• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.349-358
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• 2004

A low pressure impactor is an impaction device to separate airborne particles into aerodynamic size classes at low pressure condition. We designed a two-stage low-pressure impactor to classify submicron sized environmental aerosols. Performance evaluation was carried out for stages 1 and 2 by using an electrical method. Monodisperse liquid dioctyl sebacate (DOS) particles were generated using evaporation-condensation process followed by electrostatic classification using a DMA (differential mobility analyzer). The test particles were in the range of 0.08∼0.8$\mu\textrm{m}$. For the evaluation of the impactor we used two electrometers; one was connected to the impaction plate of the impactor and the other was to the Faraday cage used as a backup filter. The effect of polydispersity of test aerosols on the performance was investigated. The results showed that the experimental 50-% cutoff diameters at each impactor's operation pressure were 0.53 and 0.187$\mu\textrm{m}$ for stages 1 and stage 2, respectively. The effects of operation pressure on the cutoff diameter and the steepness of collection efficiency curves were also investigated.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.157-163
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• 2014

This paper proposes a two-stage step-down buck and a tapped-inductor boost cascaded converter for high efficiency photovoltaic micro-inverter applications. The proposed inverter is a new structure to inject a rectified sinusoidal current into a low-frequency switching inverter for single-phase grid with unity power factor. To build a rectified-waveform of the output current. the converter employs both of a high efficiency step-up and a step-down converter in cascade. In step-down mode, tapped inductor(TI) boost converter stops and the buck converter operates alone. In boost mode, the TI converter operates with the halt of buck operation. The converter provides a rectified current to low frequency inverter, then the inverter converts the current into a unity power-factor sinusoidal waveform. By applying a TI, the converter can decrease the turn-on ratios of the main switch in TI boost converter even with an extreme step-up operation. The performance validation of the proposed design is confirmed by an experimental results of a 120W hardware prototype.

• Steel and Composite Structures
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• v.18 no.4
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• pp.971-983
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• 2015

To promote greater acceptance and use of composite RCS systems, a two-bay two-story frame specimen with improved composite RCS joint details was tested in the laboratory under reversed cyclic loading. The test revealed superior seismic performance with stable load versus story drift response and excellent deformation capacity for an inter-story drift ratio up to 1/25. It was found that the failure process of the frame meets the strong-column weak-beam criterion. Furthermore, cracking inter-story drift ratio and ultimate inter-story drift ratio both satisfy the limitation prescribed by the design code. Additionally, inter-story drift ratios at yielding and peak load stage provide reference data for Performance-Based Seismic Design (PBSD) approaches for composite RCS frames. An advantage over conventional reinforced concrete and steel moment frame systems is that the displacement ductility coefficient of the RCS frame system is much larger. To conclude, the test results prove that composite RCS frame systems perform satisfactorily under simulated earthquake action, which further validates the reliability of this innovative system. Based on the test result, some suggestions are presented for the design of composite RCS frame systems.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.644-652
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• 2016

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.3
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• pp.339-349
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• 2017

This paper proposes a four-stage algorithm for detecting lanes on a driving car. In the first stage, it extracts region of interests in an image. In the second stage, it employs a median filter to remove noise. In the third stage, a binary algorithm is used to classify two classes of backgrond and foreground of an input image. Finally, an image erosion algorithm is utilized to obtain clear lanes by removing noises and edges remained after the binary process. However, the proposed lane detection algorithm requires high computational time. To address this issue, this paper presents a parallel implementation of a real-time line detection algorithm on a multi-core architecture. In addition, we implement and simulate 8 different processing element (PE) architectures to select an optimal PE architecture for the target application. Experimental results indicate that 40×40 PE architecture show the best performance, energy efficiency and area efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.52-59
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• 2010

The conventional CCFL (Cold Cathode Fluorescent Lamp) inverter used in the backlight unit for LCD-TV, composed of the three power stage, can degrade the whole power conversion efficiency. In this paper, a novel scheme to drive the CCFL, composed only of the two power stage without using a dc/dc power stage, is proposed to enhance the whole power conversion efficiency. By adopting the proposed "4-in-1 Transformer", the current balance and the simultaneous ignition among the four CCFL lamp are assured with the one inverter circuit. The proposed scheme features the simple circuit structure, which can save the volume and the cost in the LCD backlight unit. Design considerations are discussed and design procedures are derived. Experimental results of the proposed scheme for 40" LCD-TV are presented to confirm the theoretical analysis.

