• 대한기계학회논문집B
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• 제36권7호
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• pp.675-681
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• 2012

본 연구는 낮은 회 성분의 함량과 높은 발열량의 특성을 지닌 초청정 석탄의 촤 반응율 특성을 알아보았다. 실험은 DTF(Drop Tube Furnace)를 통해서 다양한 온도조건 하에 산소의 분율을 바꾸어가며 수행하였다. 촤 반응률을 도출하기 위하여 FT-IR을 통해 배기가스(CO, $CO_2$)를 측정하였으며, 이색온도계를 통하여서 입자 온도를 측정하였다. 또한, Arrhenius 경험식을 토대로 초청정 석탄 촤의 활성화 에너지와 빈도인자를 도출하였다. 결과는 초청정 석탄 촤의 반응특성은 온도와 산소 분율이 높아질수록 뚜렷한 증가를 보였고, 초청정 석탄 촤의 활성화 에너지는 역청탄의 수치와 비슷한 값을 보임을 알 수 있었다.

• 핵의학기술
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• 제14권2호
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• pp.208-211
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• 2010

현재 본원은 TFB사의 CA19-9 항체가 bead에 코팅되어있는 CA19-9 IRMA 시약을 사용하고있다. 이번에 TFB사에서 새로 개발된 CA19-9 항체가 polystyrene test tube에 코팅된 CA 19-9 IRMA 시약이 기존 TFB사의 bead를 사용하는 시약을 대체하여 사용할 수 있는지 시약의 성능을 평가하였다. 본원과 서울대학교병원 환자 56명의 검체를 대상으로 하여 TFB사의 기존 bead 방법을 사용한 시약과 새로 개발된 coated tube를 사용한 시약을 비교하여 상관계수와 회귀식을 구하고 coated tube를 사용한 시약의 정밀도, 회수율, 직선성, 민감도, Hook effect 를 확인하였다. 저, 중, 고역가 검체의 검사내 정밀도는 4.1%, 4.0%, 4.2%이고 검사간 정밀도는 7.6%, 4.3%, 7.8%이며 회수율은 모두 $100{\pm}10%$이다. 직선성은 우수하였고 분석적민감도는 0.3U/mL이었으며 9,020,000 U/mL 농도에서는 Hook effect가 나타나지 않았다. 또한 TFB사의 기존 bead를 사용한 방법과 비교하여 상관관계를 분석한 결과, y=0.9185x-0.953, 상관계수 $R^2$=0.9779이었다. 이번 연구를 통해 본원은 TFB사에서 새로 개발된 coated tube CA19-9 IRMA 시약이 검사 시간과 검사 과정에서 간편화되고 검사시 자동화기기를 사용할 수 있으며 기존 bead를 사용한 시약에 대체하여 사용할 수 있다고 판단하였다.

• 대한기계학회논문집B
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• 제24권2호
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• pp.233-240
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• 2000

An experimental study of condensation heat transfer was performed for pure refrigerants HFC32, HFCI25, and HFC134a, and a ternary refrigerant mixture of HFC32/125/134a (23/25/52wt%). The heat transfer coefficients were measured inside a horizontal smooth tube 5.8 mm I.D. and 8.0 m long. The refrigerant temperature at inlet was 40 $^{\circ}C$, and the mass flux was varied from 150 to 400 $kg/m^2s$. As for the pure refrigerants, the heat transfer coefficient of HFC32/125/l34a decreased as the quality decreased. In addition, the heat transfer coefficient of HFC32/l25/134a was about 20 % lower than HFC 134a at a low mass flux but showed no reduction at a high mass flux. The heat transfer coefficient of ternary refrigerant mixtures was 30% lower on the average than that of the pure refrigerant.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.151-154
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• 2002

The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee's total variation diminishing (TVD) scheme is used to solve the unsteady, two-dimensional, compressible, Euler equations. The Mach number $M_{s}$, of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two parallel tubes, the peak pressure produced by the twin-impulse waves and its location strongly depend upon the distance between two parallel tubes, L/d and the incident shock Mach number, $M_{s}$. The predicted Schlieren images represent the measured twin-impulse wave with a good accuracy.

• 동력기계공학회지
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• 제12권5호
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• pp.48-53
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• 2008

Heat exchangers are commonly used in practice in a wide range of application, from heating and air-conditioning system in a household, to chemical processing and power production in a large plant. Heat transfer in a heat exchanger usually involves convection in each fluid and conduction through the wall separating the two fluids. The heat transfer characteristics of tube banks of in-line arrangements of four circular cylinders in a cross flow are compared for a range of tube locations and Reynolds numbers. The in-line pitch ratio was set up in the range of $1.5\leq L/d\leq4.0$, where L is the center to center distance and d the circular cylinder diameter, and in the Reynolds number of $13,000\leq Re\leq50,000$. The local and mean Nusselt numbers were estimated, and then. Subsequently, the heat transfer characteristics of four circular cylinders were found to exhibit a strong dependency upon the cylinder spacing and separation point of their upstream cylinders.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.513-525
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• 2004

