• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.6 no.1
• /
• pp.43-49
• /
• 2010

The piping failure probability of the reactor coolant system in Kori unit 1 was evaluated considering stress corrosion cracking. The P-PIE program (Probabilistic Piping Integrity Evaluation Program) developed in this study was used in the analysis. The effect of some variables such as oxygen concentration during start up and steady state operation, and operating temperature, which are related with stress corrosion cracking, on the piping failure probabilities was investigated. The effects of leak detection capability, the size of big leak, piping loops, and reactor types on the piping failure probability were also investigated. The results show that (1) LOCA (loss of coolant accident) probability of Kori unit 1 is extremely low, (2) leak probability is sensitive to oxygen concentration during steady state operation and operating temperature, while not sensitive to the oxygen concentration during start up, and (3) the piping thickness and operating temperature play important roles in the leak probabilities of the cold leg in 4 reactor types having same inner diameter.

• Journal of Power Electronics
• /
• v.5 no.3
• /
• pp.240-246
• /
• 2005

Considering the start-up and economical efficiency, the optical sensor technique using a slotted-disk and an opto-interrupter are appropriate, however, this method needs three opto-interrupters and a slotted-disk when driving the 6/4 pole SRM(switched reluctance motor). In this paper, we propose an economic method by replacing the conventional opto-interrupter and slotted-disk with only optical sensor which enables the motor to start up and forward and reverse operation. Also the control circuit includes only analog devices, which makes the process more economical.

• Tribology and Lubricants
• /
• v.15 no.1
• /
• pp.108-115
• /
• 1999

The electrical and frictional properties of oil-impregnated sintered-metal bearing (OSB) and herringbone-grooved fluid bearing (HFB) with varying loads and speeds were measured. OSB shows very good performance up to 20,000 rpm and 0.05 N, and HFB successfully works up to 35,000 rpm and 0.05 N. From the endurance tests on start-stop and continuous operation, it was confirmed that those bearings could be mass-produced fur use on scanner motor in a laser scanner unit.

• Journal of Magnetics
• /
• v.20 no.2
• /
• pp.176-185
• /
• 2015

We present the design optimization of the magnetic pole and slot design options that minimize the cogging torque of permanent-magnet (PM) brushless generators for small wind turbine generators. Most small wind-turbines use direct-driven PM generators which have the characteristics of low speed and high efficiency. Small wind-turbines are usually self-starting and require very simple controls. The cogging torque is an inherent characteristic of PM generators, and is mainly caused by the generator's geometry. The inherent the cogging torque can cause problems during turbine start-up and cut-in in order to start softly and to run a power generator even when there is little wind power during turbine start-up. Thus, to improve the operation of small turbines, it is important to minimize the cogging torque. To determine the effects of the cogging torque reductions, we adjust the slot opening width, slot skewing, mounting method of magnets, magnet shape, and the opening and combinations of different numbers of slots per pole. Of these different methods, we combine the methods and optimized the design variables for the most significant design options affecting the cogging torque. Finally, we apply to the target design model and compare FEA simulation and measured results to validate the design optimization.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.15 no.5
• /
• pp.261-276
• /
• 2020

This study seeks to find an effective support plan through the success factors recognized in the early stages of startup and those recognized after success by grasping the success factors of successful small business entrepreneurs at each stage from the pre-start stage to the growth stage. To this end, a qualitative study through interviews was conducted with successful convenience store franchisees to derive success factors from the start-up preparation stage to the early stage and growth stage. The success factors of starting a small business were studied in consideration of the characteristics of franchise convenience store startups using the ERI model and the ERIS model applied in the study on the performance of startups. The success factors were studied using the multisite service firm life cycle of Sasser et al.(1978) reflecting the results. As a result of the study, the key factors of successful franchisees were the selection of the location of the first store, the selection of strategic additional stores, and the successful renewal of the contract. Depending on the characteristics of the founder, the enterprising franchisees took an active attitude in selecting strategic locations for additional stores and defending the commercial district, while the relatively conservative franchisees showed an active attitude toward store operation and renewal from a management perspective. In particular, the entrepreneur's mind is important in the preparation stage, and the importance of the entrepreneur's management strategy was discovered in the entire business cycle. Based on the results of this study, this study specifically sought out a start-up plan to effectively apply it to the future growth stage.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.3
• /
• pp.1-8
• /
• 2016

