Pesticides and herbicides

Chung, Kyuhyuck,Starrett, Steve,Chung, Yunchul,Ro, Kyoung S. 성균관대학교 약학연구소 1998 成均藥硏論文集 Vol.10 No.1

MONITORING Wood and Anthony (1997) investigated herbicide leaching using a series of natural springs draining small surficial aquifers. The herbicides were detected at the level of nanograms per liter. Monitoring herbicides in Recharge Lake in York, Nebraska, was performad (Ma and Spalding, 1997). Herbicide concentrations rose rapidly in the spring and diminished gradually over a few months. Sancho et al. (1997) reported that the insecticide fenitrothion showed a strong tendency to bioconcentrate into the brain of the European eel(Anguilla anguilla).

Comparison of Approximate Computing with Sobel Edge Detection

Yunchul Chung,Youngmin Kim 대한전자공학회 2021 IEIE Transactions on Smart Processing & Computing Vol.10 No.4

In this study, a Sobel filter with approximate computing was used to detect the edge of an image and compare the quality of the output images and error metrics of various approximate adders. Approximate computing is performed by applying the logic of various approximate adders to the lower-bit part of the addition operation of the Sobel filter. The image quality of the edge detection result and error metrics are analyzed by varying approximating bits. The approximate adders used include an Approximate Mirror Adder (AMA), Approximate XOR/XNOR-based Adder (AXA), and Inexact Adder (InXA). A simulation was performed in Quartus using Verilog HDL. The precise adder and the approximate adder logic were applied to the low part, synthesized, and compared. The two filters were compared through various error metrics for approximate computing and logic utilization indicating how much of the logic module has been used. In the simulation, the Sobel filter with the AMA4 showed the best error metrics and performance logic among the 10 types of approximate adders. The results show that approximate adder logic with the appropriate approximate bits can be applied to an edge-detecting filter and has an acceptable error and image quality.

Anomalous 0.7 Electrical Conductance Quantization in Nano-scale Constriction

Yunchul Chung,Dong-In Chang,Sang-Hyun Jo,Michelle zaffalon,Vladimir Umansky,Moty Heiblum,Hu-Jong Lee 한국자기학회 2006 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Study on reuse of hydrofluoric acid wastewater

鄭允喆,NA, Jaesik,Lee, Wonkwon 嶺南大學校 環境問題硏究所 1997 環境硏究 Vol.17 No.1

ABSTRACTReverse osmosis has been applied in this study for reusing water in hydrofluoric acid wastewater after lime treatment. Experimental results show a high degree of rejection of almost impurities by certain membrane in a single pass. The major impurity has been investigated for long period stability of the membrane exposed hydrofluoric acid wastewater.

Quantization of the Current Induced by a Surface Acoustic Wave through a Quantum Point Contact

김남,Yunchul Chung,Byung-Chill Woo,Jinhee Kim,Minky Seo 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I

The acousto-electric currents through a quantum point contact induced by surface acoustic waves were observed. The current was found to be quantized at integer multiples of $ef$, where $f$ is the surface acoustic frequency. By using an interdigitated transducer with a 500 nm spacing between the gates, we produced surface acoustic waves at 2.456 GHz, which resulted in 1.18 nA quantized current when three electrons were transferred from the source to the drain at a time. Also, we found that the quantization is related to the a presence of a static quantum dot unintentionally formed in a quantum point contact.

PESTICIDE WASTEWATER TREATMENT USING ELECTROCHEMICAL OXIDATION

Pak, Daewon,Chung, Dowon,Chung, Yunchul 영남대학교 환경문제연구소 2000 環境硏究 Vol.20 No.1

Electrochemical treatment of wastewater generated from the production of chemicals used to make insecticide, herbicide, and pesticide is investigated. IrO2/SnO2 film electrode prepared on titanium was used as an anode in the electrochemical cell. Based on TOC data obtained from the batch test, organic compounds in the wastewater was oxidized and mineralized. Some organic compounds did not undergo electrochemical oxidation. In order to identify those compounds, gel permeation chromatogram and GC/MS analysis was made. Factors that determine electrochemical oxidation rate were investigated. TOC removal rate was strongly affected by current density. Eleotrochemical oxidation rate was not improved under acidic condition. Continuous test was performed to investigate preliminary design parameter for electrochemical cell.

