• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.413-421
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• 2007

In this paper, the performance characteristics of heat pump system using a new refrigerant subcooling system designed for the study, are introduced. The new heat pump system have the ice storage tank at the outlet of condenser. The experimental apparatus is a well-instrumented water/water heat pump which consisted of working fluid loop, coolant loop, and ice storage tank. The experiment parameters of subcooling ranged as the evaporating temperature from $-5^{\circ}C$ to $8^{\circ}C$, the condensing temperature from $30^{\circ}C$ to $35^{\circ}C$. The test of the ice storage was carried out at evaporating temperature of $-10^{\circ}C$ and the ice storage mode is Ice-On-Coil type. The working fluid was R-22 and the storage materials were city-water. The test results obtained were as follows; The refrigerant mass flow rate and compressor shaft power were unchanged by the degrees of subcooling, that is, they were independent of degrees of subcooling. The cooling capacity of the new heat pump system increase as the evaporating temperature and subcooling degrees increase and is higher by $25{\sim}30%$, compared to the normal heat pump system. The COP of the new heat pump system increases as the degrees of subcooling and evaporating temperature increase and is higher by 28% than that of the normal heat pump system.

• 한국산업보건학회지
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• 제27권2호
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• pp.123-129
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• 2017

Objectives: The purpose of this study is to enhance the application of analytical method of polar solvents(alcohols) by GCOTC (gas chromatography open tubular column) through the system suitability test(SST) to estimate the whole chromatographic system performance(integral part). Methods: To perform the SST, carried out repeatability(n=6) as analytical method of polar solvents by GCOTC, got the retention time($t_R$), standard deviation(${\sigma}_{n-1}$) of $t_R$, baseline width($w_b=4{\sigma}_{n-1}$) and calculated dead time($t_m$) by $v_m=d^2{\pi}L(f/4)$ and $v_m=t_m$ x flow rate. Results: In this experiment, obtained the basic data, there were $t_m=2$ min, methanol($t_R=3.569$, ${\sigma}_{n-1}=0.01$, $w_b=0.04$), ethanol ($t_R=3.892$, ${\sigma}_{n-1}=0.004$, $w_b=0.016$), isopropanol($t_R=4.209$, ${\sigma}_{n-1}=0.004$, $w_b=0.016$). By using these data, calculated the corrected retention time($t_R{^{\prime}}$), capacity factor(k), separation factor(${\alpha}$), number of theoretical plate(n) and resolution($R_s$) for SST and got the good results. Conclusions: Through the SST, could reconfirm the whole chromatographic performance system(integral part) for analytical method of polar solvents by GCOTC. Therefore, this analytical method expect to be widely applied at the related areas.

• 한국해양공학회지
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• 제23권5호
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• pp.25-31
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• 2009

The most important component of wind turbine is rotor blades. The developing method of wind turbine was focused on design of rotor blade. By the way, the design of a rotating body is more decisive process in order to adjust the performance of wind turbine. For instance, the design allows the designer to specify the wind characteristics derived by topographical map. The iterative solver is then used to adjust one of the selected inputs so that the desired rotating performance which is directly related to power generating capacity and efficiency is achieved. Furthermore, in order to save the money for manufacturing the rotor blades and to decrease the maintenance fee of wind power generation plant, while decelerating the cut-in speed of rotor. Therefore, the design and manufacturing of rotating body is understood as a substantial technology of wind power generation plant development. The aiming of this study is building-up the profitable approach to designing of rotating body as a system for the wind power generation plant. The process was conducted in two steps. Firstly, general designing and it’s serial testing of rotating body for voltage measurement. Secondly, the serial test results above were examined with the CFD code. Then, the analysis is made on the basis of amount of electricity generated by rotor-blades and of cut-in speed of generator.

• 대한정형도수물리치료학회지
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• 제20권1호
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• pp.21-26
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• 2014

Background: This study was aimed to determine the effects of deep abdominal muscle exercises (DAME) and thoracic mobility exercises (TME) on pulmonary function. Methods: This study was conducted with 22 college students who are in their 20s and have no problem carrying out activities of daily living. All subjects were randomly assigned to either the DAME group (11) or the TME group (11) to undertake the exercises for 2 weeks. To measure pulmonary function of subjects, forced vital capacity (FVC), forced exploratory volume in 1 second (FEV1) and peak expiratory flow (PEF) were measured using chest graph. Chest expansion of subjects was also measured with tape ruler. These measurements were performed on the first day before the exercise program started and on the next day after the 2-week exercise program was completed. A paired-t test was performed to compare the differences in pulmonary function before and after the exercise program, and an independent t-test was performed to compare the two groups. Results: The results of this study were as follows: 1) In comparison of pre- and post-exercise changes in the DAME and TME groups, both groups showed significant increase in chest expansion and PEF after the exercise program, compared with the baseline data (p<.05). Both groups also demonstrated improvements in FVC and FEV1 after the exercise program, compared with the baseline data. However, the differences were not statistically significant (p>.05). 2) The comparison of the DAME and TME groups revealed no significant differences in chest expansion, FVC, FEV1 and PEF (p>.05). Conclusion: It is therefore concluded that both DAME and TME were effective in improving pulmonary function.

