• Ocean Systems Engineering
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• 제3권4호
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• pp.295-307
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• 2013

More FOWTs (floating offshore wind turbines) will be installed as relevant regulations and technological hurdles are removed in the coming years. In the present study, a numerical prediction tool has been developed for the fully coupled dynamic analysis of FOWTs in time domain including aero-loading, tower elasticity, blade-rotor dynamics and control, mooring dynamics, and platform motions so that the influence of rotor-control dynamics on the hull-mooring performance and vice versa can be assessed. The developed coupled analysis program is applied to Hywind spar design with 5 MW turbine. In case of spar-type floaters, the control strategy significantly influences the hull and mooring dynamics. If one of the control systems fails, the entire dynamic responses of FOWT can be significantly different. Therefore, it is important to maintain various control systems in a good operational condition. In this regard, the effects of failed blade pitch control system on FOWT performance including structural and dynamic responses of blades, tower, and floater are systematically investigated. Through this study, it is seen that the failure of one of the blade pitch control system can induce significant dynamic loadings on the other blades and the entire FOWT system. The developed technology and numerical tool are readily applicable to any types of floating wind farms in any combinations of irregular waves, dynamic winds, and steady currents.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.562-568
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• 2017

Background: The chemical characterization of metallic alloys and oxides is conventionally carried out by wet chemical analytical methods and/or instrumental methods. Instrumental neutron activation analysis (INAA) is capable of analyzing samples nondestructively. As a part of a chemical quality control exercise, Zircaloys 2 and 4, nimonic alloy, and zirconium oxide samples were analyzed by two INAA methods. The samples of alloys and oxides were also analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and direct current Arc OES methods, respectively, for quality assurance purposes. The samples are important in various fields including nuclear technology. Methods: Samples were neutron irradiated using nuclear reactors, and the radioactive assay was carried out using high-resolution gamma-ray spectrometry. Major to trace mass fractions were determined using both relative and internal monostandard (IM) NAA methods as well as OES methods. Results: In the case of alloys, compositional analyses as well as concentrations of some trace elements were determined, whereas in the case of zirconium oxides, six trace elements were determined. For method validation, British Chemical Standard (BCS)-certified reference material 310/1 (a nimonic alloy) was analyzed using both relative INAA and IM-NAA methods. Conclusion: The results showed that IM-NAA and relative INAA methods can be used for nondestructive chemical quality control of alloys and oxide samples.

• 소성∙가공
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• 제24권6호
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• pp.425-430
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• 2015

In the current paper, the effects of initial slug design on the earring of an Al rectangular battery case manufactured by impact extrusion were studied. During impact extrusion, non-uniform metal flow between the long and the short sides of the battery case leads to earring, which is subsequently trimmed. Process parameters such as friction, aspect ratio of the battery case, the die shape and the forming temperature tend to induce earring because they cause greater non-uniform metal flow. Large aspect ratio of the battery case and high friction between slug and die can greatly affect the earring of a rectangular battery case. To make a rectangular battery case without earring, it is necessary to control metal flow uniformly during impact extrusion. One of the ways to reduce the earring is to control the metal flow of slug at the initial upsetting stage. To analyze the effects of the initial slug design on earring, FE analysis was conducted using DEFORM 3D. Two types of initial slug designs were evaluated where volume was removed along either the width or thickness directions. The results show that the initial slug design can be effective in adjusting the uniformity of metal flow.

• Journal of Korean Biological Nursing Science
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• 제22권4호
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• pp.260-270
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• 2020

Purposes: Sepsis is a critical condition in which nurses should detect clinical manifestations and provide early intervention to prevent unwanted serious conditions in the patients. The initial occurrence and management of sepsis take place in general units, but there is a lack of knowledge in nurses. The purpose of this study was to examine the effects of a case-based sepsis education program and compare the case-based education program with and without smartphone applications. Methods: A quasi-experimental pre-test-post-test design with a control group was used. We provided a case-based education program with and without smartphone applications to the nurses and tested the effects of the program on knowledge, the accuracy of sepsis assessment, and self-efficacy as outcome variables. A total of 60 nurses in general units participated. To test differences in knowledge, the accuracy of sepsis assessment, and self-efficacy regarding sepsis between the groups over time, a mixed-design ANCOVA was used for parametric analysis, and generalized estimating equations (GEE) were used for nonparametric analysis. Results: There were significant differences in knowledge, the accuracy of sepsis assessment, and self-efficacy between the groups and within the groups over time. The intervention groups treated with the case-based education program showed improved outcome variables compared to the control group. There was no difference between case-based education with the smartphone application or without the application. Conclusions: The case-based education improved knowledge, the accuracy of sepsis assessment, and self-efficacy in the care of sepsis by nurses working in the general wards. The results suggest that the case-based education program for nurses was effective and eventually improved patient health outcomes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1847-1852
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• 2004

