고정상 담체를 충진한 BER에서 HRT, 전류밀도 및 담체 충진율 변화가 질산성 질소 제거효율과 전류이용효율에 미치는 영향

황규대,이상근,성해창 대한상하수도학회 2010 상하수도학회지 Vol.24 No.4

BER at different packing ratios of bio-ring media(BRM) was tested to investigate the effect of varying hydraulic retention time (HRT) and current density on the nitrate removal and current efficiency. In the preliminary batch mode experiment of BERs, current density was applied at 2.0 A/㎡, 4.0 A/㎡, 4.8 A/㎡, which correspond to the designation of reactor #1, #2, #3, respectively. The reactor #2 showed a highest nitrate removal rate of 162.0 mg NO3--N/L/d, and the kinetics of nitrate removal rate was defined as the Zero order reaction. In the primary experiment of BERs, four BERs packed with BRM were operated in varying HRT and current, and the packing ratios of reactor #1, #2, #3 and #4 were 0%, 8%, 16%, 24%. respectively. This results of the experiments indicated that the nitrate removal rate and current efficiency were increased significantly cause of growing of autotrophic denitrification microorganisms on the surface of cathode and media by increasing of the current density and decreasing of HRT. However, The decreasing of nitrate removal rate and current efficiencies were observed in the condition of HRT of 5.25 hr and 4.8 A/㎡ of current density. With more increasing current density and decreasing of HRT, the hydrogen inhibition occurred at the surface of cathode. Moreover, nitrate removal rate by autotrophic denitrification microorganisms attached on the media surface was observed to be limited by no longer increasing dissolved hydrogen concentration of each reactor. In conclusion, the highest nitrate nitrogen removal and current efficiency could be achieved when the BER was operated at the conditions of 7 hr HRT, current density of 4.0 A/㎡, and 16% packing ratio. And it was found that the amount of nitrate removal by microorganisms attached on the surface of cathode and media (BRM) was 178.2 mg/L and 52.2 mg/L respectively. and the amount of nitrate removal per MLVSS was 0.435 g NO3--N/g MLVSS·d and 0.336 NO3--N/g MLVSS·d.

Synthesis and Magnetic Properties of Electrodeposited Cobalt-Iron-Vanadium Thin Films

Chae, Kwang-Pyo The Korean Magnetics Society 2006 Journal of Magnetics Vol.11 No.2

CoFeV thin film alloys were fabricated by electrodeposition, and the dependences of their magnetic properties on the current density were investigated using an X-ray diffractometer and a vibrating sample magnetometer. The deposited Co increased from about 45 to 60 wt.% with increasing current density until $25mA/cm^2$ whereas the deposited Fe decreased from about 55 to 40 wt.% with increasing current density until $25mA/cm^2$. The deposited V, about 2 wt.%, was independent of the current density. The current efficiencies of electrodeposition decreased linearly from about 40 to 29% with increasing current density. The X-ray diffraction measurement showed that all peaks of the CoFeV films were consistent with those of a typical Co hcp and Fe bcc mixed phase. An increase in the current density decreased the grain size and increased the lattice constant. The saturation magnetization increased from about 2.2 to 2.5 T with increasing current density. The coercivity measured in the perpendicular direction decreased from 260 to 120 Oe with increasing current density; a drastic drop of 60 Oe occurred at $5mA/cm^2$. The coercivity measured in the in-plane direction remained almost unchanged, at about 20 Oe, with increasing current density.

