Showing papers by "Kwangwoon University published in 2000"
TL;DR: Kinetics analysis from batch studies revealed that the denitrification reaction with nanoscale Fe0 appeared to be a pseudo first-order with respect to substrate and the observed reaction rate constant varied with iron content at a relatively low degree of application, suggesting that theDenitrification appears to be coupled with oxidative dissolution of iron through a largely mass transport-limited surface reaction (<40 rpm).
372 citations
TL;DR: In this article, a practical expert system for the diagnosis of various faults which may occur in distribution substations is presented, where the backward inexact reasoning process is applied for the fault section estimation using the knowledge of topology, the operation rules of protective devices, heuristic knowledge of well-trained operators, and instantaneous alarms.
Abstract: This paper presents a practical expert system for the diagnosis of various faults which may occur in distribution substations. The backward inexact reasoning process is applied for the fault section estimation using the knowledge of topology, the operation rules of protective devices, heuristic knowledge of well-trained operators, and instantaneous alarms. In this paper, the overall structure, detailed knowledge-base and the efficiency of general methodology based on topology are discussed. The proposed system has been tested in a local control center in Korea as a part of an intelligent guidance system for the SCADA operators.
130 citations
TL;DR: For point-of-care examination, an immuno-chromatographic assay system based on conductimetric detection was investigated by utilizing, as signal generator, colloidal gold with polyaniline bound on the metal surface as a conductivity-modulating agent after immobilizing an antibody specific to human albumin used as model analyte.
123 citations
TL;DR: In this paper, the particle size distributions in Co-Al-O insulating granular films with various Co concentrations (x Co ) were investigated by analyzing the superparamagnetic behavior of magnetization.
99 citations
TL;DR: An integrated fuzzy expert system is presented to diagnose various faults that may occur in a regional transmission network and substations to improve efficiency, generality, and reliability of the solution.
Abstract: An integrated fuzzy expert system is presented to diagnose various faults that may occur in a regional transmission network and substations. Fuzzy reasoning method is applied, and it is discussed in detail. Discrimination of false operations or nonoperations of protective devices as well as the fault identification scheme are also analyzed, together with the fuzzy inference process. The proposed system is designed to improve efficiency, generality, and reliability of the solution. The system will replace a fault diagnosis system that had been tested as a part of an intelligent support system on a local control center in Korea.
95 citations
TL;DR: The proposed NC/PbO2 strip sensor is shown to be virtually insusceptible to interfering species such as acetaminophen and ascorbic and uric acids and to exhibit good performance, in terms of the sensor-to-sensor reproducibility, the sensitivity, and the linearity.
Abstract: A new type of disposable amperometric sensor is devised by screen printing thick-film electrodes directly on a porous nitrocellulose (NC) strip. The chromatographic NC strip is then utilized to introduce various sample pretreatment layers. As a preliminary application, a glucose biosensor based on hydrogen peroxide detection is constructed by immobilizing glucose oxidase (GOx) on the NC electrode strip and by formulating a strong oxidation layer (i.e., PbO2) at the sample loading area, placed below the GOx reaction band. The screen-printed PbO2 paste serves as a sample pretreatment layer that removes interference by its strong oxidizing ability. Samples applied are carried chromatographically, via the PbO2 paste, to the GOx layer, and glucose is catalyzed to liberate hydrogen peroxide, which is then detected at the electrode surface. The proposed NC/PbO2 strip sensor is shown to be virtually insusceptible to interfering species such as acetaminophen and ascorbic and uric acids and to exhibit good performance, in terms of the sensor-to-sensor reproducibility (standard deviation, +/-0.026 - +/-0.086 microA), the sensitivity (slope, -0.183 microA/mM), and the linearity (correlation coefficient, 0.994 in the range of 0-10 mM).
94 citations
TL;DR: The results clearly indicated a coexistence of 2D ZnCdSe platelets and 3D islands, showing clearly that the platelets act as precursors for the formation of the3D islands.
Abstract: The evolution of self-assembled CdSe quantum dots deposited on (and subsequently capped by) ZnSe was investigated on a series of samples grown by molecular beam epitaxy, with CdSe coverages from 0.5 to 2.6 monolayers. The samples were investigated by cross-sectional scanning transmission electron microscopy, as well as macro- and microphotoluminescence. The results clearly indicated a coexistence of 2D ZnCdSe platelets and 3D islands, showing clearly that the platelets act as precursors for the formation of the 3D islands.
