• Membrane Journal
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• v.18 no.2
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• pp.176-184
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• 2008

Nano-porous ceramic membranes was synthesized by the sol-gel method. Gas permeation of hydrogen and nitrogen was determined by single composition gas. Pore size $0.1{\mu}m$ and porosity 32% of flat type ${\alpha}-Al_2O_3$ substrate was manufactured. An intermediate ${\gamma}-Al_2O_3$ layer with pore size of 4 nm was formed by dip-coating. Polymeric silica sol was synthesized by acid catalyzed hydrolysis and condensation of tetra-ethyl-ortho-silicate. Supported membranes on alumina were prepared by dipping and calcining. He, $N_2$ permeation experiments with nanoporous sol-gel modified supported ceramic membranes were peformed to determine the gas transport characteristics. $He/N_2$ permselectivity around $100{\sim}160$ and helium permeation in the order of $10^{-7}mol/m^2{\cdot}s{\cdot}Pa$ were measured in the temperature range of $303{\sim}363K$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.83-88
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• 2012

Real slug and bubbly flows were measured using a three-ring impedance meter that can efficiently measure the void fraction of two-phase flows in a tube. First, the fitting curves between the signal from the impedance meters and the void fraction were found. The impedance meter had different fitting curves for slug and bubbly flows that had the same void fraction. An impedance meter should choose one of the two fitting curves according to the flow pattern, and the flow patterns can be recognized using the measured void fraction. The velocities and sizes of the bubbles were calculated using the void fraction curves measured by two impedance meters.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.857-862
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• 2002

Porous ceramic supports with immobilized microorganisms for the water purifier were synthesized by firing green compacts of mixed powder comprising of fly ash, bentonite and an additive of yeast powder at 800∼1,000$^{\circ}C$ for 1h and the pore and mechanical properties of specimens were investigated. The compressive strength was increased in FB (Fly Ash + Bentonite) specimens while pore properties was decreased with increasing the bentonite content and sintering temperature. The compressive strength, bulk density, apparent density, porosity, mean pore size, pore volume and specific surface area of FB specimens at 800∼1,000$^{\circ}C$ were 89.6∼128.9 kgf/$cm^2$, 1.25∼1.43, 1.61∼1.78, 27.2∼62.2%, 7.9∼25.6 ${\mu}m$, 8.9∼$22.2{\times}10^{-5}\;cm^3/g$ and 35.2∼134.3 $m^2/g$, respectively. The pore properties of FBY (FB+yeast powder) specimens were superior to that of FB specimens, however compressive strength was decreased with increasing yeast powder content. The overall properties of 9F1B1Y (9F1B+10% of yeast powder) specimens at 900$^{\circ}C$ for 1 h were 98.7 kgf/$cm^2$, 1.20, 1.67, 68.1%, 48.9 ${\mu}m$, $29.5{\times}10^{-5}\;cm^3/g$ and 152.2 $m^2/g$, respectively. In this study, it was revealed that 9F1B1Y specimen demonstrated better S. saprophyticus adherence properties n their surface pores. Consequently, the microorganisms immobilized on porous ceramic supports showed better water purifying performance with many pores and adequate strength.

• Journal of Acupuncture Research
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• v.22 no.1
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• pp.177-190
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• 2005

Objective : This study intends to identify the effects of the Doin Gigong Exercise on the shoulder-arm pain in Women. Methods : The study was performed with nonequivalent control group pretest-posttest design. A total of 45 subjects were divided into 25 persons in experimental groups and 20 persons in contrastive group by convenience sampling. The data were collected by using questionnaires and measured values from June, 2004, to August, 2004. Results : The results of the study are as follows: 1. The homogeneity testing revealed that most study variables were equally distributed between experimental and control groups. 2. The first hypothesis: The experimental group who performed the Doin Gigong Exercise and who decreased on the subjective symptom scale was supported(t=10.245, p=.000). 3. The scond hypothesis : The experimental group who received Doin Gigong Exercise and who decreased on the subjective pain(VAS) was supported(t=6.816, p=.000). 4. The third hypothesis: The experimental group who received Doin Gigong Exercise and who decreased on the muscular stiffness measured techniques(UNIQUE) was supported (t=7.114, p.000). Conclusions : Based on the results described above, it is considered that the Doin Gigon Exercise is clearly effective in all an values of the 5 measured. Therefore, the Doin Gigong Exercise can be thought of as effective nursing intervention for the reduction of shoulder-arm pain in women.