한계전류밀도 이상에서 전기투석공정의 운전

박진수,최재환,문승현 한국막학회 2002 멤브레인 Vol.12 No.3

이온교환막의 전압-전류곡선의 plateau length를 결정하는 변수를 다양한 NaCl 농도와 유속 하에서 연구하였다. 또한, 한계전류밀도 이상의 전류에서 전기투석공정 운전의 타당성을 검토하기 위해 다양한 전류밀도의 전원을 공급하면서 0.1 M NaCl 용액의 탈염실험을 실시하여 이온의 제거효율, 전류효율, 에너지소비량, 물 분해 현상을 측정하였다. NaCl 용액의 농도와 유속이 감소하면서 확산경계층의 두께도 함께 감소하였으며, 본 확산경계층의 두께는 plateau length와도 밀접한 관련이 있는 것으로 나타났다. 탈염실험에서 측정된 이온 제거 효율 및 전류효율은 한계전류밀도 이상에서도 한계전류밀도 이하에서의 탈염실험과 크게 차이 나지 않은 것으로 보아 한계전류밀도 이상에서도 대부분의 전류는 이온교환막 표면의 물분해에 의한 것이 아니라 막을 통한 이온의 이동에 의한 것으로 사료된다. 한계전류밀도 이상에서의 탈염운전에 대한 에너지소비량은 plateau length의 영향으로 한계전류밀도 이하에서의 탈염운전 보다 다소 높지만, 한계전류밀도 이상에서는 전류밀도의 증가에도 에너지소비량이 증가하지 않았다. 이러한 결과들은 물분해 현상이 심각하게 일어나지 않는 한 한계전류밀도 이상에서도 매우 경제적으로 전기투석 공정을 운전찬 수 있다는 것을 제시해 주는 것이다. The parameter which determines the plateau length of current-voltage curve for ion- exchange membranes was studied at various concentrations of NaCl and different flow rates. Moreover, the feasibility of the electrodialytic removal of 0.1 M NaCl solution at various current densities was tested by assessing the electrodialysis performance parameters such as salt removal efficiency, current efficiency, energy consumption and water dissociation. The diffusion boundary layer (DBL) thickness decreased with the NaCl concentration and flow rate of fled solution and it was observed that the plateau length of current-voltage curves was related with the DBL thickness. The removal efficiency and current efficiency were not affected significantly by the current densities even at the overlimiting current region indicating that most current were passed by electrolyte, and water dissociations are not responsible for the overlimiting current. Energy consumption increased when the current density supplied exceeded the limiting current density (LCD) values, because additional energy was necessary to overcome the plateau potential. Beyond the LCD values the energy consumption required to get a certain removal efficiency was not affected by the current density applied. The result suggests that it is allowed to operate electrodialysis processes at as high as possible current density unless water-splitting does not occur.

다층 진단 모델에 의한 광양만의 잔차류 수치 실험

추효상,이병걸,이규형 한국환경과학회 2002 한국환경과학회지 Vol.11 No.1

In order to estimate the quantitative roles of the tide induced residual currents, densisy currents and wind driven currents on the residual currents in Kwangynag Bay Korea, numerical experiments with a diagnostic multi-level model were carried out. Density currents were calculated from the temperature and salinity data observed in January, May, August and November 1998. Anti-clockwise circulations are formed at the western inner part of the bay, the location from the east of Myodo Is. to the south of POSCO Co. and the place between Yeosu peninsula and Namhae Is. from the calculation results of the tide induced residual currents. Velocities of the density currents are less than 3㎝/s at the western inner part of the bay and about 5㎝/s at the southern entrance of the bay. Density currents get strong in summer and weak in autumn. Wind driven currents at the surface layer flow in the directions of the given winds which are the daily mean winds when the temperature and salinity observations are carried out. In the middle and lower layers, however the wind driven currents flow in the opposite direction to the surface currents as supplementary currents. The surface wind driven currents are greater than the tide induced residual currents or the density currents. The calculated residual currents including the tide induced residual currents, density currents and wind driven currents agree with the results of the current observations approximately. In the Bay, the wind driven currents affect on the residual currents greatestly and tide induced residual currents and density currents do in the second place and the third place.

ORIGINAL ARTICLE : Three-Dimensional Numerical Simulation of Intrusive Density Currents

