22 results on '"Choi, Junyoung"'
Search Results
2. A Universal Synthesis of Single‐Atom Catalysts via Operando Bond Formation Driven by Electricity.
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Zhan, Xinyu, Zhang, Libing, Choi, Junyoung, Tan, Xinyi, Hong, Song, Wu, Tai‐Sing, Xiong, Pei, Soo, Yun‐Liang, Hao, Leiduan, Li, Molly Meng‐Jung, Xu, Liang, Robertson, Alex W., Jung, Yousung, Sun, Xiaofu, and Sun, Zhenyu
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METAL bonding , *ELECTROLYTIC reduction , *ELECTROSYNTHESIS , *CATALYST synthesis , *METALLIC oxides - Abstract
Single‐atom catalysts (SACs), featuring highly uniform active sites, tunable coordination environments, and synergistic effects with support, have emerged as one of the most efficient catalysts for various reactions, particularly for electrochemical CO2 reduction (ECR). However, the scalability of SACs is restricted due to the limited choice of available support and problems that emerge when preparing SACs by thermal deposition. Here, an in situ reconstruction method for preparing SACs is developed with a variety of atomic sites, including nickel, cadmium, cobalt, and magnesium. Driven by electricity, different oxygen‐containing metal precursors, such as MOF‐74 and metal oxides, are directly atomized onto nitrogen‐doped carbon (NC) supports, yielding SACs with variable metal active sites and coordination structures. The electrochemical force facilitates the in situ generation of bonds between the metal and the supports without the need for additional complex steps. A series of MNxOy (M denotes metal) SACs on NC have been synthesized and utilized for ECR. Among these, NiNxOy SACs using Ni‐MOF‐74 as a metal precursor exhibit excellent ECR performance. This universal and general SAC synthesis strategy at room temperature is simpler than most reported synthesis methods to date, providing practical guidance for the design of the next generation of high‐performance SACs. [ABSTRACT FROM AUTHOR]
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- 2024
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3. Understanding the catalytic mechanism of calcium compounds for enhancing crystallinity in carbon fiber.
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Lee, Sora, Choi, Junyoung, Chung, Yong Sik, Kim, Jiwoong, Moon, Sookyoung, and Lee, Sungho
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CALCIUM compounds , *GRAPHITIZATION , *CARBON fibers , *PAN-based carbon fibers , *CALCIUM ions , *HEAT treatment , *ELECTRIC conductivity - Abstract
[Display omitted] • PAN-based carbon fibers with highly developed microstructures via calcium-assisted thermal treatments is reported. • The catalytic effect of Ca compounds on CF graphitization at low temperatures of 1600 °C was observed. • The effect of Ca on the structural changes of CFs was investigated via AIMD simulations. • We suggest a new and affordable methodology to manufacture CF with significantly higher conductivities and moduli. Graphitized carbon fibers are attractive materials because of their high tensile modulus and thermal and electrical conductivities. These attributes derive from their crystalline structures that develop during heat treatments of up to 3000 °C. Despite the costly thermal processes, there is a structural limit for achieving these sought-after properties for polyacrylonitrile-based carbon fibers. Herein, the preparation of polyacrylonitrile-based carbon fibers with highly developed microstructures via calcium-assisted thermal treatments of up to 2700 °C is reported. Carbon fibers hydrothermally immersed in a solution of calcium carbonate were heat-treated and their chemical structures traced to investigate the calcium-assisted catalytic graphitization mechanism. Graphitic structures appeared at 1400 °C, accompanied by intermediate complexes of carbon and calcium on the carbon fibers surfaces. Further heat treatment of the calcium compounds at 1600 °C to incorporate carbon fibers resulted in an interlayer spacing of 0.3360 nm, which was unachievable solely through heat treatment at 2700 °C. In addition, the achieved tensile modulus and electrical conductivity of 480 GPa and 1.7 × 103 S/cm, respectively, were significantly higher than those of pure carbon fibers. The calcium ions penetrating the internal structure of the carbon fibers aligned the non-uniform graphene structure and developed the graphite structure of the carbon fibers by acting as catalysts, even at low temperatures. [ABSTRACT FROM AUTHOR]
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- 2024
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4. Suppression of dendrites and granules in surface-patterned Li metal anodes using CsPF6.
