• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.133-135
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• 2003

The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

• 센서학회지
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• 제24권6호
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• pp.419-422
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• 2015

Pure and Mo-doped ZnO hollow nanofibers were prepared by single capillary electrospinning and their gas sensing characteristics toward 5 ppm ethanol, trimethylamine (TMA), CO and $H_2$ were investigated. The gas responses and responding kinetics were dependent upon sensing temperature and Mo doping. Mo-doped ZnO hollow nanofibers showed high response to 5 ppm TMA ($R_a/R_g=111.7$, $R_a$: resistance in air, $R_g$: resistance in gas) at $400^{\circ}C$, while the responses of pure ZnO hollow nanofibers was low ($R_a/R_g=47.1$). In addition, the doping of Mo enhanced selectivity toward TMA. The enhancement of gas response and selectivity to TMA by Mo doping to ZnO nanofibers was discussed in relation to the interaction between basic analyte gas and acidic additive materials.

• 한국구조물진단유지관리공학회 논문집
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• 제22권2호
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• pp.133-140
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• 2018

본 연구에서는 중공형의 PHC말뚝과 강관말뚝을 합성한 중공형 콘크리트 충전 강관(HCFT)말뚝의 거동분석을 위한 수치해석 모델을 개발하였고 휨강도시험에 적용하여 모델의 타당성을 검증하였다. 개발된 비선형 유한요소해석 모델의 적정성을 파악하기 위해 실물 시험 결과와 비교하였고 이를 활용하여 HCFT말뚝에 적합한 접촉조건, PC강봉의 제원에 따른 효과, 콘크리트 두께에 따른 효과 등을 분석하였다. 소성응력분배법을 적용하여 HCFT말뚝의 휨강도 산정식을 제안하였고 시험 및 해석결과와 비교하여 활용성을 검증하였다. 본 연구의 결과는 HCFT말뚝의 최적설계 및 거동분석에 기초자료로 활용될 수 있을 것으로 판단된다.

• 한국소음진동공학회논문집
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• 제22권6호
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• pp.582-587
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• 2012

This paper presents a solution of the vibration reduction in the hollow shafts by using magentorehological( MR) elastomer. Proposed active damping structure is built by embedding the MR elastomers whose elastic modulus is controllable by an applied magnetic field. MR elastomers consist of synthetic rubber filled with micron-sized magnetizable particles. For reduction of vibration, dynamic damper of hollow shaft is designed by using MR elastomer and equipped in the hollow shaft for the application to drive shaft. Experiment results are shown through the experiments to confirm the effect of MR elastomer dynamic damper for vibration reduction. Thus, the designed damping structure can be applied to vibration absorber used in drive shafts as well as the propeller shafts.

• 대한금속재료학회지
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• 제49권12호
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• pp.950-955
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• 2011

In the present study, the formation of hollow Cu oxide nanoparticles through the oxidation process at temperatures from 200 to $300^{\circ}C$ has been studied by transmission electron microscopy with Cu nanoparticles produced by the plasma arc discharge method. The Cu nanoparticles had a thin oxide layer on the surface at room temperature and the thickness of this oxide layer increased during oxidation in atmosphere at $200-300^{\circ}C$ However, the oxide layer consisted of $Cu_2O$ and CuO after oxidation at $200^{\circ}C$ whereas this layer was comprised of only CuO after oxidation at $300^{\circ}C$ On the other hand, hollow Cu oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process.

• Steel and Composite Structures
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• 제31권2호
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• pp.173-185
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• 2019

This paper presents experimental and numerical investigations of aluminum tubular members subjected to combined bending and web crippling. A series of tests was performed on square hollow sections (SHS) fabricated by extrusion using 6061-T6 heat-treated aluminum alloy. Different specimen lengths were tested to obtain the interaction relationship between moment and concentrated load. The non-linear finite element models were developed and verified against the experimental results obtained in this study and test data from existing literature for aluminum tubular sections subjected to pure bending, pure web crippling, and combined bending and web crippling. Geometric and material non-linearities were included in the finite element models. The finite element models closely predicted the strengths and failure modes of the tested specimens. Hence, the models were used for an extensive parametric study of cross-section geometries, and the web slenderness values ranged from 6.0 to 86.2. The combined bending and web crippling test results and strengths predicted from the finite element analysis were compared with the design strengths obtained using the current American Specification, Australian/New Zealand Standard and European Code for aluminum structures. The findings suggest that the current specifications are either quite conservative or unconservative for aluminum square hollow sections subjected to combined bending and web crippling. Hence, a bending and web crippling interaction equation for aluminum square hollow section specimens is proposed in this paper.

