• Journal of the Korean Chemical Society
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• v.65 no.6
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• pp.433-440
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• 2021

Surfactants are organic compounds that have both hydrophilic and non-polar parts in one molecule, classified as non-ion, anion, cation, and amphoteric surfactants according to the charge of hydrophilic parts in aqueous state. A trace amounts may remain when vegetables and fruits are washed using type1 detergent (Vegetable and fruit detergent), and there is a possibility of exposure to the human body through ingestion. This study developed the simultaneous analysis method for 5 surfactants with LC-MS/MS for analysis of detergent residues after washing vegetables and fruits with detergent. The mobile phase used distilled water and acetonitrile containing 50 mM ammonium formate and 0.1% formic acid and was analyzed using a gradient method using XBridge BEH C8 column. The accuracy of the established method was 83.9-112.1%, and the precision was less than 20%. The detection limit was 7.0 (SLS) to 29.0 (SLES-N3) ㎍/L, and the correlation coefficient (r²) of calibration line regression was greater than 0.99, it is considered suitable for the analysis of trace amounts of surfactant components remaining in vegetables and fruits.

• Journal of Digital Convergence
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• v.16 no.3
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• pp.1-12
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• 2018

The objective of this study is to explore the way to improve baby boom generation's ICT skills in their daily life. This study explores the effect of leisure activities on ICT skills. The analysis used 2016 Korea Media Panel data. Results show that the more leisure activities baby-boomers participate, the higher ICT skills they could get. The result of 2SLS regression also supports the leisure activities' effect on the improvement of ICT skills. More specifically, watching performing art such as movies, musicals, affects the improvement of the integrated ICT skills, and creative hobbies such as cooking, painting, affect the ability to use video contents and e-commerce; shopping affects the improvement of communication and information searching with a digital device. These findings suggest that leisure activities could improve ICT skills for baby boom generation who are familiar with face to face communication.

• Health Policy and Management
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• v.14 no.4
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• pp.48-74
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• 2004

Considering the existence of asymmetric information between doctor and patient, the doctor's reimbursement method has been considered as a desirable policy device of improving efficiency of patient's use of medical care in terms of its affecting doctor's practice pattern by determining doctor's practice revenue. By using the Community Tracking Study (CTS) physician data set, which includes not only various information on doctors practice arrangements and sources of practice revenue, but also vignettes of various clinical presentations, this paper investigates doctor's reaction to the financial incentive under the control of patient's specific medical situation. Under the econometric model for exploring the effect of doctor's reimbursement method on his/her practice patterns; referring patients, recommend doctor-visit or medical tests, the Hausman's specification test was used for checking out the possibility of the doctor's reimbursement method being endogeneized explanatory variable. In the case where the endogeneity problem of doctor's reimbursement method exists, the 2SLS method was used for correcting that problem, and the multiple regression method was used in the case where the problem is found to be nonexistent. Based on the empirical results, this paper finds that doctors do appear to respond to financial incentive. The empirical results show that the doctor's reimbursement method statistically significantly affects doctor's practice pattern and are coincident with the theoretical result proposed by previous researches, This results suggest, as doctor's practice revenues are mainly determined by prospective method, such as capitation, doctors would more refer their patients to specialists, and hesitate in recommending doctor-visit or medical exam.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.611-620
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• 2016

Firms grow in a competitive environment and competition can be a source of corporate growth. In an increasingly global market, companies face increased competition. As such, it is natural that all firms face some degree of risk due to competition. While firms compete for market share, they also imitate competitors in order to minimize risk that accompanies competition. This research attempts to demonstrate the effects of inter-firm competition on investment decisions. Using idiosyncratic equity returns as the instrument variable, this paper uses a two-stage least squares regression, as well as an ordinary least squares (OLS), to identify the influence of peer firms' investment decisions on a firm's own investment strategy. The results confirm that firms show stronger imitative behavior with more intense competition. Also, firms with higher debt ratios show higher peer group influence. This imitative factor provides clues to measure the risk-averseness in investment decisions.

• KDI Journal of Economic Policy
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• v.28 no.2
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• pp.131-177
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• 2006

This paper examines a simultaneous determination of corporate control mechanisms, and its effects on firm performance. The corporate control mechanisms considered include the following; insider shareholding, institutional shareholding, the board of directors, dividend policy, and capital structure. This paper applies a simultaneous equation methodology and investigates the interdependence among the corporate control mechanisms. In the first part, the paper finds that firm-level variations of control mechanisms are large across time although average variations are relatively small. These variations are related to one another, which is confirmed by Granger causality test based on dynamic panel autoregression model. More specifically insider shareholding, institutional shareholding and outside director ratio cause each other. With regard to interdependence among the control mechanisms, 2SLS(two stage least squares) regression results show that insider shareholding and institutional shareholding are substitutes while institutional shareholding acts as complements to the ratio of outside members in the board of directors. Then in the second part, the paper examines the relationship between firm performance and corporate governance. Firm performance, measured by Tobin's Q, has a positive association with leverage ratio while that has a negative relation to outside director ratio. This suggests that there may be a room for reforming corporate governance in Korea. Specifically it is necessary to enhance the independence of the outside directors.