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Beyond surface area: enhanced pseudocapacitive properties of cobalt layered double hydroxide through structural modifications
Get PDFCobalt hydroxide and other first-row transition metal hydroxides have gained significant attention as pseudocapacitor materials due to their rapid and reversible redox processes. Their layered structures facilitate interactions between electrolyte anions and cobalt cation sites within the bulk of the material, enabling higher charge density and extending redox activity beyond the particle surface. By controlled precipitation under hydrothermal conditions, the structure and morphology of cobalt hydroxides can be optimized to enhance electrochemical performance. Challenging conventional assumptions, surface area alone is not the primary factor driving increased pseudocapacitive performance. The hexagonal hydrotalcite-like structure, characterized by lower skeletal density and larger basal plane spacing, outperforms the monoclinic cobalt carbonate hydroxide structure, achieving an order of magnitude higher capacitance. In situ X-ray absorption spectroscopy provides critical insights into the pseudocapacitive behavior, revealing enhanced accessibility of Co2+ sites for electrochemical oxidation. While monoclinic cobalt carbonate hydroxide exhibits minimal changes in the Co2+ oxidation state, indicative of surface-limited redox activity, the hydrotalcite-like cobalt hydroxides show substantial shifts in the Co K-edge position, highlighting oxidation of Co2+ sites throughout the bulk
Polar questions with narrow focus in Vietnamese: another argument for the bi-clausal analysis
No full textCharacterization of brown carbon absorption in different European environments through source contribution analysis
Get PDFBrown carbon (BrC) is a fraction of organic aerosol (OA) that absorbs radiation in the ultraviolet and short visible wavelengths. Its contribution to radiative forcing is uncertain due to limited knowledge of its imaginary refractive index (k). This study investigates the variability of k for OA from wildfires, residential, shipping, and traffic emission sources over Europe. The Multiscale Online Nonhydrostatic Atmosphere Chemistry (MONARCH) model simulated OA concentrations and source contributions, feeding an offline optical tool to constrain k values at 370 nm. The model was evaluated against OA mass concentrations from aerosol chemical speciation monitors (ACSMs) and filter sample measurements, as well as aerosol light absorption measurements at 370 nm derived from an Aethalometer™ from 12 sites across Europe. Results show that MONARCH captures the OA temporal variability across environments (regional, suburban, and urban background). Residential emissions are a major OA source in colder months, while secondary organic aerosol (SOA) dominates in warmer periods. Traffic is a minor primary OA contributor. Biomass and coal combustion significantly influence OA absorption, with shipping emissions also notable near harbors. Optimizing k values at 370 nm revealed significant variability in OA light absorption, influenced by emission sources and environmental conditions. Derived k values for biomass burning (0.03 to 0.13), residential (0.008 to 0.13), shipping (0.005 to 0.08), and traffic (0.005 to 0.07) sources improved model representation of OA absorption compared to a constant k. Introducing such emission source-specific constraints is an innovative approach to enhance OA absorption in atmospheric models
Eruptive mass loss less than a year before the explosion of superluminous supernovae
Get PDFWe present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at z = 0.4296 and z = 0.3103, respectively, which show an additional set of broad Mg II absorption lines, blueshifted by a few thousands kilometer second−1 with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding circumstellar material (CSM) expelled shortly before the explosion. The peak rest-frame g-band magnitude of SN 2020xga is −22.30 ± 0.04 mag and of SN 2022xgc is −21.97 ± 0.05 mag, placing them among the brightest SLSNe-I. We used high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mg II line profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ∼1.3 × 1016 cm, moving with a maximum velocity of 4275 km s−1, and the shell of SN 2022xgc is located at ∼0.8 × 1016 cm, reaching up to 4400 km s−1. These shells were expelled ∼11 and ∼5 months before the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as a result of luminous-blue-variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyzed optical photometric data and modeled the light curves, considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the mass-shedding limit, powering these SNe with ejecta masses of ∼7 − 9 M⊙. The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing toward stars > 50 M⊙ He-corehence, alternative scenarios such as fallback accretion and CSM interaction are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 107.8 M⊙, a star formation rate of 0.96−0.26+0.47 M⊙ yr−1, and a metallicity of ∼0.2 Z⊙
Nastavitev linije za tehnologijo površinske montaže
Get PDFThis work aims to describe Surface-Mount Technology (SMT) and the process of setting up the production line. The focus is on a detailed explanation of the SMT line, the machines included in the SMT line, and the necessary steps that must be taken to ensure its optimal performance. The main contribution of this work is a description of the line-setting procedure, where each machine is individually set up with Printed Circuit Board (PCB) parameters adjusted to meet each customer\u27s specific technical requirements. For a clearer explanation, a task flow diagram is provided to show the sequence and functions of the machines in the line. Finally, the conclusion highlights the fully assembled PCB, with all components correctly mounted and functioning. These components are identified and explained individually, along with their specific function and purpose.Namen tega dela je opisati tehnologijo površinske montaže (ang. Surface-Mount Technology, SMT) in postopek vzpostavitve proizvodne linije. Poudarek je na podrobni razlagi linije SMT, strojih, ki jih vključuje linija SMT, in potrebnih ukrepih, ki jih je treba sprejeti za zagotovitev njenega optimalnega delovanja. Glavni prispevek tega dela je opis postopka nastavitve linije, pri katerem je vsak stroj individualno nastavljen s parametri tiskanih vezij (ang. Printed Circuit Board, PCB), prilagojenimi tako, da izpolnjujejo posebne tehnične zahteve vsake stranke. Za jasnejšo razlago je na voljo diagram poteka nalog, ki prikazuje zaporedje in funkcije strojev v liniji. Na koncu je predstavljeno popolnoma sestavljeno tiskano vezje z vsemi komponentami, pravilno nameščenimi in delujočimi. Te komponente so opredeljene in razložene posamično, skupaj z njihovo posebno funkcijo in namenom