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Kim, Seokwoo, Choi, Junyoung, Lee, Hongkyung, Jeong, Yong-Cheol, Lee, Yong Min, and Ryou, Myung-Hyun
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ANODES , *LITHIUM ions , *DENDRITIC crystals , *GRANULE cells , *CESIUM - Abstract
Abstract Unexpected Li deposition during plating, which causes low Coulombic efficiency and safety issues, limits the use of Li metal as an anode in commercial secondary batteries. With the recently developed micro-patterned Li metal anodes, dendrite formation during high current Li plating (2.4 mA cm−2) has successfully been reduced, as Li ions are guided into the patterned holes. However, the uncontrolled formation of granular Li is still observed in this material. To overcome these shortcomings, we have introduced cesium hexafluorophosphate into micro-patterned Li metal anodes. This additive employs the self-healing electrostatic shield mechanism to effectively reduce the formation of granular Li and Li dendrites, thereby significantly improving the electrochemical performance of the anodes even when only small amounts (0.05 M) of electrolyte are used. Our experiments revealed that batteries employing surface-patterned Li metal anodes with cesium hexafluorophosphate maintained 88.7% (96.6 mAh g−1) of their initial discharge capacity after the 900th cycle (Charging current density: C/2, 0.6 mA cm−2, Discharging current density: 1C, 1.2 mA cm−2), which is three times higher than the capacity observed with surface-patterned Li metal anodes without the additive (discharge capacity starts to decrease from 300 cycles). Graphical abstract Image 1 Highlights • Cesium hexafluorophosphate was introduced to surface-patterned Li metal anodes. • Cs+ ions and patterned Li showed synergistic improvement in cycle performance. • Cs+ ions hindered the formation of granule and dendrites of patterned Li metal. • Cs+ ions stabilized the morphology of the surface-patterned Li metal anodes during cycling. [ABSTRACT FROM AUTHOR]
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- 2019
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5. Effectiveness of water spray in infrared signature suppression of engine plumes.
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Choi, Junyoung, Moon, Sungjae, Kim, Hyemin, and Choi, Seongman
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SPRAY nozzles , *IR spectrometers , *STEALTH aircraft , *WATER pressure , *MILITARY airplanes , *ENGINES , *SPRAYING & dusting in agriculture , *OIL field flooding - Abstract
• The quantitative measurement of the effect of water spray on mitigating the IR signature from the engine plume was conducted. • Higher injection pressure resulted in the formation of a denser water spray cloud, thereby increasing the attenuation effect on the IR signature. • The water spray cloud effectively attenuated the IR signature, with enhanced effectiveness observed at lower observation angles. In modern military aircraft, reducing the Infrared (IR) signature is critical for stealth. However, the IR signature from the engine plume is particularly challenging to address due to its link with engine operation and its unique, non-continuous characteristics. In this study, a novel approach using a water spray cloud to attenuate the IR signature from the engine plume was proposed, and it is experimentally verified by employing a micro-turbine engine. Six water nozzles generated the water spray cloud, and IR signature reduction was quantitatively measured using an IR spectrometer. Variations in water injection pressure and observation angles were used as experimental conditions. The results revealed that the IR signature was reduced with higher water injection pressure, attributed to the increased thickness of the water spray cloud. The IR signature from the engine plume was effectively attenuated by the water spray cloud in overall, with a more pronounced effect observed at lower observation angles due to the extended path within the cloud. The potential of water spray clouds for enhancing the IR stealth of military aircraft is underscored by this research. [ABSTRACT FROM AUTHOR]
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- 2023
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6. Single‐Atom Cadmium‐N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra‐Long Lifetime.
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Zhu, Kaige, Li, Xin, Choi, Junyoung, Choi, Changhyeok, Hong, Song, Tan, Xinyi, Wu, Tai‐Sing, Soo, Yun‐Liang, Hao, Leiduan, Robertson, Alex W., Jung, Yousung, and Sun, Zhenyu
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ELECTRIC batteries , *STORAGE batteries , *CARBON sequestration , *METAL catalysts , *DENSITY functional theory , *CATALYTIC activity - Abstract
The rechargeable Li–CO2 battery shows great potential in civil, military, and aerospace fields due to its high theoretical energy density and CO2 capture capability. To facilitate the practical application of Li–CO2 battery, the design of efficient, low‐cost, and robust non‐noble metal cathodes to boost CO2 reduction/evolution kinetics is highly desirable yet remains a challenge. Herein, single‐atom cadmium is reported with a Cd‐N4 coordination structure enable rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li–CO2 battery, even up to 10 A g−1, and remains stable at a high current density (100 A g−1). An unprecedented discharge capacity of 160045 mAh g−1 is attained at 500 mA g−1. Excellent cycling stability is maintained for 1685 and 669 cycles at 1 A g−1 and capacities of 0.5 and 1 Ah g−1, respectively. Density functional theory calculations reveal low energy barriers for both Li2CO3 formation and decomposition reactions during the respective discharge and recharge process, evidencing the high catalytic activity of single Cd sites. This study provides a simple and effective avenue for developing highly active and stable single‐atom non‐precious metal cathode catalysts for advanced Li–CO2 batteries. [ABSTRACT FROM AUTHOR]
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- 2023
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7. Effects of compressor frequency and heat exchanger geometry on dynamic performance characteristics of heat pump dryers.
