• Journal of Labour Economics
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• v.24 no.1
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• pp.67-96
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• 2001

The recent economic crisis started at the end of 1997 has brought about changes in labor market practices. One of them is rapid increase in the ratio of workers with alternative employment arrangement, so-called contingent workers. This type of arrangement, unlike traditional employment arrangement, makes employers properly adjust employment to business cycles and it also makes it possible for employees to solve time and spatial constraints related to labor supply. However, recent experience has revealed its negative characteristics such as lower wage rate, deficient fringe benefits, insufficient job security. Using the data from the first and the second wave of the Korea Labor and Income Panel Survey, this study focuses on change in the tendency of being contingent workers and decomposition of the wage differentials among regular and contingent workers by estimating the switching regression model. Results show that the recent crisis significantly contributed to probabilities of being contingent workers, especially for women, the young, the older, and the lowly educated. Decomposition shows that one quarter or one third of 35% of wage differentials are due to the price effect that the same productive characteristics are differently paid by the types of employment arrangements.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.6
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• pp.561-568
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• 2011

The purpose of this study is to measure displacements that occurs on a surface and interior of slope model and the shape when the slope is destroyed at vibration experiment of the slope model using close range photogrammetry. The circle targets and sphere targets are installed on a chamber and a slope model, while the earthquake wave are applied in regular time interval. The close range photogrammetric images are acquired in each displacements step until the slope model is destroyed. Those photos are processed by image processing method and the center points of targets are automatically extracted. Furthermore, the three-dimensional coordinates of targets are calculated by image orientation and bundle adjustment processing. As a result, amount of displacement at each level is precisely measured and provided the basic information for assessing the slope stability using three-dimensional measurement of the target movement and slope destruction.

• Health Policy and Management
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• v.22 no.2
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• pp.207-224
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• 2012

This study estimates the total health expenditure of ambulatory dental care and explores the factors related to disbursements. The study used two waves of a 2008 Korea Health Panel (KHP) survey, of which each wave is composed of 7866 households and 24,659 persons. The KHP includes missing expanses of reimbursement data of the National Health Insurance (NHI), such as out-of-pocket, drugs, and private health insurance. The study estimates total monthly ambulatory dental expenditure and the sub-special categories of dental care. For influential factors analyses, the study exploits log-linear model with age, gender, education, job, equivalence income, the status of chronic diseases, means-tested benefit recipients, private insurance, and the composite deprivation index as independent variables. The total monthly outpatient health spending is estimated to be 102,468 won per household, and for dental, each household spends 31,115 won per month. Older age, means-test recipients, non-regular workers are more likely to spend less money on dental care, whereas private insurers, high income, and those who live in less deprived areas are more likely to spend more money for dental services. From the study we found that the KHP data are more suitable to estimate the total amount of health care markets, especially when the NHI coverage is low, such as for dental care in Korea.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.371-379
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• 2016

In the ship design process, ship motion and propulsion performance in sea waves became very important issues. Especially, prediction of ship propulsion performance during real operation is an important challenge to ship owners for economic operation in terms of fuel consumption and route-time evaluation. Therefore, it should be considered in the early design stages of the ship. It is thought that the averaged value and fluctuation of effective inflow velocity to the propeller have a great effect on the propulsion performance in waves. However, even for the nominal velocity distribution, very few results have been presented due to some technical difficulties in experiments. In this study, flow measurements near the propeller plane using a stereo PIV system were performed. Phase-averaged flow fields on the propeller plane of a KVLCC2 model ship in waves were measured in the towing tank by using the stereo PIV system and a phase synchronizer with heave motion. The experiment was carried out at fully loaded condition with making surge, heave and pitch motions free at a forward speed corresponding to Fr=0.142 (Re=2.55×106) in various head waves and calm water condition. The phase averaged nominal velocity fields obtained from the measurements are discussed with respect to effects of wave orbital velocity and ship motion. The low velocity region is affected by pressure gradient and ship motion.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.4
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• pp.240-247
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• 2013

