• 한국방사선학회논문지
• /
• 제15권6호
• /
• pp.869-875
• /
• 2021

이 연구의 목적은 CT 모의치료장치에서 발생된 X-선 빔의 유효에너지 계산식을 유도하는데 있다. 90, 120, 140 kVp X-선 빔 하에서, AAPM CT 성능 팬텀의 CT수 교정 삽입부는 CT 모의치료장치로 5번 스캔하였다. 폴리에틸렌, 폴리스틸렌, 물, 나일론, 폴리카보네이트, 그리고 아크릴의 CT수는 각각의 CT 슬라이스 영상에 대하여 측정하였다. 단일 관전압 하에서 측정된 CT수 평균값과 미국표준기술연구소의 자료로부터 계산된 각각의 광자에너지에 대응하는 선감쇠계수들을 선형정합하였다. 얻어진 상관계수들 중 최대값을 갖는 광자에너지를 유효에너지를 결정하였다. 이와 같은 방법으로, 각각의 관전압에서 생성된 X-선 빔의 유효에너지를 결정하였다. 결정된 유효에너지(y)들와 관전압(x)들을 선형정합하여 유효에너지 계산식으로서 y=0.33026x+30.80263을 유도하였다.

• International Journal of Aeronautical and Space Sciences
• /
• 제15권2호
• /
• pp.205-211
• /
• 2014

The design parameters to affect the cooling capacity of a cryocooler were examined with the application of numerical modeling to optimize an inertance pulse tube cryocooler. This modeling includes the regenerator, pulse tube, inertance tube, gas reservoir, and heat exchangers. One-dimensional modeling on strings of acoustic and thermoacoustic elements was applied to compare the design parameters. The diameter and length of the pulse tube can significantly affect the cooling capacity and efficiency. The aftercooler was optimized by maintaining a certain size. The efficiency also improved as the length of inertance tube and volume of gas reservoir are increased. It was confirmed that effective design parameters are critical to the performance of an inertance pulse tube cryocooler considering the comparison of the dimensions of each part to optimize its cooling power and efficiency.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 추계학술대회
• /
• pp.401-411
• /
• 2003

Tube expanding process is for combining a heat-sink plate with hair-pins (Cu-tube) through plastic deformation. The two parts, i. e. , heat-sink plate and hair-pins are they components of a heat-exchanger for an air conditioner. This paper presents the analysis and dynamic modeling of a high-speed tube expander which integrates transfer of parts, fixing of parts, and tube expanding into one process. The 3-dimensional modeling of all the parts for the tube-expander was constructed using CATIA$\circledR$. then the CATIA$\circledR$ models are transferred into visuaINastran$\circledR$ to execute the 3-dimensional animation for checking prescribed cycle-time. The technique presented in this paper has been shown to be effective as a priori tool for verifying the design of a high-speed tube expander.

• Journal of Chest Surgery
• /
• 제48권5호
• /
• pp.378-379
• /
• 2015

Mediastinitis is a life-threatening disease, and effective drainage is needed to treat mediastinitis with abscess formation. We recommend an alternative drainage method using chest tube binding with a Silastic Penrose drainage tube. The use of a Silastic Penrose drainage tube may help to manage mediastinitis with abscess formation. This method facilitates effective draining and prevents tissue adhesion.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
• /
• pp.96-96
• /
• 2010

Magnesium alloy is being used for structural material since it has high specific strength. Tubular shape was effective way for enhanced structural design. To manufacture the tube, it is necessary to weld the butted joint of both tubular formed sides. But the magnesium alloy was hardly welded with conventional welding processes. The laser welding was effective way to joint magnesium alloys because it had high weld strength and productivity compare with other welding processes. In this study, magnesium alloy sheets was formed at elevated temperature to tubular shape and welded with laser. Consequently, the magnesium alloy tube was making successful with warm forming and laser welding and bicycle frame was making with it.

• 설비공학논문집
• /
• 제11권5호
• /
• pp.692-699
• /
• 1999

The vortex tube is a sample device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. The phenomena of energy separation through the vortex tube were investigated experimentally, to see the effects of the number of nozzle holes on the energy separation. The experiment was carried out with the number of nozzle holes from 1 to 10 by varying inlet pressure and cold mass fraction. The experimental results were indicated that the effective number of nozzle holes for the best cooling performance was found as 4. Also, to find effective use in a given operation conditions, the temperature difference of cold air and the cooling capacity of vortex tube was compared. The result is that cooling capacity was more important than temperature difference of cold air.

• Bulletin of the Korean Chemical Society
• /
• 제32권6호
• /
• pp.1970-1974
• /
• 2011

The effects of convection on the measurement of the diffusion coefficients of liquids by the pulsed gradient spin echo (PGSE) NMR method at low temperature are discussed. To examine the generation of convective flows, we used four different types of sample tubes in the diffusion measurements with temperature variation; a normal 5 mm NMR tube, a Shigemi tube, an ELISE type tube, and a capillary tube. Below room temperature, the calculated diffusion coefficients of chloroform in 5 mm o.d. type tubes increased with decreasing temperature, while those in the capillary tube decreased linearly. The convective flow was found to be significant even at low temperature and it seemed to be mainly induced by the transverse temperature gradient. It was also found that the capillary tube was most appropriate to measure the diffusion coefficients, since its small diameter is effective in suppressing the convective flows at both high and low temperatures.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2005년도 연구개발 발표회 논문집
• /
• pp.825-828
• /
• 2005

Experimental and numerical study was done to confirm the effect of the flexible tube in pipeline on transient flow oscillation. Experiment was made for a pipeline with and without deformable flexible tube using a single pumping system of main stainless pipe. The wave speeds of main pipe and flexible tube were calculated from the pipe material properties, structures, and boundary conditions. Time dependent pressure fluctuations were calculated for the pipeline using the simple and the Kelvin-Voigt viscoelastic models for the deformation of main pipe and flexible tube. Pressure calculated by the Kelvin-Voigt viscoelastic model showed better agreement with measured one than pressure by the simple model. Experimental and numerical results show that the maximum pressure as well as amplitude of pressure oscillation was decreased by inserting short flexible tube in pipeline. Hence, inserted short flexible tube to pipeline was found to be effective for the suppression of strong pressure oscillation. Moreover, the wave speed in pipe was discussed based on numerical and experimental results.

• 소성∙가공
• /
• 제31권3호
• /
• pp.143-150
• /
• 2022

The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.

• KSTLE International Journal
• /
• 제10권1_2호
• /
• pp.33-36
• /
• 2009

The nuclear steam generator is composed of a bundle of tubes. The length of these tubes is very long, but their diameter is small. Fluid exists inside of the steam generator and its flow causes vibration, therefore these tubes are supported by anti-vibration bars. The wear damage due to the vibration is known as fretting wear, which should be minimized to ensure the safety of the plants. Research needs to be done about decreasing the amount of fretting wear. Hard coatings have proven to be very effective in reducing the amount of wear. The commercial coatings of TiN and CrN have excellent wear resistance and are used to protect the Inconel tube from fretting wear. The tube-on-flat type tester was used for conducting the fretting wear tests. It was found that the wear amounts of the coated tubes decreased depending on the coating thickness. CrN was found to be very effective in reducing the wear, while the wear amounts were dependent on the coating thickness in the case of TiN and a thick coating of TiN was very effective on wear resistance.