• 한국식품조리과학회지
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• 제9권1호
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• pp.43-51
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• 1993

Buckwheat protein isolate was tested for the effects of pH, addition of sodium chloride and heat treatment on solubility, emulsion capacities, emulsion stability, surface hydrophobicity, foam capacities and foam stability. The solubility of buckwheat protein isolate was affected by pH and showed the lowest value at pH 4.5, the isoelectric point of buckwheat protein isolate. The solubility significantly as the pH value reached closer to either ends of the pH, i.e., pH 1.0 and 11.0. The effects of NaCl concentration on solubility were as follows; at pH 2.0, the solubility significantly decreased when NaCl was added; at pH 4.5, it increased above 0.6 M; at pH 7.0 it increased; and at pH 9.0 it decreased. The solubility increased above $80^{\circ}C$, at all pH ranges. The emulsion capacity was the lowest at pH 4.5. It significantly increased as the pH approached higher acidic or alkalic regions. At pH 2.0, when NaCl was added, the emulsion capacity decreased, but it increased at pH 4.5 and showed the maximum value at pH 7.0 and 9.0 with 0.6 M and 0.8 M NaCl concentrations. Upon heating, the emulsion capacity decreased at acidic pH's but was maximised at pH 7.0 and 9.0 on $60^{\circ}C$ heat treatment. The emulsion stability was the lowest at pH 4.5 but increased with heat treatment. At acidic pH, the emulsion stability increased with the increase in NaCl concentration but decreased at pH 7.0 and 9.0. Generally, at other pH ranges, the emulsion stability was decreased with increased heating temperature. The surface hydrophobicity showed the highest value at pH 2.0 and the lowest value at pH 11.0. As NaCl concentrationed, the surface hydrophobicity decreased at acidic pH. The NaCl concentration had no significant effects on surface hydrophobicity at pH 7.0, 9.0 except for the highest value observed at 0.8 M and 0.4 M. At all pH ranges, the surface hydrophobicity was increased, when the temperature increased. The foam capacity decreased, with increased in pH value. At acidic pH, the foam capacity was decreased with the increased in NaCl concentration. The highest value was observed upon adding 0.2 M or 0.4 M NaCl at pH 7.0 and 9.0. Heat treatments of $60^{\circ}C$ and $40^{\circ}C$ showed the highest foam capacity values at pH 2.0 and 4.5, respectively. At pH 7.0 and 9.0, the foam capacity decreased with the increased in temperature. The foam stability was not significantly related to different pH values. The addition of 0.4 M NaCl at pH 2.0, 7.0 and 9.0 showed the highest stability and the addition of 1.0 M at pH 4.5 showed the lowest. The higher the heating temperature, the lower the foam stability at pH 2.0 and 9.0. However, the foam stability increased at pH 4.5 and 7.0 before reaching $80^{\circ}C$.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1279-1285
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• 2010

Our country has a tendency to build many structures by cutting mountainous areas due to geographical features. Among these construction done in our country, road construction take the first spot in rank. As the construction is done, fractured inclining plane is created inevitability because of the natural properties of mountainous areas. The stability of the fractured inclining planes and slope formed in the opening, which are developed at the time of construction, need to be evaluated. Also, reinforcement plans for these matters are necessary. This paper is to go through an examination on the fractured inclining surface that is developed at the time of construction, especially the composite inclining plane that consists of soil and rocks. Furthermore, evaluating the stability by performing an analysis on stereographic projection and limit equilibrium, based on the examination results. using the stability evaluations, applications were explored for reinforcement methods of construction that fits the geological characters of this inclining surface.

