• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.629-634
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• 2011

초고속 비행체에 적용 가능한 소모성 터빈엔진 개발을 위한 사전연구를 수행하였다. 엔진 요구도 및 설계점 결정을 위한 가상 운용임무형상을 선정하고, 유사급 엔진과 참고문헌 등을 통해 확보된 데이터를 활용하여 설계점 해석을 수행하였는데, 해면고도, 마하수 1.2 조건에서 터빈입구온도 3,600R에 대한 설계점 계산결과, 비추력 2599.4 ft/s, 비연료소모율 1.483 lb/($lb^*h$)이 예측되었다. 설계점 계산결과를 기준으로 두 가지 임무형상에 대한 엔진 성능해석결과, 엔진 최대 순추력을 결정하는 설계변수는 천음속 및 낮은 초음속영역에서는 터빈입구온도, 높은 초음속 영역에서는 압축기 출구온도임을 확인하였다. 이밖에도 단순, 저가, 경량의 엔진형상으로 축류형 다단압축기와 직류형 연소기, 1단 축류터빈, 고정 수축팽창 노즐이 적용된 단순터보제트엔진을 제시하였다.

• Advances in Energy Research
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• 제4권2호
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• pp.121-146
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• 2016

This study is concerned with the analysis of two renewable technologies for electric energy production: wind energy and photovoltaic energy. The two technologies were assessed and compared by economic point of view, by using selected indicators characterized by a clear calculation approach, requirement of information easy to be collected, clear, but even complete, interpretation of results. The used economic indicators are Levelized Cost of Energy, $CO_2$ abatement cost and fossil fuel saving specific cost; these last two specifically aimed at evaluating the different capabilities that renewable technologies have to cut down direct $CO_2$ emissions and to avoid fossil fuel extraction. The two technologies were compared also from the environmental point of view by applying Life Cycle Assessment approach and using the environmental impact categories from the Eco-indicator'95 method. The economic analysis was developed by taking into account different energy system sizes and different geographic areas in order to compare different European conditions (Italy, Germany and Denmark) in term of renewable resource availability and market trend. The environmental analysis was developed comparing two particular types of PV and wind plants, respectively residential and micro-wind turbine, located in Italy. According to the three calculated economic indicators, the wind energy emerged as more favorable than PV energy. From the environmental point of view, both the technologies are able to provide savings for almost all the considered environmental impact categories. The proposed approach, based on the use of economic and environmental indicators may be useful in supporting the policies and the decision making procedures concerned with the promotion and use of renewables, in reference to the specific geographic, economic and temporal conditions.

• 한국인터넷방송통신학회논문지
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• 제18권1호
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• pp.129-134
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• 2018

실내에서의 위치를 추정하기 위한 기술 연구가 활발하게 진행되고 있다. 특히 추가적인 기반 시설을 필요로 하지 않는 WiFi fingerprint 방식은 경제성이 높아서 부분적으로 실용화되고 있다. 사전에 여러 지점에서 측정된 무선랜 수신 신호의 세기 정보와 추후에 특정 지점에서 측정된 세기 정보를 비교하여 유사한 지점을 해당 지점으로 추정하는 KNN 방식은 간단하지만 성능이 좋다. 그러나 기존의 KNN 방식은 평균하는 후보 위치들의 개수 K가 일정하므로, 특정 지점에 따라 위치 추정 오차가 최적화되지 못하는 문제가 있다. 본 논문에서는 특정 지점마다 K 값을 적응적으로 변화시키는 KNN 방식에서 평균 범위를 설정하는 알고리즘을 제안하고 실험 데이터에 적용하여 그 성능을 평가하였다.

• 대한간호학회지
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• 제29권3호
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• pp.563-575
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• 1999

The purpose of this study was to examine the correlation between self-efficacy and self-care of hemodialysis patients. The subjects consisted of 140 hemodialysis patients who underwent hemodialysis at 2 university hospitals. The data were collected by questionnaires and chart review. The questinnaire used the self-efficacy tool developed by Kim Ju Hyune(1995) and the self-care tool developed by literature review and indepth open openended questions to 10 patients. Also, the questionnaire included physiologic data which collected through review of the patients' charts. The statistical analysis was used the SPSS program for frequency, mean, t-test, ANOVA and Pearson correlation. The results were as follows : 1. The mean score for general self-efficacy of hemodialysis patients was 3.103(1-4point) and there were significant differences according to percieved health. The mean score for specific self-efficacy of hemodialysis patients was 3.113 (1-4point) and there were significant differencies according to percieved health, side effects and complications which related hemodialysis. 2. The mean score for self-care of hemodialysis patients was 3.822(1-5point) and there were significant differencies according to marital status and economic level. 3. The relationship between general self-efficacy and self-care was a positive correlation(P＝.000). The relationship between specific self-efficacy and self-care was a positive correlation(P＝.000). In conclusion, this study revealed the level of self-efficacy and self-care, and the positive correlation between self-efficacy and self-care in hemodialysis patients. Therefore, intervention is needed to promote self-efficacy for self-care of hemodialysis patients. Considering the vulnerable self-care area same as checking blood pressure and weight, fluid restriction, social adjustment, exercise and rest, luther studies should develop self-efficacy promoting programs for self-care of hemodialysis patients.

