• Structural Engineering and Mechanics
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• 제91권1호
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• 대한기계학회논문집B
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• 제37권5호
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• pp.513-522
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• 2013

본 연구에서는 다중효용 증발식 담수기에 쓰이는 강하막식 증발기의 수치해석을 수행하였다. 증발기에 사용되는 다관군을 다공성 매질로 묘사하고 공간평균 개념을 적용하였다. 증발기 내부의 유동계산 및 열 전달로 인한 상변화를 계산하기 위해서 FLUENT 와 UDF 가 사용되었다. 작동조건에 대한 증발기의 성능변화를 살펴보기 위해 수평관 내 증기 질량 유속을 $0.5{\sim}2.5kg/m^2s$, 관내입구 측 비 응축성 기체의 질량분율을 0~1%, 그리고 수평관 외 뿌려지는 강하막의 액막 레이놀즈 수를 100~1000 으로 바꾸어가며 해석을 수행하였다. 관내 증기유속 및 관외 강하막 레이놀즈 수가 증가할수록 증발량은 증가하였으며, 관내 비 응축성 기체의 질량분율이 1%증가함에 따라 증발량이 0.87%줄어들었다.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.229-237
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• 2018

Medical silicone tubes are generally used as implants for the treatment of nasolacrimal duct stenosis. However, side effects such as allergic reactions and bacterial infections have been reported following the silicone tube insertion, which cause surgical failure. These drawbacks can be overcome by modifying the silicone tube surface using a functional coating. Here, we report a biocompatible and superhydrophilic surface coating based on a polysaccharide multilayer nanofilm, which can load and release antibacterial and anti-inflammatory agents. The nanofilm is composed of carboxymethylcellulose (CMC) and chitosan (CHI), and fabricated by layer-by-layer (LbL) assembly. The LbL-assembled CMC/CHI multilayer films exhibited superhydrophilic properties, owing to the rough and porous structure obtained by a crosslinking process. The surface coated with the superhydrophilic CMC/CHI multilayer film initially exhibited antibacterial activity by preventing the adhesion of bacteria, followed by further enhanced antibacterial effects upon releasing the loaded antibacterial agent. In addition, inflammatory cytokine assays demonstrated the ability of the coating to deliver anti-inflammatory agents. The versatile nanocoating endows the surface with anti-adhesion and drug-delivery capabilities, with potential applications in the biomedical field. Therefore, we attempted to coat the nanofilm on the surface of an ophthalmic silicone tube to produce a multifunctional tube suitable for patient-specific treatment.

• 한국환경과학회지
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• 제9권4호
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• pp.311-318
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• 2000

To improve $CO_2$pemselectivity, a modified silica membrane was prepared by chemical vapor deposition with tetraethoxysilane(TEOS)-ethanol-water, and TEOS-ethanol-water-HCI solution at 300-$600^{\circ}C$. The silica was effectively deposited in the mesopores of a ${\gamma}$-alumina film coated on a porous $\alpha$-alumina tube by evacuating the reactants through the porous wall. In this membrane, $CO_2$interacts, to some extent, with the pore wall, and $CO_2$/$N_2$selectivity then exceeds the value of the Knudsen diffusion mechanism, while the membrane derived from TEOS alone has no $CO_2$selectivity. The silica membrane prepared from TEOS-ethanol-water-HCI solution showed that $CO_2$permeance was $2.5$\times$10^{-7}mol/s^{-1}.m^{-2}.Pa^{-1} at 30{\circ}C$ and $CO_2$/$N_2$selectivity was approximately 3. The $CO_2$permeance and selectivity was improved by enlarging the surface diffusion with modification of chemical affinity of the silica pores.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.115.1-115.1
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• 2016

Electrochemical anodization has been interested due to its useful way for the nano-scale architecture of metal oxides obtained from a metal substrate. By using this method, it is easy to control the morphology of the oxide materials by controlling electrochemical conditions. Among oxide materials obtained from the transition metals such as Ti, V, W, etc., in this paper, the morphological study of anodized $TiO_2$ was employed at various voltage conditions in fluoric based electrolyte, and the effects of applied voltage (sweep rate and retention time) on the tube morphologies were investigated. Furthermore, by using anodization of tungsten substrate (W), we fabricated the porous structure of $WO_3$ and provided merits of tailored structure for the hybridization of inorganic and organic materials as electrochromic (EC) applications. The hybrid porous $WO_3$ shows multi-chromic properties during the EC reactions at specific voltage conditions. From these results, the anodization process with tailoring nano-structure is one of the promising methods for EC applications.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.456-459
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• 2008

