• Macromolecular Research
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• 제12권6호
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• pp.598-603
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• 2004

Cellulose nitrate (CN) composite membranes, containing cobalt porphyrin (CoP) complexes self-assembled within nanometer-sized rhenium clusters (ReCoP), have been prepared and their oxygen and nitrogen gas perme­abilities were analyzed. The solubility of ReCoP and the characteristics of the corresponding composite membranes were analyzed using a Cahn microbalance, FT-IR spectroscopy, wide-angle X-ray scattering, and differential scanning calorimetry. The nitrogen permeability through the CN composite membranes decreased upon addition of ReCoP and CoP, which implies that the presence of these oxygen carrier complexes affects the structure of the polymer matrix. The oxygen permeability through the composite membranes containing small quantities of ReCoP decreased, but it increased upon increasing the concentration. The oxygen gas transport was affected by the matrix at low ReCoP concentrations, but higher concentrations of ReCoP increased the oxygen permeability as a result of its reversible and specific interactions with oxygen, effectively realizing ReCoP carrier-mediated oxygen transport.

• 한국지반신소재학회논문집
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• 제4권2호
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• pp.3-9
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• 2005

최근 모래가격이 급등하고 수급이 어려워져 비교적 가격이 저렴한 코코넛껍질 압축매트와 황마필터로 구성된 수평 천연섬유배수재가 모래 대체재료로서 각광 받고 있다. 본 연구에서는 수평 천연섬유배수재의 인장강도와 투수특성을 평가하여 수평 배수재로서의 사용성을 평가하였다. 수평 천연섬유배수재의 인장특성을 분석한 결과 코코넛껍질 매트의 매우 낮은 인장강도에도 불구하고 대부분의 인장강도가 황마필터에서 발휘되므로 Christopher와 Holtz(1985)가 제안한 일반적인 토목섬유에 대한 인장강도 기준을 훨씬 상회하는 것으로 나타났다. 또한, 매우 높은 압축하중에서 수평 천연섬유배수재의 투수성을 평가한 결과 일반적인 모래의 투수계수보다 높은 투수성을 나타내는 것으로 평가되었다. 이와 같은 결과를 종합적으로 분석하면, 수평 천연섬유배수재는 기존의 모래재료를 대체할 수 있는 배수재료로 사용이 가능할 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.382-388
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• 2005

Soil vapor extraction(SVE) is an effective and cost efficient method of removing volatile organic compounds(VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Prefabricated vertical drains(PVDs) have been used for dewatering fine-grained soils for more than 25 years. Incorporating PVDs in and SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the work described herein was to effectively incorporate PVDs into a SVE remediation system and to demonstrate a PVDs enhanced SVE system at full scale. The finding from this research will facilitate the design of field PVD-SVE systems in terms by providing insight into the optimal spacing between PVDs, the radius of influence of the wells and the flow rates to be used to capture and extract gas phase contaminants.

• 한국분말재료학회지
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• 제22권2호
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• pp.87-92
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• 2015

Metallic porous materials have many interesting combinations of physical and geometrical properties with very low specific weight or high gas permeability. In this study, highly porous Cu foam is successfully fabricated by a slurry coating process. The Cu foam is fabricated specifically by changing the coating amount and the type of polyurethane foam used as a template. The processing parameters and pore characteristics are observed to identify the key parameters of the slurry coating process and the optimized morphological properties of the Cu foam. The pore characteristics of Cu foam are investigated by scanning electron micrographs and micro-CT analyzer, and air permeability of the Cu foam is measured by capillary flow porometer. We confirmed that the characteristics of Cu foam can be easily controlled in the slurry coating process by changing the microstructure, porosity, pore size, strut thickness, and the cell size. It can be considered that the fabricated Cu foams show tremendous promise for industrial application.

• Computers and Concrete
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• 제17권5호
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• pp.613-628
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• 2016

In this study, the influence of coarse aggregate size and type on chloride penetration of concrete was investigated, and the grey correlation analysis was applied to find the key influencing factor. Furthermore, the proposed 6-10-1 artificial neural network (ANN) model was constructed, and performed under the MATLAB program. Training, testing and validation of the model stages were performed using 81 experiment data sets. The results show that the aggregate type has less effect on the concrete permeability, compared with the size effect. For concrete with a lower w/b, the coarse aggregate with a larger particle size should be chose, however, for concrete with a higher w/c, the aggregate with a grading of 5-20 mm is preferred, too large or too small aggregates are adverse to concrete chloride diffusivity. A new idea for the optimum selection of aggregate to prepare concrete with a low penetration is provided. Moreover, the ANN model predicted values are compared with actual test results, and the average relative error of prediction is found to be 5.62%. ANN procedure provides guidelines to select appropriate coarse aggregate for required chloride penetration of concrete and will reduce number of trial and error, save cost and time.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.339-343
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• 2006

