• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.81-90
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• 2010

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with antireflective properties. Protonated polystyrene-block-poly (4-vinylpyrine) (PS-b-P4VP) and anionic polystyrene-block-poly (acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the oppositely BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. Furthermore, we demonstrate that the nanostructured electrochemical sensors based on patterning methods show the electrochemical activities. Anionic poly(styrene sulfonate) (PSS) layers were selectively and uniformly deposited onto the catalase (CAT)-coated surface using the micro-contact printing method. The pH-induced charge reversal of catalase can provide the selective deposition of consecutive PE multilayers onto patterned PSS layers by causing the electrostatic repulsion between next PE layer and catalase. Based on this patterning method, the hybrid patterned multilayers composed of platinum nanoparticles (PtNP) and catalase were prepared and then their electrochemical properties were investigated from sensing $H_2O_2$ and NO gas. This study was based on the papers reported by our group. (J. Am. Chem. Soc. 128, 9935 (2006); Adv. Mater. 19, 4364 (2007); Electro. Mater. Lett. 3, 163 (2007)).

• Journal of Power Electronics
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• v.17 no.5
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• pp.1137-1149
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• 2017

In order to reduce the cost, improve the efficiency and simplify the complicated control of existing isolated LED drivers, an improved boundary conduction mode (BCM) Buck ac-dc light emitting diode (LED) driver with extended output voltage and low total harmonic distortion is proposed. With a coupled inductor winding and a stacked output, its output voltage can be elevated to a much higher value when compared to that of the conventional Buck ac-dc converter, without sacrificing the input harmonics and power factor. Therefore, the proposed Buck LED driver can meet the IEC61000-3-2 (Class C) limitation and has a low THD. The operating principle of the topology and the design methodology of the ac-dc LED driver are presented. A 150 W ac-dc prototype was built in the laboratory and it shows that the input current harmonics meet the lighting standard. In addition, the THD is less than 16% at a typical ac input. The peak efficiency is higher than 96.5% at a full load and a normal input.

• Nuclear Engineering and Technology
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• v.37 no.1
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• pp.91-100
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• 2005

Kyung-hee Thorium Fuel (KTF), a heterogeneous thorium-based seed and blanket design concept for pressurized light water reactors, is being studied as an alternative to enhance proliferation resistance and fuel cycle economics of PWRs. The proliferation resistance characteristics of the KTF assembly design were evaluated through parametric studies using neutronic performance indices such as Bare Critical Mass (BCM), Spontaneous Neutron Source rate (SNS), Thermal Generation rate (TG), and Radio-Toxicity. Also, Fissile Economic Index (FEI), a new index for gauging fuel cycle economy, was suggested and applied to optimize the KTF design. A core loaded with optimized KTF assemblies with a seed-to-blanket ratio of 1: 1 was tested at the Korea Next Generation Reactor (KNGR), ARP-1400. Core design characteristics for cycle length, power distribution, and power peaking were evaluated by HELIOS and MASTER code systems for nine reload cycles. The core calculation results show that the KTF assembly design has nearly the same neutronic performance as those of a conventional $UO_2$ fuel assembly. However, the power peaking factor is relatively higher than that of conventional PWRs as the maximum Fq is 2.69 at the M$9^{th}$ equilibrium cycle while the design limit is 2.58. In order to assess the economic potential of a heterogeneous thorium fuel core, the front-end fuel cycle costs as well as the spent fuel disposal costs were compared with those of a reference PWR fueled with $UO_2$. In the case of comprising back-end fuel cycle cost, the fuel cycle cost of APR-1400 with a KTF assembly is 4.99 mills/KWe-yr, which is lower than that (5.23 mills/KWe-yr) of a conventional PWR. Proliferation resistance potential, BCM, SNS, and TG of a heterogeneous thorium-fueled core are much higher than those of the $UO_2$ core. The once-through fuel cycle application of heterogeneous thorium fuel assemblies demonstrated good competitiveness relative to $UO_2$ in terms of economics.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.250-255
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• 2006

A low cost PDP sustain power supply is proposed based on flyback topology using Boundary Conduction Mode(BCM) to control input current regulation. This method guarantees DCM condition to regulate the input current harmonics under all load conditions. An excessive voltage stress due to the link voltage increase can be suppressed by removing link capacitor and adjusting transformer turns ratios, which makes it possible to be used for universal line applications. The proposed converter is tested with a 400W(200V-2A output) prototype circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.1
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• pp.91-97
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• 2014

Recently, the LED(Light Emitting Diode) is expected to replace conventional lamps including incandescent, halogen and fluorescent lamps for some general illumination application, due to some obvious features such as high luminous efficiency, safety, long life, environment-friendly characteristics and so on. To drive the LED, a single stage PFC(Power Factor Correction) flyback converter has been adopted to satisfy the isolation, PFC and low cost. The conventional flyback LED driver has the serious disadvantage of high 120Hz output current ripple caused by the PFC operation. To overcome this drawback, a new PFC flyback with low 120Hz output current ripple is proposed in this paper. It is composed of 2 power stages, the DCM(Discontinuous Conduction Mode) flyback converter for PFC and BCM(Boundary Conduction Mode) boost converter for tightly regulated LED current. Since the link capacitor is located in the secondary side, its voltage stress is small. Moreover, since the driver is composed of 2 power stages, small output filter and link capacitor can be used. Especially, since the flyback is operated at DCM, the PFC can be automatically obtained and thus, an additional PFC IC is not necessary. Therefore, only one control IC for BCM boost converter is required. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a prototype of 24W LED driver are presented.

