• Information and Communications Magazine
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• v.31 no.6
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• pp.3-11
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• 2014

Mobile operators today face yet another critical challenge as technology lifecycle becomes increasingly short and also as heterogeneous and complex network becomes exceedingly expensive and difficult to manage. With extremely competitive market and demanding users, the overall revenue structure is expected to get worse. A network architecture based on software-defined networking (SDN) and virtualization techniques gives operators greater opportunity to build cost-effective and efficient alternative to the legacy. In this work we review our Carrier Cloud as a future mobile network infrastructure that exploits both SDN and NFV in order to increase the operator agility, reduce the cost, and even disrupt the vendor landscape. This new architecture will not be fully adopted by the conservative operators at once. Technological hurdles have to be overcome, and a clear understanding of operational differences must be preceded.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.289-292
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• 2007

The flyback converter is one of the most attractive isolated converters in small power applications because of its simple structure. However, it suffers from high device stress, large transformer size, and high voltage stress across switch and diode. To solve these problems a new cost-effective PWM single-switch isolated converter is proposed. The proposed converter has no output filter inductor, reduced voltage stress on the secondary devices, and reduced transformer size. Moreover, the switch turnoff loss is reduced and no dissipative snubber across the secondary diode is required. Therefore, it features a simple structure, low cost, and high efficiency. The operational principle and characteristics of proposed converter are presented compared with flyback converter and verified experimentally.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.62-67
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• 2002

A single-phase power factor corrected converter for switched reluctance motor driving is presented to achieve sinusoidal, near unity power factor input currents. Because it combines a power factor corrected converter and a conventional asymmetric SRM driver into one power stage, the configuration has a simple structure resulted in low cost. A prototype to drive 6/6 poles SRM employing a parking magnet is designed to evaluate the proposed topology. The characteristics and operational mode will be discussed in depth, and the validity of proposed driver will be verified through the experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1138-1143
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• 2011

One of the critical items in radar testing is the ability to evaluate the performance of radar systems under real operational environments. But it takes lots of time and cost to operate real targets and analyze the test results due to a large amount of data based on these complicated environments. In this paper, the Radar Simulative T&E Lab. is introduced, and the test and analysis results of the developing radar for predicting the radar system performance are described in the Radar Simulative T&E Lab. This laboratory could be used to test the far-field characteristics of antenna radiation pattern and to perform an effective radar system test and evaluation using a simulative target generator under a low cost repeating test situation.

• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.170-178
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• 2011

In general, a software fault detection phenonenon is described by a software reliability model based on a nonhomogeneous Poisson process(NHPP). In this paper, we propose a software reliability growth model considering the differences of the software environments in both the testing phase and the operational phase. Also, we consider the problem of determining the optimal release time and the optimal warranty period that minimize the total expected software cost which takes account of periodic software maintenance(e.g. patch, update, etc). Finally, we analyze the sensitivity of the optimal release time and warranty period based on the fault data observed in the actual testing process.

• Journal of Applied Reliability
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• v.18 no.2
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• pp.184-191
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• 2018

Purpose: The purpose of this study is to propose a method to calculate the optimal preventive maintenance cycle of radar used in the aviation weapon system of ROKAF. Methods: A hybrid model is used to estimate the optimal preventive maintenance cycle in a system that can perform condition based predictive maintenance (CBPM) through continuous diagnosis. The failure data of the radars operating in the military were used to calculate the reliability. Results: According to the research results, the reliability threshold of the radar began to decrease after 5 flights, and decreased rapidly after 12 flights. Since the second check, costs have continued to decline. Conclusion: A method is proposed to determine the cycle of optimal preventive maintenance of radar within operational budget through modeling results between reliability limit and cost for radar. The results can be used to determine the optimal preventive maintenance cycle and frequency of various avionics equipment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.1
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• pp.61-73
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• 2021

