• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.388-395
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• 2018

Significant efforts have been applied toward fabricating three-dimensional (3D) scaffolds using 3D-bioprinting tissue engineering techniques. Gelatin has been used in 3D-bioprinting to produce designed 3D scaffolds; however, gelatin has a poor printability and is not useful for fabricating desired 3D scaffolds using 3D-bioprinting. In this study, we fabricated pore size controlled 3D gelatin scaffolds with two step 3D-bioprinting approach: a low-temperature ($-10^{\circ}C$) freezing step and a crosslinking process. The scaffold was crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The pore sizes of the produced 3D gelatin scaffolds were approximately 30% smaller than the sizes of the designed pore sizes. The surface morphologies and pore sizes of the 3D gelatin scaffolds were confirmed and measured using scanning electron microscopy (SEM). Human dermal fibroblasts (HDFs) were cultured on a 3D gelatin scaffold to evaluate the effect of the 3D gelatin scaffold pore size on the cell proliferation. After 14 days of culture, HDFs proliferation throughout the 3D gelatin scaffolds prepared with more than $580{\mu}m$ pore size was approximately 14% higher than proliferation throughout the 3D gelatin scaffold prepared with a $435{\mu}m$ pore size. These results suggested that control over the 3D gelatin scaffold pore size is important for tissue engineering scaffolds.

• Carbon letters
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• 제11권3호
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• pp.201-205
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• 2010

Activated carbons are well known as adsorbents for gases and vapors. Micro porous carbons are used for the sorption/separation of light gases, whereas, carbon with bigger pore size are applied for removal of large molecules. Therefore, the control of pore size of activated carbon plays a vital role for their use in specific applications. In the present work, steam activation parameters have been varied to control pore size of the resulting activated carbon. It was found that flow rate of steam has profound effect on both surface characteristic and surface morphology. The flow rate of steam was optimized to retain monolith structure as well as higher surface area.

• 한국분말재료학회지
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• 제26권6호
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• pp.502-507
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• 2019

Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100-450 ㎛ are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80℃ and 200℃ in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800℃ for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.434-441
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• 2018

The pore size of nickel (Ni) bottom electrode layer (BEL) for low-temperature solid oxide fuel cells embedded with ultrathin-film electrolyte was controlled by changing the substrate surface morphology and deposition process parameters. For ~150-nm-thick Ni BEL, the upper side of an anodic aluminum oxide (AAO) substrate with ~65-nm-sized pores provided ~1.7 times smaller pore size than the lower side of the AAO substrate. For ~100-nm-thick Ni BEL, the AAO substrate with ~45-nm-sized pores provided ~2.6 times smaller pore size than the AAO substrate with ~95-nm-sized pores, and the deposition pressure of ~4 mTorr provided ~1.3 times smaller pore size than that of ~48 mTorr. On the AAO substrate with ~65-nm-sized pores, the Ni BEL deposited for 400 seconds had ~2 times smaller pore size than the Ni BEL deposited for 100 seconds.

• 전자공학회논문지
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• 제52권4호
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• pp.135-144
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• 2015

지문의 땀샘(pore)은 지문인식 분야에서 아주 유용한 특징의 하나이고 땀샘에 기반한 지문인식 시스템도 많이 제안되었다. 땀샘 정보를 이용하여 지문을 인식하려면 땀샘을 정확하게 추출하는 것이 아주 중요하다. 기존의 땀샘 추출 방법은 2차원 모델정합 기법을 이용하여 땀샘 중심을 검출한다. 본 논문에서는 2차원 모델보다 간단한 1차원 가우시안 모델을 이용한 땀샘 추출 방법을 제안한다. 1차원 모델을 이용하여 모델정합하는 과정에 2차원 모델보다 적은 연산량을 필요한다는 장점이 있다. 제안하는 방법은 먼저 국부적 융선(ridge)의 방향을 계산하고 융선 마스크(ridge mask)를 생성한 다음 땀샘 중심이 주변보다 밝다는 성질을 이용하여 사이즈가 각각 $3{\times}3$과 $5{\times}5$인 필터로 땀샘 후보를 찾는다. 검출된 땀샘 후보에 대하여 1차원 가우시간 모델정합을 적용하여 땀샘 중심을 검출한다. 땀샘 추출 실험을 통하여 제안하는 방법은 기존의 2차원 모델에 기반한 방법보다 더 높은 땀샘 검출률을 보여주었고 땀샘 매칭 실험을 통하여 제안하는 땀샘 추출 방법이 지문인식에 사용될 수 있음을 보여준다.

