• Geomechanics and Engineering
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• 제38권3호
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• pp.307-317
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• 2024

To get a better understanding of the effect of drying-wetting cycles (DWC) on the mechanical behaviors of silty clay hiving different initial moisture content (IMC), the direct shear tests were performed on sliding band soil taken from a reservoirinduced landslide at the Three Gorges Reservoir area. The results indicated that, as the increasing number of DWC, the shear stress-displacement curves type changed from strain-hardening to strain-softening, and both the soil peak strengths and strength parameters reduced first and then nearly remain unchanged after a certain number of DWC. The effects of DWC on the cohesion were predominated that on the internal friction angle. The IMC of 17% is regarding as the critical moisture content, and the evolution laws of both peak shear strength and strength parameters presented a reversed 'U' type with the rising of the IMC. Based on it, a strength deterioration evolution model incorporating the influence of IMC and DWC was developed to describe the total degradation degree and degradation rate of strength parameters, and the degradation of strength parameters caused by DWC could be counterbalanced to some extent as the soil IMC close to critical moisture content. The microscopic mechanism for the soil strength caused by the IMC and DWC were discussed separately. The research results are of great significance for further understanding the water-weakening mechanicals of the silty clay subjected to the water absorption/desorption.

• 자원리싸이클링
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• 제30권4호
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• pp.35-45
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• 2021

본 연구에서는 폐닥나무 섬유를 사용한 목모보드의 제조 및 조습 특성 분석을 수행하였다. 목모보드 제조를 위해 폐닥나무 섬유의 분쇄 시간을 30, 60, 120, 180초로 제어하였으며, 혼합량을 시멘트 대비 0, 3, 6, 9% 수준으로 외할 첨가하여 제어하였다. 분쇄시간 제어 조습섬유 혼입 목모보드의 흡·방습 특성 분석 결과, 60초 분쇄 섬유 혼합 목모보드가 흡·방습 성능이 뛰어난 것으로 확인되었으며, 이는 분쇄 섬유의 손상이 적어 소재 자체의 흡·방습 성능이 보드 혼합 시에도 발현되었기 때문이다. 또한 섬유 혼합량 제어 목모보드의 흡·방습 특성 분석 결과, 6% 혼합 목모보드가 흡·방습 특성이 가장 뛰어났으며, 흡습 및 방습량은 각각 291.00g/m² 및 108.75g/m²으로 확인되었다.

• Journal of the Korean Wood Science and Technology
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• 제40권1호
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• pp.10-18
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• 2012

최근 만들어지고 있는 거주공간은 단열성능 향상을 통한 냉난방 에너지 절약을 위하여 더욱 기밀해지고 있다. 이로 인해 일상생활 중에 발생하는 수분의 인위적인 배출과 외부공기의 인위적인 유입이 줄어듦에 따라 건축내장재의 자연조습기능에 대한 관심이 증대하고 있다. 본 연구에서는 열처리된 잣나무의 흡 방습성능을 평가하고 이에 영향을 미치는 인자들을 분석하였다. 상대습도 변화에 따른 평형함수율과 흡 방습률을 측정하였고, 조도(거칠기)와 미시적 표면형상, 그리고 FT-IR spectrum과 흡방습성과의 관계를 고찰하였다. 본 연구결과는 거주공간의 조습성능 정량화 평가시스템 구축을 위한 기초자료로 활용될 수 있을 것이라 기대된다.

• Food Science and Biotechnology
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• 제16권5호
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• pp.771-777
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• 2007

Sliced and whole root of rehmannia were dehydrated in a laboratory dryer at 40, 60, 80, and $100^{\circ}C$ to evaluate the kinetic parameters for dehydration of rehmannia. The drying curves of both samples were characterized by a falling-rate drying period only. Sliced rehmannia dried 1.1 to 3.1 times faster than whole root of rehmannia depending on drying temperature. Equilibrium moisture content (EMC) of rehmannia samples at the drying temperature tested were 0.069-0.078 g water/g dry solid, which was coincided with the monolayer moisture content (0.06 and 0.07 g water/g dry solid) evaluated from desorption isotherms using GAB (Guggenheim-Anderson-de Boer) model. A logarithmic model for thin layer drying was applied to evaluate the drying time to reach EMC ($t_{EMC}$) and drying constant (k). The effect of temperature on $1/t_{EMC}$ and k was described by the Arrhenius model with activation energy values of 32.56 and 47.14 kJ/mol determined using the former parameter, and 34.27 and 38.26 kJ/mol determined using the latter parameter for sliced and whole root of rehmannia, respectively.