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Choi, JunYoung, Lee, DongChan, Park, Myeong Hyeon, Lee, Yongju, and Kim, Yongchan
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HEAT pumps , *HEAT exchangers , *COMPRESSORS , *THERMODYNAMIC cycles , *ENERGY consumption - Abstract
A heat pump dryer (HPD) exhibits significant transient behaviors owing to the combined system of the heat pump cycle and closed-loop air cycle. However, a complete transient simulation for HPDs has not been yet developed owing to its complicated equations and lack of experimental data. In this study, a complete transient simulation of an HPD was developed using the finite volume method and was validated with experimental data, presenting validation errors less than 6.1%. Using the developed simulation model, the dynamic behavior and performance of the HPD were analyzed by varying operation modes and heat exchanger length. The operation mode with a higher compressor frequency showed a 16.5% higher moisture extraction rate (MER) due to the decreased drying time, whereas that with a lower frequency showed a 34.8% higher specific moisture extraction rate (SMER) due to the decreased energy consumption. As the heat exchanger length increased from 80% to 120%, the MER increased by 10% and the SMER increased by 14%. Additionally, as the compressor frequency increased, the optimum heat exchanger length for achieving maximum performance increased. In conclusion, the compressor control logic and heat exchanger length should be optimized according to the drying time, power consumption, and initial cost. • A transient simulation model for heat pump dryers is developed and validated. • Effects of operation mode and heat exchanger length on the performance are studied. • High compressor frequency results in high moisture extraction and energy consumption. • Increase in heat exchanger length reduces drying time as well as energy consumption. • Optimum lengths of heat exchangers are investigated based on compressor frequency. [ABSTRACT FROM AUTHOR]
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- 2021
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8. Plume IR characteristics of microturbine engine in various bypass ratios.
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Choi, Junyoung, Jang, Hyeonsik, Kim, Hyemin, and Choi, Seongman
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TURBOFAN engines , *IR spectrometers , *PLUMES (Fluid dynamics) , *ENGINES - Abstract
• IR signature of the microturbine engine plume was measured in different bypass ratio and observation angle. • The plume IR signature diminished when the observation angle increased due to the shorter path of the length. • Rise of the bypass ratio reduced the plume IR signature, but the reduction rate did not linearly match with the bypass ratio. The reduction in IR signature from aircrafts in modern warfare is one of the most important factors that increase survivability and stealth capability. IR signature from the engine exhaust plume cannot be reduced easily and can pose a hazard because they are vulnerable to detection by IR-guided missiles. Therefore, it is essential to observe the engine plume IR signature under various conditions for the plume IR reduction design of aircraft. This study focused on analyzing the effect of the observation angle and bypass ratio on the plume IR signature. A modified microturbine engine system was prepared to apply a bypass ratio to the plume, and the IR signature was measured using an IR spectrometer. The IR signature of the engine plume was measured at observation angles of 30°, 60°, and 90° and bypass ratios of 0, 0.5, and 1. In this study, an increase in the observation angle and bypass ratio attenuated the IR signature, whereas the reduction ratio was not constant with the changes. [ABSTRACT FROM AUTHOR]
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- 2021
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9. Highly Stable Porous Polyimide Sponge as a Separator for Lithium-Metal Secondary Batteries.
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Choi, Junyoung, Yang, Kwansoo, Bae, Hyeon-Su, Phiri, Isheunesu, Ahn, Hyun Jeong, Won, Jong Chan, Lee, Yong Min, Kim, Yun Ho, and Ryou, Myung-Hyun
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STORAGE batteries , *MACHINE separators , *OPEN-circuit voltage , *IONIC conductivity , *LITHIUM-ion batteries , *POROUS metals , *SOLID state batteries - Abstract
To inhibit Li-dendrite growth on lithium (Li)-metal electrodes, which causes capacity deterioration and safety issues in Li-ion batteries, we prepared a porous polyimide (PI) sponge using a solution-processable high internal-phase emulsion technique with a water-soluble PI precursor solution; the process is not only simple but also environmentally friendly. The prepared PI sponge was processed into porous PI separators and used for Li-metal electrodes. The physical properties (e.g., thermal stability, liquid electrolyte uptake, and ionic conductivity) of the porous PI separators and their effect on the Li-metal anodes (e.g., self-discharge and open-circuit voltage properties after storage, cycle performance, rate capability, and morphological changes) were investigated. Owing to the thermally stable properties of the PI polymer, the porous PI separators demonstrated no dimensional changes up to 180 °C. In comparison with commercialized polyethylene (PE) separators, the porous PI separators exhibited improved wetting ability for liquid electrolytes; thus, the latter improved not only the physical properties (e.g., improved the electrolyte uptake and ionic conductivity) but also the electrochemical properties of Li-metal electrodes (e.g., maintained stable self-discharge capacity and open-circuit voltage features after storage and improved the cycle performance and rate capability) in comparison with PE separators. [ABSTRACT FROM AUTHOR]
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- 2020
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10. Pool boiling heat transfer enhancement using the micro-thick metallic foam surface in saturated water.