• 대한화장품학회지
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• 제30권2호
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• pp.189-195
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• 2004

카본 블랙은 매우 낮은 밀도로 화장품에는 사용되지 않고 있지만 독성이 없고 안정한 물리적 특성과 검은색의 특성으로 이용 가치가 있다고 사료되는 바이다. 본 연구에서는 TEOS, a) PEO/ lecithin, b) PEO/polyethylene glycol, c) lecithin/polyethylene을 ethanol/water 수용액상에서 계면활성제를 탄화시켜 sol-gei반응에 의해 meso-porous silica샘플을 얻었고 N2 조건하 50$0^{\circ}C$에서 열처리된 organic-inorganic hybrid silica를 합성하였다. Pore안에 카본 블랙을 함유하는 meso-porous silica는 친수성, 소수성 용매에서 모두 좋은 분산성을 보여준다. 이 샘플은 BET에 의해 specific surface area (750$m^2$/g)과 pore size (4-6 nm)이고, XRD측정으로 pore structure (cylindrical type)를, 샘플의 SEM촬영으로 morphology(0.1-0.5$\mu\textrm{m}$ 입자 크기를 갖는 spherical powder)를 갖는다는 것을 알아냈다. 이렇게 합성한 카본-실리카 블랙 컬러를 마스카라에 적용하면 일반적으로 마스카라에 사용되던 블랙 컬러 사용시 보다 좀더 검은색을 보여주는 것은 물론이고 우수한 분산성도 갖는다. 무엇보다 이 파우더의 밀도 조절이 가능하여 마스카라 뿐 만 아니라 모든 화장품에의 사용이 가능하다.

• 멤브레인
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• 제22권2호
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• pp.104-112
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• 2012

Chemically stable Polyvinylidene fluoride-hexa-fluoropropane (PVDF-HFP) copolymer asymmetric membranes were prepared by the conventional phase inversion process, using Dimethyacetamide (DMAc) as a solvent and water as a non-solvent. To control the pore size and porosity of the PVDF-HFP membranes, tetra-ethoxysilane (TEOS) was used as a pore-forming agent. The prepared membranes were characterized, using several analytical methods such as Fourier Transform Infrared spectroscopy (FTIR), Thermo-gravimetric analyzer (TGA), Field Emission Scanning Electronic Microscopy (FESEM). TEOS turned out to increase porosity and make homogeneous pores on the membranes. Depending on the composition of the dope solutions, the pore size was ranged from 0.1 to 1.0 ${\mu}m$. The flux of the PVDF-HFP membranes prepared by using TEOS as a pore forming agent was increased substantially without much decrease in the rejection. When 15 wt% PVDF-HFP solution was blended with 13 wt% TEOS solution at composition ratio of 70/30 in wt%, the water flux at 2 bars was about 2 $m^3/m^2day$.

• 한국재료학회지
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• 제14권9호
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• pp.664-669
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• 2004

Anodic aluminum oxide (AAO) with pores of various diameter, density, and thickness values was obtained through control of the anodization parameters including voltage, temperature, pore widening time, anodization time, etc. The pore diameter was controlled by a pore widening in an etchant, and alumina templates having stepped nano-channels were fabricated by repetition of anodization and pore widening processes. Stepped carbon nanotubes (CNTs) were then grown on the stepped AAO templates by pyrolysis of acetylene without using the catalyst. High-resolution transmission electron microscopy images revealed that CNTs have a multi-wall structure made of graphite flakes of several nm sizes. The current-voltage characteristic of the sloped and linear CNTs were also examined.

• The Korean Journal of Physiology and Pharmacology
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• 제6권2호
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• pp.81-85
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• 2002

Conventional views of synaptic transmission generally overlook the possibility of 'postfusional-control' the regulation of the speed or completeness of transmitter release upon vesicular fusion. However, such regulation often occurs in non-neuronal cells where the dynamics of fusion-pore opening is critical for the speed of transmitter release. In case of synapses, the slower the transmitter release, the smaller the size and rate-of-rise of postsynaptic responses would be expected if postsynaptic neurotransmitter receptors were not saturated. This prediction was tested at hippocampal synapses where postsynaptic AMPA-type glutamate receptors (AMPAR) were not generally saturated. Here, we found that the small miniature excitatory postsynaptic currents (mEPSCs) showed significantly slower rise times than the large mEPSCs when the sucrose-induced mEPSCs recorded in cyclothiazide (CTZ), a blocker for AMPAR desensitization, were sorted by size. The slow rise time of the small mEPSCs might result from slow release through a non-expanding fusion pore, consistent with postfusional control of neurotransmitter release at central synapses.

• Elastomers and Composites
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• 제42권2호
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• pp.86-92
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• 2007

이축 연신에 의한 폴리테트라플루오르에틸렌(PTFE) 막을 제조하기 위한 공정 조건을 확립하기 위하여 상용화되는 PTFE 막 및 PTFE 미세 분말을 선택하였다. 막 제조공정에 사용 되기 위해 PTFE 미세 분말은 전처리 되었고, 첨가제와 혼합되었으며, 혼합물의 숙성, 페이스트 압출 공정, 칼렌더 가공 공정 등이 수행되었고 막의 두께 및 기공크기와 다공성을 측정하였다. 기계적 물성을 강화하기 위하여 시료의 후처리가 실시되었고, PTFE 막 제조공정을 위한 페이스트 압출 공정에서의 PTFE 분말과 첨가제의 혼합비, 숙성 시간, 숙성 온도, 압력 등에 관한 공정 조건이 확립되었고, 기공크기(pore size)와 다공성(porosity)을 조절할 수 있는 이축연신 공정에 대한 최적공정 조건도 확립하였다.