• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.949-958
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• 2018

A voice recognition control system is a system for controlling a peripheral device by recognizing a voice. Recently, a voice recognition control system have been applied not only to smart devices but also to various environments ranging from IoT(: Internet of Things), robots, and vehicles. In such a voice recognition control system, the recognition rate is lowered due to the ambient noise in addition to the voice of the user. In this paper, we propose a dual channel acoustic beamforming hardware architecture for MEMS(: Microelectromechanical Systems) microphones to eliminate ambient noise in addition to user's voice. And the proposed hardware architecture is designed as ASIC(: Application-Specific Integrated Circuit) using TowerJazz $0.18{\mu}m$ CMOS(: Complementary Metal-Oxide Semiconductor) technology. The designed dual channel acoustic beamforming ASIC has a die size of $48mm^2$, and the directivity index of the user's voice were measured to be 4.233㏈.

• Ceramist
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• v.23 no.2
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• pp.211-230
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• 2020

Perovskite-type oxides with the nominal composition of ABO₃ can exsolve the B-site transition metal upon the controlled reduction. In this exsolution process, the transition metal emerges from the oxide lattice and migrates to the surface at which it forms catalytically active nanoparticles. The exsolved nanoparticles can recover back to the bulk lattice under oxidation treatment. This unique regeneration character by the redox treatment provides uniformly dispersed noble metal nanoparticles. Therefore, the conventional problem of traditional impregnated metal/support, i.e., sintering during reaction, can be effectively avoided by using the exsolution phenomenon. In this regard, the catalysts using the exsolution strategy have been well studied for a wide range of applications in energy conversion and storage devices such as solid oxide fuel cells and electrolysis cells (SOFCs and SOECs) because of its high thermal and chemical stability. On the other hand, although this exsolution strategy can also be applied to gas phase reaction catalysts, it has seldomly been reviewed. Here, we thus review recent applications of the exsolution catalysts to the gas phase reactions from the aspects of experimental measurements, where various functions of the exsolved particles were utilized. We also review non-perovskite type metal oxides that might have exolution phenomenon to provide more possibilities to develop higher efficient catalysts.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.5
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• pp.319-325
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• 1999

Direct current(d.c.)leakage current voltage characteristics of radio-frequencymagnetron sputtered BaTa\sub 2\O\sub 6\ film capacitors with aluminum(A1) top and indium tin oxide (ITO) bottom electrodes have been investigatedas a function of applied field and temperature. In order to study surfacetreatment effect on the electrical characteristics of as-deposited film weperformed exposure of oxygen plasma on $BaTa_2O_6$ surface. d. c.current-voltage (I-V), bipolar pulse charge-voltage (Q-V), d. c. current-time (I-t) andcapacitance-frequency (C-f) analysis were performed on films. All ofthe films exhibita low leakage current, a high breakdown field strength (3MV/cm-4.5MV/cm), and high dielectric constant (20-30). From the temperature dependence of leakage current,we can conclude that the dominant conduction mechanism is ascribed toSchottky emission at high electric field (>1MV/cm) and hopping conduction at lowelectric field (<1MV/cm). According to our results, the oxide plasma surfacetreatmenton as-deposited $BaTa_2O_6$ resulted in lowering interfacebarrier height and thus, leakage current when a negative voltage applied to the A1 electrode. This can be explained by reduction of surface contamination via etching surface and filling defects such as oxygen vacancies.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.407-411
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• 2020

In this study, we propose an array-type gas sensor with high selectivity and response using multiple oxide semiconductors. The sensor array was composed of SnO₂ and In₂O₃, and the detection characteristics were improved by using Pt, Au, and Pd catalysts. All samples were deposited directly on the Pt interdigitated electrode (IDE) through the e-beam evaporator glancing angle deposition (GAD) method. They grew in the form of well-aligned nanorods at off-axis angles. The prepared SnO₂ and In₂O₃ nanorod samples were exposed to CH₃COCH₃, C₇H₈, and NO₂ gases in a 300℃ dry condition. Au-decorated SnO₂, Au-decorated In₂O₃, and Pd-decorated In₂O₃ exhibited high selectivity for CH₃COCH₃, C₇H₈, and NO₂, respectively. They demonstrated a high detection limit of the sub ppb level computationally. In addition, measurements from each sensor were executed in the 40% relative humidity condition. Although there was a slight reduction in detection response, high selectivity and distinguishable detection characteristics were confirmed.

