• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.381-386
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• 2017

A railway track generates severe levels of vibrations. In order to reduce these vibrations and to provide structural stability, various rail pads, mats, etc., are used for vibration protection. In this study, a specially designed rail pad was developed to reduce vibration and to generate electric power simultaneously, that is, by using the vibrations generated by railway cars on the track. The newly developed rail pads were tested to evaluate the characteristics of electric power by investigating the generated voltage and the current levels and patterns. In addition, we proposed an optimal laminated structure and adhesive by comparing the voltage generated by each type of adhesive required for optimal adhesion of the rail pad and the piezoelectric device.

• 한국염색가공학회지
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• 제16권4호
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• pp.10-18
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• 2004

In this work, Aqueous sericin solution was prepared by degumming process with electrolytic reduction water. Then, the microfiltration and ultrafiltration systems were applied to the concentration of aqueous sericin solution. The objective of this study was to select the optimum operating condition among the different pressure. The permeate flux and rejection ratio were observed with time, pressure, flow rate and concentration. and, the wastewater and permeated water quality values such as pH, BOD, COD, and NH levels were measured. In order to see the influence of electrolytic reduction water, the flux of pure water and electrolytic reduction water by PVDF22(MF) and PS100(UF) membrane was measured. In microfiltration system, the relative flux reduction decreased rapidly to 0.02 in the 30min, as the concentration polarization and gel layer formation were increased. and then the sericin concentration rejection ratio was 40%. In ultrafiltration system, the permeate flux decreased with time and concentration, and increased with the operating pressure and flow rate. Optimal condition in PS100 membrane system for sericin concentration was operating pressure 1.464kgf/$cm^24, operating flow rate $7\ell/min at\; 40^{\circ}C$. At that time, sericin concentration rejection ratio was 83% respectably. The sericin solution was concentrated from 0.1wt% solution to 0.2 wt % solution during about 2 hrs by the UF filteration membrane system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.714-717
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• 2007

In this study, a novel actuator was developed by employing the newly-synthesized ionic networking membrane (INM) of poly (styrene-alt-maleic anhydride) (PSMAn)-incorporated poly (vinylidene fluoride) (PVDF). Based on the same original membrane, various samples of INM actuator were prepared through different reduction times with the electroless-plating technique. The as-prepared INM actuators were tested in terms of surface resistance, platinum morphology, resonance frequency, tip displacement, current and blocked force, and their performance was compared to that of the widely-used traditional Nafion actuator. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) revealed that much smaller and more uniform platinum particles were formed on the surfaces of the INM actuators as well as within their polymer matrix. Although excellent harmonic response was observed for the newly-developed INM actuators, this was found to be sensitive to the applied reduction times during the fabrication. The mechanical displacement of the INM actuator fabricated after optimum reduction times was much larger than that of its Nafion counterpart of comparable thickness under the stimulus of constant and alternating current voltage.

• 전기학회논문지
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• 제67권7호
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• pp.860-864
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• 2018

The signal of space charge distribution measured in polymer insulating materials by the PEA has some noises due to the system circuits and the ringing phenomena in the sensor of PVDF and so on forth. It's magnitude mainly depends on the thickness of the insulation material, and it is also affected by the attenuation and dispersion when traveling in a dielectric material. In order to make it reliable, the correcting process for the signal is essential. In this study, we proposed the new deconvolution process on the measured signal of space charge distribution in the flat XLPE insulator, and developed a new signal processing algorithm. Using this, we could improve the reliability of the measured signal much and analyze the effects of space charge clearly in materials.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.60-65
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• 2014

This article explains the experimental results of ferroelectric polarization switching (FPS) of potassium nitrate ($KNO_3$) with different polymers such as polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF) using simple melt-press techniques. To analyze the ferroelectric polarization switching in potassium nitrate ($KNO_3$) composite films at room temperature, we applied the Ishibashi and Takagi theory (based on Avrami model) to the switching current transient. To investigate the dimensionality of domain growth, the ferroelectric polarization switching current (FPS current) was observed from the square - wave bipolar signals across a resistance of $0.1k{\Omega}$ in series with the composite films. The existence of a switching current transient pulse confirmed the ferroelectricity and indicated the stability of the ferroelectric phase (phase III) of $KNO_3$ at room temperature. Polarization hysteresis (P-E) characteristics supported the prominent features of ferroelectric polarization switching in the composite films at room temperature.

