이 논문에서는 보행교의 진동 사용성 평가에 있어서 보행자의 이동 질량 관성 효과의 고려 여부, 보행 패턴 등을 고려한 보행 시나 리오 등에 따른 해석 결과를 제시하고, 그에 따라 보행교 설계 단계에서 동적 유한요소 해석을 통한 진동 사용성 평가에 있어 적절한 해석 방법과 유의점을 제안한다. 지간 40m의 강합성 박스 단면을 갖는 단경간 단순교 형식의 보행교에 대하여 보행자 밀도, 보행 속 도, 임의 보행, 동기화 보행 등을 고려한 보행 시나리오에 대한 가속도 응답을 분석한다. 해석 결과 고정 질량 해석 방법은 임의 보행 시 나리오 해석에서 이동 질량 해석과 큰 차이를 보이지 않으며 진동 사용성 평가시에는 더 넓은 진동수 대역을 가진할 수 있는 임의 보행 시나리오를 고려하는 것이 바람직할 수 있음을 보였다.

As the design life of nuclear power plants are coming to the end, starting with Kori unit 1, nuclear power related organizations have been actively conducted research on the treatment of nuclear power plant decommissioning waste. In this study, among various types of radioactive waste, stabilization and volume reduction experiments were conducted on radioactive contaminated soil waste. Korea has no experience in decommissioning nuclear power plants, but a large amount of radioactively contaminated soil waste was generated during the decommissioning of the KAERI research reactor (TRIGA Mark- II) and the uranium conversion facility. This case shows the possibility of generating radioactive soil waste from nuclear power plants and nuclear-related facilities sites. Soil waste should be solidified, because its fluidity and dispersibility wastes specified in the notification of the Korea Nuclear Safety and Security Commission. In addition, the solidified waste forms should have sufficient mechanical strength and water resistance. Numerous minerals in the soil are components that can make glass and ceramics, for this reason, glass-ceramic sintered body can be made by appropriate heat and pressure. The sintering conditions of soil were optimized, in order to make better economical and more stable sintered body, some additives (such as additives for glass were mixed) with the soil and sintering experiments were conducted. Uncontaminated natural soil was collected and used for the experiment after air drying. Moisture content, pH, bulk density, and organic content were measured to understand the basic properties of soil, and physicochemical properties of the soil were identified by XRD, XRF, TG, and SEM-EDS analysis. In order to understand the distribution by particle size of the soil, it was divided into Sand (0.05–2 mm) and Fines (< 0.05 mm). The green body was manufactured in the form of a cylinder with a diameter of 13mm and a height of about 10mm. Appropriate pressure (> 150 MPa) was applied to the soil to make a green body, and appropriate heat (> 800°C) was applied to the sintered body to make a sintered body. The sintering was conducted in a muffle furnace in air conditions. The volume reduction and compressive strength of the sintered body for each condition were evaluated.

현무암 섬유를 함유한 BFRP 시트와 복합섬유 패널로 보강한 정사각형 단면 철근콘크리트 기둥에 대한 반복하중 실험을 수행하여 지진 거동을 검토하였다. 30%가량의 상당한 수준의 축하중비 조건 하에서 전단 손상이 발생하였음에도 불구하고, 보강 실험체에서 변위연성도 및 에너지 소산능력의 증가를 확인하였다. 실험체의 파괴 모드는 휨-전단 고연성 파괴로 분류 되며, 철근콘크리트 구조물에서 자주 관찰되는 파괴 모드이다. 하지만 이러한 파괴에 이르는 정사각형 단면 철근콘크리트 기둥에 BFRP을 포함한 복합재료 보강이 미치는 영향에 대한 연구가 현재까지 광범위하게 이루어지지는 않았다. 복합재료로 보강한 철근콘크리트 기둥의 휨-전단 거동을 보다 깊이 이해하는데 본 연구의 결과가 기여할 것으로 기대한다.

In this research, carbon nanotubes(CNT) and graphene nanoplates(GnP) are deposited on the surface of carbon fibers(CF) at once. Investigating the effect between CNT and GnP on increasing the interfacial and mechanical properties of carbon fiber reinforced epoxy composites(CFRP). The cross section of the CFRP composites indicates that the GnPs/CNTs hybrid coating exhibits significantly higher mechanical performance in all coating samples. The interlayer shear strength of the GnPs/CNT hybrid coated CFRP composite was 90% higher than that of the uncoated CF composite. The flexural and tensile strength of CFRP composites using GnPs /CNT hybrid coatings were improved by 52% and 70%, respectively, compared to uncoated CF.

