• Structural Engineering and Mechanics
• /
• v.85 no.4
• /
• pp.531-543
• /
• 2023

The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the non-stationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The non-stationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.

• Journal of Preventive Medicine and Public Health
• /
• v.38 no.3
• /
• pp.337-344
• /
• 2005

Objectives : Job insecurity, such as non-standard work, is reported to have an adverse impact on health, regardless of health behaviors. The aim of this study was to examine the relationship between non-standard employment and health in Korea. Methods : We analyzed a representative weighted sample, which consisted of 2,112 men and 1,237 women, aged 15-64, from the 1998 Korea National Health and Nutrition Examination Survey. Non-standard employment included part-time permanent, short time temporary and daily workers. Self-reported health was used as a health indicator. Results : This study indicated that women were more likely to report poorer health than men with standard jobs. Of all employees, 20.3% were female manual workers. After adjusting for potential confounders, such as age, education, equivalent income, marital, social and self-reported economic status and health behavior factors, nonstandard employment was found to be significantly associated with poor health among female manual workers (OR, 1.86; 95% CI, 1.24 to 2.79). No significant association was found in other working groups Conclusions : Among female manual workers, nonstandard employees reported significantly poorer health compared with standard workers. This result raises concern as there are increasing numbers of non-standard workers, particularly females.

• Korean Journal of Social Welfare
• /
• v.59 no.3
• /
• pp.147-174
• /
• 2007

This study examines how path dependency of working poor labor market segmented from the primary and the secondary labor market affects employment and quality of employment of working poor. It Further examines how path dependency makes working poor to remain in the labor market and makes it difficult for them to escape from a vicious poverty cycle. Data is based on the $3{\sim}7th$ Korea Labor and Income Panel Study(KLIPS). Markov's transition probability and discrete-time hazard analysis are used for analysis. This study finds that Korea labor market is divided into three parts; the primary labor market, the secondary labor market and the working poor labor market. The proportion of employed poor has been reduced, but the proportion of non economically-active working poor has been increased and has become the main group among the working poor. This shows that labor demand of working poor is fundamentally lacking and there are structural barriers that block working poor's employment itself. The regression analysis shows that the longer working poor labor market participation is, the lower poverty-exit rate. This is an evidence of vicious poverty cycle that the poor have little chance to exit from working poor labor market, once they step into it. Therefore, the longer their participation in poor labor market, the more likely they would move only within the closed working poor labor market. Consequently, it is necessary to fundamentally reform labor market structure and to alleviate negative perception and discrimination about the poor labor while activating labor demand.

• Journal of Agricultural Extension & Community Development
• /
• v.18 no.4
• /
• pp.861-877
• /
• 2011

The purpose of this study is to survey job stress and Musculoskeletal Disorder(MSDs) of workers in small plants with agricultural products. The subjects were comprised of 69 workers participated in "Helping the rural women to get the small businesses" project. The questionnaire surveys were Korean Occupational Stress Scale(KOSS), and Legal Risk Assessment of Musculoskeletal Disorders(KOSHA CODE H-30-2003). As a result of the survey, scores of KOSS 8 sub-items except for job demand were similar to that of Korea workers. Prevalence of MSDs symptoms of small plants workers was high percent (44.9%). And the rate according to kinds of product was significant difference at neck (p<0.01), lumbar (p<0.01), and leg (p<0.01). There was no significant difference between view person sign of MSDs and non MSDs according to sex, year, the number of workers, working years, working time per one day, rest time per one day, and subjective working intensity, but there were significant difference between high stress group and low stress group about MSDs at interpersonal conflict(p<0.05). Job stress and MSDs were important factor to workers of small plants producted agricultural products. Therefore, starting a business with small plats, workers consider interpersonal conflict and body part showing MSDs.

• Journal of the Chungcheong Mathematical Society
• /
• v.33 no.2
• /
• pp.237-253
• /
• 2020

This article studies asymptotic stability of non-auto nomous linear systems with time-dependent coefficient matrices {A(t)}_t∈ℝ. The classical theorem of Levinson has been widely used to science and engineering non-autonomous systems, but systems with defective eigenvalues could not be covered because such a family does not allow continuous diagonalization. We study systems where the family allows to have upper triangulation and to have defective eigenvalues. In addition to the wider applicability, working with upper triangular matrices in place of Jordan form matrices offers more flexibility. We interpret our and earlier works including Levinson's theorem from the perspective of invariant manifold theory.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.7
• /
• pp.856-863
• /
• 1999

The thermal performance degradation of heat pipes is caused by the non-condensable gas generation mainly due to the electrochemical corrosion which results from the reaction of working fluids with tube materials. In this study, a simplified method described below was proposed to estimate the life of heat pipes concerning the non-condensable gas generation. The temperature distributions at the outer surface of heat pipes was measured, and based on them the amount of non-condensable gas of hydrogen was estimated. Applying it to the Arrhenius model, the mass generation of hydrogen and the volume occupied by the gas In heat pipes could be estimated for an operating temperature and time. Moreover, this simplified method was applied to the accelerated life test of nine methanol-stainless steel heat pipe samples.

