• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.904-912
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• 2005

The flow in a microchannel is usually characterized as a low Reynolds number (Re) so that good mixing is quite difficult to be achieved. In this regard, we developed a novel chaotic micromixer, named Barrier Embedded Kenics Micromixer (BEKM). In the BEKM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms: (i) splitting/reorientation by helical elements inside the microchannel and (ii) stretching/folding via periodically located barriers on the channel wall. The fully three-dimensional geometry of BEKM was realized by a micro-stereolithography technology, in this study, along with a Kenics micromixer and a circular T-pipe. Mixing performances of three micromixers were experimentally characterized in terms of an average mixing color intensity of phenolphthalein. Experimental results show that BEKM has better mixing performance than other two micromixers. Chaotic mixing mechanism, proposed in this study, could be integrated as a mixing component with Micro-Total-Analysis-System, Lab-on-a-chip and so on.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1549-1556
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• 2004

We have deigned, fabricated and compared four different types of static chaos microfluid mixers, including the mixers using straight channel flow, microblock-induced alternating whirl flow, microchannel-induced lamination flow, and combined alternating whirl-lamination flow. Among them, the alternating whirl-lamination (AWL-type) mixer, composed of 3-D rotationally arranged microblocks and dividing microchannels fabricated by conventional planar lithography process, is effective to reduce the mixing length over wide flow rate ranges. We characterize the performance of the fabricated mixers, through the flow visualization technique using phenolphthalein solution. We verify that the AWL-type microfluid mixer shows the shortest fluid mixing length of 2.8mm∼5.8mm for the flow rate range of Re=0.26∼26 with the pressure drop lower than 5kPa. Compared to the previous mixers, requiring the mixing lengths of 7∼17mm, the AWL-type microfluid mixer results in the 60% reduction of the mixing lengths. Due to the reduced mixing lengths within reasonable pressure drop ranges, the present micromixers have potentials for use in the miniaturized Micro-Total-Analysis-Systems($\mu$TAS).

• The Korean Journal of Physiology
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• v.11 no.2
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• pp.67-71
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• 1977

This study was undertaken to investigate the effect of cingulate cortical ablation upon gastric secretion and its components in rats. 23 male rats were divided into the cingulate(N=9) and the operated control(N= 14) groups. Cingulate cortex was ablated through a slit-shaped opening(1 mm in width, 5 mm in length) which was made symmetrically on both sides of, and parallel to, the sagittal suture by removing a bone flap from frontal bone on each side. In the operated control group, the surgical procedure was ended by the removal of the bone flap. Under light ether anesthesia, experimental animals were placed in a restraining jacket of fine mesh wire and gastric juice was collected for 5 hours via a canula which had been inserted through the anterior abdominal wall into the antral portion of the lumen of the stomach. Volume of the gastric juice was measured, and total acid output and free acid output were titrated with 0.04 N NaOH solution by using phenolphthalein and Topfer's reagent at indicator, and chloride ion output was estimated by means of chloridometer. Results obtained were that volume, total acid output, free acid output and chloride ion output of the gastric juice were higher significantly in the cingulate group than in the operated control group. It is inferred from the above results that the cingulate cortex exerts a fascilitatory influence upon gastric secretion and acid output in rats.

• Geomechanics and Engineering
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• v.18 no.1
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• pp.59-69
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• 2019

Grout injection is mainly used for permeability reduction and/or improvement of the ground by injecting grout material into pores, cracks, and joints in the ground. The oscillatory grout injection method was developed to enhance the grout penetration. In order to verify the level of enhancement of the grout, field grout injection tests, both static and oscillatory tests, were performed at three job sites. The enhancement in the permeability reduction and ground improvement effect was verified by performing a core boring, borehole image processing analysis, phenolphthalein test, scanning electron microscopy analysis, variable heat test, Lugeon test, standard penetration test, and an elastic wave test. The oscillatory grout injection increased the joint filling rate by 80% more and decreased the permeability coefficient by 33-68%, more compared to the static grout injection method. The constrained modulus of the jointed rock mass was increased by 50% more with oscillatory grout injection compared to the static grout injection, indicating that the oscillatory injection was more effective in enhancing the stiffness of the rock mass.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.149-150
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• 2022

In Korea, there is no clearly established technology for diagnosing and evaluating the damage depth of concrete structures created by fire. There have been cases of repairing, reinforcing, and demolishing degraded structures without diagnosing the damage depth. The commonly used phenolphthalein-based carbonate thickness measurement does not satisfy the complete disappearance condition of Ca(OH)₂ in the interval where the relatively stationary flow declines after exposure to high temperatures. Even a small amount of Portlandite[Ca(OH)₂] reacts with a red color, and the damage depth is misjudged. It was confirmed by X-ray diffraction and scanning electron microscope that Ca(OH)₂ existed from 300℃ to 500℃ where the residual compressive strength decreased.

