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S. K. Verma

Publications and source records attributed to S. K. Verma.

3 recordsLinked to original sources

The dual of the Hardy space associated to the Dunkl-Schrödinger operator with reverse Hölder class potential

Let $\mathcal{L}_k = -Δ_k + V$ be a Schrödinger operator associated with the Dunkl Laplacian $Δ_k$, where $V$ is the non-negative potential function belonging to the reverse Hölder class $RH_k^q(\mathbb{R}^n)$ with $q> \max\{1, \frac{n+2γ}{2}\}$. Here, $2γ$ denotes the degree of homogeneity of the weight function $w_k$, which is determined by the normalized root system and the non-negative multiplicity function $k$. In this paper, we investigate the dual space of the Hardy space $H_{\Tilde{\mathcal{L}}_k}^1$ associated with the Dunkl-Schrödinger operator. The dual space $BMO(\mathcal{L}_k)$ is a subspace of the $BMO_k$ space, which is the Dunkl analogue of the classical $BMO(\mathcal{L})$ space. We provide a characterization for the $BMO(\mathcal{L}_k)$ space. The duality result is obtained via the atomic decomposition of $H_{\Tilde{\mathcal{L}}_k}^1$, where the cancellation condition of atoms depends on the critical radius function associated with the potential $V$. Finally, we establish the boundedness of the uncentered maximal function on the space $BMO(\mathcal{L}_k)$.

math.FA

High Entropy Alloy Catalytic Action on MgH2 Hydrogen Storage Materials

Magnesium hydride (MgH2) is the mostly used material for solid-state hydrogen storage. However, their slow kinetics and highly unfavorable thermodynamics make them unsuitable for the practical applications. The current study describes the unusual catalytic action of a new class of catalyst, a high-entropy alloy (HEA) of Al20Cr16Mn16Fe16Co16Ni16, on the de/re-hydrogenation properties of MgH2. The onset desorption temperature of MgH2 is reduced significantly from 376 °C (for pristine MgH2) to 338 degC when it is catalyzed with a HEA-based catalyst. On the other hand, a fast de/re-hydrogenation kinetics of MgH2 was observed during the addition of HEA-based catalyst. It ab sorbs 6.1 wt% of hydrogen in just 2 minutes at a temperature of 300 degC under 10 atm hydrogen pressure and desorbs ~ 5.4 wt% within 40 minutes. At moderate temperatures and low pressure, the HEA-based catalyst reduced desorption temperatures and improved re-hydrogenation kinetics. Even after 25 cycles of de/re-hydrogenation, the storage capacity of MgH2 catalyzed with the leached version of HEA degrades negligibly.

cond-mat.mtrl-sci

Catalytic action of two-dimensional layered materials (WS2, and MoS2) on hydrogen sorption properties of MgH2

The present study reports the catalytic action of two-dimensional (2D) layered materials (MoS2 and WS2) for improving the de/re-hydrogenation kinetics of MgH2. The MgH2 start desorbing at 277 C with a hydrogen storage capacity of 5.95 wt% in the presence of WS2 catalyst whereas onset desorption temperature of MgH2 catalyzed by MoS2 is 330 C. The MgH2-WS2 absorbed hydrogen ~ 3.72 wt% within 1.3 minutes at 300 C under 13 atm hydrogen pressure and it desorbed ~5.57 wt% within 20 minutes at 300 C under 1 atm hydrogen pressure. We have performed 25 cycles of dehydrogenation (under 1 atm hydrogen pressure at 300 C) and re-hydrogenation (under 13 atm hydrogen pressure at 300 °C) to ensure cyclic stability of catalyzed version of MgH2 where MgH2-WS2 shows better cyclic stability than MgH2-MoS2. MgH2-WS2 also shows the lower reaction activation energy ~117 kJ/mol as compare to other catalyzed and uncatalyzed samples. On the other hand, these catalysts (WS2 and MoS2) do not have any impact on the thermodynamical parameters that is change in enthalpy.

cond-mat.mtrl-sci