용접흄 충 금속함량 변화에 관한 연구

윤충식,박동욱,박두용 한국환경보건학회 2002 한국환경보건학회지 Vol.28 No.2

Concentration of welding fumes and their components is known to be hazardous to welder and adjacent worker. To determine the generation rates of metals in fumes, $CO_2$ flux cored arc welding on stainless steel was performed in well designed fume collection chamber. Variables were different products of flux cored wire(2 domestic products and 4 foreign products) and input energy(low-, optimal- , high input energy). Mass of welding fumes was determined by gravimetric method(NIOSH 0500 method), and 17 metals were analysed by inductively coupled plasm-atomic emission spectroscopy(NIOSH 7300 method). Flux cored wire tube and flux were analysed by scanning electron microscopy to determine their metal composition. 17 metals were classified by their generation rates. Generation rates of iron, manganese, potassium and sodium were all above 50mg/min at optimal input energy level. Generation rates of chromium and amorphous silica were 25~50mg/min. At 1~25mg/min level, nickel, titanium, molybdenum, and aluminum were included. Copper, zinc, calcium, lead, magnesium, lithium, and cobalt were generated below 1 mg/min. Generation rates of metal components in fumes were influenced by input energy, types of flux cored wire. Flux cored wire was consisted of outer shell tube and inner flux. Iron, chromium, and nickel were the major components of outer tube. Flux contained iron, chromium, nickel, potassium, sodium, silica, and manganese. The use of flux cored wire can increase the hazards by increasing the amounts of fumes formed relative to that of solid wire. The reason might be the direct transfer of elements from the flux, since the flux is fine power. Ratio of metals to the fume of flux cored wire was lower than that of solid wire because non-metal components of flux were transferred. Total metal content of fumes in flux cored arc welding was 47.4(24.3~57.2) percent that is much lower than that of solid wire, 75.9 percent. We found that generation rates of iron, manganese, chromium and nickel, all well known to cause work related disease to welder, increased more rapidly with increasing input energy than those of fumes. To reduce worker exposure to fumes and hazardous component at source, further research is needed to develop new welding filler materials that decrease both the amount of fumes and hazardous components.