This paper reports an experimental study on flow boiling of pure refrigerants R l34a and R l23 and their mixtures in a uniformly heated horizontal tube. The flow pattern was observed through tubular sight glasses with an internal diameter of 10㎜ located at the inlet and outlet of the test section. Tests were run at a pressure of 0.6 MPa in the heat flux ranges of 5-50㎾/㎡, vapor quality 0-100 percent and mass velocity of 150-600㎏/㎡s. Both in the nucleate boiling-dominant region at low quality and in the two-phase convective evaporation region at higher quality where nucleation is supposed to be fully suppressed, the heat transfer coefficient for the mixture was lower than that for an equivalent pure component with the same physical properties as the mixture. The reduction of the heat transfer coefficient in mixture is explained by such mechanisms as mass transfer resistance and non-linear variation in physical properties etc. In this study, the contribution of convective evaporation, which is obtained for pure refrigerants under the suppression of nucleate boiling, is multiplied by the composition factor by Singal et al. (1984). On the basis of Chen's superposition model, a new correlation is presented for heat transfer coefficients of mixture.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.40-43
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• 2003

In this paper, the electric field distribution in dielectric tube with one layer and spherical dielectric(glass) in water was simulated. The reactor was made up of the spherical dielectric that is diameter : 3.0[mm], glass(${\varepsilon}_r$:5) and one glass plate of thickness(2[mm]), ${\varepsilon}_r$(5) as electrode. The discharge gap was 8[mm). Toget more strong electric field, the dielectric constant should be higher comparatively. Using the spherical dielectric for water discharge in dielectric tube, the location of equipotential line was shifting from the interior to the exterior. At real water discharge experimental, $H_2O_2$ was measured higher generated $H_2O_2$ in water at condition of water rate(1[l/min]) and injector than condition of non-injector or 2-3[l/min])

• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1854-1860
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• 2006

Electrochemical behaviors of acetaminophen at a muti-wall carbon nano-tube composite film modified glassy carbon electrode were investigated by cyclic voltammetry, linear sweep voltammetry and chronocoulometry. Compared with that obtained at the unmodified electrode, the peak currents were enhanced significantly, and the oxidation peak shifted towards more negative potential with the reduction peak shifted positively. The peak-to-peak separation turned narrow, and suggested that the reversibility was improved greatly. Experimental parameters, such as scan rate, pH and accumulation conditions were optimized. It was found that a maximum current response can be obtained at pH = 5.0 after accumulation at -0.50 V for 80 s. The oxidation peak current was found to be linearly related to acetaminophen concentration over the range of $5.0{\times}10^{-7}\;\sim\;1.0{\times}10^{-4}$ mol $L^{-1}$ with a detection limit of $5.0{\times}10^{-8} $mol $L^{-1}$. A convenient and sensitive electrochemical method was developed for the determination of acetaminophen in a commercial paracetamol oral solution. Its practical application demonstrated that it has good selectivity and high sensitivity.

• Steel and Composite Structures
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• 제32권1호
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• pp.59-66
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• 2019

Hollow steel-reinforced concrete-filled GFRP tubular member is a new kind of composite members. Firstly set the mold in the GFRP tube (non-bearing component), then set the longitudinal reinforcements with stirrups (steel reinforcement cage) between the GFRP tube and the mold, and filled the concrete between them. Through the axial compression test of the hollow steel-reinforced concrete-filled GFRP tubular member, the working mechanism and failure modes of composite members were obtained. Based on the experiment, when the load reached the ranges of $55-70%P_u$ ($P_u-ultimate$ load), white cracks appeared on the surface of the GFRP tubes of specimens. At that time, the confinement effects of the GFRP tubes on core concrete were obvious. Keep loading, the ranges of white cracks were expanding, and the confinement effects increased proportionally. In addition, the damages of specimens, which were accompanied with great noise, were marked by fiber breaking and resin cracking on the surface of GFRP tubes, also accompanied with concrete crushing. The bearing capacity of the axially compressed components increased with the increase of reinforcement ratio, and decreased with the increase of hollow ratio. When the reinforcement ratio was increased from 0 to 4.30%, the bearing capacity was increased by about 23%. When the diameter of hollow part was decreased from 55mm to 0, the bearing capacity was increased by about 32%.

• Archives of Metallurgy and Materials
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• 제67권4호
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• pp.1547-1550
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• 2022

In this study, a flake-shaped metal powder was coated on a tube shaped pre-sintered 316L stainless steel support using a wet powder spraying process to fabricate a double pore structure, and the pore characteristics were analyzed according to coating time and tube rotation speed. The thickness of the coated layer was checked via optical microscopy, and porosity was measured using image analysis software. Air permeability was measured using a capillary flow porometer. As a result of the experiment, the optimal rotation speed of the support tube was established as 200 rpm. When the rotation speed was fixed, the coating thickness and the coating amount of the double pore structure increased as the coating time increased. The porosity of the double pore structure was increased due to the irregular arrangement of the flake-shaped powder. The air permeability of the double pore structure decreased with increasing fine pore layer thickness.