• International Journal of Fluid Machinery and Systems
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• v.4 no.2
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• pp.243-254
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• 2011

In the present paper, we focus on the flow computation of a low head Propeller turbine at a wide range of design and off-design operating conditions. First, we will present the results on the efficiency hill chart prediction of the Propeller turbine and discuss the consequences of using non-homologous blade geometries for the CFD simulation. The flow characteristics of the entire turbine will be also investigated and compared with experimental data at different measurement planes. Two operating conditions are selected, the first one at the best efficiency point and the second one at part load condition. At the same time, for the same selected operating points, the numerical results for the entire turbine simulation will be compared with flow simulation with our standard stage calculation approach which includes only guide vane, runner and draft tube geometries.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.63
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• pp.101-110
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• 2001

This study is concern with the design of experiment planning for quality improvement in flow shop manufacturing system. In this study, the procedure of two stage experiment planning are proposed and applied to the manufacturing process of Li/$MnO_2$ batteries. The result of in this paper is that, compared with the current process conditions, 52% of the insulation inspection process, 81.6% of the first premier discharge process, 98.5% of the second premier discharge process, 84.7% of O.C.V./C.C.V. process, and 86.2% of voltage inspection process are decreased. After a given period of time, the life of the batteries extends to 75 hours, which means the 15% improvement in capacity. In case that the proposed methods are applied to the process Improvements of the flow shop manufacturing system, the much effected in experimental cost- saving and quality improvement.

• Korean Journal of Adult Nursing
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• v.20 no.3
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• pp.406-417
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• 2008

Purpose: The purpose of this study was to develop an empowerment program as a nursing intervention for the patients having an acute stroke and to determine the effects of the program on their motivation, depression, and activities of daily living(ADLs). Methods: An non-equivalent control group pretest-posttest design was used in this study. Sixty subjects were recruited from two separated institutions: 31 patients were allocated into experimental group and 29 were into control group. Six week empowerment program was provided to the experimental group. The study was conducted from November 2006 to March 2007. Results: After 6 week empowerment program, rehabilitation motivation was significantly increased in the experimental group in comparison to the control group(t=-2.173, p=.036). There were no significant differences in depression and ADLs between experimental and control groups. Conclusion: The empowerment program effectively increased rehabilitation motivation of patients with stroke, while did not improve the levels of depression and ADLs. Future long-term intervention may benefit the patients more in terms of depression and ADLs when considering the acute stage of the patients in this study.

• The Journal of Korean Academic Society of Nursing Education
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• v.18 no.2
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• pp.248-258
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• 2012

Purpose: The purpose of this study was to compare the effects of CEDA (Cross Examination Debate Association) debate with those of traditional lecture education on moral judgment and ethical values using the Korean version of DIT and the ethical values. Methods: The experiment was performed for 9 weeks, from September 2 to November 12, 2010. Participants were 71 undergraduate nursing students in a nursing college, assigned to an experimental group (36 students) or a control group (35 students). The design of this study was a non equivalent control group pretest-posttest design. Results: The experimental group reported significantly higher scores of the 4 stage scores of moral judgment (t=-2.19, p=.036) and ethical values (t=3.04, p=.004) than the control group. However, no significant differences were found in the P score of moral judgment between the two groups. Conclusion: The findings of this study showed the benefits of providing a CEDA debate course for nursing ethics education. Therefore, in further studies, it is necessary to develop various teaching strategies or educational programs to improve nursing ethical values and moral judgment.