대전지역 자연환경림 관리 및 기능평가를 위한 물질순환 모델화

장관순(Gwan-Soon Jang),정헌준(Heon-Jun Jeong) 한국환경관리학회 2006 環境管理學會誌 Vol.12 No.1

대전지역에서 생물지화학적 물질순환 관점으로 대기오염물질이 생태계로 유입되는 강우(WD)로부터 시작하여 삼림수관으로 통과하는 임내우(TF)와 수간류(SF) 그리고 토양배출수(DS)로 거동하는 이온 flux를 측정하여 산성강하 물질에 대한 삼림의 산 정화능력을 평가하였다. 평가는 H?와 양이온 flux를 주요 인자로 취급하였고, 두개의 삼림지역에서 2002년 4월부터 12월까지 조사가 이루어졌다. 조사 기간동안, 활엽수림지역에서 H? flux는 WD가 0.1kmolc h?¹, TF+SF로는 0.03 이었으며, 양이온 flux는 WD가 1.96 kmolc ha?¹ 그리고 TF+SF로는 3.36으로 측정되어 WD로부터 유입된 H?는 수관을 통과하면서 0.07 kmolc ha?¹이 소비되었다. 반면에 수관으로부터 용탈되어 나온 양이온은 1.40kmolc ha?¹에 해당되었다. 침엽수림지역에서 H?의 유입량은 1.1 kmolc ha?¹, TF+SF로는 0.09로 측정되었고, 수관에 의한 H? 소비는 0.01 kmolc h?¹로서 활엽수림보다 약 7배 낮았다. 양이온 flux는 유입량이 2.05 kmolc h?¹, TF+SF에서는 2.93, 그리고 수관으로부터 용탈은 0.89 kmolc ha?¹로 활엽수림보다 낮았다. DS에 대한 양이온 flux는 침엽 수림지역에서 3.41kmolc ha?¹ 그리고 활엽수림지역에서 2.16으로 이들 지역에서 유입량 1.96~2.05 kmolc ha?¹보다 배출량이 많아 양이온 flux 수지는 모두 음(-)의 균형을 나타내고 있었다. 조사지역에서 보이는 있는 음(-)의 물질수지는 영양염류가 토양에 축적되는 것보다 토양으로부터 유실되는 양이 더 많아 산성강하물에 의한 토양산성화를 방지하고 토양 양료보전을 위한 노력이 필요함을 의미한다. To verify acid neutralization capacity against atmospheric deposition in two forest ecosystem, Taejeon, biogeochemical proton and base cation fluxes were estimated using data on wet deposition(WD), throughfall(TF), stemflow(SF), and discharge from soils(DS) from April to December 2002. In deciduous ecosystem during investigation period, proton flux was 0.1 kmolc ha?¹ for WD, 0.03 for TF+SF, and base cation flux was 1.96 kmolc ha?¹ for WD, 3.36 for TF+SF, indicating that atmospheric acid input was neutralized through forest canopy. In deciduous canopy proton consumption was 0.07 kmolc ha?¹ and net canopy leaching of base cation was 1.40 kmolc ha?¹. In coniferous ecosystem, proton flux was kmolc ha?¹ for WD, 0.09 for TF+SF and base cation flux was 2.05 kmolc ha?¹ for WD, 2.93 for TF+SF. Proton consumption in coniferous canopy appeared 7 times lower than one in deciduous canopy and net canopy leaching of base cation was 0.89 kmolc ha?¹, indicating that acid neutralization capacity for atmospheric acid input in two forest ecosystem excelled in decidous ecosystem. DS fluxes in deciduous and in coniferous were 3.4 1kmolc ha?¹ and 2.16 kmolc ha?¹, respectively and base cation budgets in two ecosystem showed negative balance of loss nutrient element from soil.

Heat flux partitioning analysis of pool boiling on micro structured surface using infrared visualization

Kim, S.H.,Lee, G.C.,Kang, J.Y.,Moriyama, K.,Park, H.S.,Kim, M.H. Pergamon Press ; Elsevier Science Ltd 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.102 No.-

We study a heat flux partitioning analysis of nucleate pool boiling on microstructured surface through infrared visualization technique. A heat flux partitioning analysis of the nucleate pool boiling consists of three kinds of heat flux mechanisms; convective, quenching and evaporative heat flux. It is importance of understanding the dominance among those heat flux mechanisms to fundamental study of the nucleate boiling heat transfer, but it is not clearly figured out. In this study, directly measuring the boiling parameters; bubble departure size, bubble releasing frequency, nucleation site density and bubble growth time through the infrared visualization technique, a nucleate boiling heat flux portioning analysis on pool boiling has been carried out. The experimental results indicate that sum of the three heat flux partitions from the measured boiling parameters shows good agreement with the experimentally given total heat flux. In addition, the quenching heat flux and evaporative heat flux becomes dominant at high heat flux regime by numerous bubble generation and fast bubble growth. On the microstructured surface, the increased heating surface area by the roughness ratio intactly contributes the heat transfer performance enhancement, and the area increase effect have to be reflected on the heat flux partitioning calculation. Although there are still many arguments of the heat flux portioning model analysis on pool boiling heat transfer from literatures and the methodological limitation due to the chaotic boiling phenomena, this study gives good inspiration and understanding of the boiling heat transfer mechanism and the importance of each heat transfer mechanism.

Critical flux-based membrane fouling control of forward osmosis: Behavior, sustainability, and reversibility

Nguyen, Thanh-Tin,Kook, Seungho,Lee, Chulmin,Field, Robert W.,Kim, In S. Elsevier 2019 Journal of membrane science Vol.570 No.-