• Korean Journal of Microbiology
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• v.42 no.2
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• pp.125-130
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• 2006

The emergence of extended spectrum ${\beta}$-lactamase producing bacteria is causing very serious problems in Korea. Although there have been many reports about these bacteria Isolated from patients and clinical specimens, there is no report of extended spectrum ${\beta}$-lactamase producing organisms isolated from natural environment in Korea. This study was conducted to investigate the biological characteristics and extended spectrum ${\beta}$-lactamase types of eighteen strains of extended spectrum ${\beta}$-lactamase producing Klebsiella pneumoniae and Escherichia coli isolated from a slaughterhouse in Pusan in Korea during 2002 to 2004. Extended spectrum ${\beta}$-lactamases were identified by double-disk synergy test, conjugation, isoelectric focusing values and gene sequencing. Eight strains of Klebsiella pneumoniae and two strains of Eschericha coli were isolated kom pigs and transferred extended spectrum ${\beta}$-lactamase genes to recipient Escherichia coli J53 (sodium azide resistant and ceftazidime senstive) strain by conjugation. The conjugants of extended spectrum ${\beta}$-lactamase genes were alignments and translated to amino acids by BCM and NCBI blast. Eight conjugants of Klebsiella pneumonae were typed TEM-52, and two strains of Escherichia coli, SHV-12, but CMY-1 type were not detected in this study.

• Korean Journal of Microbiology
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• v.43 no.2
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• pp.116-123
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• 2007

The purpose of this study was typing the plasmid mediated extended spectrum ${\beta}-lactamases$ produced by enteric bacteria isolated from rivers in Pusan. Six strains of Eschericha coli and fifteen strains of Klebsiella pneumoniae transferred their plasmid mediated extended spectrum ${\beta}-lactamase$ genes to the recipient strain Eschericha coli J53 $Azid^{R}$. The plasmid mediated extended spectrum ${\beta}-lactamase$ genes were sequenced directly after PCR and the types were determined by the BCM Search Launcher and GenBank nucleotid database. Determined types of the plasmid mediated extended spectrum ${\beta}-lactamases$ were TEM-52 and SHV-12. TEM-52 was isolated from both Escherichia coli and Klebsiella pneumoniae. However SHV-12 was isolated from Klebsiella pneumoniae only. The results indicated that the plasmid mediated extended spectrum ${\beta}-lactamase$ producing bacteria spreded over the area of clinical to the nature in Korea.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.363-371
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• 2023

Purpose: This paper aims to develop evaluation criteria of Plan- 'Understanding the Organization' in the PDCA(Plan-Do-Check-Act) requirements of ISO 22301 which is a global standard in the area of BCMS(Business Continuity Management System). Method: The group of 20 experts in the BCMS checked for the validity of the evaluation criteria of Plan- 'Understanding the Organization' by the modified Delphi technique and relative importance are surveyed by the group. Results: As a result, the 12 evaluation criteria with relative importance that can be applied for BCMS evaluation of the organizations are developed and proposed. Conclusion: In order to introduce a quantitive evaluation in the BCMS, it was concluded that evaluation criteria need to be chosen and given relative importance, thus the criteria with the importance could be used for effective evaluation

• Journal of Power Electronics
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• v.19 no.2
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• pp.431-442
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• 2019

This paper proposes a unified high-frequency bipolar buck-boost (UHFBB) control strategy for a dual-active-bridge (DAB), which is derived from the classical buck and boost DC/DC converter. It can achieve optimized current stress of the switches and soft switching in wider range. The UHFBB control strategy includes multi-control-variables, which can be achieved according to an algorithm derived from an accurate mathematical model. The design method for the parameters, such as the transformer turns ratio and the inductance, are shown. The current stress of the switches is analyzed for selecting an optimal inductor. The analysis is verified by the experimental results within a 500W prototype.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.441-452
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• 2009

This paper describes the evaluation technique for climate change effect on daily precipitation frequency using daily precipitation generator that can use outputs of the climate model offered by IPCC DDC. Seoul station of KMA was selected as a study site. This study developed daily precipitation generation model based on two-state markov chain model which have transition probability, scale parameter, and shape parameter of Gamma-2 distribution. Each parameters were estimated from regression analysis between mentioned parameters and monthly total precipitation. Then the regression equations were applied for computing 4 parameters equal to monthly total precipitation downscaled by K-NN to generate daily precipitation considering climate change. A2 scenario of the BCM2 model was projected based on 20c3m(20th Century climate) scenario and difference of daily rainfall frequency was added to the observed rainfall frequency. Gumbel distribution function was used as a probability density function and parameters were estimated using probability weighted moments method for frequency analysis. As a result, there is a small decrease in 2020s and rainfall frequencies of 2050s, 2080s are little bit increased.