• Title/Summary/Keyword: Flow efficiency

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Fundamental Properties of Mortar with Magnet-Separated Converter-Slag Powder as SCM (자력 선별 전로슬래그 미분말을 결합재로 활용한 모르타르의 기초특성)

  • Beom-Soo Kim;Sun-Mi Choi;Jin-Man Kim
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.3
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    • pp.161-168
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    • 2023
  • Converter slag is a by-product generated by refining the pig iron produced into molten steel in the blast furnace, occupying about 15 % of the weight of steel production. It has a high free-CaO content that can generate expansion cracks when used for concrete aggregate. This is the main reason to make it difficult to recycle. To solve this problem, government guideline requires that converter slag has to be aged in an open yard for 90 days. However, aging can not be perfectly performed because it entails time and cost. In this study, we tried to investigate the applicability of converter slag as a cementitious material rather than an aggregate by mixing converter slag with mortar formulations. According to the EDS results of the converter slag in the experiment, we found that screening in the aggregate phase was more effective than that in the powder phase. When the particles separated by a magnet in the aggregate state were pulverized and used for concrete up to a 15 % replacement ratio, various engineering characteristics, such as flow, length change, and compressive strength, showed engineering characteristics similar to those of the control mix.

Evaluation of Bonding Performance in UHPC-based Concrete Repair Materials Considering Surface of Structure Subject to Repair (보수대상 구조 표면 상태를 고려한 UHPC 기반 콘크리트 보수재료의 부착 성능 평가)

  • Yong-Sik Yoon;Kyong-Chul Kim;Kwang-Mo Lim;Gi-Hong An;Gum-Sung Ryu;Kyung-Taek Koh
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.4
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    • pp.433-439
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    • 2023
  • In this study, the bonding performance of repair materials was evaluated on concrete repair surface to develop concrete repair materials based on UHPC (Ultra High Performance Concrete) which has high mechanical and durability performance. The ten test variables were applied considering the roughness and wet condition of the concrete surface subject to repair, the addition of polymer, and the use PP and PVA fibers in repair materials. The addition of the polymer caused a significant decrease in strength, which was thought to be due to the effect of the additional super plasticizer used to adjust workability. Also, flow was reduced by up to 13.8 % with the use of plastic-based fibers. As a result of evaluating the bond strength of the repair material considering the condition of the surface subject to repair, it was thought that in the case of using UHPC-based repair material, high bonding performance could be secured without any additional surface treatment as long as the surface of the base material was sound. In addition, UHPC-based repair materials showed high bonding performance even when the attachment surface was wet. In the future, research will be conducted on shot-crete application and gradient pouring for the development of UHPC-based repair materials, and continuous improvement in the repair material mixing property will be carried out to ensure economic efficiency and performance as a concrete structural repair material.

Approaches to Applying Social Network Analysis to the Army's Information Sharing System: A Case Study (육군 정보공유체계에 사회관계망 분석을 적용하기 위한방안: 사례 연구)

  • GunWoo Park
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.5
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    • pp.597-603
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    • 2023
  • The paradigm of military operations has evolved from platform-centric warfare to network-centric warfare and further to information-centric warfare, driven by advancements in information technology. In recent years, with the development of cutting-edge technologies such as big data, artificial intelligence, and the Internet of Things (IoT), military operations are transitioning towards knowledge-centric warfare (KCW), based on artificial intelligence. Consequently, the military places significant emphasis on integrating advanced information and communication technologies (ICT) to establish reliable C4I (Command, Control, Communication, Computer, Intelligence) systems. This research emphasizes the need to apply data mining techniques to analyze and evaluate various aspects of C4I systems, including enhancing combat capabilities, optimizing utilization in network-based environments, efficiently distributing information flow, facilitating smooth communication, and effectively implementing knowledge sharing. Data mining serves as a fundamental technology in modern big data analysis, and this study utilizes it to analyze real-world cases and propose practical strategies to maximize the efficiency of military command and control systems. The research outcomes are expected to provide valuable insights into the performance of C4I systems and reinforce knowledge-centric warfare in contemporary military operations.

