• Membrane Journal
• /
• v.6 no.3
• /
• pp.182-187
• /
• 1996

Hydrophilic poly(acrylonitrile) [PAN] membrane with good molecular weight cut-off characteristics were prepared by using the phase inversion method. Permeability and molecular weight cut-off of the membranes were measured through the ultrafiltration test. On the surface of the PAN support membranes, poly(acrylic acid) [PAA] was deposited by dip-coating. The water permeability of the PAN support membrane had $0.17~31\textrm{mm}^3/m^{2} \cdot s \cdot Pa$, the molecular weight cut-off 42, 000~150, 000. The transport characteristics of the prepared composite membranes were significantly affected by the variation of the support membrane mophology. The permeability of the composite membrane was decreased with increasing molecular weight cut-off of the support membrane, and the separation factor was slightly changed depending on the feed concentration.

• Elastomers and Composites
• /
• v.44 no.2
• /
• pp.143-149
• /
• 2009

In this study, asphalt emulsion was manufactured by phase inversion emulsification method with nonionic surfactants(Span 80, Span 60, Tween 80, and Tween 60), anionic surfactant(SLS) and cationic surfactant(Imidazole) in different feeding ratio to make up for the week points of asphalt. Its stabilization was carefully investigated with respect to droplet size, viscosity, zeta potential, and water-proofing property. When the surfactants mixed with nonionic and anionic surfactant were used into the asphalt, a stabilization of the asphalt emulsion was good. As the amount of the mixed surfactant was increased, the droplet size of asphalt emulsion were decreased, while the viscosity and zeta potential were increased. When the surfactants mixed with nonionic and anionic surfactant were used into the asphalt, a stabilization of asphalt emulsion was good.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.1
• /
• pp.69-79
• /
• 2008

Prediction of ground condition ahead of tunnel face might be the most important factor to prevent collapse during tunnel excavation. In this study, a non-destructive method to evaluate the phase velocity in model rock mass using wavelet transform of surface wave was proposed aiming at ground condition assessment ahead of tunnel face. Model tests using gypsum as a rocklike material composed of two layers were performed. A Piezoelectric actuator with frequencies ranging from 150 Hz to 5 kHz was selected as a harmonic source. The acceleration history was measured with two accelerometers. Wavelet transform analysis was used to obtain the dispersion curves from the measured data. The experimental results showed that the near-field effects can be neglected if the distance between two receivers is chosen to be three times the wavelength. A simple inversion method using weighted factor based on the normal distribution was proposed. The inversion results showed that the predicted phase velocity agreed reasonably well with the measured one when the wavelength influence factor was 0.2. The depth of propagation of surface wave was from 0.42 to 0.63 times the wavelength. The range of wavelength varying with phase velocity in dispersion curve matched well with that estimated by inversion technique.

• Transactions on Control, Automation and Systems Engineering
• /
• v.3 no.1
• /
• pp.21-26
• /
• 2001

In this study, we propose a two degree of freedom robust output tracking control method for a class of nonlinear system. We consider hyperbolically nonminimum phase single-input single-output uncertain nonlinear systems. We also consider the case that the nominal input-state equation is differentially flat. Nominal stable state trajectory is obtained in the flat output space via the flat output. Nominal feedforward control input is also computed from the nominal state trajectory. Due to the nature of the method, the generated flat output trajectory and control input are noncausal. Robust feedback control is designed to stabilize the systems around the nominal trajectory. A numerical example is given is given to demonstrate that robust tracking is achieved.

• Membrane Journal
• /
• v.26 no.6
• /
• pp.463-469
• /
• 2016

In this research, a new expectation in enhancing the PES (polyethersulfone) polymer phase inversion membrane performances with nanoparticles is proposed by using ZnO. This paper investigated the synthesis of PES phase inversion membranes including ZnO nanoparticles and evaluates the performance of these mixed matrix membranes. The PES-ZnO mixed matrix membranes were fabricated by phase inversion method using the PES-ZnO-NMP(N-methyl-1-pyrrolidone) casting solutions with low ZnO nanoparticles content of 0.375 wt%. The influence of ZnO nanoparticles on the characteristics of PES-ZnO mixed matrix membranes was investigated with scanning electron microscope observations of membrane cross-sections, contact angle measurements, tensile strength measurements, pure water flux measurements and ultrafiltration experiments of BSA solution. Those results showed that the performance advancements in comparison with the pure PES membrane without ZnO in terms of increasing hydrophilicity as well as reducing membrane fouling by adding ZnO nanoparticles even in low concentration.

