• The KSFM Journal of Fluid Machinery
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• v.18 no.2
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• pp.60-66
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• 2015

Conjugate heat transfer analysis was performed to investigate the flow and cooling performance of the high pressure turbine nozzle of gas turbine engine. The CHT code was verified by comparison between CFD results and experimental results of C3X vane. The combination of k-${\omega}$ based SST turbulence model and transition model was used to solve the flow and thermal field of the fluid zone and the material property of CMSX-4 was applied to the solid zone. The turbine nozzle has two internal cooling channels and each channel has a complex cooling configurations, such as the film cooling, jet impingement, pedestal and rib turbulator. The parabolic temperature profile was given to the inlet condition of the nozzle to simulate the combustor exit condition. The flow characteristics were analyzed by comparing with uncooled nozzle vane. The Mach number around the vane increased due to the increase of coolant mass flow flowed in the main flow passage. The maximum cooling effectiveness (91 %) at the vane surface is located in the middle of pressure side which is effected by the film cooling and the rib turbulrator. The region of the minimum cooling effectiveness (44.8 %) was positioned at the leading edge. And the results show that the TBC layer increases the average cooling effectiveness up to 18 %.

• The korean journal of orthodontics
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• v.52 no.3
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• pp.220-235
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• 2022

Objective: To evaluate the available evidence regarding the clinical effectiveness of different types of anchorage devices. Methods: A comprehensive literature search of different electronic databases was conducted for systematic reviews investigating different anchorage methods published up to April 15, 2021. Any ongoing systematic reviews were searched using PROSPERO, and a grey literature search was undertaken using Google Scholar and OpenGrey. No language restriction was applied. Screening, quality assessment, and data extraction were performed independently by two authors. Information was categorized and narratively synthesized for the key findings from moderate- and high-quality reviews. Results: Fourteen systematic reviews were included (11 were of moderate/high quality). Skeletal anchorage with miniscrews was associated with less anchorage loss (and sometimes with anchorage gain). Similarly, skeletal anchorage was more effective in retracting anterior teeth and intruding incisors and molars, resulting in minor vertical skeletal changes and improvements in the soft tissue profile. However, insufficient evidence was obtained for the preference of any anchorage method in terms of the duration of treatment, number of appointments, quality of treatment, patient perception, or adverse effects. The effectiveness of skeletal anchorage can be enhanced when: directly loaded, used in the mandible rather than the maxilla, used buccally rather than palatally, using dual rather than single miniscrews, used for en-masse retraction, and in adults. Conclusions: The level of evidence regarding anchorage effectiveness is moderate. Nevertheless, compared to conventional anchorage, skeletal anchorage can be used with more anchorage preservation. Further high-quality randomized clinical trials are required to confirm these findings.

• Journal of the Korean Society of School Health
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• v.33 no.1
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• pp.19-27
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• 2020

Purpose: This study is to confirm the effectiveness of the character education program applied to high school students. Methods: The study used a one-group pretest-posttest design with a sample of students aged 15 (n=263, male), the members of eleven 10th grade classes in a high school in Seoul, from March 1st, 2019 to February 28th, 2020. In order to confirm the effectiveness of the program, the Korean Educational Development Institute (KEDI) character questionnaire was used, and a paired t-test was performed using IBM SPSS statistics 25 statistical program. Results: In this study, character levels were significantly higher after the character education program than before. The pre-post differences in character levels were measured for Sincerity (t=5.63, p<.001), Self-respect (t=2.78, p=.011), Decorum (t=3.97, p<.001), Responsibility (t=5.35, p<.001), Consideration and communication (t=5.89, p<.001), Citizenship (t=5.28, p=p<.001), Self-regulation (t=6.25, p<.001), Justice (t=2.62, p=.011), Wisdom (t=5.75, p<.001), and Honesty and courage (t=7.11, p<.001). Conclusion: In this study, and were found to be significantly related to improvements in character.

• Journal of applied mathematics & informatics
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• v.31 no.3_4
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• pp.577-594
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• 2013

In this paper, we study the global stability and the existence of almost periodic solution of high-order Hopfield neural networks with distributed delays of neutral type. Some sufficient conditions are obtained for the existence, uniqueness and global exponential stability of almost periodic solution by employing fixed point theorem and differential inequality techniques. An example is given to show the effectiveness of the proposed method and results.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.394-402
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• 2001

In order to lessen cable vibration, new cable damper system with high damping rubber was developed using the basis of the LRB design scheme. The analysis model of cable damper system incorporate voigt-kelvin damper model into the nonlinear cable analysis model. To achieve maximum damping capacity both reducing damper stiffness and developing high damping rubber were performed. As a result of verification test, the high damping rubber damper show its effectiveness in improving cable damping capacity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.263-266
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• 2004

In this paper, Firstly, it is shown that the high vibration source of piping and pump system is the Resonanse of pump and piping system. Secondly, in order to decrese the high vibration of pump and piping system, some practical Friction damper with high damping have been developed and its effectiveness is investigated as installing it at piping system practically.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.323-327
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• 1998

Under high power IGBTs Switching, a large overvoltage is induced across the IGBT module due to the stray inductance in the circuit. This paper proposes a new gate drive circuit for high power IGBTs which can actively suppress the overvoltage across the driven IGBT at turn-off while preserving the most simple and reliable power circuit. The turn-off driving scheme has adaptive feature to the amplitude of collector current, so that the overvoltage can be limited much effectively at the fault collector current. Experimental results under various normal and fault conditions prove the effectiveness of the proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.342-347
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• 1995

Loop shaping $H_{\infty}$control with normalized coprime factorization was applied to a servo-motor driven high-speed powitioning system. The high-gain controller was designed to attenuate the postion errors caused byfriction effects and extermal disturbances. The non-existence of limit cycle was analyzed, though there is actuator saturation. The designed $H_{\infty}$control system was experimently tested in a rotary index table. Results showed its effectiveness to improve postion accuracy with out any compensation scheme for friction, and robustness to model perturbation and external disturbances.ces.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1604-1606
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• 2003

In this paper, investigated the core of transformer of high power factor and high effectiveness about design and choice technology. Transformer that use existent general core and material is high no-load loss power. Presented core choice method that can reduce loss. Could do to reduce loss according to choice technology of use material more than about 10 (%). Presented classification and check list by Core's type.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.2
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• pp.94-99
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• 2004

In this paper, We design a RF control system capable of handling multiple POS thermal printers. The system has three parts including embedded master controller, RF controller and high-speed thermal printer. Specially the designed linux embedded controller has simple structure and high performance to connect the TCP/IP network. The effectiveness of the developed RF control system is shown by proposed food ordering system.