• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.317-324
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• 2020

Combined cycle power plants (CCPP) that use natural gas as fuel are easier to start and stop, and have lower pollutant emissions, so their share of domestic power generation facilities is steadily increasing. However, CCPP have a high concentration of nitrogen dioxide (NO2) emission in the initial start-up and low-load operation region, which causes yellow plume and civil complaints. As a control technology, the yellow plume reduction system was developed and operated from the mid-2000s. However, this technology was unable to control the phenomenon due to insufficient preheating of the vaporization system for 10 to 20 minutes of the initial start-up. In this study, CFD analysis and demonstration tests were performed to derive a control technology by injecting a reducing agent directly into the gas turbine exhaust duct. CFD analysis was performed by classifying into 5 cases according to the exhaust gas condition. The RMS values of all cases were less than 15%, showing a good mixing. Based on this, the installation and testing of the demonstration facilities facilitated complete control of the yellow plume phenomenon in the initial start-up.

• New & Renewable Energy
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• v.7 no.3
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• pp.67-73
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• 2011

MGT fuelled by landfill gas was tested to asses feasibility of its exhaust gas application for $CO_2$ enrichment. The exhaust gas was analyzed during start-up and normal operation with different MGT load conditions. Due to the changes of air/fuel ratio and combustion mode, $O_2$, $CO_2$, CO and NOx concentration were varied within wide ranges during the MGT start-up. Especially, NOx emissioin level was increased up to 20.01 ppmv. Different tendencies of $O_2$, $CO_2$, CO and NOx concentrations were observed with MGT output changes. $O_2$ and CO concentrations were shown to be decreased and NOx and $CO_2$ concentrations were shown to have opposite trends. NOx emission level (0.8~1.88 ppmv) was very low compared to other types of combustion based power generation equipment. Unburned hydrocarbon emission level was substantially decreased with MGT load increase. Especially, $C_2H_4$ concentration was below the detection limit(0.2 ppmv) around the nominal load condition. The exhaust gas from landfill gas fuelled MGT system was shown to be feasible for $CO_2$ fertilization. Concentrations of major components were within or below the maximum allowable ranges.

• Korea Journal of Hospital Management
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• v.28 no.3
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• pp.68-86
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• 2023

Purpose: The purpose of this study is to explore the relationship between corporate entrepreneurship and organizational effectiveness among employees of medical institutions. In addition, we aim to investigate the mediating effect of motivation to participate in the In-house Innovation & Start-up Contest and the moderating effect of support from a dedicated organization. Methodology/Approach: A survey was conducted on participants in the 3rd in-house contest held in 2023 at Granum Sinapis Center of Seoul St. Mary's Hospital. A total of 122 people responded to the survey. The collected data were analyzed PLS-SEM(Partial Least Squares-Structural Equation Model) using SmartPLS 4.0 program. Findings: First, 'Corporate entrepreneurship' had an effect on 'Participation motivation in in-house contest'. Second, 'Corporate entrepreneurship' had an effect on 'Organizational Effectiveness'. Third, 'Participation motivation in in-house contest' mediated the relationship between 'Corporate entrepreneurship' and 'Organizational Effectiveness'. And last, 'Support from a dedicated organization' had no moderating effect on the relationship between 'Corporate entrepreneurship' and 'Organizational Effectiveness'. Practical Implications: Since the dedicated organization is in the early stages of operation, there may be no moderating effect on organizational effectiveness. If follow-up research is conducted after the dedicated organization's system has been supplemented, the moderating effect may appear differently.

• Journal of Korean Orthopaedic Sports Medicine
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• v.9 no.1
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• pp.65-68
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• 2010

Operative treatment including a bone graft and an internal fixation was done in a fifteen-year old wrestler with transverse olecranon stress fracture. At 6 weeks after the operation, he could start active muscle strengthening exercise and returned to the previous level of exercise at 6 monthes after surgery. Conservative treatment including resting and muscle strengthening exercise was performed in an eighteen-year old baseball player with oblique olecranon stress fracture. At the follow-up of three months, he could start staged throwing exercise without pain or tenderness. He returned the previous level of throwing following strengthening exercise for 6 months.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.465-474
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• 2010

Although the number of medium-length road tunnels, less than 1 km in length, has increased recently more than 30 percent each year, their ventilation and fire safety system design guidelines have not been established yet. The guidelines for long tunnel design are adopted even for the medium-length road tunnels. Therefore the necessity is brought up to optimize the ventilation and fire safety systems based on their own design guidelines. This study aims at determining the optimal start time of jet fan in case of 20 MW fires by analyzing smoke backlayering range, temperature distribution, range of poor visibility, evacuation time and critical velocity. The CFD study results are expected to contribute to propose the optimal fan operation mode.