• Economic and Environmental Geology
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• v.43 no.6
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• pp.543-553
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• 2010

This study was focused on the mineralogical and geochemical characteristics of field soil of the Baekje Kingdom from K wongbawigol site in Jeongdongri, Buyeo and whether the bricks from Songsanri Tombs and Muryung's Royal Tomb were made of soil from this site. Soil samples show the similar size fraction as a silt loam and acidic soil, whereas some samples have the enrichment of organic matter, P and S. Also, they have similar geochemical behavior of elements and similar mineral phases consisting of quartz, plagioclase, orthoclase, vermiculite, mica and kaolinite. The enrichment of iron oxide is found in some soil layer, including the iron oxide mottling and precipitation along plant roots and they are attributed to repeat oxidation and reduction environments due to flooding and drainage of field soil. It's anthropogenic alteration by human activity. Especially, it is assumed that the concentration of the iron oxides found in bricks from Muryung's Royal Tomb and Songsanri Tombs is the additional evidence that soil in this study is probably the raw materials of those bricks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1016-1022
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• 2010

An Experimental study of cleaning solution has been performed on a high capacity steam boiler burning heavy fuel oil to on-line cleaning of deposit. The deposit is mixture of soot, slag, ash, metal oxide and clinker. The traditional technology of deposit cleaning was carried hand-crafted. The conventional technology of boiler cleaning method is mechanical removal by the worker while the boiler shut down operation. In this experiment, the deposit of mixture of soot, slag, ash, metal oxide and clinker has been removed by the cleaning agents without shut down of boiler burning. This study found out the optimum cleaning solution composition. The best results have been obtained when the mixture of ammonium nitrate and $MgNO_3$ were used in cleaning solution. The various transition metal effect was investigated for optimum mixing condition. In this research, the metal compound additive of the clean solution compoition was obtained. The combustion efficiency was improved by on-line cleaning with derived clean solution compoition. On-line cleaning method prevents the fouling and corrosion in the boiler and heat exchanger.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.401-406
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• 2015

The change of subthreshold swing for channel length of asymmetric double gate(DG) MOSFET has been analyzed. The subthreshold swing is the important factor to determine digital chracteristics of transistor and is degraded with reduction of channel. The subthreshold swing for channel length of the DGMOSFET developed to solve this problem is investigated for channel thickness, oxide thickness, top and bottom gate voltage and doping concentration. Especially the subthreshold swing for asymmetric DGMOSFET to be able to be fabricated with different top and bottom gate structure is investigated in detail for bottom gate voltage and bottom oxide thickness. To obtain the analytical subthreshold swing, the analytical potential distribution is derived from Possion's equation, and Gaussian distribution function is used as doping profile. As a result, subthreshold swing is sensitively changed according to top and bottom gate voltage, channel doping concentration and channel dimension.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.388-389
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• 2005

In this paper, the electric properties of mercury Iodide multi-layer samples has been investigated. We measured and analyzed their performance parameters such as the X-ray sensitivity and dark-current for a mercury Iodide multi-layer X-ray detector with a dielectric layer. The digital X-ray image detector can be constructed by integrating photoconduction multi-layer that dielectric layer has characteristics of low dark-current, high X-ray sensitivity. However this process has found to have complexity on the performance of the sample. We have investigate dielectric layer that it substitute dielectric layer for HgO(Mercury Oxide). We have employed two approaches for producing the mercury Iodide sample : 1) Physical Vapor Deposition(PVD) and 2) Particle-In-Binder(PIB). In this paper fabricated by PIB Method with thicknesses ranging from approximately 180um to 240um and we could produce high-quality samples for each technique particular application. As results, the dielectric materials such as HgO between the dielectric layer and the top electrode may reduce the dark-current of the samples. Mercury Iodide multi-layer having HgO has characteristics of low dark-current, high X-ray sensitivity and simple processing. So we can acquired a enhanced signal to noise ratio. In this paper offer the method can reduce the dark-current in the X-ray detector.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.2
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• pp.76-82
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• 2019

Objectives: To appraise the effectiveness of platelet-rich fibrin (PRF) in the management of established dry socket in terms of pain, inflammation, and wound healing. Materials and Methods: Two hundred patients with established alveolar osteitis were studied to determine the efficacy of PRF and zinc oxide eugenol (ZOE) for pain control, inflammation reduction, and wound healing. Patients were randomly allocated to Group A (PRF) or Group B (ZOE). Patients were examined on the 1st, 3rd, 7th, and 14th postoperative day and evaluated for pain using visual analogue scale scores, inflammation with a gingival index score, and wound healing through a determination of the number of bony walls exposed. Results: Group A showed better results in terms of pain remission, control of inflammation, and wound healing compared to Group B. Results between groups were statistically significant (P<0.05). Conclusion: PRF is a better alternative than ZOE for the effective management of alveolar osteitis.

• Korean Journal of Materials Research
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• v.32 no.12
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• pp.545-552
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• 2022

Tin-antimony sulfide nanocomposites were prepared via hydrothermal synthesis and a N₂ reduction process for use as a negative electrode in a sodium ion battery. The electrochemical energy storage performance of the battery was analyzed according to the tin-antimony composition. The optimized sulfides exhibited superior charge/discharge capacity (770 mAh g^-1 at a current density of 100 mA g^-1) and stable lifespan characteristics (71.2 % after 200 cycles at a current density of 500 mA g^-1). It exhibited a reversible characteristic, continuously participating in the charge-discharge process. The improved electrochemical energy storage performance and cycle stability was attributed to the small particle size, by controlling the composition of the tin-antimony sulfide. By optimizing the tin-antimony ratio during the synthesis process, it did not deviate from the solubility limit. Graphene oxide also acts to suppress volume expansion during reversible electrochemical reaction. Based on these results, tin-antimony sulfide is considered a promising anode material for a sodium ion battery used as a medium-to-large energy storage source.