Quasi-strongly regular graphs form a significant generalization of strongly regular graphs. We study the eigenvalues of a family of such graphs, Γ_H(G), constructed from a finite group G and a subgroup H. Our main results include a sufficient condition for Γ_H(G) to be integral and an explicit computation of its entire spectrum when H is normal, revealing that the spectrum in this case depends only on |G| and the index [G:H].
Y1−xCexMnO3 (x = 0.0, 0.05, 0.10) manganites, were investigated to correlate structural distortion, defect chemistry, and multifunctional properties. Rietveld-refinement confirms the retention of the hexagonal P63cm structure upon Ce doping, accompanied by anisotropic lattice distortion, increased crystallite size, and microstrain. XPS indicates the coexistence of Ce3+/Ce4+ and Mn3+/Mn4+ mixed-valence states along with oxygen vacancies. Optical band gap reduced from 1.42 to 1.36 eV with increasing Ce content, suggesting defect-induced band tailing. Magnetic measurements reveal a suppression of the Néel temperature from ∼72 K to 56 K, which indicates short-range ferromagnetic correlations. Curie-Weiss analysis demonstrates a reduction in antiferromagnetic interaction and magnetic frustration, confirming a transition toward a magnetically inhomogeneous state. Isothermal magnetization supports the coexistence of competing antiferromagnetic superexchange and ferromagnetic double-exchange interactions. Bound magnetic polaron analysis suggests defect-mediated magnetic clustering upon Ce substitution. Moreover, 10% Ce doped YMnO3, achieving ∼79% methylene blue degradation within 180 min compared to ∼45% for YMnO3. These results provide important insights into the development of advanced oxide materials for optoelectronic and water remediation applications.
Abstract Incompatibility between organic asphalt-coated aggregates and the inorganic cement matrix led to a reduction in mechanical strength in reclaimed asphalt pavement (RAP)–based concrete mixtures; however, the fundamental chemical mechanisms governing this behavior remain insufficiently understood. In this study, a fundamental approach was used to understand the leachate compounds within the alkaline cement solution, and the effect of asphalt-coated aggregates on cement hydration was investigated using a novel suspension technique. Fine RAP aggregates with different levels of asphalt oxidation (high, moderate, and low) were used. A suspension system was prepared using fine RAP aggregates mixed with cement powder at a 1 ∶ 1 weight ratio and deionized water at a liquid-to-solid ratio of 10 ∶ 1 . The mixture was continuously stirred at 30 ± 2 revolutions/min (rpm) for 24, 48, 72, and 96 h, followed by vacuum filtration to obtain and isolate the solid and liquid phases for subsequent analysis. The liquid cement solution was analyzed to determine the leachate compounds using Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma optical emission spectroscopy (ICP-AES), and pH measurements. The solid (cement powder sample) was further analyzed to understand the variation in cement hydration products caused by asphalt-coated aggregates in the suspension using thermogravimetric analysis (TGA), FTIR, and X-ray diffraction (XRD) analysis. The results showed elevated calcium concentrations and reduced sodium and barium mobility in the cement pore solution, accompanied by a decrease in pH, attributed to the formation of calcium–carboxylate complexes and neutralization of alkalinity by oxidized asphalt functional groups. FTIR analysis of the liquid phase indicated the transformation of carbonyl groups into carboxylate species. Solid-phase analyses exhibited reduced portlandite and bound water content, delayed C─S─H formation, and weakened Si─O stretching vibrations, indicating inhibited early cement hydration in the presence of asphalt-coated aggregates. These findings indicate that chemical interaction between aged asphalt coatings and the cement matrix alters ionic equilibrium and inhibits early hydration reactions.
This study evaluates the operational efficiency and operational fuel-energy sustainability of 37 Indian State Transport Undertakings (STUs) using cross-sectional data for FY2022–23. A three-stage framework is developed to account for heterogeneity in fleet composition, benchmark operational performance, and assess energy sustainability. First, Shannon entropy is applied to propulsion mix, bus-type composition, and fleet-age structure to quantify fleet diversification, followed by Ward's hierarchical clustering to identify STUs with similar diversification profiles. Second, a slack-based measure data envelopment analysis (SBM-DEA) is implemented using group-specific and pooled frontiers to estimate Group Technical Efficiency (GTE), Meta-frontier Technical Efficiency (MTE), and the Group Frontier Gap Ratio (GFGR). GFGR values remain close to unity for most operators, indicating relatively limited group-to-pooled benchmark separation, although notable exceptions occur. Monte Carlo perturbation analysis further indicates that the efficiency estimates of MSRTC and SKNT are comparatively sensitive to small variations in the observed data. Third, an Operational Fuel Energy Sustainability Index (OESI) integrates the Energy Intensity Index (EII), Avoidable Energy Use Index (AEUI), and Cleaner-Propulsion Adoption Index (CPAI). OESI scores range from 0.042 to 0.969, revealing substantial variation across STUs. The three components are only weakly correlated, while leave-one-component-out analysis indicates that each contributes non-redundant information to the composite ranking. Cleaner-propulsion adoption does not necessarily coincide with favourable operational energy performance, as some operators with high CPAI continue to exhibit relatively high energy intensity or avoidable energy use. Alternative weighting schemes and a restricted-sample analysis excluding operators with substantial electric-bus penetration show that the principal OESI ranking pattern remains broadly stable. The framework supports operator-specific performance assessment alongside cleaner-fleet transition policies.
Although, the influence of the base-isolation (BI) system on the structural performance of building structures is well understood, but the influence of the soil-structure interaction (SSI) on the performance of the BI buildings is remains unclear. Additionally, rapid urbanization, the increasing rate of building construction, and the frequent occurrence of seismic events necessitate the investigation of the frequency-dependent behavior of typical urban building infrastructures equipped with seismic control systems such as base isolation (BI). The present study investigates the effect of the BI system on the seismic performance of low-, intermediate-, and high-rise base-isolated shear buildings considering the SSI. Three different buildings typically found in urban areas with different fundamental structural frequency are considered in the numerical investigation. For a comprehensive study of the earthquake on the building structures with different height (low-rise, intermediate-rise and high-rise buildings), the earthquake records are classified as low-intermediate- and high-frequency earthquakes. The numerical modelling of the building structures is done using lumped-mass model and the parameters of the linearized equivalent BI system are integrated into the model, considering that the BI system behaves like the bottom story of the structural system. For this study, the interaction between the soil and foundation is represented using springs and dashpots considering sway and rocking inertial responses. The seismic responses are compared between isolated and non-isolated cases, considering SSI and non-SSI conditions separately. It is found that, the SSI significantly affects the seismic response of each category of considered building structures, independent of isolated or non-isolated cases. Additionally, the sensitiveness of different types of buildings to different frequency-content earthquake is evident for both isolated and non-isolated scenarios. For all the considered earthquakes, the efficiency of the BI system is observed to be overestimated when SSI effect is neglected.