• KSBB Journal
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• 제28권5호
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• pp.319-326
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• 2013

This study was carried out to investigate the in vitro and in vivo moisturizing properties and percutaneous absorption of PEG-impregnated Aloe vera gel. The PEG-i-Aloe gel was obtained from dewatering and impregnation by soaking (DIS) of Aloe vera leaf slice. The moisturizing property of the obtained sample was evaluated by moisture determination using gravimetric method in desiccator under different RH% and by water sorption-desorption test on human skin. The transdermal penetration characteristics of PEG-i-Aloe gel was investigated by Franz diffusion cell in vitro transdermal absorption method. PEG-i-Aloe gel had high moisture retention ability and could significantly lead the enhancing skin hydration status as well as reducing the skin water loss due to the film formation as a skin barrier. The skin penetration rate of PEGi- Aloe gel at steady state was 9.76 ${\mu}g/(h{\cdot}cm^2)$ and the quantity of the transdermal absorption was 144 ${\mu}g/cm^2$ in 9 hr. The penetration mechanism was well fitted with Higuchi model ($R^2$ = 0.974-0.994). The results show that PEG-i-Aloe gel has the significant moisturizing effect and strong penetration of the animal skin. It could be used as the moisturizing additive in cosmetic skin products.

• Journal of Biosystems Engineering
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• 제19권4호
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• pp.358-368
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• 1994

Major factors in reducing the stacking strength of corrugated fiberboard boxes in cold storage or transport conditions are high relative humidity, causing elevated moisture absorption by the boxes. The bottom boxes in a stack will deform to the critical deflection causing agricultural products damage there, and eventually additional deflection will cause box collapse and finally toppling of the stack. The study was conducted to determine the water absorption characteristics and the compressive strength of the corrugated fiberboard boxes being widely used in packaging agricultural products in Korea. The sample boxes for the study were selected from the regular slotted containers (RSC) types, and one was the box used in apple packaging (Box A), another one was the box used in pear packaging (Box B). The corrugated shipping containers were made from a large portion of recycled fibers in Korea, and comparing with Box B, Box A was fabricated from fiberboard which contained more percentage of old corrugated containers (OCC) imported from foreign countries than domestic waste paper. The results obtained from the study were summarized as follows ; 1. Equilibrium moisture content (EMC) of the sample boxes was established after about 20 hours, and the EMC by absorption was lower than that by desorption. The EMC increased with the increasing of relative humidity and with the decreasing of temperature, and the rate of increasing was much higher above the relative humidity of 50%. 2. The maximum compressive strength of Box A was about 100 kgf greater than that of Box B on the same enviromental conditions. The strength of the sample boxes decreased rapidly with the increasing of relative humidity. The effect of relative humidity on the strength was a little higher than that of temperature. 3. As the applied load was progressively increased and a level was reached, the vertical side panels ($L{\times}D$) deflected laterally inwards or outwards. The panels deflected laterally inwards at higher relative humidity. 4. The maximum compressive deflection ratio and the critical deflection ratio of the sample boxes were increased linearly with the increasing of relative hunidity, but trends for its ratios showed inconsistant response to temperature.

• Journal of the Korean Wood Science and Technology
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• 제37권2호
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• pp.141-147
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• 2009

The fluctuation of physical properties in wood or wood composites is an important subject when the materials in building and construction. Sorption and desorption occur in wood when exposed to the open air, and the temperature distribution in wood can fluctuate as a result of changes in environmental temperature, solar radiation, humidity, and wind velocity. In this study, the temperature difference and fluctuation caused by outdoor environment among different wood species were analyzed using a numerical method. The effect on the process of heat transfer in wood caused by environmental factors was investigated using 1-dimensional partial differential equation with real boundary and initial conditions. The experimental data have been used to check the accuracy of programming code. Through analysis, it was found out that density and moisture content have a negative effect on thermal diffusivity of wood.

