• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.35-40
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• 2006

In this paper, a current-mode analog variable finite-impulse-response (FIR) filter with variable tap coefficient circuits is proposed for frequency selective wireless personal area network(WPAN) system or terminals. From the circuit simulation the operation of the 7-tap FIR filter is confirmed. The 0.0625-step tap coefficient circuit is designed and fabricated with $0.8[{\mu}m]$ CMOS technology. The proposed FIR filter has a variable length of taps and variable coefficients, so it has a potential for being used to frequency selective WPAN system or frequency selective wireless communication terminals.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6C
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• pp.403-411
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• 2011

This paper addresses a cooperative transmission scheme based on Alamouti coding for cognitive radio networks over frequency selective fading channels. In the proposed scheme, the Alamouti coded form at the destination node is constructed through a simple combination of symbols at the source node, instead of the time-reversal operation and the conjugate operation at the relay nodes used in the conventional scheme. Numerical results show that the proposed scheme achieves a higher order cooperative diversity than that of the conventional scheme.

• Journal of Technologic Dentistry
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• v.37 no.2
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• pp.69-76
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• 2015

Purpose: In this study, the marginal fitness of ceramic Co-Cr metal crown made by precision casting, milling, and selective laser melting method were compared. Methods: The ceramic Co-Cr metal crown manufactured by precision casting used the lost wax(LC specimen) method. The abutment were scanned and then made by milling(CM specimen), selective laser melting(CS specimen) method. The specimen were cut bucco-lingual and mesio-distal, and absolute marginal discrepancy and marginal gap were measured using a digital microscope. The surface roughness of the crown was also observed. Results: On the bucco-lingual axial, absolute marginal discrepancy was the LC specimen $31.72({\pm}4.58){\mu}m$, the CM specimen $78.29({\pm}3.28){\mu}m$ and the CS specimen $143.13({\pm}3.83){\mu}m$, respectively. On the bucco-lingual axial, marginal gap was the LC specimen $22.70({\pm}1.46){\mu}m$, the CM specimen $22.70({\pm}1.49){\mu}m$ and CS specimen $99.60({\pm}1.57){\mu}m$, respectively. Conclusion: For ceramic Co-Cr metal crowns, LC specimen was superior for absolute marginal discrepancy and marginal gap. The surface of metal crowns by selective laser melting were the roughest.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.526-531
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• 1994

In order to develop a new improved selective medium for the Bifidobacterium sp. from the human fecal samples, one hundred eight Bifidobacterium strains were isolated and identified. Sensitivity test for the antibiotics and antimetabolites and test for the specific substrate were performed to obtain basic data for the development of the Bifidobacterium selective medium. TOS(transgalactosylated oligosaccharide) was shown to be preferentially used by Bifidobacterium sp.. Sodium propionate promoted the growth of Bifidobacterium while inhibiting other intestinal bacteria. Upon these results, TP medium was designed and shown to be very effective for the selection of Bifidobacterium and better than Mitsuoka BS medium.

• Current Photovoltaic Research
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• v.2 no.3
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• pp.130-134
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• 2014

We have fabricated the selective emitter solar cell using double textured nanowires structure. The $40{\times}40mm2$-sized silicon substrates were textured to form the pyramid-shaped surface and the nanowires were fabricated by metal assisted chemical etching process using Ag nanoparticles, subsequently. The heavily doped and shallow emitters for selectiv eemitter solar cells were prepared through the thermal $POCl_3$ diffusion and chemical etch-back process, respectively. The front and rear electrodes were prepared following conventional screen printing method and the widths of fingers have been optimized. The selective emitter solar cell using double textured nanowires structure achieved a conversion efficiency of 17.9% with improved absorption and short circuit current density.

• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.121-126
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• 2010

An amperometric ascorbic acid selective sensor utilizing the transfer reaction of proton liberated from the dissociation of ascorbic acid in aqueous solution across an elliptic micro-hole water/organic gel interface is demonstrated. This redox inactive sensing platform offers an alternative way for the detection of ascorbic acid to avoid a fouling effect which is one of the major concerns in redox based sensing systems. The detection principle is simply measuring the current change with respect to the assisted transfer of protons by a proton selective ionophore (e.g., ETH 1778) across the micro-hole interface between the water and the polyvinylchloride-2-nitrophenyloctylether gel phase. The assisted transfer reaction of protons generated from ascorbic acid across the polarized micro-hole interface was first characterized using cyclic voltammetry. An improved sensitivity for the quantitative analysis of ascorbic acid was achieved using differential pulse stripping voltammetry with a linear response ranging from 1 to $100\;{\mu}M$ concentrations of ascorbic acid. As a demonstration, the developed sensor was applied for analyzing the content of vitamin-C in different types of commercial pharmaceutical tablets and syrups, and a satisfactory recovery from these samples were also obtained.

• KSBB Journal
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• v.11 no.6
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• pp.726-732
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• 1996

Selective adsorption of plant metabolites from a polar dilute solution onto a polycarboxyl ester sorbent (XAD-7) was investigated. Experimental results demonstrated that neutral resins could selectively concentrate specific flavonoids from dilute aqueous mixtures. Adsorption was dependent on the pH of medium, dosage of the resins and medium composition. Especially the medium composition was a key factor for the selective adsorption and it was found that the selective adsorption was dependent on specific sorbent-sorbate-medium characteristics. Under the optimum condition, selectivity increased up to 85% and the yield of recovery was approached to 98%. It was also found that XAD-7 adsorbed flavonoids in the order of hydrophobicity.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3592-3596
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• 2011

A novel poly(vinylchloride)-based membrane sensor using $N^1$,$N^3$,$N^5$-tris(2-(2,3-dihydroxybenzylamino)-ethyl)cyclohexane-1,3,5-tricarboxamide (CYCOENCAT, L) as ionophore has been prepared and explored as $Fe^{3+}$ selective electrode. The membrane electrode composed of ionophore, poly(vinylchloride) and o-nitropheyloctyl ether in the optimum ratio 4:33:63 gave excellent potentiometric response characteristics, and displayed a linear log[$Fe^{3+}$] versus EMF response over a wide concentration range of $1.0{\times}10^{-5}-1.0{\times}10^{-1}$ M with super nernstian slope of 28.0 mV/decade and the detection limit of $8.0{\times}10^{-6}$ M. The proposed ion selective electrode showed fast response time (< 15 s), wide pH range (3.0-7.0), high non-aqueous tolerance (up to 20%) and adequate long life time (120 days). It also exhibited very good selectivity for $Fe^{3+}$ relative to a wide variety of alkali, alkaline earth, transition and heavy metal ions. Further, the analytical applicability of the sensor was tested as an indicator electrode in the potentiometric titration of $Fe^{3+}$ with EDTA.

• Corrosion Science and Technology
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• v.15 no.6
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• pp.311-313
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• 2016

The anodic dissolution behavior of copper and brass in an electrolyte solution of 0.5M NaCl containing 0.5 mM $NaHCO_3$ was investigated by electrochemical impedance spectroscopy. The Nyquist plots of the copper impedance described a small loop in the high-frequency range and a large locus in the low-frequency range. Additionally, the features of the impedance spectrum of the brass were similar to those of the copper. This indicates that the copper-enriched layer formed on the brass surface due to the selective dissolution of the zinc from the surface. In addition, the rest potential and the anodic polarization curve for each sample were measured in order to discuss the selective dissolution of the zinc from the brass surface.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.872-876
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• 2017

Laser Based 3D Printing is an recently advance manufacturing technology for making complex shape comopnent such as automobile and aerospace. So in this article, stainless steel 316L was manufactured by Selective Laser Melting (SLM) and Laser Melting Deposition (LMD) method. SLM is an additive manufacturing process that allow for the manufacture of small and complex component by laser melting and solidification of powder in bed using a high intensity laser beam. The results showed that the laser scanning speed and laser power affects the defect, microstructure and the hardness of the components.