79 citations
TL;DR: This work demonstrates a transmission of 4 x 10 Gb/s WDM channels over 1.2 km of free space in 1.55-microm band through a fiber-pigtailed collimator and enables the use of standard 100-GHz channel spacing and an optical preamplifier at the receiver.
Abstract: We demonstrate a transmission of 4×10 Gb/s WDM channels over 1.2 km of free space in 1.55-µm band. The transmitted beam is coupled into a single-mode fiber through a fiber-pigtailed collimator, which enables the use of standard 100-GHz channel spacing and an optical preamplifier at the receiver. All the received channels have Q values higher than 6.
67 citations
TL;DR: In this article, an axially extracted virtual cathode oscillator has been fabricated for ultra-high-power microwave generator, which is powered by the "Chundoong" intense relativistic electron beam pulser (Max: 600 kV, 88 kA, and 60 ns duration).
Abstract: An axially extracted virtual cathode oscillator has been fabricated. This ultra-high-power microwave generator is powered by the "Chundoong" intense relativistic electron beam pulser (Max: 600 kV, 88 kA, and 60 ns duration). In this experiment, a solid electron beam with a peak diode current of 21 kA is obtained from the pulser operated at a peak diode voltage of 300 kV. It is found in this experiment that the peak of microwave emission occurred at the moment of the second peak in electron beam current, where the diode voltage V/sub d/ and diode current I/sub d/ are V/sub d/=290 kV and I/sub d/=21 kA, respectively. This observation might be strongly correlated to the inherent oscillations of the electron cloud in time and space originated from both the dynamics of the reflected electron beam due to virtual cathode and oscillations of the virtual cathode itself, from which the peak of high-power microwave can be generated in this experiment. The major operating output frequencies have been measured to be 6.68 GHz/spl les/f/spl les/7.19 GHz based on the waveguide dispersive delayed line method, which is in good agreement with that from "MAGIC" computational results for an electron beam voltage of 290 kV and a diode current of 21 kA. The maximum microwave output power from the virtual cathode oscillator has been measured to be 200 MW in this experiment. while its power conversion efficiency is approximately 3.3%. The dominant emission mode from the virtual cathode oscillator is shown to be the TM/sub 01/ mode based on the emission pattern of microwave induced air breakdown in this experiment.
60 citations
TL;DR: Findings seem to suggest that bis(TFAB)CAs recognize the incoming carbonate ion by forming both covalent and hydrogen bonding between the hydrated and unhydrated TFAB groups.
Abstract: Potentiometric properties of the ion-selective electrodes) based on highly plasticized PVC membranes doped with the carbonate-selective cholic acid (CA) derivatives have been measured. The carbonate-selective neutral carriers have been prepared by coupling one to three trifluoroacetobenzoyl (TFAB) groups to a cholic acid derivative which has three hydroxyl linkers lining on the C3, C7, and C12 positions of its rigid steroidal ring structure. The membranes based on cholic acid derivatives with two TFABs [3,7-bis(TFAB)CA, 3,12-bis(TFAB)CA, and 7,12-bis(TFAB)CA] exhibited remarkably improved carbonate selectivity, indicating that the bis(TFAB)CAs behave like molecular tweezers for the carbonate ion. For example, 3,12-bis(TFAB)CA resulted in 10−300-fold-enhanced carbonate selectivity over other anions (e.g., salicylate, ClO4-, SCN-, HPO42-, NO3-, NO2-, Br-, and Cl-) compared to that of the neutral carriers with a single TFAB group. The distances between the carbonate binding centers of bis(TFAB)CAs, i.e., the...
58 citations
TL;DR: A set of ion-selective membranes for the measurement of clinically relevant electrolytes, i.e., K+, Na+, Ca2+, H+ and Cl−, and a solvent-processible polyurethane (PU)-based reference membrane were cast on metal electrodes patterned on small ceramic plates, and on silicon-based sensors.
Abstract: A set of ion-selective membranes for the measurement of clinically relevant electrolytes, i.e., K+, Na+, Ca2+, H+ and Cl−, and a solvent-processible polyurethane (PU)-based reference membrane were cast on metal electrodes patterned on small ceramic plates, and on silicon-based sensors. Since the liquid junction-free PU membrane-based reference electrode provides a constant potentiometric signal for an extended period of time, accurate determination of blood electrolytes could be made without using a separate reference flow. The PU membrane-based reference electrodes not only improve the mass producibility of miniaturized solid-state ion sensors but also simplify the configuration of flow cell cartridges without compromising their analytical performance.