Development of the Spark Torch Igniter for the 450 N-scale Methane-Oxygen Rocket Engine (450 N급 메탄-산소 로켓 엔진을 위한 스파크 토치 점화기 개발)

  • Sinyoung Park;Edam Choi;Eunjo Han;Jin Geon Kim;Dahae Lee;Eunkwang Lee;Minwoo Lee
    • Journal of Aerospace System Engineering
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    • v.18 no.1
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    • pp.53-63
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    • 2024
  • Adopting an engine igniter with high efficiency and ignition performance is essential for reliable operation of liquid rocket engines. In this study, we developed a spark torch igniter for a 450 N-scale methane-oxygen liquid rocket engine by conducting numerical analyses, igniter manufacturing and validation. Specifically, we conducted a parametric study for maximizing the enthalpy at the igniter exit, specifically by adjusting the mass flow rate, nozzle area ratio, fuel-oxidizer mixture ratio, and the igniter length-to-diameter. The heat transferred via the igniter nozzle exit was computed using 3-dimensional numerical simulations. We also manufactured and tested the igniter based on a deduced design to confirm ignition performance of the designed spark torch igniter. The igniter developed through this study could contribute to the development of practical propulsion systems such as upper-stage engines of small launch vehicles.

Shipboard Verification Test of Onboard Carbon Dioxide Capture System (OCCS) Using Sodium Hydroxide(NaOH) Solution (가성소다(NaOH) 용액을 이용한 선상 이산화탄소 포집 장치의 선박 검증시험)

  • Gwang Hyun Lee;Hyung Ju Roh;Min woo Lee;Won Kyeong Son;Jae Yeoul Jeong;Tae-Hong Kim;Byung-Tak NAM;Jae-Ik Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.61 no.1
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    • pp.51-60
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    • 2024
  • Hi Air Korea and Hanwha ocean are currently developing an Onboard Carbon dioxide Capture System (OCCS) to absorb CO2 emitted from ship's engine using a sodium hydroxide(NaOH) solution, and converting the resulting salt into a solid form through a chemical reaction with calcium oxide (CaO). The system process involves the following steps; 1)The reaction of CO2 gas absorption in water, 2)The reaction between carbonic acid (H2CO3) and NaOH solution to produce carbonate or bicarbonate, and 3)The reaction between carbonate or bicarbonate and CaO to form calcium carbonate (CaCO3). And ultimately, the solid material, CaCO3, is separated and discharged using a separator. The OCCS has been installed on an ship and the test results have confirmed significant reduction effects of CO2 in the ship's exhaust gas. A portion of the exhaust gas emitted from the engine was transferred to the OCCS using a blower. The flow rate of the transferred gas ranged from 800 to 1384 m3/hr, and the CO2 concentration in the exhaust gas was 5.1 vol% for VLSFO, 3.7 vol% for LNG and a 12 wt% NaOH solution was used. The results showed a CO2 capture efficiency of approximately 42.5 to 64.1 vol% and the CO2 capture rate approximately 48.4 to 52.2kg/hr. Additionally, to assess the impact of the discharged CaCO3on the marine ecosystem, we conducted "marine ecotoxicity test" and performed Computational Fluid Dynamics (CFD) analysis to evaluate the dispersion and dilution of the discharged effluent.

A Functional N/S-doped Carbon Electrode from a Carbonized Bagasse Activated with Water Vapor

  • Fitria Rahmawati;Ainaya Febi Amalia;Arikasuci Fitonna Ridassepri;Jun Nakamura;Younki Lee
    • Journal of Electrochemical Science and Technology
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    • v.15 no.4
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    • pp.466-475
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    • 2024
  • This research used solid waste from sugarcane production, named bagasse, as raw material for a functional carbon electrode. The bagasse was carbonized to produce carbon powder and, following activation with water vapor at 700℃. The activated carbon was doped with N and S to improve its electrochemical properties by treating it with thiourea precursor and heating it at 850℃ under nitrogen flow to produce N/S-doped carbon (NSCE). The produced carbon was then characterized to understand the specific diffraction pattern, molecular vibrations, and surface morphology. The result found that the NSCE showed two broad diffraction peaks at 23° and 43°, corresponding to [002] and [100] crystal planes following JCPDS75-1621. FTIR spectra showed some O-H, C-H, C-O, and C=C peaks. Peaks of C=N, C-N, and S-H demonstrate the presence of N/S within the NSCE. Raman analysis revealed that N/S doping caused structure defects within the single C6 layer networks, providing carbon vacancies (VC••••) because of C replacement by N (N'C) and S (S"C). Meanwhile, XPS analysis showed N/S introduction to the C network by revealing peaks at 168.26 eV and 169.55 eV, corresponding to S2p3/2 and S2p1/2, and 171.95 eV corresponds to C-SO3-C, indicating the presence of S within the thiol group attached to the carbon. Meanwhile, N1s are revealed at 402.4 eV and 405.5 eV, confirming pyrrolic nitrogen (N-5) and quaternary nitrogen (N-Q). The electrochemical analysis found that the reaction within the prepared-NSCE/NaClO4/Na was reversible, with an onset potential of 0.1 V vs. Na/Na+, explaining the intercalation and deintercalation of sodium ions. The sodium battery full cell showed an excellent battery performance with an initial charging-discharging capacity of 720 mAh g-1 and 570 mAh g-1, respectively, at 0.2C. Meanwhile, a cycling test showed the average Coulombic efficiency of 84.4% and capacity retention of 57% after 50 cycles.

