• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.359-365
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• 1999

We have evaluated the performance and some physical properties of 25 automotive engine oils (21 domestic and 5 imported products) which are purchased on the market to verify the API(American Petroleum Institute) or ILSAC(International Lubricant Standardization and Approval Committee) certification marks attached on the products and to determine the necessity of the quality control of the engine oils on the market. 12 test items are chosen according to API engine oil specification, which are flash point, pour point, cold cranking simulator apparent viscosity, pumping viscosity, gelation index, HTHS(High Temperature High Shear viscosity), foam, high temperature foam, filterability, volatility, high temperature deposit(TEOST), phosphorus content. We have found one product which did not meet the API specification on gelation index, one on HTHS, four on foam, and one on volatility, which implies that the quality control system is in need to check the fidelity of the certification marks attached on the engine oils being marketed. In addition, this works raises the necessity of the upgrade of the present Korean engine oil specification.

• Elastomers and Composites
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• 제53권2호
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• pp.86-94
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• 2018

The effect of the NCO index and catalyst type on the thermal stability of poly(urethane-isocyanurate) (PUIR) foams was investigated to identify a method for enhancing the flame resistance of PUIR. PUIR foams were prepared using 4,4-diphenylmethane diisocyanate (MDI) and [(diethylene glycol)adipate]diol, which were synthesized by esterification of adipic acid and diethylene glycol. Dabco K-15, Dabco TMR-30, and Toyocat RX-5 were used as the catalysts for trimerization and gelation. The amount of urea and isocyanurate groups in PUIR was semi-quantitatively determined by normalizing their absorbance with the phenyl absorbance measured by FT-IR. The normalization data showed that Dabco TMR-30 effectively generated isocyanurate groups in PUIR. As a result, Dabco TMR-30 effectively raised the decomposition temperature and increased the 800 K and 900 K residues of the PUIR foam synthesized with an NCO index of 200.

• Advances in Traditional Medicine
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• 제8권2호
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• pp.178-186
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• 2008

In this study, ionotropic gelation method was used for the preparation of ibuprofen-loaded calcium alginate (CALG) and ethylenediamine (EDA) treated calcium alginate (EDA-CALG) microspheres. The effect of EDA-treatment on drug entrapment efficiency, particle size, morphology, swelling behavior and in vitro release characteristics of the microspheres was investigated by varying its concentration from 0.5 to 2% (v/v). The reduction in drug entrapment efficiency by a maximum of 44.60% was noted for EDA-CALG microspheres compared to untreated CALG microspheres. The particle size and swelling index of EDA-CALG microspheres were reduced with increasing EDA concentration. All the microspheres were observed to retain their spherical shapes with rough surfaces. EDA-CALG microspheres prepared using 1% and 2% v/v EDA, released almost all of its content within 7 h in pH 6.8 phosphate buffer, however, CALG microspheres were found to release the same within 3 h. The intensity of melting endothermic peak of ibuprofen reduced significantly at lower drug load as experienced from DSC thermograms. The FT-IR spectrum of pure ibuprofen, ibuprofen-loaded CALG and EDA-CALG microspheres showed the characteristic band of C = O stretching vibration of ibuprofen. Hence, this study revealed that EDA can be employed for the preparation of ibuprofen-loaded CALG microspheres to retard the drug release to some extent.

• 품질경영학회지
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• 제39권3호
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• pp.365-376
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• 2011

Robust design (RD) has emerged as a key feature in process design and development for more than twenty years. Many researchers and industrial engineers around the world have invested their intensive efforts to develop and apply RD in many fields in order to improve quality of output products. However, there is also room for improvement. The primary objective of this research is to determine "robust formulation" of a medicine by checking its gelation index. In order to achieve this target, based on the nature of problem, at first, a customized experimental format is designed for obtaining data. Second, time-depended responses based models are developed by the proposed inverse problem (IP) methodology. Third, an RD model based on mean square error (MSE) concept is introduced for time-depended responses. Finally, the proposed approach is illustrated by a case study while comparing obtained results to the response surface methodology (RSM) approach.

• Geomechanics and Engineering
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• 제19권4호
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• pp.307-314
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• 2019

Light construction waste (LCW) particles are pieces of light concrete or insulation wall with light quality and certain strength, containing rich isolated and disconnected pores. Mixing LCW particles with soil can be one of the alternative lightweight soils. It can lighten and stabilize the deep-thick soft soil in-situ. In this study, the unconfined compressive strength (UCS) and its mechanism of Construction Waste Stabilized Lightweight Soil (CWSLS) are investigated. According to the prescription design, totally 35 sets of specimens are tested for the index of dry density (DD) and unconfined compressive strength (UCS). The results show that the DD of CWSLS is mainly affected by LCW content, and it decreases obviously with the increase of LCW content, while increases slightly with the increase of cement content. The UCS of CWSLS first increases and then decreases with the increase of LCW content, existing a peak value. The UCS increases linearly with the increase of cement content, while the strength growth rate is dramatically affected by the different LCW contents. The UCS of CWSLS mainly comes from the skeleton impaction of LCW particles and the gelation of soil-cement composite slurry. According to the distribution of LCW particles and soil-cement composite slurry, CWSLS specimens are divided into three structures: "suspend-dense" structure, "framework-dense" structure and "framework-pore" structure.

