• Wind and Structures
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• 제36권3호
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• pp.149-160
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• 2023

Lightness and flexibility of membrane roofs make them very sensitive to any external load. One of the most important parameters that controls their behavior, especially under wind load is the sag/span ratio of edge cables. Based on the value of the pretension force in the edge cables and the horizontal projection of the actual area covered by the membrane, an optimized design range of cable sag/span ratios has been determined through carrying on several membrane form-finding analyses. Fully coupled fluid structure dynamic analyses of these membrane roofs are performed under wind load with several conditions using the CFD method. Through investigating the numerical results of these analyses, the behavior of membrane roofs with cables sag/span ratios selected from the previously determined optimized design range has been evaluated.

• 대한조선학회논문집
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• 제45권6호
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• pp.726-734
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• 2008

While the structural safety assessment of Cargo Containment System(CCS) in membrane type LNG carriers has to be carried out in consideration of sloshing impact pressure, it is very difficult to figure out its dynamic response behaviors due to its very complex structural arrangements/materials and complicated phenomena of sloshing impact loading. For the development of its original technique, it is necessary to understand the characteristics of dynamic response behavior of CCS structure under sloshing impact pressure. In this study, for the exact understanding of dynamic response behavior of CCS structure in membrane Mark III type LNG carriers under sloshing impact pressure, its wet drop impact response analyses were carried out by using Fluid-Structure Interaction(FSI) analysis technique of LS-DYNA code, and were also validated through a series of wet drop experiments for the enhancement of more accurate shock response analysis technique. It might be thought that the structural response behaviors of impact response analysis, such as impact pressure impulses and resulted strain time histories, generally showed very good agreement with experimental ones with very appropriate use of FSI analysis technique of LS-DYNA code, finite element modeling and material properties of CCS structure, finite element modeling and equation of state(EOS) of fluid domain.

• 대한조선학회논문집
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• 제45권6호
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• pp.735-749
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• 2008

For the development of the original technique of structural safety assessment of Cargo Containment System(CCS) in membrane type LNG carriers, it is necessary to understand the characteristics of dynamic response behavior of CCS structure under sloshing impact pressure. In the previous study, the wet drop impact response analyses of CCS structure in membrane Mark III type LNG carriers were carried out by using Fluid-Structure Interaction(FSI) analysis technique of LS-DYNA code, and were also validated through a series of wet drop experiments for the enhancement of more accurate shock response analysis technique. In this study, the characteristics of structural shock response behaviors of CCS structure were sufficiently figured out by careful examinations of the effects of specimen weight, drop height, incident angle, corrugation and stiffness of inner hull on its shock response behaviors. The shock response analysis of upward shooting fluid to inner hull was performed, and the reason of faster strain response than shock pressure one was also figured out.

• Journal of Plant Biology
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• 제38권3호
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• pp.275-280
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• 1995

The formation of osmiophilic globules related to the granal lysis has been investigated with a shade plant ginseng (Panax ginseng C. A. Meyer) exposed to full sunlight. The changes of chloroplast were examined as a function of time over 9 days under full sunlight exposure. The ultrastructure of ginseng leaf showed swelling of the granal thylakoid during an early stage of the light exposure. The thylakoid membrane faded and small electron-opaque dots were aggregated on the edges of the granal thylakoid membrane when the exposure time was increased over 1 day. Then, the sahpe of the grana changed into round. After the exposure over 3 days, there appeared many osmiophilic globules with multi-lamellated concentric structure. The globules at this stage were partly accumulated with osmiophilic substances. The outermost membrane of these multi-lamellated osmiophilic globules was attached to the stromal thylakoid membrane connecting to the deforming grana. The osmiophilic globules were elongated after 9 days. In this stage, the multi-lamellated structure was difficult to identify due to severe accumulation of osmiophilic substances. The number of the osmiophilic globules also increased along with the full sunlight exposure time. This observation leads us to believe that the multi-lamellated osmiophilic globules came from the deformation of grana.

• 자연, 터널 그리고 지하공간
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• 제21권2호
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• pp.103-116
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• 2019

Permanent sprayed concrete tunnel linings waterproofed with bonded membranes have been used at a number of important traffic projects over the last decade. Research has been carried out in several teams in order to increase the understanding of the function, properties and behavior of such linings under different loading and boundary conditions. The basic layout of this lining gives fundamental different system properties compared to the traditional lining systems. The main differences pertain to the groundwater exposure and the resulting hydraulic loading, the response of the concrete and membrane materials to this loading, as well as the geomechanically induced loading of the lining structure. The current understanding of the function and properties of such lining structures is presented in the paper based on review of recent research carried out in Norway, as well as field observations and monitoring carried over a several years. The influence of the water exposure on the final condition of the concrete and membrane materials has proven to be of vital importance for proper material testing and acceptance, assessments of the mechanical contribution of the bonded membrane, as well as assessments of the longterm durability of such linings. Obtaining realistic material parameters for the concrete and membrane materials subject to the boundary conditions posed by the groundwater exposure in an undrained structure is emphasized. Finally, some recent results from currently ongoing research on such linings, particularly the hydraulic response of the rock mass and the long term behavior of the concrete and membrane materials are presented.