• Fibers and Polymers
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• 제6권1호
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• pp.6-12
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• 2005

Fiber surface morphologies and associated internal structures are closely related to its properties. Unlike other fibers including cotton, bast fibers possess transverse nodes and fissures in cross-sectional and longitudinal directions. Their morphologies and associated internal structures were anatomically examined under the scanning electron microscope. The results showed that the morphologies of the nodes and the fissures of bast fibers varied depending on the construction of the inner fibril cellular layers. The transverse nodes and fissures were formed by the folding and spiralling of the cellular layers during plant growth. The dimensions of nodes and fissures were determined by the dislocations of the cellular layers. There were also many longitudinal fissures in bast fibers. Some deep longitudinal fissures even opened the fiber lumen for a short way along the fiber. In addition, the lumen channel of the bast fibers could be disturbed or disrupted by the nodes and the spi­rals of the internal cellular layers. The existence of the transverse nodes and fissures in the bast fibers could degrade the fiber mechanical properties, whereas the longitudinal fissures may contribute to the very rapid moisture absorption and desorption.

• Korean Chemical Engineering Research
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• 제60권3호
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• pp.377-385
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• 2022

우리나라 전통 숯가마로부터 제조된 숯의 표면형상과 흡착특성을 분석한 후, 습도와 온도를 조절하면서 이들의 수분 흡착성능을 측정하고 황토, 활성탄소섬유 직포 및 활성탄소섬유 종이의 수분 흡착성능과 비교하였다. 숯은 소수성이므로 45% 이하의 습도에서는 수분을 잘 흡착하지 않지만 습도가 증가하면 흡착성능이 서서히 1차식에 비례하여 증가하였다. 황토 분말도 낮은 습도에서는 숯과 유사했지만 습도가 증가하면 흡착성능이 기하급수적으로 증가하면서 Type V 등온흡착곡선을 보였다. 따라서 조선시대에 기상청 직원들이 숯과 황토의 수분 흡착능력을 일기예보에 적용하였다는 기록을 실험적으로 확인할 수 있었다. 활성탄소섬유 직포와 활성탄소섬유 종이는 수분 흡착능력이 월등하고 신속한 반응을 보이므로 습도측정 센서에 적용할 수 있다고 판단된다. 숯 조각의 등온흡착 및 탈착곡선 측정에서 흡착질인 질소의 탈착이 잘 이루어지지 않아 낮은 압력 이력현상(low-pressure hysteresis)이라는 독특한 Type I과 Type IV의 혼합형태를 보이는데, 이는 질소입자가 흡착시에 숯 세공의 틈새를 비비고 들어가 단단히 끼었다가 탈착시에 빠져나오지 않기 때문이다. 숯을 분말로 분쇄하면 이러한 틈새들이 분쇄되어 비표면적이 증가하고 낮은 상대압력에서 흡착질의 탈착량이 증가되었다.

• 한국해양바이오학회지
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• 제12권2호
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• pp.81-90
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• 2020

Sialic acid, which is contained in about 60-160 mg/kg in the edible bird's nest (EBN), is known to facilitate in the proper formation of synapses and improve memory function. The objective of this study is to extract effectively the sialic acid from edible bird's nest using affinity bead technology (ABT). After preparing the non-polar polymeric bead "KJM-278-28A" having a porous network structure, and then desorbed sialic acid was concentrated and dried. The analysis of the physicochemical properties of bead "KJM-278-28A" showed that the particle size was 400-700 ㎛, the moisture holding capacity was 67-70%, the surface area (BET) was 705-900 ㎡/g, and the average pore diameter 70-87 Å. The adsorption capacity of the bead "KJM-278-28A" for sialic acid was shown a strong physical force to bind sialic acid to the bead surface of 400 mg/L. In addition, as a result of analyzing the adsorption and desorption effects of sialic acid on water, ethanol, and 10% ethanol on the bead, it was confirmed that desorption effectively occurs from the beads when only ethanol is used. As a result of HPLC measurement of the separated sialic acid solution, a total of four sialic acid peaks of N-acetyl-neuraminic acid (Neu5Ac), α,β-anomer of Neu5Ac and N-glycoly-neuraminic acid were identified. Through these results, it was confirmed that it is possible to separate sialic acid from EBN extract with efficient and high yield when using ABT.