many items occurred simultaneously. This complex pattern of missing observations critically limits the ability to produce an unbiased analysis. First, the large number of missing observations is likely to cause a misleading estimate of the standard error. Even worse, the possible dependency of missing observations on their latent values is likely to produce biased estimates of covariates. Two models are employed to solve the possible inference biases. First, EM algorithm is used to infer the missing values based on the knowledge of the association between the observed values and other covariates. Second, a selection model was employed given the suspicion that the probability of missing observations of proximity depends on its unobserved outcome.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.253-262
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• 1994

The patterns of the conventional radiation treatment fields and their shielding blocks are analysed to determine the optimal dimension of the MultiLeaf Collimator (MLC) which is considered as an essential tool for conformal therapy. Total 1109 radiation fields from 303 patients (203 from Asan Medical center, 50 from Baek Hosp and 50 from Hanyang Univ. Hosp.) were analysed for this study. Weighted case selection treatment site (from The Korean Society of Therapeutic Radiology 1993). Ninety one percent of total fields have shielding blocks. Y axis is defined as leaf movement direction and it is assumed that MLC is installed on the cranial-caudal direction. The length of X axis were distributed from 4cm to 40cm (less than 21cm for $95\%$ of cases), and Y axis from 5cm to 38cm (less than 22cm for $95\%$ of cases). The shielding blocks extended to less than 6cm from center of the field for $95\%$ of the cases. Start length for ninety five percent of block is less than 10cm for X axis and 11cm for Y axis. Seventy six percent of shielding blocks could be placed by either X or Y axis direction, $7.9\%$ only by Y axis, $5.1\%$ only by X axis and It is reasonable to install MLC for Y direction. Ninety five percent of patients can be treated with coplanar rotation therapy without changing the collimator angle. Eleven percent of cases of cases were impossible to replace with MLC. Futher study of shielding technique is needed for $11\%$ impossible cases. The treatment field dimension of MLC should be larger than $21cm{\times}22cm$. The MLC should be designed as a pair of 21 leaves with 1cm wide for an acceptable resolution and 17cm long to enable the leaf to overtravel at least 6cm from the treatment field center.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.572-577
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• 2008

In order to apply strategic advanced project management to the Korean construction industry, the study conducted a comparative analysis of the project management body of knowledge of the advanced countries such as the USA and Japan as well as Europe. As a result, it was found that the connection to 'execution' of 'strategy' was highlighted as a common main issue in the theoretical background of project management body of knowledge, and strategic planning, which aligns 'program management' based on the integration of multiple project management and operations in single project with 'portfolio management' for selection and concentration, has been emphasized. Accordingly, the study built up the framework for the application of strategic advanced project management for strategic action in the Korean construction industry and proposed the following applicable solutions for implementation into the current Korean construction industry: 1) Innovate global competitiveness by preparing an 'ideology and philosophy' for the strategic action of an organization, 2) Establish a strategic 'environment' in consideration of the culture and structure of an organization, 3) Propose a strategic 'vision' for attaining a realizable goal within an organization, 4) Create an 'investment' on the portfolio in line with the strategy, 5) 'Execute' the program through the portfolio and project management. Lastly, the study brought up strategies for sustainable growth by applying strategic advanced project management to the Korean construction industry with a view to acquiring 'Performance' through the implementation and operation of their integrated system.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.63-72
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• 2018

This study was conducted to explore the impact of learning strategies on the level of participation in the online collaborative learning process. To do this, We studied 91 students who took professorship courses at A university in the Seoul metropolitan area. At the beginning of the semester, the learning strategies were measured through MSLQ, rehearsal, elaboration, organizing, critical thinking, metacognition, learning management, effort control, peer learning, and seeking help. Next, cooperative tasks were carried out to measure the interaction, and group composition consisted of 4-5 persons. The level of participation was measured by scores given to the messages created for interaction. The process of collaborative learning was divided into the steps of identifying learning goals, learning plans, performing individual learning, sharing learning results, and writing reports. The effects of learning strategies on participation level were analyzed through multiple regression analysis (stepwise selection method). As a result, the learning goal step influenced the highest level of metacognition, and the learning plan is the management of the learning time, the demonstration of the learning execution, the adjustment of the effort, the acquisition of help, the collegial learning, Writing was influenced by organization, elaboration, critical thinking, and critical thinking, metacognition, and elaboration.

• The Journal of the Korea Contents Association
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• v.16 no.12
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• pp.132-142
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• 2016

The study aimed to examine the state of visual acuity tests in preschoolers and determine the factors affecting the deterioration of their vision. A total of 172 pair, child aged 5-7 years and either one of their parents, were recruited from childcare centers or kindergarten between August 2015 and January 2016. Questionnaires were administered to the parents, and the children's visual acuities were measured. Using forward selection in logistics regression analysis, factors affecting vision deterioration were elucidated. Of 172 children, 128 (74.4%) had undergone a visual acuity test previously and 77 (44.8%) showed a deterioration in their vision. Children who had undergone their first visual acuity test after the age of 7 years (OR=7.425, CI=2.844- 19.385) and showed more abnormal eye symptoms, such as squinting or tilting the head to see or falling down frequently (OR=3.084, CI=1.202-7.914) and whose age was younger (OR=10.335, CI=3.252-32.848), were more likely to develop deterioration of vision. Children who had a posture such that they looked up at the computer monitor from below (OR=.075, CI=.022-.255), were less likely to show deterioration of vision. It can be inferred that early visual acuity tests is essential to detect deteriorated vision of preschoolers. Therefore, it is necessary to educate parents, personnels in day care center, and health clinics about the importance of early visual acuity tests and close observation of specific behaviors related to vision deterioration. Development of precautionary intervention program of vision deterioration in preschoolers and examination of its effects are needed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.125-135
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• 2015