• Membrane Journal
• /
• v.34 no.1
• /
• pp.20-29
• /
• 2024

Membranes are increasingly used in a variety of applications including desalination, gas separation, disposable filters, and healthcare products. Recently, sustainable and green membrane fabrication technology is recognized as one of the decisive initiatives to reach the target of pollution control. Especially, the fabrication of bio-based membranes using such as poly lactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS) has attracted considerable attention. The phase inversion method is one of the versatile approaches for preparing PLA membranes. This article reviews the recent advances in PLA membrane preparation via the phase inversion method. Furthermore, it provides a perspective on the potential outlook for future advances. Overall, this review has demonstrated has been conducted in the area of bio-based PLA membranes.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.5
• /
• pp.1192-1202
• /
• 1994

Fatigue behavior and life prediction were presented for thermal-mechanical and isothermal low cycle fatigue of 12Cr forged steel used for high temperature applications. In-phase and out-of-phase thermal-mechanical fatigue test at 350 to 600.deg. C and isothermal low cycle fatigue test at 600.deg. C were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Cyclic softening behavior was observed regardless of thermal-mechanical and isothermal fatigue tests. The phase difference between temperature and strain in thermal-mechanical fatigue resulted in significantly shorter fatigue life for out-of-phase than for in-phase. The difference in fatigue lives was dependent upon the magnitudes of inelastic strain ranges and mean stresses. Increase in inelastic strain range showed a tendency of intergranular cracking and decrease in fatigue life, especially for out-of-phase thermal-mechanical fatigue. Thermal-mechanical fatigue life prediction was made by partitioning the strain ranges of the hysteresis loops and the results of isothermal low cycle fatigue tests which were performed under the combination of slow and fast strain rates. Predicted fatigue lives for out-of-phase using the strain range partitioning method showed an excellent agreement with the actual out-of-phase thermal-mechanical fatigue lives within a factor of 1.5. Conventional strain range partitioning method exhibited a poor accuracy in the prediction of in-phase thermal-mechanical fatigue lives, which was quite improved conservatively by a proposed strain range partitioning method.

• Journal of the Korean Electrochemical Society
• /
• v.9 no.1
• /
• pp.29-33
• /
• 2006

A new porous separator based on poly(vinyl chloride) (PVC)/poly(vinylidene fluoride-co-hexafluoro-propylene) (P(VdF-co-HFP)/poly(methyl methacrylate) (PMMA) was prepared by a phase inversion method. To enhance mechanical property, the membrane was stretched uniaxially at high temperature. Tensile strength and ionic conductivity were measured for various draw ratios. The tensile strength and ionic conductivity were increased with increasing draw ratio. The tensile strength of the separator reached 52MPa after stretching to draw ratio of 5, and the ionic conductivity of the separator was increased from $1.9Xs10^{-4}S/cm\;to\;4.6X10^{-4}S/cm\;at\;25^{\circ}C$. The stretched separator immersed in liquid electrolyte was electrochemically stable up to 4.7 V. The cell based on the stretched separator was maintained at about 99% of the initial discharge capacity after 10th cycle operation at 0.2C rate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.1
• /
• pp.56-60
• /
• 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.

• Membrane Journal
• /
• v.9 no.4
• /
• pp.215-220
• /
• 1999

The asymmetric polyimide [PI] membrane with good solvent-resisting and heat-resisting properties was prepared by using the phase inversion method from polyamic acid, and its pervaporation separation characteristics of water-acetic acid system were studied. It was appeared from the prepared membranes that the best non-solvent of polyamie acid for the phase inversion was toluene. The best heat-treatment condition for the imidization of polyamic acid was 1 hr heating at each of the temperatures, 373, 473, and 573 K The thermal durability and chemical stability during the pervaporation separation of water-acetic acid of the prepared PI membrane was superior. The pervaporation characteristics of prepared membrane were 180 of separation factor and 0.5 kg/$m^2$hr of total flux for 80 wt% acetic acid feed.