• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.804-812
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• 2001

A triboelectrostatic separation system for removing unburned carbon from coal fly ash is designed and evaluated. Fly ash from a coal-fired power plant is used as an accepted additive in concrete where it adds strength, sulfate resistance and reduced cost, provided acceptable levels of unburned carbon are maintained. Unfortunately, unburned carbon in coal fly ash absorbs some of other additives and reduces the concrete strength. This paper describes to investigate dry triboelectrostatic process to separate unburned carbon from coal fly ash and utilize it into economically valuable products. The laboratory-scale triboelectrostatic separation system consists of a particle feeding system, a tribocharger, a separation chamber, and collection systems. Particles of unburned carbon and fly ash can be imparted positive and negative surface charges, respectively, with a copper tribocharger due to differences in the work function values of the particles and the tribocharger, and can be separated by passing them through an external electric field. Results showed that fly ash recovery was strongly dependent on the electric field strength and the particle size. 70wt% of fly ash containing 6.5wt% of carbon contents could be recovered at carbon contents below 3%. The triboelectrostatic separation system showed a potential to be an effective method for removing unburned carbon from coal fly ash.

• Korean Membrane Journal
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• v.6 no.1
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• pp.61-69
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• 2004

Small angle light scattering (SALS) and field emission scanning electron microscope (FE-SEM) have been used to investigate the effects of alcohol on phase separation of chlorinated poly(vinyl chloride) (CPVC)/tetrahydrofuran (THF)/alcohol (9/61/30 wt%) solution during water vapor induced phase separation. A typical scattering pattern of nucleation & growth (NG) was observed for all casting solutions of CPVC/THF/alcohol. In the case of the phase separation of CPVC dope solution containing 30 wt% ethanol or n-propanol, the demixing with NG was observed to be heterogeneous. Meanwhile, the phase separation of CPVC dope solution with 30 wt% n-butanol was found to be predominantly homogeneous NG. Although the different phase separation behavior of NG was observed with types of alcohol additives, the resultant surface morphology had no remarkable differences. That is, even though the NG process by water vapor is either homogeneous or heterogeneous, this difference does not play a main role on the final surface morphology. However, it was estimated from the result of hydraulic flux that the phase separation by homogeneous NG provided the membrane geometry with lower resistance in comparison with that by heterogeneous one.

• Proceedings of the Membrane Society of Korea Conference
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• 1991.10a
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• pp.9-16
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• 1991

The current status of reverse osmosis and ultrafiltration membranes are reviewed with the view for the future. In the case of reverse osmosis (RO) membranes, as examples, new crosslinked aromatic polyamide membranes exhibited the superior separation performance with the sufficient water permeability, the high tolerance for oxidizing agents and chemicals. Ultrafiltration (UF) membrane based on poly(phenylene sulfide sulfone) (PPSS) also exibited the superior separation performance with the high solvent, heat and fouling resistance.

• Macromolecular Research
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• v.12 no.1
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• pp.11-21
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• 2004

Toughening of epoxy resins for improvement of crack resistance has been the subject of intense research interest during the last two decades. Epoxy resins are successfully toughened by blending with a suitable liquid rubber, which initially remains miscible with epoxy and undergoes a phase separation in the course of curing that leads to the formation of a two-phase microstructure, or by directly blending preformed rubbery particle. Unlike the situation for thermoplastics, physical blending is not successful for toughening epoxy resins. Recent advances in the development of various functionalized liquid rubber-based toughening agents and core-shell particles are discussed critically in this review.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.590-598
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• 1988

Viscous flows through a screen normal to an uniform flow are numerically simulated. A .kappa.-.epsilon. model is adopted for evaluation of the Reynolds stresses. The existence of a screen is regarded as extra sources in the momentum equations. The amount of extra sources is related to the resistance coefficient and the refraction coefficient of the screen. Flows are numerically simulated for various resistance coefficients and heights of the screen and Reynolds numbers. The present method has been verified to reasonably simulate viscous wakes and shear layers of the screen, for which the inviscid theory is quite limitted. As the fluids approach the screen, the velocity is reduced and the pressure is raised to satisfy the Bernoulli equation. After passing the screen, the velocity shows its minimum value at the down-stream, but static pressure is slowly recovered. A detached separation-bubble from the screen appears as the resistance coefficient is increased to a certain level. Such results are qualitatively in agreement with limitted experimental data available. The turbulent kinetic energy shows its maximum value at further down stream and decrease thereafter.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.3
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• pp.371-380
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• 2004

In the dust separation by using porous filter media, the structure of dust layer deposited on the filter surface of filter medium directly affects the effective filtration. The present study has investigated the specific resistance (K$_2$') of the dust layer and its porosity ($\varepsilon$$_{c}$) for three different filters; FA composite filter, metal fiber filter and stainless filter. The specific resistance (K$_2$') increased and at the same time the cake porosity ($\varepsilon$$_{c}$) decreased with the increase of filtration velocity, possibly due to the compressible effect of dust layer. However, under the low dust concentration, subsequent dust particles would block the open channels through the layer resulting in high specific resistance of the layer. The FA composite filter among three filters was shown to be the most effective filter for dust cake filtration at low filtration velocities less than 0.1 m/s for an approximate dust concentration of 5 g/㎥.

