• Title/Summary/Keyword: Limiting current density

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4-Channel 2.5-Gb/s/ch CMOS Optical Receiver Array for Active Optical HDMI Cables (액티브 광케이블용 4-채널 2.5-Gb/s/ch CMOS 광 수신기 어레이)

  • Lee, Jin-Ju;Shin, Ji-Hye;Park, Sung-Min
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.49 no.8
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    • pp.22-26
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    • 2012
  • This paper introduces a 2.5-Gb/s optical receiver implemented in a standard 1P4M 0.18um CMOS technology for the applications of active optical HDMI cables. The optical receiver consists of a differential transimpedance amplifier(TIA), a five-stage differential limiting amplifier(LA), and an output buffer. The TIA exploits the inverter input configuration with a resistive feedback for low noise and power consumption. It is cascaded by an additional differential amplifier and a DC-balanced buffer to facilitate the following LA design. The LA consists of five gain cells, an output buffer, and an offset cancellation circuit. The proposed optical receiver demonstrates $91dB{\Omega}$ transimpedance gain, 1.55 GHz bandwidth even with the large photodiode capacitance of 320 fF, 16 pA/sqrt(Hz) average noise current spectral density within the bandwidth (corresponding to the optical sensitivity of -21.6 dBm for $10^{-12}$ BER), and 40 mW power dissipation from a single 1.8-V supply. Test chips occupy the area of $1.35{\times}2.46mm^2$ including pads. The optically measured eye-diagrams confirms wide and clear eye-openings for 2.5-Gb/s operations.

Preparation of Hafnium Oxide Thin Films grown by Atomic Layer Deposition (원자층 증착법으로 성장한 HfO2 박막의 제조)

  • Kim Hie-Chul;Kim Min-Wan;Kim Hyung-Su;Kim Hyug-Jong;Sohn Woo-Keun;Jeong Bong-Kyo;Kim Suk-Whan;Lee Sang-Woo;Choi Byung-Ho
    • Korean Journal of Materials Research
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    • v.15 no.4
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    • pp.275-280
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    • 2005
  • The growth of hafnium oxide thin films by atomic layer deposition was investigated in the temperature range of $175-350^{\circ}C$ using $Hf[N(CH_3)_2]_4\;and\;O_2$ as precursors. A self-limiting growth of $0.6\AA/cycle$ was achieved at the substrate temperature of $240-280^{\circ}C$. The films were amorphous and very smooth (0.76-0.80 nm) as examined by X-ray diffractometer and atomic force microscopy, respectively. X-ray photoelectron spectroscopy analysis showed that the films grown at $300^{\circ}C$ was almost stoichiometric. Electrical measurements performed on $MoW/HfO_2$(20 nm)/Si MOS structures exhibited high dielectric constant$(\~17)$ and a remarkably low leakage current density of at an applied field of $1.5-6.2\times10^{-7}A/cm^2$ MV/cm, probably due to the stoichiometry of the films.

Preparation of Anion Exchange Membranes of Cross-linked Poly((vinylbenzyl)trimethylammonium chloride-2-hydroxyethyl methacrylate)/Poly(vinyl alcohol) (가교결합한 Poly((vinylbenzyl)trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) 음이온 교환막 제조)

  • Kim, Mi-Yang;Kim, Kwang-Je;Kang, Ho
    • Applied Chemistry for Engineering
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    • v.21 no.6
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    • pp.621-626
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    • 2010
  • Anion exchange membranes can be used for reverse electrodialysis for electric energy generation, and capacitive deionization for water purification, as well as electrodialysis for desalination. In this study, anion exchange membranes of poly((vinylbenzyl) trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) were prepared through the polymerization of (vinylbenzyl)trimethylammonium chloride and 2-hydroxyethyl methacrylate in aqueous poly(vinyl alcohol) solutions, esterification with glutaric acid, and cross-linking reaction with glutaraldehyde. We investigated electrochemical properties for the anion exchange membranes prepared according to experimental conditions. Ion exchange capacity and electrical resistance for the membranes were changed with a variation in the monomer ratio in polymerization. Water uptake and conductivity for the membranes decreased with an increase in the content of glutaric acid in esterification. The change in the time of crosslinking reaction with the formed film and glutaraldehyde affected electrochemical properties such as water uptake, conductivity, or transport number for the membranes. Chronopotentiometry and limiting current density for the anion exchange membranes prepared were measured.

