• Membrane and Water Treatment
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• 제6권5호
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• pp.351-363
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• 2015

To increase the surface hydrophilicity of PVDF membranes, in this paper, an electric enhancing method was adopted to treat PVDF nascent membranes during the phase inversion process. It was found that when PEG 600 was taken as the additive, the surface water contact angle of the PVDF membrane treated under 2 kV electric field was decreased from $84.0^{\circ}$ to $65.7^{\circ}$. The reason for the surface elements change of the PVDF membranes prepared under the electric field was analyzed in detail with the dielectric parameters of the polymer dope solutions. Results from BSA adsorption experiment showed that the antifouling ability of the external electric field-treated membranes was distinctly enhanced when compared with that of the untreated membranes. The amount of BSA adsorbed by the treated membranes was lower by 38-43%. Compared with the common chemical reaction methods to synthesize hydrophilic additives or membrane materials, the electric field-assisted processing method did not involve any additional chemical synthesis process and it was capable of realizing better hydrophilicity.

• 한국전기전자재료학회논문지
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• 제27권1호
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• pp.56-60
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• 2014

The polyimide composite membranes were prepared with polyimide composite solutions including graphenes by using the phase inversion method. The morphologies of these membranes were significantly changed according to the graphene loadings in composite solutions and the solvent systems of the composite solutions. The finger-like macro-voids were formed in the hollow fiber membranes which were prepared in the NMP solvent system with a small amount of ethanol. As increasing the content of the viscous alcohols such as glycerol or 1,3-propanediol in the composite solution, however, the morphologies of the hollow fiber membranes were changed to sponge-like types. In case of flat membranes, the increase of graphene content in polyimide composites causes that their membranes change from the finger-like macro-porous to sponge-like morphologies.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.356-361
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• 2003

The objective of this study is a qualitative comparison between line-integrated OH chemiluminescence ($OH{\ast}$) image and its Abel inversion image at different phase of the oscillating pressure field. PIV(Particle Image Velocimetry) measurements were conducted under non-reacting conditions to see the global flow structure. Also NOx emission was measured to investigate the effect of fuel-air premixing on combustion instability and emission characteristics. Experiments were carried out in an atmospheric pressure, laboratory-scale dump combustor operating on natural gas. Combustion instabilities in present study exhibited a longitudinal mode with a dominant frequency of ${\sim}341.8$ Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instability occurred. Results gave an insight about the location where the strong coherence of pressure and heat release existed. Also an additional information on active control to suppress the combustion instabilities was obtained. For lean premixed combustion, strong correlation between $OH{\ast}$ and NOx emissions was expected largely due to the exponential dependence of thermal NOx mechanism on flame temperature.

• 한국운동역학회지
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• 제22권1호
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• pp.35-42
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• 2012

The aim of the present study was to investigate effect of running speed conditions on the kinematic pattern of the metatarsus, mid-foot, calcaneus. Twenty-two healthy young adults were made to run on treadmill at three different running speeds(normal speed, 9.2; slow speed, 7.4; fast speed, 11.1km/hr.) and the trajectories of the 10 reflective markers for each subject were recorded by an eight-camera motion capture system at 200 Hz. Three-dimensional angles for the foot segment in the support phase during running were calculated according to Euler's technique. Results showed that running speed did not affect the peak of the dorsi/plantar flexion, inversion/eversion, and adduction/abduction or their range of motion for each foot segment. However, when the running speed was fast, significant differences were found in the peak of the plantar flexion, eversion, and adduction and ROM(range of motion) of the dorsi/plantar flexion, inversion/eversion, and adduction/abduction between the foot segments, metatarsus, mid-foot, and calcaneus. It was proposed that the foot segment should be analyzed from a multi-segment system point of view on the basis of anatomical reference during locomotion.

• 멤브레인
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• 제6권3호
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• pp.182-187
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• 1996

우수한 분획특성을 가지는 친수성 고분자인 poly(acrylonitrile) [PAN]을 막소재로 하여 상전환법(phase inversion method)으로 복합막의 지지층으로 사용될 지지막을 제조하였으며, 한외여과 실험을 통하여 지지막의 특성인 순수 투과도와 분획분자량을 측정하였다. 이 지지막 표면에 poly(acrylic acid) [PAA]를 dip-coating 시켜 열처리한 복합막을 제막하고 에탄올 수용액의 투과증발 분리특성을 고찰하였다. PAN 지지막의 UF 특성은 순수의 투과유속이 $0.17~31\textrm{mm}^3/m^{2} \cdot s \cdot Pa$, 분획분자량이 42,000~150,000의 막을 얻었다. 복합막의 투과유속과 분리계수는 지지막의 기공구조 변화에 상당한 영향을 받고 있음을 알 수 있으며, 지지층의 분획분자량의 증가에 따라 투과유속은 감소하였고 분리계수는 공급원액의 농도에 따라 약간의 변화를 보였다.