FRP 보강이 RC 기둥의 내진성능에 미치는 효과를 평가하고자 다양한 실험 연구가 수행되어 왔다. 그 중 많은 연구가 휨지배를 받는 원형 단면 RC 기둥의 거동에 초점을 맞추었다. 단면 형태가 FRP 보강에 의한 구속효과에 영향을 주기 때문에, 단면 형태에 따라 보강효과 및 최종손상 양상이 다를 수 있다. 또한, 기존 RC 기둥 중 일부는 현재의 구조기준을 만족하지 못하는 설계로 인하여 취성적인 파괴 모드인 전단 파괴가 발생할 것으로 여겨진다. 이 두 가지 조건을 고려하여, 현무암 섬유를 함유한 FRP 시트와 복합섬유 패널로 보강한 정사각형 단면을 가진 짧은 RC 기둥의 전단 거동을 살펴보기 위하여 반복하중 실험을 수행하였다. 실험 결과에서 전체적인 전단 거동의 개선을 확인하였으며, 이러한 경향은 모서리 부분에서 심각한 손상이 발생할 때까지 유효하였다.

현재 우리나라에서 운영 중인 교량 중 30년 이상 된 교량이 전체의 약 11%를 차지할 정도로 노후교량의 수가 증가하고 있다. 따라 서 교량의 노후화에 따른 영향을 고려한 내진성능 평가방법의 개발이 필요하다고 볼 수 있다. 예제 교량으로는 포트받침, 탄성고무받 침과 납-고무받침을 가진 3가지의 강합성 상자형 거더교를 선정하고, opensees 프로그램을 사용하여 구조해석모델을 작성하였다. 본 연구에서는 교량의 노후도를 교각의 주철근과 띠철근의 부식에 의한 면적의 감소로 반영하였다. 교각의 노후화 정도로는 5%, 10%, 25%, 50%의 4가지 조건을 사용하였다. 입력지진으로는 근거리 지진과 원거리 지진을 각각 40개씩 사용하였으며, 노후화 정도에 따른 예제교량의 교각에 대한 최대변위와 최대 전단력 응답을 구하여 비교하였다. 노후도가 증가할수록 힘-변위 관계에서 교각의 강도 저하가 발생함을 알 수 있으며, 이로 인하여 교각의 변위응답이 증가함을 알 수 있다. 교각의 노후도에 따른 변위응답과 전단저항능력의 영향을 분석하기 위하여 변위비(Dratio)와 전단력비(Fratio)를 정의하여 평가하였다. 예제교량의 고유주기가 길어질수록 노후도에 따른 변위비(Dratio)의 증가가 크게 나타남을 알 수 있으며, 전단력비(Fratio)의 감소 경향은 작게 나타남을 알 수 있다.

막 생물 반응기(MBR)에서, 활성화 된 슬러지는 생물학적 성분을 분해하고 막 공정은 이 부유 물질인 박테리아를 분리시킨다. 그러나 MBR에서의 주요 문제는 ‘막 오염’이다. 이 리뷰에서는 ‘막 오염’을 극복하기 위하여 제시된 ‘복합막’을 논의하고 있다. ‘복합막’은 탄소 또는 비탄소 재료 포함하는 막으로 분류할 수 있다. 이 복합막의 친수성은 그래핀, 산화그래핀 (GO) 및 탄소 나노 튜브 또는 그들의 변형 된 부분을 깨끗한 막에 도입시킬 때 향상된다. 이산화규소(SiO2) 또는 이산화티타 늄(TiO2)과 같은 무기 물질 또한 막의 물 흐름을 증가시키기 위해 복합막 형성에 통합된다.

