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Promotional effect of Mn on Pt/Al2O3 catalysts in HC, CO, and NOx oxidation for controlling diesel emission
No full textEmissions from diesel engines, including hydrocarbons (HCs), carbon monoxide (CO), and nitric oxide (NO), cause serious environmental and human health problems. Diesel oxidation catalysts (DOCs) are drawing attention for their ability to eliminate such harmful exhausts effectively. Here, we report significantly improved activities of Pt-based catalysts, which are widely used as DOCs, in the oxidation of HC, CO, and NOx after Mn addition. Mn-doped Pt/Al2O3 showed significantly lower light-off temperatures in the oxidation of HC, CO, and NOx than those of the unmodified Pt/Al2O3 catalysts, by as much as 30 degrees C. The size of Pt particles was reduced from 71 nm to 33 nm after Mn addition, as evidenced by X-ray diffraction analysis and transmittance electron microscopy. Additionally, the interaction between CO and Pt on Mn-doped catalysts was weakened, and the CO adsorbed on Pt was readily oxidized even at room temperature, as confirmed by diffuse reflectance infrared Fourier-transform spectroscopy and CO temperature-programmed desorption experiments. The results of this study provide insights towards the improvement of the activity of Pt-based DOCs used for HC, CO, and NOx oxidation, by enhancing the fundamental understanding of the Pt nature promoted with Mn
Catalytic behavior of Pt single-atoms supported on CeO2
No full textIn this study, we demonstrate that the CO oxidation activity of Pt/CeO2 single-atom catalysts (& LE;0.4 Pt/nm2) is significantly low despite the increase in reducibility, which is associated with the formation of oxygen vacancies that are critical for oxygen activation, with increasing Pt surface density. This result can be related to the negligible amount of CO adsorbed onto the Pt/CeO2 single-atom catalysts. As the Pt surface density increases to 0.8 Pt/nm2, the activity sharply increases; at this loading, Pt clusters are formed and the interactions with CO are enhanced. Notably, after the controlled reduction treatment using CO, the catalytic activity of 0.4 Pt/CeO2 in-creases to the level of 0.8 Pt/CeO2. The sudden increase in activity can be explained by the formation of a partially reduced Pt cluster and the enhanced CO interactions with the Pt atoms of the cluster. These results indicate that Pt cluster formation and its partial reduction are essential for low-temperature CO oxidation. Our study explains the cause of the significantly low CO oxidation activity of Pt/CeO2 single-atom catalysts and how controlled reduction treatment of these catalysts enhances their activity
Magnetic nanoparticles for ferroptosis cancer therapy with diagnostic imaging
No full textFerroptosis offers a novel method for overcoming therapeutic resistance of cancers to conventional cancer treatment regimens. Its effective use as a cancer therapy requires a precisely targeted approach, which can be facilitated by using nanoparticles and nanomedicine, and their use to enhance ferroptosis is indeed a growing area of research. While a few review papers have been published on iron-dependent mechanism and inducers of ferroptosis cancer therapy that partly covers ferroptosis nanoparticles, there is a need for a comprehensive review focusing on the design of magnetic nanoparticles that can typically supply iron ions to promote ferroptosis and simultaneously enable targeted ferroptosis cancer nanomedicine. Furthermore, magnetic nanoparticles can locally induce ferroptosis and combinational ferroptosis with diagnostic magnetic resonance imaging (MRI). The use of remotely controllable magnetic nanocarriers can offer highly effective localized image-guided ferroptosis cancer nanomedicine. Here, recent developments in magnetically manipulable nanocarriers for ferroptosis cancer nanomedicine with medical imaging are summarized. This review also highlights the advantages of current state-of-the-art image-guided ferroptosis cancer nanomedicine. Finally, image guided combinational ferroptosis cancer therapy with conventional apoptosis-based therapy that enables synergistic tumor therapy is discussed for clinical translations
Stability of Hill's spherical vortex
