• 멤브레인
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• 제26권3호
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• pp.212-219
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• 2016

알루미나 분말이 분산된 고분자용액을 비용매 유도 상전이법으로 방사 및 소결하여 알루미나 중공사막을 제조하였다. 용매-비용매의 상호작용 속도에 따른 중공사막 기공 구조 형성을 확인하고, 특성을 분석하기 위해 dimethylsulfoxide (DMSO), dimethylacetamide (DMAc), triethylphosphite (TEP) 용매를 사용하여 방사액을 제조하였으며, 고분자 바인더로는 polyethersulfone (PESf), 첨가제로는 polyvinylpyrrolidone (PVP)를 사용하였다. 알루미나 중공사막의 기공 구조 변화를 확인하기 위해 SEM으로 중공사막 단면을 분석하였다. DMSO, DMAc 용매를 사용할 경우 지상 구조(finger-like structure)와 망상 구조(sponge-like structure)가 복합된 기공 구조가 나타났으며, TEP 용매를 사용할 경우 전체적으로 망상 구조를 가졌다. 기공 구조에 따른 중공사막의 특성을 확인하기 위해 기체투과도, 기공도 및 기계적 강도를 측정하였다. 망상 구조를 갖는 중공사막은 높은 기체 투과특성을 보였으며 지상 구조가 증가할수록 기체투과도가 감소하였다. 반대로 기계적 강도는 지상 구조가 발달할수록 증가하였다.

• 한국세라믹학회지
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• 제34권11호
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• pp.1139-1150
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• 1997

A model for predicting the relative density and the compressive strength of open-cell ceramics with three-dimensional network structure was proposed through the interpretation of their macrostructure and fracture mechanics. The equation predicting the relative density was derived under the assumption that the open-cell structure was a periodic array of the tetrakaidecahedron unit cell consisting of cylindrical struts containing the internal hollow with the shape of a triangular prism. The model for compressive strength of open-cell ceramics with the hollow strut was also developed by modifying conventional model which based on fracture behavior of them subjected to the compressive stress. Both the relative density and the compressive strength were expressed in terms of the ratio of the strut diameter to the length together with the ratio of the hollow size to the strut diameter. The proposed model for the relative density and the compressive strength of the alumina-zirconia composite with open-cell structure were accorded well with the experimental values, whereas Gibson-Ashby and Zhang's model did not show such a good agreement.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.362-367
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• 2008

Recently, the use of biaxial hollow slab is increased to reduce noise and vibration of the floor slab. Therefore, an efficient method for the vibration analysis of biaxial hollow slab is required to describe dynamic behavior of biaxial hollow slab. A finite element analysis is one of the method to analyze the biaxial hollow slab. It is necessary to use a refined finite element model for an accurate analysis of a floor slab with an effects of the hollow shape. But it would take a significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. Thus the proposed method uses equivalent plate model in this study. Dynamic analyses of an example structure subjected to walking loads were performed to verify the efficiency and accuracy of the proposed method.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.33.1-33.1
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• 2009

To date, nanostructured tungsten oxides with a variety of stoichiometries, such as WO3, WO2.9, W18O49, and WO2, have been prepared, because they are promising candidates for applications such as gas sensors, photocatalysts, electrochromic devices, and field emission devices. Among them, W18O49 and WO2 have been widely studied due to their outstanding chemical sensing, catalytic, and electron emissive properties. Here we report, for the first time, a one-pot solution-phase route to synthesizing a novel composite hierarchical hollow structure without adding catalysts, surfactants, or templates. The products, consisting of a WO2 hollow core sphere surrounded by a W18O49 nanorod shell (yielding a sea urchin-like structure), were generated as discrete structures via Ostwald ripening. To our knowledge, this type of composite hierarchical core/shell structure has not been reported previously. The morphological evolution and the detailed growth mechanism were carefully studied. We also demonstrate that the size of the hollow urchins is readily tunable by controlling the reactant concentrations.Interestingly, although bulk tungsten oxides are weakly paramagnetic or diamagnetic, the as-prepared products show unusual ferromagnetic behavior atroom temperature. The urchin structures also show a very high Brunauer-Emmet-Teller (BET) surface area, suggesting that they may potentially be applied to chemical sensor or effective catalyst technologies.

