• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.2 s.245
• /
• pp.110-116
• /
• 2006

A syringe pump or a device using high electric voltage has been used for controlling flows inside a LOC (lab-on-a-chip). Compared to LOC, however, these microfluidic devices are large and heavy that they are burdensome for a portable ${\mu}-TAS$ (micro total analysis system). In this study, a new flow control technique employing pressure regulators and pressure chambers was developed. This technique utilizes compressed air to control the micro-scale flow inside a LOC, instead of a mechanical actuator or an electric power supply. The pressure regulator controls the output air pressure by adjusting the variable resistor attached. We checked the feasibility of this system by measuring the flow rate inside a capillary tube of $100{\mu}m$ diameter in the Re numbers ranged from 0.5 to 50. In addition, the performance of this flow control system was compared with that of a conventional syringe pump. The developed flow control system was found to show superior performance, compared with the syringe pump. It maintains automatically the: air pressure inside a pressure chamber whether the flow inside the capillary tube is on or off. Since the flow rate is nearly proportional to the resistance, we can control flow in multiple microchannels precisely. However, the syringe pump shows large variation of flow rate when the fluid flow is blocked in the microchannel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.5
• /
• pp.268-274
• /
• 2010

Because both R-134a and R-600a are used as a refrigerant of a household refrigerator in the global market, the home-appliance industry needs an optimized cycle for both refrigerants. The objective of this study is to provide the design guideline on the optimization of a refrigeration system using both refrigerants. For both refrigerants, the performance characteristics of the refrigeration system were tested by varying refrigerant charge amount, capillary tube length, suction diameter and SLHX length. The tested refrigeration system was optimized at the refrigerant charge of 60 g and the capillary tube length of 3600 mm with R-134a, and the refrigerant charge of 34 g and the capillary tube length of 3900 mm with R-600a. The COP increased from 1.63 to 1.68 for R-134a and increased from 1.37 to 1.48 for R-600a, respectively, by applying the suction diameter expansion. In addition, the COP of the R-134a and R-600a system decreased by 2.3~2.4% as the SLHX length decreased by 300 mm.

• Proceedings of the PSK Conference
• /
• 2000.10a
• /
• pp.248.2-248.2
• /
• 2000

• Proceedings of the Membrane Society of Korea Conference
• /
• 2001.10a
• /
• pp.39-50
• /
• 2001

The performance of membranes is governed their pore struture. Pore structures of porous materials can be determined by a number of techniques. However, The novel technique, capillary folw porometry has a number of advantages. In this technique, the sample is brought in contact with a liquid that fills the pores in the membrane spontaneously. Gas under pressure is used to force the liquid from the pores and increase gas flow. Gas flow rate measured as a function of gas pressure in wet and dry samples yield data on the largest pore size, the mean flow pore size, flow distribution and permeability. Pore characteristics of a number of membranes were measured using this technique. This technique did not require the use of any toxic material and the pressure employed was low. Capillary flow porometry is a suitable technique for measurement of the pore structure of many membranes.

• International Journal of Concrete Structures and Materials
• /
• v.4 no.1
• /
• pp.37-43
• /
• 2010

Theoretical models based on modern interpretations of the morphology and interactions of cement hydration products are developed for prediction of the mechanical properties of hydrated cement paste (hcp). The models are based on the emerging nanostructural vision of calcium silicate hydrate (C-S-H) morphology, and account for the intermolecular interactions between nano-scale calcium C-S-H particles. The models also incorporate the effects of capillary porosity and microcracking within hydrated cement paste. The intrinsic modulus of elasticity and tensile strength of hydrated cement paste are determined based on intermolecular interactions between C-S-H nano-particles. Modeling of fracture toughness indicates that frictional pull-out of the micro-scale calcium hydroxide (CH) platelets makes major contributions to the fracture energy of hcp. A tensile strength model was developed for hcp based on the linear elastic fracture mechanics theories. The predicted theoretical models are in reasonable agreements with empirical models developed based on the experimental performance of hcp.

• Laser Solutions
• /
• v.10 no.1
• /
• pp.11-17
• /
• 2007

We presented the proper laser processing conditions for the capillary line marking, which could be applied for the fabrication of injection needles. With changing the parameters such as lamp current, duty cycle and beam amplification factor of beam expander, we evaluated the processing performance considering amount of dross, processing efficiency and processed linewidth in the sample. We could carry out the proper line marking at the condition of 70% lamp current, duty cycle of 7-10% and 6-times amplification of beam diameter. To perform efficient line processing, the utilization of duty cycle of 12% at 80% lamp current was also preferred.

• Structural Engineering and Mechanics
• /
• v.51 no.3
• /
• pp.403-412
• /
• 2014

In this paper, enhancement of corrosion and chloride resistance of high performance self compacting concrete (SCC) through incorporating nanosilica into the binder has been investigated. For this purpose, different mixtures were designed with different amounts of silica fume and nano silica admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resitivity tests. Water absorption and capillary absorption were also measured as other durability-related properties. The results showed that water absorption, capillary absorption and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially blend of silica fume and nano silica. By addition of the admixtures, resistivity of the SCC mixtures increased which can lead to reduction of corrosion probability.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.5
• /
• pp.382-391
• /
• 2008

A simple analytical model of rarefied channel flow is developed to predict the compression ratio in a helical drag pump. If the surface velocity is zero, the model reduces to a capillary leaks. Predictions of our model agree well with the Knudsen's data for capillary leaks in transition flow, in addition to giving a good account of the Knudsen minimum. Also, the present results are compared with experimental data, and good agreement is obtained over the entire pressure range from molecular to slip flow.

• Korean Journal of Food Science and Technology
• /
• v.30 no.6
• /
• pp.1247-1251
• /
• 1998

A method is developed for simultaneously determining ethanol and acetic acid in vinegars by quantitative packed-column gas chromatography. Vinegars were filtrated and directly chromatographed on a $2\;m{\times}2\;mm$ stainless steel column packed with Tenax-GC, 80/100. Ethanol, isopropy alcohol as an internal standard, and acetic acid were completely separated within 20 min of running time without any interfering peaks. The accuracy of packed column gas solid chromatography (PCGSC) was discussed compared to the analytical data by titration, high performance liquid chromatography and capillary column gas liquid chromatography (CCGLC).

• KSBB Journal
• /
• v.27 no.4
• /
• pp.199-206
• /
• 2012

Chiral crown ethers are synthetic macrocyclic polyethers that bind protonated chiral primary amines with high selectivity and affinity. They have been widely used to separate or distinguish the enantiomers of chiral compounds containing a primary amino moiety by high-performance liquid chromatography, capillary electrophoresis, and NMR spectroscopy. In this paper, two important chiral crown ethers including chiral binaphthyl unit and (18-crown-6)-2,3,11,12-tetracarboxylic acid as chiral selectors are focused. And several chiral resolution techniques and their applications in chirotechnology using these chiral crown ethers with related chiral recognition mechanism studies are reviewed. Especially, it was shown that the commercially available HPLC columns based on (18-crown-6)-2,3,11,12-tetracarboxylic acid have been developed and successfully applied for the resolution of various primary amino compounds including amino acids.