• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 1999년도 추계학술발표대회 논문집
• /
• pp.168-171
• /
• 1999

For the axial crushing tests of various shape of tubes, it was reported that composite tubes need trigger mechanism to avoid brittle failure. In this study, static axial crush tests were performed with the new aluminum/GFRP hybrid tubes. Glass/Epoxy prepregs were wrapped around aluminum tube and co-cured. The failure of hybrid tube was stable and progressive without trigger mechanism, and specific energy absorption was increased to maximum 34% in comparison with aluminum tube. Effective energy absorption is possible for inner aluminum tube because wrapped composite tube constrain the deflection of aluminum tube and reduce the folding length. The failure of hybrid composite tube was stable without trigger mechanism because inner aluminum tube could play the role of crack initiator and controller. Aluminum/Glass-Epoxy hybrid tube is suitable for the vehicle front structure due to effective energy absorption capability, easy production, and simple application for RTM process.

• 한국자동차공학회논문집
• /
• 제15권5호
• /
• pp.112-117
• /
• 2007

With the Euro-4 regulation coming into effect, the domestic car industry is forced to look for newer options to reduce NOX in the exhaust. EGR(Exhaust Gas Recirculation) Cooler is an effective method for the reduction of NOX form a diesel engine. High efficiency, low pressure loss and compactness are desirable features of an EGR Cooler. The cooling performance of EGR depends on the shape of tubes and the location of the entrance and exit. This paper reports the computational work conducted to estimate the performance of EGR cooler with three different cross section tubes and a triangular spiral tube. Three dimensional computation results show that the triangular tube is more effective than circular and rectangular tube. The most effective geometry is a triangular spiral tube with offset inlet and outlet locations.

• 소성∙가공
• /
• 제8권5호
• /
• pp.520-526
• /
• 1999

In this study a practical formula based on the experime수 랙 the estimation of load in the non-circular tube extrusion with the mandrel is proposed by using the effective extrusion ratio. Through some experiments for the several shaped sections, the coefficients of the empirical equation are determined by ticine as a model material at room temperature. The proposed empirical formula for the estimation of extrusion load will be applicable to the non-steady state as well as steady state for the extrusion of various shaped tubes from hollow billets.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2002년도 학술대회지
• /
• pp.697-698
• /
• 2002

The dispersion of an aerosol bolus in acinus is analyzed numerically. Model geometry is a straight duct surrounded by an axisymmetric semicircular annulus which is expanding or contracting with breathing. Unsteady Wavier-Stokes equation is solved by CFX-F3D, an FVM commercial code and the trajectory of massless particle Is computed by Lagrangian method. For steady flow with no wall motion, mean velocity of aerosol bolus in alveolated duct is a little smaller than that in straight duct and dispersion in alveolated duct is comparable with the dispersion in straight tube. For expanding duct mean velocity of aerosol bolus approaches half of that in straight tube and effective diffusivity is smaller than that of straight tube. For contracting duct mean velocity of aerosol bolus becomes slightly larger than that in straight tube and effective diffusivity is comparable with the case of straight tube.

• 한국자동차공학회논문집
• /
• 제8권6호
• /
• pp.208-219
• /
• 2000

In this study, static axial crush tests were performed with the new aluminum/GFRP hybrid tube. Glass/Epoxy prepregs were wrapped around an aluminum tube and co-cured. The failure of the hybrid tube was stable and progressive without trigger mechanism, and specific energy absorption was increased to the maximum of 33% in comparison with the aluminum tube. Effective energy absorption is possible for an inner aluminum tube because a wrapped composite tube constrains the deflection of an aluminum tube. The failure of a hybrid composite tube was stable without trigger mechanism because the inner aluminum tube could play the role of the crack initiator and controller. Mean crushing load could be calculated by modifying the plastic hinge collapse model for hybrid materials. The predicted results by this analytical model showed good agreement with the experimental results. It can be said that Aluminum/Glass-Epoxy hybrid tube is suitable for the vehicle front structure because this hybrid tube shows effective energy absorption, easy production, and simple application capability for RTM process.

• Journal of Chest Surgery
• /
• 제26권8호
• /
• pp.664-666
• /
• 1993

A technique for insertion of a long silicone T-tube in patient with critical stenosis and high-risk resection and primary anastomosis of long segment of the distal trachea is presented. It was not easy to insert a long T-tube by existing methods because of flexibility of a T-tube and tightness of stenosis. So we used a silastic endotracheal tube and guiding wire as stylet of a T-tube. During insertion, ventilation was normally maintained through the lumen of endotracheal tube. This provided rapid relief from airway obstruction and asphyxation and is a easy, safe and effective method to restore patency of the major airways.

