• Steel and Composite Structures
• /
• v.48 no.2
• /
• pp.207-233
• /
• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• 한국노년학
• /
• v.39 no.4
• /
• pp.699-721
• /
• 2019

The purpose of this study was to examine and compare factors affecting the subjective life expectancy among the elderly, and to suggest health practice and social welfare service implications for later life. A total of 4,483 seniors from the 6th wave(2016) of the Korean Longitudinal Study on Aging (KLoSA) were used for analysis. The subjects were divided into three age groups: the young-old (n=2,106, 65~74 years), middle-old (n=1,803, 75~84 years), and oldest-old (n=574, 85 years and older). Control variables were sociodemographic factors and health status factors. Independent variables were health promotion behavior, cognition of public care, participating social activity, economic activity, and receiving basic pension. The data were analyzed using hierarchical multiple regression. The main results were as follows. Health promotion behavior was associated with the young-old. Social activities and economic activity were associated with the young-old and middle-old. Receiving basic pension had a significant impact on all age groups. In the middle-old, significant results were focused on socio-demographic and health status factors compared to other groups. The results of this study will provide basic data for the elderly policy and welfare service and will help to find and improve the important factors for the life of the elderly.

• Korean Journal of Social Welfare Studies
• /
• v.44 no.2
• /
• pp.169-199
• /
• 2013

This study has a purpose to analyze trajectories of life satisfaction of the elderly after their retirement and how the characteristics of individual, retirement and family relationship have an effect on the life satisfaction. This study has investigated the Korean elderly, who had been retired, using the data from three waves(1st wave(2005)~3rd wave(2009) of the Korean Retirement and Income Panel(KReIS). Data analysis has been used to identify the predictors of the intercept and slope related to the life satisfaction after retirement, focusing the trajectories of the life satisfaction after retirement and individual characteristics, retirement characteristics and family relationship with application of the growth curve model by Amos 20.0. First, the intercept of the life satisfaction after retirement was somewhat below average. Life satisfaction averagely increased little by little from 1st wave to 3rd wave. Second, by conducting the conditional growth curve model, the study revealed that the intercept of the life satisfaction after retirement is high on individual characteristics(sex, educational level, income, health status) and in retirement characteristics(voluntary retirement) and satisfaction with family relationship and married life). Furthermore, health status, voluntary retirement, and satisfaction with family relationship asserted the meaningful variables in the slope of life satisfaction after retirement.

• Asia Marketing Journal
• /
• v.15 no.3
• /
• pp.53-77
• /
• 2013

As advertising and promotions are categorized as operating expenses, managers tend to reduce marketing budget to improve their short term profitability. Gauging the value and accountability of marketing spending is therefore considered as a major research priority in marketing. To respond this call, recent studies have documented that financial market reacts positively to a firm's marketing activity or marketing related outcomes such as brand equity and customer satisfaction. However, prior studies focus on the relation of marketing variable and financial market variables. This study suggests a channel about how marketing activity increases firm valuation. Specifically, we propose that a firm's marketing activity increases the level of the firm's product market information and thereby the dispersion in financial analysts' earnings forecasts decreases. With less uncertainty about the firm's future prospect, the firm's managers and shareholders have less information asymmetry, which reduces the firm's cost of capital and thereby increases the valuation of the firm. To our knowledge, this is the first paper to examine how informational benefits can mediate the effect of marketing activity on firm value. To test whether marketing activity contributes to increase in firm value by mitigating information asymmetry, this study employs a longitudinal data which contains 12,824 firm-year observations with 2,337 distinct firms from 1981 to 2006. Firm value is measured by Tobin's Q and one-year-ahead buy-and-hold abnormal return (BHAR). Following prior literature, dispersion in analysts' earnings forecasts is used as a proxy for the information gap between management and shareholders. For model specification, to identify mediating effect, the three-step regression approach is adopted. All models are estimated using Markov chain Monte Carlo (MCMC) methods to test the statistical significance of the mediating effect. The analysis shows that marketing intensity has a significant negative relationship with dispersion in analysts' earnings forecasts. After including the mediator variable about analyst dispersion, the effect of marketing intensity on firm value drops from 1.199 (p < .01) to 1.130 (p < .01) in Tobin's Q model and the same effect drops from .192 (p < .01) to .188 (p < .01) in BHAR model. The results suggest that analysts' forecast dispersion partially accounts for the positive effect of marketing on firm valuation. Additionally, the same analysis was conducted with an alternative dependent variable (forecast accuracy) and a marketing metric (advertising intensity). The analysis supports the robustness of the main results. In sum, the results provide empirical evidence that marketing activity can increase shareholder value by mitigating problem of information asymmetry in the capital market. The findings have important implications for managers. First, managers should be cognizant of the role of marketing activity in providing information to the financial market as well as to the consumer market. Thus, managers should take into account investors' reaction when they design marketing communication messages for reducing the cost of capital. Second, this study shows a channel on how marketing creates shareholder value and highlights the accountability of marketing. In addition to the direct impact of marketing on firm value, an indirect channel by reducing information asymmetry should be considered. Potentially, marketing managers can justify their spending from the perspective of increasing long-term shareholder value.

