• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.213-217
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• 2017

Since more than 30% of the liquid rocket engine failures occur during the start-up process, and the Space Shuttle Main Engine (SSME) is especially sensitive to small changes in propellant conditions, a 2% error in the valve position or a 0.1sec timing error could lead to significant damage of the engine, simulation modeling of start-up process is important. However, there are many difficulties associated with engine start-up process caused by nonlinear mass flow and heat transfer characteristics associated with filling an unconditioned engine system with cryogenic propellants. In this paper, we modelled a SSME simulation model using partially Computational Fluid Dynamics (CFD) method to solve these problems and checked the performance by comparing with the performance of the simulation model using the lumped method under the state of normal condition.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.533-539
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• 2016

This study was performed to evaluate the characteristics of start-up of anaerobic digestion from food waste with different inoculum ratios. The hydrogen yield was similar with different inoculum ratios. The hydrogen production rate increased with increasing inoculum ratio. But the specific hydrogen production rate decreased with increasing inoculum ratio. Total volatile fatty acids composition analysis showed that butyrate and acetate were the prevalent products in all reactors, followed by lactate and propionate. The acetate was most prevalent product in reactors at $X_0/S_0=0.080$ and 0.159. But in reactors at $X_0/S_0=0.239$ and 0.318, butyrate accounted for greater than 50% of the total volatile fatty acids.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.1
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• pp.38-43
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• 2011

This paper presents the improvement of start-up characteristic of sensorless controlled IPMSM(Interior Permanent Magnet Synchronous Motor) with SMO(Sliding Mode Observer). It is difficult to utilize the rotor position information at starting point for the back EMF estimation based sensorless control. For this reason, open loop control is normally used during start-up period. However, changing from open loop to closed loop control might bring a problem on the transient characteristics for difference load conditions. To solve this problem, we add another rotor angle controller. Simulation results and experimental results are presented to verify proposed method.

• International Journal of Highway Engineering
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• v.19 no.4
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• pp.69-78
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• 2017

PURPOSES : In this study, we analyzed the road crossing behavior of older pedestrians on a mid-block signalized crosswalk, and compared it to that of younger pedestrians. In addition, we analyzed the correlation between accidents involving older pedestrians while crossing roads and their behavioral characteristics. Finally, we confirmed the reasons for an increase in accidents involving older pedestrians. METHODS : First, 30 areas with the highest incidence of accidents involving older pedestrians while crossing roads were selected as target areas for analysis. Next, we measured the start-up delay (the time elapsed from the moment the signal turns green to the moment the pedestrian starts walking) and head movement (the number of head turns during crossing a road) of 900 (450 older and 450 younger) pedestrians. The next step was to conduct a survey and confirm the differences in judgment between older and younger pedestrians about approaching vehicles. Finally, we analyzed the correlation between the survey results and traffic accidents. RESULTS : The average start-up delay and head movement of the older pedestrians was 1.58 seconds and 3.15 times, respectively. A definite correlation was obtained between head movement and the frequency of pedestrian traffic accidents. The results of our survey indicate that 17.3% of the older pedestrians and 7.8% of the younger pedestrians have a high crash risk. CONCLUSIONS : Behavioral characteristics of older pedestrians were closely correlated with accidents involving older pedestrians while crossing roads in mid-block signalized crosswalks. Our study indicates that in order to reduce the number of accidents involving older pedestrians, it is necessary to develop an improvement plan including measures such as installation of safety facilities taking the behavioral characteristics of older pedestrians into consideration and their safety education.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• The Journal of Sustainable Design and Educational Environment Research
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• v.20 no.4
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• pp.13-20
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• 2021

In the world, each country is preparing various policies to promote start-ups, and the Korean government is actively promoting policies to support start-ups and the national economy through technology-based start-ups for creating jobs. Recently, the number of start-up companies is on the rise. In particular, in accordance with the industrial structure transformation leading the 4th Industrial Revolution, technology-based start-ups are steadily growing based on knowledge-based services such as information and communication, science and technology service industry, and business support service industry. The purpose of this study is to find out whether the startup space provided by the university reflects the startup-friendly characteristics, and to investigate and analyze the satisfaction and requirements of the space required by the actual college campus startup space users to create a more efficient space configuration plan. Through this study, factors that should be considered first for universities in preparing startup spaces were derived for each space element. Therefore, it is necessary for university campuses to deeply recognize the importance of space provision among the future start-up support systems, and to improve them periodically through the consumers' satisfaction of the space in the construction and improvement of startup spaces.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.233-247
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• 2011

