Birla Institute of Technology and Science, Pilani – Hyderabad Campus (shortened to BITS Pilani, Hyderabad Campus or BPHC) is a private deemed university campus located in Hyderabad, India. It is one of the four constituent campuses of the BITS Pilani university which has been declared as the Institute of Eminence by the Government of India. BITS Pilani opened its campus in Hyderabad upon invitation by the Government of Andhra Pradesh in 2008 with the first batch of campus graduating in 2012. It is a technical and research institute with focus on Engineering and Sciences.
This work focuses on a posteriori error estimation within a non-conforming framework for the stabilizer-free immersed weak Galerkin finite element method (IWG-FEM) applied to elliptic and parabolic problems with non-smooth coefficients. With an appropriate adaptation of the Helmholtz decomposition of the error, an optimal a posteriori error bound is derived in the weighted H-1-seminorm to address elliptic problems with non-smooth coefficients. For parabolic problems, we analyze a fully discrete scheme that combines the implicit backward Euler time-stepping method with the non-conforming IWG-FEM. A reliable a posteriori error indicator is derived using the time-dependent Helmholtz decomposition in the -norm in time and the weighted -seminorm in space without directly relying on the energy argument. Finally, numerical experiments on various test problems confirm the convergence behavior of the proposed error indicators.
In this article, we consider a newly proposed parameterization of the viscosity coefficient ζ, specifically ζ=ζ̄0ΩmsH, where ζ̄0=ζ0Ωm0s within the coincident f(Q) gravity formalism. We consider a non-linear function f(Q)=−Q+αQn, where α and n are arbitrary model parameters, which is a power-law correction to the STEGR scenario. We find an autonomous system by invoking the dimensionless density parameters as the governing phase-space variables. We discuss the physical significance of the model corresponding to the parameter choices n=−1 and n=2 along with the exponent choices s=0,0.5, and 1.05. We find that model I shows the stable de-Sitter type or stable phantom type (depending on the choice of exponent s) behavior with no transition epoch, whereas model II shows the evolutionary phase from the radiation epoch to the accelerated de-Sitter epoch via passing through the matter-dominated epoch. Hence, we conclude that model I provides a good description of the late-time cosmology but fails to describe the transition epoch, whereas model II modifies the description in the context of the early universe and provides a good description of the matter and radiation era along with the transition phase.
This article presents a comprehensive study of a proposed 40 Gbps hexagonal 16QAM modulator based on four silicon microring modulators (MRMs), demonstrating enhanced performance over classical modulation formats. The MRMs, with a ring length of 53.8 mu m and a coupling ratio (kappa) of 0.2, enable precise optical signal modulation via voltage control. The hexagonal constellation design offers equidistant symbol placement, resulting in improved symbol detection margins and lower bit error rates (BER). Mathematical modeling and constellation analysis confirm the benefits of the hexagonal structure, achieving a BER of 10(-3) at 16.5 dB OSNR. Validated through theoretical analysis and simulation, this green photonic modulator demonstrates robustness and reliability for noise-tolerant optical communication, paving the way for high-efficiency, low-power optical systems.
Microplastic reformation in conjunction with the electrochemical hydrogen evolution has merits for producing value-added chemicals and mitigating environmental pollution. This study presents an approach for producing green hydrogen by electro-oxidizing PET micro-plastics in conjunction with alkaline electrolysis, which produces hydrogen gas at the cathode and a valuable chemical, formic acid, at the anode. In this work, a hierarchically structured NiCe@NiTe heterostructure is deposited on nickel foam via facile hydrothermal and chemical bath deposition techniques for PET plastic up-cycling at industrial scale current densities. Owing to the interface synergistic effect, an abundance of catalytically active sites, and regulated interfacial charge-transfer, the NiCe@NiTe catalyst exhibits superior HER performance with an overpotential of 243 mV to achieve a 100 mA cm-2 current density. In situ operando Raman spectroscopy and impedance spectroscopy show the accelerated catalytic oxidation and abundance of in situ formed NiOOH sites. It enables the oxidation of ethylene glycol (EG) at 1.38 V vs. RHE at 100 mA cm-2, lowering the anodic potential by 250 mV as compared to oxygen evolution. With high selectivity, the NiCe@NiTe catalyst facilitates the conversion of EG to formate with a faradaic efficiency (FE) of 96.5%. Additionally, the FE for hydrogen evolution is more than 93%. The NiCe@NiTe catalyst shows exceptional stability in PET hydrolysate electrolysis (similar to 70 h). Overall, these findings suggest the capability of the NiCe@NiTe catalyst for highly selective and energy-efficient PET upcycling into value-added chemicals and H2-fuel production at industrial scale current densities.
The rational design and optimization of electrode structures are crucial for enhancing catalytic performance for water electrolysis and plastic upcycling, addressing environmental concerns while creating economic value. In this work, a hierarchically structured Ni-Fe3Se4 catalyst was deposited on nickel foam by a chemical bath deposition method. The Ni-Fe3Se4 catalyst exhibits low interfacial resistance and abundance of NiFeOOH active sites, achieving excellent electrocatalytic performance for industrial-level alkaline water electrolysis and electrocatalytic polyethylene terephthalate (PET) upcycling with conversion of ethylene glycol to formate with a faradaic efficiency of 89%. A bi-functional electrolyser using Ni-Fe3Se4 demonstrates excellent stability at 300 mA cm-2 over 42 hours in a 5 M KOH electrolyte. Interestingly, the Ni-Fe3Se4 catalyst shows the simultaneous anodic electro-upcycling of PET hydrolysate and cathodic H2 production at industrial scale current densities for 50 hours, ensuring sustained performance for transforming waste into value-added products such as H2-gas, formate, and terephthalate.
