• 한국지하수토양환경학회지:지하수토양환경
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• 제11권3호
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• pp.12-19
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• 2006

본 연구에서는 우리나라의 경주에서 산출된 칼슘벤토나이트 콜로이드의 안정성에 대한 연구를 동적광산란 방법을 이 용하여 이온강도 및 pH 등의 지화학적 조건 변화에 따른 크기 변화를 관측함으로써 수행하였다. 속도론적 및 평형상태에서 pH 및 이온강도의 변화에 따른 칼슘벤토나이트 콜로이드의 크기변화를 관측하였다. 실험결과 칼슘벤토나이트 콜로이드의 안정성은 접촉시간, 매질의 이온강도와 pH 에 매우 크게 의존함을 보였으며 0.01 M $NaClO_4$ 이상의 이온강도에서는 고려된 대부분의 pH 에서 콜로이드가 불안정함을 보였다. 아울러 칼슘벤토나이트 콜로이드의 안정비 W와 CCC(Critical Coagulation Concentration) 등을 속도론적 응집 실험 자료들을 이용하여 계산하였다. 안정비 W는 이온강도가 증가함에 따라 감소하는 경향을 뚜렷하게 나타내었으며 pH 변화에 따른 W 값의 변화는 이온강도에 따라 다른 양상을 보였다. 또 pH 7 근처에서 칼슘벤토나이트 콜로이드의 CCC 는 약 0.05 M $NaClO_4$ 임을 알 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.135-142
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• 2000

A framework alternative to that of classical slope stability analysis is developed, wherein the soil mass is treated as a continuum and in situ soil stresses and strengths are computed accurately using inelastic finite element methods with general constitutive models. Within this framework, two alternative methods of stability analysis are presented. In the first, the strength characteristics of the soil mass are held constant, and the gravitational loading on the slope system is increased until failure is initiated by well-defined mechanisms. In the second approach, the gravity loading on the slope system is held constant, while the strength parameters of the slope mass are gradually decreased until well-defined failure mechanisms developed. Details on the applying both of the proposed methods, and comparisons of their characteristics on a number of solved example problems are presented.

• 펄프종이기술
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• 제31권1호
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• pp.79-88
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• 1999

The stability and performance (peel strength) of the acrylic copolymer and various modified rosin systems were investigated. The peel strength was measured over a wide range of scaling rates, and the influence of the viscoelasticity of the PSA(pressure sensitive adhesive) was considered. In the case of miscible systems, the peak of peel strength (PSA performance) over wide peel rates was changed and modified systematically with increasing glass transition temperature of the blends. The peak of the peel strength for blended systems shifts toward the lower rate side as glass transition temperature ($T_g$) of the blend increased. The influence of esterification of the rosin on performance and stability against deterioration was greatly modified by blending with rosin of glycerol ester and rosin pentaerythritol ester. The failure mode of the blend varies with the combination with acrylic copolymer and modified rosin, and cohesive failure was found at a lower peel rate while interfacial failure was found at a high peel rate. A few systems where a single Tg could be measured, despite the fact that two phases were observed microscopically, were detected.

• 보존과학회지
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• 제28권2호
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• pp.95-99
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• 2012

처리 농도 및 용매에 따른 PEG의 압축강도를 측정하고 치수안정화 효과와 비교 하여 전시 및 보관에 적합한 처리 조건을 설정하고자 하였다. 선행된 고함수율 수침고목재의 동결건조를 위한 PEG전처리 농도 및 용매 설정 연구에서 수용액 PEG 40% 전처리 후 진공동결건조가 치수안정성이 가장 우수하게 나왔다. 이번 연구에서는 약품의 처리 농도에 비례하여 압축강도가 증가하였으며, 용매에 있어서는 물이 t-butanol 보다 상대적으로 압축강도가 높게 나타났다. 특히 수용액에서 PEG 40%와 PEG 50%의 강도차가 6.6%(16kgf/$cm^2$)로 큰 차이가 없는 것으로 나타났다. 이상의 결과에 따라 수침고목재유물의 보존처리에서 치수안정성과 압축강도를 동시에 충족시키고자 할 때, 수용액 PEG 40% 전처리 후 동결건조를 실시하는 것이 가장 효과적인 것으로 확인되었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.621-626
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• 2010

According to development of method and device of Finite Element Analysis, the strength of welded joint is demonstrated by Finite Element Analysis not classical calculations. On the FEA, all of the joints for carbody are assumed to be ideal connections and the yield stress of welded joint is assumed to be the same to base metal. On these assumption, FEA is appropriate to evaluate the overall stability and strength of whole carbody. The classical calculation is appropriate to evaluate strength of specific welded joint and to determine the weld method and properties. Some project request strength calculation of the specific welded joints in addition to FEA, because of the demonstration of stability. The objective of this paper is the check of the consistency of the FEA result for the welded joints by the stress comparison between Detailed FE Model and classical calculation and the evaluation of the reliability of FEA result.