TL;DR: Symmetrically hindered methylphenols 1 react smoothly with NBS to form transient intermediates, p-benzoquinone methides (BM), which can be further processed to give hydroxybenzaldehydes in the presence of DMSO.
Abstract: Symmetrically hindered methylphenols 1 react smoothly with NBS to form transient intermediates, p-benzoquinone methides (BM), which can be further processed to give hydroxybenzaldehydes in the presence of DMSO. This reaction is initiated by the formation of the phenoxy radical, followed by disproportionation to afford BM. None of the side-chain-brominated product is observed. The existence of BM is supported by the following observations: the formation of BM in solution can be monitored by GC and GC−MS; the electrophilic methine part participates in electrophilic aromatic substitution with anisoles to give hydroxybenzylated products 15; and the double bond character of the exocyclic methine plays a role in [4 + 2] cycloaddition with diene to afford Diels−Alder adducts. In contrast, unsymmetrically hindered or simple methylphenol (p-cresol) with NBS gives the nuclear brominated products, as usual. The energies of symmetrically hindered BMs, unsymmetrically hindered BM, and simple BM were calculated using ...
TL;DR: In this article, a black chrome coating was made on Ni substrates using newly synthesized electrolyte at a current density of 0.3-0.4 A/cm 2 for 20-30 s. The changes in the physical properties of the sample due to thermal degradation were characterized by Auger electron spectroscopy and spectrophotometry.
TL;DR: In this paper, 2-nitro-substituted acylbenzenes or iminobenzenes were cyclized toward 2-1-benzisoxazoles in the presence of 2-bromo-2-nitrogenpropane and indium in an MeOH/H2O solution in excellent yields.
TL;DR: In this article, the effects of initial polymer concentration and zone drawing on the structure, physical properties, and hydrolytic degradation of PBS film were investigated, and it was concluded that the initial concentration of 14 g/dl is the optimum polymer concentration to produce maximum draw ratio in this work.
TL;DR: It was found that the derivatives of thiazole containing dibenzo-18-crown-6 incorporated in PVC-based membranes provide enhanced NH4+ selectivities over alkali metal cations, especially over Na+, compared to those of the nonactin-doped membranes.
Abstract: A new class of crown ethers containing heterocyclic units has been designed to develop synthetic NH4+-selective ionophores whose resulting potentiometric properties in solvent polymeric membranes are superior or at least comparable to those of nonactin. It was found that the derivatives of thiazole containing dibenzo-18-crown-6 (1; TDB18C6) incorporated in PVC-based membranes provide enhanced NH4+ selectivities over alkali metal cations, especially over Na+, compared to those of the nonactin-doped membranes: for example, the selectivity coefficients, log (J = Li+, Na+, K+), for the 2-nitrophenyloctyl ether (NPOE) plasticized PVC membranes doped with the hexyl chain-substituted TDB18C6 (2) were −4.9, −3.9, and −1.3, while those for the same type of membranes with nonactin −4.4, −3.0, and −1.0, respectively. Unlike other synthetic NH4+-selective neutral carriers reported to date, TDB18C6-type compounds result in potentiometric performance highly comparable to that of the nonactin-based ones except their sl...
TL;DR: In this paper, the tunable color emission and solid solubility limit in Ba1−xCaxAl2O4:Eu 0.0012+ phosphors were investigated by using cathodoluminescence (CL) and X-ray diffraction (XRD) measurements.
TL;DR: In this paper, the onset of vortex instability in primary laminar natural convection flow over an inclined plate embedded in a porous medium was analyzed using Forchheimer's model involving thermal dispersion.
TL;DR: In this article, pseudodielectric function data from 1.5 to 6.0 eV using spectroscopic ellipsometry were obtained by fitting model line shapes to numerically calculated second energy derivatives of 〈e〉, from which the bowing parameters and spin-orbit-splitting Δ1 of the E1 and E1+Δ1 gaps were obtained.
