• Geomechanics and Engineering
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• 제18권4호
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• pp.439-448
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• 2019

The bearing capacity of roadside support is the key problem in gob-side entry retaining technology. To study the cooperative bearing characteristics of the roof-roadside support-floor along the gob-side entry retaining, a mechanical model of the composite structure of the roof-roadside support-floor was first established. A method for determining the structural parameters of gob-side entry retaining was then proposed. Based on this model, adaptability analysis of roadside support was carried out. The results showed that the reasonable width of the gob-side entry roadway was inversely proportional to the mining height, and directly proportional to the bearing strength of the roof and floor. And the reasonable width of the "flexible-hard" roadside support was directly proportional to its own strength, and inversely proportional to the width of the gob-side entry retaining. When determining the position and size of the roadside support along the gob-side entry retaining, the surrounding rock environment should be fully considered. Measured results from case study also show the rationality of the model and calculation method.

• 마이크로전자및패키징학회지
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• 제25권4호
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• pp.111-118
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• 2018

강성도가 서로 다른 두 polydimethylsiloxane (PDMS) 탄성고분자와 flexible printed circuit board (FPCB)로 이루어진 soft PDMS/hard PDMS/FPCB 구조의 강성도 국부변환 신축기판을 개발하기 위해 PDMS와 FPCB를 acrylic-silicone 양면테이프를 사용하여 접합한 후 접합공정에 따른 PDMS/FPCB 계면접착력을 분석하였다. 완전 경화된 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 접착한 FPCB의 pull 강도는 259 kPa이었으며, pull 시험시 PDMS와 silicone 접착제 사이에서 박리가 발생하였다. 반면에 $60^{\circ}C$에서 15~20분 유지하여 반경화시킨 PDMS에 acrylic-silicone 양면테이프의 silicone 접착제로 FPCB를 접착 후 $60^{\circ}C$에서 12시간 유지하여 PDMS를 완전 경화시키면 pull 강도가 1,007~1,094 kPa로 크게 향상되었으며, pull 시험시 계면 박리가 acrylic-silicone 양면테이프의 acrylic 접착제와 FPCB 사이에서 발생하였다.

• Geomechanics and Engineering
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• 제38권3호
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• pp.319-334
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• 2024

The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

• 대한토목학회논문집
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• 제34권2호
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• pp.367-375
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• 2014

최근 콘크리트 구조물의 보수 보강 및 리모델링 시 구조부재를 부착시키거나 고정하는데 있어서 시공의 유연성 및 용이성으로 후설치 앵커의 사용량이 증가하고 있는 실정이다. 전단하중을 받는 앵커는 강재와 콘크리트의 강도, 연단거리, 앵커간격 등에 따라 다양한 파괴모드를 보이며 대표적인 파괴모드는 강재 파괴, 콘크리트 파열 파괴, 콘크리트 프라이 아웃 파괴 등으로 나타난다. 본 연구에서는 매입깊이, 앵커간격, 연단거리 및 콘크리트 강도를 변수로 한 세트앵커의 전단 실험을 통하여 콘크리트에 매입된 후설치 앵커의 전단 파괴거동에 미치는 영향을 규명하는 것을 그 목적으로 한다. 매입깊이 변수의 실험 결과 매입깊이가 얕을수록 콘크리트 강도의 영향이 큰 것으로 나타났다. 앵커간격 변수의 실험 결과 모두 강재 파괴가 발생하였으며, 연단거리 변수의 실험 결과 매입깊이 이하인 경우 모두 콘크리트 파괴가 발생하였다. 동일한 변수의 실험 결과를 비교해 보았을 때 콘크리트 강도가 클수록 변위가 상대적으로 더 작게 나타났다.

• 한국강구조학회 논문집
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• 제24권5호
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• pp.521-534
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• 2012

본 연구에서는 합성보의 특징을 활용하고, 일부 고강도강 적용이 가능한 단면을 개발하여 이에 대한 기초연구를 실시하였다. 본 논문은 그 첫 번째로 단위부재인 합성보의 휨성능을 실험을 통해 평가하였다. 실험결과를 통해 기존 합성보의 공칭강도 산정식 적용여부를 검토하였고, 각 구성부재를 주요변수로 하여 실험하였다. 실험결과 신형상 U형 합성보의 내력평가는 콘크리트 압축강도와 강재의 인장강도에 의한 우력모멘트로 소요모멘트에 저항하는 것으로 평가하는 것이 적합하며, 보 춤 및 강판 두께에 비례하여 내력이 안정적으로 증가하였으며, 연성거동을 하는 것으로 나타났다.

