• Proceedings of the Membrane Society of Korea Conference
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• 1991.04a
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• pp.35-37
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• 1991

무기 분말과 고분자 용액을 함께 습식방사하여 제조된 중공사를 소결하여 이방성 구조를 갖는 Alumina 와 Alumina/Silica 중공사막을 제조 하였다. 중공사 제조 용액의 조성과 소결 온도에 따른 다공성 지지체막의 기공도 및 미세구조를 Mercury Porosimeter와 Surface Analyzer(Autosorb-1)를 이용하여 살펴 보았다. 무기 분말(Alumina, Silica)이 충진된 고분자 용액의 적정한 조성에 따라 소결 후에도 이방성 구조를 유지할 수 있었고 방사 조건에 따라서도 양쪽지상구조, 한쪽지상구조, 또는 망사구조를 가지고 있으며 제조시 소결 온도에 따라 기체 투과도가 감소 하였다. 다공도는 소결 온도가 증가함에 따라 급격히 줄어들고 있으나 평균 기공의 크기는 약간 증가 하였다. 전체적으로 투과 실험 조건하에서 기체 투과가 knudsen flow 특성을 나타내었다.

• Korean Chemical Engineering Research
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• v.57 no.4
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• pp.559-564
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• 2019

Hierarchical $ZnCo_2O_4$ hollow nanofibers were prepared by electrospinning and subsequent heat-treatment process. The spinning solution containing polystyrene (PS) nanobeads was electrospun to nanofibers. During heat-treatment process, PS nanobeads in the composite were decomposed and therefore generated numerous pores uniformly in the structure, which facilitated the heat transfer and gas penetration into the structure. The resulting hierarchical $ZnCo_2O_4$ hollow nanofibers were applied as an anode material for lithium-ion batteries. The discharge capacity of the nanofibers was $815mA\;h\;g^{-1}$ ($646mA\;h\;cm^{-3}$) after the 300th cycle at a high current density of $1.0A\;g^{-1}$. However, $ZnCo_2O_4$ nanopowders showed the discharge capacity of $487mA\;h\;g^{-1}$ ($450mA\;h\;cm^{-3}$) after 300th cycle. The excellent lithium ion storage property of the hierarchical $ZnCo_2O_4$ hollow nanofibers was attributed to the synergetic effects of the hollow nanofiber structure and the $ZnCo_2O_4$ nanocrystals composing the shell. The hierarchical hollow nanofiber structure introduced in this study can be extended to various metal oxides for various applications, including energy storage.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.45-48
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• 2008

This study is for proposing the shape of hollow and evaluating the structural performance of hollow reinforced concrete (RC) half slabs. The two-phase experimental works were carried out, and styrofoam was used for reduction of dead load and vibration. From the Phase I test result, the shape and spacing of the hollow were determined to obtain the high deduction ratio of the concrete and the desirable failure mode of the hollow RC half slabs. In the Phase II test, two slab specimens were tested in flexure to evaluate the flexural capacity of the hollow RC half slabs with the proposed hollow shape. In the result of the test, all the specimens having the proposed hollow shape showed sufficient flexural capacity.

• Ceramist
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• v.12 no.4
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• pp.34-42
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• 2009

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.91-97
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• 2017

The purpose of this study is to get a more precise frequency of hollow core slabs by comparing the observed values from the actual free vibration tests and the predicted values based on the analysis model. The actual free vibration tests were carried out in the construction field using ${\Omega}$ shaped hollow core slabs. Modal analysis is conducted based on the analysis model that takes into account the differences in section properties due to void parts of slab. The differences between the predicted values based on the modal analysis with analysis model and the measured data from the actual tests range from 2~7%. This study demonstrates that the analysis model that incorporates void parts of slab could be used in evaluating serviceability of hollow core slabs with reasonable accuracies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.97-102
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• 2018

Conventional PSC I type girders were adversely affected by the self - weight of concrete, anchorage, prestressing. In order to overcome this problem, PSC girder was constructed with a hollow in the web and developed a hollow web PSC type I girder which is applicable to 50 - 70m span by multistage stressing and then actually long span hollow web PSC girder bridge was constructed. In this study, the results of Static Load Test and the Finite Element Analysis of the hollow web PSC I girder bridges were compared and analyzed, and the Load Carrying Capacity and safety of PSC girder bridges were evaluated. The Static Load Test and the numerical analysis results of this bridge showed similar tendency and the behavior of the hollow web PSC I girder was well simulated. The entire girders of the bridges had sufficient Load Carrying Capacity under the live load design condition and the bridges satisfied the safety and confirmed the appropriateness of the construction.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.819-825
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• 2018