Abstract: We report pseudodielectric function data 〈e〉=〈e1〉+i〈e2〉 of Zn1−xMgxSe and Zn1−xBexSe samples grown on GaAs substrates. The data were obtained from 1.5 to 6.0 eV using spectroscopic ellipsometry. Critical point parameters were obtained by fitting model line shapes to numerically calculated second energy derivatives of 〈e〉, from which the bowing parameters and spin-orbit-splitting Δ1 of the E1 and E1+Δ1 gaps were obtained. A transfer of oscillator strength from E1+Δ1 to E1 with increasing Mg and Be composition and a positive bowing of these threshold energies are attributed to the k-linear interaction, which is large in small-band gap semiconductors.
TL;DR: In this article, a new method using a simple zone-drawing technique has been suggested for determining the optimum initial concentration of a polymer solution that has suitable macromolecular entanglements.
Abstract: A new method using a simple zone-drawing technique has been suggested for determining the optimum initial concentration of a polymer solution that has suitable macromolecular entanglements. This method was developed to replace the incorrect inherent viscosity-measuring method for syndiotacticity-rich (syndiotactic diad content of 63.4%) ultrahigh molecular-weight (number-average degree of polymerization of 12,300) (UHMW) poly(vinyl alcohol) (PVA) solution. Syndiotacticity-rich UHMW PVA films were prepared from dimethyl sulfoxide (DMSO) solutions with different initial concentrations: of 0.1, 0.2, 0.3, 0.4, and 0.5 g/dL. In order to investigate the drawing behavior of the syndiotacticity-rich UHMW PVA films with different solution concentrations, the films were drawn under various zone-drawing conditions. Through a series of experiments, it was discovered that the initial concentration of PVA solution in DMSO caused significant changes in the draw ratio of the syndiotacticity-rich UHMW PVA film. That is, the one-step and maximum zone draw ratios of the film at an initial concentration of 0.3 g/dL exhibited its maximum values and gradually decreased at higher or lower concentrations. Thus, it was disclosed that the initial concentration of 0.3 g/dL is the optimum polymer concentration to produce a maximum draw ratio in this work. Based on the above results, it may be concluded that the optimum concentration of the initial PVA solution can be determined directly by measuring the zone draw ratio. The draw ratio, birefringence, crystallinity, degree of crystal orientation, tensile strength, and tensile modulus of the maximum drawn PVA film were 32.9, 0.0449, 0.61, 0.991, 1.91, and 46.2 GPa, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 123–134, 2000
TL;DR: In this paper, the root mean square of the average surface roughness of the ZnO film was 17.2 A and X-ray diffraction and transmission electron microscopy (TEM) measurements showed that the ZNO film layers grown on the InP substrates were epitaxial films with strong (0.0, 0.1) preferential orientation.
TL;DR: In this article, the spin coating method was used on a Pt/Ti/SiO2/Si substrate using PZT (10/90) and PZt (90/10) metal alkoxide solutions.
28 Mar 2000
TL;DR: A two-pass technique for choosing the dictionary entries is proposed, and the trade-offs in bit allocation that these choices entail are discussed, as well as one way to significantly speed up the symbol bitmap compression procedure.
Abstract: The JBIG2 standard for lossy and lossless bi-level image coding is a very flexible encoding strategy based on pattern matching techniques. The encoder collects a set of symbols in a dictionary and encodes a page by reference to the dictionary symbols. JBIG2 allows the encoder to view all symbols and choose a good set for the dictionary. We propose a two-pass technique for choosing the dictionary entries, and discuss the trade-offs in bit allocation that these choices entail. The proposed dictionary design technique outperforms simpler dictionary formation techniques by up to 7-9% and 10-18% for lossless and lossy compression, respectively. In the lossy case, we further point out one way to significantly speed up the symbol bitmap compression procedure.
03 Dec 2000
TL;DR: The Bragg reflector TFR as discussed by the authors is composed of a piezoelectric aluminium nitride thin film, electrodes of Al (1500 /spl Aring/) on both sides and reflector layers of an Al-AlN pair.
Abstract: Bragg reflector thin film resonators (TFR's) using AlN reactively sputtered at room temperature were investigated. The Bragg reflector TFR is composed of a piezoelectric aluminium nitride thin film, electrodes of Al (1500 /spl Aring/) on both sides and reflector layers of an Al-AlN pair. The resonator has a fundamental resonance at 2.81 GHz with a return loss of 3.07 dB.
TL;DR: A variety of neutral carrier type ionophores for monovalent cations were employed to prepare solid-state cation-selective electrodes (SSEs) for use as a detector in single-column ion chromatography.
