• 한국기계가공학회지
• /
• 제19권10호
• /
• pp.1-7
• /
• 2020

In this study, a multichannel gas-liquid microextraction system is designed by integrating the automatic elution of extraction line and multichannel gas-purging liquid phase microextraction. The system uses an injection pump and inert gas to push the extraction solvent to a sample bottle of a gas-phase color autosampler and then implements multichannel gas-liquid microextraction and gas chromatography-mass spectrometry. The system also employs a three-way integrated micro-high-temperature heater, syringe pump, and microflow controller to realize the simultaneous processing of multiple groups of samples, thus improving the sample pretreatment speed and reproducibility and reducing human error. Autoinjection experiments were implemented with polycyclic aromatic hydrocarbon standard samples. The experiments show that the average recovery rate of the system exceeds 70%, and the relative standard among the channels is less than 15%.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.1882-1887
• /
• 2007

In the present experimental study, the effect of interfacial tensions on pressure drop of air-water two-phase flow in round mini-channels was investigated. A glass (highly wettable) tube and a Teflon (poorly wettable) tube, both in 350 mm length but 1.8 mm and 1.59 mm in inner diameters each, were used for the tests. All the experiments were performed only in the plug flow regime, confirmed by visualization. In the glass tube, the gas plugs were surrounded by the liquid film along the inner periphery. On the other hand, the inner wall remained dry at the gas portion in the Teflon tube. The pressure drop of the plug flow in the Teflon tube without the liquid film) appeared much larger than in the glass tube (with the liquid film) due to dissipation of energy by movement of the wetting lines. In this paper, various correlations on the two-phase pressure drop of plug flows were compared and a modified correlation was proposed, taking account of the surface wettability.

• 설비공학논문집
• /
• 제13권4호
• /
• pp.304-311
• /
• 2001

An experimental study on the countercurrent two-phase flow in narrow rectangular channels has been performed. The void fraction and the pressure gradient were investigated using air and water in 760 mm long, 100 mm wide. vertical test sections with 2, 3 and 5 mm channel gaps. Tests were systematically performed with downward liquid superficial velocities and upward gas velocities covering 0 to 0.08 and 0 to 2.5 m/s ranges. respectively. the experimental results were compared with the previous correlations, which were mainly for round tubes, and the qualitative trends were found to be in good agreements. However the quantitative discrepancies were hardly neglected. as the superficial gas velocities increased, the void fraction increased and the pressure gradient decreased, where the effects of the liquid superficial velocities were infinitesimal. as the gap width of the rectangular channel increased the void fraction and the 2-phase frictional pressure gradient approached those values for the round tubes. Equi-periphery diameter, rather than the hydraulic diameter, seemed to be more effective in the analysis of two-phase flow behavior.

• 대한기계학회논문집B
• /
• 제27권5호
• /
• pp.635-643
• /
• 2003

Parametric study for the analysis of performance characteristics of a planar -type solid oxide fuel cell(SOFC) using computational flow analysis is conducted. A planar -type SOFC, which is composed by two gas channels (fuel and ai.) and one set of anode-electrolyte-cathode assembly, is modeled as a two -dimensional isothermal case. Results of computational analysis of flow field including distributions of mass fractions in gas channels are used to the performance analysis of the fuel cell. Flow analysis makes it possible to consider current density distributions along the length of the cell in the process of performance analysis of the SOFC. As results of parametric study, it is found that the mole fraction of fuel at the inlet of fuel channel, operating pressure and temperature are closely related to the performance characteristics of SOFC.

• 한국수소및신에너지학회논문집
• /
• 제25권4호
• /
• pp.386-392
• /
• 2014

The effective water management in a polymer electrolyte membrane fuel cell (PEMFC) is one of the key strategies for improving cell performance and durability. In this work, an ex situ measurement was carried out to understand the water droplet behavior on the surface of gas diffusion layer (GDL) as a fundamental study for establishing novel water management. For that purpose, simplified cell including one rib and two flow channels was designed and fabricated. Using this ex situ device, the water droplet emergence through the GDL of the PEMFC was emulated to understand liquid water transport through the porous diffusion medium. Through the visualization experiment, the emergence and growth of water droplets at the channel/GDL interface are mainly observed with the surface characteristics of GDL (SGL 10BA, 24BA) and rib when the liquid water passes through the GDL and is expelled to the flow channel. It is expected that the results obtained from this study can contribute to the better understanding on the water droplet behavior (emergence and removal) in the flow channels of PEMFC.