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Lim, Hyunmuk, Doh, Su-Yoon, Choi, Junyoung, Moc, Jungchan, You, Seung M., and Lee, Jungho
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EBULLITION , *METAL foams , *METALLIC surfaces , *HEAT transfer coefficient , *HEAT transfer , *HEAT flux , *DISSOLVED air flotation (Water purification) - Abstract
Pool boiling experiments using micro-thick metallic foam (MMF) are performed in saturated water at atmospheric pressure. Sintered experimental samples were fabricated with micro-thick metallic foam instead of soldering for the rigorous pool boiling experiments. This study provides the heat transfer coefficient and the critical heat flux (CHF) of the metallic foam surfaces for different pore densities and thicknesses. Also, the boiling mechanism and bubble dynamics on the micro-thick metallic foams for pool boiling were investigated with their visualization. As a result, the MMF surface with 200 μm thick and 130 PPI has a CHF of 2050 kW/m2 and a heat transfer coefficient of 273.6 kW/m2∙K, respectively. Compared with other surface modification methods, MMFs with a thickness of about 200 μm to 300 μm can enhance heat transfer characteristics and increase the CHF. In particular, the increase in CHF might be attributed to the highly permeable structure of the metallic foam. Therefore, this study presents valuable insight into a feasible material-insensitive heat transfer enhancement method for pool boiling. [ABSTRACT FROM AUTHOR]
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- 2024
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11. Strengthening of carbon nanotube fiber using ecofriendly triblock copolymer and newly designed characterization via low-frequency noise.
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Eo, Su Bin, Lee, Jinyong, Choi, Junyoung, Son, Hayoung, Lee, Jae Won, Kim, Sung-Soo, Lee, Min Wook, Hwang, Jun Yeon, Kim, Jiwoong, Jeon, Dae-Young, and Moon, Sook Young
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CARBON nanotubes , *CARBON fibers , *YOUNG'S modulus , *ETHYLENE glycol , *NOISE measurement , *BLOCK copolymers - Abstract
In this study, carbon nanotube fibers (CNTFs) were strengthened by densifying and reorienting CNT bundles using a triblock copolymer (poly (propylene glycol)– block -poly (ethylene glycol)– block -poly (propylene glycol (PPG–PEG–PPG)). This copolymer possesses a unique combination of hydrophilic and hydrophobic molecules, enabling it to easily penetrate and expand the distance between bundles. Through a stretching process after impregnation, the CNTFs induced a structural alignment of the bundles, resulting in high integration of the CNT bundles. The microstructural analysis of the fiber cross-section revealed an increased number of aligned CNTs along the fiber direction, concomitant with a reduction in the bundle-to-bundle distance owing to bundle aggregation. The highly aligned structure showed an average specific tensile strength of 0.536 N/tex and specific elastic modulus of 66.3 N/tex, which is an increase of 175 % and 252 %, respectively, compared to the pristine CNTF. The polymer infiltration stretching method effectively aggregated CNT bundles and removed macro voids within the CNTF. Additionally, the densification and alignment of CNTFs were characterized through novel low-frequency noise measurement and analysis. Understanding the nanoscale structure and morphology of CNTFs in nanoscale will provide valuable guidance for building enhanced strengthening strategies. [Display omitted] • CNT fiber (CNTF) was reoriented and densified by wet stretching method using a triblock copolymer. • The structure modified CNTFs enhanced tensile strength, Young's modulus, and electrical conductivities. • A low-frequency noise method was used to investigate the densification and alignment quality of CNT bundles. [ABSTRACT FROM AUTHOR]
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- 2024
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12. Gamma 3 U-Blade lag screws in patients with trochanteric femur fractures: are rotation control lag screws better than others?
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Yoo, Jehyun, Kim, Sangmin, Choi, Junyoung, and Hwang, Jihyo
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BONE screws , *COMPUTED tomography , *DIAGNOSIS , *FEMUR neck , *FRACTURE fixation , *BONE fractures , *GAIT in humans , *HIP joint injuries , *PROSTHETICS , *RISK assessment , *THREE-dimensional imaging , *BONE density , *BODY mass index , *TREATMENT effectiveness ,RISK of prosthesis complications - Abstract
Background: Intramedullary hip nails may be classified as blades or screws depending on the type of lag screw used. Recently, a combination of lag screw types with a U-clip insertion has also been used. The purpose of this study was to evaluate the clinical and radiological outcomes of these new screw types. Methods: A total of 185 patients with trochanteric femoral fractures (age ≥ 65 years) who underwent surgery with intramedullary nails were selected. Surgeries with InterTrochanteric/SubTrochanteric (ITST), Proximal Femoral Nail Antirotation (PFNA), and Gamma 3 U-Blade lag screws were performed between January 2011 and June 2016. The AO/OTA classification, presence of a basicervical fracture type on 3D-CT, BMI, BMD, reduction quality, position of the lag screw, TAD (tip apex distance) of the lag screw, sliding distance of the lag screw, varus change (neck shaft angle), radiological union period, fixation failure and functional outcome as determined by walking ability were analyzed. Results: There were 3/60 (5.0%) cases of fixation failure in the ITST group, all caused by cut-out; 4/57 (7.0%) in the PFNA II group: 3 caused by cut-through and 1 by metal fracture; 1/68 (1.5%) in the Gamma 3 U-Blade lag screw group (P = 0.301). In each group, the sliding distance of the lag screw showed a significant difference (P = 0.017), whereas significant sliding over 10 mm showed no statistically significant results. Conclusion: There was only one (1.5%) case of fixation failure in the Gamma 3 U-Blade lag screw group. The sliding distance of the U-Blade was found to be in the middle, between the PFNA II (shorter) and ITST (longer) implants. The new rotational control lag screw seems to be comparable to other screw types. [ABSTRACT FROM AUTHOR]
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- 2019
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13. The HSP90 inhibitor, NVP-AUY922, attenuates intrinsic PI3K inhibitor resistance in KRAS-mutant non-small cell lung cancer.