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.11-17
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• 2012

This study focused on application of various $CO_2$ philic adsorbents with amine to improve $CO_2$ uptake in mortar. TGA, phenolphthalein method, FT-IR XRD, and FE-SEM analysis methods were used to evaluate $CO_2$ capture in mortar. When $CO_2$ philic adsorbents was used, $CO_2$absorption efficiency was improved maximum of 58.5%. Carbonation depth was increased 3 times compared with original mortar. Chemical reactions between bicarbonate ion, $CO_2$, $CO_2$ philic adsorbents aqueous solution, and $Ca^{2+}$ ions dissolved from cement formed $CaCO_3$ in the mortar. Therefore, impregnation of the $CO_2$ philic adsorbent on the surface of the mortar can increase the adsorbed $CO_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.254-259
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• 2012

The mechanical property enhancement was studied using fly ash produced from fluidized bed type boiler in power plant, which contains a lot of Ca component being used to carbonate for $CO_2$ fixation in the lightweight aggregates made of cement and some portion of fly ash as a cement substitution under the supercritical condition. Specimens having various fly ash substitution rates and curing periods were carbonated under the supercritical condition at $40^{\circ}C$. The weight change rate, carbonation rate by TG/DTA analysis, 1% Phenolphthalein test, specific gravity and mechanical compression strength test were performed to observe the mechanical property enhancement of the cemented materials after carbonation under the supercritical condition and to make sure those could be classified as lightweight aggregates having specific gravity under 2.0.

• Microbiology and Biotechnology Letters
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• v.20 no.2
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• pp.156-163
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• 1992

Bacillus sp. was isolated from soil for its strong activity of cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19). The enzyme was purified by gel filtration and anion exchange column chromatography using FPLC. The purified enzyme exhibited its maximum CGTase activity in the pH range of 6~8 and the temperature range of 50~$70^{\circ}C$. The molecular weight was estimated as 114,000 by SDS-PAGE. The isoelectric point of the enzyme was 4.3. The CGTase of Bacillus sp. E l produced $\beta$-cyclodextrin mainly and did not produce a-cyclodextrin. The product ratio of $\beta$-cyclodextrin to $\gamma$-cyclodextrin was 7:l.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1298-1306
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• 2005

In this paper, Part II, we realized the Serpentine Laminating Micromirer (SLM) which was proposed in the accompanying paper, Part I, by means of the injection molding process in mass production. In the SLM, the higher level of chaotic mixing can be achieved by combining two general chaotic mixing mechanisms of splitting/recombination and chaotic advection by the successive arrangement of 'F'-shape mixing units in two layers. Mold inserts for the injection molding process of the SLM were fabricated by SU-8 photolithography and nickel electroplating. The SLM was realized by injection molding of COC (cyclic olefin copolymer) with the fabricated mold inserts and thermal bonding of two injection molded COC substrates. To compare the mixing performance, a T-type micromixer was also fabricated. Mixing performances of micromixers were experimentally characterized in terms of an average mixing color intensity of a pH indicator, phenolphthalein. Experimental results show that the SLM has much better mixing performance than the I-type micromixer and chaotic mixing was successfully achieved from the SLM over the wide range of Reynolds number (Re). The chaotic micromixer, SLM proposed in this study, could be easily integrated in Micro-Total-Analysis- System , Lab-on-a-Chip and so on.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.1
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• pp.33-37
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• 2005

A micromixer plays an important role in Bio-MEMS or μ-TAS. Mixing is generally generated by turbulence and interdiffusion of two fluids. Because of low Reynolds number values (Re << 2000) within microchannels, it is difficult to generate turbulence, and consequently mixing mainly depends on interdiffusion. So, channel distance is often prohibitively long to mix two different fluids properly. To reduce this mixing length, we proposed a new mixer for micromixing in which two fluids were effectively mixed by an ultrasonic wave generated by PMN-PT. The ultrasonic wave was radiated into a chamber In the cross-sectional direction into the boundary surface formed by two fluids. The two fluids were positioned one on top of the other. The mixing state was measured by observing the color of samples due to the reaction of NaOH and phenolphthalein.