Diffusion Coefficient of Ag(I) ion in the Concentrated Nitric Acid Solution (고농도 질산용액에서 Ag(I) 이온의 확산계수 측정)

  • Park Sang Yoon;Choi Wang Kyu;Lee Kune Woo;Moon Jei Kwon;Oh Won Zin
    • Journal of the Korean Electrochemical Society
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    • v.2 no.2
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    • pp.93-97
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    • 1999
  • From the anodic peak currents of cyclic voltammograms for Ag(I)/Ag(II) couple obtained with the variation of nitric acid concentration, Ag(I) concentration and solution temperature at a Pt electrode in concentrated nitric acid solutions, the diffusion coefficients of Ag(I) ion were evaluated to estimate the limiting current density of Ag(II)-mediated electrochemical oxidation (MEO) process, which has been effectively used for the complete destruction of hazardous organic materials. The results showed that, due to the water decomposition reaction which occurred simultaneously with the Ag(I) ion oxidation, background subtractions for the cyclic voltammograms were required to estimate the correct peak currents. The empirical relationship for the diffusion coefficient of Ag(I) was suggested as a function of solution viscosity and temperature.

Operating parameters in electrodialysis membrane processes for removal of arsenic in groundwater (지하수내 비소제거를 위한 전기투석 막여과 운전인자 연구)

  • Choi, Su Young;Park, Keun Young;Lee, Seung Ju;Choi, Dan Bi;Park, Ki Young;Kim, Hee Jun;Kweon, Ji Hyang
    • Journal of Korean Society of Water and Wastewater
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    • v.30 no.4
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    • pp.449-457
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    • 2016
  • In this study, the effectiveness of electrodialysis in removing inorganic arsenic from groundwater was investigated. To evaluate the feasibility of the electrodialysis, operating parameters such as treatment time, feed concentration, applied voltage and superficial velocity were experimentally investigated on arsenic removal. The higher conductivity removal and arsenic removal efficiency were obtained by increasing applied voltages and operation time. An increase of salinity concentrations in arsenic polluted groundwater exerted no effects on the arsenic separation ratios. Arsenic polluted waters were successfully treated with stack voltages of 1.8 ~ 2.4 V/cell-pair to approximately 93.4% of arsenic removal. Increase flow rate in diluate cell gave positive effect to removal rate. However, increase of superficial velocity in the concentrated cell exerted no effects on either the conductivity reduction or on the separation efficiency. Hopefully, this paper will provide direction in selecting appropriate operating conditions of electrodialysis for arsenic removal.

Active Reaction Sites and Oxygen Reduction Kinetics on $La_1_{-x}Sr_xMnO_{3+\delta}$(x=0.1-0.4)/YSZ (Yttria-Stabilized Zirconia) Electrodes for Solid Oxide Fuel Cells

  • Lee, Hee Y.;Cho, Woo S.;오승모
    • Bulletin of the Korean Chemical Society
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    • v.19 no.6
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    • pp.661-666
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    • 1998
  • Active reaction sites and electrochemical O2 reduction kinetics on La_{1-x}Sr_xMnO_{3+{\delta}} (x=0.1-0.4)/YSZ (yttria-stabilized zirconia) electrodes are investigated in the temperature range of 700-900 ℃ at $Po_2=10^{-3}$-0.21 atm. Results of the steady-state polarization measurements, which are formulated into the Butler-Volmer formalism to extract transfer coefficient values, lead us to conclude that the two-electron charge transfer step to atomically adsorbed oxygen is rate-limiting. The same conclusion is drawn from the $Po_2$-dependent ac impedance measurements, where the exponent m in the relationship of $I_o$ (exchange current density) ∝ $P_{o_{2}}^m$ is analyzed. Chemical analysis is performed on the quenched Mn perovskites to estimate their oxygen stoichiometry factors (δ) at the operating temperature (700-900 ℃). Here, the observed δ turns out to become smaller as both the Sr-doping contents (x) and the measured temperature increase. A comparison between the 8 values and cathodic activity of Mn perovskites reveals that the cathodic transfer coefficients $({\alpha}_c)$ for oxygen reduction reaction are inversely proportional to δ whereas the anodic ones $({\alpha}_a)$ show the opposite trend, reflecting that the surface oxygen vacancies on Mn perovskites actively participate in the $O_2$ reduction reaction. Among the samples of x= 0.1-0.4, the manganite with x=0.4 exhibits the smallest 8 value (even negative), and consistently this electrode shows the highest ${\alpha}_c$ and the best cathodic activity for the oxygen reduction reaction.