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Park, Kang-Seo, Yang, Hannah, Choi, Junyoung, Seo, Seyoung, Kim, Deokhoon, Lee, Chang Hoon, Jeon, Hanwool, Kim, Sang-We, and Lee, Dae Ho
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HEAT shock proteins , *NON-small-cell lung carcinoma , *PHOSPHATIDYLINOSITOL 3-kinases , *ENZYME inhibitors , *DRUG resistance in cancer cells , *GENETIC mutation , *ANIMAL experimentation , *ANTINEOPLASTIC agents , *CELL lines , *CELLULAR signal transduction , *GENES , *HETEROCYCLIC compounds , *LUNG cancer , *LUNG tumors , *MICE , *PHENOLS , *PHOSPHOTRANSFERASES , *PROTEINS , *PROTEIN kinase inhibitors , *CHEMICAL inhibitors , *PHARMACODYNAMICS - Abstract
More than 25% of non-small cell lung cancers (NSCLCs) carry mutations in KRAS, one of the most common oncogenic drivers in this disease. KRAS-mutant NSCLC responds poorly to currently available therapies; therefore, novel treatment strategies are needed. Here, we describe a particularly promising targeted therapeutic strategy against KRAS mutation-harboring NSCLC intrinsically resistant to treatment by PI3K inhibition. We found that intrinsic resistance to PI3K inhibition derived from RAF/MEK/ERK and RSK activation, bypassing blockage of the PI3K/AKT/mTOR pathway. The HSP90 inhibitor AUY922 suppressed both PI3K/AKT/mTOR and RAF/MEK/ERK signaling, rendering cells sensitive to a PI3K inhibitor (omipalisib, GSK458). Combining these two drugs achieved a synergistic effect, even using only sub-therapeutic concentrations. Dual inhibition of the HSP90 and PI3K signaling pathways with sub-therapeutic doses of these combined anticancer drugs may represent a potent treatment strategy for KRAS-mutant NSCLC with intrinsic resistance to PI3K inhibition. [ABSTRACT FROM AUTHOR]
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- 2017
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14. Single‐Atom Cadmium‐N4 Sites for Rechargeable Li–CO2 Batteries with High Capacity and Ultra‐Long Lifetime (Adv. Funct. Mater. 25/2023).
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Zhu, Kaige, Li, Xin, Choi, Junyoung, Choi, Changhyeok, Hong, Song, Tan, Xinyi, Wu, Tai‐Sing, Soo, Yun‐Liang, Hao, Leiduan, Robertson, Alex W., Jung, Yousung, and Sun, Zhenyu
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STORAGE batteries , *ELECTRIC batteries , *ELECTROCATALYSIS - Abstract
CO2 reduction, electrocatalysis, Li-CO2 battery, single-atom catalysts Single-Atom Cadmium-N4 Sites for Rechargeable Li-CO2 Batteries with High Capacity and Ultra-Long Lifetime (Adv. Funct. Keywords: CO2 reduction; electrocatalysis; Li-CO2 battery; single-atom catalysts EN CO2 reduction electrocatalysis Li-CO2 battery single-atom catalysts 1 1 1 06/22/23 20230619 NES 230619 B Single-Atom Catalysts b In article number 2213841, Zhenyu Sun, Yousung Jung, Xinyi Tan, and co-workers report, that single-atom cadmium with a Cd-N SB 4 sb coordination structure enables rapid kinetics of both the discharge and recharge process when employed as a cathode catalyst, and thus facilitates exceptional rate performance in a Li-CO SB 2 sb battery, even up to 10 A g SP -1 sp , and remains stable at a high current density (100 A g SP -1 sp ). [Extracted from the article]
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- 2023
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15. The natural flavonoid galangin inhibits osteoclastic bone destruction and osteoclastogenesis by suppressing NF-κB in collagen-induced arthritis and bone marrow-derived macrophages
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Huh, Jeong-Eun, Jung, In-Tae, Choi, Junyoung, Baek, Yong-Hyeon, Lee, Jae-Dong, Park, Dong-Suk, and Choi, Do-Young
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FLAVONOIDS , *OSTEOCLASTS , *ARTHRITIS , *COLLAGEN , *MACROPHAGES , *OSTEOPROTEGERIN , *NF-kappa B - Abstract
Abstract: We investigated the effect of galangin, a natural flavonoid, on osteoclastic bone destruction in collagen-induced arthritis and examined the molecular mechanisms by which galangin affects osteoclastogenesis in bone marrow derived macrophages. In mice with collagen-induced arthritis, administration of galangin significantly reduced the arthritis clinical score, edema and severity of disease without toxicity. Interestingly, galangin treatment during a later stage of collagen-induced arthritis, using mice with a higher clinical arthritis score, still significantly slowed the progression of the disease. Extensive cartilage and bone erosive changes as well as synovial inflammation, synovial hyperplasia and pannus formation were dramatically inhibited in arthritic mice treated with galangin. Furthermore, galangin-treated arthritic mice showed a significant reduction in the concentrations of IL-1β, TNF-α and IL-17 . We found that galangin inhibited osteoclastogenic factors and osteoclast formation in bone marrow-derived