• Korean journal of applied entomology
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• v.62 no.4
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• pp.267-275
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• 2023

Botanical extracts are employed in management of aphids. Extracts from Tanacetum cineariaiaefolium, Derris elliptica, and Sophora flavescens are widely used to control various insects. In this study, we determined concentrations of insecticidal active ingredients in commercial botanical extracts of these plants, and we investigated the time and concentration for lethal results with the green peach aphid, Myzus persicae. The concentrations of active ingredients, pyrethrins from T. cineariaiaefolium, rotenone from D. elliptica, and matrine and oxymatrine from S. flavescens, were determined after their fractionation by liquid chromatography followed by mass analysis and comparison with standard compounds. The extracts were tested for lethality in a bioassay with green peach aphids. Sprays at defined doses were applied to tobacco leaves infested with aphid nymphs. The lethal concentrations (LC50) were 20.4 ppm for pyrethrins, 34.1 ppm for rotenone, and 29.6 ppm for matrine at 48 h after treatments. At 100 ppm application levels, the lethal time LT50 was 13.4 h for pyrethrin, 15.1 h for rotenone, and 14.4 h for matrine. Kaplan-Meier analysis indicated the lethal times for the three botanical extracts at 100 ppm were significantly faster than application of a chemical insecticide, Sulfoxaflor, applied at the recommended level. These results provide baselines to develop and formulate single or mixed preparations containing botanical extracts to control green peach aphids on commercial crops.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.1
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• pp.133-144
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• 2017

This study investigates firm-specific financial variables that determine investment or speculative grades from the viewpoint of firms, which are one of the major stakeholders related to the credit rating. We employ an ordered probit model for our analysis with the sample data from 1999 to 2015 for listed firms in the Korean stock markets. For investment grades, operating margin, sales, market-to-book, dividend payment, capital expenditure ratio, and tangible asset ratio have a significantly positive impact on credit ratings. In the subsample for speculative grades, the coefficients of the dividend payment, retained earnings ratio, and capital expenditure ratio are significantly positive while short-term debt ratio and R&D expenditures have a significantly negative impact on credit ratings. For the analysis before and after 2009, when the Credit Information Use and Protection Act was strengthened after the global financial crisis, the coefficients of the capital expenditure ratio, cash ratio, and tangible asset ratio are significantly positive in the subsample for investment grades before 2009, but not significant after 2010. The coefficient of the long-term debt ratio is more significantly negative than that of the short-term debt ratio before 2009, for speculative grades, but short-term debt ratio has a more negative effect on ratings than long-term debt ratio after 2010. Surprisingly, the coefficient of the R&D expenditures is significantly negative in both investment and speculative grades since 2010. Our findings are inconsistent with the conjecture that the increase in R&D expenditures enhances the possibility of creating cash-flow by raising the investment growth opportunity, and thus affects positively the credit rating.

• Journal of Technology Innovation
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• v.23 no.1
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• pp.61-86
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• 2015

This study provides an empirical analysis based on 2012 Korea Innovation Survey (STEPI) to investigate the relation between R&D cooperation and in-house R&D investment. The study further analyzes the effect of the R&D cooperation and in-house R&D investment on technical innovation. First, the relation between company's in-house R&D investment and R&D cooperations is estimated with the two equations using SUR models. Second, the effect of in-house R&D investment and R&D cooperation on the company's technical innovation is estimated using Probit model. This study differs from other existing R&D studies using Korean data in that empirical models are based on structural relationships among in-house R&D, R&D cooperation, and technical innovation. The results can be summarized as follows; the R&D cooperation expands the in-house R&D investment and the in-house R&D strengthen the R&D cooperation. Furthermore, In-house R&D investment increases the chances of success in innovation. As we obtain evidence of complementary relation between R&D cooperation and in-house R&D investment, it is necessary to develop environment conducive to this complementarity in order to have more efficient R&D system.

• Environmental and Resource Economics Review
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• v.27 no.1
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• pp.139-160
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• 2018

Using survey data of selected 1,349 individuals nationwide in Korea, we measure the influencing factors for the acceptance of nuclear power and estimates the probability of acceptance under several scenarios with different percentages of monetary compensation. Results of panel probit demonstrate that nuclear risk aversion tendency was found to be higher in case of female, younger age, past experience of extreme event such as an earthquake. However, the residents' residency nearby the nuclear power plant was not related to the risk-aversion tendency. In addition, we found that the nuclear acceptance is improved when the monetary compensation rate is increased. Although the policy demand intended to reduce GHG emissions in South Korea, the expansion of nuclear power is not be easy due to the occurrence of recent strong earthquakes because the risk attitude of an individual is influenced by subjective assessments formed through direct and indirect experiences of natural disasters such as an earthquake. Our results suggest that the opposition to construction of nuclear power plant is expected to be further intensified especially when combined with the experiences of threatening earthquakes. As a result, the debate and policy conflicts of nuclear power plants will consistently continue and large social costs are apparent for the acceptance of nuclear power plant.

• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.33-41
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• 2003

There exists high hazard when transporting LPG as well as using, storing, and producing. For small scale LPG consumer, retailers deliver LPG to customers via a truck loading many LPG cylinders. Suppose there occurred a accident during LPG cylinder transfer, this could result in serious damages to the life and properties in the near or neighbor of the accident spot. In this regard, we made a quantitative risk analysis to estimate the possible damages and the probability through the identification of accidents causes and the simulation of the possible scenario. In this study, we made the Excel & Visual Basic computer program to perform quantitative LPG accident analysis. The simulation showed the following results. In case of UVCE(Unconfined Vapor Cloud Explosion), the effect within l0m of the accident spot showed very severe structural damages and even the accident can break the window glasses of the area of 150 m apart from accident spot. In case of TNT corresponding probit analysis, after 10 minutes LPG leaking, $75\%$ window glasses of 40 m distance was expected to be broken. And $16\%$ frames of 20m distance, $10\%$ frames of 40m distance was expected to be collapsed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.610-617
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• 2019

The urban-rural complex area in Korea has a distinctive spatial structure where the urban area and rural area coexist. Therefore, in order to cope with the over-depopulation in the rural region of the urban-rural complex area, it is necessary to explore various policies that can prevent the existing residents from leaving, and in fact support them to remain where they currently reside. In this context, this current study analyzed the factors affecting the existing residents' continuous intention to remain by employing the '2017 Chuncheon City Social Survey' as a countermeasure for the over-depopulation of the rural region in the urban-rural complex area. Especially, since a regional identity is determined endogenously, this study used a simultaneous bivariate ordered probit model with giving consideration to the endogenous relationship between a regional identity and a regional residents' intentions. As a result, it was found on analysis that the regional residential intention was higher as the regional identity was stronger. Furthermore, the regional identity was stronger as a householders' age and residence period were longer, and also as the residents were satisfied with their work leisure and life residence balance. It was also found that the residents' intention was higher as the residents' satisfaction with the local medical service and their work was increased. Thus, supporting policy is needed that can provide appropriate quality-of-life services in a timely manner, but only after identifying the demand for these services by the rural residents in the urban-rural complex area.

• Journal of Information Technology Applications and Management
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• v.18 no.4
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• pp.55-79
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• 2011

This study attempts to examine the factors affecting the introduction of e-Business systems and also, to assess the effects of various e-Business systems on firm performance. Empirical analysis is carried out with firm data of 2009, which is collected from Firm Activity Survey of Statistics Korea. Firm performance is measured by four indexes; operating income per employee, value added per employee, return on assets, and return on sales. Empirical results indicate that a firm is more likely to introduce any e-Business system as its size and its assets per employee are larger and as its ratio of labor compensations to operating costs is lower. Additionally, a firm with higher skill levels and more fruitful management experiences is more likely to have any e-Business system. In general, it appears that the presence of e-Business, especially enterprise resources planning, has positive effects on the firm performance.

• Journal of Labour Economics
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• v.32 no.1
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• pp.57-75
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• 2009

This paper provides empirical evidence on the impact of SCHIP (The State Children's Health Insurance Program) on single mothers' working decisions using recent CPS (Current Population Survey) data during 1999-2005. SCHIP are found to have a significant positive impact on hours-worked decision.

• Journal of Korean Society of Transportation
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• v.4 no.1
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• pp.72-87
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• 1986

본 연구의 목적은 주가로상 좌회전운전자의 문격수낙특성(gap-acceptance characteristics)을 파악하는 데 있다. 이 목적을 달성하기 위하여 포켓컴퓨터를 이용한 새로 운 자료수집기법이 개발되었다. 이 기법은 적은 비용으로 정확한 자료의 수집을 가능하게 하였다. 연구교차로는 마산시의 부도심에 위치한 2차선가로 및 4차선가로상의 전형적인 신 호등 비설치교차로가 선정되었다. 정규분포 및 대수정규분포가 probit분석을 이용하여 임계 수낙문격분포(critical acceptance gap distribution)로 검정되었다. 두 분포들은 5% 우의수준 에서 기각되지 않았다. 2차선가로의 임계수낙문격은 2.9∼3.0초의 범위였으며 표준편차는 1. 2∼1.5초의 범위였고, 4차선가로는 각각3.3∼3.4초와 1.3∼1.5초의 범위였다. 2차선가로의 임 계 lag는 2.6초였으며 4차선가로의 임계lag는 3.2초이었다. 국내 좌회전운전자의 임계수낙문 격이 미국인의 것에 비하여 짧은 것으로 나타났다. 이는 도시교통류의 주구성 차량이 직업 운전자들이 운전하는 소형 택시로 이루어지는 운전자 및 차량특성에 기인한 것으로 볼 수 있다.

• Journal of Agricultural Extension & Community Development
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• v.16 no.1
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• pp.201-235
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• 2009

This study analyzed the demographic characteristics, strengths and weaknesses related to information acquisition of local innovation diffusion types. This study use ordered probit model to find strengths and weaknesses of innovation diffusion type in rural area. The individual characteristics of 'formal extension type', 'situational reaction diffusion type', 'agriculturist connection type', and 'systematic approach type', all differentiated according to innovation diffusion type, were analyzed. Following Choi & Choe(2008), immediacy, accessibility, referability, applicability, and satisfaction were the highest in the situational reaction diffusion type, systematic approach type, formal extension type, and farmers connection type, in the order. And there existed organic contexts among individual characteristics. So this study tried to analyze strengths and weaknesses of innovation diffusion type with a focus on immediacy, which emerged as the most important variable in the process of interpreting innovation diffusion. And the strengths and weaknesses of each innovation diffusion type were presented.