• Journal of Trauma and Injury
• /
• v.36 no.3
• /
• pp.196-205
• /
• 2023

Purpose: Surgical stabilization of rib fractures (SSRF) is widely used in patients with flail chests, and several studies have reported the efficacy of SSRF even in multiple rib fractures. However, few reports have discussed the hardware failure (HF) of implanted plates. We aimed to evaluate the clinical characteristics of patients with HF after SSRF and further investigate the related factors. Methods: We retrospectively reviewed the electronic medical records of patients who underwent SSRF for multiple rib fractures at a level I trauma center in Korea between January 2014 and January 2021. We defined HF as the unintentional loosening of screws, dislocation, or breakage of the implanted plates. The baseline characteristics, surgical outcomes, and types of HF were assessed. Results: During the study period, 728 patients underwent SSRF, of whom 80 (10.9%) were diagnosed with HF. The mean age of HF patients was 56.5±13.6 years, and 66 (82.5%) were men. There were 59 cases (73.8%) of screw loosening, 21 (26.3%) of plate breakage, 17 (21.3%) of screw migration, and seven (8.8%) of plate dislocation. Nine patients (11.3%) experienced wound infection, and 35 patients (43.8%) experienced chronic pain. A total of 21 patients (26.3%) underwent reoperation for plate removal. The patients in the reoperation group were significantly younger, had fewer fractures and plates, underwent costal fixation, and had a longer follow-up. There were no significant differences in subjective chest symptoms or lung capacity. Conclusions: HF after SSRF occurred in 10.9% of the cases, and screw loosening was the most common. Further longitudinal studies are needed to identify risk factors for SSRF failure.

• Korean small business review
• /
• v.42 no.4
• /
• pp.69-102
• /
• 2020

Shedding new light on the research trend on entrepreneurial ecosystems in the 40-year history of the Asia Pacific Journal of Small Business, this study aims at exploring a potential measurement framework of ecological inputs and outputs in an entrepreneurial ecosystem that promotes entrepreneurship at geographical and spatial levels. As a result of the analysis of research on the entrepreneurial ecosystem in the journal, we found that prior studies emphasized the managerial importance of various ecological factors on the premise of possible causalities between the factors and entrepreneurship. However, empirical research to verify the premised causality has been underexplored yet. This literature gap may lead to unbalanced development of conceptual and case studies that identify requirements for successful entrepreneurial ecosystems based on experiential facts, thereby hindering the generalization of the research results for practical implications. In that there is a growing interest in creating and operating productive entrepreneurial ecosystems as an innovation engine that drives national and regional economic growth, it is necessary to explore and develop the measurement framework for ecological factors that can be used in future empirical research. Hereupon, we apply a conceptual model of 'input-output-outcome-impact' to categorize individual environmental factors identified in prior studies. Based on the model. We operationalize ecological input factors as the financial, intellectual, institutional, and social capitals, and ecological output factors as the establishment-based, innovation-based, and performance-based entrepreneurship. Also, we propose several longitudinal databases that future empirical research can use in analyzing the potential causality between the ecological input and output factors. The proposed framework of entrepreneurial ecosystems, which focuses on measuring ecological input and output factors, has a high application value for future research that analyzes the causality.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.18 no.4
• /
• pp.1-20
• /
• 2023

This study attempted to identify the relationship between the investment determinants of accelerators and investment performance through empirical analysis. Through literature review, four dimensions and 12 measurement items were extracted for investment determinants, which are independent variables, and investment performance was adjusted to the cumulative amount of subsequent investment based on previous studies. Performance data from 594 companies selected by TIPS from 2017 to 2019, which are relatively reliable and easy to secure data, were collected, and the subsequent investment cumulative attraction amount, which is a dependent variable, was hypothesized through multiple regression analysis three years after the investment. As a result of the study, 'industrial experience years' in the characteristics of founders, 'market size', 'market growth', 'competitive strength', and 'number of patents' in the characteristics of products and services had a significant positive (+) effect. The impact of independent variables on dependent variables was most influenced by the competitive strength of market characteristics, followed by the number of years of industrial experience, the number of patents, the size of the market, and market growth. This was different from the results of previous studies conducted mainly on qualitative research methods, and in most previous studies, the characteristics of founders were the most important, but the empirical analysis results were market characteristics. As a sub-factor, the intensity of competition, which was the subordinate to the importance of previous studies, had the greatest influence in empirical analysis. The academic significance of this study is that it presented a specific methodology to collect and build 594 empirical samples in the absence of empirical research on accelerator investment determinants, and created an opportunity to expand the theoretical discussion of investment determinants through causal research. In practice, the information asymmetry and uncertainty of startups that accelerators have can help them make effective investment decisions by establishing a systematic model of experience-dependent investment determinants.

