• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.885-890
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• 2006

This study presents analysis results for the hybrid system combining solid oxide fuel cell and gas turbine. Two different system layouts(an ambient pressure system and pressurized system) are considered and their design performance are comparatively investigated taking into account critical design factor, the most critical parameter such as turbine inlet temperature, gas turbine pressure ratio, temperature difference at the fuel cell and fuel cell operating temperature are considered as design constraints. Performance variations according to system layout and design parameters are examined in energetic view point.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2839-2846
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• 2021

In this study, experiments of downward-facing flow boiling were conducted to investigate material effects on CHF. Experiments were conducted using aluminum, copper, and carbon steel. It was found that different materials had different CHFs. Aluminum has the biggest CHF while copper has the lowest CHF for each mass flux. After experiment, surface wettability increased and surface became rougher, which was probably due to the oxidation process during nucleate boiling. The CHF difference is likely to be related to the surface wettability, roughness and thermal effusivity, which influences the bubble behavior and in turn affects CHF. Further studies are needed to determine which factor is dominant.

• Design & Manufacturing
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• 제13권1호
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• pp.42-47
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• 2019

Nucleate boiling heat transfer is one of the most important phenomenon in the various industries. Especially, critical heat flux (CHF) refers to the upper limit of the pool boiling heat transfer region. Therefore, many researchers have found that CHF can be significantly increased by adding very small amounts of nanoparticles. In this study, the CHF and heat transfer coefficient were tested under the pool boiling state using copper and multi wall carbon nanotube nanoparticles. The results showed that two different types of nanoparticles deposited on the surface of two specimens made of the same material increased the heat flux in the nanoparticles with high conductivity, and there was no difference in the critical heat flux when the same material nanoparticles were deposited on the two different specimen surfaces.

• 한국기계가공학회지
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• 제21권5호
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• pp.53-60
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• 2022

In this study, the conceptual design and performance evaluation of a personal air vehicle (PAV) is presented, which is a potential futuristic individual transportation. The blade element theory (BET) is employed to compute a rotational velocity. A computational fluid dynamics (CFD) simulation is performed to investigate the difference in the thrust performance in the rotor axis distance of a quad-copter PAV in hovering. Modal analysis is performed to create a Campbell diagram to investigate critical speed. Consequently, a quad-copter PAV changes the aerodynamics thrust and critical velocity according to the rotor axis distance.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2864-2872
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• 2023

The criticality problem in this study is studied with the recently investigated the Anlı-Güngör scattering function. The scattering function depends on the Legendre polynomials as the Mika scattering function, but it includes only one scattering parameter, t, and its orders. Both Mika and Anlı-Güngör scattering are the same for only linear anisotropic scattering. The difference appears for the quadratic scattering and further. The analytical calculations are performed with the H_N method, and the numerical results are calculated with Wolfram Mathematica. Interpolation technique in Mathematica is also used to approximate the isotropic scattering results when t parameter goes to zero. Thus, the calculated results could be compared with the literature data for isotropic scattering.

• Tuberculosis and Respiratory Diseases
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• 제48권2호
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• pp.260-267
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• 2000

거대세포성 간질성 폐렴은 경금속 도구를 이용한 절삭, 연마공정에서 발생하는 경금속 분진을 흡입하여 발생하는 산업성 폐질환으로 알려져 있다. 저자들은 이러한 특징적인 경금속분진에 대한 노출력이 없이 발생하였던 거대세포성 간질성 폐렴을 수술적 폐생검과 폐조직내 금속 함유량 분석을 통해 진단하였기에 보고 하는 바이다.

