• Korean Journal of Social Welfare Studies
• /
• v.42 no.3
• /
• pp.291-327
• /
• 2011

The purpose of this study is to classify the type of retirement process among the mature-aged in Korea. The study used the panel data from Korean Labor Panel (year2~6) for the classification of retirement process through Optimal Matching and Cluster Analysis. Classification is made in 5 categories as 'peripheral-economically active', 'private-transfer dependent', 're-entering limited', 'securely exiting', 'exit-and-reentering'. First, "peripheral-economically active" is a group which frequently experienced job status change and work insecurity. Second, "private-transfer dependent" is a group in which private transfer is likely to be supplements income in the incidence of unemployment. Third, "re-entering limited" is a group in which the proportion of no financial support combined with the absence of any economic activity is the largest. Fourth, the type "Securely exit" is th group whose members switches over to non-economically active status with pension receipt. The last type is "exit-and-reenter" that the member are highly possible to reenter in the labor market and stay in long time regardless of with or without pension plan. To examine the inequality among the types of retirement process, the duration of each status is analyzed. First, in the situation of being non-economically active, the duration of status is maintain public pension receiving and duration stabile in "securely exit" group. For "private-transfer dependent" type, members are mostly dependent on private financial support and that duration of it is longest. Through the analysis of retirement process without under other financial supports, it is "securely-exiting" type for which the duration of full-time employment is longest. It appears that the duration of part-time employment is longest in "peripheral-economically active" type. And for the case of non-waged employment it is "exit-and-reenter" type. Finally, the redistribution policy based on life course perspective is necessary to prevent that the opportunity in the structure before retirement stage and the unfavorable position in labor market make worse disadvantage in retirement process and after that.

• Korean journal of applied entomology
• /
• v.24 no.1 s.62
• /
• pp.29-33
• /
• 1985

Every plant in $990m^2$ onion field was inspected for damages by the onion maggot. Maps were constructed every ten days to show which plants were infested and which were not from April 11 to May 21, 1984. The maps were sectioned into squares one of which contains 80 onion plants and the counts of damaged onions in each square were fitted to poisson and negative binomial distribution and tested by chi-square. We argue that the satisfactory fitness of the expected negative binomial $[P(x^2)>0.05]$ provided a useful description of the spatial distribution patterns of the damaged onions. Edge effect was tested by the differences of damage ratio and variance/mean ratio (${\sigma}^2/m$) between edge and center part. The result showed that the damage ratioes and variances of all the periods, ${\sigma}^2/m$ values after May 1 were greater in edge part than in center part. Again, the maps were sectioned into four blocks and the squares (sample units) were sectioned into quadrants. By application of the variance component technique, it was suggested that $2{\sim}8$ sample units for 5% sampling error and $1{\sim}2$ sample units for 10% error should be sampled randomly to estimate the damage ratio when $2{\sim}3$ quadrants were inspected.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.10 no.1
• /
• pp.17-24
• /
• 2008

This study was performed to estimate non-$CO_2$ greenhouse gases (i.e., GHGs) emission from biomass burning at a local scale. Estimation of non-$CO_2$ GHGs emission was conducted using Landsat TM satellite imagery in order to assess the damage degree in burnt area and its effect on non-$CO_2$ GHGs emission. This approach of estimation was based on the protocol of the 2003 IPCC Guidelines. In this study, we used one of the most severe fire cases occurred Samcheock in April, 2004. Landsat TM satellite imageries of pre- and post-fire were used 1) to calculate delta normalized burn ratio (dNBR) for analyzing burnt area and burn severity of the Samcheok large-fire and 2) to quantify non-$CO_2$ GHGs emission from different size of the burnt area and the damage degree. The analysis of dNBR of the Samcheok large-fire indicated that the total burnt area was 16,200ha and the size of the burnt area differed with the burn severity: out of the total burnt area, the burn severities of Low (dNBR < 152), Moderate (dNBR = 153-190), and High (dNBR = 191-255) were 35%, 33%, and 32%, respectively. It was estimated that the burnt areas of coniferous forest, deciduous forest, and mixed forest were about 11,506ha (77%), 453ha (3%), and 2,978ha (20%), respectively. The magnitude of non-$CO_2$ GHGs emissions from the Samcheok large-fire differed significantly, showing 93% of CO (44.100Gg), 6.4% of CH4 (3.053Gg), 0.5% of $NO_x$ (0.238Gg), and 0.1% of $N_2O$ (0.038Gg). Although there were little changes in the total burnt area by the burn severity, there were differences in the emission of non-$CO_2$ GHGs with the degree of the burn severity. The maximum emission of non-$CO_2$ GHGs occurred in moderate burn severity, indicating 47% of the total emission.