• 전기의세계
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• v.23 no.6
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• pp.49-55
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• 1974

Amorphous semiconductor from As 30 Te 48 Ge 10 Si 12 was prepared, and studied electron microscopy, X-ray analysis and resistivity measurement. It's resistivity is 1.56*10$^{6}$ .ohm.-cm when small ampule is used for preparing sample it is found that no phase separation has occurced by electron microscopy, and that phase transition temperature is 232.deg. C by differential Thermal Analysis. The specimen showed threshold switching that the low resistance state occur at critical electric field and the resistance recover at low applied field. Critical electric field of the switching is 10$^{5}$ V/cm at room temperature. Threshold voltage secreace exponentially with increasing ambient temperature and at that each voltage resistance of the switching device increase exponentially. According to the series resistance and applied vottage current slope on the V-I curve is varied. When applied voltage is decreased after switching, the resistance of the switching device is increased. By this result the origin of the switching is the Joule's heating.

• Membrane Journal
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• v.30 no.6
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• pp.385-394
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• 2020

In the gas separation process, the separation membranes have to not only show high gas transport and selectivity but also exhibit exceptional stability at high temperature and pressure. However, when the polymeric membranes (particularly, glassy polymers) are exposed to the condensable gases (i.e., CO2, H2S, hydrocarbon, etc.), the polymer chains are prone to swell, leading to low stability. As a result, the plasticization behavior reduces the gas selectivity in the separation of mixture gases at high pressures and thus results in limited applications to the separation processes. To address these issues, many strategies have been studied such as thermal treatment, polymer blending, thermally rearrangement, mixed-matrix membranes, cross-linking, etc. In this review, we will understand the plasticization behavior and suggest potential methods based on the previously reported studies.

• Journal of Environmental Health Sciences
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• v.39 no.3
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• pp.239-246
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• 2013

Objectives: Antimicrobial resistance and multidrug resistance patterns have been studied with a total of 189 samples of Salmonella Enteritidis and Salmonella Typhimurium isolated from diarrhea patients in Incheon from 2008 to 2012. Methods: Antimicrobial resistance tests were determined by Disc Diffusion method. Results: The serological distribution of Salmonella spp. showed 108 strains (30.1%) of S. Enteritidis, 81 strains (22.6%) of S. Typhimirium, eight strains (8.0%) of S. Typhi, 11 strains ( 3.1% ) of S. Paratyphi, and the 151 other strains (42.1%). The separation rate of Salmonella spp. by year showed 14.5% (52 strains) in 2008, 13.6% (49 strains) in 2009, 22.8% (82 strains) in 2010, 25.3% (91 strains) in 2011, and 23.7% (85 strains) in 2012. Additionally, the separation rate of S. Enteritidis and S. Typhimirium in 2010 was the highest. The Salmonella spp. isolated from diarrhea patients showed significant differences according to age (p<0.05), gender (p<0.01) and medical institution (p<0.05). The highest resistance was found to the following antimicrobial agents: imipenem 77 strains, ampicillin 47 strains, ciprofloxacin 34 strains, nalidixic acid 29 strains for S. Enteritidis, and ampicillin 45 strains, nalidixic acid 45 strains for S. Typhimurium. Separated S. Enteritidis and S. Typhimurium resistance to the antibiotics by the year showed significant differences (p<0.05). The patterns of multidrug resistance rates were 43.1% (47 strains) for one drug, 8.3% (9 strains) for two drugs, 11.0% (12 strains) for three drugs, 15.62% (17 strains) for four drugs, and 13.7% (15 strains) for five or more drugs for S. Enteritidis. For S. Tyhpimurium, the rates were 15.0% (12 strains) for one drug, 10.0% (8 strains) for two drugs, 6.3% (five strains) for three drugs, 18.7% (15 strains) for four drugs, and 23.8% (19 strains) for five or more drugs. Conclusion: The antibiotic resistance issue is directly related to people's lives. Thus, the usage of antibiotics should be reduced in order to manage antibiotic resistance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1722-1741
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• 2017

Intrusion detection techniques based on virtual machine introspection (VMI) provide high temper-resistance in comparison with traditional in-host anti-virus tools. However, the presence of semantic gap also leads to the performance and compatibility problems. In order to map raw bits of hardware to meaningful information of virtual machine, detailed knowledge of different guest OS is required. In this work, we present VDSM, a lightweight and general approach based on driver separation mechanism: divide semantic view reconstruction into online driver of view generation and offline driver of semantics extraction. We have developed a prototype of VDSM and used it to do intrusion detection on 13 operation systems. The evaluation results show VDSM is effective and practical with a small performance overhead.