• Journal of Power Electronics
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• v.19 no.5
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• pp.1142-1152
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• 2019

This paper presents a control method for reducing the current distortion in an indirect matrix converter (IMC) operating in boost mode under unbalanced input conditions. IMCs operating in boost mode are useful in distributed generation (DG) systems. They are connected with renewable energy systems (RESs) and the grid to transmit the power generated by the RES. However, under unbalanced voltage conditions of the RES, which is connected with the input stage of the IMC operating in boost mode, the input-output currents are distorted. In particular, the output current distortions cause a ripple of the power, which is transferred to the grid. This aggravates the reliability and stability of the DG system. Therefore, in this paper, a control method using positive/negative sequence voltages and currents is proposed for reducing the current distortion of both side in IMCs operating in boost mode. Simulation and experimental results have been presented to validate effectiveness of the proposed control method.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.4
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• pp.149-154
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• 2018

Risk Based Oversight is a way of performing oversight, where planning is driven by the combination of risk profile and safety performance. Risk Based Oversight enables prioritization and allocation of State's safety management resources commensurate with the safety risk profile of each service provider. This paper presents the concept of Risk Based Oversight and applies it to the current Korean aviation safety oversight process. In particular, this study presents a method for generating operating profiles, one of the key concepts of Risk Based Oversight. Operations Specifications of Part 121 Airlines can generate operating profiles. In this study, a practical study was conducted to generate the operating profile and scoped DCTs using Part 121 Airlines's Operations Specifications.

• Journal of the Korea Safety Management & Science
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• v.23 no.4
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• pp.105-112
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• 2021

This paper presents a periodic replacement policy for a system subject to shocks when the system is operating for a finite random horizon. The system is subject to shocks during operation, and each shock causes downgrading of the system performance and makes it more expensive to run by the additional running cost. Shocks arrive according to a nonhomogeneous or a renewal process, and we develop periodic replacement policies under a finite random operating horizon. The optimum periodic replacement interval which minimizes the total operating cost during the horizon is found. Numerical examples are presented to demonstrate the results.

• The Korean Journal of Health Service Management
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• v.11 no.1
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• pp.1-9
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• 2017

Objectives : Cash Flows from operating activities is the most important part of the cash flow statement and it serves as an important financing source. Accordingly, the purpose of this study is to examine the influence of the contents of cash flows from operating activities on the changes in borrowings. Methods : In this study financial data from 2011 to 2014 were used to analyz 36 general hospitals and 85 hospitals according to the index displaying variation against the previous year. Results : For general hospitals, borrowings in cash flow from financing activities increased as net income decreased; while depreciation etc increased in cash flow from operating activities. For hospitals, borrowings in cash flow from financing activities increased as the gain on disposition of tangible assets in cash flow from operating activities decreased. Conclusions : General hospitals need to control the management of borrowings and depreciation at the level of funding management; whereas hospitals need to manage of future cash forecasts for stability of operational funds.

• Korea Journal of Hospital Management
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• v.11 no.3
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• pp.73-93
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• 2006

This study aims at providing necessary informations for management decision-making to the hospital manager, such as ratios of fixed and variable cost to total operating expense, and variable cost ratio to operating revenues, and determinant factors affecting cost behavior. A study model and related hypotheses were established, data were collected from 41 private university hospitals for the 6years from 1998 to 2003, and regression analyses were performed to test the hypotheses. The results of the analyses and conclusions are as follows; First, labor cost and administration cost within the same number of beds have not only fixed quality of the cost, but variable quality of that. Also, the ratio of the variable costs to operating revenue of the metropolitan was estimated 76.9% and that of other area hospitals was 80.1%. Second, the major factors affecting the increase rate of the operating expense were the increase rates of the number of inpatients, the number of employee, and the number of hospital operating bed. This result implies that maintaining a optimal hospital bed size and efficient operation of the beds are important strategic factors of hospital management.