macrophages and osteoblast co-cultured cells, and increased osteoprotegerin (OPG) levels in osteoblasts. Galangin and NF-κB siRNA suppressed RANKL-induced phosphorylation of the c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), but not AKT and extracellular signal-regulated kinase 1/2 (ERK1/2). Also, the JNK inhibitor SP600125 and p38 inhibitor SB203580 reduced RANKL-induced expressions of phospho-c-Jun, c-fos and NFATc1 genes during osteoclast development. In addition, galangin suppressed RANKL-induced phosphorylation of NF-κB, phospho-IκBα, inflammatory cytokines and osteoclast formation in bone marrow-derived macrophages. Our data suggest that galangin prevented osteoclastic bone destruction and osteoclastogenesis in osteoclast precursors as well as in collagen-induced arthritis mice without toxicity via attenuation of RANKL-induced activation of JNK, p38 and NF-κB pathways. [Copyright &y& Elsevier]
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- 2013
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16. Improved LDSE processing for the avoidance of overplating yielding 19.2% efficiency on commercial grade crystalline Si solar cell
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Lee, Eunjoo, Lee, Hyunwoo, Choi, Junyoung, Oh, Dongjun, Shim, Jimyung, Cho, Kyungyeun, Kim, Jisun, Lee, Soohong, Hallam, Brett, Wenham, Stuart R., and Lee, Haeseok
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SILICON solar cells , *LASERS , *PLATING , *SEMICONDUCTOR doping , *SILICON nitride , *LIGHT , *PLASMA-enhanced chemical vapor deposition , *CHEMICAL processes - Abstract
Abstract: A record in laser doped selective emitter (LDSE) solar cells with an efficiency η=19.2% is reported. In this study, we investigate the effect of SiN x films for laser doped selective emitter solar cells with plated front contacts. It is observed that the condition of processes such as silicon nitride and laser doping (LD) is of critical importance prior to light induced plating. If these processes are not performed optimally, localized shunts may form during the light induced plating (LIP) process that then inhibit plating in the surrounding areas. In the previous work an efficiency of 18.3% has been achieved, even though the fill factor was only 74.2% and the cell suffered from additional shunting and shading losses due to overplating. However, in this work, we demonstrate that with the optimization of the PECVD SiN x and metallization processes, cells have reached efficiencies of more than 19% on commercial grade p-type CZ Si substrates. [Copyright &y& Elsevier]
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- 2011
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17. Flow patterns and heat transfer characteristics of R-1234ze(E) for downward condensation in a plate heat exchanger.
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Lee, DongChan, Yun, Sungho, Choi, JunYoung, and Kim, Yongchan
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PLATE heat exchangers , *CONDENSATION , *FLOW visualization , *HEAT transfer , *HEAT transfer coefficient , *PRESSURE drop (Fluid dynamics) , *FILM flow - Abstract
l Condensation flow patterns of R-1234ze(E) in a plate heat exchanger are studied. l Dynamic flow characteristics and trend of plate surface temperature are analyzed. l Heat transfer coefficient and pressure drop are analyzed considering flow patterns. l Flow pattern map and transition correlation between flow patterns are developed. This study investigates the condensation flow patterns and heat transfer characteristics of a low global warming potential refrigerant R-1234ze(E) for downward flow in a plate heat exchanger through flow visualization. An asymmetric flow aspect for downward condensation is characterized by vapor- and liquid-preferred paths owing to the effect of gravity. Flow patterns for downward condensation are classified into two regimes: steady film flow without intermittent flooding and pulsating film flow involving intermittent flooding. Additionally, the condensation heat transfer coefficient and frictional pressure drop were analyzed considering flow patterns. Intermittent flooding is hardly related to the heat transfer performance. A frequency analysis of the pressure drop exhibited a considerable difference in periodic characteristics between the flow regimes with and without intermittent flooding. Finally, the visualization data coincided with the flow pattern map proposed by the existing study, and an empirical correlation for predicting the flow transition between pulsating and steady film flow was developed in terms of the Weber number. [ABSTRACT FROM AUTHOR]
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- 2021
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18. HSP90 inhibitor (NVP-AUY922) enhances the anti-cancer effect of BCL-2 inhibitor (ABT-737) in small cell lung cancer expressing BCL-2.
