• Title/Summary/Keyword: Discharge arc

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Water Supply Change Outlook for Geum River Basin Considering RCP Climate Change Scenario (RCP 기후변화 시나리오를 고려한 금강유역의 미래 용수공급 변화전망)

  • No, Sun-Hee;Jung, Kwan Sue;Park, Jin Hyeog;Ryoo, Kyong Sik
    • Journal of Korea Water Resources Association
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    • v.46 no.5
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    • pp.505-517
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    • 2013
  • In this study, water supply for Geum River Basin was calculated by regulating the future water supply of Dam with the future expected discharges. HadGEM2-AO, which is the climate change prediction model that KMA (Korea Meteorological Administration) recently introduced was used for this study. The data of weather stations within the Geum River basin was extracted with the new Greenhouse Gas RCP scenario. The runoff of Geum river basin was simulated using the ArcSWAT for the 1988~2010 period. After validating the model, the similarity of results between simulation and observation at the Yongdam Dam and Daecheong Dam was 92.25% and 95.40%, respectively, which shows a good agreement with observed data. As the result of analysis for the discharges, the discharges would increase 47.76% under the RCP4.5 scenario and 36.52% under the RCP8.5 scenario. Water balance analysis was conducted by the KModSim for predicting the water supply under the runoff variation. We analyzed the volume of water intake with national standard of water supply 95% by Dam Operation Manual. By the analysis under RCP4.5 scenario, $9.41m^3/s$, $24.82m^3/s$ of additional water supply is available on Yongdam Dam and Daecheong Dam. By the analysis under the RCP8.5 scenario, $6.48m^3/s$, $21.08m^3/s$ of additional water supply is available on Yongdam Dam and Daecheong Dam.

A Modified grid-based KIneMatic wave STOrm Runoff Model (ModKIMSTORM) (I) - Theory and Model - (격자기반 운동파 강우유출모형 KIMSTORM의 개선(I) - 이론 및 모형 -)

  • Jung, In Kyun;Lee, Mi Seon;Park, Jong Yoon;Kim, Seong Joon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.6B
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    • pp.697-707
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    • 2008
  • The grid-based KIneMatic wave STOrm Runoff Model (KIMSTORM) by Kim (1998) predicts the temporal variation and spatial distribution of overland flow, subsurface flow and stream flow in a watershed. The model programmed with C++ language on Unix operating system adopts single flowpath algorithm for water balance simulation of flow at each grid element. In this study, we attempted to improve the model by converting the code into FORTRAN 90 on MS Windows operating system and named as ModKIMSTORM. The improved functions are the addition of GAML (Green-Ampt & Mein-Larson) infiltration model, control of paddy runoff rate by flow depth and Manning's roughness coefficient, addition of baseflow layer, treatment of both spatial and point rainfall data, development of the pre- and post-processor, and development of automatic model evaluation function using five evaluation criteria (Pearson's coefficient of determination, Nash and Sutcliffe model efficiency, the deviation of runoff volume, relative error of the peak runoff rate, and absolute error of the time to peak runoff). The modified model adopts Shell Sort algorithm to enhance the computational performance. Input data formats are accepted as raster and MS Excel, and model outputs viz. soil moisture, discharge, flow depth and velocity are generated as BSQ, ASCII grid, binary grid and raster formats.

Simple one-step synthesis of carbon nanoparticles from aliphatic alcohols and n-hexane by stable solution plasma process

  • Park, Choon-Sang;Kum, Dae Sub;Kim, Jong Cheol;Shin, Jun-Goo;Kim, Hyun-Jin;Jung, Eun Young;Kim, Dong Ha;Kim, Daseulbi;Bae, Gyu Tae;Kim, Jae Young;Shin, Bhum Jae;Tae, Heung-Sik
    • Carbon letters
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    • v.28
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    • pp.31-37
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    • 2018
  • This paper examines a simple one-step and catalyst-free method for synthesizing carbon nanoparticles from aliphatic alcohols and n-hexane with linear molecule formations by using a stable solution plasma process with a bipolar pulse and an external resistor. When the external resistor is adopted, it is observed that the current spikes are dramatically decreased, which induced production of a more stable discharge. Six aliphatic linear alcohols (methanol-hexanol) containing carbon with oxygen sources are studied as possible precursors for the massive production of carbon nanoparticles. Additional study is also carried out with the use of n-hexane containing many carbons without an oxygen source in order to enhance the formation of carbon nanoparticles and to eliminate unwanted oxygen effects. The obtained carbon nanoparticles are characterized with field emission-scanning electron microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The results show that with increasing carbon ratios in alcohol content, the synthesis rate of carbon nanoparticles is increased, whereas the size of the carbon nanoparticles is decreased. Moreover, the degree of graphitization of the carbon nanoparticles synthesized from 1-hexanol and n-hexane with a high carbon (C)/oxygen (O) ratio and low or no oxygen is observed to be greater than that of the carbon nanoparticles synthesized from the corresponding materials with a low C/O ratio.

