• Proceedings of the KOR-KST Conference
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• 2001.02a
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• pp.135-155
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• 2001

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.224-229
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• 2006

Many studies have been done on the application of residual charge measurement in cable degradation diagnosis. In this paper, the behavior of residual charges measured with water-tree degraded XLPE sheets and cable are discussed. At charge injection process, the charge is injected by applying dc voltage as a conventional method, suddenly cut-off ac voltage or impulse voltage. Therefore the residual charge is influenced by the applying process. At charge release process, transient dc current flows when applying ac high voltage and also ac high voltage superimposed to dc low voltage. From the results, new diagnosis method is suggested.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.1
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• pp.62-71
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• 2011

There is widespread concern that particulate filtering respirators (PFRs) available in Korea will be efficient for nanoparticles. The purpose of this review study was to analyse research literature and recommend PFRs suitable for protection against nanoparticles. In all studies, respirators containing electret filter media (N95, P100 and FFP2, FFP3) consistently have their MPPS below 100 nm and particle penetration levels at the MPPS can vary widely, but they comply with NIOSH or EN certification criterion. Electret filtering facepieces respirators (FFRs) were found to shift in the Most-Penetrating Particle Size(MPPS) from 30-60 to 200-300 nm range after the electric charges were removed, and FFRs were above their minimum penetrations of criterion. Korean special class and first class FFRs (the same as FFP3 and FFP2, respectively) would be effcient for nanoparticles unless FFRs are removed electric charges. It is difficult to evaluate if mechanical PFRs is efficient for nanoparticles due to the lack of related materials.

• BMB Reports
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• v.36 no.3
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• pp.243-250
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• 2003

In this paper we investigate (using AM1 semi-empirical as well as HF methods at the STO-3G, 3-21G, 6-31G, 6-$31G^*$ and 6-31+$G^{**}$ level) the conformations, geometrical parameters, Mulliken charges, and solvation effects of the triphosphate form of AZT (AZTTP), as well as the thymidine nucleotide (dTTP) structure. Our calculated geometrical parameters and Mulliken charges, with and without solvation effects, are correlated with recent experimental results.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1997.10a
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• pp.239-242
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• 1997

Subscriber network investment cost is a main cost element among those constituting the access charges in telephone networks. The purpose of this paper to estimate the investment cost of installing a subscriber network in a typical metropolitan area and to develop a cost modeling framework. To this aim, a metropolitan area in Seoul was investigated. The main cost elements were identified and their relationships with the cable technology, geographical characteristics, and the number of subscribers were analyzed. The findings could be used to design an enhanced cost proxy models for estimating the access charges in a multi-operator environment.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1681-1683
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• 1998

Unlike AC, DC dielectric characteristics of the spacer are very influenced by the quantity and the distribution of surface charges. A general impression of the distribution of surface charges is obtained if electrostatic powders are sprinkled over the surface. The distribution of surface charge was investigated with dust figures. Mechanism of charge accumulation on the spacer of $SF_6$ GIS has been studied using various types of model spacers which have different depths. As a result, it was found that charge accumulation was dominantly influenced by the normal component of the electric field and the usage of embedded electrodes was an adequate method to lessen field concentration around the triple junction. The guide of the optimum depth of the spacer was proposed.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.229-230
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• 2008

The investigations included the measurements of volume currents and also internal space charges on epoxy samples of mm thicknesses. The current versus time relations were shown to correspond well with classical forms of dielectric response such as the Curie-von Schweidler model. After the time transient, near steady currents were extremely small and exhibited a significant temperature dependence, similar in relation to the Poole-Frenkel hoping transport model. Equivalent resistances were on the order of $10^{19}$ ohms and represent very weak charge transport. Electrically stimulated acoustic waves were used to quantify the small internal charges that would accumulate within the epoxy. There was a notable homocharge near both anode and cathode. The dielectric response and the internal charge were related to show a consistent model for charge transport within unfilled epoxy.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.305-308
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• 2003

It is widely used that a network termination rate is calculated by using a Long Run Incremental Costing model. Interconnection Order issued Ministry of Information and Communication in Korea on December 2002 has declared that termination charges of local, national, payphone, and mobile calls are going to be determined by LRIC costing models after 2004. There are lots of preceding researches on a fixed network costing model for applying to LRIC method but on a mobile network not pretty much of them. Besides, Most important basis of current calculation models for termination charges are access costs to connect subscribers to network such as a local loop. In this paper, we look into being of access costs in mobile network and show the applicable standards for cost allocation of access costs in implementing LRIC costing model.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.281-286
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• 2001

Since the number of amino groups which are exposed by deacetylation of acetyl-D-glucosamine influences antimicrobial activity, a chitosan oligosaccharide (COS) derivative by N-conjugation of COS with asparagine, an amino acid with two amino groups, was synthesized and the antimicrobial effect on E. coli growth was compared with other COS derivatives which were N-conjugated with glycine, alanine, aspartic acid, cysteins, an methionine, and unmodified COS. The structure of asparagine N-conjugated COS (Asn-COS) derivative was identified by using a FT-IR, $^{13}C\;FT-NMR$, and an elemental analyzer. The antimicrobial activity of Asn-COS against E. coli growth was significantly improved as compared to the other COS derivatives as well as COS itself. This means that Asn-COS with two positive charges strongly interacts with the carboxyl negative charges on the bacteria cell wall. The results for Asn-COS were as follows: 100% bactericidal activity, 0.002% MIC, and no growth of E. coli during 3 days of culture time, suggesting that Asn-COS may be useful as a new antibiotic agent.

• Journal of Astronomy and Space Sciences
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• v.32 no.2
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• pp.141-144
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• 2015

In this paper we study the transmission of the electrostatic field due to coulomb charges of an individual thundercloud into the midlatitude ionosphere, taking into account the total geomagnetic field integrated Pedersen conductivity of the ionosphere. It is shown that at ionospheric altitudes, a typical thundercloud produces an insignificant electrostatic field whereas a giant thundercloud can drive the horizontal electrostatic field with a magnitude of ${\sim}270{\mu}V/m$ for nighttime conditions.