( Sang Do An ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.7

Density currents have been easily observed in environmental flows, for instance turbidity currents and pollutant plumes in the oceans and rivers. In this study, we explored the propagation dynamics of density currents using the FLOW-3D computational fluid dynamics code. The renormalization group (RNG) κ-ε scheme, a turbulence numerical technique, is employed in a Reynold-averaged Navier-Stokes framework (RANS). The numerical simulations focused on two different types of intrusive density flows: (1) propagating into a two-layer ambient fluid; (2) propagating into a linearly stratified fluid. In the study of intrusive density flows into a two-layer ambient fluid, intrusive speeds were compared with laboratory experiments and analytical solutions. The numerical model shows good quantitative agreement for predicting propagation speed of the density currents. We also numerically reproduced the effect of the ratio of current depth to the overall depth of fluid. The numerical model provided excellent agreement with the analytical values. It was also clearly demonstrated that RNG κ-ε scheme within RANS framework is able to accurately simulate the dynamics of density currents. Simulations intruding into a continuously stratified fluid with the various buoyancy frequencies are carried out. These simulations demonstrate that three different propagation patterns can be developed according to the value of hn//H: (1) underflows developed with hn//H=0 ; (2) overflows developed when hn//H=1 ; (3) intrusive interflow occurred with the condition of 0<hn//H<1.

구리 박막의 표면형상과 물성에 대한 전류밀도 영향

우태규,박일송,정광희,설경원,Woo, Tae-Gyu,Park, Il-Song,Jung, Kwang-Hee,Seol, Kyeong-Won 한국재료학회 2010 한국재료학회지 Vol.20 No.10

This study examined the effect of current density on the surface morphology and physical properties of copper plated on a polyimide (PI) film. The morphology, crystal structure, and electric characteristics of the electrodeposited copper foil were examined by scanning electron microscopy, X-ray diffraction, and a four-point probe, respectively. The surface roughness, crystal growth orientation and resistivity was controlled using current density. Large particles were observed on the surface of the copper layer electroplated onto a current density of 25 mA/$cm^2$. However, a uniform surface and lower resistivity were obtained with a current density of 10 mA/$cm^2$. One of the important properties of FCCL is the flexibility of the copper foil. High flexibility of FCCL was obtained at a low current density rather than a high current density. Moreover, a reasonable current density is 20 mA/$cm^2$ considering the productivity and mechanical properties of copper foil.

Leakage flux, Leaked voltage, Leaked current, Magnetic flux density, Surface leakage

Chung Hyeok Kim,Tag-Yong Kim,Yong-Cheul Oh 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.3

Current research about voltage leakage involves investigation of the effects of leaked voltage and current on humans through simulated environments and dummies. Electrocution results from leaked current when electricity flows through the body as a result of potential difference. Research that analyzes actual electrocution is insufficient because of the danger from leaked voltage present in the leakage area. This thesis analyzes magnetic flux density from current around a leak to investigate the distribution of current. The authors used a simulated environment to investigate electrocution accidents that frequently occur during floods through leakage along metal surfaces, and evaluated the distribution of leaked magnetic flux. Current research about voltage leakage involves investigation of the effects of leaked voltage and current on humans through simulated environments and dummies. Electrocution results from leaked current when electricity flows through the body as a result of potential difference. Research that analyzes actual electrocution is insufficient because of the danger from leaked voltage present in the leakage area. This thesis analyzes magnetic flux density from current around a leak to investigate the distribution of current. The authors used a simulated environment to investigate electrocution accidents that frequently occur during floods through leakage along metal surfaces, and evaluated the distribution of leaked magnetic flux.

Effects of Current Wave Forms and Current Densities on the Electroplated Cu Interconnection in Damascene Plating

Lee, Yu Yong,Park, Young Joon,Cho, B. W.,Lee, Jae-Bong 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.1

Effects of three different types of current waveforms and current densities on damascene copper line filling capability were investigated. The electroplating solution developed for printed circuit board (PCB) was used for Damascene plating. Three different types of current wave forms i.e. direct current (DC), Pulsed current, and periodic (PR) current methods were chosen for electroplating with the variation of current densities. The cross-section profiles of deposited wafers were analyzed by Field Emission Scanning Electron Microscope (FE-SEM). Trenches were successfully superfilled without void for Cu lines with 0.4 and 0.8m width according to each current waveform. Each current waveform was optimized with the proper current density values. The critical causes for the center and the sidewall void formations were investigated. Copper plating profiles due to DC current waveform showed center void in the final stage of plating because the copper deposition on the trench top comer was faster than those inside of trench. Oh the contrary, Pulsed or PR current methods tend to result in center voids due to the faster deposition on the sidewall. Sidewall void formation could be attributed to the localized corrosion of copper seed layers due to long immersion of the wafer in the electrolyte at zero current state before plating.

