http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Comparative studies of novel biooxidation process to low-grade sulphide gold ores
Ahn Junmo,Wu Jiajia,Lee Jaeheon 한국자원공학회 2022 Geosystem engineering Vol.25 No.4
The Sand Farming is one of novel biooxidation processes suitable for sulphide oxidation of lowgrade refractory gold ores. It has been previously proven to be feasible and more efficient compared to other conventional sulphide oxidation processes. In this study, the Sand Farming was compared with conventional tank biooxidation to investigate biooxidation behaviors on ores with different mineralogy and compare the ultimate gold recovery. Ore samples were tested for Sand Farming biooxidation. Conventional tank biooxidation was also compared as the baseline. After each biooxidation was completed, cyanidation was conducted for gold extraction. The Sand Farming achieved the gold recovery of 75% from high grade with higher sulphur content sample (Sample A) and 68% from low grade with lower sulphur content sample (Sample B), slightly lower than tank biooxidation of 83% and 85%, respectively. Sand Farming can be an alternative to several sulphide oxidation processes with better overall economics.
Junmo Ahn,Eun Hea Jho,Kyoungphile Nam 대한환경공학회 2015 Environmental Engineering Research Vol.20 No.3
The effects of carbon-to-nitrogen (C/N) ratio in simulated rice straw hydrolysates using glucose and ammonium chloride on polyhydroxyalkanoates (PHA) accumulation by Cupriavidus necator was investigated. In general, PHA accumulation rate was higher under higher degrees of N-deficient conditions (e.g., C/N ratio of 360:1) than lower degrees of N-deficient conditions (e.g., C/N ratio of 3.6:1 and 36:1). Also, the most PHA accumulation was observed during the first 12 h after the PHA accumulation initiation. This study showed that the similar PHA accumulation could be achieved by using different accumulation periods depending on C/N ratios. N source presence was important for new cell production, supported by approximately ten times greater PHA accumulation under the N-deficient condition (NH₄Cl 0.01 g/L) than the N-free (without NH₄Cl) condition after 96 h. C/N ratio of the rice straw hydrolysate was approximately 160:1, based on the glucose content, and this accumulated 0.36±0.0033 g/L PHA with PHA content of 21±3.1% after 12 h. Since external C or N source addition for C/N ratio adjustment increases production cost, an appropriate accumulation period may be used for PHA accumulation from organic wastes, based on the PHA accumulation patterns observed at various C/N ratios and C and N concentrations.
High-performance graphene-based transparent flexible heaters.
Kang, Junmo,Kim, Hyeongkeun,Kim, Keun Soo,Lee, Seoung-Ki,Bae, Sukang,Ahn, Jong-Hyun,Kim, Young-Jin,Choi, Jae-Boong,Hong, Byung Hee American Chemical Society 2011 NANO LETTERS Vol.11 No.12
<P>We demonstrate high-performance, flexible, transparent heaters based on large-scale graphene films synthesized by chemical vapor deposition on Cu foils. After multiple transfers and chemical doping processes, the graphene films show sheet resistance as low as 43 Ohm/sq with 89% optical transmittance, which are ideal as low-voltage transparent heaters. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional transparent heaters based on indium tin oxide. In addition, we confirmed that mechanical strain as high as 4% did not substantially affect heater performance. Therefore, graphene-based, flexible, transparent heaters are expected to find uses in a broad range of applications, including automobile defogging/deicing systems and heatable smart windows.</P>
Comparative Leaching Study on Conichalcite and Chalcopyrite Under Different Leaching Systems
Jiajia Wu,Junmo Ahn,Jaeheon Lee 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.4
Copper leaching from low-grade copper ore samples obtained from two active mines in the US, named conichalcite (sample A) and chalcopyrite (sample B), were studied under different leaching conditions using sulfuric acid and methane sulfonic acid (MSA). The conichalcite, sample A, is calcium-copper arsenite hydroxide [CaCu(AsO4)(OH)] with small amount of gold and other metals. The copper grade is 0.41% with 0.48% arsenic and 2.04% sulfur. The chalcopyrite, sample B, was the main mineral with 0.60% copper grade with 0.73% sulfur and 0.032% molybdenum. Leaching systems utilized two oxidants (ferric ion and hydrogen peroxide) to investigate the kinetics of copper extractions. All leaching tests were performed by bottle roll leaching tests with 6.25% pulp density for 24 hours. Results showed that the leaching kinetics were relatively fast for oxidized sample A. Overall copper recovery was slightly affected by the oxidants and higher than 60% copper extraction was observed. Screen fractioned materials and the leached residue analysis showed that the copper grade in the residues are relatively consistent with 0.14-0.16% copper. This results showed that the ore samples contains readily leachable copper and refractory elements in all size fractions. The refractory portion seems to be relative uniform with wide range of easily leachable copper with 0.30 to 0.54%. Copper extraction from sample B using acids with ferric ion as an oxidant showed around 35% but it significantly increased over 80% using hydrogen peroxide as an oxidant. The copper extraction gradually increased up to 3.0 mol/L hydrogen peroxide content.
