• Title/Summary/Keyword: Green emission

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Synthesis and Luminescence Characteristics of SrGa2S4:Eu Green Phosphor for Light Emitting Diodes by Solid-State Method (고상법을 이용한 LED용 SrGa2S4:Eu 녹색 형광체의 합성 및 발광특성)

  • Kim, Jae-Myung;Kim, Kyung-Nam;Park, Joung-Kyu;Kim, Chang-Hae;Jang, Ho-Gyeom
    • Journal of the Korean Chemical Society
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    • v.48 no.4
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    • pp.371-378
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    • 2004
  • The $SrGa_2S_4:Eu^{2+}$ green emitting phosphor has been studied as a luminous device for CRT (Cathode Ray Tube) or FED (Field Emission Display) and EL (Electroluminescence). This phosphor, also, is under noticed for LED (Lighting Emitting Diode) phosphor, which makes use of excitation characteristics of long wavelength region. The $SrGa_2S_4:Eu^{2+}$ phosphor was prepared generally conventional synthesis method using flux. However, this method needs high heat-treated temperature, long reaction time, complex process and harmful $H_2S$or $CS_2$ gas. In this works, therefore, we have synthesized $SrGa_2S_4:Eu^{2+}$ using SrS, $Ga_2S_3$, and EuS as starting materials, and the mixture gas of 5% H2/95% N2 was used to avoid the $H_2S$or $CS_2$. We investigated the luminescence characteristic of $SrGa_2S_4:Eu^{2+}$ phosphor prepared in various synthesis conditions, performed post-treatment and sieving process for application to LED.

Photoluminescent Properties of $\textrm{Zn}_2\textrm{SiO}_4$:Mn Green Phosphors Prepared by the Solution Reaction Method (액상반응법으로 제조한 $\textrm{Zn}_2\textrm{SiO}_4$:Mn 녹색 형광체의 발광특성)

  • Park, Eung-Seok;Jang, Ho-Jeong;Jo, Tae-Hwan
    • Korean Journal of Materials Research
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    • v.9 no.1
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    • pp.46-50
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    • 1999
  • $\textrm{Zn}_{2-x}\textrm{Mn}_{x}\textrm{SiO}_{4}$ green phosphors have been prepared by the solution reaction method and the photoluminescence and crystalline properties were studied as a function of both the firing temperature ($900^{\circ}C$~$1200^{\circ}C$) and the concentration of Mn activator (x=0.01~0.20). Under 147 nm and 254nm and excitation sources, the emission intensity of the phosphors was increased about 4 times increasing firing temperatures from $900^{\circ}C$ to $1200^{\circ}C$. From the XRD analysis, $\textrm{Zn}_{2}\textrm{SiO}_{4}$:Mn phosphors fired above $1100^{\circ}C$ showed willemite crystal structure. Under 147nm excitation, the maximum emission intensity was obtained at the Mn concentration of x=0.02 for $\textrm{Zn}_{2-x}\textrm{Mn}_{x}\textrm{SiO}_{4}$ phosphors fired at $1200^{\circ}C$ and the concentration quenching was occurred at the Mn concentration above x=0.10. The phosphor particles showed almost spherical shapes with the average size of around 2~3$\mu\textrm{m}$ by the SEM morphology.

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Effect of no-tillage and green manure practices on the nitrous oxide emission from cropland (농경지에서 무경운 및 녹비 투입에 따른 아산화질소 배출특성)

  • Lee, Sun-Il;Kim, Gun-Yeob;Lee, Jong-Sik;Choi, Eun-Jung
    • Korean Journal of Environmental Biology
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    • v.37 no.3
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    • pp.309-316
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    • 2019
  • Cropland is a major source of atmospheric nitrous oxide (N2O) and we need technologies in the field of agriculture that can reduce the presence of N2O. In this study, a field experiment encompassing six treatments was conducted to determine the efflux of N2O in cropland during the growing season. An experimental plot was composed of two main sectors, no-tillage (NT) and conventional tillage (CT), which were subdivided into three plots according to types of nitrogen (N) sources: CF, chemical fertilizer; HV, hairy vetch+chemical fertilizer; and RY, rye+chemical fertilizer. The cumulative N2O emissions were 179.8 mg N2O m-2 for CF-CT, 108.1 mg N2O m-2 for HV-CT, 303.5 mg N2O m-2 for RY-CT, 86.7 mg N2O m-2 for CF-NT, 73.8 mg N2O m-2 for HV-NT, and 122.7 mg N2O m-2 for RY-NT during the fallow season. The CT, HV, and RY of no-tilled soils were reduced by 51.8, 31.7 and 59.6%, respectively (p<0.001). Our results indicate that the use of no-tillage and hairy vetch practice rather than conventional tillage and chemical fertilizer practice can decrease N2O emission.