TL;DR: In this article, an angle-tuned Fabry-Perot etalon filter with periodic Gaussian transmittance curves down to 40 dB from peak transmissions in spectral domain is presented.
Abstract: We present an angle-tuned Fabry-Perot etalon filter that has periodic Gaussian transmittance curves down to 40 dB from peak transmissions in spectral domain. This unique property becomes possible introducing an offset to the output-coupling fiber with respect to the incident Gaussian beam. This filter can be used not only as a general-purpose narrow bandwidth filter but also as an optical noise filter for wavelength-division multiplexed channels to eliminate the amplified-spontaneous emission or the back-scattered lights in bidirectional transmissions.
TL;DR: An extended split-step time-domain model for composite coupling structures is reported and through an analysis of an add-drop filter based on a grating-written directional-coupler structure, the proposed modeling method is shown to be an order of magnitude more efficient than the previous methods.
Abstract: An extended split-step time-domain model for composite coupling structures is reported. Time-dependent coupled-wave equations are solved by splitting of the operators for phase accumulation, forward directional coupling, and reverse Bragg reflection. Through an analysis of an add–drop filter based on a grating-written directional-coupler structure, the proposed modeling method is shown to be an order of magnitude more efficient than the previous methods.
TL;DR: In this article, the structural, optical, and electrical properties of the GaN epitaxial films grown on porous Si(100) by plasma-assisted molecular-beam epitaxy with a two-step method were investigated.
Abstract: A new approach was used for combining GaN and porous Si with the goal of producing high-quality GaN epitaxial layers for optoelectronic integrated circuit devices based on Si substrates. Reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), photoluminescence (PL), and Van der Pauw–Hall effect measurements were performed to investigate the structural, optical, and electrical properties of the GaN epitaxial films grown on porous Si(100) by plasma-assisted molecular-beam epitaxy with a two-step method. The RHEED patterns were streaky with clear Kikuchi lines, which was direct evidence for layer-by-layer two-dimensional growth of GaN epitaxial layers on porous Si layers. The XRD curves showed that the grown layers were GaN(0001) epitaxial films. The results of the XRD and the PL measurements showed that the crystallinities of the GaN epilayers grown on porous Si by using a two-step growth were remarkably improved because the porous Si layer reduced the strains in the GaN epilayers by sharing them with the Si substrates. Hall-effect measurements showed that the mobility of the GaN active layer was higher than that of the GaN initial layer. These results indicate that high-quality GaN epitaxial films grown on porous Si(100) by using two-step growth hold promise for potential applications in new kinds of optoelectronic monolithic and ultralarge integrated circuits.
12 Dec 2000
TL;DR: A pseudo static walking gait with dynamic gait modification method by adjusting the position of a hip joint is proposed that makes foot landing easy, and weight and cost of legs are also reduced.
Abstract: Presents a compliant ankle mechanism and its implementation for a biped robot without actuators for the ankle joints. Ankle joints have been built using springs and mechanical constraints, which give a flexibility of joint within a predefined range and stiffness beyond the range. The biped with compliant ankles proposed makes foot landing easy, and weight and cost of legs are also reduced. The cost of the advantages is that the control problem becomes more difficult because the control torque of the ankle joint to put the biped in a desired walking gait can not be provided from the compliant ankle joint. To overcome this problem, we propose a pseudo static walking gait with dynamic gait modification method by adjusting the position of a hip joint. Experimental results with the biped KUBCA are given to show the validity of the proposed controller.
TL;DR: The proposed differential pCO2 microelectrodes exhibited significantly improved performance in their preconditioning period, response and recovery times, stability, response slope, and lifetime.
Abstract: To develop planar microchemical pCO2 sensing devices with improved electrochemical properties, we combined two advanced technologies. One is a differential sensor arrangement to simplify the microfabrication procedure by employing pH-sensitive gas-permeable membranes, and the other is the use of an enzyme (carbonic anhydrase) to shorten total measurement time by accelerating the rate of CO2 hydration. The adhesion of the polyurethane−matrix gas-permeable membrane is enhanced significantly by incorporating a silanizing reagent (silicon tetrachloride), improving the stability and extending sensor lifetime. The proposed differential pCO2 microelectrodes exhibited significantly improved performance in their preconditioning period, response and recovery times, stability, response slope, and lifetime.