• Journal of the Korean Wood Science and Technology
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• 제36권6호
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• pp.121-129
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• 2008

고경도, 고광택, 고내마모성 및 고내산성 등의 물성이 요구되는 마루바닥재의 상도용 도료로는 물성이 우수하면서도 환경친화적인 자외선경화형 도료가 많이 사용되고 있다. 그 중에서도 특히 에폭시 아크릴레이트계의 올리고머는 높은 열안정성과 속경화 특성으로 인하여 목재내장재의 도료로써 많이 사용되고 있다. 본 연구에서는 아크릴레이트 관능기 수가 자외선 경화형 에폭시 아크릴레이트 도료의 열안정성 및 표면경도에 미치는 영향을 분석하고자 하였다. 조성분을 이루는 모노머, 올리고머, 광개시제 각각의 열분해 거동 및 아크릴레이트 관능기수가 달리 배합된 에폭시 아크릴레이트 도료의 열안정성을 열중량분석기(TGA)를 사용하여 평가하였으며, 열안정성과 물리적 물성과의 관계를 확인하기 위하여 진자경도계를 이용하여 표면경도를 측정하였다. 경화 전 후의 열분해 거동 및 표면경도를 비교한 결과, 자외선 경화 중에 발생하는 가교에 의해 도막의 열안정성이 부여되며, 관능기의 수가 많아짐에 따라 열안정성뿐만 아니라 표면경도도 향상됨을 확인하였다.

• 공업화학
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• 제8권2호
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• pp.252-261
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• 1997

여러 종류의 용제와 수지용액에 있어서의 $CaCO_3$ 안료의 분산 안정성을 Dynometer를 이용하여 조사하였다. Dynometer를 이용하여 비교적 단시간에 분산계의 분산 안정성을 평가할 수 있었으며, Dynometer를 이용한 분산 안정성 평가로부터 구한 $CaCO_3$ 안료의 용해성 파라미터, ${\delta}$는 11.62(${\delta}_d=8.04$, ${\delta}_p=5.05$, ${\delta}_h=6.70$)이었다. 안료와 친화력이 약한 용제가 첨가되는 경우 수지 용액내에서의 안료표면에의 수지 흡착층을 증가시켜 수지 용액내에서의 분산 안정성을 증가시켰다. 수지 용액 제조시 소량 첨가된 용제도 안료를 포함한 전체 분산계의 유동성과 분산 안정성에 큰 영향을 미친다는 것을 알 수 있었다.

• 터널과지하공간
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• 제34권1호
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• pp.54-70
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• 2024

생산이 완료된 노천광산 채굴적을 광미(광물찌꺼기) 적치 장소로 활용하는 방안은 기존 광미 적치 시설(TSF, Tailing storage facility)의 설치 공간 및 운영비용 문제 해결을 위한 대안으로 제시된다. 하지만 장기간에 걸쳐 적치된 광미는 주변 암반에 추가적인 하중으로 작용하여 광산의 역학적 안정성을 저해할 위험성이 존재한다. 본 연구에서는 호주 Marymia 광산의 사례를 참고하여 약 60,400 시간에 걸친 광미 적치 시나리오를 구축하였으며, 다양한 지하 채광장 형태 및 암반 조건에 따른 천반 수평필러의 역학적 안정성을 Sigma/W 해석 소프트웨어를 활용하여 분석하였다. 분석 결과, 광미 적치가 장기간 지속됨에 따라 천반 수평필러의 파괴 가능성이 유의미하게 증가함을 확인하였다. 해당 결과는 노천채굴적 내 광미 적치 시 광산 구조에 대한 역학적 안정성 고려가 필수적임을 시사한다.

• Elastomers and Composites
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• 제51권4호
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• pp.350-354
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• 2016

The surface properties of poly(methyl methacrylate) (PMMA) were investigated after accelerated weathering. Glossinesses, contact angles, surface free energies, thermal stability, and mechanical properties were investigated. The glossiness of the weathered PMMA was decreased with increasing exposure time. Contact angles and surface free energies were not overtly changed because the amount of oxygen on the surface was remained. PMMA was compounded with anti-block and antistatic agents using a co-rotating twin screw extruder to improve the durability. The PMMA composites showed better glossinesses after accelerated weathering while maintaining the contact angles, surface energy, thermal stability, and mechanical properties without significant changes.