This article provides the connection between feedback stabilization and interpolation conditions for n-D linear systems (n > 1). In addition to internal stability, if one demands performance as a design goal, then there results an n-D matrix Nevanlinna-Pick interpolation problem. Application of recent work on Nevanlinna-Pick interpolation on the polydisk yields a solution of the problem for the 2-D case. The same analysis applies in the n-D case (n > 2), but leads to solutions which are contractive in a norm (the "Schur-Agler norm") somewhat stronger than the $H^{\infty}$ norm. This is an analogous version of the connection between the standard $H^{\infty}$ control problem and an interpolation problem of Nevanlinna-Pick type in the classical 1-D linear time-invariant systems.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.146-157
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• 1999

Safety systems for road vehicles have been rapidly developed in recent years. Especially, the VDC(Vehicle dynamics Control) system is a new active safety system for road vehicles which controls its dynamic vehicle motion in emergency situations . In the case of configuring the VDC system by utilizing the ABS(Anti-lock Brake System), the role of a control logic which directly influences the vehicle motion is very important. In this study the performance of the VDC vehicle was compared to the performances of the CBS (Conventional Brake system )and ABS vehicle. For various driving conditions , the simulation of vehicle dynamics with known VDC control logics was performed. Analysis results showed the VDC vehicle could stably perform even on the road of low coefficient of friction. In addition it was shown that the basic control logic for the VDC system could outstandingly improve driving stability in the case of braking as well as constant speed cruising.

• Journal of the Korean Data and Information Science Society
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• 제19권4호
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• pp.1191-1200
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• 2008

Recently classroom monitoring is becoming important since the lecture is being held in the classroom and academic institutions are interested in the quality assurance. Some institutions have adopted ISO 9000 systems and constructed monitoring system through measurement, analysis and improvement. In this study quality assurance problems in academic institutions and the requirements of ISO 9001:2000 will be briefly discussed. Next we will investigate how to monitor the lecture in the classroom(in-class) using statistical process control techniques such as control charts. Then case study will be given to illustrate the technique to use appropriate statistics. Finally how to monitor the learning process during in-class and after-class will be proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2242-2244
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• 2003

This paper considers a networked control system (NCS) that consists of an inverted cart pendulum, a digital controller, and a controller area network (CAN) in which the actuator and sensors of the pendulum are connected to form a closed-loop system. The worst-case message response time (WCMRT) in the CAN is analyzed and the analysis results are applied to the target control system. For the case where the control system cannot satisfy the WCMRT condition and therefore time delays are inevitable, the Luck and Ray method is used to compensate the network-induced time delays. Simulations are carried out to show the feasibility of the proposed scheme.

• Asian Pacific Journal of Cancer Prevention
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• 제14권8호
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• pp.4733-4737
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• 2013

Purpose: Numerous observational epidemiological studies have evaluated associations between breastfeeding and the risk of childhood Hodgkin lymphoma; however, the existing results are inconsistent. We therefore conducted a systematic review and meta-analysis. Methods: Medical literature was searched in the Pubmed and Embase databases to identify all English-language relevant studies up to April 10, 2013. Reference lists were thereafter hand-searched for additional articles. Studies that reported relative risk ratios (RRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were included. This meta-analysis was conducted in accordance with the guidelines for the meta-analysis of observational studies in epidemiology. Results: We finally included 10 case-control studies in our meta-analysis, involving 1,618 childhood Hodgkin lymphoma cases and 8,181 controls. Overall, we did found a borderline significant association between breastfeeding and reduced risk of childhood Hodgkin lymphoma comparing ever breastfed children to never breastfed children (pooled OR =0.79; 95%CI, 0.58-1.08; P=0.13), with limited evidence for between-study heterogeneity (P =0.12, $I^2$ = 35.70%). Conclusion: There is limited evidence for an inverse association between breastfeeding and risk of childhood Hodgkin lymphoma.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.216-219
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• 2003

The resonant inverter is widely used for induction heating, electronic ballast and supersonic motor driving circuit. In the meantime, control techniques of PWM, PFM etc.. are mainly applied to control the output power of the resonant inverter. But, in the case of using the half bridge resonant inverter, it is difficult to control the output power by PWM, because its main circuit does not provide the load free-wheeling mode. Therefore, PAM or PFM was usually applied to control output power of half bridge resonant inverter. However, PAM needs a variable DC voltage source, which makes the system structure more complex. On the other hand, in case of PFM, efficiency is declined by operation with poor power factor. This paper Proposed the novel half bridge resonant inverter which can provide the load free-wheeling mode. Also its analysis results for PWM operation with unity fundamental power factor are Presented and compared with other resonant inverters using PWM and PFM.