• Child Health Nursing Research
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• 제6권3호
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• pp.397-410
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• 2000

This is a nonequivalent control group pretest- posttest design in quasi experimental basis to assess how the thermal head and feet support influences on early stage weight gain in premature neonates. The clients were selected among the premature infants with the weight under 2000gms and with the gestational period under 37 weeks, admitted over 15 days in K university hospital, Seoul. The control group of 29 were selected from January 1998 to August 1998, who were without head and feet thermal support, and the experimental group of 30 were selected from September 1998 to May 1999, who were with the two thermal interventions. The results of the study follow, 1.The experimental group with thermal interventions showed more weight gain than the control group without thermal interven- tions, which was statistically significant between the two groups. 2.The physiological weight loss after birth showed less in the experimental group than in the control group. 3.The recovery of the birth weight after the physiologic weight loss showed no statistical difference between the experimental group and the control group. Consequently, the thermal head and feet supportive nursing intervention could be applied as a nursing intervention program to help the premature neonates' development. With the results above we should like to suggest the following: 1) A continuous application in the practice of our thermal supportive intervention for the premature neonates, a development of the content through evaluation, and a comparision of the results through a long time study. 2) A neccessity of deveopment of various study and cross comparision. 3) A neccessity of multi-angular study on the premature infants' characteristics influencing the thermal therapy and the study of the individual differences of the clients.

• 대한기계학회논문집B
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• 제28권4호
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• pp.389-394
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• 2004

An experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is a act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel bums. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as a primary and secondary fuels. This study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.161-166
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• 2001

An Experimental study on the NOx formation of LNG flame in fuel staged combustor has been studied. The design concept of multi fuel/air staged combustor is creation of two separate flame, a primary flame is act as a pilot flame for the secondary combustion stage combustion zone, where most of fuel burns. Experiments were performed on a semi-industrial scale (thermal input 0.233 MW) in a laboratory furnace and Liquefied Natural Gas(LNG) was used as primary and secondary fuels. The study included parametric study to identify the optimum operating conditions which are primary/secondary fuel ratio, and primary/secondary air ratio for reducing NOx emission with two types of nozzle. The test demonstrated that NOx emission can be reduced by >70% in accordance with operating conditions.

• Journal of Power Electronics
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• 제13권2호
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• pp.206-213
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• 2013

In this paper, an improved passive snubber is investigated in a single-phase single-stage full-bridge boost power factor correction (PFC) converter, by which the voltage spike across primary side of the power transformer can be suppressed and the absorbed energy can be transferred to the output side. When compared with the basic passive snubber, the two single-inductors are replaced by a coupled-inductor in the improved snubber. As a result, synchronous resonances in the snubber can be achieved, which can avoid the unbalance of the voltage and current in the snubber. The operational principle of the improved passive snubber is analyzed in detail based on a single-phase PFC converter, and the design considerations of both the snubber and the coupled-inductor are given. Finally, a laboratory-made prototype is built, and the experimental results verify the feasibility of the proposed method and the validity of the theoretical analysis and design method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.951-954
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• 2006

This Study introduces the design of a reactive type silencer for reducing impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level above 150dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study. the reactive type silencers have been utilized. The performance of noise reduction for them can be expressed by insertion loss. The reactive silencers have been tested for 23 different types with each different porosity, hole diameter and depth. From the experimental results, it is found that the reactive silencer has an excellent performance to greatly suppress the impulse noise. The one-stage, two-stage and three-stage reactive type silencers have been shown to have the insertion losses of about from 35dB (A) to 25dB(A).

• 한국간호교육학회지
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• 제19권4호
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• pp.640-647
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• 2013

Purpose: The purpose of this study was to identify the effectiveness of smoking cessation education using the transtheoretical model on the process of change, smoking temptation, decisional balance and stage change transition. Methods: A nonequivalent control group non-synchronized design was used for this study. The study population was 44 male college students in the experimental group and 66 students in the control group. Smoking cessation education was administered to the experimental group at one university. Descriptive analysis, t-test, and ANCOVA were used with the SPSS 19.0 program to analyze the data. Results: After providing a smoking cessation program, the experimental group showed significantly higher scores for self-efficacy for smoking cessation, process of change, and a lower score in decisional balance for pros of smoking and nicotine dependancy compared to the control group two weeks after the pre-test. However, no significant differences were found at four weeks after the pre-test. Conclusion: The findings indicate that this program could have a positive effect on process of change, decisional balance and stage transition for college student smokers.

