• 터널과지하공간
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• 제13권3호
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• pp.215-224
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• 2003

자연 상태에서의 물리적 풍화를 실험적으로 재현하기 위해서 동결-응해 시험을 실시하였다. 시험 과정에서 탄성파 속도, 흡수율, 무게 및 부피 변화 등의 물리적 성질을 측정하였으며, 시험 전 및 시험 종료 후에 일축압축시험을 실시하여 강도 및 탄성 계수의 변화도 조사하였다. 시료의 무게 및 부피 변화는 풍화의 진전 정도와 명확한 상관관계를 보이지 않았으나 탄성파 속도와 일축압축강도 및 탄성계수는 풍화가 진행되면서 감소함을 보였다. 시험 결과는 암반 사면의 장기적 안정성 평가에 이용될 수 있을 것으로 기대된다.

• Food Science and Biotechnology
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• 제16권5호
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• pp.817-821
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• 2007

The effect of acetylated rice (AR) starch at different concentrations (0, 4, 6, and 8%) on rheological properties of surimi sols and gels was studied. Dynamic frequency sweeps of surimi-AR starch sols at $10^{\circ}C$ showed that the magnitudes of storage moduli (G') decreased with an increase in starch concentration while those of tan ${\delta}$ increased, indicating that the effect of AR starch on the viscoelastic properties of surimi sols depended on starch concentration. In general, the G' thermograms of surimi sols showed the similar sol-gel transition pattern and they were also influenced by the addition of AR starch. The presence of AR starch in the surimi gel system reduced the gel strength and expressible moisture content (EMC). Surimi-AR starch gels showed better freeze-thaw stability compared to the control (0% starch concentration). The effect of AR starch on the rheological properties of surimi sols and gels appeared to be related to the swelling ability of starch granules in the presence of limited water available for starch.

• 한국세라믹학회지
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• 제55권1호
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• pp.36-43
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• 2018

The physical and chemical analyses of mineral waste such as moisture content, water absorption, freezing-thawing resisting sexual, chemical composition and crystal structure were investigated. In the technological process of crushing, screening, molding, drying, preheating, sintering and cooling, many parameters were changed to eliminate the influence of freeze thaw stability and the ball billets were processed into slate ceramsites eventually. Adopting orthogonal experiment and range analysis, the optimal technology parameters were confirmed as preheating temperature of $300^{\circ}C$ for 25 minutes and sintering temperature of $1230^{\circ}C$ for 20 minutes. Slate wastes in Shangri-la could foam and expand without any additive. The ultra-light ceramsite could be directly used as building aggregate, since the analysis results of its leaching toxicity were eligible. Besides, effects of sintering temperature on physical property and crystal phase were also explored in this study.

• 광물과 암석
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• 제35권3호
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• pp.299-311
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• 2022

지표에 노출된 암석은 지속적으로 풍화를 받게 되고 이러한 영향으로 암석의 공학적 안정성이 약해지게 된다. 특히 풍화가 진행되면서 암석의 표면은 풍화에 의해서 변화를 일으키고 이러한 표면 변화는 암석으로 구성된 지반의 공학적 안전성에 영향을 미치게 된다. 또한, 풍화를 받은 암석에서 생성되는 화학종은 주변환경에 직접적인 영향을 미치거나 구조물에 영향을 미치게 된다. 광산지역과 같이 암석이 노출된 지역에서는 풍화에 의해 생성된 화학종이 주변 자연환경에 심각한 영향을 미치기도 한다. 본 연구에서는 이러한 관점에서 동결/융해 실험을 활용한 풍화가속 실험을 이미 풍화를 받은 암석과 신선한 암석을 대상으로 실시하고 각 암석의 표면 변화를 다초점 레이저 현미경으로 관찰하고 IC/ICP-MS를 활용하여 화학종 생성에 대한 분석을 실시하였다. 풍화가 진행됨에 따라 표면의 거칠기는 완화되는 것을 확인하였고 주변환경에 영향을 미칠 수 있는 화학종은 풍화를 받는동안 양이 증가하는 것을 확인하였다. 본 연구 결과는 암석이 노출된 지역에서의 공학적/환경학적 안전성을 평가하는 기초 자료로 활용될 수 있을 것이다.

• 지질공학
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• 제25권2호
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• pp.165-178
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• 2015

Physical and chemical weathering degrades rock, affecting its structural properties and thus the stability of stone buildings or other structures. Confocal laser scan microscopy (CLSM) is used here to observe temporal changes in the surface roughness of rock samples under simulated accelerated weathering. Samples were pressurized to 50, 55, or 70 MPa using a pressure frame, and subjected to freeze/thaw cycling controlled by a thermostat. The temperature was cycled from -20℃ to 40℃ and back. After each 20 cycles, CLSM was used to assess the change in surface roughness, and roughness factors were calculated to quantify the progression of the surface condition over time. Variations in cross-section line-roughness parameters and surface-roughness parameters were analyzed for specific parts of the sample surfaces at 5× and 50× magnification. The result reveals that the highest and lowest values of the roughness factors are changed according to elapsed time. Freezing/thawing at high pressure caused larger changes in the roughness factor than at low pressure.