• Tuberculosis and Respiratory Diseases
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• 제68권1호
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• pp.1-5
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• 2010

Background: To analyze the result of $^{18}F-FDG$ positron emission tomography (PET) in patients with a concomitant malignancy and tuberculoma in a tuberculosis (TB)-endemic area. Methods: Twelve patients with a concomitant malignancy and tuberculoma, who underwent whole-body $^{18}F-FDG$ PET, were evaluated retrospectively. The maximal standardized uptake values (SUVmax) of the malignancy and tuberculoma were compared. In 6 patients, $^{18}F-FDG$ PET was repeated during the anti-TB treatment and the changes in SUVmax were analyzed. Results: Of the 12 patients, 10 were male. The mean age was $67.2{\pm}7.9$ years. Tuberculomas were located in the lung (n=10) and lymph nodes (n=2), and tumors were located in the lung (n=6), colon (n=3), stomach (n=1), ovary (n=1) and liver (n=1). Although the mean SUVmax of malignant lesions was higher than that of tuberculomas ($5.2{\pm}3.2$ vs $3.5{\pm}2.0$), the difference was not significant. In 4 patients, the SUVmax was higher in the tuberculoma than the tumor. After anti-TB treatment in 6 patients, the mean SUVmax of the tuberculomas decreased significantly, from $3.5{\pm}2.0$ to $1.6{\pm}0.9$ (p=0.028). Conclusion: In patients with a concomitant malignancy and tuberculoma, SUVmax alone could not differentiate between them. However, $^{18}F-FDG$ PET may be useful in monitoring the response to anti-TB treatment.

• Tuberculosis and Respiratory Diseases
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• 제82권3호
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• pp.234-241
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• 2019

Background: The utility of computed tomography (CT) in the differential diagnosis of patients with chronic obstructive pulmonary disease (COPD) exacerbation remains uncertain. However, due to the low cost associated with CT scan along with the impact of Koreas' health insurance system, there has been a rise in the number of CT scans in the patients with initial diagnosis of COPD exacerbations. Therefore, the utility of CT in the differential diagnosis was investigated to determine whether performing CT scans affect the clinical outcomes of the patients with an initial diagnosis of COPD exacerbation. Methods: This study involved 202 COPD patients hospitalized with an initial diagnosis of COPD exacerbation. We evaluated the change in diagnosis or treatment after performing a CT scan, and compared the clinical outcomes of patient groups with vs. without performing CT (non-CT group vs. CT group). Results: After performing CT, the diagnosis was changed for two (3.0%) while additional diagnoses were made for 27 of the 64 patients (42.1%). However, the treatment changed for only one (1.5%), and six patients (9.3%) received supplementary medication. There were no difference in the median length of hospital stay (8 [6-13] days vs. 8 [6-12] days, p=0.786) and intensive care unit care (14 [10.1%] vs. 11 [16.7%], p=0.236) between the CT and non-CT groups, respectively. These findings remained consistent even after the propensity score matching. Conclusion: Utility of CT in patients with acute COPD exacerbation might not be helpful; therefore, we do not recommend chest CT scan as a routine initial diagnostic tool.

• Tuberculosis and Respiratory Diseases
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• 제84권1호
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• pp.46-54
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• 2021

Background: The aim of this study was to investigate inhaler device handling in elderly patients. Inhaler devices with respect to misuse and error correction were also compared. Methods: Inhaler use technique was assessed using standardized checklists at the first visit and 3-month follow-up visit after retraining. The primary outcome was difference in the acceptable use ratio among inhaler devices. Secondary outcomes included differences in error correction, the most common step of misuse, and factors affecting the accuracy of inhaler use. Results: A total of 251 patients (mean age, 76.4 years) were included. The handling of 320 devices was assessed in the study. All patients had been trained before. However, only 24.7% of them used inhalers correctly. Proportions of acceptable use for Evohaler, Respimat, Turbuhaler, Ellipta, and Breezhaler/Handihaler were 38.7%, 50.0%, 61.4%, 60.8%, and 43.2%, respectively (p=0.026). At the second visit, the acceptable use ratio had increased. There were no significant differences among inhaler types (Evohaler, 63.9%; Respimat, 86.1%; Turbuhaler, 74.3%; Ellipta, 64.6%; and Breezhaler/Handihaler, 65.3% [p=0.129]). In multivariate analysis, body mass index, Turbuhaler, and Ellipta showed positive correlations with acceptable use of inhalers, whereas Chronic Obstructive Pulmonary Disease Assessment Test score showed a negative correlation. Conclusion: Although new inhalers have been developed, the accuracy of inhaler use remains low. Elderly patients showed more errors when using pressurized metered-dose inhalers than using dry powder inhalers and soft-mist inhalers. However, there were no significant differences in misuse among inhaler devices after individual training. Results of this study suggests that repeat training is more important than inhaler type.

