• 동력기계공학회지
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• 제18권1호
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• pp.57-62
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• 2014

This paper present the performance characteristics of R404A two-stage compression refrigeration system. The operating parameters considered in this study include evaporating and condensing temperature, subcooling and superheating degree, compressor efficiency. The main results were summarized as follows: The COP of two-stage compression refrigeration system using R404A has an effect on the variation of evaporation temperature, condensation temperature, subcooling degree and compressor efficiency, but not an effect on the superheating degree. R404A two-stage compression refrigeration system is unstable because COP of this system is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. This is inefficient for long-term use.

• 한국공작기계학회논문집
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• 제14권4호
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• pp.69-74
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• 2005

Nowadays CFC and HCFC refrigerants are restricted because they causes to depletion of ozone layer. Accordingly, an experiment is apply to the $NH_3$ gas for refrigerant to study the performance characteristic and to improve the energy efficiency. An experiment are carried out for the condensed pressure in a range from 14.5bar to 16bar and for degree of superheat in a range from 0 to $10^{\circ}C$ at each condensed pressure. As the result of experiment, when degree of superheat is $1^{\circ}C$ and condensed pressure is 14.5bar, the refrigeration system showed the high performance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2454-2459
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• 2008

The objective of this paper is to find out the most effective injection angle for the purpose of deicing through SC/Tetra, a commonly used CFD software. Nowadays, vehicles are developed giving priority to an improved interior which emphasizes a pleasant environment and thermal comfort without decreasing the basic performance. Clear visibility is one of the most important phenomenon. The primary factors which affect the efficiency of deicing are 3D geometry of Defrost Nozzle, the inlet velocity and temperature of the flow and the injection angle. However in this paper, all these parameters are optimized by changing the injection angle. A wide range of injection angle from 5 degree to 50 degree have been considered for analysis. A very good defrosting performance has been achieved with 45 degree injection angle which can satisfy the condition of NHTSA.

• 한국태양에너지학회 논문집
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• 제39권6호
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• pp.41-54
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• 2019

The purpose of this study is to analyze the performance of solar thermal system according to regional weather conditions and feedwater temperature. The performance analysis of the system was carried out for the annual and winter periods in terms of solar fraction, collector efficiency and it's optimal degree. The system is simulated using TRNSYS program for 6 cities, Seoul, Incheon, Gangneung, Mokpo, Gwangju, and Ulsan. Simulation results prove that the solar fraction of the system varies greatly from region to region, depending on weather conditions and feedwater temperatures. Monthly average solar fraction for winter season from November to February, a time when heat energy is most required, indicated that the highest is 73.6% in Gangnueng and the lowest is 56.9% in Seoul. This is about 30% relative difference between the two cities. On the other hand, the collector efficiency of the system for all six cities was analyzed in the range between 40% and 42%, indicating small difference compare to the solar fraction. The annual average solar fraction is rated the highest at 40 collector degree, while monthly average solar fraction during winter season is rated at 60 degree.

• 전기학회논문지P
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• 제52권2호
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• pp.74-80
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• 2003

In this paper, a robust two-degree-of-freedom(TDF) the speed control system using $H_{\infty}$ optimization method and real genetic algorithm is proposed for the robust stability and the robust performance in dc servo motor system. This control system composed of feedback and feedforward controller. The feedback(FB) controller with $H_{\infty}$ optimization method is designed for real genetic algorithm that is model matching problem using mixed sensitivity function. The feedforward(FF) controller with $H_{\infty}$optimization method is minimized the error between transfer function of the optimal model and the overall transfer function. The proposed robust two-degree-of-freedom speed control system is simulated to the dc servo motor. By the simulation, feedback controller can obtain the robust stability property and feedforward controller can obtain the robust performance property under modelling error. The performance of the dc servo motor is analyzed by the experiment setting. The validity of the proposed method is verified through being compared with pid(proportional integrated differential)control system design method for the dc servo motor.

• 한국치위생학회지
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• 제20권3호
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• pp.387-397
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• 2020

Objectives: This study aimed to evaluate the inhibitory effects of probiotics containing Lactobacillus reuteri on Streptococcus mutans and Aggregatibacter actinomycetemcomitans. In addition, the degree of biofilm formation, initial acidity, buffering ability, and acid production performance were measured to confirm the dental caries-inducing ability. Methods: S. mutans (KCTC3065) and A. actinomycetemcomitans (KCTC2581) were used as experimental strains. The number of viable cells, degree of biofilm formation, initial pH, buffering capacity, and production performance were measured for comparing L. reuteri-containing probiotics and Bulgaris. Results: The viability of S. mutans in the groups was reduced in the following order: Bulgaris, probiotics, control. The degree of biofilm formation was significantly higher at 0% and gradually reduced at different concentrations (p<0.01). At 2.5%, the absorbance of the probiotics and Bulgaris groups differed significantly (p<0.01). The acid formation ability differed significantly based on the performance of S. mutans in each product (p<0.05). The absorbance of the probiotics group was significantly lower than that of the Bulgaris group (p<0.01). Conclusions: This study suggests that the use of L. reuteri-containing probiotics as an adjuvant for the prevention and decreasing of oral diseases may reduce their incidence, which can be considered one of the benefits of using probiotics.