• 한국식품영양과학회지
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• 제28권1호
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• pp.1-8
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• 1999

Starch was isolated from nine Korean sweet potato varieties(Shinmi, Seangmi, Yulmi, Shinyulmi, Sunmi, Jeungmi, Mokpo 26, Mokpo 29, and Mokpo 30) and analysed in its physicochemical properties in comparison with a commercial sweet potato starch(Kumokanyu) imported from China. Protein content in the isolated starch was highest(1.1%) in Mokpo 29 and lowest(0.3%) in Kumokanyu, whereas lipid content was equally less than 0.2%. Pasting analysis by Rapid Viscoanalyser(RVA) showed that Yulmi starch had the lowest pasting temperature(70.2oC) whereas Kumokanyu did the highest one (74.3oC). Under a differential scanning calorimetry(DSC), however, Kumokanyu showed the lowest onset temperature(61.8oC) and enthalpy(42.0 J/g) for crystal melting. Shinyulmi showed the highest peak viscosity of the starch paste, but shear thinning was significant like commercial potato starch. Kumokanyu, however, displayed the least peak visicosity but good shear stability. With the starch gels prepared at 4oC, Mokpo 29 showed the highest hardness, whereas Shinyulmi did the lowest one. Against repeated freeze thawing treatments, the starch gel of Kumokanyu was most stable, and among the Korean varieties, Yulmi, Shinyulmi, Jeungmi and Mokpo 26 had good stability. According to the chain distribution analysis, Shinyulmi and Mokpo 29 consisted of larger quanitites of shorter amylopectin chains than Kumokanyu, potato and corn starches.

• 한국식품조리과학회지
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• 제27권5호
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• pp.507-522
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• 2011

In this study, samples of wheat flour and dough were prepared by adding of 1, 3, or 5% branched dextrin, which is produced from the amylopectin of waxy corn starch using a cyclization reaction with a branching enzyme. The samples were then evaluated qualitatively in terms of farinogram, viscogram, and extensogram characteristics. The fermentation power of dough expansion, extensogram characteristics, specific volume, baking loss, external/internal surface appearance, and sensory qualities were also examined after 4 weeks of storage at -20$^{\circ}C$ to determine the effect on freeze-thaw stability and quality improvement of branched dextrins in the soft roll bread formulation. Furthermore, the samples along with a control were compared regarding their quality characteristics, including changes in moisture content, water activity, color, and textural characteristics during a storage period of 4 days at 20$^{\circ}C$ to determine the effect on preventing retrogradation of the branched dextrin. As the branched dextrin content increased, area and extensibility increased, whereas water absorption, fermentation power of dough expansion, resistance/extensibility ratio, baking loss, and brownness of the crust decreased. However, the control group presented significantly higher peak viscosity, resistance, specific volume, taste, overall acceptability, moisture content, water activity, springiness, cohesiveness, and resilience values than those of the branched dextrin samples, whereas lightness, hardness, and chewiness showed the reverse effect. As the storage period increased, lightness, hardness, and chewiness increased, whereas cohesiveness decreased. In conclusion, the results indicate that adding 1~3% branched dextrin into a soft roll bread formulation from frozen dough had no positive effect on freeze-thaw stability or preventing retrogradation but may provide good nutritional properties.

• 한국약용작물학회지
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• 제19권2호
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• pp.126-135
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• 2011

Various herbal medicinal extracts were examined for the development of cosmetic products with anti-oxidative and anti-wrinkle activity. First, total polyphenol contents and DPPH radical scavenging activities of herbal medicinal extracts were measured. Most herbal samples, except for DW extracts of Portulaca oleracea, Caesalpinia sappan, Taraxacum platycarpum, Carthamus tinctorius, and 70% EtOH extracts of Taraxacum platycarpum and Carthamus tinctorius, showed DPPH radical scavenging activity over 80% at a concentration of $400{\mu}g/m{\ell}$. SOD-like antioxidant activity of DW extracts of Syzygium aromaticum, DW extracts of Eriobtrya japonica and 70% EtOH extracts of Sophora japonica was measured as 40%, 35% and 80%, respectively at a dry matter concentration of $50{\mu}g/m{\ell}$. In elastase inhibition assay, DW extracts of Lycium chinense ($50{\mu}g/m{\ell}$) and 70% EtOH extracts of Areca catechu ($50{\mu}g/m{\ell}$) showed 50% and 40% of inhibition, respectively. At a concentration of $1.250{\mu}g/m{\ell}$, DW extracts of Lycium chinense and 70% EtOH extracts of Areca catechu showed 10% and 30% of collagenase inhibition, respectively. Skin and lotion samples were prepared using the two herbal extracts of high anti-wrinkle activity: Lycium chinense extract and Areca catechu extract. The storage stability of skin and lotion containing each of the selected herbal extracts was evaluated. pH and viscosity were used as stability indicators for the stability test under different storage temperatures and freeze-thaw cycle conditions. The skin and lotion containing each of DW extract of Lycium chinense and 70% EtOH extract of Areca catechu was showed high pH and viscosity stability. The skin and lotion containing DW extracts of Lycium chinense showed relatively higher stability than the skin and lotion containing 70% EtOH extract of Areca catechu, at cycle chamber and freeze-thaw conditions. In summary, these results indicated that cosmetics containing DW extract of Lycium chinense were relatively stable, and this herbal extract could be used as a stable functional cosmetic material.