It was examined that start-up characteristics of a staged combustion cycle engine powerpack. Among various parameters, valve opening time was considered as a main factor affecting the start-up characteristics. Using monte-carlo method, characteristics variation was analyzed when the valve opening time deviates from the nominal value. As a result, the main fuel valve opening time and the start turbine ending time were significant associated with the startup characteristics. When separating main fuel valve opening time and start turbine stop time, main fuel valve opening time was an important factor. For stable operation, the main fuel valve opening time must be set one second before after driving the start turbine. Likewise, it was confirmed that the startup analysis can suggest an appropriate startup sequence for a stable startup.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.6
• /
• pp.53-60
• /
• 2011

The effect of exhaust heat recovery system can be evaluated by two well known method. First method is to measure the time duration from engine start under cold coolant temperature till coolant get warmed. By this methodology coolant warming duration can be index of warm-up effect. Second method is to analyze heat balance of the engine during warm-up phase under steady engine operation so that wasted energy by losses such as cooling and exhaust can be index of warm-up effect. This study focused on evaluation of warming-up effect by both methodology above mentioned using 2L SI engine under from idle to 2000rpm steady condition. Results, idle operation showed low heat recovery efficiency but under higher engine speed condition, remarkable heat recovery efficiency improvement was observed. In 2000rpm steady condition, warm-up duration of engine is decreased by exhaust heat recovery system.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.9 no.4
• /
• pp.1-12
• /
• 2014

It is essential factor for business operation to raise funds effectively. However, in Korea, many start-ups and small businesses have difficulties in fund-raising. In recent years, crowdfunding, a new method for funding a project of individuals or organizations by raising monetary contributions from a large number of people, has been growing up simultaneously with diffusion of social media. Crowdfunding is on early stage in Korea, and the majority of projects are focused on cultural or art categories. There is high proportion of projects that have social value in start-up sector. Crowdfunding in Korea has great potential because success rate of it is much higher than its of advanced countries, although market size is much smaller than them. The purpose of this paper is to propose success strategies of crowdfunding for start-up through case study. 5 crowdfunding platforms of Korea and Kickstarter, the platform of United States were investigated. Then we checked the figures related to the operation of the whole Korean projects on start-up. Finally, we made comparison between the cases of success and failure by analyzing 8 project characteristics. The study shows that it were the differences in trustworthiness and activeness of project creator, value of reward and efforts for interactivity that have great effects on success of the project. Whereas there was no significant influence of societal contribution and sponsor engagement. The thesis provides success strategies of crowdfunding for start-up as follows. Firstly, creator of the project should make support base by enthusiastic activites before launching funding project. Secondly, there should be contents that can easily show the process of business development in the project information. Thirdly, there must be appropriate design of rewards for each amounts of support money. Finally, efforts for interactivity, such as frequent updates, response for comments and SNS posting, should be followed after the launch of the project.

• Journal of the Korean Institute of Gas
• /
• v.11 no.3
• /
• pp.40-43
• /
• 2007

The performance of PEMFC stack can be improved significantly by optimizing the design and operating conditions. As a result, the performance of daily operation showed slight deviation (0.02-0.9%) after accumulated DSS operation for 500 hrs but the stack performance was stable. Therefore, it is confirmed that it would be improved the life-time of stack and operation reliability for the commercialization of PEMFC system.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.11 no.5
• /
• pp.129-139
• /
• 2016

In this study, we analyzed the effect of entrepreneurial spirit of the start-up real estate founder gives to management achievements, founding education and it was confirmed whether they have a regulatory effect between them. For this reason, we conducted a questionnaire survey of real estate founder of start-up, were analyzed using the SPSS 18.ok. To summarize the research results are as follows. First of all, prefer achieve desire and venture start-up founder, it has become a direction of a significant and positive and management achievements of the dependent variable (+). This can be seen to affect the establishment go management achievements prefer to achieve desire is higher or of the venture. Second, the satisfaction of the business with the contents of the management achievements, may be mentioned whether the business recommendation, factors of these management achievements, each of the major contents of the management outcomes can be seen as an impact to some extent. While factors of independent variables were clearly private that there is a difference on the basis of its founding education as an adjustment variable in relation to the impact on business performance, some the only adjustment variables, such as whether to recommend satisfaction and business of business it was confirmed that shown. In this study, which provide us with the knowledge of information that can be derived to provide the basic information of implementation and policy-making that it is possible to promote the success activation of the start-up real estate in the successful establishment and operation of the business It is expected.