• Elastomers and Composites
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• 제44권2호
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• pp.143-149
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• 2009

본 연구에서는 아스팔트가 가지는 단점을 보완하고자 아스팔트를 비이온 계면활성제(Span 80, Span 60, Tween 80, 및 Tween 60), 음이온 계면활성제(SLS), 및 양이온 계면활성제(Imidazole)를 변량 배합하여 반전유화법으로 아스팔트 에멀젼을 제조하였다. 유화아스팔트의 안정성을 규명하고자 입자크기, 점도, 제타전위, 및 내수성을 고찰하였다. 비이온 계면활성제와 음이온 계면활성제를 혼합 사용할 경우 유화아스팔트의 안정성은 우수하였으며 계면활성제의 양이 증가함에 따라 입자크기는 감소하였고, 반면에 점도와 제타전위 및 내수성은 증가하였다.

• 멤브레인
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• 제9권4호
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• pp.215-220
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• 1999

고농도의 초산수용액(80 wt% 이상)을 분리 농축하기 위하여 내용매성이 우수하며 고온에서의 내열성을 가지는 폴리이미드 비대칭막을 만들어 막의 특성을 검토하고 물-초산 계의 투과증발 분리성능을 고찰하였다. 제막은 폴리아믹산의 상전이용액으로 톨루엔을 사용한 것이 가장 좋은 상태의 막을 얻을수 있었다. 열처리에 의한 imide화는 373, 473573 K에서 각각 1시간씩 연속적으로 처리하는 것이 가장 효과적이었다 막은 물-초산 계의 투과증발 분리에 의한 열내구성 및 화학적 안정성이 우수하였다 폴리이미드막의 투과증발 분리특성은 80 wt% 초산수용액 계에서 분리계수는 180 투과유속은 0.5kg/$m^2$hr을 얻을 수 있었다.

• 한국통신학회논문지
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• 제31권11A호
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• pp.1044-1052
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• 2006

In this paper the optimum position of optical phase conjugator (OPC) and the optimal dispersion coefficients of filler sections in WDM system with the conventional mid-span spectral inversion (MSSI) are numerically induced and then applied into $16{\times}40$ Gbps WDM systems with 1,000km non zero - dispersion shifted fiber(NZ-DSF) in order to efficiently compensate for the distorted overall channels. It is confirmed that the compensation extents of overall WDM channels are more improved by applying the induced optimal parameters into WDM system than those in WDM system with the conventional MSSI. So it is expected to alternate with the forming method of the symmetrical distributions of power and local dispersion by applying these optimal parameters into the real WDM system, which generate a serious problem of applying the OPC into multi-channels WDM system if it is not formed. It is also confirmed that two optimal parameters depend on each other, but less related with the finding procedure. And, it will be possible to realize the flexible system design by applying the methods proposed in this paper into the real WDM system with OPC.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.17-22
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• 2007

In this paper, the optimal value of optical phase conjugator (OPC) position and the optimal values of dispersion coefficients of fiber sections for the best compensation of the distorted WDM signals with frequency chirp of -1 are induced to alternate with the symmetrical distributions of power and local dispersion with respect to OPC, which is difficult to form in real optical link due to fiber attenuation in mid-span spectral inversion (MSSI) technique. It is confirmed that the Q-factors of total channels of -18.5 dBm launching light power exceed 16.9 dB, which value corresponds to 10-12 BER, by applying the induced optimal parameter values into 16 channels ${\times}$ 40 Gbps WDM system, on the other hand the Q-factors of only 9 channels exceed that value in WDM system with the conventional MSSI technique. Thus, it is expected to expand the availability of OPC in WDM system through the using of the optimal parameter values that are induced by the proposed method in this paper, without the symmetrical distributions of power and local dispersion.

• Membrane and Water Treatment
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• 제13권3호
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• pp.139-145
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• 2022

Development in advanced separation processes leads to the significant advancement in polymeric membrane preparation methodology. Therefore, present research investigated the preparation and characterization of cellulose acetate membrane by phase inversion separation method to determine optimized operating parameters. Prepared CA membrane's performance was been analyzed in terms of % rejection and flux. Investigation was conducted to study effect of different parameters such as polymer concentration, evaporation rate, thickness of film, coagulation bath properties, temperature of polymer solution and of the coagulation bath etc. CA membrane was fabricated by taking polymer concentration 10wt% and 11wt% with zero second evaporation time and varying film thickness over non-woven polyester fabric. Effect of coagulation bath temperature (CBT) and casting solution temperature were also been studied. The experimental results from SEM showed that the surface morphology had been changed with polymer r concentration, coagulation bath and casting solution temperature, etc. Lower polymer concentration leads to lower precipitation time giving porous membrane. The prepared membrane was tested for advanced waste water treatment of relevant effluent stream in pilot plant to study flux and rejection behavior of the membrane.