5,414 research outputs found
Theoretical spectroscopic studies of the atomic transitions and lifetimes of low-lying states in Ti IV
The astrophysically important electric quadrupole (E2) and magnetic dipole
(M1) transitions for the low-lying states of triply ionized titanium (Ti IV)
are calculated very accurately using a state-of-art all-order many-body theory
called Coupled Cluster (CC) theory in the relativistic frame-work. Different
many-body correlations of the CC theory has been estimated by studying the core
and valence electron excitations to the unoccupied states. The calculated
excitation energies of different states are in very good agreement with the
measurements. Also we compare our calculated electric dipole (E1) transition
amplitudes of few transitions with recent many-body calculations by different
groups. We have also carried out the calculations for the lifetimes of the
low-lying states of Ti IV. A long lifetime is found for the first excited
3d state, which suggested that Ti IV may be one of the useful
candidates for many important studies. Most of the results reported here are
not available in the literature, to the best of our knowledge.Comment: 15 pages submitted to J. Phys.
Combined Effect of Multistage Processing and Treatment Methods on the Physical, Chemical, and Microstructure Properties of Recycled Concrete Aggregates
This research aims to examine the effects of multi-stage processing on reducing the old cement fractions and enhancing the quality of CRA (concrete recycled aggregate). The investigation involves the use of demolished concrete debris and subsequent treatments in both single and multi-stage processes. The recycled aggregates (RA) were obtained using a multi-stage jaw crushing process followed by utilising natural aggregate, untreated RA, RA treated with hydrochloric acid and sodium silicate immersion (single stage treatment) and RA treated with mechanical scrubbing and sodium silicate immersion in two separate stages (multi-stage treatment). The subsequent phase of the experimental inquiry involves assessing the physical attributes of both treated and untreated RA. This is followed by conducting microstructural examinations utilising techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry-differential thermal analysis (TG-DTA). The findings indicate that employing a two-step process, involving mechanical abrasion followed by immersion in sodium silicate, yields high-quality CRA. This conclusion is reinforced by the favourable physical performance observed. The water absorption values of CRA were lowered by 78% through single-stage treatments such as immersion in hydrochloric acid. The similar treatment is found to show densest concrete with Ca/Si ratio reduced to around 81% to that of untreated CRA. Additionally, for single stage treated CRA samples, microstructural study using FTIR verified the creation of additional hydration products, whereas for two stages treated CRA specimens, TGA analysis demonstrated the formation of stable CSH. According to the findings, it is advised to use a multi-stage process of jaw crushing, then treating it with mechanical abrasion and sodium silicate. This has the ability to improve the physical, chemical, and microstructural properties of CRA
Accurate estimations of circumstellar and interstellar lines of quadruply ionized vanadium using the coupled cluster approach
Accurate {\it ab initio} calculations have been carried out to study the
valence electron removal energies and oscillator strengths of astrophysically
important electromagnetic transitions of quadruply ionized vanadium, .
Many important electron correlations are considered to all-orders using the
relativistic coupled-cluster theory. Calculated ionization potentials and fine
structure splittings are compared with the experimental values, wherever
available. To our knowledge, oscillator strengths of electric dipole
transitions are predicted for the first time for most of the transitions. The
transitions span in the range of ultraviolet, visible and near infrared regions
and are important for astrophysical observations.Comment: Submitted in Astrophysical
Optimizing Robustness and Invisibility in Digital Image Watermarking: A SVM-Based Multi-Level DWT and SVD Approach
This research introduces a new digital image watermarking approach that utilizes discrete wave transformation (DWT), Support vector machine, and singular value decomposition. The method improves robustness under various assault situations by using the SVM classifier during watermark extraction. Multi-level DWT splits the host picture into sub-bands when embedding, and the coefficients are used as input for SVM. After SVD, the scaling factor embeds the watermark. Comparing the proposed approach to existing research under various attacks, the experimental findings demonstrate that it strikes an equilibrium between robustness and invisibility for watermarks of varying sizes. Support Vector Machine is a contemporary category of machine learning techniques that is extensively employed for the purpose of solving classification problems
Relativistic calculations of the lifetimes and hyperfine structure constants in Zn
This work presents accurate {\it ab initio} determination of the magnetic
dipole (M1) and electric quadrupole (E2) hyperfine structure constants for the
ground and a few low-lying excited states in Zn, which is one of
the interesting systems in fundamental physics. The coupled-cluster (CC) theory
within the relativistic framework has been used here in this calculations. Long
standing demands for a relativistic and highly correlated calculations like CC
can be able to resolve the disagreements among the lifetime estimations
reported previously for a few low-lying states of Zn. The role of
different electron correlation effects in the determination of these quantities
are discussed and their contributions are presented.Comment: 9 pages, 1 figure. submitted to J. Phys. B Fast Trac
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