• 한국철도학회논문집
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• 제11권3호
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• pp.317-325
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• 2008

최근 연구결과 레일연마 및 장대레일화로 누적통과톤수에 의한 레일교체기준의 연장이 가능한 것으로 보고되었다. 본 연구에서는 현재 도시철도에서 사용 중인 대표 궤도구조에 대해 실운행 열차하중에 의한 궤도의 동적 응답을 분석하여 현 궤도의 상태평가를 하였으며 궤도의 상태 변화에 따른 레일의 부담력을 검토하였다. 또한, 측정된 응력파형을 Rainflow Count Method를 이용하여 응력히스토그램을 작성하고 등가응력을 상정하여 신규 레일 용접부의 S-N 선도에 적용함으로써 노후레일의 누적피로손상도 및 휨 피로수명을 산정하였다. 최종적으로 본 연구에서는 궤도구조 및 상태를 고려한 레일교체기준의 개정을 제안하고자 하였다.

• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.25-31
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• 2011

The performance of fan for engine room of ship is absolutely important when it take into consideration work efficiency, work condition, and the performance of various equipments. Fan performance test should be carried out during sea trial to satisfy owner's requirement as above mentioned. We have considered various values to affect fan test result. In here, various values are to be silencer, fan inlet shape, and arrangement of fan room. In general, the shapes of fan inlet is overall circular type because of the shapes of axial fan. So, all vessels built at SHI have been applied fan inlet of circular type. And now, in order to reduce sound of noise from supply fan, big silencer often has been installed at high value vessels. In this case, the capacity of supplied air can be insufficient due to silencer which is an obstructer about air flow. In this paper, we have studied the performance of fan through comparison between a circular shape and a square shape of fan inlet. We also compare with CFD results and experimental results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.424-426
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• 2008

초소형 가스터빈에 사용되는 소형 고속 구름베어링의 연료윤활 특성을 실험적으로 조사하였다. 윤활유로는 항공용 가스터빈에서 사용되는 MIL-PRF-7808 터빈오일과 항공용 가스터빈의 추진연료로 사용되는 JP-8 연료를 사용하여 운용특성을 비교하였고, 시험용 베어링으로는 내경 17 mm의 깊은 홈(deep groove) ball bearing과 내경 20 mm의 원통형(cylindrical) roller bearing을 사용하였다. 베어링의 연료윤활에 따른 특성을 비교하기 위하여 오일 및 연료를 공급하며 고속베어링 시험을 수행할 수 있는 시험 장치를 개발하여 하중, 냉각공기 온도, 윤활유량 및 회전속도를 변화시키면서 시험을 수행하였다. 30,000 rpm에서 70,000 rpm까지 회전속도를 변화시키면서 시험한 결과 깊은 홈 볼베어링은 축하중과 회전속도가 증가하는 경우 베어링 케이지에 마모가 발생하였으며 마모상태는 오일윤활보다 연료윤활시 마모가 더 많이 발생하였고 본 베어링의 속도한계인 59,000 rpm까지는 연료 윤활로 운용이 가능하다는 것을 확인할 수 있었다. 연료윤활의 경우가 오일윤활의 경우보다 베어링 온도가 더 낮은 것을 알 수 있었는데 이는 베어링의 냉각특성이 연료윤활인 경우가 오일윤활의 경우보다 더 좋기 때문이라 판단된다. 본 실험을 통하여 소형 항공용 가스터빈의 주축 베어링 윤활방식으로 연료윤활 방식이 적용 가능함을 확인할 수 있었다.

• 대한조선학회논문집
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• 제43권1호
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• pp.15-21
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• 2006

Recently, the attention to large container ships whose size is greater than 10,000 TEU container ship has been increased due to their increasing demand. The large container ship has twin skegs because of the engine capacity and large beam-draft ratio. In this paper, the maneuvering characteristics of a container ship with twin skegs were investigated through 4DOF(four degree of freedom) HPMM(Horizontal Planar Motion Mechanism) test and computer simulation. A mathematical model for maneuvering motion with 4DOF of twin skegs system was established to include effects of roll motion on the maneuvering motion. And to obtain roll-coupling hydrodynamic coefficients of a container ship, 4DOF HPMM system of MOERI which has a roll moment measurement system was used. HPMM tests were carried out for a 12,000 TEU class container ship with twin skegs at scantling load condition. Using the hydrodynamic coefficients obtained, simulations were made to predict the maneuvering motion. Rudder forces of twin-rudders were measured at the angles of drift and rudder. The neutral rudder angles with drift angles of ship was quite different with those of single skeg ship. So other treatment of flow straightening coefficient $\gamma_R$ was used and the simulation results was compared with general simulation result. The treatment of experimental result at static drift and rudder test was very important to predict the maneuverability of a container ship with twin skegs.