<P><B>Abstract</B></P> <P>Membrane fouling is closely related to the concept of critical flux. Therefore, a fouling control strategy for forward osmosis (FO) membranes that is based on the critical flux is necessary. This study systematically investigated the critical flux behavior of FO membranes (CTA and PA-TFC) in the short-term using a stepping method (draw solution (DS) concentration stepping). In addition, to test the reliability of this method, long-term experiments were conducted to evaluate the influences of operational critical flux on the fouling behavior (sustainable operation and fouling reversibility/irreversibility), thereby determining the critical flux for reversibility. Our results showed that the DS concentration stepping could be applied for critical flux determination in FO. Both membranes exhibited higher critical flux values for alginate fouling compared to other single foulants such as colloidal silica or gypsum. The values were 15.9 LMH for a cellulose triacetate membrane (CTA) and 20.5 LMH for the polyamide thin-film composite (PA-TFC). Whilst these values should be adequate in FO applications they were determined for single foulants. The presence of multispecies of foulants caused a significant decline in the critical flux values. This study found 5.4 LMH for the CTA membrane and 8.3 LMH for the PA-TFC membrane for the combined foulants of alginate + gypsum. This indicates that the critical flux behavior in FO was dependent on the foulant type and membrane type. Importantly, the high restoration of water flux was achieved with the PA-TFC membrane at an operation either close to critical flux (92–98%) or below critical flux (98–100%) (i.e., with negligible irreversible fouling). The critical fluxes for reversibility obtained in this study will aid the efficient operation of practical FO processes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Draw Solution stepping method was used to determine the critical flux value. </LI> <LI> Critical flux behavior in FO was dependent on foulants and membrane types. </LI> <LI> Plant operation below the critical flux is vital for the minimization of chemical cleaning. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

보성 농업지역에서의 장기간 플럭스 특성 분석

이영태,황성은,김병택,김기훈 한국기상학회 2024 대기 Vol.34 No.1

In this paper, Annual flux variations in the Boseong Tall Tower (BTT) from 2016 to 2020 were analyzed using data from three levels (2.5 m, 60 m, and 300 m). BTT was installed in Boseong-gun, Jeollanam-do in February 2014 and continued to conduct energy exchange observations such as CO2, sensible heat, and latent heat using the eddy covariance method until March 2023. The BTT was located in a very flat and uniform paddy field, and flux observations were conducted at four levels: 2.5 m, 60 m, 140 m, and 300 m above ground. Surface energy balance was confirmed from observed data of net radiation flux, soil heat flux, sensible heat flux, and latent heat flux. Additionally, 2.5 m height surface fluxes, which are most influenced by agricultural land, were compared with data from Local Data Assimilation and Prediction System (LDAPS) of the Korea Meteorological Administration to evaluate the accuracy of LDAPS flux data. The correlation coefficient between LDAPS flux data and observed values was 0.95 or higher. Excluding summer latent heat flux data, there was a general tendency for LDAPS data to be higher than observed values. The footprint areas estimated below 60 m height mainly covered agricultural land, and flux observations at 2.5 m and 60 m heights showed typical agricultural characteristics. In contrast, the footprint estimated at 300 m height did not show agricultural characteristics, indicating that observations at this height encompassed a wide range, including mountains, sea, and roads. The analysis results of long-term flux observations can contribute to understanding the energy and carbon dioxide fluxes in agricultural fields. Furthermore, these results can be utilized as essential data for validating and improving numerical models related to such fluxes.

분리된 삼상 자속구속형 전류제한기와 일체화된 삼상 자속구속형 전류제한기의 전류제한 특성 비교

두승규,두호익,김민주,박충렬,김용진,이동혁,한병성,Doo, Seung-Gyu,Du, Ho-Ik,Kim, Min-Ju,Park, Chung-Ryul,Kim, Yong-Jin,Lee, Dong-Hyeok,Han, Byoung-Sung 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.8

We investigate the comparison of fault current characteristics between the separates three-phase flux-lock type superconducting fault current limiter(SFCL) and integrated three-phase flux-lock type superconducting fault current limiter(SFCL). The single-phase flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil on an iron core and superconducting elements are connected to secondary coil in series. Superconducting elements are used by the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. But the integrated three-phase flux-lock type SFCL consists of three-phase flux-reactors wound on an iron core. Flux-reactor consists of the same turn's ratio between coil 1 and coil 2 for each single phase. To compare the current limiting characteristics of the separated three-phase flux-lock type SFCL and integrated three-phase flux-lock type SFCL, the short circuit experiments are carried out fault condition such as the single line-to-ground fault. The experimental result shows that fault current limiting characteristic of the separated three-phase flux-lock type SFCL was better than integrated three-phase flux-lock type SFCL. And the integrated three-phase flux-lock type SFCL has an effect on sound phase.