PAV is considered to improve quality of life and standards of living, improvement of which was caused by automobile hundred years ago. Comparative economic efficiency of PAVs is measured to compare each PAV. Specification and sales price of the PAVs are open to the public. BlackFly, Transition and Aeromobil 3.0 have competitive power in flying range, purchasing cost, and operational cost. Lift & cruise configuration and vectored thrust configuration PAVs are designed by many companies nowadays, and BlackFly which can be considered to be lift & cruise configuration is one of the most efficient PAVs. High battery price does not help multi-copter shaped PAVs to have economic efficiency. Aerodynamic wing, eVTOL, and low sale price are needed for PAVs to ride a wave of public interest as a new personal mobility. Under the conditions, the PAV can fly at downtown and can be purchased by people at large. Popularization of PAV could follow in the 100 years old footsteps of automobile.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.45-51
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• 2023

During the operation of a nuclear power plant (NPP), the waste reactor vessel closure head (RVCH) that is replaced owing to design or manufacturing defects is buried in a designated area or temporarily stored in a radiation shielding facility within the NPP. In such cases, storing it for extended periods proves a challenge owing to space constraints in the power plant and a safety risk associated with radiation exposure; therefore, dismantling it quickly and safely is crucial. However, not much research has been done on the dismantling of the RVCH in an operational power plant. This study proposes a dismantling process based on the radioactive contamination level measured for the Kori #1 RVCH, which is currently being discarded and stored, and examines the decontamination and cutting according to this process. In addition, the amount of secondary waste and dismantling cost are evaluated, and the dismantling effect of the reactor closure head is analyzed.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.13 no.6
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• pp.143-154
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• 2018

This study is intended to look into the effects of SCM(supply chain management) competency and process improvement on operational performance in small and venture companies. To achieve this, a survey was empirically carried out to 179 small and venture manufacturing companies. The findings showed that the SCM competency had a significant effect on the process improvement and operational performance in small and venture companies, adopting all hypotheses. And the process improvement had a significant mediating effect on the relationship between SCM competency and operational performance in small and venture companies, adopting hypothesis 4. As for the findings, strategic alliance, technology development, competency concentration as SCM competencies and starting preparation, detailed planning, implementation management as process improvements were factors that have positive effects on quality performance, cost reduction and profit increase as operational performances in small and venture companies. In other words, the better process and performance by the maximized SCM competencies require selective input strategies for strategic alliance, technology development and competency concentration in small and venture companies. And for its early application and settlement, the starting preparation and detailed planning of business process within small and venture companies need to be jointly put in action under clear company-wide goal management. Consequently, the expected performance can be maximized when strict management and implementation lead to these attributes.

• Journal of Korean Academy of Nursing Administration
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• v.8 no.1
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• pp.123-135
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• 2002

Purpose: In this study, the critical pathway for laparoscopic cholecystectomy patients was developed and applied for clinical study. The effectiveness of the critical pathway was analyzed. Method: The subjects with no critical pathway services of this study were 30 laparoscopic cholecystectomy operation patients, who were hospitalized in B General Hospital in Busan from Nov. 28. 2000 to May 2. 2001. The subjects with critical pathway services of this study were 30 laparoscopic cholecystectomy operation patients, who were hospitalized in B General Hospital in Busan from June. 11. 2001 to Oct. 31. 2001. Results: 1. Development for critical pathway Preliminary critical pathway for the laparoscopic cholecystectomy patients was developed though analysis of the reference and 34 case of medical record. The items on the y-axis were assessment, test, treatment, diet, fluid, consult, medication, activity and education and the items on the x-axis were till 3days after operation. The developed critical pathway was applied in clinical field. 2.　Effectiveness of application on developed critical pathwayPost operational complication was not found in neither the critical pathway using Group nor Non-using Group. Hospitalization period mean was 4.63 days for the using Group and 5.93 days for the Non-using Group(P=.001). The mean cost for medical examination and treatment for the using Group was 786,270 won, 117,454 won(12.9%) less than that of the Non-using Group, 903,724 won(P=.000). The degree of satisfaction for the using group was 3.7 points, for the Non-using Group, 3.15 points. The degree of satisfaction for the used Group was 0.55 points higher than that for the Non-using Group and there was a statistically significant difference(P=.000). Concousion: From results of this study, Using the critical pathway in the laparoscopic cholecystectomy operational patients was effective in decreasing the hospitalization period and cost, and increasing the satisfaction about the medical service.