• The Korean Journal of Applied Statistics
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• v.26 no.5
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• pp.697-712
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• 2013

When analyzing repeated binary data, the generalized estimating equations(GEE) approach produces consistent estimates for regression parameters even if an incorrect working correlation matrix is used. However, time-varying covariates experience larger changes in coefficients than time-invariant covariates across various working correlation structures for finite samples. In addition, the GEE approach may give biased estimates under missing at random(MAR). Weighted estimating equations and multiple imputation methods have been proposed to reduce biases in parameter estimates under MAR. This article studies if the two methods produce robust estimates across various working correlation structures for longitudinal binary data with time-varying covariates under different missing mechanisms. Through simulation, we observe that time-varying covariates have greater differences in parameter estimates across different working correlation structures than time-invariant covariates. The multiple imputation method produces more robust estimates under any working correlation structure and smaller biases compared to the other two methods.

• Journal of the Korea Society of Computer and Information
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• v.25 no.9
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• pp.159-166
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• 2020

The purpose of this research is to suggest some practical and policy implications for improving adolescent's self-esteem through analyzing longitudinally the effects of parental attitude, peer relationship, student-teacher relationship, school learning activity, life-goal on adolescent's self-esteem by using latent growth curve model. Analytical data was obtained from the KYCPS. The analytical results showed that the change model of adolescent's self_esteem turned out to be a leaner model in which the change rate and intercept were significant. Second, time dependent variables influence on adolescent's self_ esteem meaningfully. Third, time dependent variables influence on adolescent's self_ esteem changes significantly. This study proposed some policy implications basing on these findings.

• Korean Journal of Computational Design and Engineering
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• v.10 no.4
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• pp.244-253
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• 2005

In the initial ship design stage of shipyards, the hull form design, the basic design (compartment modeling and ship calculation), and the hull structural design are being performed by different systems. Thus, the problem on interfaces between these systems occurs. To solve this, we developed the hull form design system 'EzHULL' and the compartment modeling and ship calculation system 'EzCOM-PART' for developing finally an integrated ship design system. And, in this study, we present an object-oriented hull structural design .system 'EzSTRUCT', which is developed recently. A structural design in an initial design stage can be frequently changed, because the design is not firmly determined yet. Therefore, designers perform the simplified structural modeling with bigger structural parts (or objects) such as deck, longitudinal bulkhead, etc. in the initial design stage, and the detailed structural modeling with smaller structural parts such as plate, seam, slot, etc. in the detailed design stage. However, the existing hull structural CAD system used in a shipyard is not efficient in generating a 3D CAD model in the initial design stage, because it has difficulty in handling frequent changes in design. Therefore, designers initially draw 2D drawings in the initial design stage, and generate the 3D CAD model from these 2D drawings in the detailed design and production design stages. In this study, the hull structural design system, which can efficiently generate a 3D CAD model through rapid modeling at an initial design stage, was developed in this study To evaluate the applicability of the developed system, we applied it to hull structural modeling of various ships such as a VLCC, a bulk carrier, etc. As a result, it could efficiently generate a 3D CAD model of a hull structure.

• Journal of Periodontal and Implant Science
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• v.47 no.2
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• pp.106-115
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• 2017

Purpose: The possibility of immediate or early loading has become popular in implant dentistry. A prerequisite for the immediate or early loading of an implant prosthesis is the achievement of initial stability in the implant. Moreover, in response to clinicians' interest in verifying clinical stability to determine the optimal time point for functional loading, a non-invasive method to assess implant stability has been developed on the basis of resonance frequency analysis (RFA). The primary objective of this study was to monitor the stability of sandblasted, large-grit, and acid-etched (SLA) implants with different diameters during the early phases of healing by RFA. The secondary objective was to evaluate how the initial stability of implants varied depending on different surface modifications and other contributing factors. Methods: Thirty-five implants (25 SLA implants and 10 resorbable blasting media [RBM] implants) placed in 20 subjects were included. To measure implant stability, RFA was performed at baseline and at 1, 2, 3, 4, 6, and 10 weeks after surgery. Results: The longitudinal changes in the implant stability quotient (ISQ) values were similar for the SLA implants with different diameters and for the RBM implants. During the initial healing period, the ISQ decreased after installation and reached its lowest values at 1 week and 2 weeks, respectively. The mean ISQ values in the SLA implants were significantly higher in ${\varnothing}5.0mm$ implants than in ${\varnothing}4.0mm$ implants. Men showed a higher ISQ than women. Mandibular sites showed a higher ISQ than maxillary sites. Conclusions: All implants used in this study are suitable for immediate or early loading under appropriate indications. A wider diameter and SLA surface treatment of implants could improve the stability, if the implant is fixed with at least 30 Ncm of insertion torque.