• Membrane and Water Treatment
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• 제9권1호
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• pp.53-62
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• 2018

In this study, vacuum membrane distillation (VMD) was used to treat high-salinity wastewater (concentration about 17%) discharged by chlor-alkali plant after resin regeneration. The feasibility of VMD for the treatment of real saline wastewater by using Polyvinylidene fluoride (PVDF) microporous plate membrane with a pore diameter of $0.2{\mu}m$ was investigated. The effects of critical operating parameters such as feed temperature, velocity, vacuum degree and concentration on the permeate water flux were analyzed. Numerical simulation was used to predict the flux and the obtained results were in good agreement with the experimental data. The results showed that an increase in the operating conditions could greatly promote the permeate water flux which in turn decreased with an increase in the concentration. When the concentration varied from 17 to 25%, the permeate water flux dropped marginally with time indicating that the concentration was not sensitive to the decrease in permeate water flux. The permeate water flux decreased sharply until zero due to the membrane fouling resistance as the concentration varied from 25 to 26%. However, the conductivity of the produced water was well maintained and the average value was measured to be $4.98{\mu}s/cm$. Furthermore, a salt rejection of more than 99.99% was achieved. Overall, the outcome of this investigation clearly indicates that VMD has the potential for treating high-salinity wastewater.

• Membrane and Water Treatment
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• 제2권1호
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• pp.1-24
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• 2011

The deficiency of clean water is a major global concern because all the living creatures rely on the drinkable water for survival. On top of this, abundant of clean water supply is also necessary for household, metropolitan inhabitants, industry, and agriculture. Among many purification processes, advances in low-energy membrane separation technology appear to be the most effective solution for water crisis because membranes have been widely recognized as one of the most direct and feasible approaches for clean water production. The aim of this article is to give an overview of (1) two new emerging membrane technologies for water reuse and desalination by forward osmosis (FO) and membrane distillation (MD), and (2) the molecular engineering and development of highly permeable hollow fiber membranes, with polyvinylidene fluoride (PVDF) and polybenzimidazole (PBI) as the main focuses for the aforementioned applications in National University of Singapore (NUS). This article presents the main results of membrane module design, separation performance, membrane characteristics, chemical modification and spinning conditions to produce novel hollow fiber membranes for FO and MD applications. As two potential solutions, MD and FO may be synergistically combined to form a hybrid system as a sustainable alternative technology for fresh water production.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1689-1696
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• 2020

In this study, we developed a fiber-optic humidity sensor (FOHS) system for the monitoring and detection of coolant leakage in nuclear power plants. The FOHS system includes an FOHS, a spectrometer, a halogen white-light source, and a Y-coupler. The FOHS is composed of a humidity-sensing material, a metal tube, a multi-mode plastic optical fiber, and a subminiature version A (SMA) fiber-optic connector. The humidity-sensing material is synthesized from a mixture of polyvinylidene fluoride (PVDF) in dimethyl sulfoxide (DMSO) and hydroxyethyl cellulose (HEC) in distilled water. We measured the optical intensity of the light signals reflected from the FOHS placed inside the humidity chamber with relative humidity (RH) variation from 40 to 95%. We found that the optical intensity of the sensing probe increased linearly with the RH. The reversibility and reproducibility of the FOHS were also evaluated.

• 한국환경과학회지
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• 제25권6호
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• pp.817-827
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• 2016

The resistance in series model has been frequently used for determination of various filtration resistance to correctly understand the membrane fouling behaviour in MBR (membrane bio-reactor) for wastewater treatment. The cake layer resistance ($R_c$) which is commonly determined by calculation of flux dataset that are obtained empirically before and after removing the cake layer on membrane surface. However, the calculated Rc values are very dependent on the cleaning methods adapted for removal of cake layer. This study investigated how the various cleaning options affect $R_c$. Seven different cleaning methods were employed: i) ultrasonication (100 W, 10 min), ii) ultrasonication (200 W, 60 min), iii) ultrasonication (400 W, 120 min), iv) water rinsing in a shaker (100 rpm, 10 min), v) water rinsing in a shaker (300 rpm, 60 min), vi) water rinsing, vii) sponge scrubbing. For the hydrophilic PES membrane, the cake layer removal efficiencies ranged from 64% to 10%, indicating that the removal of cake layer was highly dependent on the cleaning options. For the hydrophobic PVDF membrane, the cake layer removal efficiencies ranged from 79% to 97%. Consequently, a standardized method for cake layer removal to determine cake resistance ($R_c$) is needed for correct interpretation of the fouling phenomena.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.331-337
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• 2006

높은 이온전도도와 충분한 기계적 강도, 전해질 누수가 적은 새로운 형태의 고분자 전해질막(pore-gel SPE)을 연구 개발하였다. 다공성 PVDF-HFP 고분자막의 기공 내에 전해질 용액을 흡수시킨 후 막 내에서 젤화를 진행시켰다. 전해질 용액은 2:2:1의 비를 갖는 PC/EC/DMA에 1M SA(Salicylic acid)를 용해하고 여기에 고분자막을 용해시킬 수 있는 아세톤을 첨가하였다. 초음파를 이용함으로써 고분자막의 용액 흡수율을 증가시키고 또 고분자막에서 젤화를 촉진 시킬 수 있었다. 이렇게 젤화한 막의 이온전도도는 젤화 전 막보다 $1{\sim}2.2$ 배 향상되었고, 인장강도는 gel-type SPE 보다 40 배 증가하였으며, 전해질 누수실험결과 hybrid-type SPE는 13%의 누수를 보였으나 본 연구의 막(pore-gel SPE)은 6%로 감소함을 보였다.