• 한국응용과학기술학회지
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• 제39권1호
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• pp.52-62
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• 2022

소변검사 전 냉/해동 반복과 해동 과정에 따라 대표적인 임상 화학검사 측정값의 변화를 확인함으로써 소변검사의 안정성과 품질 개선방안을 모색하고자 하였다. 조사 대상자는 모두 건강한 남성 10명이었으며 이들의 소변 검체를 이용하여 냉/해동 안정성(freeze and thaw stability) 실험을 진행하였다. Micro-albumin과 Amylase의 경우 시간이 경과 됨에 따라 37℃에서는 통계적 유의성은 없었으나, 42℃와 60℃에서는 시간의 경과에 따른 결과가 통계적으로 유의한 변동이 있었고, BUN, Creatinine, Uric acid와 Glucose에서는 통계적으로 유의한 변동이 있었다. Long term의 안정성 결과, 7일이 지난 후에는 Glucose의 변이는 증가하였고, 60℃에서는 Amylase가 감소하는 양상을 보였다. Glucose와 Amylase의 경우 시간의 경과에 따른 결과가 통계적으로 유의한 변동이 있었다. 신뢰성 있는 검사결과를 얻기 위해서는 소변 시료의 채취, 보관 및 저장 등을 비롯한 요검사의 정확한 표준화가 필요하며 생체 물질별 안정성 확보를 위한 조건들의 체계적 연구가 필요하다.

• 한국발생생물학회지:발생과생식
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• 제10권4호
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• pp.263-269
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• 2006

Tilapia 난과 혈청의 cysteine proteinase 저해제(cystatin)의 산업적 이용 적성을 평가하고자 이의 저온 저장성과 가열에 대한 열 안정성을 살펴보았다. Tilapia 난과 난의 균질 상등액을 $4^{\circ}C$에서 3일간 보관하면서 cystatin 활성도의 변화를 측정한 결과 난의 경우는 저장 중 큰 변화가 없었으나, 난 균질 상등액의 경우는 활성이 차츰 감소하여 저장 3일 후에는 초기 활성의 약 65%로 줄어들었다. 냉동과 해동에 따른 cystatin의 안정성을 살펴보기 위하여 난과 혈청을 $-20^{\circ}C$ 냉동과 상온 해동을 하루에 한 차례씩 반복한 결과, 난의 경우 5회 이상 냉동과 해동이 반복된 경우에는 활성이 차츰 감소하였으나, 혈청의 경우는 냉동-해동 cycle을 5회 반복하여도 cystatin 활성에 영향을 미치지 않았다. 난 cystatin의 열 안정성을 측정하기 위하여 $35^{\circ}C$와 $50^{\circ}C$에서 각각 30분간 가열하여 cystatin 활성을 측정한 결과 $35^{\circ}C$에서는 80% 이상의 활성이 유지되었으나 $50^{\circ}C$에서는 10% 미만으로 감소되었다. 반면에 혈청의 경우는 $50^{\circ}C$에서 30분 가열하여도 cystatin 활성이 감소하지 않고, $80^{\circ}C$의 고온에서 30분 동안 가열하여도 약 74%의 활성이 남아 있어 열에 매우 강한 특성을 보였다. 이상의 결과를 종합하면 난을 냉장저장할 때는 난을 파괴하지 않고 원상대로 보관하는 것이 난을 균질하여 원심분리한 상등액으로 저장하는 것보다 cysteine proteinase 저해제 활성을 더 오래 보존하는 방법이며, 난 cysteine proteinase 저해제는 냉동-해동 반복처리에도 비교적 안정하였으나 혈청은 난에 비하여 냉동-해동 반복처리에 대해 더욱 안정하였다. 열 안정성에 있어서는 난 cystatin은 열에 비교적 약한 반면 혈청 cystatin은 열에 매우 안정하였다. 따라서 tilapia 난과 혈청은 surimi 제조시 cysteine proteinase 저해제로서 활용가치가 있으며, 특히 혈청은 더욱 유용하다고 사료된다.