• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1334-1341
• /
• 2010

유망식생공을 실시한 사면에 집중강우가 유입되면 단위중량이 증가하여 중력방향으로 이동을 하게 되며, 그에 따라 망이 유실되는 경우가 많아, 이를 고려한 점착력 확보가 요구되고 있는 실정이다. 강우와 사고사례에 따른 분석을 통하여 적절한 점착력을 확보하기 위한 기준마련 및 제시를 통해 국도이용의 안정성을 확보하고자 한다.

• Journal of the Korean Society for Railway
• /
• v.6 no.4
• /
• pp.257-264
• /
• 2003

In electric motor coaches, the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the weight of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control algorithm which uses the maximum adhesive effort by instantaneous estimation of adhesion force using load torque disturbance observer. Based on this estimated adhesive effort, the re-adhesion control is performed to obtain the maximum transfer of the tractive effort.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.170-171
• /
• 2015

최근 고성능이며 유연하고 투명한 전자 기기의 제작에 대한 관심이 높아지고 있으며 이에 대한 연구가 많이 수행되고 있다. 유연 전자제품을 제작하기 위해서는 고성능의 전자소자를 스탬프를 이용해 모재에서 유연한 기판으로 옮겨 붙이는 전사공정이 필요하다. 성공적인 전사공정을 수행하기 위해 스탬프 표면의 점착력을 제어하는 것이 중요하며, 이를 위해 다양한 표면 패터닝 및 표면처리 방법이 연구되고 있다. 대기압 플라즈마 표면처리는 공정 과정이 단순하여 대면적 연속적 전사 장비에 적용하기에 적합한 표면처리 공정으로, 본 연구에서는 대기압 플라즈마 표면 처리된 스탬프의 점착특성을 조사하고, 표면 처리된 스탬프를 이용하여 전자소자의 전사여부를 확인하는 실험을 수행하였다. 플라즈마 처리되지 않은 스탬프 표면은 높은 접착력을 가지며, 이를 이용하여 전자소자를 모재에서 떼어낼 수 있었다. 반면에 스탬프에 대기압 플라즈마 표면처리를 하면 실리카 재질의 경화층이 형성되며 이 층에 의해 점착력이 감소하여 전자소자를 모재에서 떼어낼 수 없었다. 따라서 스탬프에 대기압 플라즈마 표면처리를 함으로써 스탬프와 전자소자 사이의 점착력을 변화시킬 수 있으며, 이를 이용하면 선택적 전사가 가능함을 확인하였다.

• Tunnel and Underground Space
• /
• v.25 no.3
• /
• pp.284-292
• /
• 2015

The generalized Hoek-Brown failure criterion, the strength parameters of which are determined by using the GSI index, is an empirical nonlinear failure criterion of rock mass and has been widely employed in various rock engineering practices. Many rock engineering practitioners, however, are still familiar with the description of the strength of rock mass in terms of friction angle and cohesion. In addition, almost all rock mechanics softwares incorporate the simple linear Mohr-Coulomb function. Therefore, it is necessary to provide a tool to implement the Hoek-Brown function in the framework of the Mohr-Coulomb criterion. In this study, the use of upper-bound solution of limit analysis for bearing capacity of a strip footing resting on the ground surface is proposed for the estimation of the equivalent friction angle and cohesion of rock mass incorporating the generalized Hoek-Brown failure criterion. The upper-bound bearing capacity is expressed in terms of friction angle by use of the relationship between tangential friction angle and tangential cohesion implied in the generalized Hoek-Brown function. The friction angle minimizing the upper-bound bearing capacity is taken as the equivalent friction angle. Through the illustrative implementations of the proposed method, the influences of GSI, $m_i$ and D on the equivalent friction angle and cohesion are investigated.

• Applied Chemistry for Engineering
• /
• v.18 no.5
• /
• pp.444-448
• /
• 2007

The effects of intra-particle composition on the adhesive properties and water dispersity of acrylic emulsion type pressure sensitive adhesives (PSAs) were investigated. In the case of PSA having uniform intra-particle composition, the higher holding strength made the water dispersity lower. By changing the intra-particle composition in hard core/soft shell type, however, it was possible to get PSAs showing both high holding strength and water dispersity. When the weight ratio of MAA/AA is 4/1, high holding strength, but low initial tack and very low water dispersity were observed in both cases of higher contents of (AA+MAA) in core and shell area. When the weight ratio of MAA/AA is 1/4, however, higher water dispersity and lower holding strength were indicated in the case of higher contents of (AA+MAA) in shell area.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.11
• /
• pp.33-40
• /
• 2015