With recent increase in growth without employment and unemployment rate, Business Incubator (BI), which is the birthplace of business start-up, is drawing much attention. Therefore, numerous studies had been carried out from the perspectives of efficient operation and performances of BI. Preceding studies at home and abroad were concentrated mainly on the effect of Critical Success Factors of BI on performance, or on internal operational programs or support services of BI. Recently, assertion that potential capacity of companies located in BI at the time of their commencement of occupancy imparts effect on the performance has been presented. Therefore, this Study, in order to pursue research on above issues, will, firstly, analyze the effect of the characteristics of evaluation of companies wishing to be located in BI conducted by each BI, and, secondly, regulation effect of characteristics of evaluation of companies wishing to be located in BI imparted on performance in connection with the work capabilities of BI and capabilities of manager. The results of analysis illustrated that the expertise, among the capabilities of CEO, imparts affirmative effect on the success rate of business start-up. Product competitiveness and marketability displayed affirmative effect on the success rate of business start-up when work capability (operational intensity) is applied. In particular, although the financing capability of CEO of the company located in BI, as an important factor, imparts negative effect on the success rate of business start-up, it implies affirmative regulation effect through the capabilities of manager.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.13 no.6
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• pp.15-25
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• 2018

As jobless growth became the new norm and the average life expectancy continues to increase, it is difficult to find quality jobs regardless of gender. In this situation, entrepreneurs who can take charge of creating quality jobs have begun to gain attention from governments. As a result, many startup support programs have been introduced and operated. In Korea, various government-sponsored startup support programs have been in operation since the late 2000s, and the number of startups has increased since. However, there are many cases where they are not able to maintain their business for a long time because such programs often lack expertise and experience. Mentoring programs for startup founders is becoming an attractive solution to these problems. However, when we look at the responses of entrepreneurs, they found the mentoring program beneficial only when it was well planned and operated. Otherwise, they found the program unhelpful. Although there are many startup mentoring programs in various fields, there is little research on whether customized mentoring that matches the characteristics of startups and entrepreneurs are effective. In this study, we study the effects of startup mentoring on mentoring satisfaction. Our model also intends to identify the moderating effects of entrepreneurs' characteristics and provide guidance to future startup mentoring.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.8 no.2
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• pp.47-52
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• 2013

The identification of the entrepreneurs' capacity and the obstacles of university/graduate school students have been assuming a growing importance in the development of mentoring directed towards the entrepreneurship and start-up processes. This study aims to identify the factors that most contribute for the intention to start up a business. The research also tries to identify the profile of a potential entrepreneur student concerning several characteristics: entrepreneurial capacity, obstacles and mentoring. We used the modeling testing of the data collected from 139 university/graduate school students. Research findings include the idea that entrepreneurial mentoring is moderating effect on entrepreneurial intention. On the other side, personal entrepreneurial capacity has an important role in shaping motivation to start-up a business and entrepreneurial obstacle have a negative impact in the intention to start-up. Contribution and suggestions are provided for the further research.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.103-114
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• 2012

The study is analyzed that policy support impact on youth entrepreneurship and to purpose enhancing the effectiveness of the policy support, would like to empirical study on support performance by start-up support program through education level of the founder, performance of the establishment enterprises and an empirical study of start-up support. This study reported that start-up support should be different from impact of performance of support by young founder to participate in the success of entrepreneurship incubator package or preliminary young founders and is focused on study of policy support. Examines the literature of associated young founder's characteristics and entrepreneurship support policies at domestic and foreign, and the government's support policies in order to achieve the purpose of this study, survey research as the basis of the model was set. This study surveyed to university student which were trained nationwide entrepreneurship program in order to validate the research model. The survey targeted engineering students who is practical technology foundation possible during from June 1, 2012 to June. 15, 2012, the way of data collection was directly surveryed to engineering students who participated in the entrepreneurship program. and an empirical analysis were collected each 157 call.