Application of BASINS/WinHSPF for Pollutant Loading Estimation in Soyang Dam Watershed (소양강댐 유역의 오염부하량 산정을 위한 BASINS/WinHSPF 적용)

  • Yoon, Chun-Gyeong;Han, Jung-Yoon;Jung, Kwang-Wook;Jang, Jae-Ho
    • Korean Journal of Ecology and Environment
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    • v.40 no.2
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    • pp.201-213
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    • 2007
  • In this study, the Batter Assessment Science Integrating point and Nonpoint Sources (BASINS 3.0)/window interface to Hydrological Simulation Program-FPRTRAN (WinHSPF) was applied for assessment of Soyang Dam watershed. WinHSPF calibration was performed using monitoring data from 2000 to 2004 to simulate stream flow. Water quality (water temperature, DO, BOD, nitrate, total organic nitrogen, total nitrogen, total organic phosphorus and total phosphorus) was calibrated. Calibration results for dry-days and wet-days simulation were reasonably matched with observed data in stream flow, temperature, DO, BOD and nutrient simulation. Some deviation in the model results were caused by the lack of measured watershed data, hydraulic structure data and meteorological data. It was found that most of pollutant loading was contributed by nonpoint source pollution showing about 98.6. The WinHSPF BMPRAC was applied to evaluate the water quality improvement. These scenarios included constructed wetland for controlling nonpoint source poilution and wet detention pond. The results illustrated that reasonably reduced pollutant loadin. Overall, BASINS/WinHSPF was found to be applicable and can be a powerful tool in pollutant loading and BMP efficiency estimation from the watershed.

Studies on the Separation and Preconcentration of Metal Ions by XAD-16-[4-(2-thiazolylazo)] orcinol Chelating Resin (XAD-16-[4-(2-thiazolylazo)]orcinol 킬레이트 수지에 의한 금속이온의 분리 및 농축에 관한 연구)

  • Lee, Won;Seol, Kyung-Mi;An, Hye-Sook;Lee, Chang-Heon;Lim, Jae-Hee
    • Analytical Science and Technology
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    • v.10 no.4
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    • pp.282-290
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    • 1997
  • The sorption and desorption properties of U(VI), Th(IV), Zr(IV), Cu(II), Pb(II), Ni(II), Zn(II), Cd(II) and Mn(II) ions on XAD-16-[4-(2-thiazolylazo)orcinol] (TAO) chelating resin were studied by elution method. The effect was examined with respect to overall capacity of each metal ion, separation of mixed metal ions, flow rate and concentration of buffer solution for optimum condition of sorption. The overall capacities of some metal ions on this chelating resin were 0.35nmol U(VI)/g resin, 0.49nmol Th(IV)/g resin, 0.41nmol Cu(II)/g resin, and 0.31nmol Zr(IV)/g resin, respectively. The elution order of metal ions obtained from breakthrough capacity and overall capacity at pH 5.0 was Th(IV)>Cu(II)>U(VI)>Zr(IV)>Pb(II)>Ni(II)>Zn(II)>Mn(II)>Cd(II). The group separation of mixed metal ions was possible by increasing pH in pH range 2~5 at a flow rate of 0.28mL/min. Characteristics of desorption were investigated with desorption agents such as HNO3, HCl, HClO4, H2SO4, and Na2CO3. It was found that 2M HNO3 showed high desorption efficiency to most of metal ions except Zr(IV) ion. Also, desorption and recovery of Zr(IV) ion were successfully performed with 1M H2SO4. Recovery of trace amount of U(VI) ion from artificial sea water was over 94%. The chelating resin, XAD-16-TAO was successfully applied to group separation of rare earth metal ions from U(VI) by using 2M HNO3 as an eluent.

