• Elastomers and Composites
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• v.48 no.1
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• pp.76-84
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• 2013

The term 'Piezoresistive effect' describes a change in the electrical resistance of the material from deformed to its original shape by the external pressure, e.g., elongation, compression, etc. This phenomenon has various applications of sensors for monitoring pressure, vibration, and acceleration. Although there are many materials which have the piezoresistive effect, rubber (nano)composites with conductive fillers have attracted a great deal of attention because the piezoresistive effect appears at the various range of pressure by controlling the type of filler, particle size, particle shape, aspect ratio of particles, and filler content. Especially one can obtain the composites with elasticity and flexibility by using the rubber as a matrix. This paper aims to review the piezoresistive effect itself, their basic principles, and the various conductive rubber-composites with piezoresistive effect.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.186-193
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• 2003

최근 설계 및 시공되고 있는 국내 초고층 주거복합건물들의 유형과 구조설계내용들을 재점검하고 더 안전하고 경제적인 초고층 주거복합건물을 설계하기 위한 향후 과제로서 고강도 콘크리트 사용의 범용화와 구조적으로 유리한 기둥 배치계획과 횡력저항 요소로서의 Tubular 구조 및 Flat slab 등가골조 적용 등을 추가로 제시하며 또한 P.O.E의 구조적 측면에서의 도입자 인건비상승 및 후분양제도실시로 인한 공기단축등을 대비하는 철골조 아파트에 대한 지속적 상세연구가 필요하다고 판단된다. 또한 기둥의 부등축소문제, 내구성증대 및 거주성 향상문제 등도 관련 전문가들과 계속적 연구와 혐의가 필요한 것으로 생각된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.34-34
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• 1998

일반 항공기 및 상용 복합 구조재의 경우에는 내부에 결함이 생길 경우 유지 및 보수가 용이하나 복합재 압력 용기의 경우에는 다양한 환경 변화를 겪게 되며 또한 유지 및 보수가 힘들다는 제약 조건이 있으므로 단열재로 사용되는 인슈레이션 고무와 FRP간의 접착, 가황 고무와 미가황 고무 사이의 접착 등 여러 가지 이종 재질들 간의 접착이 매우 중요한 변수가 될 뿐만 아니라 압력 용기의 전체적인 성능에도 상당한 영향을 미치게 된다. 이러한 시스템들은 제작 조건에 따라 결함이 발생하는 빈도가 차이가 나며 특히 가혹한 환경 조건하에서도 내구성을 보여야 하므로 본 실험에서는 다양한 환경 조건, 성형 조건을 가지는 FRP/고무, 고무/고무 접착 시스템의 계면 접착력을 측정한 후 이로부터 환경 노화에 저항성이 강한 최적의 접착제 및 접착 조건 등을 확립하고자 하였다.

• Clean Technology
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• v.19 no.3
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• pp.272-278
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• 2013

Ethylene propylene diene terpolymer (EPDM) has been usually used for various applications. Bottom ash generated in thermoelectric power plant is hardly recycled. In this study, EPDM/bottom ash/talc composites were prepared by using roll-mill. Bottom ashes obtained from thermoelectric power plant were modified using surfactant. The processing materials used in this study were antioxidant, processing oil, cross-linking co-agent and softening agent. Morphology and physical properties of EPDM composites are investigated by using SEM, TGA, UTM and Rheometer. As a result, when modified ash and talc are added to EPDM composites, the tensile strength and modulus of EPDM composites were remarkably enhanced.