• The Journal of Advanced Prosthodontics
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• 제12권1호
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• pp.22-32
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• 2020

PURPOSE. The aim of this study was to evaluate the microshear bond strength (µSBS) of four computer-aided design/computer-aided manufacturing (CAD/CAM) blocks repaired with composite resin using three different surface treatment protocols. MATERIALS AND METHODS. Four different CAD/CAM blocks were used in this study: (1) flexible hybrid ceramic (FHC), (2) resin nanoceramic (RNC), (c) polymer infiltrated ceramic network (PICN) and (4) feldspar ceramic (FC). All groups were further divided into four subgroups according to surface treatment: control, hydrofluoric acid etching (HF), air-borne particle abrasion with aluminum oxide (AlO), and tribochemical silica coating (TSC). After surface treatments, silane was applied to half of the specimens. Then, a silane-containing universal adhesive was applied, and specimens were repaired with a composite, Next, µSBS test was performed. Additional specimens were examined with a contact profilometer and scanning electron microscopy. The data were analyzed with ANOVA and Tukey tests. RESULTS. The findings revealed that silane application yielded higher µSBS values (P<.05). All surface treatments were showed a significant increase in µSBS values compared to the control (P<.05). For FHC and RNC, the most influential treatments were AlO and TSC (P<.05). CONCLUSION. Surface treatment is mandatory when the silane is not preferred, but the best bond strength values were obtained with the combination of surface treatment and silane application. HF provides improved bond strength when the ceramic content of material increases, whereas AlO and TSC gives improved bond strength when the composite content of material increases.

• 한국구조물진단유지관리공학회 논문집
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• 제19권3호
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• pp.55-63
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• 2015

콘크리트용 후설치 세트앵커는 콘크리트가 경화된 후에 설치되는 앵커이며 시공 장비의 발달과 시공의 유연성 및 용이성으로 사용량이 증가하고 있는 실정이다. 전단하중을 받는 앵커는 강재 파괴, 콘크리트 파열파괴, 콘크리트 프라이아웃 파괴 등의 대표적인 파괴모드를 보인다. 본 연구에서는 매입깊이, 연단거리 및 콘크리트 강도를 변수로 한 세트앵커의 실험 및 유한요소 해석 결과를 통하여 콘크리트에 매입된 저하중용 후설치 세트앵커의 전단 파괴거동에 미치는 영향을 규명하는 것을 그 목적으로 한다. 매입깊이 변수의 실험 결과 매입깊이가 얕을수록 콘크리트 강도의 영향이 큰 것으로 나타났다. 연단거리 변수의 실험 결과 동일한 파괴모드를 보이면서 콘크리트 강도의 영향이 크지 않은 것으로 나타났다. 강재 파괴가 발생한 실험 결과를 비교해 보았을 때 콘크리트 강도가 클수록 변위가 상대적으로 더 작게 나타났다.

• Korea-Australia Rheology Journal
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• 제20권2호
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• pp.89-94
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• 2008

To satisfy good mechanical and optical properties of polymer-coated film products, it will be indispensable to elucidate the molecular orientation of polymer chains within coating liquids in coating flows. Using hybridized numerical method between computational fluid dynamics (CFD) and Brownian dynamics (BD) simulations can provide the useful information for the better quality control of coated films. Flexible polymer chains, e.g., ${\lambda}$-DNA molecules here, change their conformation according to the flow strength and the flow type. The molecular conformation within the coated film on the web or substrate is quite different, because the polymer chains experience the complicated flow strength and flow types in flow field. Especially in the slot coating flow, these chains are more extended by the extension-like flow field generated in the free surface curvature just beyond the downstream die region. Also, the polymer chain extension beneath the free surface can be affected by the die geometry, e.g., the coating gap, changing flow field.

• 한국재료학회지
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• 제9권1호
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• pp.65-72
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• 1999

In order to minimize flexible printed circuit(FPC), which is used in computer, communication, medical facility, aviation space industry, it is required to improve the interfacial adhesion of polymide/epoxy or polyimide/polyimide consists of FPC. In this study, it was considered to improve the adhesion strength of polyimide/epoxy joint by introducing functional group on polyimide film and improving mechanical property of epoxy. Functional group on polyimide film was introduced by changing polyimide film surface to polyamic acid in KOH aqueous solution. The optimum conditions for surface modification were the concentration of 1M KOH and treatment time of 5min. Also, the optimum adhesion strength of polyimide/epoxy joint was obtained using rubber modified epoxy and polyamic acid as a base resin and curing agent of epoxy adhesive, respectively. The degree of surface modification of polyimide film examined with contact angle measurement of FTIR, thus modification of polyimide to polyamic acid was identified. Fracture surface of plymide/epoxy joint was analyzed by scanning electron microscopy, and modified polyamic acid reimidezed to polymide as increasing curing temperature.

• Journal of the Korean Wood Science and Technology
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• 제23권2호
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• pp.37-46
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• 1995

The substitution of carboxymethylated hydroxyl group in pulp revealed more hydrophilic than hydroxyl group. And then fibers were more flexible, swell more which leads to better conformation between fibers in turn this raise paper strength. In this paper, we tried to chemical modifyings of recycled fiber, OCCs(old corrugated containers). Many researchers have examined chemical modification of papermaking fiber by partial carboxymethylation(PCM) using a organic solvent processes. We made modified PCM processes adapted waters m replace of the organic solvent. Our testings for the optimum conditions on the new method, conditions as reaction time, temperature, liquor ratios were designed likely plant system. Freenesses(SR$^{\circ}$) were increased following on carboxyl content of the samples. Handsheets of untreated samples and partial carboxymethylated OCCs were made by optimum conditions on different concentrations of the reagent. As results, maximum 25% strength increasing effects were obtained by the new method.