Hydrodynamic characteristics of a planing craft are very sensitive to the hull form variations, especially when the craft navigates with high-speed. Therefore, we need to verify hydrodynamic performances of the craft during the process of hull form design. In this paper, motion performances of a 40ft class cruise leisure boat are evaluated by both model tests and theoretical analyses using two different methods. Model tests are carried out at calm sea and regular wave conditions using high speed towing carriage installed in SNU towing tank. Theoretical methods used are a empirical method proposed by Martin (1976) and a potential method based on Rankine panel (DNV, 2010). The results from the theoretical methods are compared with and verified by those of model tests. Results of empirical formula showed somewhat larger motion RAOs and resonant frequencies than those of model tests. Potential based method showed even larger discrepancies with the model test results. From the analyses of comparison results, we could confirm the limitation of each theoretical method and suggest the way of improvement for the better prediction of motion performances.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.24.1-24.13
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• 2022

Background: In modern society, depression is serious issue that causes socioeconomic and family burden. To decrease the incidence of depression, risk factors should be identified and managed. Among many risk factors for depression, this study examined socioeconomic risk factors for depression. Methods: We utilized first (2006), second (2008), and third (2010)-wave data from the Korean Longitudinal Study of Aging (KLoSA). Depressive symptom was measured with the 10-item Center for Epidemiological Studies Depression Scale, Short Form (CES-D-10) in the survey in 2008 and 2010. Three risk factors including job security, employment type and monthly income were measured in the survey in 2006. The association between risk factors and depressive symptom was analyzed by Cox proportional-hazard model. Results: We analyzed data from 1,105 workers and hazard ratios (HRs) for 3 risk factors were significant entirely. In addition, regular worker with high income group is the most vulnerable group of poor job insecurity on depression among male workers (HR: 1.73; 95% confidence interval [CI]: 1.07-2.81). Finally, HRs for 7 groups who had at least 1 risk factor had higher HRs compared to groups who had no risk factors after stratifying 3 risk factors. In the analysis, significantly vulnerable groups were total 5 groups and the group who had highest HR was temporary/daily workers with poor job security (HR: 2.51; 95% CI: 1.36-4.64). The results concerning women, regardless of job type, were non-significant. Conclusions: This study presented one or more risk factors among poor job security, low income, temporary/daily employment type increase hazard for depressive symptom in 2 or 4 years after the exposure. These results inform policy to screen for and protect against the risk of depression in vulnerable groups.

• Radiation Oncology Journal
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• v.26 no.3
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• pp.181-188
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• 2008

Purpose: In order to enhance the efficiency of respiratory gated 4-dimensional radiation therapy for more regular and stable respiratory period and amplitude, a respiration training system was designed, and its efficacy was evaluated. Materials and Methods: The experiment was designed to measure the difference in respiration regularity following the use of a training system. A total of 11 subjects (9 volunteers and 2 patients) were included in the experiments. Three different breathing signals, including free breathing (free-breathing), guided breathing that followed training software (guided-breathing), and free breathing after the guided-breathing (post guided-breathing), were consecutively recorded in each subject. The peak-to-peak (PTP) period of the breathing signal, standard deviation (SD), peak-amplitude and its SD, area of the one cycle of the breathing wave form, and its root mean square (RMS) were measured and computed. Results: The temporal regularity was significantly improved in guided-breathing since the SD of breathing period reduced (free-breathing 0.568 vs guided-breathing 0.344, p=0.0013). The SD of the breathing period representing the post guided-breathing was also reduced, but the difference was not statistically significant (free-breathing 0.568 vs. guided-breathing 0.512, p=ns). Also the SD of measured amplitude was reduced in guided-breathing (free-breathing 1.317 vs. guided-breathing 1.068, p=0.187), although not significant. This indicated that the tidal volume for each breath was kept more even in guided-breathing compared to free-breathing. There was no change in breathing pattern between free-breathing and guided-breathing. The average area of breathing wave form and its RMS in postguided-breathing, however, was reduced by 7% and 5.9%, respectively. Conclusion: The guided-breathing was more stable and regular than the other forms of breathing data. Therefore, the developed respiratory training system was effective in improving the temporal regularity and maintaining a more even tidal volume.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1982.05a
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• pp.11.2-12
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• 1982