• Journal of the Korea Concrete Institute
• /
• v.19 no.1
• /
• pp.91-102
• /
• 2007

Through lessons in recent earthquakes, the bridge engineering community recognizes the need for new seismic design methodologies based on the inelastic structural performance of RC bridge structures. This study represents results of performance-based fragility analysis of reinforced concrete (RC) bridge. Monte carlo simulation is performed to study nonlinear dynamic responses of RC bridge. Two-parameter log-normal distribution function is used to represent the fragility curves. These two-parameters, referred to as fragility parameters, are estimated by the traditional maximum likelihood procedure, which is treated each event of RC bridge pier damage as a realization of Bernoulli experiment. In order to formulate the fragility curves, five different damage states are described by two practical factors: the displacement and curvature ductility, which are mostly influencing on the seismic behavior of RC bridge piers. Five damage states are quantitatively assessed in terms of these seismic ductilities on the basis of numerous experimental results of RC bridge piers. Thereby, the performance-based fragility curves of RC bridge pier are provided in this paper. This approach can be used in constructing the fragility curves of various bridge structures and be applied to construct the seismic hazard map.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.295-307
• /
• 2002

In the Nakdong River plain a very thick clayey soils are covered widely. Since the early 1990's, some huge reclamation projects have been performed for the development of industrial and residential complexes and so on. Despite a large number of soil investigations have been carried out for the projects, the geotechnical properties have never been elucidated well, so that the settlements of the ground due to the mischaracterized properties were greatly underestimated. Therefore, it has been needed to evaluate definitely the characteristics of the clayey soils, particularly for the compressibility characteristics to help understand the settlement behavior. For the compressibility characteristics of the Pusan clays, physical index and consolidation tests were conducted on the reconstituted and undisturbed samples. Using the result of physical index, the Pusan clays could be divided into two different units, which have different depositional environments. According to the concepts of Burland (1990) and Nagaraj et. al. (1990), the intrinsic state line and field compression curve of the Pusan clays could be established. It could be found from their concepts that the Pusan clays are under the cemented and young normally consolidated state and largely consisted of two units. The cementation of the clays was as well identified by compression index ratio (Tsuchida et. al.,1991) and sensitivity (Leroueil et. al.,1983).

• Journal of Korea Port Economic Association
• /
• v.31 no.1
• /
• pp.1-14
• /
• 2015

The standard GARCH model imposing symmetry on the conditional variance, tends to fail in capturing some important features of the data. This paper, hence, introduces the models capturing asymmetric effect. They are the EGARCH model and the GJR model. We provide the systematic comparison of volatility models focusing on the asymmetric effect of news on volatility. Specifically, three diagnostic tests are provided: the sign bias test, the negative size bias test, and the positive size bias test. This paper shows that there is significant evidence of GARCH-type process in the data, as shown by the test for the Ljung-Box Q statistic on the squared residual data. The estimated unconditional density function for squared residual is clearly skewed to the left and markedly leptokurtic when compared with the standard normal distribution. The observation of volatility clustering is also clearly reinforced by the plot of the squared value of residuals of export volume and values. The unconditional variance of both export volumes and export value indicates that large shocks of either sign tend to be followed by large shocks, and small shocks of either sign tend to follow small shocks. The estimated export volume news impact curve for the GARCH also suggests that $h_t$ is overestimated for large negative and positive shocks. The conditional variance equation of the GARCH model for export volumes contains two parameters ${\alpha}$ and ${\beta}$ that are insignificant, indicating that the GARCH model is a poor characterization of the conditional variance of export volumes. The conditional variance equation of the EGARCH model for export value, however, shows a positive sign of parameter ${\delta}$, which is contrary to our expectation, while the GJR model exhibits that parameters ${\alpha}$ and ${\beta}$ are insignificant, and ${\delta}$ is marginally significant. That indicates that the asymmetric volatility models are poor characterization of the conditional variance of export value. It is concluded that the asymmetric EGARCH and GJR model are appropriate in explaining the volatility of export volume, while the symmetric standard GARCH model is good for capturing the volatility.