Radiative Heat Transfer Behavior of Mold Fluxes for Casting Low and Medium Carbon Steels

Wang, Wanlin,Gu, Kezhuan,Zhou, Lejun,Ma, Fanjun,Sohn, Il,Min, Dong Joon,Matsuura, Hiroyuki,Tsukihashi, Fumitaka The Iron and Steel Institute of Japan 2011 ISIJ international Vol.51 No.11

<P>An investigation was carried out to study the radiative heat transfer behavior of two typical mold fluxes for casting low (Flux1) and medium (Flux2) carbon steels. By using an infrared radiation emitter, a radiative heat flux was applied to a copper mold covered with solid mold flux disk to simulate the heat transfer phenomena in continuous casting. The effective thermal conductivities were determined by measuring the temperature gradient in the copper mold system. It was found that the solid crystalline mold Flux2 for casting medium carbon steel has a better capability to transfer heat than that of solid crystalline Flux1, while their glassy fluxes behave similar capability. The DHTT (Double Hot Thermocouple Technique) was employed in this paper to study the heat transfer capability of the crystalline mold fluxes. DHTT measurements suggested that the thermal diffusivity of crystalline sample of Flux2 is higher than that of Flux1. The XRD and SEM results were indicated that the precipitated crystalline phase for Flux1 is only granular cuspidine, Ca<SUB>4</SUB>Si<SUB>2</SUB>O<SUB>7</SUB>F<SUB>2</SUB>, while those for Flux2 are consisted of dendritic cuspidine, Ca<SUB>4</SUB>Si<SUB>2</SUB>O<SUB>7</SUB>F<SUB>2</SUB> and gehlenite, Ca<SUB>2</SUB>Al<SUB>2</SUB>SiO<SUB>7</SUB>.</P>

Effects of Flux Composition on the Element Transfer and Mechanical Properties of Weld Metal in Submerged Arc Welding

방국수,박찬,정홍철,이종봉 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.3

Submerged arc welding was performed using metal-cored wires and fluxes with different compositions. The effects of wire/flux combination on the chemical composition, tensile strength, and impact toughness of the weld metal were investigated and interpreted in terms of element transfer between the slag and the weld metal, i.e., △ quantity. Both carbon and manganese show negative △ quantity in most combinations, indicating the transfer of the elements from the weld metal to the slag during welding. The amount of transfer, however, is different depending on the flux composition. More basic fluxes yield less negative △C and △Mn through the reduction of oxygen content in the weld metal and presumably higher Mn activity in the slag, respectively. The transfer of silicon, however, is influenced by Al2O3, TiO2 and ZrO2 contents in the flux. △Si becomes less negative and reaches a positive value of 0.044 as the oxides contents increase. This is because Al, Ti, and Zr could replace Si in the SiO2 network, leaving more Si free to transfer from the slag to the weld metal. Accordingly, the Pcm index of weld metals calculated from chemical compositions varies from 0.153 to 0.196 depending on the wire/flux combination, and it almost has a linear relationship with the tensile strength of the weld metal. Submerged arc welding was performed using metal-cored wires and fluxes with different compositions. The effects of wire/flux combination on the chemical composition, tensile strength, and impact toughness of the weld metal were investigated and interpreted in terms of element transfer between the slag and the weld metal, i.e., △ quantity. Both carbon and manganese show negative △ quantity in most combinations, indicating the transfer of the elements from the weld metal to the slag during welding. The amount of transfer, however, is different depending on the flux composition. More basic fluxes yield less negative △C and △Mn through the reduction of oxygen content in the weld metal and presumably higher Mn activity in the slag, respectively. The transfer of silicon, however, is influenced by Al2O3, TiO2 and ZrO2 contents in the flux. △Si becomes less negative and reaches a positive value of 0.044 as the oxides contents increase. This is because Al, Ti, and Zr could replace Si in the SiO2 network, leaving more Si free to transfer from the slag to the weld metal. Accordingly, the Pcm index of weld metals calculated from chemical compositions varies from 0.153 to 0.196 depending on the wire/flux combination, and it almost has a linear relationship with the tensile strength of the weld metal.