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package cheesesstacked on a spindle made of a perforated tube. Spindles up to now, have been designed without considering the characteristics of dyeing liquid, focusing only on the geometric configuration which cause many problems such as lack of level dyeing. To improve the level dyeing and find the appropriate spindle configuration for the most effective dyeing process, this study examines the spindle flow-field in detail, using a computational method. Flow characteristics inside the spindle have been investigated with varying in porosity, porous diameter and the velocity of the flow. The results show that the total pressure of the flow through the spindle is used to overcome body force. The characteristics of the flow from the porous spindle could also be observed. Based on the results from this study, an effective spindle configuration for level-dyeing has been proposed.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2577-2583
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• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• 한국연소학회지
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• 제18권3호
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• pp.24-30
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• 2013

Flame stabilization characteristics of premixed flames in an annular coaxial 5-tubes burner (AC5TB) were investigated experimentally. The AC5TB was made of five quartz tubes, and the flame stabilization conditions in that burner were investigated with the variation of equivalence ratio and the flow velocities. Flame behaviors inside of narrow annular tubes could be observed directly. Overall flame stabilization conditions were similar to that of the previous study, while the flame behaviors and structures were different mainly due to the controlled uniform distribution of the velocities in channels. Flame flashback conditions were thought to be governed by the competition between heat release rate, heat loss and heat recirculation in each channel. Stationary flames at a fixed location were compared in its velocity distribution and burned gas temperature across the channel. This AC5TB can be a basic configuration for the development of flame stabilization model of porous media combustors, and it will help understand about the real behavior of flames in meso-scale combustion spaces.

• 대한전자공학회논문지
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• 제23권5호
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• pp.699-705
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• 1986

Sb2S3 thin films were fabricated by vacuum evaporation of compound Sb2S3 at a pressure of 10**-5 torr. and in argon ambient. Then, their electrical and photoconductive properties were investigated. The Sb2S3 glass-layer showed maximum photosensitivity at the deposition rate of 250\ulcornersec, and Sb2S3 porous layer had mininum dielectric constant of 1.5 at the deposition rate of 0.3 um/sec and argon partial pressure of 0.2torr. Sb2S3 multi-layers were prepared at the different thickness ratio (B/A) to find the proper structural property suited for camera pick-up tube. Here, A is the sum of the thickness of Sb2S3 porous layer and Sb2S3 fine grain layer, and B is the thickness of Sb2S3 fine grain layer. As a result, photosensitivity had a peak value at the thickness ratio (B/A) of 60%.

• 대한기계학회논문집B
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• 제36권6호
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• pp.619-624
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• 2012

본 논문에서는 원통형 다공성 유리막을 이용한 전기삼투 펌프의 실험적 연구를 수행하였고, 장시간 작동을 평가하였다. 전기삼투 펌프의 성능은 탈이온수와 1 mM 붕산염 완충액을 이용하여 최대유량, 최대전류, 그리고 최대압력으로 표현하였다. 최대유량, 최대전류, 그리고 최대압력은 모두 이론에서 예측하는 것과 같이 전압이 증가할 때 선형적으로 증가하였다. 최대유량을 유체의 펌핑면적과 적용 전압으로 나눈 표준화 유량을 사용하여 원통형 다공성 유리막을 이용한 전기삼투 펌프와 평면형 다공성 유리막을 이용한 전기삼투 펌프의 성능을 비교하였다. 표준화 유량은 원통형 다공성 유리막을 이용할 때 평면형 다공성 유리막보다 대략 1.5 배 높은 값을 가졌고, 이는 원통형 다공성 유리막과 평면형 다공성 유리막의 기하학적 부분의 차이에 의한 것으로 판단되었다. 표준화 유량 값을 이용하여 동일한 전기삼투 펌프 부피에서 두 다공성 막을 비교하면, 원통형 전기삼투 펌프는 평면형 전기삼투 펌프에 비해 최대 원주율만큼의 펌핑면적을 증가할 수 있으므로 5 배 높은 유량을 얻었다. 원통형 전기삼투 펌프의 내부 전극에서 전기분해에 의해 발생하는 가스들은 나피온 튜브를 통하여 효과적으로 배출되었고, 이로 인해 3 시간 이상의 작동에서 성능의 감소는 발생되지 않았다.