• 치위생과학회지
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• 제11권6호
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• pp.543-551
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• 2011

치위생(학)과 학생의 비판적 사고 성향과 관련 요인을 파악하기 위해 3년제 치위생과 및 4년제 치위생학과 학생 941명을 대상으로 2011년 5월 3일부터 6월 5일까지 자기기입식 설문조사를 실시하고 최종적으로 909부를 분석하였다. 비판적 사고 성향 측정도구는 윤의 간호 대학생을 대상으로 조사하고 개발한 도구를 이용하였으며, 지적열정, 신중성, 체계성, 자신감, 객관성, 지적공정성, 건전한 회의 등 7개 요인의 27개 문항으로 구성되었다. 요인분석, 신뢰도 분석, 중회귀 분석, 다변량 분산분석 등을 통해 분석한 결과 다음과 같은 결론을 얻었다. 1. 본 연구에 사용된 비판적 사고 성향 측정도구는 치위생(학) 학생 대상의 평가에 적합한 것으로 나타났다. 요인분석 결과 원 연구와 동일한 7개 요인이 추출되었으며, 각 요인에 적재된 문항도 원 연구와 일치하였고, 전체 분산의 51.34%를 설명하였다. 내적일관성 신뢰도(Cronbach's alpha)수는 0.82로서 원 연구결과와 유사하였고, 7개 하위요인의 신뢰도 역시 원연구결과와 유사하였다. 2. 학제에 따른 비판적 사고 성향 총합척도 및 7개 하위척도 점수의 차이를 비교하기 위해 독립표본 t 검정을 실시하였다. 비판적 사고 성향 총합척도의 평균은 차이가 나타나지 않았다. 하위척도는 지적 공정성을 제외한 6개 평균이 차이가 없었다. 3. 다중회귀 분석 결과 대인관계 만족도(p<0.001)와 전공 만족도(p<0.001)가 비판적 사고 성향에 영향을 미치고 있다($R^2=0.115$, F=11.896, p=0.000). 4. 다변량 분산분석 결과 대인관계 만족도 수준별 집단에 따라 다변량 통계량이 유의한 차이가 나타났다(Pillai의 트레이스=0.075, F(14, 1782)=4.979, p<0.001). 또한 전공 만족도 수준별 집단에 따라 다변량 통계량이 유의한 차이가 있었다(Pillai의 트레이스=0.035, F(14,1728)=2.257, p=0.005). 개체-간 효과 검정 결과, 대인관계 만족도 수준별 집단은 비판적 사고 성향의 하위요인 중 신중성을 제외한 6개 요인에서 유의한 차이가 나타났다. 전공만족도 수준별 집단은 비판적 사고 성향 하위요인 중 지적 열정(p=0.002), 체계성(p=0.013), 지적 공정성(p=0.003)은 유의한 차이가 있지만, 나머지 요인은 차이가 나타나지 않을 수 있다. 결론적으로, 치위생(학)과 학생의 비판적 사고 성향은 대인관계 및 전공만족도에 따라 차이가 있으나, 학제와 학년에 따른 차이가 나타나지 않아, 학생의 사고력 증진을 위한 교육 프로그램 개발이 필요한 것으로 나타났다.