• Journal of the Korea Society of Computer and Information
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• v.24 no.3
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• pp.29-39
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• 2019

In this study, we introduce a model that satisfies energy efficiency and economical efficiency by introducing and demonstrating cogeneration generators in industrial complexes using various actual data collected at the site. The proposed model is composed of three scenarios, ie, full - time operation, scenario operated according to demand, and a fusion type. In this study, the power generation profit and surplus thermal energy are measured according to the operation of the generator, and the thermal energy is traded according to the demand of the customer to calculate the profit and loss including the heat and evaluate the economic efficiency. As a result of the study, it is relatively profitable to reduce the generation of the generator under the condition that the electricity rate is low and the gas rate is high, while the basic charge is not increased. On the contrary, if the electricity rate is high and the gas rate is low, The more you start up, the more profit you can see. These results show that even a cogeneration power plant with a low economic efficiency due to a low "spark spread" has sufficient economic value if it can sell more than a certain amount of heat energy from a nearby customer and adjust the applied power through peak management.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.114-123
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• 2018

Recently, as one of the countermeasures to reduce carbon dioxide($CO_2$) for global warming problems, operation methods in micro-grid systems replacing diesel generator with renewable energy sources including wind power(WP) and photovoltaic(PV) system have been studied and presented in energetic manners. However, it is reported that some operation problems in micro-grid systems without diesel generator for carbon-free island are being occurred when large scaled WP systems are at start-up. To overcome these problems, this paper proposes an operation strategy in micro-grid systems by adapting control devices such as CVCF(constant voltage constant frequency) ESS(energy storage system) for constant frequency and voltage regulation, load control ESS for balancing demand and supply and SVC(static-var compensator) for reactive power compensation. From the simulation results based on the various operation scenarios, it is confirmed that the proposed operation strategy in micro-grid systems without diesel generators is a useful tool to perform a stable operation in micro-grid systems without diesel generator and also make a contribution to reduce carbon dioxide in micro-grid systems.

• Journal of Advanced Technology Convergence
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• v.2 no.2
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• pp.1-8
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• 2023

Due to the recent long-term economic downturn, the number of non-store and mail-order sellers is increasing as prospective entrepreneurs are concentrated due to the phenomenon of non-store start-ups with low start-up costs. In particular, in addition to unemployed young people and housewives who lack funds, many office workers who wish to have a 'two-job' are jumping into the business. Therefore, in this paper, we have moved away from provider-oriented service platforms that are dependent on specific networks, operators, and service types. In addition, we plan to design a business integration support system that can provide B2B services in the promotional material industry that contributes to business support and profit generation of wholesale and retail non-store entrepreneurs through sharing and participation. The proposed system is judged to be a business integrated operation support system applying orchestration and service management technology and enterprise business partner management technology that can provide stable operation management service.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.156-165
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• 1997

In the practical control systems, the dynamic range of actuatiors is limited(or saturated) when actuators are driven by sufficiently large signals. This gives rise to a nonlinearity as a result of actuator saturation. For example, the upper limit is imposed on productive capability by available factory space and capital equipment. Other examples of those kinds of actuator saturations are a maximum torque of the actua- ting motors and a throttle position in an aircraft speed control A saturating actuator may lead not only to a large overshoot during start-up and shut-down, but also to deterioration of the performance due to the uncertainties. That is, the speed of response is decreased and, possibly, the system output may not follow the lalrge reference inputs. The large-overshoot may be accompanied by rest wind-up(or called by integra- tor wind-up) which comes from controllers with integral action in saturation operation regions. Eventually, as the overshoot increases, the system has a limit cycle or becomes oscillatorily unstable. Due to these cir- cumstances, many studies are focused on the stability and robustness of the nonlinear systems with satu- rating actuator in the time-domain as well as in the frequency-domain.

• Asia-Pacific Journal of Business
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• v.14 no.3
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• pp.241-250
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• 2023

Purpose - The purpose of this study was to investigate the perception of 'unmanned cafes' on the network through big data analysis, and to identify the latest trends in rapidly changing consumer perception. Based on this, I would like to suggest that it can be used as basic data for the revitalization of unmanned cafes and differentiated marketing strategies. Design/methodology/approach - This study collected documents containing unmanned cafe keywords for about three years, and the data collected using text mining techniques were analyzed using methods such as keyword frequency analysis, centrality analysis, and keyword network analysis. Findings - First, the top 10 words with a high frequency of appearance were identified in the order of unmanned cafes, unmanned cafes, start-up, operation, coffee, time, coffee machine, franchise, and robot cafes. Second, visualization of the semantic network confirmed that the key keyword "unmanned cafe" was at the center of the keyword cluster. Research implications or Originality - Using big data to collect and analyze keywords with high web visibility, we tried to identify new issues or trends in unmanned cafe recognition, which consists of keywords related to start-ups, mainly deals with topics related to start-ups when unmanned cafes are mentioned on the network.