The tendency of more longer span length being required economical in railway bridges is studying about PSC I shaped girder. In this case, it is important to analyze and choose the effective girder section for stiffness of bridge. This study investigates the dynamic properties and safety of PSC I shaped girder being used wide upper flange whose selection based on radii and efficiency factor of flexure for railway bridge in different span type. In addition, 40m PSC Box girder bridge adopted in Honam high speed railway is further analyzed to compare dynamic performance of PSC I shaped girder railway bridge with same span length. Time history response is acquired based on the mode superposition method. Static analysis is also analyzed using standard train load combined with the impact factor. Consequently, the result met limit values in every case including vertical displacement, acceleration and distort.

• Journal of Korean Society of Forest Science
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• v.79 no.3
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• pp.278-284
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• 1990

We have demonstrated expression of bacterial genes transferred into cells of Populus nigra ${\times}$ P. maximowiczii by A. tumefaciens strain 6044 (pGA 472). We determined the optimum concentration of kanamycin sulfate for effective selection of punctured leaf transformed using Agrobacterium binary vector pGA 472 containing a neomycine phosphotransferase gene (NPT-II) which confers kanamycin resistance. The combination of cefotaxime (200mg/l) and carbenicillin (300mg/l) showed good performance of discarding Agrobacterium from inoculated punctured leaf. A relatively low concentration (10mg/l) of kanamycin sulfate inhibited callus and shoots induction from punctured leaf. Number of shoots regenerated from co-cultured punctured leaf was 3.0 on MS basal medium supplemented with 10 mg/l kanamycin sulfate, while that of not co-cultured punctured leaf was none. The regeneration rate was 10% from the punctured leaf co-cultured on MS medium with 10 mg/l kanamycin. Regenerated shoots are developing from micropropagation for Southern blot analysis and inheritance of the kanamycin resistance trait (NPT-II).

• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.312-322
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• 2010

In Korea, Torreya nucifera (L.) Siebold & Zuccarini is widely distributed in the warm temperate zone of South coastal area and Jeju island, mainly as preserved forest in the vicinity of the Buddhist temple and Confucian temple. The objective of this study is in order to develop the conservation method and comprehension of vegetation community by current vegetation structure analysis of Torreya nucifera stand. As the results, the number of surveyed species in Torreya nucifera stand were total 148 species with 28 species of tree layer, 38 species of subtree layer, and 82 species of shrub layer. The appearance of the common species were Ligustrum obtusifolium Siebold & Zucc., Hedera rhombea Bean, and Trachelospermum asiaticum Nakai var. asiaticum. All the story of the surveyed region, Torreya nucifera maintained the current dominant species, but the subtree layer and shrub layer was decreased dominant rate because of the development of the crown of tree layer and biased growth of the subtree layer. Most of the tree layer and subtree layer in Torreya nucifera stands are composed of the sprout forest. Therefore, these results suggest that in order to maintain the healthy stand it is demanded for the application of selection thinning method for reducing crown competition in Torreya nucifera forests.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.4
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• pp.191-203
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• 2018

Identify the effects of ISO quality management system on the durability of the enterprise by applying it to early startups and small - and medium-sized enterprises. In particular, the quality management system of a technology start-up small and medium sized companies is important in applying the management system to the financial, management and quality control services rather than to research and development. The quality management system is applied to the medical equipment manufacturers, mobile phone brokers, foreign Chinese companies, and components manufacturers for diesel engines.Try it. Check the case where the quality management system has been applied to the company concerned and the nonconformities have been improved. In addition, the success of the project was determined by applying the quality control system to maintain the stability and perpetuation of the company through the case of the failed selection. The company explains that recently, it must appoint internal auditors to carry out continuous improvement activities and that those who want the development and continuity of the company must reflect the quality management system.

• Journal of Digital Convergence
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• v.18 no.9
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• pp.265-275
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• 2020

The burden of injury is widely considered to be very severe in our society. Nonetheless, we don't have enough data for injury surveillance. The objective of this research is to select and supplement CORE DATA for injury surveillance. For this purpose, this study had analyzed the literature such as the Quality Assessment Report about 'Causes of Death Statistics', 'Health Insurance Statistics' and 'Hospital Discharge Injury Surveillance' according to the six dimension of Statistics Quality. The analysis result is that 'Cause of Death Statistics' and 'Health Insurance Statistics' have the usefulness as the CORE DATA for injury surveillance. But there is a significant shortcoming in the Health Insurance Statistics, which is that there is a lack of the data about the external causes of injury. For supplementing the defect, this study proposes the system that the medical institutions should obligatorily report the external causes of injury when claim National Health Insurance Medical Care Expenses. As the results of this system, we can expect 'Establishing of Injury pyramid', 'Data Connecting with the National Pension' and 'Improving the Promptness of Injury Data'. And we expect the follow-up study for the realization of this system.