Incorporating metabolic flux ratios into constraint-based flux analysis by using artificial metabolites and converging ratio determinants

Choi, Hyung Seok,Kim, Tae Yong,Lee, Dong-Yup,Lee, Sang Yup Elsevier Science Publishers 2007 Journal of biotechnology Vol.129 No.4

<P><B>Abstract</B></P><P>One of the well-established approaches for the quantitative characterization of large-scale underdetermined metabolic network is constraint-based flux analysis, which quantifies intracellular metabolic fluxes to characterize the metabolic status. The system is typically underdetermined, and thus usually is solved by linear programming with the measured external fluxes as constraints. Thus, the intracellular flux distribution calculated may not represent the true values. <SUP>13</SUP>C-constrained flux analysis allows more accurate determination of internal fluxes, but is currently limited to relatively small metabolic networks due to the requirement of complicated mathematical formulation and limited parameters available. Here, we report a strategy of employing such partial information obtained from the <SUP>13</SUP>C-labeling experiments as additional constraints during the constraint-based flux analysis. A new methodology employing artificial metabolites and converging ratio determinants (CRDs) was developed for improving constraint-based flux analysis. The CRDs were determined based on the metabolic flux ratios obtained from <SUP>13</SUP>C-labeling experiments, and were incorporated into the mass balance equations for the artificial metabolites. These new mass balance equations were used as additional constraints during the constraint-based flux analysis with genome-scale <I>E. coli</I> metabolic model, which allowed more accurate determination of intracellular metabolic fluxes.</P>

An investigative study of enrichment reduction impact on the neutron flux in the in-core flux-trap facility of MTR research reactors

Xoubi, Ned,Darda, Sharif Abu,Soliman, Abdelfattah Y.,Abulfaraj, Tareq Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.3

Research reactors in-core experimental facilities are designed to provide the highest steady state flux for user's irradiation requirements. However, fuel conversion from highly enriched uranium (HEU) to low enriched uranium (LEU) driven by the ongoing effort to diminish proliferation risk, will impact reactor physics parameters. Preserving the reactor capability to produce the needed flux to perform its intended research functions, determines the conversion feasibility. This study investigates the neutron flux in the central experimental facility of two material test reactors (MTR), the IAEA generic10 MW benchmark reactor and the 22 MW s Egyptian Test and Research Reactor (ETRR-2). A 3D full core model with three uranium enrichment of 93%, 45%, and 20% was constructed utilizing the OpenMC particle transport Monte Carlo code. Neutronics calculations were performed for fresh fuel, the beginning of life cycle (BOL) and end of life cycle (EOL) for each of the three enrichments for both the IAEA 10 MW generic reactor and core 1/98 of the ETRR-2 reactor. Criticality calculations of the effective multiplication factor (K_eff) were executed for each of the twelve cases; results show a reasonable agreement with published benchmark values for both reactors. The thermal, epithermal and fast neutron fluxes were tallied across the core, utilizing the mesh tally capability of the code and are presented here. The axial flux in the central experimental facility was tallied at 1 cm intervals, for each of the cases; results for IAEA 10 MW show a maximum reduction of 14.32% in the thermal flux of LEU to that of the HEU, at EOL. The reduction of the thermal flux for fresh fuel was between 5.81% and 9.62%, with an average drop of 8.1%. At the BOL the thermal flux showed a larger reduction range of 6.92%-13.58% with an average drop of 10.73%. Furthermore, the fission reaction rate was calculated, results showed an increase in the peak fission rate of the LEU case compared to the HEU case. Results for the ETRR-2 reactor show an average increase of 62.31% in the thermal flux of LEU to that of the HEU due to the effect of spectrum hardening. The fission rate density increased with enrichment, resulting in 34% maximum increase in the HEU case compared to the LEU case at the assemblies surrounding the flux trap.