• Research in Community and Public Health Nursing
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• v.16 no.3
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• pp.351-359
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• 2005

Purpose: To find the factors of subjective musculoskeletal symptoms associated with the general characteristics and tasks of operating room nurses (OR nurses) and then to use the factors as basic information for preventing and managing musculoskeletal symptoms in OR nurses. Method: This study was an exploratory research. Data were collected using a self-report questionnaire from OR nurses working at 8 polyclinics in Korea during the period from July 26 2004 to August 19 2004. The questionnaire contains 7 questions on general characteristics and 18 questions on tasks in the operating room. Result: 187 (75.1%) nurses said they 'had' subjective musculoskeletal symptoms. Statistically significant differences were observed according to clinical career, career as an OR nurse, skillfulness, satisfaction with tasks in the operating room, perception on suitable treatment, care of symptoms by the hospital. weight of hospital linen and weight of a basic operation set (p<.05). Conclusion: Musculoskeletal symptoms complained of by OR nurses were significant. This may cause difficulties in nursing tasks in the operating room. Thus, various arrangements should be made for OR nurse with subjective musculoskeletal symptoms at the early stage.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.3
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• pp.313-319
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• 2002

Since the oil crisis in 1970, a great deal of effort has been made to develop automatic electric load sharing systems as a part of the efforts to save energy. A large scale electric generating system composes more than two generators whose characteristics may be different. When such a system is operated individually or in parallel, the lagrange multiplier's method has difficulty in achieving optimal load distribution because generators usually have the limitations of the operating range with inequality constraints. Therefore, a suitable operating mode of generators has to be decided according to the selection of the generators to meet electric power requirements at the minimum cost. In this study, a method which solves the optimal electric load distribution problem using the dynamic programming technique is proposed. This study also shows that the dynamic programming method has an advantage in dealing with the optimal load distribution problem under the limitations of the operating range with inequality constraints including generator operation mode. In this study, generator operating cost curve of second order equation by shop trial test results of diesel generators are used. The results indicate that the proposed method can be applied to the ship's electric generating system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.12
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• pp.44-49
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• 2012

The earth leakage circuit-breakers installed to protect the human body against electrical shock have conventionally had a sensitivity current of 30 mA and an operating time of 30 ms or less. No reviews are found, however, on the operating time of the current conducting through the human body due to the electrical shock or ground fault. This paper measures the trip-operating time against the earth leakage under the condition of increased current as well as under the condition of rated sensitivity current of the earth leakage circuit-breakers. Further measurement with a prototype model showed an improved operating time of 16 ms or less under the condition of rated sensitivity current. It is expected that development of circuit-breakers with higher safety is possible if the performance of the electronic circuit can be improved.

• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.39-45
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• 2006

Fundamental informations on performance of sets of solenoid valve and nozzle were necessary to develop a target selectable spraying system. The experiments were performed for the sets of solenoid valves and flat spraying nozzles at 3 levels of the operating pressures, and the obtained results are as follows; Rise time of the system pressure to reach up to 90% of the operating pressure after the valve turned was affected by nozzle size and operating pressure. Maximum overshoot of the system pressure was about 170% not affected by the sets of valve and nozzle and operating pressure. The system pressure after its settle down within 5% of the set pressure showed good uniformity in any condition of the experiment as less as 2.3% of its coefficient of variation. Time requirement to lower the system pressure down to 50% after the valve power turned off was affected by valve and nozzle set and operating pressure.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.11a
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• pp.263-266
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• 2004

An experimental study was carried out on the recovery of ammonium lactate from simulated fermentation brothby desalting electrodialysis (DSED). All experiments, using AM-1 and CM-1 membranes, were operated in a constant current and a subsequent constant-voltage mode, and the switching point was determined based on the previous results. The effects of operating conditions such as operating current, initial feed concentration, and initial feed pH were investigated. Increased operating current resulted in a decreased operating time but an increased energy consumption per unit amount of ammonium lactate recovered. As the initial feed concentration was increased, the operating time increased while energy consumption decreased. The operating time and energy consumption slightly decreased as the initial feed pH was increased up to 6.0. However, no significant influences on the recovery of ammonium lactate were observed over 6.0. The rejections of acetate, glucose, and proteins were $10\%,\;93\%,\;and\;98\%$, respectively. Sulfate was not rejected at all.