Electromigration에 의한 Sn-0.7Cu 솔더 금속간화합물 성장 예측

허민혁 ( Min-hyeok Heo ),강남현 ( Namhyun Kang ),박성훈 ( Seonghun Park ),김준기 ( Jun-ki Kim ),홍원식 ( Won Sik Hong ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.12

The reliability of printed circuit boards (PCB) has emerged as a critical concern as the size of solder bump decreases and current density to solder bump increases by fine pitch formation. The main failure mode of solder bumps is open-circuits due to void formation as intermetallic compounds (IMC) grow, mainly due to electromigration. This study modeled IMC growth by electromigration in Sn-0.7Cu solder bumps. The IMC produced in the reflow process grew again significantly due to electromigration upon application of electric current. The thickness of the IMC under electromigration increased as the current increased from 1 A (current density: 1.3 × 104 A/cm2) to 1.5 A (current density: 1.9 × 104 A/cm2). For the current density applied in the study, IMC growth of Cu6Sn5 was faster than that of Cu3Sn. The Nernst-Einstein relation was used to model the IMC growth induced by electromigration. The modeling results of Cu3Sn and Cu6Sn5 thickness showed good agreement with the experimental observations of IMC growth under electromigration. Specifically, a good prediction for Cu3Sn growth was derived for the current density of 1.3 × 104 A/cm2. However, the modeling values of 1.9 × 104 A/cm2 and Cu6Sn5 thickness showed a minor difference as compared with the experimental IMC thickness results. As the current density increased from 1.3 × 104 A/cm2 to 1.9 × 104 A/cm2, the solder bump probably evolved under heat generation, and the further effects of aging and thermomigration should be incorporated in the IMC growth. †(Received April 7, 2016; Accepted June 17, 2016)

Extraction of chloride from chloride contaminated concrete through electrochemical method using different anodes

Saraswathy, Velu,Lee, Han-Seung,Karthick, Subbiah,Kwon, Seung-Jun Elsevier 2018 Construction and Building Materials Vol.158 No.-

<P><B>Abstract</B></P> <P>Electrochemical chloride removal is one of the superior healing methods for chloride affected reinforced (RC) concrete structures. In the present study, the effect of electrochemical chloride removal (ECR) of chloride contaminated concrete consisting of embedded rebar in corroded condition was assessed by measuring the corrosion rate and rebar potential after the ECR treatment at a current density of 0.5, 1.0 and 2.0 mA/m<SUP>2</SUP> and by using three types of anodes namely, TiSA, SSA and, CCPA. Here, ‘current ON’ (ON<SUB>C</SUB>) and ‘current OFF’ (OFF<SUB>C</SUB>) method was adopted to obtain an efficient and uniform ECR throughout the specimen. From the results, it is found that the increase in current density (1.0 and 2.0 A/m<SUP>2</SUP>) increases the chloride removal efficiency. However, the corrosion rate of the rebar was increased at higher current densities and some damage on the CCPA anode material was noticed due to the hydrogen gas evolution in the rebar. It is found that the CCPA is more stable and the chloride removal efficiency was improved at 0.5 A/m<SUP>2</SUP> current density and hence it is suitable for long-time application of ECR process under ON<SUB>C</SUB> and OFF<SUB>C</SUB> method. This approach allows the easier passage of chloride ions from the cathode to the anode and the current OFF<SUB>C</SUB> period allows the system to re-establish the equilibrium between the anode and cathode. From this study, it was found that the ‘‘ON<SUB>C</SUB> and OFF<SUB>C</SUB> method’’ increases the chloride removal efficiency and thereby preventing the rebar from corrosion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ECR process development by using three different anodes and current densities. </LI> <LI> ECR process was carried out under laboratory and field exposed concretes. </LI> <LI> The CCPA is stable at 0.5 A/m<SUP>2</SUP> and suitable for long-time application. </LI> <LI> The higher current density is not suitable for continuous ECR process in all anodes. </LI> <LI> ON<SUB>C</SUB> and OFF<SUB>C</SUB> method increases the chloride removal efficiency. </LI> </UL> </P>