• Transactions of the Korean Society of Mechanical Engineers B
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• 제28권7호
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• pp.826-833
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• 2004

Cascade impactors are widely used to collect size classified aerosol. A major disadvantage of this instrument is the required long sampling time. Electrical low pressure impactor has been developed to overcome this disadvantage and to achieve real-time measurements on the particle size distribution. The instrument consists primarily of a corona charger, low pressure cascade impactor and multi channel electrometer. We designed and evaluated the performance of a potable 3-stage low pressure impactor using an electrical method. For the calibration of the impactor, monodispersed particles were generated using evaporation-condensation method followed by electrostatic classification using a DMA(Differential Mobility Analyzer). The collection efficiency curves of the stages can be determined by analysing the fraction of particles collected by each stage.

• Journal of Drive and Control
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• 제18권3호
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• pp.8-15
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• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• Journal of Navigation and Port Research
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• 제40권3호
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• pp.139-146
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• 2016

Due to the continuous increasement of the container cargoes, each container port market has been growing as well. Moreover, the competition among container terminal operators located in the same port is also growing in order to attract more container cargoes. This paper looked into the market structures, market conducts and market performances of container ports in Busan and Shanghai. The index which has been most widely used to measure market structure, the Hirschman-Herfindahl Index (HHI), is computed by squaring each supplier's market share, then adding the squared shares. This paper estimated the market performance as profitability (PCM, ROA), growth (total TEU, rate of the increasement of TEU) and examined the effects of the HHI on the profitability and growth in a container terminal operators in Korea and China. The major findings of this study is that the market structure has effects on market performance in Busan port (total TEU) and Shanghai port (PCM, ROA and total TEU). As a result of analysing this study, market structure has an effect on market performance in Busan and Shanghai port, but the power of influence can be changed by market concentration index and various market conduct of companies.

• Journal of Korean Society of Transportation
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• 제19권6호
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• pp.131-142
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• 2001

Previous OD matrix estimation methods from link traffic counts have focused on the formulation of mathematical model and its solution algorithm. Thereby those methods have assumed that true or real OD is similar to the target OD and paid little attention to the properties of the change of OD structure. Although it is general situation that each OD pair increases or decreases due to significant land use and to large time variation between target OD with real OD, those methods have set unrealistic assumptions that target OD increases or decreases uniformly and that the OD structure does not change. Therefore those methods have showed poor performance of OD estimation in general situation. To cope with the problem. this paper suggests a new concept of OD matrix structure and shows the shortcomings of previous method′s dependancy on target OD matrix. We divide "OD trips" into "OD scale" and "OD structure". Where OD scale is a quantitative magnitude of OD trips and "OD structure" is ordinal OD scale. This paper use the same solution algorithm developed by Baek et al. (2000) for analysing the OD structure. Results of numerical examples show that the performance of the method is better than that of previous methods, while the previous methods have better performance in estimation only when OD trips increase or decrease. In addition to, if OD structure does not change, the results show that the error of estimation is low relatively regardless of the large difference of trips between target OD and real OD. This paper also shows that the model performance on OD structure and on OD trips is low as the number of origins that OD structure is changed increase. From the results we suggest that the change of OD structure can be more important information than the difference between target OD and real OD in OD estimation steps.

• Journal of Regulation Studies
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• 제27권1호
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• pp.63-91
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• 2018

This paper attempts to explore the impact of technological regulation on technological innovation and performance of Small and Medium Enterprises(SMEs) by analysing a survey data of 286 Korean SMEs. The 3-step mediated regression analysis results reveal that the perceived regulatory burden is negatively associated with SMEs' R&D investment and innovation of product and process. Moreover, the level of regulatory burden may affect the objective and subjective performance of SMEs. The results suggest that regulatory policies for reducing regulatory burden need to be designed and implemented in order to enhance technological innovation and performance of SMEs.

• Journal of Distribution Science
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• 제14권2호
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• pp.93-101
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• 2016

Purpose - This study aims to advance our knowledge about factors influencing technical startup performance through analysing technical startup process empirically. This study was conducted to focus on industry structure(industry growth rate, competitive intensity, and enter barriers), technology characteristics(technical excellence and wide range of technical application), and the performance in the technology-based start-ups. Specifically, analyzing moderating effect of technology-marketing strategy, this studied how moderating variables affect technical startup performance under industry structure. Research design, data, and methodology - The subject of this study was technology-based start-ups company that received technology transfer from public organization. The development of the paper model is based on the literature of the preceding research analysis in technology commercialization, performance of technology-based start-ups, and marketing strategy. This study has a construct that was defined in the previous studies, such that technology marketing strategy was defined into the two ways of being broad or narrow in strategic application. From November 3. 2015 to December 22, 220 questionnaires were distributed with targeting to start-up companies in technology-based. 188 responses were collected for empirical analysis except the missing and wrong value responses. This data were used for structural equation modeling and regression analysis. Results - The results of this study are as follows. First, as industry structure variables influencing on performance(technical, financial) of technology-based start-ups, industry growth rate, competitive intensity and enter barriers of variables were verified; high growth rate has more positive effect on performance than low growth rate, competitive low intensity has more positive effect on performance than competitive high intensity, low enter barriers have more positive effect on performance than high enter barriers. Second, as technology characteristics variables influences on the performance(technical, financial) of technology-based start-ups, technical excellence and wide range of technical application of variables were verified ; technical high-excellence has more positive effect on performance than technology low-excellence, wide range of technical application has more positive effect on performance than narrow range of technical application. We also find that technology marketing strategy(broad/narrow) in moderating factors on performance (technical, financial) is as follows. Analyzing the moderating effect depending on technology marketing strategy(broad/narrow), application of technology, and the types of technology strategy(broad/narrow) were revealed that broad marketing strategy had a more significant effect on performance of technology-based start-ups. With AMOS, the relevancy of the study model revealed higher for broad technology-marketing strategy than narrow technology marketing strategy, and the explanatory power revealed to be 6.4% higher in broad marketing strategy than narrow marketing strategy. Conclusions - This study confirmed that industry structure and technology characteristics are important factors influencing the performance of technology-based start-ups. Technology-marketing strategy affects the performance of technology-based start-ups between industry structure and technology characteristics. According to additional analysis, moderating variables and technology-marketing strategy are important factors influencing the performance of technology-based start-ups under industry structure and technology characteristics. Broad type of technology-marketing strategy has more attractive industry structure and excellent technology characteristics than narrow types of technology-marketing.