In this study, the formation, microstructure, and wear properties of Colmonoy 88 (Ni-17W-15Cr-3B-4Si wt.%) + Stellite 1 (Co-32Cr-17W wt.%) coating layers fabricated by high-velocity oxygen fuel (HVOF) spraying are investigated. Colmonoy 88 and Stellite 1 powders were mixed at a ratio of 1:0 and 5:5 vol.%. HVOF sprayed selffluxing composite coating layers were fabricated using the mixed powder feedstocks. The microstructures and wear properties of the composite coating layers are controlled via a high-frequency heat treatment. The two coating layers are composed of γ-Ni, Ni3B, W2B, and Cr23C6 phases. Co peaks are detected after the addition of Stellite 1 powder. Moreover, the WCrB2 hard phase is detected in all coating layers after the high-frequency heat treatment. Porosities were changed from 0.44% (Colmonoy 88) to 3.89% (Colmonoy 88 + ST#1) as the content of Stellite 1 powder increased. And porosity is denoted as 0.3% or less by inducing high-frequency heat treatment. The wear results confirm that the wear property significantly improves after the high-frequency heat treatment, because of the presence of wellcontrolled defects in the coating layers. The wear surfaces of the coated layers are observed and a wear mechanism for the Ni-based self-fluxing composite coating layers is proposed.

Laminate composites composed of 0.95Pb(Zr0.52Ti0.48)O3-0.05Pb(Mn1/3Sb2/3)O3 piezoelectric ceramic and Fe-Si-B based magnetostrictive amorphous alloy are fabricated, and the effect of control of the areal dimensions and the thickness of the piezoelectric layer on the magnetoelectric(ME) properties of the laminate composites is studied. As the aspect ratio of the piezoelectric layer and the magnetostrictive layer increases, the maximum value of the ME voltage coefficient(αME) increases and the intensity of the DC magnetic field at which the maximum αME value appears decreases. Moreover, as the thickness of the piezoelectric layer decreases, αME tends to increase. The ME composites exhibit αME values higher than 1 Vcm−1Oe−1 even at the non-resonance frequency of 1 kHz. This study shows that, apart from the inherent characteristics of the piezoelectric composition, small thicknesses and high aspect ratios of the piezoelectric layer are important dimensional determinants for achieving high ME performance of the piezoelectric-magnetostrictive laminate composite.

본 연구에서는 PAN과 폴리설폰의 두 지지체와 PEBAX 1657, 2533 두 선택층을 형성하였고, 지지체의 투과저항으로 인한 복합 막의 기체 투과도와 선택도의 차이를 확인하였다. 투과선택도를 향상시키기 위하여 PEG를 첨가하여 20에서 50 wt% 범위에서 농도를 달리하여 막을 제조한 후 CO2, N2 기체 투과성능을 측정하였다. 투과 성능이 가장 우수한 복합막의 물성 평가로써, PEBAX 복합평막의 미세구조를 관찰하였고, PEG 함량의 증가로 인한 Polyether 유리전이온도의 변화를 확인하였다. PEG 첨가제에 의한 PEBAX 복합평막은 에틸렌옥사이드 그룹으로 이루어진 PEG가 이산화탄소에 친화성을 가지고 있어서, PEG가 증가함에 따라 이산화탄소의 투과도를 향상시킬 수 있었다.

Membrane fabrication is a critical area that hampers forward osmosis (FO) technology from industrialization. Herein, electrospun poly(vinyl alcohol) (PVA) nanofiber (NF) was used as a support layer for thin film composite (TFC) FO membrane. The PVA NF was incorporated with sulfonated graphene oxide (sGO). The oxygenous-rich sGO enhanced the hydrophilicity and mechanical strength of PVA NF as revealed by contact angle and tensile strength measurements, and pure water flux. On this support, the active polyamide layer was formed through interfacial polymerization. Meanwhile, FO performance of sGO/PVA TFC membrane is currently being evaluated. This work was supported by NRF of Korea funded by the Ministry of Science and ICT (2016R1A2B1009221 and 2017R1A2B2002109) and Ministry of Education (2009-0093816 and 22A20130012051 (BK21Plus)).