Relationship between Squid (Todarodes pacificus) Catch by Sea Block and Marine Environment in the East Sea during 1980s and 1990s (1980-1990년대 동해에서 해구별 오징어(Todarodes pacificus) 어획량과 해양환경의 관계)

  • Kim, Yoon-Ha;Moon, Chang-Ho;Choi, Kwang-Ho;Lee, Chung-Il
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.16 no.3
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    • pp.259-268
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    • 2010
  • Data on squid catches by the Korean jig fishery in sea blocks ($30'{\times}30'$), water temperatures at depth(30m, 50m and 100m) and zooplankton biomass in the East Sea from 1980 to 1999 were analyzed to examine the mechanism of formation of the high density stock area. Japanese common squid (Todarodes pacificus) catch in the East Sea was low in 1980s, while the catch was high in 1990s. The five sea blocks (No. 76, 82, 83, 87, 88) of the southern part in the eastern coastal waters of Korea showed high levels of percentage of total catch (35.1%), whereas the four sea blocks (No. 65, 71, 72, 78) of the coastal waters of Uleung Island showed high levels of percentage of CPUE (61.2%) for 20 years. Squid catches showed monthly fluctuations according to the vertical distribution of optimum water temperature for fishing ($14^{\circ}C{\sim}19^{\circ}C$). High total catch and high CPUE area matched well with $10^{\circ}C$ isothermal lines at 100m depth indicating northern limiting of Tsushima Warm Current, and temporal and spatial change in $10^{\circ}C$ isothermal line caused the change in total catch and CPUE. Horizontal distribution of zooplankton biomass by sea block was not matched well with those of total catch and CPUE, however pattern of time-series change in total zooplankton biomass was similar to that in total squid catch.

Physical properties of Southeastern Yellow Sea Mud (SEYSM): Comparison with the East Sea and the South Sea mudbelts of Korea (황해 남동부 니질대의 물리적 성질: 동해 및 남해 니질대와의 비교)

  • Kim, Dae-Choul;Kim, Shin-Jeong;Seo, Young-Kyo;Jung, Ja-Hun;Kim, Yang-Eun;Kim, Gil-Young
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.5 no.4
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    • pp.335-345
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    • 2000
  • Physical and acoustic properties of the Southeastern Yellow Sea Mud (SEYSM) of Korea were studied by using 10 piston cores. The data were also compared with mudbelt sediments in the South Sea and the East Sea (southeastern inner shelf) of Korea. The sediments were mainly composed of homogeneous silt. Sandy mud and mud were minor components. The major source of sediment in the study area is probably the Keum River. Finegrained sediments discharged from the river are transported southward by coastal current, resulting in a gradual southward increase in porosity and a decrease in wet bulk density and sound velocity. The mean grain size especially appears to be the most important variable to determine the physical properties and velocity. The variations of physical properties with burial depth are dependent more strongly on sediment texture (especially, silt content) than compaction and/or consolidation. Correlations between the physical properties and the sediment texture show slight deviations from those of the East Sea and the South Sea of Korea in spite of similar pattern within the limiting values. This is probably due to the differences in silt contents, sedimentary environments, mineral compositions, and gas contents.

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A Techno-Economic Study of Commercial Electrochemical CO2 Reduction into Diesel Fuel and Formic Acid

  • Mustafa, Azeem;Lougou, Bachirou Guene;Shuai, Yong;Razzaq, Samia;Wang, Zhijiang;Shagdar, Enkhbayar;Zhao, Jiupeng
    • Journal of Electrochemical Science and Technology
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    • v.13 no.1
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    • pp.148-158
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    • 2022
  • The electrochemical CO2 reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO2 reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO2 obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO2) and hydrogen, while in the second scenario, direct electrochemical CO2 reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren't competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.