• Composites Research
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• v.29 no.5
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• pp.256-261
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• 2016

In this work, we have prepared the filter papers with the pitch-based activated carbon fibers and the binder fibers using wet-laid process. The influence of the binder fiber on the porosity of the filter papers has been investigated by using nitrogen adsorption isotherms at 77 K and a scanning electron microscope (SEM). As a result, the specific surface area has increased with an decrease in the content of binder fiber. It has been shown that the optimum ratio of pitch-based activated carbon fibers and the binder fibers is 70:30, resulting in high porosity, excellent bonding strength, large specific surface area ($650.4m^2/g$) and high noxious gas removal efficiency (86.9%). In addition, it has been observed that the mean pore size distribution of the fiber papers has not been affected by the binder fiber.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.844-847
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• 2009

진공압출성형 공정을 이용하여 한쪽 끝단이 막힌 다공질 탄화규소 캔들 필터를 단일공정으로 제조하는 기술을 확립하였다. 캔들 필터 지지층의 특성 최적화를 위해 탄화규소 출발입자와 무기바인더의 첨가량 변화를 통해 기계적 특성과 기공크기 등의 분석을 수행하여 상용 캔들 필터의 수준에 대응할 수 있는 조합을 도출하였다. Mullite와 clay를 소결조제로 사용하고, $30{\mu}m$ 입도의 탄화규소 입자로 지지층을 제조한 경우, 30% 이상의 기공율을 보유하면서 50 MPa 이상의 상온 3점 굽힘강도를 나타낼 수 있는 조건이 확립됨에 따라 $125{\mu}m$ 입도의 탄화규소와 bi-modal로 사용할 경우, 상용제품의 특성을 상회하는 탄화규소 캔들 필터가 제조될 수 있음을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.251-259
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• 2005

In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.235-242
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• 2017

In order to prepare porous scaffolds capable of pore control, PMMA powder serving as a pore-forming agent was added to HA powder to synthesize a slurry containing TBA as a solvent. And then, porous HA scaffolds where pillarshaped pore channels interconnected with each other were fabricated by freeze-casting and sintering. The crystal structure of the HA scaffolds according to the addition amount of PMMA powder was measured by XRD and the surface and inner cross section of the scaffolds were analyzed through SEM. It was found that removal of PMMA during sintering affects the internal structure of the scaffolds and the crystallinity of the HA powder. Furthermore, through evaluating the physical and mechanical properties of the scaffolds, it was confirmed that the porosity, pore size and compressive strength can be controlled by controlling the addition amount of the pore-forming agent. It was also found that the HA scaffolds produced in this study were similar in structure and properties to the natural cancellous bone. This suggests that porous HA scaffolds with PMMA can be used as an alternative to autogenous bone for tissue engineering as an artificial bone scaffold.

• Korean Journal of Food Science and Technology
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• v.49 no.5
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• pp.507-512
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• 2017

The physicochemical properties of maize starch sonicated at various amplitudes (100, 200, and 300 W) and times (10, 30, and 50 min) were examined. The amount of enzyme-susceptible starch increased marginally after sonication. Sonication increased the amount of oil absorbed in the starch although the degree of oil absorption decreased with an extension of the sonication time, implied that different types and extent of damages occurred. Scanning electron microscopy revealed that ultrasound sonication did not form pores on the surfaces, but caused damages such as depression and erosion. Pasting viscosity of starch decreased with an increase in the severity of sonication conditions because of the weakened polymer network. X-ray diffraction suggested that the crystalline domains in starch were not susceptible to sonication and were more resistance to degradation. Sonicated starch formed more pin-holes on the surfaces in the initial glucoamylase reaction; subsequently, as the reaction proceeded, porous starch with enlarged pores was formed and finally, disrupted granular fragments were observed.

• Journal of the KSME
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• v.51 no.1
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• pp.53-56
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• 2011

로터스 금속은 종래의 등방성 기공구조의 다공질 금속에서 발현할 수 없는 새롭고 우수한 기계적 특성을 갖고 있어서 새로운 산업적 응용이 기대된다. 이 글에서는 로터스 금속의 제조법, 기계적 특성, 응용에 관해 소개하고자 한다.