• The Korean Journal of Financial Management
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• v.26 no.1
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• pp.165-188
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• 2009

This paper has suggested the methodology for the frontier portfolios and the optimal portfolio under the mean-VaR framework, not assuming the normal distribution and considering the investor's preferences for the higher moments of return distributions. It suggested the grid and rank approach which did not need an assumption about return distributions to find the frontier portfolios. And the optimal portfolio was selected using the utility function that considered the 3rd and the 4th moments. For the application of the methodology, weekly returns of the developed countries index, the emerging market index and the KOSPI index were used. After the frontier portfolios of the mean-variance framework and the mean-VaR framework were selected, the optimal portfolios of each framework were compared. This application compared not only the difference of the standard deviation but also the difference of the utility level and the certainty equivalent expressed by weekly expected returns. In order to verify statistical significances about the differences between the mean-VaR and the mean-variance, this paper presented the statistics which were obtained by the historical simulation method using the bootstrapping. The results showed that an investor under the mean-VaR framework had a tendency to select the optimal portfolio which has bigger standard deviation, comparing to an investor under the mean-variance framework. In addition, the more risk averse an investor is, the bigger utility level and certainty equivalent he achieves under the mean-VaR framework. However, the difference between the two frameworks were not significant in statistical as well as economic criterion.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.60-68
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• 2008

This work describes a re-configurable 10MS/s to 100MS/s, low-power 10b two-step pipeline ADC operating at a power supply from 0.5V to 1.2V. MOS transistors with a low-threshold voltage are employed partially in the input sampling switches and differential pair of the SHA and MDAC for a proper signal swing margin at a 0.5V supply. The integrated adjustable current reference optimizes the static and dynamic performance of amplifiers at 10b accuracy with a wide range of supply voltages. A signal-isolated layout improves the capacitor mismatch of the MDAC while a switched-bias power-reduction technique reduces the power dissipation of comparators in the flash ADCs. The prototype ADC in a 0.13um CMOS process demonstrates the measured DNL and INL within 0.35LSB and 0.49LSB. The ADC with an active die area of $0.98mm^2$ shows a maximum SNDR and SFDR of 56.0dB and 69.6dB, respectively, and a power consumption of 19.2mW at a nominal condition of 0.8V and 60MS/s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.77-85
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• 2008

This work proposes a 12b 130MS/s 108mW $1.8mm^2$ 0.18um CMOS ADC for high-quality video systems such as TFT-LCD displays and digital TVs requiring simultaneously high resolution, low power, and small size at high speed. The proposed ADC optimizes power consumption and chip area at the target resolution and sampling rate based on a three-step pipeline architecture. The input SHA with gate-bootstrapped sampling switches and a properly controlled trans-conductance ratio of two amplifier stages achieves a high gain and phase margin for 12b input accuracy at the Nyquist frequency. A signal-insensitive 3D-fully symmetric layout reduces a capacitor and device mismatch of two MDACs. The proposed supply- and temperature- insensitive current and voltage references are implemented on chip with a small number of transistors. The prototype ADC in a 0.18um 1P6M CMOS technology demonstrates a measured DNL and INL within 0.69LSB and 2.12LSB, respectively. The ADC shows a maximum SNDR of 53dB and 51dB and a maximum SFDR of 68dB and 66dB at 120MS/s and 130MS/s, respectively. The ADC with an active die area of $1.8mm^2$ consumes 108mW at 130MS/s and 1.8V.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.371-377
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• 2020

The purpose of this study is to investigate the effects of satisfaction with green space on life satisfaction and to examine mediating effect of subjective health status in the relationship between satisfaction with green space and life satisfaction of older adults living in cities. For the purpose of the study, older adults aged over 65 years old who participated in 2018 Social Survey conducted by Statistics Korea were analyzed. A total of 4,567 older adults were analyzed using multiple regression analyses and significance of mediating effect was examined using bootstrapping method. Results of the analyses showed that satisfaction with green space had a significant effect on life satisfaction. Since a higher level of satisfaction with green space increased the level of life satisfaction, a direct effect of satisfaction with green space on life satisfaction was revealed. Also satisfaction with green space had a significant effect on subjective health status, so persons with a higher level of satisfaction with green space perceive their subjective health more positively. In regard to mediating effect, subjective health status partially mediated the relationship between satisfaction with green space and life satisfaction of the urban elderly. Results of this study show that green space can be used as an intervention method to improve health and life satisfaction of the urban elderly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.227-236
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• 2016

This study tested the effects of stress on smartphone addiction via depression and self-efficacy among college students, and the analysis results were as follows: setting mediator and extra variables significantly correlated with the criterion variable as covariates and applying the regression analysis and SPSS Macro as well as bootstrapping method, to verify the mediating effects of depression and self-efficacy in stress and smartphone addiction. This study analyzed the direct effects of stress on the depression, self-efficacy, and smartphone addiction of college students and found that stress had direct effects on their depression and self-efficacy and also indirect effects on their smartphone addiction via depression and self-efficacy. Both depression and self-efficacy had dual and partial mediating effects on the influences of stress on their smartphone addiction. Stress had significant dual mediating effects on their smartphone addiction via the indirect paths of depression and self-efficacy, and high stress also had significant direct effects on their smartphone addiction, thus validating the dual mediation model. These findings demonstrate the need to develop programs to mitigate the stress and depression of college students and enhance their self-efficacy in order to reduce their smartphone addiction.