• Tuberculosis and Respiratory Diseases
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• 제84권4호
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• pp.274-281
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• 2021

Background: The Korea National Health and Nutrition Examination Survey (KNHANES) is a well-designed survey to collect national data, which many researchers have used for their studies. In KNHANES, although portable spirometry was used, its reliability has not been verified. Methods: We prospectively enrolled 58 participants from four Korean institutions. The participants were classified into normal pattern, obstructive pattern, and restrictive pattern groups according to their previous spirometry results. Lung function was estimated by conventional spirometry and portable spirometry, and the results were compared. Results: The intraclass correlation coefficients of forced vital capacity (FVC) (coefficient, 9.993; 95% confidence interval [CI], 0.988-0.996), forced expiratory volume in 1 second (FEV₁) (coefficient, 0.997; 95% CI, 0.995-0.998), FEV₁/FVC ratio (coefficient, 0.995; 95% CI, 0.992-0.997), and forced expiratory flow at 25-75% (FEF25-75%; coefficient, 0.991; 95% CI, 0.984-0.994) were excellent (all p<0.001). In the subgroup analysis, the results of the three parameters were similar in all groups. In the overall and subgroup analyses, Pearson's correlation of all the parameters was also excellent in the total (coefficient, 0.986-0.994; p<0.001) and subgroup analyses (coefficient, 0.915-0.995; p<0.001). In the paired t-test, FVC, FEV₁/FVC, and FEF25-75% estimated by the two instruments were statistically different. However, FEV₁ was not significantly different. Conclusion: Lung function estimated by portable spirometry was well-correlated with that estimated by conventional spirometry. Although the values had minimal differences between them, we suggest that the spirometry results from the KNHANES are reliable.

• Clinical and Experimental Pediatrics
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• 제52권11호
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• pp.1267-1272
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• 2009

목 적:국내 학동 전기 소아를 대상으로 폐활량 측정법을 시행하여 기존에 제시된 여러 지표를 기준으로 검사 결과의 적정성을 평가함으로써 이 연령대에서의 폐기능 검사의 성공률을 알아보고자 하였다. 방 법:만성 기침이나 천식이 의심되어 내원한 2세 이상 6세 이하의 176명을 대상으로 폐활량 측정법을 시도하여 총 155 명에서 측정 결과를 얻을 수 있었다. ATS/ERS 에서 제시한 기준에 따라 후외삽용적(Vbe)이 80 mL 미만이고 FVC의 12.5% 미만일 때를 시작 기준에 적합하다고 정의하였다. 검사의 반복성을 확인하기 위해 선별한 두개의 유량-용적 곡선에서 FVC, FEV1의 차이를 구하여 FVC와 $FEV_1$의 절대적 차이값이 100 mL 또는 10% 미만인 경우를 적합하다고 정하였다. 검사의 종료에 대한 기준은 학동 전기 연령에서 수치적으로 정의되어 있지 않지만 유량-용적 곡선이 초기에 급격하게 증가해서 후기에 완만하게 감소하는 것을 합당하다고 보았다. 또한 유량-용적 곡선이 적절하게 나온 대상자(107명)를 선별하여 다른 문헌에 발표된 여러 정도 관리 기준에 맞추어 각 항목별로 성공률을 비교하였다. 결 과:전체 폐기능 검사의 성공률은 59% 이었고 연령이 증가할수록 폐활량 측정법의 성공률이 증가하였으며, 특히 3세부터 급격하게 성공률이 증가하였다(2세 14.3%, 3세 53.7%, 4세 65.1%, 5세 69.7%, 6세 70.8%). 폐활량 측정법의 실패 원인으로는 시작 기준에 맞지 않는 경우가 전체의 6.5%, 반복성 기준에 맞지 않는 경우가 12.3% 또 최대 호기량의 부족, 조기 종료 등으로 인해 검사 종료 기준에 맞지 않는 경우가 전체의 31% 로 가장 높았다. 폐활량 측정법 성공군와 실패군을 비교하였을 때 나이에서만 유의한 차이가 있었다(P<0.01). 정도 관리에 대한 몇몇 연구결과에 따라 각 항목별로 성공률을 보았을 때 연령이 증가할수록 성공률도 증가하였다. 결 론:학동 전기 소아에서도 약 60% 정도 폐활량 측정법을 성공적으로 수행하였다. 성공률은 연령에 따라 급격히 변화하므로 각 연령에 적합한 정도 관리 기준을 개발하여 이용한다면 검사의 성공률을 높일 수 있을 것으로 사료된다.