• Journal of Korean Academy of Nursing
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• v.45 no.1
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• pp.118-128
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• 2015

Purpose: Evidence suggests that some patients with breast cancer experience cognitive difficulties following chemotherapy. This longitudinal study was done to examine the prevalence of cognitive impairment and trajectory of cognitive function over time in women with breast cancer, who received adjuvant chemotherapy. Methods: Participants were 137 patients with breast cancer. They completed neuropsychological tests and the Functional Assessment of Cancer Therapy-Cognitive Function before adjuvant therapy (pretest), toward the end of adjuvant therapy (posttest), and 6 months after the completion of adjuvant therapy (follow-up test). Of the patients, 91 were treated with adjuvant chemotherapy and 46 patients who did not receive chemotherapy made up the comparison group. A reliable-change index and repeated-measure ANOVA were used for statistical analyses. Results: At the posttest point, over 30% of patients showed complex cognitive impairment and reported greater difficulty in subjective cognitive function. At the follow-up test point, 22.0% of patients exhibited complex cognitive impairment and 30.8% of patients complained of subjective cognitive impairment. Repeated-measure ANOVA showed significant decreases after receiving chemotherapy followed by small improvements 6 months after the completion of chemotherapy in cognitive domains of change for attention and concentration, memory, executive function, and subjective cognitive function. Conclusion: These results suggest that chemotherapy in patients with breast cancer may be associated with objective and subjective cognitive impairments. Further studies are needed to explore the potential risk factors and predictor of chemotherapy-related cognitive changes. Also nursing interventions for prevention and intervention of cognitive impairments should be developed and tested.

• Wind and Structures
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• v.23 no.5
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• pp.465-483
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• 2016

This study aims to enhance the understanding of the surface pressure distribution around rectangular bodies, by considering aspects such as the suction pressure at the leading edge on the top and side faces when the body aspect ratio and wind direction are changed. We carried out wind tunnel measurements and numerical simulations of flow around a series of rectangular bodies (a cube and two rectangular bodies) that were placed in a deep turbulent boundary layer. Based on a modern numerical platform, the Navier-Stokes equations with the typical two-equation model (i.e., the standard $k-{\varepsilon}$ model) were solved, and the results were compared with the wind tunnel measurement data. Regarding the turbulence model, the results of the $k-{\varepsilon}$ model are in overall agreement with the experimental results, including the existing data. However, because of the blockage effects in the computational domain, the pressure recovery region is underpredicted compared to the experimental data. In addition, the $k-{\varepsilon}$ model sometimes will fail to capture the exact flow features. The primary emphasis in this study is on the flow characteristics around rectangular bodies with various aspect ratios and approaching wind directions. The aspect ratio and wind direction influence the type of wake that is generated and ultimately the structural loading and pressure, and in particular, the structural excitation. The results show that the surface pressure variation is highly dependent upon the approaching wind direction, especially on the top and side faces of the cube. In addition, the transverse width has a substantial effect on the variations in surface pressure around the bodies, while the longitudinal length has less influence compared to the transverse width.

• Journal of Distribution Science
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• v.17 no.10
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• pp.107-114
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• 2019

Purpose - This is longitudinal research which aims to investigate the meaning of greenness to consumers' behavior. Consumers adopt green marketing as a new factor in product buying and consumption and more and more consumers prefer green product and services. Consumers' green buying behavior can be different from other purchasing experiences. There would be changes in the meaning of green as time passed and it can be different from countries to other countries. This study examines focus group studies with several groups. There is a ten-year gap between 2010 focus group and 2019 focus group interviews. With this ten-year gap, we can find the change of greenness to consumers. Research design, data, and methodology - The data were collected from Turkish, Korean, Kazakhstan people. This is a cross-sectional study and focus group interview was designed. We can gain information relevant to the research problem with using focus group study and get some insights into basic needs and attitudes of green marketing. The subjects for green purchase interviewee were confined to under 40 years old's shoppers regardless of gender. The first study was investigated with several groups in 2010 and the second interview were conducted in 2019. Results - Results show that the meaning of greenness for consumer has changed over time in accordance with the growing accordance of environmental sustainability. Basically, green marketing still means valuable, natural, recycle-able, good for health, clean, smart behavior, essential benefit. The concept of greenness significantly evolved since it was investigated in 2010. It moves away from focusing on specific environmental issues to considering global sustainability issues. Especially we found that greenness can be related with globalization, higher education, social status at the 2019 interview. Conclusions - This paper attempted to confirm the green marketing is essential and expands its meaning to various aspect. Usually, we can think green marketing is everywhere, therefore, people don't care about green issues in real. But consumers are adopting green marketing more and more, it can be a means to attract potential consumers. Therefore, companies should provide enough greenness information for people and they might apply greenness communication to attract potential customers.