Effects of Leveler on the Trench Filling during Damascene Copper Plating (전해전착시 상감 구리 배선의 충전에 미치는 레벨러의 효과)

  • Lee, Yu-Young;Park, Young-Joon;Lee, Jae-Bong;Cho, Byung-Won
    • Journal of the Korean Electrochemical Society
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    • v.5 no.3
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    • pp.153-158
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    • 2002
  • The effects of leveler on the copper trench filling were investigated during damascene plating process. To investigate the trench filling effect with the addition of a leveler, a cross-section images of the electroplated trenches with the width of$0.37{\mu}m,\;and\;0.18{\mu}m$ were observed by field emission scanning electron microscope (FE-SEM). Polyethylene glycol(PEG), 3-mercapto-1-propanesulfonic acid and Janus Green B were used as a carrier, an accelerator and a leveler. $0.37{\mu}m$ trenches were superfilled without voids, but there was voids formation in $0.18{\mu}m$ trenches when the leveler was not added into the electrolyte. On the other hand $0.18{\mu}m$ trenches were superfilled without voids with the addition of the leveler due to the reduction growth rate of copper at protrusions and edges, which yield smooth final deposit surface. The leverer effect becomes more significant as the width of trenches becomes smaller when trenches are filed.

Cellulosic Ethanol as Renewable Alternative Fuel (신재생 대안 에너지로서의 셀룰로스 에탄올)

  • Cho, Woo-Suk;Chung, Yu-Hee;Kim, Bo-Kyung;Suh, Su-Jeoung;Koh, Wan-Soo;Choe, Sung-Hwa
    • Journal of Plant Biotechnology
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    • v.34 no.2
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    • pp.111-118
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    • 2007
  • Global warming crisis due primarily to continued green house gas emission requires impending change to renewable alternative energy than continuously depending on exhausting fossil fuels. Bioenergy including biodiesel and bioethanol are considered good alternatives because of their renewable and sustainable nature. Bioethanol is currently being produced by using sucrose from sugar beet, grain starches or lignocellulosic biomass as sources of ethanol fermentation. However, grain production requires significant amount of fossil fuel inputs during agricultural practices, which means less competitive in reducing the level of green house gas emission. By contrast, cellulosic bioethanol can use naturally-growing, not-for-food biomass as a source of ethanol fermentation. In this respect, cellulosic ethanol than grain starch ethanol is considered a more appropriate as a alternative renewable energy. However, commercialization of cellulosic ethanol depends heavily on technology development. Processes such as securing enough biomass optimized for economic processing, pretreatment technology for better access of polymer-hydrolyzing enzymes, saccharification of recalcitrant lignocellulosic materials, and simultaneous fermentation of different sugars including 6-carbon glucose as well as 5-carbon xylose or arabinose waits for greater improvement in technologies. Although it seems to be a long way to go until commercialization, it should broadly benefit farmers with novel source of income, environment with greener and reduced level of global warming, and national economy with increased energy security. Mission-oriented strategies for cellulosic ethanol development participated by government funding agency and different disciplines of sciences and technologies should certainly open up a new era of renewable energy.

Upconversion luminescence from poly-crystalline Yb3+, Er3+ co-doped NaGd(MoO4)2 by simple solid state method (Er3+, Yb3+ 이온이 동시 도핑된 NaGd(MoO4)2의 업컨버젼 분석)

  • Kang, Suk Hyun;Kang, Hyo Sang;Lee, Hee Ae;Shim, Kwang Bo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.26 no.4
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    • pp.159-163
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    • 2016
  • Up-conversion (UC) luminescence properties of polycrystalline $Er^{3+}/Yb^{3+}$ doped $NaGd(MoO_4)_2$ phosphors synthesized by a simple solid-state reaction method were investigated in detail. Used to 980 nm excitation (InfraRed area), $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ exhibited very weak red emissions near 650 and 670 nm, and very strong green UC emissions at 540 and 550 nm corresponding to the infra 4f transitions of $Er^{3+}(^4F_{9/2},\;^2H_{11/2},\;^4S_{3/2}){\rightarrow}Er^{3+}(^4I_{15/2})$. The optimum doping concentration of $Er^{3+}$, $Yb^{3+}$ for highest emission intensity was determined by XRD and PL analysis. The $Er^{3+}/Yb^{3+}$ (10.0/10.0 mol%) co-doped $NaGd(MoO_4)_2$ phosphor sample exhibited very strong shiny green emission. A possible UC mechanism for $Er^{3+}/Yb^{3+}$ co-doped $NaGd(MoO_4)_2$ depending on the pump power dependence was discussed.

A Study of the Combination Method for Earthwork Equipments Using the Environmental Loads and Costs (토공사 환경오염물질 부하량 및 공사비를 이용한 장비조합방법 연구)

  • Kang, Min-Ho;Park, Hyung-Keun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.3
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    • pp.1215-1224
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    • 2013
  • Great efforts have been made worldwide to reduce the Green House Gas (GHG) emission following the "Kyoto Protocol" declared during the United Nations Framework Convention on Climate Change in 1997. Many industries have restructured to meet the standard set by the Protocol. However, no clear guidance has been established for the purpose of reducing the GHG emission in construction industry. In addition, no significant effort has been made to conserve the energy during construction activities. For more effective energy saving in construction industry, it is essential to collect data about energy consumption, quantity of environmental emissions and costs. However, most studies on sustainable construction have been concentrated on the use of equipment, maintenance and repair works during construction due to the difficulties of collecting such data. This study suggests a method to select the most environmentally friendly equipment combination for earthwork with comparing environmental loads and costs using the database of Life Cycle Inventory in the Ministry of Knowledge Economy and Ministry of Environment of Korea.