• 한국기계가공학회지
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• 제15권3호
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• pp.58-65
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• 2016

This study analyzed the structural weld strength for a door hinge for a field artillery ammunition support vehicle. In order to determine the optimal conditions, we measured the modal analysis and analyzed the leg length of a rear door hinge. From these methods, we acquired the vibration frequency of normal mode and the optimal welding leg length conditions. It was possible to obtain a structural stability for a rear door hinge of the field artillery ammunition support vehicle. In the future, this should be used as a reference source for the weld strength analysis of high vibration and high weight structures for another welding system design.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.423-430
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• 1999

A weathered residual soil is a soil-like material derived from the in situ weathering and decomposition of rock which has not been transported from its original location. Undisturbed sampling of residual soils is extremely difficult, which has an important effect on investigating the strength and compression characteristics. Thus, a special undisturbed sampling device (direct shear box with shoe) was developed and undisturbed samples were successfully obtained for direct shear tests, Direct shear testing was conducted under unsoaked and soaked condition. As a result, the shear strength of soaked samples was less than that of unsoaked samples, and it was verified that direct shearing of undisturbed samples can evaluate reasonably the shear strength and the slope stability.

• 한국도로학회논문집
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• 제16권4호
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• pp.21-33
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• 2014

PURPOSES: The purpose of this study was to break away from the workforce method using cold-mix asphalt mixtures and has a constant quality and has develop repair materials of pre-production asphalt-precast types. METHODS: The selection of the repair material was determined as the results obtained through physical properties of materials and the field applicability. In case of repair materials, values obtained through Marshall stability test & the dynamic stability test & retained stability test as well as the site conditions was considered. In case of adhesive, test results were obtained through examination of the bond strength(tensile, shear) and the field applicability of the adhesive was examined through combined specimens to simulate field applications. RESULTS : According to the results of laboratory tests, in the case of repair materials, Marshall stability and dynamic stability, retained stability of cold-mix reaction type asphalt mixture is the highest. In the case of adhesive, two-component epoxy-urea has a very high bonding strength(tensile, shear) was most excellent. According to the results of field tests, when epoxy-urea was excellent workability. Also, the repair body through actual mock-up test did not occur large deformation and fracture after 12 months. CONCLUSIONS : A suitable repair material is cold-mix reaction type mixture of asphalt-precast, a suitable adhesive is a two-component epoxy-urea.

• Archives of Pharmacal Research
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• 제15권2호
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• pp.176-183
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• 1992

The stabilizing effects of $\alpha$-$\beta$-$\gamma$- and dimethyl-$\beta$-cyclodextrins $(\alpha$-, $\beta$-, $\gamma$- and DM-$\beta-$-CyDs) on the degradation of hydrocortisone 17-butyrate (HC-17B) in aqueous solution was investigated. Hc-17B underwent a facile hydroxide ion-catalyzed rearrangement to the less active 21-butyrate ester by the apparent first-order kinetics, and maximum stability of HC-17B was obtained at around pH 4.0. The stability of HC-17B was increased by inclusion complexation with $\alpha$-, $\gamma$- and DM-$\beta$-CyD in the pH range of 2.0-8.0 examined, whereas $\beta$-CyD accelerated the degradation of HC-17B at the pH higher than 5.0. The effects of ionic strength, solvent, temperature and CyD concentration were also investigated. Stability constants and apparent degradation rate constants of HC-17B-$\gamma$-CyD and HC-17B-DM-$\beta$-CyD complexes were determined kinetically on the basis of 1:1 complexation. The results suggested that the inclusion complexation with $\gamma$-CyD or DM-$\beta$-CyD was most useful means to enhance the stability of the steroid.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1998년도 터널.암반역학위원회 박사학위 논문집
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• pp.3-34
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• 1998

The stability condition of rock slopes is greatly affected by the geometry and strength parameters of discontinuities in the rock masses. Rock slopes Involving movement of rock blocks on discontinuities are failed by one or combination of the three basic failure modes-plane, wedge, and toppling. In rock mechanics, practically all the parameters such as the joint set characteristics, the rock strength properties, and the loading conditions are always subject to a degree of uncertainty. Therefore, a reasonable assessment of the rock slope stability has to include the excavation of the multi-failure modes, the consideration of uncertainties of discontinuity characteristics, and the decision on stabilization measures with favorable cost conditions. This study was performed to provide a new numerical model of the deterministic analysis, reliability analysis, and reliability-based optimization for rock slope stability. The sensitivity analysis was carried out to verify proposed method and developed program; the parameters needed for sensitivity analysis are design variables, the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and rock slope geometry properties. The design variables to be optimized by the reliability-based optimization include the cutting angle, the support pressure, and the slope direction. The variability in orientations and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a greatly influenced on the rock slope stability. The stability of rock slopes considering three basic failure modes is more influenced by the selection of slope direction than any other design variables. When either plane or wedge failure is dominant, the support system is more useful than the excavation as a stabilization method. However, the excavation method is more suitable when toppling failure is dominant. The case study shows that the developed reliability-based optimization model can reasonably assess the stability of rock slopes and reduce the construction cost.