• 대한한방부인과학회지
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• 제31권3호
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• pp.79-96
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• 2018

Objectives: The objective of this study was to survey the performance of postpartum care and compare the western medicine and Korean medicine according to women's postpartum disease. The purpose of this study was to provide basic data for the prevention and management of postpartum disease. Methods: The subjects were 228 women who experienced postpartum disease. This research was conducted in G city, at outpatient department of western medicine hospital and Korean medicine hospital. The degree of performance of postpartum care was measured on a 4-point scale divided by each area, and was compared in three groups. Results: Postpartum care includes traditional postpartum care and postpartum care in hospitals. The degree of performance of postpartum care means that the higher the score, the better. The traditional postpartum care performance score was 2.35 and the postpartum care performance score at the hospital was 1.63. The results of this study showed that the performance of traditional postpartum care was higher than that of postpartum care administered in hospitals. The perception of traditional postpartum care methods was 'An indispensable postpartum care method for health' (75.9%). The most effective method of postpartum care was 'consolidate in harmony traditional postpartum care and guidance of the medical team' (88.2%). Conclusions: The improvement and satisfaction degree of postpartum care were higher in Korean medicine than in western treatments. Therefore, the most efficient method of postpartum care must be integrated in harmony with the direction of the medical staff and traditional methods of postpartum care.

• 융합신호처리학회논문지
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• 제5권1호
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• pp.66-72
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• 2004

PID제어는 수십년간 잘 사용이 되어 왔다. PID알고리즘은 적당한 튜닝법을 사용하여 파라미터를 구하여 제어시스템을 설계한다. 그러나 어떤 경우에는 다양한 평가지표가 필요하고, 따라서 이들 다양한 평가지표를 사용하여 설계할 제어시스템이 필요로 하는 조건들을 만족되게 해야 한다. 본 논문에서는 오차, 제어입력의 에너지 및 제어입력의 변화율 등의 시간영역지표들은 물론이고 견실성을 확보하기 위해서 견실성 지표 예들 들면 가중치를 부과한 상보감도함수의 무한대놈을 포함한 선형조합형태의 평가지표를 사용하여 2 자유도 PID제어기를 설계한다. 수치해석을 통하여 최적의 2 자유도 PID파라미터들을 구한다. 이들 I-PD형 등의 2자유도 형은 PID를 변형한 형태로서 단일의 PID제어기들에 비해 더 개선된 출력특성을 얻을 수 있음을 보인다. 시뮬레이션은 MATLAB m 및 mdl파일을 통하여 실행한다.

• International Journal of Advanced Culture Technology
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• 제10권1호
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• pp.187-195
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• 2022

Since most of the first witnesses of cardiac arrest in clinical settings are nurses, the ability to perform CPR is important. The purpose of this study is to provide basic data for developing education that strengthens CPR performance in the future by examining inactive nurses' CPR knowledge, attitude, performance confidence, device discomfort, continued use intention, and educational achievement. The final subjects of this study were 88 inactive nurses residing in B city. The study period was from June 23, 2020 to December 24, 2020. The collected data were analyzed by descriptive statistics and Pearson correlation using SPSS WIN 24.0 program. After obtaining the subject's consent for the study, an inactive nurse who understood the purpose of the study and voluntarily consented to the study participated. To investigate the perception of experience, the subjects watched 360-degree virtual reality contents about CPR in the hospital using HMD. The data of this study were analyzed using SPSS WIN 22.0.program. As a result of this 360-degree study on CPR in the hospital, the average score for the inactive nurses on CPR knowledge was 12.70±3.43, the average score for performance confidence was 6.04±2.45, and the average score for attitude was 4.63±0.80. As a result of experience recognition of 360-degree virtual reality contents for CPR in hospitals, the average score for device discomfort was 4.01±0.94, the average score for continued use intention was 2.07±0.85, and the average score for educational achievement was 2.11±0.79. As a result of correlation analysis, educational achievement and continued use intention were significantly positively correlated (r=.77, p<.001). Based on the results of this study, in order to strengthen the CPR performance capability of inactive nurses in emergency situations, it is necessary to increase CPR knowledge and confidence in performing CPR, and to cultivate a positive attitude toward performing CPR. In addition, it is necessary to implement CPR simulation education based on patient cases by applying content that considers educational achievement and continuous use intention.

• 가정간호학회지
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• 제26권3호
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• pp.329-340
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• 2019

Purpose: This study aimed to provide basic data necessary to develop education programs and educational services for home care by investigating the degree of patient and family education among home health care nurses. Methods: Data collection was carried out with 145 people from 47 institutions that agreed to participate in the research. A total of 128 questionnaires were received, of which 122 were analyzed. Data were analyzed using SPSS 12.0. Results: The item on which education was most frequently delivered was intravenous injection speed control (66.4%), whereas the item requiring the longest teaching period was pressure ulcer care. The average degree of impediment perceived by home care nurses was 2.82 out of 5. Conclusion: Medical institutions should develop educational materials and programs that reflect the characteristics and degree of home health care needed. Repeated research, including that by medical institutions, on the degree and impeding factors related to patient and family education performance of home health care nurses should be conducted. Moreover, medical institutions should investigate the nursing and educational needs of patients and families who received home health care service.