A Study on the Origin of Anomalously Low Saline Tsushima Current Water Using $^{228}Ra$ ($^{228}Ra$를 이용한 이상 저염 대마난류수의 기원 추적 연구)

  • Lee, Tong-Sup;Kim, Ki-Hyun
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.3 no.4
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    • pp.175-182
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    • 1998
  • Recently it is reported that anomalously low saline surface waters (salinity < 32) occurred at the Ulleung Basin in the East Sea-Japan Sea, during early September to November 1996. Apparent source of such a low saline watermass seems remotely linked to the Changjiang Dilute Water (CDW), which expands to the vicinity of Cheju Island during a flood season. Based on the assumption that waters passing through the Western Channel of the Korea Strait are formed by a mixing of Kuroshio Water and CDW, simplified two end-member mixing model using $^{228}Ra/^{226}Ra$ as a conservative tracer is applied to calculate the contribution of each end member for the formation of low saline surface seawater. Model calculations show CDW contributes $58{\pm}3%$ in September 1996 (S=32.17) and $10{\pm}3%$ in February 1997 (S=34.53) in the formation of surface water flowing into the Western Channel of the Korea Strait. Although results arc deduced from a simplified model with limited data, this study demonstrates that Changjiang discharge is clearly traceable to the interior of the East Sea-Japan Sea in fall season. Undergoing Three Valley Dam construction in the Changjiang River would invoke inevitable changes in the nature and discharge of CDW and its impacts on the marine environment might be significant in the northern East China Sea and even in the Ulleng Basin for coming decades.

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Growth of vertically aligned carbon nanotubes on Co-Ni alloy metal (Co-Ni 합금위에서 수직방향으로 정렬된 탄소나노튜브의 성장)

  • Lee, Cheol-Jin;Kim, Dae-Woon;Lee, Tae-Jae;Park, Jeong-Hoon;Son, Kwon-Hee;Lyu, Seung-Chul;Song, Hong-Ki;Choi, Young-Chul;Lee, Young-Hee
    • Proceedings of the KIEE Conference
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    • 1999.07d
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    • pp.1504-1507
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    • 1999
  • We have grown vertically aligned carbon nanotubes in a large area of Co-Ni codeposited Si substrates by the thermal CVD using $C_2H_2$ gas. Since the discovery of carbon nanotubes, Synthesis of carbon nanotubes for mass production has been achieved by several methods such as laser vaporization arc discharge, and pyrolysis. In particular, growth of vertically aligned nanotubes is of technological importance for applications to FED. Recently, vertically aligned carbon nanotubes have been grown on glass by PECVD Aligned carbon nanotubes can be also grown on mesoporous silica and Fe patterned porous silicon using CVD. Despite such breakthroughs in the growth, the growth mechanism of the alignment are still far from being clearly understood. Furthermore, FED has not been clearly demonstrated yet at a practical level. Here, we demonstrate that carbon nanotubes can be vertically aligned on catalyzed Si substrate when the domain density reaches a certain value. We suggest that steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically and then nanotubes are further grown by the cap growth mechanism.

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Characterization and Electrical Conductivity of Carbon-Coated Metallic (Ni, Cu, Sn) Nanocapsules

  • Wang, Dong Xing;Shah, Asif;Zhou, Lei;Zhang, Xue Feng;Liu, Chun Jing;Huang, Hao;Dong, Xing Long
    • Applied Microscopy
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    • v.45 no.4
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    • pp.236-241
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    • 2015
  • Carbon-coated Ni, Cu and Sn nanocapsules were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and a four-point probe device. All of these nanocapsules were prepared by an arc-discharge method, in which the bulk metals were evaporated under methane ($CH_4$) atmosphere. Three pure metals (Ni, Cu, Sn) were typically diverse in formation of the carbon encapsulated nanoparticles and their different mechanisms were investigated. It was indicated that a thick carbon layers formed on the surface of Ni(C) nanocapsules, whereas a thin shell of carbon with 1~2 layers covered on Cu(C) nanocapsules, and the Sn(C) nanocapsules was, in fact, a longger multi-walled carbon nanotubes partially-filled with metal Sn. As one typical magnetic/dielectric nanocomposite particles, Ni(C) nanocapsules and its counterpart of oxide-coated Ni(O) nanocapsules were compared in the electrically conductive behaviors for further applications as the electromagnetic materials.

Production of Hydrogen-Rich Gas from Methane by a Thermal Plasma Reforming (고온 플라즈마 개질에 의한 메탄으로부터 고농도 수소생산)

  • Kim, Seong-Cheon;Lim, Mun-Sup;Chun, Young-Nam
    • Journal of Hydrogen and New Energy
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    • v.17 no.4
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    • pp.362-370
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    • 2006
  • The purpose of this paper was to investigate the reforming characteristics and optimum operating condition of the plasmatron assisted $CH_4$ reforming reaction for the hydrogen-rich gas production. Also, in order to increase the hydrogen production and the methane conversion rate, parametric screening studies were conducted, in which there were the variations of the $CH_4$ flow ratio, $CO_2$ flow ratio, vapor flow ratio, mixing flow ratio and catalyst addition in reactor. High temperature plasma flame was generated by air and arc discharge. The air flow rate and input electric power were fixed 5.1 l/min and 6.4 kW, respectively. When the $CH_4$ flow ratio was 38.5%, the production of hydrogen was maximized and optimal methane conversion rate was 99.2%. Under these optimal conditions, the following synthesis gas concentrations were determined: $H_2$, 45.4%; CO, 6.9%; $CO_2$, 1.5%; and $C_2H_2$, 1.1%. The $H_2/CO$ ratio was 6.6, hydrogen yield was 78.8% and energy conversion rate was 63.6%.