• The korean journal of orthodontics
• /
• v.26 no.4
• /
• pp.325-340
• /
• 1996

Along with traditional goal of 'straightening teeth', today's orthodontics put more and more emphasis on facial esthetics. Naturally, the importance of soft tissue, which dictates one's facial form, is noticed. There have been many cephalometric studies on growth of hard tissue ; however, only a few on that of soft tissue. In Korea, various methods of sampling, measuring and analysing were used to study soft tissue changes, and yet, soft tissue changes along with process of normal growth have not been studied. The author carried out this study as a part of semi-longitudinal study on craniofacial growth and development of Korean children from ages of six to seventeen. 409 boys and 436 girls who'd had no systemic disease for the last three years and shown normal developmental and occlusal status were chosen as subjects. Cephalometric X-rays were taken of each subject, and facial form, lip position & form, nose form, and lip thickness were measured. Mean values and standard deviations were calculated according to age and gender, and figures and tables were drawn accordingly. The following results were obtained: 1. In respect to facial form, boys showed growth for longer period compared to girls. Also, lower face showed higher growth rate than upper face. 2. There was not much change in thickness of upper and lower lips with age; however, they appeared more prominent compared to caucasian children. 3. Nose grew horizontally with age. 4. Horizontal thickness of lower face increased with age, and upper lip thickness at nose base[A-Sn(FH)] showed more growth than anywhere else.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.40 no.3
• /
• pp.285-296
• /
• 1995

Anatomical studies of sink tissues are required for better understanding the biological plant growth system and energy metabolism. Kinematics of root growth zones of two genotypes of tall fescue (Festuca arundinacea Schreb.) receiving 50 or 200 ppm N were determined. Longitudinal anatomy and cell dynamics of root growth zones were studied and calculated. The root growth zone is organized similarly to the leaf growth zone which has cell division, elongation, and maturation zones, but the root growth zone is only about 3.0 mm long compared to 25 to 30 mm for the leaf growth zone. The root cap extends about 0.4 to 0.5 mm from the apical initial, while the cell elongation zone for both cortical and metaxylem cells extends about 3.3 mm from the apical initial for both genotypes and N levels. Root cap cells elongate from an initial length of about 5$\mu{m}$ long to a final length of about 40$\mu{m}$ before being sloughed. Initial lengths of cortical and metaxylem cells were about 8.5 $\mu{m}$ and 13.0 $\mu{m}$, respectively. Elongation of cortex and metaxylem cell showed sigmoidal curves with final lengths of about 120 $\mu{m}$ for cortex cells and 650 $\mu{m}$ for metaxylem cells. Initial size and final size for both types were not affected by N level, but cell fluxes and cell elongation rates of cortical and metaxylem cells were about double in low N. Cell production rates were about 5 to 6 times higher in cortical cells than in metaxylem cells. Differences in N caused a larger change in cell production rate, duration of cell elongation, and relative cell elongation rate than did the genotypes. These data indicate that N application affects root growth longitudinally by changing cell production rate and elongation rate.

• Korea journal of population studies
• /
• v.29 no.1
• /
• pp.185-207
• /
• 2006

Predominant explanations of the persistence of sex segregation ill occupations link job choices to profoundly gendered responses to childbearing and other family demands, arguing that women are more likely to seek jobs which are in some sense compatible with motherhood, either because they are family friendly (flexible, low intensity work) or because they are easy to exit and re-enter. In this paper, I examine the effect of occupational sex segregation on job exits into the labor market among women, with a special attention to the role of childbearing and child rearing. I use data from detailed employment histories gathered from the National Longitudinal Survey of Youth (NLSY) in continuous time event history models. My results indicate that women in female dominated jobs are less likely to exit their jobs than women in other types of occupations. Further this relationship is not shaped by motherhood. While mothers or pregnant women are more likely to leave work, mothers in female-dominated occupations are slightly less likely to leave employment than mothers in other occupations. These results are not consistent with the ideas that women's choice of female-dominated occupations expresses a gendered identity and women strategically seek jobs which accommodate maternal roles. Taken together, my findings do not provide support to the idea that women choose female-dominated occupations because they are easier to integrate with motherhood (except for the pregnancy period).