• 분석과학
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• 제16권3호
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• pp.232-239
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• 2003

청주시 석남천 유역의 4개 지점, 미호천 유역의 1개 지점, 석남천과 미호천 합류지역의 1개 지점 등 6개 지점을 기준지점으로 택하고, 각 지점의 상층, 중층, 하층에서 침전물을 채취하여 조사용 시료를 제작하였다. 한국원자력연구소의 연구용 원자로(HANARO)의 중성자 선을 이용한 중성자 방사화 분석법으로 원소함량을 분석하였다. 미국 표준연구원(NIST)의 인증표준물질을 이용하여 시료 중의 30 개 원소들의 함량을 비교법으로 분석하였다. 그 분석 결과로부터 하천오염원지역에서 하류로 이어지는 지역의 침전물 오염도분포조사 및 예측시 오염물질의 원소비중과 유속을 고려해야 하며 하천침전물의 함량분석을 위한 시료를 채취할 때 시료의 지역적 대표성을 확립하기 위해서는 원소의 비중과 유속 등을 고려하여 수직적 범위를 정할 필요가 있음을 알았다.

• 지역사회간호학회지
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• 제21권2호
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• pp.178-187
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• 2010

Purpose: The purpose of this study was to analyze the effects of a walking leader program on changes in walking knowledge and self-efficacy. Methods: The subjects were 276 participants who participated in the nationwide walking leader program 9 times from May to September in 2008. Data were collected before and after the program by an organized questionnaire. Results: 1) Knowledge related to walking exercise increased significantly to 4.14 point from 2.90 point after the program (t=-20.70, p<.001). 2) Self-efficacy related to walking exercise increased significantly to 4.08 point from 3.40 point after the program (t=13.93, p<.001). 3) Significant factors that affected knowledge and self efficacy before the program were regular exercise and subjective health status. The history of chronic disease and smoking were significantly affecting factors to knowledge and self-efficacy after the program. Conclusion: The walking leader program promoted the participants' walking knowledge and selfefficacy. It is necessary to develop more specific programs tailored to socio-demographic characteristics of participants and to make efforts to increase participants with active public information.

• 정보처리학회논문지C
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• 제15C권5호
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• pp.409-418
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• 2008

본 논문에서는 운영체제에서 지원하는 PPP 프로그램이 없는, 즉 별도의 운영체제를 사용하지 않는 임베디드 시스템에서 글로벌스타 인공위성 모뎀을 이용하기 위한 PPP 프로그램을 작성하였다. 글로벌스타를 포함한 오브컴, 인말샛과 같은 많은 위성통신 시스템은 데이터 링크 구현을 위하여 그 자체의 인터페이스를 제공하고 있다. 글로벌스타 위성 시스템과 데이터 링크를 구현하기 위해서는 글로벌스타 위성에서 사용하는 PPP를 사용해야 한다. 따라서 본 논문에서는 임베디드 프로세서 기반의 PPP를 구현하였으며, 이와 더불어 사용자 단말 장치를 개발하였다. 사용자 단말 장치는 다양한 응용분야에 사용될 수 있도록 여러 가지 입출력 장치 및 센서를 장착하여 설계 및 실현하였다. 실험 테스트를 통하여 이와 같이 구축된 모든 시스템은 글로벌스타 데이터 링크를 통해서 잘 동작함을 확인한다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권4호
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• pp.588-594
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• 2009

The maximum power point operation point(MPPOP) of photovoltaic(PV) power generation systems changes with varying atmospheric conditions such as temperature, solar radiation. For achieving a high efficiency in PV system, it is very important for PV system to track the MPPOP correctly according to operation condition. Although the MPPT(maximum power point tracking) algorithm which applied P&O(Perturbation & Observation) or IncCnd(Incremental Conductance) algorithm tracks the MPPOP efficiently, its efficiency drops noticeably in case that the incidence angle of PV panel on buoy changes rapidly. To solve this problem, this paper proposes maximum power point searching and tracking algorithm(MPPST). The proposed algorithm set the specific area and measures the PV voltage at the same interval. The proposed algorithm have been obtained high efficiency than P&O algorithm through ocean experiment.

• The Journal of the Acoustical Society of Korea
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• 제16권1E호
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• pp.41-48
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• 1997

The very purpose of subband codec is the attainment of data rate compression through the use of quantizer and optimum bit allocation for each decimated signal. Yet the question of floating-point quantization effects in subband codec has received scant attention. There has been no direct focus on the analysis of quantization errors, nor on design with quantization errors embedded explicitly in the criterion. This paper provides a rigorous theory for the modelling, analysis and optimum design of the general M-band subband codec in the presence of the floating-point quantization noise. The floating-point quantizers are embedded into the codec structure by its equivalent multiplicative noise model. We then decompose the analysis and synthesis subband filter banks of the codec into the polyphase form and construct an equivalent time-invariant structure to compute exact expression for the mean square quantization error in the reconstructed an equivalent time-invariant structure to compute exact expression for the mean square quantization error in the reconstructed output. The optimum design criteria of the subband codec is given to the design of the analysis/synthesis filter bank and the floating-point quantizer to minimize the output mean square error. Specific optimum design examples are developed with two types of filter of filter banks-orthonormal and biorthogonal filter bank, along with their perpormance analysis.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.545-552
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• 2001

Analysis of a structure for vertical vibration requires a lot of computational efforts because large number of degrees of freedom are generally involved in the dynamic response. Especially, when a structure is loaded with local vibration source, it may not be economical to model the whole structure to obtain the responses of specific members located near or far from the sources. In this study, substructure models have been used for analysis of local vibration An analysis of local vibration is performed for the case that the loaded point and the response point are located on the same floor. Other analysis is performed for the case that the loaded point and the response point are located on the different floor. In this case, if only the floors on which loaded and response points are located are modeled, response of substructure model is very different from that of full model. So, there should be a consideration that degrees of freedom of floors in addition to those of loaded and response floors are included to improve results of dynamic analysis. In this study, floors between loaded floor and response floor were modeled so that modeshapes which affect the response are presented well.