• Journal of Korean Society of Transportation
• /
• v.33 no.5
• /
• pp.497-507
• /
• 2015

Nonrecurrent congestion of freeway was primarily caused by incident. The main cause of incident was known as a traffic accident. Therefore, accurate prediction of traffic incident clearance time is very important in accident management. Traffic accident data on freeway during year 2008 to year 2014 period were analyzed for this study. KNN(K-Nearest Neighbor) algorithm was hired for developing incident clearance time prediction model with the historical traffic accident data. Analysis result of accident data explains the level of accident significantly affect on the incident clearance time. For this reason, incident clearance time was categorized by accident level. Data were sorted by classification of traffic volume, number of lanes and time periods to consider traffic conditions and roadway geometry. Factors affecting incident clearance time were analyzed from the extracted data for identifying similar types of accident. Lastly, weight of detail factors was calculated in order to measure distance metric. Weight was calculated with applying standard method of normal distribution, then incident clearance time was predicted. Prediction result of model showed a lower prediction error(MAPE) than models of previous studies. The improve model developed in this study is expected to contribute to the efficient highway operation management when incident occurs.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.5 no.3
• /
• pp.127-136
• /
• 1985

A simplified single degree of freedom analog with mass-spring-dashpot is proposed in this study. The simplified analog can describe the dynamic behavior of a rigid circular footings whose contact pressures are parabolic. The analog proposed in this study shows remarkable agreement when compared with the elastic half-space theory the analog is also compared with vertical vibration test results of model concrete footings. For the vibration experiments, 11 circular footings with different mass ratio are constructed. The elastic half-space is represented by compacted sand layer. A constant force excitation vibrator is used for the dynamic loading. The frequency range for vibration tests is 30 to 100 Hz. From the dynamic experiments, it is found that the measured resonant frequencies agree very well with the analog results, however, the ratio of theoretical and measured resonant amplitudes vary between 0.5 and 1.7. It is also found that, when the dynamic force is increased, the resonant frequency is decreased slightly and the resonant amplitude is increased slightly.

• Journal of Biomedical Engineering Research
• /
• v.23 no.2
• /
• pp.109-117
• /
• 2002

Electrogastrography(EGG) is a noninvasive method for measuring gastric electrical activity on the abdomen resulting from gastric muscle. EGG signals have a very low frequency range (0.0083 ~0.15 Hz) and extremely low amplitude(10~100 uV). Consequently, EGG signal is easily influenced by other noises. Both finite impulse response(FIR) and infinite impulse response (IIR) filters need high orders or have phase distortions for passing very narrow bandwidth of the EGG signal. In this study, we decomposed EGG signals using a wavelet multiresolution method with Daubechies mother wavelet. The EGG signals were decomposed to seven levels. We reconstructed signal by summing the decomposed signals from level four to seven. To evaluate the performance of the wavelet multiresolution filter(WMF) with simulated EGG signal using two kinds of FIR and four kinds of IIR filters., we used two indices; signal to noise ratio(SNR) and reconstruction squared error(RSE). The SNR of WMF had 9.5, 6.9, and 4.7 dB bigger than that of the other filters at different noise levels, respectively. Also, The RSE of WMF had $1.22{\times}10^6, 1.16{\times}10^6, 1.02{\times}10^6$ smaller than that of the other filters at different noise levels, respectively. The WMF performed better in the SNR and RSE than two kinds of FIR and four kinds of IIR filters.

• Journal of Korean Orthopaedic Sports Medicine
• /
• v.4 no.2
• /
• pp.109-115
• /
• 2005

Purpose: The purpose of this study was to evaluate the effectiveness of three functional performance tests and one-legged hop test and to establish the reference data of the three functional performance tests of the active young Korean men. Materials and methods: We performed five tests on 40 normal subjects such as one-legged hop test (single hop, triple hop) and the three functional performance tests (carioca test, co-contraction test, shuttle run test). The mean age was 28.4 years. The mean score of Tegner activity scale was 6.2 and Lysholm score 98.2 Mean value and standard deviation were obtained. The correlation of age, height and weight with the results, the relationship between FPT and one-legged hop test and the mean difference between dominant and non-dominant limbs were statistically calculated. Results: All data obtained were normally distributed and there were no significant relationship between age, height and weight. The paired t-test of one legged hop test showed no statistical significance between dominant and non-dominant limbs. The results of one legged hop test had strong relationship with functional performance test. Conclusion; The three functional performance tests can be a useful functional test in ACL-insufficient athletes. Our results can be used as normal reference data of the normal active Korean men.