• Journal of Korea Technology Innovation Society
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• 제16권3호
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• pp.724-753
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• 2013

This paper empirically examines the effects of green technology patent on the financial performance of SMEs and venture specialized green enterprises. In particular, this paper is focused on analysing the financial performance difference by comparing the financial condition of 1st year before and 1st year after the application of green technology patent, and the one of 1st year before and 2nd year after it using sales, operating profit, net income, ratio of operating profit to net sales, and ratio of net profit to net sales. The statistical significances were accepted on sales after 1st and 2nd year, operating profit and ratio of net profit to net sales after 1st year, and ratio of operating profit to net sales after 2nd year. This paper proposes the vitalization of green consumption market, the reinforcement of green financial policy, the installation of financing windows, the improvement of unfair business conducts of large enterprises, and the reinforcement of win-win partnership between large enterpsises and SMEs as policy issues of Korean government in order to promote SMEs and venture specialized green enterprises.

• Journal of Korea Society of Industrial Information Systems
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• 제17권7호
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• pp.177-186
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• 2012

Social Network Service is a web-based service that allows the people to construct relationship among users with same interest and supports various activities such as managing personal relations and sharing information or contents. The objective of this study is analysing the influence of the innovativeness on the use intention in SNS based on the UTAUT model. This study establishes a theoretical model that includes four independent variables(performance expectancy, effort expendancy, social influence, innovativeness) and two moderating variables(gender and innovativeness). The empirical results obtained in a sample of 403 university students are followings; 1) The use intention is positively influenced by the performance expectancy, effort expendancy, social influence and innovativeness. The effort expectancy is the strongest predictor of the use intention 2) The gender has a moderating effect whileas the innovativeness has no moderating effect. For men, the stronger the effect of performance expectancy on the use intention and for women, the stronger the effect of social influence on the use intention.

• Journal of Information Technology Applications and Management
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• 제16권4호
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• pp.205-222
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• 2009

Considering time-lag in the performance evaluation of information system (IS) investment is important because its effect reveals after certain period of time passed. Particularly it is more in the systems of e-government informatization projects which the amount of investment and the scale of business are huge. Many methods to solve this issue have been proposed such as system dynamics methods, simulations, structural equations etc. However, it is still difficult and unsolved problem because collecting practical data for time-lag analysis is very hard. In this paper, we analyze IS time-lag effect through factor analysis using the accumulated practical operational DB data. For the performance evaluation of the G4C system, the representative e-government web portal, we selected eleven factors reflecting time passing in G4C DB data. With these factors this paper conduct time-lag analysis in four view points. First, we conducted 'Stabilizing of G4C system' and got a result that IS is needed about three years for the stabilization. Second, we conducted 'Utilization of G4C system' and got a result that the utilization reaches appropriate level after in three years later after the introduction of G4C system. Third, we conducted 'Cost reduction effect' and got a result that cost reduction is stable in the third year after the introduction of G4C system. Lastly, we conducted 'System maturity effect' and got a result that the system reaches to the quality level that users expect after third to fourth years. According to the results of this research, we found that performance of IS improv continuously not immediately, and it needs three or four years of time-lag.

• Aerospace Engineering and Technology
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• 제1권1호
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• pp.147-152
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• 2002

In the preceding tests of Sub.(Ⅰ) engines, it was observed that the heat resistant capability of the engines was not enough, and the design of Sub.(Ⅰ) engines was modified to satisfy the mission requirement. Sub.(Ⅰ) Mod. engines have three major design parameters - the arrangement of main injectors, the impinging angle of main injectors and thermal barrier coating. More than 20 experiments were carried out to evaluate engine performance and heat resistance capability with respect to design parameters. Analysing the result of Sub.(Ⅰ) and Sub.(Ⅰ) Mod. engine tests, it is found that the decreased impinging angle, adopting the H-type arrangement(rather than radial type arrangement), and adopting the thermal barrier coating can increase heat resistance capacity substantially. The result show that the performance variation by design change is below 5 percents and the radial type arrangement of injectors has higher performance than H-type. However, the performance of 15°impinging angle engine is higher than that of 20°impinging angle engine, which is inconsistent to our expectation. High frequency instabilities may cause such phenomenon, which will be verified by a series of tests.