Porous nanofibers comprising hollow ${\alpha}-Fe_2O_3$ nanospheres were prepared by applying both template method and Kirkendall diffusion effect to electrospinning process. During heat-treatment processes, the solid Fe nano-metals formed by initial heat-treatment in the carbon matrix were converted into the hollow structured ${\alpha}-Fe_2O_3$ nanospheres. In particular, PS nanobeads added in the spinning solution were decomposed and formed numerous channels in the composite, which served as a good pathway for Kirkendall diffusion gas. The resulting porous nanofibers comprising hollow ${\alpha}-Fe_2O_3$ nanospheres were applied as an anode material for lithium-ion batteries. The discharge capacities of the nanofibers for the 30th cycle at a high current density of $1.0A\;g^{-1}$ was $776mA\;h\;g^{-1}$. The good lithium ion storage property was attributed to the synergetic effects of the hollow ${\alpha}-Fe_2O_3$ nanospheres and the interstitial nanovoids between the nanospheres. The synthetic method proposed in this study could be applied to the preparation of porous nanofibers comprising hollow nanospheres with various composition for various applications, including energy storage.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.04a
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• pp.36-37
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• 1993

상전이 공정에 의해 제조된 기체분리용 중공사막은 1차적으로 방사원액의 조성과 내.외부응고제의 조성, 중공사 방사조건 그리고 후처리 과정에 의해서 전체적인 구조가 결정되어진다. 특히 기체 분리에 이용되는 Nonprous Membrane의 경우 Dense Skin의 Thickness와 Pinhole의 유무에 따라 투과성과 선택성에 커다란 영향을 미친다. 따라서 최근에는 Dense Skin의 초박막화와 Pinhole이 없는 비대칭막 제조등 폭넓은 연구가 이루어지고 있다. 본 연구에서는 CO$_2$ Gas 분리용 Polyetherimide 중공사막을 제조하여, 중공사막 제조조건과 후처리 조건에 따른 $CO_2/N_2$ Gas의 분리계수를 측정하였다.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.75-76
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• 1996

다공성 고분자 분리막을 제조하는 방법으로 기존의 용매교환법을 대신하여 내용매성, 내약품성 및 내열성이 매우 뛰어난 고분자를 소재로하여 다공성 고분자막을 만드는 열유도 상분리법(Thermally Induced Phase Separation, TIPS)이 개발되었다. TIPS공정에서는 주로 고분자/희석제 system의 열역학적인 불안정성에 의하여 polymer-rich phase와 polymer-lean phase로 상이 분리되는 liquid-liquid phase separation과 결정성 고분자의 결정화에 의한 solid-liquid phase separation을 주로 상분리 mechanism으로 사용하고 있다. 따라서 위에 언급된 TIPS 이론에 근거한 melt spinning 공정에 의하여 PP 중공사막을 제조하였는데 wet spinning 공정에 의한 용매 교환법에 비해 비교적 공정이 단순하고 다공도를 조건하기가 용이하며 구조 및 성능면에서도 높은 재현성을 가지고 있다. 또한 우수한 소재임에도 불구하고 절절한 용매의 부재로 용매교환법에서 사용할 수 없었던 폴리올레핀계, 나일론계, 방향족출합계 고분자를 사용할 수 있게 되어 소재의 폭이 넓어졌다는데에 가장 큰 장점이 있다. 본 연구에서는 PP중공사막을 제조하기 위하여 먼저 용융 방사장치를 제작하였고 melt spinning 공정에 의해 막을 제조하는데 적합한 방사조건들을 확립한 후 결정된 방사조건에 의해 얻어진 PP 중공사막의 구조 및 성능에 영향을 미치는 인자들에 관하여 조사하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.182-189
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• 2021

VPS(Void Plywood Slab System, VPS) has optimized the shape of the hollow material. In addition, it has a function to prevent the floating of the hollow material and the separation due to the working load. In this study, the punching shear capacity of flat plate was performed using Void Plywood Slab System with form work panel proposed in the previous study. As a result of the test, the strength of the VSPS specimen in which the hollow material was placed beyond 2.0 times the column width from the loading point was reduced by 9.4% compared to the reference specimen. However, the strength value was about 1.57 times higher than the design value suggested by KBC 2016. It was found that there was no change in stiffness compared to the reference specimen until shear failure occurred in the VSPS specimen in which the hollow material was placed. It can be seen that this experiment is being destroyed by shear as the flexural reinforcing bars are sufficiently reinforced.