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Yang, Hannah, Lee, Mi-Hee, Park, Intae, Jeon, Hanwool, Choi, Junyoung, Seo, Seyoung, Kim, Sang-We, Koh, Gou Young, Park, Kang-Seo, and Lee, Dae Ho
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SMALL cell lung cancer , *ANTINEOPLASTIC agents , *B cells , *HEAT shock proteins , *CANCER chemotherapy , *PROTEIN metabolism , *ANIMALS , *BIPHENYL compounds , *CELL lines , *CELLULAR signal transduction , *DRUG synergism , *HETEROCYCLIC compounds , *LUNG cancer , *LUNG tumors , *MICE , *PHENOLS , *PROTEINS , *STATISTICAL sampling , *SULFONAMIDES , *CHEMICAL inhibitors , *PHARMACODYNAMICS - Abstract
Small cell lung cancer (SCLC) cannot be efficiently controlled using existing chemotherapy and radiotherapy approaches, indicating the need for new therapeutic strategies. Although ABT-737, a B-cell lymphoma-2 (BCL-2) inhibitor, exerts anticancer effects against BCL-2-expressing SCLC, monotherapy with ABT-737 is associated with limited clinical activity because of the development of resistance and toxicity. Here, we examined whether combination therapy with ABT-737 and heat shock protein 90 (HSP90) inhibitor NVP-AUY922 exerted synergistic anticancer effects on SCLC. We found that the combination of ABT-737 and NVP-AUY922 synergistically induced the apoptosis of BCL-2-expressing SCLC cells. NVP-AUY922 downregulated the expression of AKT and ERK, which activate MCL-1 to induce resistance against ABT-737. The synergistic effect was also partly due to blocking NF-κB activation, which induces anti-apoptosis protein expressions. However, interestingly, targeting BCL-2 and MCL-1 or BCL2 and NF-κB did not induce the cytotoxicity. In conclusion, our study showed that combination of BCL2 inhibitor with HSP90 inhibitor increased activity in in vitro and in vivo study in only BCL-2 expressing SCLC compared to either single BCL2 inhibitor or HSP inhibitor. The enhanced activity might be led by blocking several apoptotic pathways simultaneously rather than a specific pathway. [ABSTRACT FROM AUTHOR]
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- 2017
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19. Modified susceptible–exposed–infectious–recovered model for assessing the effectiveness of non-pharmaceutical interventions during the COVID-19 pandemic in Seoul.
- Author
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Jung, Seungpil, Kim, Jong-Hoon, Hwang, Seung-Sik, Choi, Junyoung, and Lee, Woojoo
- Subjects
- *
COVID-19 pandemic , *SOCIAL distancing - Abstract
Susceptible–exposed–infectious–recovered (SEIR) models were applied to assess the effectiveness of non-pharmaceutical interventions (NPIs) and to study the dynamic behavior of the COVID-19 pandemic. Recently, SEIR models have evolved to address the change of human mobility by some NPIs for predicting the new confirmed cases. However, the models have serious limitations when applied to Seoul. Seoul has two representative quarantine policies, i.e. social distancing and the ban on gatherings. Effects of the two policies need to be reflected in different functional forms in the model because changes in human mobility do not fully reflect the ban on gatherings. Thus we propose a modified SEIR model to assess the effectiveness of social distancing, ban on gatherings and vaccination strategies. The application of the modified SEIR model was illustrated by comparing the model output with real data. • Seoul has two quarantine policies such as social distancing and ban on gatherings. • Ban on gatherings aims to mitigate the risk of mass infection in various facilities. • We propose a modified SEIR model to assess the effectiveness of the two policies. • Effects of the two policies need to be reflected in different functional forms. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
20. The HSP90 inhibitor, NVP-AUY922, sensitizes KRAS-mutant non-small cell lung cancer with intrinsic resistance to MEK inhibitor, trametinib.