• The Journal of Fisheries Business Administration
• /
• v.47 no.2
• /
• pp.43-59
• /
• 2016

This study investigated the difference of the effects of public loan programs in fishery industry on management performance from a balanced score card (BSC) perspective depending on the type of loan, scale of fund, period of support and business category, using the financial data of fisheries firms having the balance of loan at the end of 2014. The key factors influencing credit rating change were also analyzed after public loan support. From a integrative perspective, results show that the firms supported by working fund have higher management performance than the firms supported by facility fund. The firms received large scale fund showed higher management performance than the firms received small scale fund. While management performance was decreasing or slowing down over time after financial support, management performance of the firms supported by facility fund improved over time. From a non-financial perspective, the firms received facility fund invested more in education and growing perspective than the firms received working fund. As the size of fund increased, the investment in education, growing, internal process and customer increased. Personnel expenses and employee benefits for education and growing has increased over time. However, the firms with facility fund restricted the expenses of education, personnel expenses and employee benefits as time goes by. Because the effects of public loan on credit rating of fisheries corporations have no statistical significance, it has become known that the financial support of public loan program has no influence on the change of credit rating of fisheries corporations. This study attempted performance analysis from a BSC perspective which combine factors of non-financial perspective with factors of financial perspective. Findings from this study suggest the direction of microscopic performance analysis of public loan in fishery industry.

• Journal of Preventive Medicine and Public Health
• /
• v.45 no.1
• /
• pp.37-46
• /
• 2012

Objectives: This study was performed to consider the association between Internet using time for non-educational purposes and adolescent health, and to examine how health status differs between Internet users and non-users. Methods: We analyzed 2009 data from the Korea Adolescent Risk Behavior Web-Based Survey, conducted on a nationally representative sample of students in grades 7 to 12. A total of 75 066 adolescents were categorized into four groups according to their Internet using time excluding using for educational purposes: non-Internet users (NIUs), occasional Internet users (OIUs) (<1 h/d), moderate Internet users (MIUs) (${\geq}1$ and <2 h/d), and heavy Internet users (HIUs) (${\geq}2$ h/d). Health factors included eight health risk behavior indices, four mental health indices and six physical health indices. Results: The distribution of Internet use was as follows: NIUs 17.4%, OIUs 68.1%, MIUs 12.7%, and HIUs 1.7%. In multivariate analysis, using OIUs as a reference, U- or J-shaped associations were observed for five health risk behavior indices (current smoking, current drinking, drug abuse, sexual intercourse, sedentary behavior on weekdays) and four mental health indices (stressed, depressed, suicidal ideation, attempted suicide) in both genders. After removing confounding effects, including age, region, school type, subjective school record, subjective economic status, presence of parents, living with family, and sedentary behavior, these associations were still observed. Conclusions: Health professionals should consider both Internet non-users (for non-educational purposes) and heavy users to be high-risk groups in terms of health status. Also, more well-designed studies are needed to clarify what factors are working in these nonlinear associations.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.542-545
• /
• 2005

This paper is concerned wi th the generation of the Lamb waves in a non­ferromagnetic plate by a recently-developed orientation-adjustable patch-type magnetostrictive transducer (OPMT) and the dispersion analysis from the measured Lamb waves. OPMT is capable of adjusting wave-propagation orientation only with a single installation on a plate. The mechanics behind the wave generation and measurement by the magnetostrictive phenomenon, the working principle of OPMT is explained and the actual generation and measurement of the Lamb waves were conducted in a 3 mm-thick aluminum plate. For the accurate analysis of the dispersion characteristics of the measured Lamb waves, a modified version of the short-time Fourier transform, known as the dispersion-based short-time Fourier transform, was employed. The results presented in this work would serve as the underlying research for an advanced non-destructive evaluation based on ultrasonic waves.

• Management & Information Systems Review
• /
• v.24
• /
• pp.73-75
• /
• 2008

The purpose of this study is to propose the human resource management strategies of non-standard workers that can contribute to accomplishing both corporate social responsibility and business purpose in efficient and effective ways. For the purpose, this researcher investigated circumstances under which Korean companies are using non-standard workers and systems related to those workers. In Korea, the Non-Standard Workers Protection Act was enacted and revised, and became effective on July 1, 2007. The main provisions of the act are as follows. First, the systems of discriminatory treatment prohibition was legally stipulated, Second, restrictions on overwork for fixed-term and part-time employees and the written statement of working conditions were compelled. Third, only 26 kinds of jobs were permitted for worker dispatch in accordance with positive list system. To achieve their business purpose, companies often use standard workers, but sometimes non-standard workers unavoidably in accordance with their business strategy. This study propose main human resource management strategies of non-standard workers such as determining the scope of jobs, strengthening legal and systematic human resource management, improving human relations, extending the grievance procedure and converting non-standard workers into standard ones.