• 전력전자학회논문지
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• 제26권2호
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• pp.82-89
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• 2021

This study proposes a DAB two-stage series structure with insulated bidirectional DC-DC converter for two-way power transfer between the renewable energy of high voltages (1 kV and above). The proposed circuit transforms the existing DAB converter into a two-stage series structure to reduce the pressure in the switch. The problem of power imbalance occurring in the design of the DAB converter second-stage series is improved by applying the cell balancing method circuit and the common mode coupled inductor using an external flying capacitor instead of reflecting the existing improvement measures, voltage balance control, and inductor current control. In addition, a no-load supercharging sequence is proposed in high voltages and high-speed switching by using the fixed duty output method. This study presents the analysis results through the structure of the proposed circuit, the principle of improving the power imbalance problem, and simulations. Prototypes were manufactured to meet the specifications of input/output voltage of 1700 V, maximum load of 65 kW, and switching frequency of 51kHz, and the validity of the topology was verified using the experimental results and efficiency data.

• Design & Manufacturing
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• 제9권2호
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• pp.30-33
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• 2015

In injection molding, many kinds of defects have occurred because of a characteristic of plastics injection molding. Weld line is one of the defects is formed when separated melt fronts recombine together during the mold filling stage. That is one of problems in injection molding. Weld lines in the appearance of plastics parts can deteriorate visible quality. And most importantly, the local mechanical strength in the weld line area can be significantly weaker. It could be one of the most problems for structural applications. In this study, the mold available two-shot-molding of same polymers have been designed, and a series of experiment about tensile strength in weld line area has been conducted using Taguchi's design of experiment to optimize injection molding conditions decreasing of weld strength and find out a factors affected weld strength in two-shot- molding.

• 한국항공우주학회지
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• 제30권4호
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• pp.77-83
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• 2002

헬리콥터용 2단 축류압축기의 성능향상을 위한 설계/재설계 과정에서 수치해석을 통한 성능예측 및 내부유동분석에 대한 연구가 수행되었다. 기초 설계된 2단 압축기에 대한 유동해석을 통하여 스톨, 쵸크 등의 주요한 유동현상의 발생원인을 파악하였다. 또한 전압력 상승, 효율, 출구유동분포 등의 계산값이 실험값과의 비교에서 비교적 잘 일치하는 결과를 얻음으로써 유동해석을 통한 다단 압축기 성능예측에 대한 가능성을 검증하였으며, 재설계의 방향을 제시하였다. 따라서 3차원 유동해석은 다단 압축기의 개발 및 설계변경에 있어서 실험을 대신하여 적은 비용과 시간을 들이고도 만족한 결과를 얻을 수 있는 가능성을 보여 주었다. 1D/2D 기법으로 재설계된 압축기는 요구성능에는 다소 미흡하지만 재설계의 목적과 방향에 성공적으로 부합함을 보였다. 그러나 보다 나은 성능을 위해 향후 3차원적인 블레이드의 설계변경이 필요할 것으로 예측되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1417-1422
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• 2003

An electrical cascade impactor is a multistage impaction device to separate airborne particles into aerodynamic size classes using electrical method. We designed a real-time three-stage electrical low-pressure impactor, which is proper to nanometer sized environmental aerosols. Performance evaluation was carried out for stage 1 and 2. The monodisperse liquid dioctyl sebacate (DOS) particles were generated using condensation-evaporation followed by electrostatic classification using DMA (differential mobility analizer) for particles with diameters in the range of $0.04{\sim}0.8{\mu}m$. The evaluation of the electrical impactor is based on the use of two electrometers, one connected to the impaction plate of the impactor, and the other to the faraday cage as backup filter. The results showed that the experimental 50% cutoff diameters in the operation pressure were 0.53 and $0.12{\mu}m$ for stage 1 and stage 2. The effect of operation pressure on the cutoff diameter and the steepness of collection effcieicy curves is investigated.