We observed the application possibility of inductive coupler for the underground high-voltage power line communication by means of analysis of signal transmission characteristics and magnetic properties on annealing temperatures for high-permeability Fe-base amorphous alloys. The best electromagnetic and transmission characteristics were shown in nano-crystalline precipitated alloy annealed at temperature $510^{\circ}C$. The transmission characteristics in the low-frequency band depend on permeability of magnetic core materials and its properties of high-frequency band can be improved by impedance matching. Using the high pass filter embedded in the coupler, other noise signal band except for communication signals could be cut off.

• Elastomers and Composites
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• 제46권4호
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• pp.329-334
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• 2011

일반적으로 butyl 고무(IIR : isobutylene isoprene rubber)는 우수한 내기체투과성 및 저반발 탄성체로서 우수한 충격흡수성을 갖는다. 본 실험에서는 butyl고무에 EPDM(ethylene propylene diene monomer)을 기계적 혼련법으로 blend 혼련물을 제조하여 이들의 가교 거동, 물리적 성질 및 내오존성 등을 측정하였다. EPDM 고무량이 증가할수록 최적 가황시간이 단축되는 경향을 보였다. 기체투과속도 테스트에 의한 내기체투과성 측정 결과 butyl고무량이 50 wt% 이상일 경우에는 기체투과도가 현저히 감소하였다. 한편 butyl rubber/EPDM 블렌드의 경우에 EPDM의 함량이 25 wt.% 이상 함유될 경우 내오존성이 향상되어 50 pphm, $50^{\circ}C$, 120시간 조건에서도 아무런 표면변화가 없었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1412-1419
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• 2005

Preventing the infiltration of rainwater into the landfill site is the main purpose of the final cover in landfill sites. Compacted clay layer or geomembrain have been used as a conventional landfill final cover. But they have several disadvantages when damages might occur due to puncturing, differential settlement and desiccation or freeze and thaw. For this reason, as an alternative method SRSL(Self Recovering Sustainable Liner) has been developed. Adopting the precipitation reaction of two chemical material, by forming precipitates that fill the pores, and lower the overall permeability of the liner. The advantage of this method is that when fracture of the liner occurs the remaining reactants of the two layers form precipitates that fill the fracture and recover the low permeability of the liner. In this study, the recovering ability of the SRSL with a crack due to the seasonal variation or differential settlements was investigated by permeability tests. And in order to estimate the durability of the SRSL after freeze/thaw and desiccation, uniaxial compression strength tests were performed.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.71-81
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• 2008

A macroscopic finite element model is applied to investigate the effect of fire induced spalling on the response of reinforced concrete (RC) beams. Spalling is accounted for in the model through pore pressure calculations in concrete. The principles of mechanics and thermodynamics are applied to compute the temperature induced pore pressure in the concrete structures as a function of fire exposure time. The computed pore pressure is checked against the temperature dependent tensile strength of concrete to determine the extent of spalling. Using the model, case studies are conducted to investigate the influence of concrete permeability, fire scenario and axial restraint on the fire induced spalling and also on the response of RC beams. Results from the analysis indicate that the fire induced spalling, fire scenario, and axial restraint have significant influence on the fire response of RC beams. It is also shown that concrete permeability has substantial effect on the fire induced spalling and thus on the fire response of concrete beams. The fire resistance of high strength concrete beams can be lower that that of normal strength concrete beams due to fire induced spalling resulting from low permeability in high strength concrete.

• 한국전자파학회논문지
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• 제21권9호
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• pp.1030-1036
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• 2010

본 논문은 다이폴 타입 안테나의 광대역화를 위한 원통형 자성 매질 구조를 가지는 급전 프로브의 시뮬레이션 설계를 제안한다. 저주파수 대역의 확보를 위해 고투자율의 자성체를 설계 계산에서 고려하였다. 광대역 특성은 투자율에 의존하지 않고, 자성체와 급전 프로브 사이의 거리($r_m$)와 자성체의 두께($t_m$)의 조정에 의해 구할 수 있다는 것이 확인되었다. 뿐만 아니라, 원통형 자성 매질의 구조를 가지지 않는 설계 안테나의 크기와 비교하여 약 18 % 정도 소형화시킬 수 있었다.