• 한국태양에너지학회 논문집
• /
• 제25권1호
• /
• pp.97-104
• /
• 2005

A one-dimensional heat transfer model for the vertical borehole system is derived in this study to predict the thermal behavior of the system and surrounding soil. In this model the U-tube is replaced with one effective tube of effective diameter which is surrounded by concentric grout region. All thermal resistances of borehole are counted in the grout region with effective thermal conductivity of grout. Effective thermal conductivity of grout and sand are calculated through parameter estimation. The validity of this model is accomplished through comparison of the predicted temperature profiles of the model with experimental data.

• 한국방사선학회논문지
• /
• 제17권4호
• /
• pp.507-514
• /
• 2023

이 연구의 목적은 유방촬영의 X-선 빔에서 유효광자에너지를 쉽게 계산할 수 있는 계산식을 구하는데 있다. X2 MAM Sensor를 사용하여 각각의 설정관전압에 대하여 측정관전압을 얻었다. 알루미늄 여과체의 알루미늄에 대한 질량감쇠계수는 각각의 측정관전압 X-선 빔에서 반가층 측정으로부터 구하였다. 각각의 측정관전압 X-선 빔으로부터 구하여진 알루미늄의 질량감쇠계수는 NIST로부터 얻어진 광자에너지별 알루미늄의 질량감쇠계수에 대응시켰다. 일치하는 질량감쇠계수에 대응하는 광자에너지가 유효광자에너지로 결정되었다. 결정된 유효광자에너지의 계산식은 Origin pro 2019b 통계프로그램에서 각각의 측정관전압에 대한 유효광자에너지를 다항식으로 정합하여 y=28.98968-1.91738x+0.07786x²-0.000946717x³으로 얻었다. 여기서 x는 측정관전압이고, y는 유효광자에너지이다. 이 연구에서 얻어진 유방촬영 X-선 빔의 유효광자에너지의 계산식은 임상에서 X-선 빔과 어떤 물질과의 상호작용 계수를 구하는데 아주 유용하게 사용될 수 있을 것으로 사료된다.

• 한국콘텐츠학회논문지
• /
• 제14권1호
• /
• pp.356-363
• /
• 2014

소아 CT 촬영시 피폭선량을 저감시킬 수 있는 조건을 찾기 위하여 pediatric phantom을 이용하여 소아 방사선량을 비교 분석하였다. 관전류변동제어(tube current modulation:TCM) 방식과 low dose CT protocol(LDCTP)에 따라 소아 검사를 시행하였으며, 검사는 brain, chest, abdomen-pelvis 부위를 전산화 단층촬영 장치를 이용한 3개의 검사 프로토콜을 사용하였다. 거의 모든 MDCT 장치는 volume CT dose index(CTDIvol), dose length product(DLP)와 유효선량 평가 결과를 기록, 보관하고 있으며, 이러한 정보들은 환자들의 방사선 노출 및 위험도를 평가하는 데 필수적이다. 방사선 노출 위험도를 감소시키기 위해서 적정화 및 정당화 원칙을 반드시 준수해야 한다. 관전압(kV)에 따른 TCM 방식을 사용하였을 경우 kV가 낮아질수록 유효선량이 낮아지는 경향을 나타내었으며, low dose CT protocol을 사용한 경우가 유효선량이 상대적으로 더 적은 것을 알 수 있었다. 또한 평균 유효선량은 brain, chest, abdomen-pelvis CT의 결과가 독일의 reference dose 보다 각각 47%, 13.8%, 25.7%로 더 낮게 나타났고. 영국의 reference dose와 비교해도 55.7%, 10.2%, 43.6%에 불과했다. 결론적으로 선량 감소를 위해 주의할 것은 body-weight based tube current adaption을 포함한 TCM, 그리고 LDCTP 등 모든 선량 감소 방안을 이용하여야 한다.

• Nuclear Engineering and Technology
• /
• 제51권6호
• /
• pp.1650-1657
• /
• 2019

Fluidelastic instability and nonlinear dynamics of tube bundles is a key issue in a steam generator. Especially, once the post-instability motion of the tube becomes larger than the clearance gap to other tubes, effective contact or impact between the tubes under consideration and the other tube inevitable. There is seldom theoretical analysis to the nonlinear dynamic characteristics of a tube array in two-phase flow. In this paper, experimental and numerical studies were utilized to obtain the critical velocity of the flow-induced instability of a rotated triangular tube array. The calculation results agreed well with the experimental data. To explore the post-instability dynamics of the tube array system, a Runge-Kutta scheme was used to solve the nonlinear governing equations of tube motion. The numerical results indicated that, when the flow pitch velocity is larger than the critical velocity, the tube array system is undergoing a limit cycle motion, and the dynamic characteristics of the tube array are almost similar for different void fractions.