• 한국세라믹학회지
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• 제54권5호
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• pp.429-437
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• 2017

Micro hollow plate type silica with low refraction properties was synthesized and its hollow structure was applied as an optical structure to develop a light diffusion material that simultaneously satisfies the requirements of good light diffusibility, high transmissibility, and high luminance. The developed light diffusion material was applied to a light diffusion film and the film's optical properties were assessed. Hollow silica was synthesized by precipitation method using $Mg(OH)_2$ core particles, sodium silicate, and ammonium sulfate as the silica precursors. The concentration of the silica precursor was adjusted to control hollow silica shell thickness. The total light transmittance of the light diffusion film composed of the hollow silica was 94.55%, which was 4.57% higher than that of the PC film; new film's haze was 71.20%, which was 70.9% higher. Furthermore, the luminance increased by 5.34% compared to that of the light source. The reason for the results is not only that the micro plate type hollow silica, which has a low refractive property, played a role in reducing the difference in refractive index between the medium boundaries, but also that there was a light-concentrating effect due to the changing of light paths to the front direction inside the hollow structure. Optical simulation verified the enhanced optical properties when hollow silica was applied to the light diffusion film.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.425-430
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• 1996

The purpose of this study is to investigate the behavior of the bearing precast concrete (pc) wall structure with hollow core based on experimental tests. In order to evaluate the cyclic performance of the pc walls. Too one story pc walls and ond one reinforced concrete wall are made. The experimental results of pc walls were compared with those values of reinforced concrete (rc) wall. The structural behaviors of pc wall structure with hollow core are similar to those of reinforced concrete bearing wall structure. This study shows that the pc wall with hollow core could be treated as rc wall when designs the pc wall structure against lateral loads

• 한국막학회:학술대회논문집
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• 한국막학회 1995년도 추계 총회 및 학술발표회
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• pp.5-9
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• 1995

In the dry-jet-wet-spinning process of a hollow fiber membrane, the polymer solution is pumped into a coaxial tube, jet spinneret. The threadline emerging from the spinneret is stabilized by an internal coagulating medium(liquid or gas) as it emerges from the jet orifice. The nascent hollow thread is further stabilized in a quench bath as shown in Fig. 1. In this scheme, three mechanism of formatiota(temperature gradient, solvent evaporation, and solvent-nonsotvent exchange) can be combined. The changes which promote stabilization often play a dominant role in determining the ultimate fiber wall structure as well. Hence, in pratice, hollow fiber stabilization and development of membrane structure are commonly inseparable. However, fiber dimension(the inside diameter and wall thickness of the hollow fiber) is mainly a rheological problem and is determined by dope pumping rate, spinneret diatance from the coagulation bath, inner coagulant flow rate, and fiber draw-rate. Besides rheological phenomena play a prominent part in the final properties of the hollow fiber.

• 대한토목학회논문집
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• 제32권3C호
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• pp.85-94
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• 2012

본 논문은 액상화 지반에서의 지반-지하 중공구조물 상호작용에 따른 구조물의 rocking현상을 조사하기 위해서 수행한 원심모형실험에 관하여 서술하고 있다. 지진이 발생하였을 때 지반이 강한 진동에 노출되면 상대밀도가 낮은 느슨한 모래지반에서는 액상화가 발생하며, 액상화된 지반보다 작은 단위중량을 가진 지하 중공구조물은 부상한다. 지하 중공구조물이 부상하는 동안에 구조물의 동적 거동과 구조물의 부상량에 대한 원지반의 영향을 평가하기 위하여 원지반의 상대밀도를 다르게 모델지반을 제작하였고, 아크릴 박스를 이용하여 트랜치를 제작하여 모형실험을 수행하였다. 실험결과, 액상화된 원지반의 측방유동 및 주변지반의 전단변형에 의해 야기되는 지하 중공구조물의 rocking현상이 지하 중공구조물의 부상량의 규모에 크게 기여하는 것으로 나타났다.

• 패션비즈니스
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• 제8권6호
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• pp.68-77
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• 2004

Hollow filament yarns provide better warmth to the touch, lighter in weight, increased opacity, and subtle luster compared to the regular synthetic filament yarns. However, luster properties of textile fibers or fabrics are often difficult to characterize, partly due to the fineness of the surface texture, the anisotropic nature of the weave structure, the complexity of the fiber array comprising a yarn, and the fiber structure itself. In this study, the fabric surface luster image was analyzed using image analysis methods after image acquisition. The hollow filament fiber was modeled using a three-dimensional modeling software. It was then ray-traced for comparing the virtual luster images of the hollow fiber and the regular fiber models based on shading models including photon mapping. The luster object size of the actual hollow filament fabric was smaller than that of the regular filament fabric. The shape of the luster object of the hollow filament fabric was dual peak type while that of the regular filament was single.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3274-3280
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• 2011

Monodispersed porous NiO and $Co_3O_4$ microcapsules with a hollow core were synthesized using SBA-16 silica sol and PS as a hard template. The porous hollow microcapsules were characterized by XRD, TEM and $N_2$ adsorption/desorption analysis. After $H_2$ reduction of metal oxide microspheres, they were conducted as an active catalyst in the reduction of chiral butylronitrile and cyanobenzene. The mesoporous metals having a hollow structure showed a higher activity than a nonporous metal powder and an impregnated metal on the carbon support.