• Korean Journal of Cleft Lip And Palate
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• v.2 no.1_2
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• pp.15-22
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• 1999

It is well known that the postoperative skeletal instability after Le Fort I osteotomy for advancement of maxilla in the cleft patients is one of the major surgical problems. So we had tried to compare the amount of relapse after Le Fort I advancement surgery in the horizontal and vertical positional change, angular change of reference points between cleft patients and non-cleft patients. Longitudinal records of 10 consecutive cleft patients (test group) and 20 non-cleft patients (control group) were analyzed. Lateral cephalograms were taken preoperatively, immediately postoperatively, and 2, 6, 12 months postoperatively. We measured horizontal and vertical changes (ANS, PNS, AI) and angular change (SNA) of the reference points and lines. In the test group, horizontal relapse of ANS, PNS, AI point are 36.4%, 37.5%, 32.0% respectively at 12 months postoperatively. The vertical relapse of ANS, PNS, AI are 25.3%, 32.3%, 39.1% respectively at 12 months postoperatively. The angular change of SNA is 33.6% at 12 months postoperatively. In the control group, horizontal relapse of ANS, PNS, AI point are 23.8%, 30.2%, 21.7% respectively at 12 months postoperatively. The vertical relapse of ANS, PNS, AI are 22.7%, 27.3%, 25.1% respectively at 12 months postoperatively. The angular change of SNA is 22.2% at 12 months postoperatively. The cleft patients have a larger tendency of skeletal and dental relapse compared with non-cleft patients after Le Fort I surgery. So the oral and maxillofacial surgeons must keep in mind these facts in order to minimize the relapse phenomenon from the beginning of surgical planning to postoperative care.

• The korean journal of orthodontics
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• v.19 no.1 s.27
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• pp.7-20
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• 1989

A serial cephalometric study was undertaken to define the growth of the soft tissue facial profile in Korean children. The sample was composed of 25 males and 15 females for whom yearly cephalometric records were taken from the ages of 6 to 13 years. From the tracings, points on skeletal and soft tissue profiles were located and recorded on magnetic tape utilizing a Calcomp Talos RP660 X-Y digitizer. Linear and angular measurements of soft tissues were made directly from tape in a Cyber 174-16 computer after cephalometric enlargement had been corrected. A statistical evaluation was made of the data and the average profile diagrams in male and female were described by a Calcomp 960 pen plotter. On the basis of the findings of this study, the following trends were established. 1. The most prominent growth in soft tissue facial profile thickness was the nose and the least was the forehead. 2. The general growth direction of the soft facial tissue to the cranium described the downward and forward. 3. The degree of soft tissue facial convexity was decidely more than that exhibited earlier in life even though the soft tissue chin had protruded to the cranium. 4. The measurements indicated a general tendency for males to have larger nose and more convex and long soft tissue facial profile than did females. 5. Males showed significantly more growth than females in base of the upper lip and height of the upper anterior facial profile. 6. There was a difference between males and females in the rates of soft tissue facial profile growth. 7. Korean children showed less convex in the soft tissue profile convexity than did American children.

• Korean Journal of Social Welfare
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• v.64 no.1
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• pp.101-124
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• 2012

This study examined the longitudinal changes of self-perceptions of own aging among middle-aged and elderly adults, using the latent growth modeling with the three waves of the "Aging and the Quality of Life of the Elderly in Korea", which sampled adults aged over 45 living in Seoul and Chuncheon. The dependent variable is attitudes toward own aging, the sub-scale of the Philadelphia Geriatric Center Morale Scale developed by Lawton (1975). The results showed that the research participants' attitudes of their own aging deteriorated over time. In addition, the lower initial status of the research participants' attitudes of their own aging was associated with being older, being non-married, living in rural areas, attaining the lower level of education, having the fewer social activities, reporting the worse subjective economic status, and reporting the worse subjective health status. The slope of the research participants' attitudes of their own aging differed by the residence areas, educational attainments, subjective economic status and subjective health status. In particular, the difference of the initial status by educational attainments grew over time. Social welfare policy and practice implications are discussed for middle-aged and elderly adults to improve attitudes toward their own aging.