• Computers and Concrete
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• 제24권3호
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• pp.185-192
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• 2019

In this paper, the buckling of micro sandwich hollow circular plate is investigated with the consideration of the porous core and piezoelectric layer reinforced by functionally graded (FG)carbon nano-tube. For modeling the displacement field of sandwich hollow circular plate, the high-order shear deformation theory (HSDT) of plate and modified couple stress theory (MCST) are used. The governing differential equations of the system can be derived using the principle of minimum potential energy and Maxwell's equation that for solving these equations, the Ritz method is employed. The results of this research indicate the influence of various parameters such as porous coefficients, small length scale parameter, distribution of carbon nano-tube in piezoelectric layers and temperature on critical buckling load. The purpose of this research is to show the effect of physical parameters on the critical buckling load of micro sandwich plate and then optimize these parameters to design structures with the best efficiency. The results of this research can be used for optimization of micro-structures and manufacturing different structure in aircraft and aerospace.

• Steel and Composite Structures
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• 제31권4호
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• pp.329-340
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• 2019

An innovated type of the flat steel plate-lightweight aggregate concrete hollow composite slab was presented in this paper. This kind of the slab is composed of flat steel plate and the lightweight aggregate concrete slab, which were interfaced with a set of perfobond shear connectors (PBL shear connectors) with circular hollow structural sections (CHSS) and the shear stud connectors. Five specimens were tested under static monotonic loading. In the test, the influence of shear span/height ratios and arrangements of CHSS on bending capacity and flexural rigidity of the composite slabs were investigated. Based on the test results, the crack patterns, failure modes, the bending moment-curvature curves as well as the strains of the flat steel plate and the concrete were focused and analyzed. The test results showed that the flat steel plate was fully connected to the lightweight aggregate concrete slab and no obvious slippage was observed between the steel plate and the concrete, and the composite slabs performed well in terms of bending capacity, flexural rigidity and ductility. It was further shown that all of the specimens failed in bending failure mode regardless of the shear span/height ratios and the arrangement of CHSS. Moreover, the plane-section assumption was proved to be valid, and the calculated formulas for predicting the bending capacity and the flexural rigidity of the composite slabs were proposed on the basis of the experimental results.

• 한국구조물진단유지관리공학회 논문집
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• 제24권6호
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• pp.59-66
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• 2020

축소모형 팔각형 기둥 실험체 2개를 제작하여 일정한 축력 하에서 반복 횡하중을 가력하는 실험을 수행하였다. 실험체는 중실단면과 중공단면이고 모든 실험체의 횡방향 나선철근 체적비는 0.00206의 값을 갖는다. 실험체들은 휨-전단 파괴거동을 보였다. 본 논문에서는 실험결과에 따른 파괴거동과 내진성능을 분석하였다. 실험결과, 중공 실험체는 초기강성, 초기 균열양상, 에너지 소산능력 등의 구조성능이 중실 실험체와 유사한 거동을 보였으나, 중공 실험체의 경우에는 3% 변위비 이후에 횡력, 극한변위, 에너지소산능력이 현저하게 감소되었다.

• 한국기계가공학회지
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• 제21권7호
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• pp.64-70
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• 2022

The aim of this study is to improve the purification efficiency of odor gas by increasing the contact area between an odor gas and adsorbent. To analyze the flow in the adsorption tower, the flow characteristics in the hollow activated carbon-adsorption tower are identified by applying the loss model, which is a porous flow analysis model. The flow characteristics are investigated for pressure loss, velocity distribution, turbulent kinetic energy, and residence time distribution. The results show that the hollow adsorption tower performs better than the solid adsorption tower in terms of pressure loss and performance. The inner diameter of the hollow region inside the adsorption tower is 0.64 m (Di/Do = 0.37). Furthermore, the adsorbent performance is unaffected even when adsorbent stages are installed to replace the adsorbent.