• 멤브레인
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• 제17권1호
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• pp.14-22
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• 2007

본 연구는 투과증발법을 이용하여 수용액 중 미량의 목련 향 성분을 농축하는 방법으로, PVDF/PDMS 복합막을 제조하여 지지막의 구조와 활성층의 두께에 따른 분리능의 변화를 살펴보았다. PVDF 지지막은 제막조건인 응고액의 온도가 감소하고 고분자 농도가 증가함에 따라 지지층에서의 표면공극률과 기공의 직경이 감소함을 순수투과실험을 통해서 간접적으로 확인하였고, 복합막에 대한 지지막 구조의 영향을 투과 mechanism식에 적용하여 해석하였다. 또한 PDMS의 두께가 증가됨에 따라 선택도가 증가하는 결과를 통해서, 활성층에서의 물질전달을 Fick's law에 의하여 설명하는데 제한이 있음을 알 수 있었다.

• 한국건축시공학회지
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• 제16권6호
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• pp.545-551
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• 2016

막구조 건축물의 시공 증가에도 불구하고 국내에는 내화 및 방화기준이 마련되어있지 않고 일반 건축물의 내화기준을 적용하고 있어 막구조 건축물과 막재료의 특성을 반영하지 못하고 있다. 또한 막구조 건축물의 내화 및 방염성능을 확보하기 위해서는 막재료가 규정된 난연성능을 만족해야 한다. 따라서 본 연구에서는 건축용 막재의 고온에서의 안전성을 확보하기 위해 현무암섬유를 직포로 적용하였다. 그리고 막재의 강도특성과 방염 및 난연특성을 기존의 건축용 막재와 비교, 평가함으로써 막재료의 평가기준에 대한 참고자료로 삼고자 한다. 연구결과, 현무암섬유와 유리섬유 기반의 건축용 막재는 낮은 열방출율과 총방출열량을 나타내 화재안전성이 높은 것으로 확인되었다.

• Membrane and Water Treatment
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• 제6권2호
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• pp.141-160
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• 2015

This study aims to investigate the impacts of chemical cleaning on the performance of a reverse osmosis membrane. Chemicals used for simulating membrane cleaning include a surfactant (sodium dodecyl sulfate, SDS), a chelating agent (ethylenediaminetetraacetic acid, EDTA), and two proprietary cleaning formulations namely MC3 and MC11. The impact of sequential exposure to multiple membrane cleaning solutions was also examined. Water permeability and the rejection of boron and sodium were investigated under various water fluxes, temperatures and feedwater pH. Changes in the membrane performance were systematically explained based on the changes in the charge density, hydrophobicity and chemical structure of the membrane surface. The experimental results show that membrane cleaning can significantly alter the hydrophobicity and water permeability of the membrane; however, its impacts on the rejections of boron and sodium are marginal. Although the presence of surfactant or chelating agent may cause decreases in the rejection, solution pH is the key factor responsible for the loss of membrane separation and changes in the surface properties. The impact of solution pH on the water permeability can be reversed by applying a subsequent cleaning with the opposite pH condition. Nevertheless, the impacts of solution pH on boron and sodium rejections are irreversible in most cases.

• Membrane and Water Treatment
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• 제6권1호
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• pp.15-26
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• 2015

The compact structure and high-quality effluent of membrane bioreactors make them well-suited for decentralized greywater reclamation. However, the occurrence of membrane fouling continues to limit their effectiveness. To address this concern, a unique membrane module configuration was developed for use in a decentralized greywater treatment system. The module featured local aeration directly below a series of inclined membrane bundles, giving the overall module a twisted appearance compared to a module with vertically orientated fibres. The intent of this design was to increase the frequency and intensity of collisions between rising air bubbles and the membrane surface. Material related to the construction of custom-fit modules is rarely communicated. Therefore, detailed design and assembly procedures were provided in this paper. The twisted module was compared to two commercially available modules with diverse specifications in order to assess the relative performance and marketability of the twisted module with respect to existing products. Contaminant removal efficiencies were determined in terms of biochemical oxygen demand, chemical oxygen demand, ammonia, total nitrogen, total phosphorus, and turbidity for each module. Membrane fouling was monitored in terms of permeate flux, transmembrane pressure, and membrane resistance. Following 168 h of operation, the twisted module configuration demonstrated competitive performance, indicating good potential for further development and commercialization.

• Membrane and Water Treatment
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• 제10권6호
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• pp.461-469
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• 2019

In the present work, we present a new effective hydrophilicity modifier for polysulfone (PSf) membrane. Firstly, amphiphilic nanocellulose (ANC) with different substitution degrees (SD) was synthesized by esterification reaction with nanocellulose (NC) and dodecyl succinic anhydride (DDSA). The SD and morphology of ANC were characterized by titration method and transmission electron microscopy (TEM). Then, the polysulfone (PSf)/ANC blend membranes were prepared via an immersion phase inversion method. The influence of SD on the morphology, structure and performances of PSf/ANC blend membrane were carefully investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), mechanical property test, contact angle measuring instrument and filtration experiment. The results showed that the mechanical property, hydrophilicity and anti-fouling property of all the PSf/ANC blend membranes were higher than those of pure PSf membrane and PSf/NC membrane, and the membrane properties were increased with the increasing of SD values. As ANC-4 has the highest SD value, PSf/ANC-4 membrane exhibited the optimal membrane properties. In conclusion, the prepared ANC can be used as an additive to improve the hydrophilicity and anti-fouling properties of polysulfone (PSf) membrane.