• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.39-55
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• 1992

In this research, a Three Level Decomposition technique has been developed for configuration design optimization of truss structures. In the first level, as design variables, behavior variables are used and the strain energy has been treated as the cost function to be maximized so that the truss structure can absorb maximum energy. For design constraint of the optimal design problem, allowable stress, buckling stress, and displacement under multi-loading conditions are considered. In the second level, design problem is formulated using the cross-sectional area as the design variable and the weight of the truss structure as the cost function. As for the design constraint, the equilibrium equation with the optimal displacement obtained in the first level is used. In the third level, the nodal point coordinates of the truss structure are used as coordinating variable and the weight has been taken as the cost function. An advantage of the Three Level Decomposition technique is that the first and second level design problems are simple because they are linear programming problems. Moreover, the method is efficient because it is not necessary to carry out time consuming structural analysis and techniques for sensitivity analysis during the design optimization process. By treating the nodal point coordinates as design variables, the third level becomes unconstrained optimal design problems which is easier to solve. Moreover, by using different convergence criteria at each level of design problem, improved convergence can be obtained. The proposed technique has been tested using four different truss structures to yield almost identical optimum designs in the literature with efficient convergence rate regardless of constraint types and configuration of truss structures.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.277-290
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• 2016

Deep geological cross-sectional data is generally not common nor easy to construct, because it is expensive and requires a great deal of time. As a result, geological interpretations at depth are limited. Many scientists attempt to construct geological cross-sections at depth using geological surface data and geophysical data. In this paper, we suggest a method for constructing cross-sections from limited geological surface data in a target area. The reason for this study is to construct and interpret geological cros-sections at depth to evaluate heat flow anomaly along the Yangsan fault. The Yangsan Fault passes through the south-eastern part of the Korean Peninsula. The cross-section is constructed from Sangbukmyeon to Unchonmyeon passing perpendicularly through the Yangsan Fault System trending NW-SE direction. The geological cross-section is constructed using the following data: (1) Lithologic distributions and main structural elements. (2) Extensity of sedimentary rock and igneous rock, from field mapping. (3) Fault dimension calculated based on geometry of exposed surface rupture, and (4) Seismic and core logging data. The Yangsan Fault System is composed of the Jain fault, Milyang fault, Moryang fault, Yangsan fault, Dongnae fault, and Ingwang fault which strike NNE-SSW. According to field observation, the western section of the Yangsan fault bounded by igneous rocks and in the eastern section sedimentary rocks are dominant. Using surface fault length we infer that the Yangsan Fault System has developed to a depth of kilometers beneath the surface. According to seismic data, sedimentary rocks that are adjacent to the Yangsan fault are thin and getting thicker towards the east of the section. In this study we also suggest a new method to recognize faults using core loggings. This analysis could be used to estimate fault locations at different scales.

• Journal of Hospice and Palliative Care
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• v.14 no.2
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• pp.91-100
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• 2011

Purpose: This study was performed to investigate patients' preferences on receiving life-sustaining treatments (LST) and to analyze the relationship between patients' characteristics and LST selection. We also examined any discrepancy between LST patients' choices regarding medical intervention and actual medical intervention given/not given within 48 hours before death. Methods: This cross-sectional study was performed from March 1, 2008 to August 31, 2008 in the Palliative Care Unit of Korea University Hospital. Electric medical records (EMR) of 102 hospice cancer patients were reviewed, and 74 patients with Glasgow coma scale (GCS) ${\geq}$10 at the time of signing the advance medical directives (AMD) were selected for the first analysis. Then, patients alive at the end of this study, transferred to other hospitals or dead within 48 hours were excluded, and the remaining 42 patients were selected for the second analysis. Results: Preferred LST included antibiotics, total parenteral nutrition, tube feeding, transfusion, and laboratory and imaging studies. The relationship between patients' characteristics and LST could not be analyzed due to skewed preferences. LST chosen at the time of signing the AMD and actual medical intervention given/not given in the last 48 hours showed discrepancy in most cases. Conclusion: When making AMD in hospice cancer patients, it is important to consider the time and possibility of changing the choices. Above all, patients must fully understand the AMD. Thus, LST should always be provided with careful consideration of all possibilities, because legal and social aspects of AMD have not been established yet.

• Journal of the Korean Geographical Society
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• v.31 no.4
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• pp.699-715
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• 1996

This paper examines the cross-sectional development of children's conception of place. Previous research by Piaget and Weil, Jahoda, Daggs has questioned how young children develop the ablity to comprehend place. Oral interview and graphic test were made vy the children at the age of 5-14, in order to attain information on their knowledge, understanding and feeling about place. These data were used ti indentify developmental stages through cluster analysis. The results suggest that young children's conception of place develops with an identifiable 4 stages. There is no significant difference in development of conception of place between the 2nd year of kindergarten and the 1st year of elementary school, or the between the 5th, 6th year of elementary school and 1st, 2nd year of middle school. Rather, the 4th year of elementary school is an important and crucial truning point in the development of children's conception of place. It is concluded that children's conception of place develops in line with Piaget's general cognitive developmental theory in which the pre-conceptual stage ends at age 7 and the concrete-operation stage starts at age 11 to 12.