Iron Oxide-Carbon Nanotube Composite for NH3 Detection (산화철-탄소나노튜브 나노복합체의 암모니아 가스센서 응용)

  • Lee, Hyundong;Kim, Dahye;Ko, DaAe;Kim, Dojin;Kim, Hyojin
    • Korean Journal of Materials Research
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    • v.26 no.4
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    • pp.187-193
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    • 2016
  • Fabrication of iron oxide/carbon nanotube composite structures for detection of ammonia gas at room temperature is reported. The iron oxide/carbon nanotube composite structures are fabricated by in situ co-arc-discharge method using a graphite source with varying numbers of iron wires inserted. The composite structures reveal higher response signals at room temperature than at high temperatures. As the number of iron wires inserted increased, the volume of carbon nanotubes and iron nanoparticles produced increased. The oxidation condition of the composite structures varied the carbon nanotube/iron oxide ratio in the structure and, consequently, the resistance of the structures and, finally, the ammonia gas sensing performance. The highest sensor performance was realized with $500^{\circ}C/2h$ oxidation heat-treatment condition, in which most of the carbon nanotubes were removed from the composite and iron oxide played the main role of ammonia sensing. The response signal level was 62% at room temperature. We also found that UV irradiation enhances the sensing response with reduced recovery time.

Improved Conductivities of SWCNT Transparent Conducting Films on PET by Spontaneous Reduction

  • Min, Hyeong-Seop;Kim, Sang-Sik;Lee, Jeon-Guk
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.10a
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    • pp.43.2-43.2
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    • 2011
  • Single-walled carbon nanotubes (SWCNT) are transparent in the visible and show conductivity comparable to copper, and are environmentally stable. SWCNT films have high flexibility, conductivity and transparency approaching that indium tin oxide (ITO), and can be prepared inexpensively without vacuum equipment. Transparent conducting Films (TCF) of SWCNTs has the potential to replace conventional transparent conducting oxides (TCO, e.g. ITO) in a wide variety of optoelectronic devices, energy conversion and photovoltaic industry. However, the sheet resistance of SWCNT films is still higher than ITO films. A decreased in the resistivity of SWCNT-TCFs would be beneficial for such an application. We fabricated SWCNT sheet with $KAuBr_4$ on PET substrate. Arc-discharge SWCNTs were dispersed in deionized water by adding sodum dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWCNT was spray-coated on PET substrate and dried on a hotplate at $100^{\circ}C$. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then treated with AuBr4-, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. $HNO_3$ treated SWCNT films with Au nano-particles have the lowest 61 ${\Omega}$/< sheet resistance in the 80% transmittance. Sheet resistance was decreased due to the increase of the hole concentration at the washed SWCNT surface by p-type doping of $AuBr_4{^-}$.

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GaAs-Carbon Nanotubes Nanocomposite: Synthesis and Field-Emission Property (갈륨비소-탄소나노튜브 복합체 제작과 전계방출특성)

  • Lim, Hyun-Chul;Chandrasekar, P.V.;Chang, Dong-Mi;Ahn, Se-Yong;Jung, Hyuk;Kim, Do-Jin
    • Korean Journal of Materials Research
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    • v.20 no.4
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    • pp.199-203
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    • 2010
  • Hybridization of semiconductor materials with carbon nanotubes (CNTs) is a recent field of interest in which new nanodevice fabrication and applications are expected. In this work, nanowire type GaAs structures are synthesized on porous single-wall carbon nanotubes (SWCNTs) as templates using the molecular beam epitaxy (MBE) technique. The field emission properties of the as-synthesized products were investigated to suggest their potential applications as cold electron sources, as well. The SWCNT template was synthesized by the arc-discharge method. SWCNT samples were heat-treated at $400^{\circ}C$ under an $N_2/O_2$ atmosphere to remove amorphous carbon. After heat treatment, GaAs was grown on the SWCNT template. The growth conditions of the GaAs in the MBE system were set by changing the growth temperatures from $400^{\circ}C$ to $600^{\circ}C$. The morphology of the GaAs synthesized on the SWCNTs strongly depends on the substrate temperature. Namely, nano-crystalline beads of GaAs are formed on the CNTs under $500^{\circ}C$, while nanowire structures begin to form on the beads above $600^{\circ}C$. The crystal qualities of GaAs and SWCNT were examined by X-ray diffraction and Raman spectra. The field emission properties of the synthesized GaAs nanowires were also investigated and a low turn-on field of $2.0\;V/{\mu}m$ was achieved. But, the turn-on field was increased in the second and third measurements. It is thought that arsenic atoms were evaporated during the measurement of the field emission.