• 천문학회보
• /
• 제43권2호
• /
• pp.33.1-33.1
• /
• 2018

Ram pressure stripping by intracluster medium (ICM) can play a crucial role in galaxy evolution in the high-density environment as seen by many examples of cluster galaxies. Although much progress has been made by direct numerical simulations of galaxies (or a galaxy) as a whole in a cluster environment, the interstellar medium (ISM) in galactic disks is not well resolved to understand responses of the ISM in details. In order to overcome this, we utilize the TIGRESS simulation suite that focuses on a local region of galactic disks and resolves key physical processes in the ISM with uniformly high resolution. In this talk, we present the results from the solar neighborhood TIGRESS model facing the ICM winds with a range of ram pressures. When ram pressure is weaker than and comparable to the ISM weight, the ICM winds simply reshape the ISM to the one-sided disk, but star formation rates remain unchanged. Although there exist low-density channels in the multiphase ISM that allow the ICM winds to penetrate through, the ISM turbulence quickly closes the channels and prevents efficient stripping. When ram pressure is stronger than the ISM weight, a significant amount of the ISM can be stripped away rapidly, and star formation is quickly quenched. While the low-density gas is stripped rapidly, star formation still occurs in the extraplanar dense ISM (1-2kpc away from the stellar disk). Finally, we quantify the momentum transfer from the ICM to the ISM using the mass-and momentum-weighted velocity distribution functions of each gas phase.

• The Korean Journal of Physiology and Pharmacology
• /
• 제7권6호
• /
• pp.357-362
• /
• 2003

Carbon monoxide (CO) is low molecular weight oxide gas that is endogenously produced under physiological conditions and interacts with another gas, nitric oxide (NO), to act as a gastrointestinal messenger. The aim of this study was to determine the effects of exogenous CO on L-type calcium channel currents of human jejunal circular smooth muscle cells. Cells were voltage clamped with 10 mM barium ($Ba^{2+}$) as the charge carrier, and CO was directly applied into the bath to avoid perfusion induced effects on the recorded currents. 0.2% CO was increased barium current ($I_{Ba}$) by $15{\pm}2$% ($mean{\pm}S.E.$, p<0.01, n=11) in the cells. To determine if the effects of CO on barium current were mediated through the cGMP pathway, cells were pretreated with 1-H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, $10{mu}M$), a soluble guanylyl cyclase inhibitor, and exogenous CO (0.2%) had no effect on barium currents in the presence of ODQ ($2{\pm}1$% increase, n=6, p>0.05). CO mediates inhibitory neurotransmission through the nitric oxide pathway. Therefore, to determine if the effects of CO on L-calcium channels were also mediated through NO, cells were incubated with $N^G-nitro-L-arginine$ (L-NNA, 1 mM), a nitric oxide synthase inhibitor. After L-NNA pretreatment, 0.2 % CO did not increase barium current ($4{\pm}2$% increase, n=6, p>0.05). NO donor, SNAP ($20{\mu}M$) increased barium current by $13{\pm}2$% (n=6, p<0.05) in human jejunal smooth muscle cells. These data suggest that CO activates L-type calcium channels through NO/cGMP dependant mechanism.

• 한국산업융합학회 논문집
• /
• 제11권2호
• /
• pp.65-70
• /
• 2008

This study presents gas turbine cooling blade by using experimental and numerical works. The review cover researches related to cooling channels using finite element method in rotating blade. Also, the film cooling device and the heat transfer of the external surface of the blade are included. In addition, several methods to be used for the design of the blade, numerical method and experimental techniques are introduced. This work will contribute to improving the manufacturing of engine and the efficiency of gas turbine engines.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.2101-2104
• /
• 2003

Experimental investigations are performed for the rarefied gas flows in a disk-type drag pump (DTDP). The pump considered in this paper consists of grooved spiral channel on rotors and planar stators. The flow-metre method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of $0.001{\sim}4$ Torr. The maximum of compression ratio was about 3300 for three-stage DTDP, 1000 for two-stage and 100 for single-stage DTDP at zero throughput. The number of stage influences the pumping speed of DPDT

• 반도체디스플레이기술학회지
• /
• 제5권1호
• /
• pp.27-31
• /
• 2006

Non-contact transportation system using air cushion for the manufacturing of large-sized LCD panels was considered. Flow characteristics between air pad and glass plate was analyzed using computational fluid dynamics method to obtain optimized air pad configurations. Effects of the design variables such as hole arrays from which gas is injected, gas-feeding method into the gas supplying channels, and horizontal and vertical pitches of clusters of holes were studied. Optimized air pad unit gave evenly distributed pressure contour on the glass surface and well-suspended levitation height in the experiment.