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Assessment of future climate and land use changes impact on hydrologic behavior in Anseong-cheon Gongdo urban-growing watershed (미래 기후변화와 토지이용변화가 안성천 공도 도시성장 유역의 수문에 미치는 영향 평가)

  • Kim, Da Rae;Lee, Yong Gwan;Lee, Ji Wan;Kim, Seong Joon
    • Journal of Korea Water Resources Association
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    • v.51 no.2
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    • pp.141-150
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    • 2018
  • The purpose of this study is to evaluate the future hydrologic behavior affected by the potential climate and land use changes in upstream of Anseong-cheon watershed (366.5km2) using SWAT. The HadGEM3-RA RCP 4.5 and 8.5 scenarios were used for 2030s (2020-2039) and 2050s (2040-2059) periods as the future climate change scenario. It was shown that maximum changes of precipitation ranged from -5.7% in 2030s to +18.5% in 2050s for RCP 4.5 scenarios and the temperature increased up to 1.8C and 2.6C in 2030s RCP 4.5 and 2050s 8.5 scenarios respectively based on baseline (1976-2005) period. The future land uses were predicted using the CLUE-s model by establishing logistic regression equation. The 2050 urban area were predicted to increase of 58.6% (29.0 to 46.0km2). The SWAT was calibrated and verified using 14 years (2002-2015) of daily streamflow with 0.86 and 0.76 Nash-Sutcliffe model efficiency (NSE) for stream flow (Q) and low flow 1/Q respectively focusing on 2 drought years (2014-2015) calibration. For future climate change only, the stream discharge showed maximum decrease of 24.2% in 2030s RCP 4.5 and turned to maximum increase of 10.9% in 2050s RCP 4.5 scenario compared with the baseline period stream discharge of 601.0 mm by the precipitation variation and gradual temperature increase. While considering both future climate and land use change, the stream discharge showed maximum decrease of 14.9% in 2030s RCP 4.5 and maximum increase of 19.5% in 2050s RCP 4.5 scenario by the urban growth and the related land use changes. The results supported that the future land use factor might be considered especially for having high potential urban growth within a watershed in the future climate change assessment.

Optimum Configuration, Filter Media Depth and Wastewater Load of Small-scale Constructed Wetlands for Treating the Hydroponic Waste Solution in Greenhouses (시설하우스 폐양액 처리를 위한 소형 인공습지의 최적 조합방법, 여재깊이 및 폐양액 부하량)

  • Park, Woo-Young;Seo, Dong-Cheol;Lim, Jong-Sir;Park, Seong-Kyu;Cho, Ju-Sik;Heo, Jong-Soo;Yoon, Hae-Suk
    • Korean Journal of Environmental Agriculture
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    • v.27 no.3
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    • pp.217-224
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    • 2008
  • To obtain optimum configuration, depth and load of constructed wetlands(CWs) for treating of hydroponic waste solution(HWS) which was produced in greenhouses, the study was conducted with 4 kinds of combined systems such as Vertical flow(VF)-Horizontal flow(HF), VF-VF, HF-VF and HF-HF CWs. In four configurations of CWs, the treatment efficiency of pollutants from HWS under depth of HF and VF beds, HWS loading and HWSs were investigated. Removal rate of pollutants under different depth of VF and HF in 2-stage hybrid CWs was in the order of 50 cm < 70 cm regardless of CWs configuration. Removal rate of pollutants under HWS loading in 2-stage hybrid CWs was in the order of $150L\;m^{-2}\;day^{-1}{\fallingdotseq}300L\;m^{-2}\;day^{-1}\;>\;450L\;m^{-2}\;day^{-1}$. The optimum depth and HWS loading were 70 cm and 300Lm2day1 in four configurations of CWs, respectively. Using this optimum condition, for various HWSs (cucumber, paprika and strawberry HWS), removal rate of pollutants in HF-HF CWs was higher than that in HF-VF CWs. Optimum configuration of 2-stage hybrid CWs for treating hydroponic waste solution in greenhouses was found out to be HF-HF CWs. Therefore, under the optimum conditions, removal rate of BOD, COD, SS, T-N and T-P in HF-HF CWs were 84, 81, 84, 51 and 93%, respectively.