• Journal of Pharmaceutical Investigation
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• 제40권spc호
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• pp.97-102
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• 2010

A novel surface-attached solid dispersion is designed to improve the solubility and oral bioavailability of poorly water-soluble drugs without crystalline change. Accordingly, it draws increasing interest because of excellent stability and no pollution for accomplishing enhanced solubility and bioavailability, which have recently been highlighted in connection with a number of higher value-added poorly water-soluble drugs. In addition, excellent stability can be attained when the poorly water-soluble drugs are not dissolved but dispersed in water and provide no crystallinity change. This solid dispersion is given by means of attaching the dissolved carriers such as hydrophilic polymer and surfactant to the surface of dispersed drug particles followed by changing the hydrophobic drug to hydrophilic form. The aim of the present review is to outline the preparation, physicochemical property and bioavailability of novel surface-attached solid dispersion with improved solubility and bioavailability of poorly water-soluble drugs without crystalline change.

• 대한물리의학회지
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• 제10권3호
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• pp.81-86
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• 2015

PURPOSE: Bridge exercises are broadly used to develop trunk co-activation patterns that promote spine stability. This study was to analyze the trunk muscle activity during bridge exercise with various shoulder support surface(stable, sling, Swiss ball). METHODS: The subjects were 20 healthy subjects in their twenties. Subjects were performed bridge exercise on 4 different shoulder support surfaces using stable and labile instruments. 1) Bridge exercise on a stable surface. 2) Bridge exercise with their shoulder on a stable bench. 3) Bridge exercise with their shoulder on a sling. 4) Bridge exercise with their shoulder on a Swiss ball. Rectus abdominis, erector spinae, internal oblique, external oblique muscle activities were measured using electromyography. RESULTS: There were significant differences in RA, EO muscles between performing each of the 4 exercises(p<.05). RA and EO was recorded the highest activity during the bridge exercise with their shoulder on a sling. The lowest activity was recorded during conventional supine bridge on a stable surface. There were no differences found for the EO/RA and IO/RA ratio. The EO/RA and IO/RA ratio was the highest in the bridge exercise with their shoulders resting on a stable bench. CONCLUSION: These findings suggest that change of shoulder support surface during bridge exercise may be useful for enhancing the trunk stability.

• Steel and Composite Structures
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• 제37권2호
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• pp.229-251
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• 2020

In this paper, dynamic buckling of a smart sandwich nanotube is studied. The nanostructure is composed of a carbon-nanotube with inner and outer surfaces coated with ZnO piezoelectric layers, which play the role of sensor and actuator. Nanotube is under magnetic field and ZnO layers are under electric field. The nanostructure is located in a viscoelastic environment, which is assumed to obey Visco-Pasternak model. Non-local piezo-elasticity theory is used to consider the small-scale effect, and Kelvin model is used to describe the structural damping effects. Surface stresses are taken into account based on Gurtin-Murdoch theory. Hamilton principle in conjunction with zigzag shear-deformation theory is used to obtain the governing equations. The governing equations are then solved using the differential quadrature method, to determine dynamic stability region of the nanostructure. To validate the analysis, the results for simpler case studies are compared with others reported in the literature. Then, the effect of various parameters such as small-scale, surface stresses, Visco-Pasternak environment and electric and magnetic fields on the dynamic stability region is investigated. The results show that considering the surface stresses leads to an increase in the excitation frequency and the dynamic stability region happens at higher frequencies.

• Journal of Welding and Joining
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• 제26권2호
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• pp.62-68
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• 2008

Effects of gravitational orientation on gas tungsten arc welding (GTAW) for 304 stainless steel were studied to determine the critical factors for weld pool formation, such as weld surface deformation and weld pool shape. This study was accomplished through an analytical study of weld pool stability as a function of primary welding parameters (arc current and arc holding time), material properties (surface tension and density), and melting efficiency (cross-sectional area). The stability of weld pool shape and weld surface deformation was confirmed experimentally by changing the welding position. The arc current and translational velocity were the major factors in determining the weld pool stability as a function of the gravitational orientation. A 200A spot GTAW showed a significant variation of the weld pool formation as the arc held longer than 3 seconds, however the weld pool shape and surface morphology for a 165A spot GTAW were 'stable', i.e., constant regardless of the gravitational orientation. The cross-sectional area of the weld (CSA) was one of the critical factors in determining the weld pool stability. The measured CSA ($13.5mm^2$) for the 200A spot GTAW showed a good agreement with the calculated CSA ($14.9mm^2$).