- Author
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Park, Kang-Seo, Oh, Bora, Lee, Mi-Hee, Nam, Ky-Youb, Jin, Hae Ran, Yang, Hannah, Choi, Junyoung, Kim, Sang-We, and Lee, Dae Ho
- Subjects
- *
HEAT shock proteins , *NON-small-cell lung carcinoma , *MITOGEN-activated protein kinases , *RAS oncogenes , *PROTEIN kinase B , *PHOSPHOINOSITIDES , *PROTEIN metabolism , *ANIMAL experimentation , *ANTHROPOMETRY , *ANTINEOPLASTIC agents , *CELL lines , *CELL physiology , *CELLULAR signal transduction , *DRUG resistance in cancer cells , *DRUG synergism , *DOSE-effect relationship in pharmacology , *HETEROCYCLIC compounds , *LUNG cancer , *LUNG tumors , *MICE , *GENETIC mutation , *PHENOLS , *PROTEINS , *PYRIDINE , *TIME , *TRANSFERASES , *PROTEIN kinase inhibitors , *CHEMICAL inhibitors , *PHARMACODYNAMICS - Abstract
RAS-driven tumors are often difficult to treat with conventional therapies and therefore, novel treatment strategies are necessary. The present study describes a promising targeted therapeutic strategy against non-small cell lung cancer (NSCLC) harboring KRAS mutations, which has intrinsic resistance to MEK inhibition. Results showed that intrinsic resistance to MEK inhibition occurred via high AKT expression by PI3K activation as a bypass pathway. The HSP90 inhibitor AUY922 suppressed PI3K-AKT-mTOR and RAF-MEK-ERK, and rendered cells sensitive to trametinib (GSK1120212). Synergy from the combination of the two drugs was observed in only sub-therapeutic concentrations of either drug. Dual inhibition of the HSP90 and MEK signaling pathways with sub-therapeutic doses may represent a potent therapeutic strategy to treat KRAS-mutant NSCLC with intrinsic resistance to MEK inhibition and to resolve the toxicity observed upon dual inhibition of AKT and MEK at therapeutic doses in clinical trials. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
21. Molten salts approach of metal-organic framework-derived nitrogen-doped porous carbon as sulfur host for lithium-sulfur batteries.
- Author
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Kyom Kim, Dae, Seul Byun, Jin, Moon, San, Choi, Junyoung, Ha Chang, Joon, and Suk, Jungdon
- Subjects
- *
LITHIUM sulfur batteries , *FUSED salts , *ENERGY storage , *ELECTRIC conductivity , *POROUS metals , *SULFUR , *CARBON - Abstract
[Display omitted] • N-doped mesoporous carbon was synthesized via the molten salt method. • AZT-AC acted as physical barriers to confine polysulfides within the carbon matrix. • The S@ AZT-AC showed the facile and reversible redox kinetics of sulfur. • The lithium-sulfur batteries showed high capacity with the enhanced cycling life. Lithium-sulfur (Li-S) batteries have attracted significant attention as next-generation energy storage systems owing to their high theoretical specific capacity (1675 mAh g−1) and energy density (2567 Wh kg−1). However, the low electrical conductivity of S and the dissolution of polysulfides in organic electrolytes pose significant challenges for their industrial applications. Herein, we report a facile, scalable, and solvent-free synthetic method based on metal–organic-framework (MOF) for synthesizing N-doped carbon-based materials with hierarchical porous structures and large specific surface areas (2297 m2 g−1) as efficient cathode hosts for Li-S batteries. The cathode materials were synthesized via solvent-free mixing, followed by the direct carbonization of adenine and tetracarboxylic acid with zinc acetate using the molten salt method. Zinc salt was employed as a template for mesopores as well as binding sites for other organic materials. The irregular surface morphology and N-doping of the resulting porous carbons act as physical barriers to confine polysulfides within the carbon matrix. The S-loaded cathode was stable and exhibited a discharge capacity of 555 mAh g−1 over 290 cycles at a current density of 0.5C, corresponding to the capacity retention of 63%. The facile modified MOF synthetic strategy, assisted by molten salt processing, holds promise for the synthesis of noble cathode materials for high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
22. Exceeding 19% efficient 6 inch screen printed crystalline silicon solar cells with selective emitter
- Author
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Lee, Eunjoo, Cho, Kyeongyeon, Oh, Dongjoon, Shim, Jimyung, Lee, Hyunwoo, Choi, Junyoung, Kim, Jisun, Shin, Jeongeun, Lee, Soohong, and Lee, Haeseok
- Subjects
- *
CRYSTALS , *SILICON , *SOLAR cells , *DOPING agents (Chemistry) , *DIFFUSION , *RENEWABLE energy sources , *WAVELENGTHS - Abstract
Abstract: The process conditions for high efficiency industrial crystalline Si solar cells with selective emitter were optimized. In the screen printed solar cells, the sheet resistance must be 50–60 Ω/sq. because of metal contact resistance. But the low sheet resistance causes the increase of the recombination and blue response at the short wavelength. Therefore, the screen printed solar cells with homogeneous emitter have limitations of efficiency, and this means that the selective emitter must be used to improve cell efficiency. This work demonstrates the feasibility of a commercially available selective emitter process, based on screen printing and conventional diffusion process. Previous work, we announced about 18.5% efficient selective emitter solar cell by variation of heavy emitter pattern width. Now, we improved cell efficiency from 18.5% to 19% by transition of heavy emitter pattern and shallow emitter doping condition. A maximum cell efficiency of 19.05% is obtained on a 156 mm × 156 mm crystalline silicon solar cell. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
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