Material-Versatile Ultrabroadband Light Absorber with Self-Aggregated Multiscale Funnel Structures
Ryu, Yunha,Kim, Changwook,Ahn, Junmo,Urbas, Augustine M.,Park, Wounjhang,Kim, Kyoungsik American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.35
<P>Broadband light absorbers are essential components for a variety of applications, including energy harvesting and optoelectronic devices. Thus, the development of a versatile absorbing structure that is applicable in various operating environments is required. In this study, a material-versatile ultrabroadband absorber consisting of metal-coated self-aggregated Al<SUB>2</SUB>O<SUB>3</SUB> nanowire bundles with multiscale funnel structures is fabricated. A high absorptance of ∼0.9 over the AM 1.5G spectrum (300-2500 nm) is realized for absorbers with a range of metal coatings, including Al, W, and titanium nitride (TiN). We demonstrate that the plasmonic nanofocusing and index-matching effects of the funnel structure result in strong ultrabroadband absorption for the various metal coatings, even though the coating materials have different optical properties. As an example of applicability in an operating environment, in the evaluation of the thermal-oxidation resistance, the Al-coated solar absorber exhibits superior performance to those coated with refractory materials such as W and TiN because of the protective alumina layer formed on the Al surface.</P> [FIG OMISSION]</BR>
MPCore Based Task Scheduling under Peak Power Constraint
Sunghwan Park,Byunggyu Ahn,Junmo Jung,Hyunglae Roh,Bong-sik Sihn,Liao ZhiRui,Jongwha Chong 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
In this paper, we propose a new task scheduling algorithm which can chedule tasks under peak power constraint for MPCore systems. To gain accurate power profile of each task, we simulate the tasks under virtual platform which can estimate power consumption of each instruction. And then, we apply PWL (Piece-Wise Linear) modeling to the power profile of each task to divide a task to some sub-tasks. To meet peak power and average power constraints, we schedule each sub-task in MPCore. If there is no dependency between tasks, we use DVS algorithm in each core to minimize power consumption. We demonstrate the proposed approaches using some benchmark applications.
정혜원,이제승,송강훈,박민서,안준모,Hyewon Jung,Jeseung Lee,Ganghoon Song,Minseo Park,Junmo Ahn The Korean Institute of Resources Recycling 2024 資源 리싸이클링 Vol.33 No.1
Critical minerals such as nickel, cobalt and lithium, are known as materials for cathodic active materials of lithium ion batteries. The consumption of the minerals is expected to grow with increasing the demands of electric vehicles, resulting from carbon neutrality. Especially, the demand for LIB (lithium ion battery) recycling is expected to increase to meet the supply of nickel, cobalt and lithium for LIB. The recycling of EOL (end-of-life) LIB can be achieved by leaching EOL LIB using inorganic acid such as HCl, HNO<sub>3</sub> and H<sub>2</sub>SO<sub>4</sub>, which are regarded as hazardous materials. In the present study, the potential use of MSA (Methanesulfonic acid), as an alternative lixiviant replacing sulfuric acid was investigated. In addition, leaching behaviors of NCM black mass leaching with MSA was also investigated by studying various leaching factors such as chemical concentration, leaching time, pulp density (P/D) and temperatures. The leaching efficiency of nickel (Ni), cobalt (Co), lithium (Li), and manganese (Mn) from LIB was enhanced by increasing concentration of lixiviant and reductant, leaching time and temperature. The maximum leaching of the metals was above 99% at 80℃. In addition, MSA can replace sulfuric acid to recover Ni, Co, Li, Mn from NCM black mass.