The major advancement in phonosurgery due to recent development of laryngomicrosurgery enabled more accurate diagnosis and treatment of patient with voice disorders. Among large proportion of voice disordered patients, prominent linear furrow running parallel along the free edge of vocal cord extending from the vocal process to anterior commissure can be seen as well as incomplete closure during phonation. These cases were illustrated and coined as sulcus vocalis by Salvi in 1901, since then other similar paper was reported in Europe and Japan, but has not been reported in Korea. The exact etiology and therapeutic methods of sulcus vocalis has not been elaborated. At Department of Otolaryngology of Yonsei University College of Medicine a series of voice analysis were performed among those 35 patients with sulcus vocalis visited to Vocal Dynamics Laboratory from May, 1981 to March, 1982. Following is the result of clinical statistical investgation and therapeutic modality. 1) The incidance of sulcus vocalis among 290 patients with voice disorder visited to Vocal Dynamics Laboratory was approximately 12%(35 cases). 2) Onset of this voice disorder was most frequent among patient under 10 year-old groups; 19 cases (54%) followed by second decade, third decade groups in decreasing frequency respectably. 3) The etiology of sulcus vocalis was mostly unknown. The sequelae after measle (4 cases) and severe upper respiratory infection (3 cases) and congenital deformity (2 cases) were the possible causes of sulcus vocalis. 4) These patients were involved bilaterally in 25 cases (71%), left side only in 8 cases (23%) and right side only in 2 cases (6%). 5) Almost all patients complained hoarseness and 7 patients were suffering from chronic laryngitis. 6) In aerodynamic analysis, Maximal Phonation Time was decreased in 20 cases (57%), Phonation Quotient was increased in 22 cases (63%) and Mean Air Flow Rate was increased in 23 cases (66%). 7) Among them, 33 cases were analyzed with stroboscopy. The findings were as follows; incomplete glottic closure during phonation in 31 cases (93%), regular vocal cord movement in whole cases, asymmetric cord movement in 4 cases (12%), decreased amplitude in 5 cases (21%) and small mucosal wave in 24 cases (73%). 8) Intracordal Teflon injection in 5 cases and Sulcusectomy in 1 cases were performed as therapeutic management, however, the therapeutic results were not effective except one case with Teflon injection.

• Journal of Navigation and Port Research
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• v.31 no.8
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• pp.675-681
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• 2007

A numerical procedure is described for estimating the effects of the multi-directional irregular waves on the structural responses of the Tension Leg Platform (TLP). The numerical approach is based on a three dimensional source distribution method for hydrodynamic forces, a three dimensional frame analysis method for structural responses, in which the superstructure of TLP is assumed to be flexible instead of rigid. Hydrodynamic and hydrostatic forces on the submerged surface of a TLP have been accurately calculated by excluding the assumption of the slender body theory. The hydrodynamic interactions among TLP members, such as columns and pontoons, and the structural damping are included in structural analysis. The spectral description used in spectral analysis of directional waves for the linear system of a TLP in the frequency domain is sufficient to completely define the structural responses. This is due to both the wave inputs and responses are stationary Gaussian random process of which the statistical properties in the amplitude domain are well known. The numerical results for the linear motion responses and tension variations in regular waves are compared with the experimental and numerical ones, which are obtained in Yoshida et al.(1983). The results of comparison confirmed the validity of the proposed approach.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.615-624
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• 2016

In this study, two rectangular barges in close proximity were simulated to analyze the characteristics of motion responses due to hydrodynamic interactions. Using a numerical solution from DNV-GL SESAM, coupled stiffness matrix terms for these same FEM models were added to the multiple body modes in the surge direction. Potential theory was used to calculate the first order radiation and diffraction effects on the simulated barge models. In the results, the sheltering effect of the barges was not shown at 1.3 rad/s with hull separation of 20 m in transverse waves. The separation effect between the barges was more clear with longitudinal waves and a shallow water depth. However, sway forces were influenced by hull separation with transverse waves. The peaks for sway and heave motion and sway force occurred at higher frequencies as hull separation narrowed with longitudinal and transverse waves. Given a depth of 10 m, the sway motion on the lee side of a coupled barge made a significant difference in the range of 0.2-0.8 rad/s with transverse and oblique waves. Also, the peaks for sway force were situated at lower frequencies, even when incident waves changed.