• Journal of agricultural medicine and community health
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• v.30 no.1
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• pp.15-28
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• 2005

Objectives: The purpose of this cross-sectional study was aimed to investigate the status of bowel health behaviors, prevalence of constipation and risk factors related to self-reported constipation in high school students. Methods: The study subjects were 1,882 students of six high schools located in a metropolitan city, who were selected by the accidental sampling from June to August, 2002. We analyzed the data by frequency analysis, chi-square test, and multivariate logistic regression using SPSS ver. 10.0. Results: The result of this study were summarized as follows: 1. A prevalence rate of self-reported constipation was 25.2%. A rate in male students was 13.4% and in female students 36.5%. 2. In regard to therapeutic behavior, 52.1% of study student with change in bowel habit had not find particular counsellor, 38.9% of the student had counselling with parents. 16.3% of students in constipation group had taken laxative medicine for treating the constipation. 73.5% of the student in constipation group had suffered from anal pain during defecation, but 48.0% in normal group. 41.6% of the student in constipation group had a experience of rectal bleeding after defecation, but 23.7% in normal group. So constipation related symptoms distribution had showed statistically significant difference between two group. 3. From the multivariate analysis by self-reported method, the risk factors related to the constipation were sex(female), experience of diet for weight reduction, absence of the breakfast and intake of vegetable more than 3 times per weeks. Conclusions: we had reconfirmed that we should improve eating habits to prevent and treat the constipation in a result of this study. Intervention that is target to girl students, abstain from weight reduction diet, regularity of taking meals, intake more vegetables, stress management should be provided to prevent the constipation especially in Korean high school students. Further prospective designed study are needed to establish the causal-effect relationship between so many risk factors with constipation.

• Journal of Korea Technology Innovation Society
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• v.12 no.4
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• pp.788-818
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• 2009

Renewable energy refers to solar energy, biomass energy, hydrogen energy, wind power, fuel cell, coal liquefaction and vaporization, marine energy, waste energy, and liquidity fuel made out of byproduct of geothermal heat, hydrogen and coal; it excludes energy based on coal, oil, nuclear energy and natural gas. Developed countries have recognized the importance of these energies and thus have set the mid to long term plans to develop and commercialize the technology and supported them with drastic political and financial measures. Considering the growing recognition to the field, it is necessary to analysis up-to-now achievement of the government's related projects, in the standards of type of renewable energy, management of sectional goals, and its commercialization. Korean government is chiefly following suit the USA and British policies of developing and distributing renewable energy. However, unlike Japan which is in the lead role in solar rays industry, it still lacks in state-directed support, participation of enterprises and social recognition. The research regarding renewable energy has mainly examinedthe state of supply of each technology and suitability of specific region for applying the technology. The evaluation shows that the research has been focused on supply and demand of renewable as well as general energy and solution for the enhancement of supply capacity in certain area. However, in-depth study for commercialization and the increase of capacity in industry followed by development of the technology is still inadequate. 'Cost-benefit model for each energy source' is used in analysis of technology development of renewable energy and quantitative and macro economical effects of its commercialization in order to foresee following expand in related industries and increase in added value. First, Investment on the renewable energy technology development is in direct proportion both to the product and growth, but product shows slightly higher index under the same amount of R&D investment than growth. It indicates that advance in technology greatly influences the final product, the energy growth. Moreover, while R&D investment on renewable energy product as well as the government funds included in the investment have proportionate influence on the renewable energy growth, private investment in the total amount invested has reciprocal influence. This statistic shows that research and development is mainly driven by government funds rather than private investment. Finally, while R&D investment on renewable energy growth affects proportionately, government funds and private investment shows no direct relations, which indicates that the effects of research and development on renewable energy do not affect government funds or private investment. All of the results signify that although it is important to have government policy in technology development and commercialization, private investment and active participation of enterprises are the key to the success in the industry.

• Journal of Nutrition and Health
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• v.47 no.2
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• pp.113-123
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• 2014

Purpose: Vitamin D has been known to play an important role in the central nervous system and brain functions in the human body, and cumulative evidence has shown that vitamin D deficiency might be linked with various mental health conditions. Epidemiologic studies have shown that vitamin D deficiency may be associated with higher risk of depression in the US and European populations. However, limited information is available regarding the association between vitamin D status and depression in the Korean population. The objective of this study was to examine the associations between vitamin D levels and prevalence of depression. Methods: We conducted a cross-sectional analysis using nationally representative data from the 2008-2010 Korean National Health and Nutrition Examination Survey from which serum 25-hydroxyvitamin D concentrations were available. A total of 18,735 adults who had available demographic, dietary, and lifestyle information were included in our analysis. We defined "depression" with a diagnosis by a physician. "Depressed condition" was defined as having feelings of sadness or depression without diagnosis by a physician. Results: The prevalence of depression was 1.63% and 5.43% in Korean men and women, respectively; 12.5% of men and 26.1% of women were defined as the group having depressed conditions. In multivariate logistic regression models, no significant associations were observed between vitamin D status and prevalence of depression or depressed conditions in Korean men and women. Conclusion: We found no association between vitamin D insufficiency and depression/depressed conditions in Korean adults. Future large prospective studies and randomized controlled trials are needed to confirm this relationship.