• 한국식품과학회지
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• 제16권1호
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• pp.78-82
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• 1984

국내에서 생산되는 한천원조(寒天原藻)를 사용하여 건조방법(乾燥方法)이 한천(寒天)의 품질변화(品質變化)에 미치는 영향을 검토(檢討)하였다. 천일(天日) 건조(乾燥), 태양열(太陽熱) 집열(集熱) 건조(乾燥), 열풍(熱風) 건조(乾燥)($30^{\circ}C$), 대조구, 자연대류), 열풍(熱風) 건조(乾燥)($(30^{\circ}C$, 전처리구, 자연대류) 및 동결(凍結) 건조법(乾燥法)에서, 한천(寒天) 젤($1.0{\times}1.0{\times}34.0cm$)을 수분함량 1000%(D.B)까지 건조(乾燥)시키는 데 걸리는 시간은 96, 75, 67, 50 및 21시간 이었다. 천일(天日) 건조(乾燥), 태양열(太陽熱) 집열(集熱) 건조(乾燥), 동결(凍結) 건조(乾燥) 및 분무(噴霧) 건조법(乾燥法)에 의한 한천(寒天)의 젤리강도는 320, 370, 270 및 $360g/cm^2$로 나타났다. 열풍(熱風) 건조법(乾燥法)에 의한 젤리 강도는 건조온도(乾燥溫度) 한천(寒天) 젤의 전처리 유무(有無) 및 열전달(熱傳達) 형태(形態)에 의해 다르게 나타났으며, 타(他) 건조법(乾燥法)에 비해 비교적 높은 값을 나타냈다. 열풍(熱風) 건조시(乾燥時), 전처리 과정을 거친 한천(寒天) 젤의 건조속도(乾燥速度)가 대조구의 건조속도(乾燥速度) 보다 훨씬 증가하였으며, 한천(寒天) 젤의 건조속도(乾燥速度)의 증가에 따라 한천(寒天)의 젤리강도는 현저하게 증가되었다.

• Journal of Pharmaceutical Investigation
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• 제28권3호
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• pp.177-183
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• 1998

Low toxicity, reverse thermal gelation and high drug loading capabilities suggest that poloxamer 407 gels have great potential as a topical drug delivery system. Kojic acid (KA) is an antimelanogenic agent which has been widely used in cosmetics to whiten the skin color. However, it has the drawbacks of skin irritancy due to its acidic pH. Poloxamer gels of different polymer contents were formulated to overcome the problem and compared to the cream type formulations of either w/o/w multiple emulsion cream or o/w type emulsion cream. Using Franz diffusion cells mounted with a synthetic cellulose membrane (MWCO 12,000), drug release characteristics of the formulations were evaluated by the HPLC assay of KA concentration in the receptor compartment of pH 7.4 phosphate buffered saline solutions. Drug release from w/o/w multiple emulsion cream was controlled by oil membrane, showing the apparent zero order release kinetics. The KA release from the poloxamer gels was also controlled by the gel matrix, showing that drug release increased linearly as KA contents increase, but decreased exponentially as the polymer contents increase. In the skin irritancy test, the primary irritancy index(PII) of poloxamer gel base was lower than those of multiple emulsion cream base and o/w cream. Depending on KA contents or polymer contents in the gel. PH values in poloxamer gels were ranged from 1.3 to 2.0, which are interpreted as low or negligible irritation on skin. There was a good correlation between the log value of flux in drug release and PII value in skin irritation. It was possible to conclude that the poloxamer gels containing KA might be a good candidate for an antimelanogenic topical delivery system by virtue of the controlled release of the drug and the reduced skin irritancy.

• 한국축산식품학회지
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• 제36권2호
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• pp.267-274
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• 2016

The purposes of this study were to investigate the impacts of concentration levels of whey protein isolate (WPI) and inulin on the formation and physicochemical properties of WPI/inulin nano complexes and to evaluate their potential prebiotic effects. WPI/inulin nano complexes were produced using the internal gelation method. Transmission electron microscopy (TEM) and particle size analyzer were used to assess the morphological and physicochemical characterizations of nano complexes, respectively. The encapsulation efficiency of resveratrol in nano complexes was studied using HPLC while the potential prebiotic effects were investigated by measuring the viability of probiotics. In TEM micrographs, the globular forms of nano complexes in the range of 10 and 100 nm were successfully manufactured. An increase in WPI concentration level from 1 to 3% (w/v) resulted in a significant (p<0.05) decrease in the size of nano complexs while inulin concentration level did not affect the size of nano complexes. The polydispersity index of nano complexes was below 0.3 in all cases while the zeta-potential values in the range of -2 and -12 mV were observed. The encapsulation efficiency of resveratrol was significantly (p<0.05) increased as WPI and inulin concentration levels were increased from 1 to 3% (w/v). During incubation at 37℃ for 24 h, WPI/inulin nano complexes exhibited similar viability of probiotics with free inulin and had significantly (p<0.05) higher viability than negative control. In conclusions, WPI and inulin concentration levels were key factors affecting the physicochemical properties of WPI/inulin nano complexes and had potential prebiotic effect.

• Geomechanics and Engineering
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• 제33권1호
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• pp.29-40
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• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.