• Composites Research
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• v.26 no.1
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• pp.1-6
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• 2013

CNT-polypropylene (PP) composites were compounded by solvent dispersion method with uniform dispersion by using twin screw extruder. Damage sensing effects based on conductive carbon nanotubes (CNT) were evaluated to monitor the internal damage of CNT-PP composites using electrical resistance measurement. Mechanical and interfacial properties of CNT-PP composites were investigated and compared with neat PP. The mechanical properties of PP matrix were improved after adding CNT, because of the reinforcing effect of CNT fillers. In order to monitor the internal damage of CNT-PP composite, the change in electrical resistance of the composites was measured under fatigue loading and bending tests. CNT fillers exhibited good sensing under electrical resistance measurements. It is shown that CNT-PP composites with low CNT contents allow identifying critical cyclic loading, which are found to be accompanied with the internal failure.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.183-191
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• 2014

SNS uses the Internet as its base. It is created in order to achieve communication between the users. Up until now, most previous research were focused on the users of SNS. But, there are still a great deal of people who do not use or discontinuously use SNS. This is because users have natural resistance against SNS when using the service. In this study, time shortage perception, awareness of SNS, self-efficacy, suitability, information quality of SNS, subjective norm and privacy concern are considered as influence factors by previous research. An empirical study for Chinese students and internet users was conducted to identify how these factors influence perceived risk and perceived usefulness, and how this influence to user's resistance. This study can explain the reason why users don't use SNS and resist SNS use.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.87-97
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• 1990

There is the need to balance safety, economy and serviceability in all phases of society problems. This is especially true in structural code formulation. where a framework is established by which practicing structural engineers can be assured of designing structures that reasonably meet the above three objectives. The existing design codes, which are generally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of loads and resistances and the basic reliability concepts. The purpose of the present study is therefore to develop the realistic reliability-based design criteria to secure adequate safety arid reliability, and to derive the models for partial and combined resistance factor formats. To this end, the reliability levels of our existing design code for concrete structures are first evaluated and the target reliabilities are determined, the new code formats are evolved from these target reliabilities. The present study indicates that the proposed formats exhibit relatively-uniform reliability and reasonably take into account the different material characteristics of concrete and steel in concrete structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2741-2749
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• 2010

This paper presents the impact damage behavior of filament wound composite vessels and the effect of surface protective materials on their impact resistance. Using an instrumented impact testing machine, a series of impact tests was performed on the base panels and the protected panels (panels with surface protective materials of rubber, kevlar/epoxy or glass/epoxy laminates) that were cut from the full scale vessel. And the impact damage parameters were used to identify the effect of protective materials on the damage resistance of composite vessels. Damage resistance of the composite vessels was considerably affected by the protective materials regardless of the shape of the indenters. Among the protective materials, glass/epoxy laminates was the most effective mean for improving the damage resistance of composite vessels.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.115-119
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• 2001

The electrical properties of heavily drawn bundled Cu- Nb filamentary microcomposite wires were examined and correlated with the microstructural changes caused by thermomechanical treatments. The cross sectional shape of Nb filaments in wires fabricated by bundling and drawing appear straight or slightly curved. The different shape of Nb filaments is attributed to the break- up and cylinderization of Nb filaments during the bundling process at high temperatures. The resistivity of Cu-Nb microcomposites is predominantly controlled by electron scattering at Cu-Nb interfaces. The decrease of the conductivity below the annealing temperature of $400^{\circ}C$ is due to the increasing contribution of the scattering associated with coherency strains of needle- shaped precipitates. The slight decrease of the resistivity ratio (${\rho}_{295K}/{\rho}_{75K}$) is also due to the precipitation of Nb atoms. The increase in conductivity in Cu-Nb microcomposites at an annealing temperature of 50$0^{\circ}C$ is due to the coarsening and spheroidization of Nb filaments.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.63-69
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• 2019

Soldering technology has been used in electronic industry for a long time. However, due to solder fatigue characteristics, automotive electronics are searching the semi-permanent interconnection technology such as press-fit method. Press fit interconnection is a joining technology that mechanically inserts a press fit metal terminal into a through hole in a board, and induces a strong bonding by closely contacting the inner surface joining of the through hole by plastic deformation of press-fit terminal. In this paper, the bonding properties of press-fit interconnection are investigated with PCB hole size and surface finishes. In order to compare interconnection reliability between the press fit and soldering, the change in resistance of the press-fit and soldering joints was observed during thermal shock test. After thermal cycling, the failure modes are investigated to reveal the degradation mechanism both press-fit and soldering technology.