• Korean Journal of Family Social Work
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• no.53
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• pp.235-263
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• 2016

The purpose of this study was to examine the relationships among caregiving stress, depression, and partner violence by gender. Data were gathered though questionnaires surveying 223 cases living in the Seoul and Kyeonggi, Pusan areas. In analyzing precess, the researchers used t-test, ANOVA, correlation and regression. Additionally, bootstrapping was used to verify the significant mediating effect of depression. The findings are follows: First, approximately 37.3 percent of adult children caregivers reported having experienced partner violence in the past year. And the depression mean score among adult children caregivers was 1.00, higher compared to 0.73 of general population. Female caregiving burden and depression level was higher than those of male. Second, the results from regression analysis revealed that caregiving stress influenced to partner violence positively. Depression has the full mediating effect between caregiving stress and partner violence. The results suggest a necessity of intervention to reduce caregiving stress, depression and prevent partner violence in the dementia caregiver's family. The implications for social work practice were also discussed.

• 한국노년학
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• v.38 no.4
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• pp.905-922
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• 2018

The purpose of this study was to examine the mediating effects of generativity and ego-integration on the relationship between leisure activity experience and life satisfaction after retirement, and to clarify the structural relationship between variables. In this study, SPSS for window 21.0 program r and AMOS 18.0 were used. First, correlation analysis was performed among the main variables to investigate the relationship between variables. Next, confirmatory factor analysis and fit of hypothesis model were confirmed. Finally, the bootstrapping procedure was conducted to verify the significance of the indirect effect. The main results of this study are as follows. First, leisure activity experience, life satisfaction, generativity and ego-integration were statistically correlated. Second, in the research model, there was a double-mediated effect of the generativity and ego-integration in the married couple's leisure experience and life satisfaction after retirement. The indirect effect that affects life satisfaction was found to be greater through mediation. This study has limitations in collecting data on retirees who have retirement experience or retired husbands who have. The reason for this is that there is a difference in the sense of life satisfaction between the couple and their spouse, and the significance of the path between the variables may also differ. Therefore, the follow-up study suggests the necessity of analyzing only the couple.

• 한국노년학
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• v.38 no.2
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• pp.291-308
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• 2018

The purpose of this study is to analyze the factors influencing financial preparedness for retirement of the middle-aged North Korean defectors (resettling in South Korea) using concepts of 'financial literacy' and 'financial inclusion'. Those questioned were 100 North Korean defectors of 40-60 years-old residing in Seoul and Gyeonggi-do Province selected by convenience sampling, one of the non-probability sampling. Path analysis is used as a main analysis method. The results of the study show a direct effect in which increased financial literacy resulted in better financial preparedness for retirement among middle-aged North Korean defectors at a statistically significant level. In addition, by boost-trapping method, financial inclusion has its mediating effect on the relationship between financial literacy and financial preparedness for retirement. However, this study shows that influence of financial literacy on financial preparedness for retirement is different across economic statues. The mediating effect of financial inclusion on the relationship between financial literacy and financial preparedness is statistically significant only for the low-income group. Meanwhile, for the above average income group, financial literacy has a direct effect on the financial preparedness after retirement at a statistically significant level. Based on these results, this study suggests practical and policy implementation such as necessity of customized financial education suited to their economic status, development of financial instruments for retirement, introduction of financial social workers to prepare stable old age of North Korean defectors.

• The Journal of the Korea Contents Association
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• v.19 no.8
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• pp.641-652
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• 2019

The current study was conducted to examine the dual mediating effect of dysfunctional belief and ambivalence over emotional expressiveness in the relationship between the parents' psychological control scale perceived by university students and interpersonal problems. For that purpose, 305 4-year university students in G Metropolitan City and J Province were surveyed to rate the parents' psychological control scale, dysfunctional belief, ambivalence over emotional expressiveness, and interpersonal problems. The data were analyzed using SPSS 22.0 and SPSS Macro. As a result, it was found that dysfunctional belief and ambivalence over emotional expressiveness had a mediating effect in the relationship between the parents' psychological control scale and interpersonal problems. Also, dysfunctional belief and ambivalence over emotional expressiveness had a dual mediating effect on the relationship between psychological control scale and interpersonal problems. As a result of testing the significance of the mediating effect through Bootstrapping, dysfunctional belief and ambivalence over emotional expressiveness had a significant dual mediating effect. The purpose of the current study was to establish a useful theoretical foundation for counseling strategies to efficiently help through counseling the university students who are having difficulties with interpersonal relations due to parental control.

• Environmental and Resource Economics Review
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• v.28 no.2
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• pp.277-306
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• 2019

Mackerel is one of the most widely consumed aquatic products in Korea. Concerns about the depletion of stocks have also arisen as the catch has decreased. The primary purpose of this study is to estimate the mackerel stock and derive the optimal level of catch in Korea. We apply a generalized maximum entropy econometric method to estimate the mackerel growth function, which does not require the steady state assumption. We incorporate a bootstrapping approach to derive the significance levels of parameter estimates. We found that the average ratio of catch to the estimated total stock was less than 30% before the 1990s but exceeded 40% in the 1990s. After 2000, it dropped back to about 36%. This finding indicates that mackerel may have been over-fished in the 1990s, but the government regulations introduced in the 2000s alleviated over-fishing problems. Nevertheless, our dynamic optimization analysis suggests that the total allowable catch may need to be carefully controlled to achieve socially optimal management of resources.