Volcanic rocks in Jeju Island indicate the differences in geological and mechanical characteristics from region to region, and have vesicular structure caused by various environmental factors. In this study, triaxial compressive strength tests were conducted for intact rocks sampled in northeastern onshore and offshore, southeastern offshore and northwestern offshore of Jeju Island. The estimated cohesion and internal friction angle from the results of triaxial compression tests were compared and analyzed with absorption, a parameter representing the vesicular properties of basalts in Jeju Island. As a result, it was found that the relationship between cohesion and absorption could be classified clearly, considering two different linear relationships in bulk specific gravity and absorption. As the absorption increases, the cohesion decreases exponentially. In addition, the internal friction angle decreases almost linearly with increasing in the absorption, regardless of the relationships in bulk specific gravity and absorption.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.2
• /
• pp.117-127
• /
• 2010

Gound excavation is frequently executed in unsaturated soil conditions. In this paper, the effect of apparent cohesion in unsaturated soils on the ground behavior during underground excavation is studied. The VPPE (Volumetric Pressure Plate Extractor) test, the unsaturated triaxial test and the trap-door test were carried out to figure out how the behavior of soils varies depending on the variation of apparent cohesion. The test results show that the ground behavior is almost identical if the soil is either fully dry or fully saturated. However, if the soil is partially-saturated with the increase of water content, the ground behaves quite differently. In summary, the apparent cohesion in unsaturated soils plays key roles when excavating underground structures.

• Journal of Adhesion and Interface
• /
• v.1 no.1
• /
• pp.15-22
• /
• 2000

To prepare acrylic type pressure-sensitive adhesive, quarter polymers were synthesized from butylacrylate (BA), 2-ethylhexylacrylate (2-EHA), methyl methacrylate (MMA), 2-hydroxyethylmethacrylate (2-HEMA). The quarter polymer was identified by FT-IR. Molecular weight was measured by Gel Pearmeation Chromatograhy. Also, viscosity, solid content and peel strength were investigated. The peel strength was $160g_f/25mm$ when the volume ratio of feed monomer to solvent was 1.3:1 and the ratio was relevant to commercial usage. The pot life of adhesive was 30 s at the 50 m/min of heat treatment rate, and it indicated that the minimum drying time was 30 s. Not only weathering resistance keep up peel strength $160{\sim}180g_f/25mm$ after 1000 h, but also no residual remains.

• Journal of Conservation Science
• /
• v.23
• /
• pp.1-10
• /
• 2008

Consolidants based on tetraethoxysilane (TEOS) such as alkoxysilanes have been widely used for the consolidation of decaying stone heritages. Low-viscosity alkoxysilanes penetrate inside the decaying stone and polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the material. However, TEOS-based consolidants suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developed capillary force, which is typical for TEOS-based consolidants. We prepared new consolidants TEOS-based consolidants containing flexible (3-glycidoxypropyl)trimethoxysilane (GPTMS) and silica nanoparticles (or polyhedral oligomeric silsesquioxanes (POSS)) in order to reduce capillary force development during gel drying. Since the consolidants should have a good interaction with the component of the stone in order to connect the isolate grains of decaying stone, the adhesion interaction of the developed consolidants on the surface of the granite was macroscopically investigated by the ISO 2409 cross cutting test. The adhesion interaction decreased with the addition of silica nanoparticle and POSS while it increased with the addition of GPTMS in TEOS solution.

• Polymer(Korea)
• /
• v.33 no.4
• /
• pp.319-325
• /
• 2009

The solution polymerization was conducted to synthesize pressure sensitive adhesive for polarizer film using acrylic monomers. 2-Ethylhexylacrylate, butylacrylate, acrylic acid were used as acrylic monomers. The ratio was 2-ethylliexylacrylate:butylacrylate:acrylic acid=25:50:3.6 by reflecting $-40^{\circ}C$ of glass transition temperature in the pressure sensitive adhesive. When 1 wt% of coupling agent was added to the polymerized pressure sensitive adhesive, the light transmissivity was significantly increased. This result is due to the enhancement of adhesive power against liquid crystal cell by Si-O bond of coupling agents. Cross-linking agent was added by 0.5, 1.0, and 1.5 wt% with respect to the synthesized polymer. Initial tackiness decreased, while cohesion increased with increasing crosslinking agent. In the analysis of contact angle, the increase of crosslinking agents yielded the enhancement of surface energy, resulting in the decrease of contact angle. From the measurement of heat resistance, the acrylic pressure sensitive adhesive showed excellent heat resistance regardless of change in temperature and contents in crosslinking agent. In the observation of a cutting plane, the increased crosslinking agent represented a smoother and cleaner section. Comprehensively, the optimum additive amount of crosslinking agent was determined to be 1.0 wt% to monomer.