Photoluminescent Properties of $\textrm{Zn}_{2}\textrm{SiO}_{4}$: Mn Green Phosphors doped with Ga (Ga 도핑된 $\textrm{Zn}_{2}\textrm{SiO}_{4}$: Mn 녹색 형광체의 발광특성)

  • Park, Eung-Seok;Jang, Ho-Jeong;Jo, Tae-Hwan
    • Korean Journal of Materials Research
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    • v.8 no.9
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    • pp.860-864
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    • 1998
  • We investigated the photoluminescence and the crystalline properties with Ga doping concentrations (0-12 mol%) in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}\textrm{SiO}_{4}$ green phosphors prepared by the solid state reaction. The photoluminescence was improved by a doping of Ga element in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$ phosphors which showed the highest emission intensity and good color purity in the doping concentration of x=0.08. The emission intensity of $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$(x= 0.08) phosphors was increased to 7 times with increasing the sintering temperatures from $1100^{\circ}C$ to $1400^{\circ}C$, showing the improved crystalline quality. The decay time was not affected by Ga doping concentrations with constant values around 24ms. It was found from SEM and PSA analyses that the phosphors were composed of a large number of small grains around 1-3$10\mu\textrm{m}$ with a small amounts of agglomerated particles above $10\mu\textrm{m}$.

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Optimum Delivery Frequency for Reducing Construction Logistics Cost under a Carbon Taxation (탄소세 부과시 건설 물류비용 최소화를 위한 운송빈도 최적화)

  • Park, Moon-Seo;Chun, Myung-Hee;Lee, Hyun-Soo;Hwang, Sung-Joo;Jang, Myung-Houn
    • Korean Journal of Construction Engineering and Management
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    • v.12 no.3
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    • pp.73-82
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    • 2011
  • The term 'green' has become an important way of survival for the construction industry in 21th century in accordance with the emergence of the environmental crisis due to the climatic change. Especially the policy of carbon taxation, planed to be introduced from 2012, is expected to be a considerable burden to the construction industry which has abundant carbon emission during the resource transportation due to the complexity of resources and local distribution of the construction sites. In this regard, this study shows an optimizing strategy for delivery frequency, which downsizes the net distribution costs based on the assumption that, despite of its other advantagements, the frequent small lot mode of JIT delivery would take negative effects due to the increase of costs of transportation and carbon emission once the carbon taxation policy carried out. To simulate the efficiency of the management strategies, the System Dynamics modeling has been used. The results show that the frequent small lot transportation strategy is now always efficient method to these changes, and that the frequency of transportation should be re-determinated according to the extent of the imposition of carbon tax. This study provides the conceptual frame for an efficient management of transportation system of the construction industry, showing necessity of change of the resource transportation systems through analysing JIT deliver system in accordance with the global changes in environmental economy.

Studies on the Denitrification in the Submerged Paddy Soil -II. The Denitrification Rates Upon Kinds of Applied Organic Matter and Levels of Nitrogen Fertilizer (논토양(土壤)의 탈질작용(脫窒作用)에 관(關)한 연구(硏究) -제(第)II보(報). 유기물(有機物)의 종류(種類) 및 질소시비량차이(窒素施肥量差異)가 탈질(脫窒)에 미치는 영향(影響))

  • Lee, Sang-Kyu;Kim, Seung-Hwan;Park, Jun-Kyu;An, Sang-Bae
    • Korean Journal of Soil Science and Fertilizer
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    • v.19 no.1
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    • pp.76-82
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    • 1986
  • A laboratory experiment was conducted to find out the denitrification rate upon the levels of nitrogen and source of organic matter in submerged sandy and sandy loam soil. The results obtained were sumarized as follows; 1. Evolution of nitrous oxide was increased at 1st and 10 days after incubation. And dinitrogen was increased at 1st and 30 days after incubation. Applications of green manure was enhanced the evolution of nitrous oxide ($N_2O$) and dinitrogen ($N_2$). 2. The cumulative denitrification rates at 50 days was high in Gyuam sandy loam soil (O-M: 1.52%) than that of Hamchang sandy soil (O-M: 3.81%). On the other hand, the cumulative emission of dinitrogen was high in Gyuam sandy loam soil while nitrous oxide was high in Hamchang sandy soil. The total mount of denitrification rate was high in order of green manure > rice straw > compost > control soil. 3. Increases of fertilizer nitrogen was enhanced the rate of emission of dinitrogen and nitrous oxide during the incubation time. 4. According to Michaelis-Menten kinetic equation, denitrification rates and reaction efficiency were remarkably increased by application of readily decomposable organic matter with in higher organic matter content of soil. 5. The negative relationship was observed between the evolution of dinitrogen and carbon ($CO_2+CH_4$) while the nitrous oxide with carbon was positive. 6. Under the this experiment conditions 1 mg of carbon was required for production of 4 mg N as $N_2O$ and 3 mg of N as $N_2$, respectively.

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