No full textWe study stability of a spherical vortex introduced by M. Hill in 1894, which is an explicit solution of the three-dimensional incompressible Euler equations. The flow is axi-symmetric with no swirl, the vortex core is simply a ball sliding on the axis of symmetry with a constant speed, and the vorticity in the core is proportional to the distance from the symmetry axis. We use the variational setting introduced by A. Friedman and B. Turkington (Trans. Amer. Math. Soc., 1981), which produced a maximizer of the kinetic energy under constraints on vortex strength, impulse, and circulation. We match the set of maximizers with the Hill's vortex via the uniqueness result of C. Amick and L. Fraenkel (Arch. Rational Mech. Anal., 1986). The matching process is done by an approximation near exceptional points (so-called metrical boundary points) of the vortex core. As a consequence, the stability up to a translation is obtained by using a concentrated compactness method
A Mobile 3D-CNN Processor with Hierarchical Sparsity-Aware Computation and Temporal Redundancy-aware Network
No full textA-site effects of titanate-perovskite (ATiO3)-based catalysts on dehydrogenation of N-heterocyclic molecules
No full textDehydrogenation reactions in liquid organic hydrogen carrier (LOHC) systems present significant challenges, particularly when aiming for low-temperature operations while ensuring that no hydrogen remains in the sub-strate molecules. Enhancing catalytic performance requires modifying the adsorption behavior of the reactants and products during dehydrogenation. Perovskites have emerged as promising catalyst supports because of their ability to modify the surface chemical properties by manipulating the cations present at the A-and B-sites. This study investigated the effects of A-site cations (Ca, Sr, and Ba) in titanate-type perovskite (ATiO3)-a proto-typical perovskite-on the dehydrogenation activity in LOHC systems. Remarkably, Pd/SrTiO3 exhibited outstanding performance by completely converting octahydro-N-methylindole to N-methylindole and releasing 5.76 wt% hydrogen over 8 h. Additionally, it dehydrogenated dodecahydro-N-ethylcarbazole to N-ethylcarbazole with a hydrogen release of 5.70 wt%. Furthermore, the catalyst demonstrated a stable performance after recy-cling tests for three times without degradation or loss of activity. The chemical state of the catalyst surface was characterized through X-ray photoelectron spectroscopy, H2-temperature programmed reduction, and chemi-sorption using NH3, CO2, and H2. The results revealed that the exceptional dehydrogenation activity of Pd/ SrTiO3 is due to the presence of suitable surface oxygen vacancies and abundant acid-base sites
Human reliability evaluation method covering operator action timing for dynamic probabilistic safety assessment
No full textDynamic probabilistic safety assessment (PSA) has been introduced due to the limitations of static-based PSA such as the difficulty to analyze dynamic sequences caused by stochastic random events. While various research has been performed to achieve this integration, quantifying risk in dynamic PSA is still challenging because operator response models that can provide a branch probability according to the timing of operator action in dynamic scenarios have not yet been addressed. Existing human reliability analysis (HRA) models only consider the time given to operators for actions insofar as it can impact the failure probabilities of the human actions, despite the timing of the actions being a vital element of HRA for dynamic scenarios. This paper proposes an operator action timing-based human reliability evaluation method for dynamic PSA to evaluate the distribution of operator action timing. The method covers operator action timings with a model that convolutes two time distribution functions to provide the probability of the success or failure of an operator action. To demonstrate the practicality of the proposed method and its effectiveness, a case study and uncertainty analysis for a small break loss of coolant accident with two operator tasks were conducted
Zwitterionic material for construction of an antifouling polyamide thin film composite membrane
No full textThis research has been supported by the National Research Foundation (NRF) of Korea as funded by the Ministry of Education, Science and Technology (RS-2023-00241009) and by Korea Ministry of Environment (MOE) as ???Graduate School specialized in Integrated Water Resources Management???. The authors are thankful for the support