Multiwall carbon nanotubes (MWCNT) with two different (L/D) aspect ratios (7±2 μm/140±30 nm and 0.5–2 μm/8–15 nm) were surface treated using nitric acid (HNO3) and polyethyleneimine (PEI) prior to their deposition on carbon fibers (CF). Before the hierarchical reinforcement with CF-MWCNT, the CFs were treated with 3-glycidoxypropyltrimethoxysilane, a coupling agent (Z6040) and with poly(amidoamine) (PAMAM) a dendrimer containing an ethylenediamine core and amine surface groups. The MWCNT were deposited on the CF using two methods, by electrostatic attraction and by chemical reactions. The changes in the CF surface morphology after the MWCNT deposition were analyzed using SEM, which revealed a higher density and uniform coverage for the PAMAM-treated CF and the short MWCNTs. The interfacial adhesion of the composite materials was evaluated using the single fiber fragmentation technique. The results indicated an improvement in the interfacial shear strength with the addition of the short-MWCNTs treated with acid solutions and grafted onto the surface of the CF fiber using electrostatic attraction.

Al/expanded graphite was successfully synthesized through a facile method including ultrasonic and heat treatment. In the well-designed three dimensional structure, expanded graphite(EG) works as a conductive matrix to support coated Al particles. The effects of the fabrication parameters on the microstructures and thermal conductivities of these composites were investigated. As a result, it was found that composites with graphite volume fraction of 17.4-69.4% sintered at 600 oC/45 MPa exhibit in-plane thermal conductivities of 380-940 W/mK, over 90 % of the predictions by rule of mixture. According to the non-destructive analysis results, the synergistic enhancement was caused by the formation of efficient thermally conductive pathways due to the hybrid of the differently sized EG. The structure integrates the advantages of expanded graphite as a conductive support, preserving the electrode activity and integrity and improving the electrochemical performance.

In this paper, the method of vibration analysis for calculating the natural frequency is presented. This method is a simple but exact method of calculating natural frequencies corresponding to the modes of vibration for the cantilevered composite materials conical beam. The influence of natural frequency of the cantilevered composite materials conical beam is presented. This method may be extended to stability analysis of complex structureal elements.

Graphene oxide (GO) has received a lot of attention in membrane science for its CO2-philic nature, which can facilitate CO2 separation performance. In addition, GO has attractive properties for gas separation membrane material due to thin-film membrane formation and tunable transport channel. GO membrane can be generally prepared by coating GO nanosheets on microporous polymer supports for mechanical stability. However, the substrates for in thin GO layer should be carefully chosen for good adhesion between GO layer and support surface with maintaining good separation performance. In this study, we tried to modify the surface properties of high permeable support membranes by using gutter layer as an intermediate layer, and measured the gas transport properties of these GO thin-film composite membranes.

본 연구에서는 각기 다른 관능기를 가진 유기화된 무기입자를 sol-gel법을 이용해 제조하여 montorillonite가 가진 단점을 보완하였으며, 이를 sulfonated poly(arylene ether sulfone)(SPAES)고분자에 첨가해 복합막을 제막하였다. 제조 된 무기물은 사용한 실란화합물에 따라 상이한 색상 및 물성을 나타내었다. 최 종적으로 물리적 성능, 전기적 성능 등 복합막의 전반적인 물성변화를 나타내었으며 이에 따라 최적화된 관능기를 찾는 연구를 진행하였다.

To increase the capacitance of an Al electrolytic capacitor, the anodic oxide film, Al2O3, was partly replaced by an Al2O3-ZrO2 (Al-Zr) composite film prepared by the vacuum infiltration method and anodization. The microstructure and composition of the prepared samples were investigated by scanning electron microscopy and transmission electron microscopy. The coated and anodized samples showed multi-layer structures, which consisted of an inner Al hydrate layer, a middle Al- Zr composite layer, and an outer Al2O3 layer. The thickness of the coating layer could go up to 220 nm when the etched Al foil was coated 8 times. The electrical properties of the samples, such as specific capacitance, leakage current, and withstanding voltages, were also characterized after anodization at 100 V and 600 V. The capacitances of samples with ZrO2 coating were 36.3% and 27.5% higher than those of samples without ZrO2 coating when anodized at 100 V and 600 V, respectively.

In this study, the effect of temperature effect of the rubber matrix filled with nano sized silica particles composites with silica volume fraction of 19–25% was investigated by the Charpy impact test. The Charpy impact test was conducted in the temperature range from –40°C to 0°C. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles was considerably affected by temperature and it was shown that the maximum value was appeared at higher temperature between temperature tested and it was shown that the value of GIC increases as temperature tested increases. The major fracture mechanisms were matrix deformation, silica particle debonding and delamination, microcrack between particles and matrix, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact surfaces fracture.