미생물산 고분자를 이용한 활성슬러지 효율증진에 대한 연구

박대원,정윤철 嶺南大學校 環境問題硏究所 1995 環境硏究 Vol.15 No.1

A experiment was conducted to monitor the change of treatment efficiency in a activated sludge tank when the microorganism producing polymer was added. Z.ramigera, a microorganism which produce polymer in the activated sludge tank, was cultured to produce the polymer. Once a day the microorganism producing polymer was added to the activated sludge tanks, R-l, R-2, R-3, at the concentration of 0, 10, 100 mg/l, respectively, based on dry weight. Effluents from the activated sludge tanks were analyzed and compared. Total chemical oxygen demand (TCOD) removals in R-l, R-2, R-3 were 78%, 82%, 85%, respectively. The activated sludge tank where microorganism producing polymer was added showed higher removal rate of organic substance. Suspended solid(SS) removal was 77% in R-l. However 89% and 95% of SS removals were obtained in R-2 and R-3, respectively, where microorganism producing polymer acted as a coagulant. When organic loading to an activated sludge tank is increased, sludge bulking is often observed. To investigate the effect of microorganism producing polymer addition under the operating condition leading to sludge bulking, TCOD concentration in the influent was increased from 145 mg/l to 200 mg/l. The treatment efficiency of R-l decreased. However those of R-2 and R-3 increased. After organic loading was increased, sludge bulking was observed in R-l. Good sludge setllability was achieved in R-2 and R-3.

Anaerobic Reactor Technology for Wastewater Treatment

Jung, Jinyoung,Chung, Yunchul 嶺南大學校 環境問題硏究所 1997 環境硏究 Vol.16 No.2

AbstractAnaerobic treatment has been applied to stabilize muncipal sludge and successfully used to treat industrial and hazardous wastewater. Anaerobic reactor technology continues to evolve and UASB and AF are widely used. Hybrid type reactor AUBF(anaerobic upflow sludge bed filter), combining a sludge bed and a filter, was evaluated to treat various wastewaters - organic wastewater containing heavy metals, wastewater with high concentration of ammonia nitrogen, and high-strength organic wastewater. Organic wastewater containing heavy metals such as copper, hexavalent chromium, and nickel were effectively removed up to 92% at 25 mg Cu/L, 98% at 30mg Cr6+/L, and 98% at 40 mg Ni/L, respectively, while organic was efficiently degraded. Two-stages anaerobicaerobic reactor was evaluated to treat organic wastewater with high concentration of ammonia nitrogen. Ammonia nitrogen was removed in the range of 49 to 75% at 1-4.4 recycle ratio and COD removal efficiencies varied from 82 to 94% at 5,000mg/l of influent COD and 500mg/l of NH3-N. Two-phase anaerobic reactor with microfiltration menbrane has been investigated to increase solid retention time in the acidogenic reactor. Menbrane system enhanced acid conversion and ensured a stable operation of the followed methanogenic reactor.

Electron Interference in a Quantum Ring with a Tunable Magnetic Field Shield

Minky Seo,Hwanchul Jung,Yunchul Chung 한국진공학회(ASCT) 2021 Applied Science and Convergence Technology Vol.30 No.2

A quantum ring device that can turn on and off the external magnetic field on the ring is developed. The device is to study the effect of the interaction between electrons and external magnetic fields on Aharonov-Bohm interference. The switching is realized by employing a superconducting shield gate and turning on and off the superconductivity on the gate with applied current or magnetic field. The electron interference due to Aharonov-Bohm effect is observed regardless of the presence of the external magnetic field on the electron path of the ring. The result is consistent with the fact that effects of potentials on charged particles exists even in the region where all the field vanish hence no direct interaction between electron and magnetic field is allowed.

Color Removal with Low Temperature Catalytic Oxidation

Pak, Daewon,Chang, Wonseok,Chung, Yunchul 嶺南大學校 環境問題硏究所 1998 環境硏究 Vol.18 No.1

Novel oxidation technology to decolorize dye wastewater is discussed and the feasibility of color removal with Fe/MgO catalyst fluidizing in a reactor under continuous flow is demonstrated at room temperature. In batch tests, the oxidation reaction of reactive and disperse dye with oxidizing agent, hydrogen peroxide, in the presence of Fe/MgO catalyst is performed. Through the catalytic oxidation, dyes are oxidized to molecules with lower molecular weight and then mineralized based on TOC analysis. The influence of hydrogen peroxide and catalyst dosage on the catalytic oxidation rate is verified. The catalytic oxidation rate increases with increasing hydrogen peroxide and catalyst dosage. Fe/MgO catalyst fluidizing in the reactor operated at room temperature was tested to decolorize the wastewater from a dye manufacturing industry. In the fluidized bed reactor, the wastewater was completely decolorized and about 30% of COD removal was obtained during 30 days of operation. Organic matters were degraded and part of them mineralized by catalytic oxidation. BOD/COD ratio of the effluent from the fluidized bed reactor was increased with compared to that of the influent. After 30 days of operation, the effluent from the fluidized bed reactor started becoming yellowish. COD and residual hydrogen peroxide concentration in the effluent started to increase due to the catalyst losing its activity.