• Journal of Technology Innovation
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• v.29 no.3
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• pp.1-31
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• 2021

With the growing importance of technology innovation as a key factor for firms' competitive advantage, 'innovation persistence' became also an important research subject. 'Innovation Persistence' is a concept that indicates whether or not firms' innovation activity or performance continues. However, the data used for innovation studies are carried out as cross-sectional surveys in most countries. For this reason, studies dealing with longitudinal aspect of innovation persistence are rare. In particular, there is almost no research on innovation persistence using Korean innovation survey data. This study reviews the concepts and characteristics of innovation persistence based on extant literature, and perform an empirical analysis on the status and features of Korean firms' technology innovation persistence. Based on the data of the Korean Innovation Survey (KIS) conducted every other year from 2012 to 2018, panel data on 3,379 firms which observed multiple times are constructed. As a result, only part of the firms with persistent innovation were observed (for innovation performance 10~12%, for innovation activity 15~17%), and it was found that the persistence of non-innovation was remarkable(about 52~57%). And it was confirmed that the persistence of innovation activities is stronger than that of innovation performance. Besides, some features by sub-types of innovation appeared. Product innovation showed higher persistence than process innovation, and internal R&D also showed higher persistence than joint/external R&D. As a result of additional logit analysis to identify factors, it was found that radical or gradual product innovation is the most influential factor in persisting innovation in the next period. Since the sample selection bias due to a limitations of raw data might exist in the panel data constructed in this study, it should be noted that faulty generalization of the results are not allowed. Nevertheless, this is the first study to examine the technology innovation persistence targeting Korean firms and is expected to be a starting point for follow-up studies. It is anticipated that advanced research results will be drawn through the establishment of official panel data and improved methodologies.

• 한국노년학
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• v.38 no.3
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• pp.551-567
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• 2018

Demographic and socio-structural information is useful to identify potential welfare recipients who are in need of disease-prevention and intervention services. Thus, the present study aims to explore the differences in grip strength among middle and old-aged adults by living conditions and by living area. The 5th wave data of Korean Longitudinal Study of Aging was utilized. The dependent variable was grip strength, and the independent variables were living alone (living alone or not) and living area (city or non-city). Covariates were age, education, log-transformed household income, spouse existence, body mass index, self-rated health conditions, depressive symptoms, cognitive function, smoking, regular exercise, frequency of meeting with friends, and the number of social participation. Regression analysis was performed for middle-aged men, middle-aged women, old-aged men, and old-aged women, respectively. ANOVA and Chi-test were additionally used to specifically discuss significant results. Cross-sectional weight was applied to all analyses. According to the results, living alone and living area did not have significant effects on grip strength among middle-aged men, old-aged men, and old-aged women. In middle-aged women, however, living alone and living area were significantly associated with grip strength. To be specific, middle-aged women who lived alone in rural areas had the lowest grip strength compared to other middle-aged women. Additional analysis showed that middle-aged women who lived alone in rural areas had risk factors, such as low education level, low income, or high depressive symptoms. It implies that middle-aged women living alone in rural areas may have physical health risks, so they might be in need of disease prevention. This study is meaningful in that it can provide reliable information on the latent welfare recipients by using representative panel data and applying weight values.

• Journal of agricultural medicine and community health
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• v.46 no.1
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• pp.12-22
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• 2021

Backgrounds: Proper distribution and supply of physicians are factors that affect national health care systems. This study investigated the payment distribution levels and the determinants that influence the salary levels of hospital hired physicians. Methods: We analyzed 4,014 job advertisements posted on an internet invitation information site about physician recruitment from May 2016 to May 2019. We used univariate analysis to determine the relationship between average monthly salary and the other related variables. Multiple regression analysis was used to determine the predictors of physician salary level. Results: The average monthly salary for the service physician was 15.4 million won, highest for orthopedic surgeons with 22.24 million won, and lowest for diagnostic laboratory physician with 11.4 million won. The factors significantly associated with average monthly salary were; non-major specialty, housing provision, no severance pay, and incentives(p<0.05). Non-major specialty, incentives, and the regions were predictors of the average standardized monthly salary(p<0.05). Conclusion: Factors associated with average monthly salary as revealed by this study were; medical specialty, hospital regional location, housing provision, payment of retirement allowance, and payment of other incentives respectively. However, this study was a cross-sectional study, and further studies will be required.