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Three Approaches of multi-objective economic model predictive control for process systems
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Energy and temperature management in buildings through Multi-Objective Model Predictive Control on a chip
No full textClimate control in buildings involves multiple conflicting objectives, such as energy consumption and occupant comfort, which have to be considered simultaneously during the operation of the climate control system. In this work, the Multi-Objective Model Predictive Control (MOMPC) solution method is further developed through the multiparametric programming approach (mpMOMPC). The MOMPC optimal control problem is reformulated according to the ϵ-constraint method, and the ϵ vector is treated as unknown parameters to generate the control law expressions offline. This reduces online calculations to point location followed by function evaluation, enabling the controller to be implemented through a chip or low-cost hardware. To demonstrate the potential and versatility of the developed mpMOMPC algorithm, three case studies are conducted. Numerical simulation results show that the extreme-value case is the same as the rule-based MPC case and the preference function case results in maximum energy reduction by 20.1% compared to the rule-based MPC case
Gravitational memory meets astrophysical environments: exploring a new frontier through osculations
No full textInfluence of pit geometry and flow conditions on sand pit migration in fluvial systems: insights from flume experiments
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Type-II band-alignment in vertical transition metal-di-chalcogenide heterostructures for near infrared and visible light detection
No full textIn this work, group-6 and group-7 (ReSe2) transition metal-di-chalcogenide (TMD) heterostructures are studied systematically using density functional theory (DFT). Different combinations of ReSe2 and group-6 TMDs are explored to identify the heterostructures with ‘type-II band-alignment’. ReSe2 monolayer is chosen as group-7 TMD because of its dynamic stability. Materials like MoS2, MoSe2, MoTe2, WS2 and WSe2 are chosen as group-6 TMDs. The heterostructures are evaluated in terms of metrics like; type of band-alignment, band-offsets, optical absorption and potential difference across the interface. ReSe2/MoS2, ReSe2/MoSe2 and ReSe2/WS2 heterostructures are identified as materials with ‘type-II band-alignment’ having bandgap values of 0.447 eV, 0.956 eV and 0.684 eV respectively. The identified ‘type-II heterostructures’ show a high absorption coefficient (∼40 × 104 cm−1) in visible-light region of the electromagnetic spectrum. Also, these ‘type-II heterostructures’ show a considerable potential drop across the interface (3.49 eV, for ReSe2/MoS2, heterostructure), which is important for efficient separation of photogenerated carriers into electrons and holes. This potential drop is crucial for limiting the recombination of photogenerated carriers. Furthermore, based on the performance metrics it is shown, among the studied heterostructures, ReSe2/MoS2, ReSe2/MoSe2 and ReSe2/WS2 heterostructures are suitable for light detecting applications in visible-light region of electromagnetic spectrum. Moreover, ReSe2/MoTe2 and ReSe2/WSe2 heterostructures show a ‘type-I band-alignment’
Shear-driven flow in an elliptical enclosure generated by an inner rotating circular cylinder
No full textShear-driven flow between a rotating cylinder and a stationary elliptical enclosure is studied in this paper. Two-dimensional time-dependent Navier-Stokes equations are solved using a meshless method, where interpolations are done with polyharmonic spline radial basis functions. The fluid flow is analyzed for various aspect ratios of the ellipse and eccentric placements of the inner cylinder. Contour plots of vorticity with streamlines, plots of non-dimensional torque, and the angle of eye of the primary vortex are presented in the paper for Reynolds numbers between 200 and 2000. Formation of Moffatt like vortices in the wide-gap region of the model is observed, and some benchmark data are provided for various cases that are simulated. � 2022 Elsevier B.V., All rights reserved
Formic acid decomposition over supported Pd alloy catalysts: role of oxygen in hydrogen production
No full textAqueous formic acid (FA) catalytic dehydrogenation to hydrogen (H2) is a potential green H2 source under ambient conditions (in air). We show that commonly studied Pd nanoparticles supported on CeO2 provide low H2 selectivity and TOF (10%; 20 h−1) against water (H2O) formation from the aqueous FA reaction under ambient conditions. Further, this study explains how Ag alloying of Pd and interfacial sites affect the selective production of H2 from FA with rates and apparent energy barrier measurements without promoters in the liquid phase under ambient conditions. The presence of a high surface coverage of oxygen on Pd-CeO2 decreases the H2 selectivity and promotes H2O formation from the aqueous FA reaction at a temperature as low as 298 K. However, 0.5 PdAg-CeO2 (the atomic ratio of Pd and Ag is 0.5) catalysts provide a higher H2 selectivity (22%) and TOF (178 h−1) when compared to Pd-CeO2 (10%; 20 h−1) at 298 K. Despite the changes in H2 TOF and selectivity, Pd-CeO2 and 0.5 PdAg-CeO2 present the C-H bond activation of formate as a kinetically relevant step for H2 production from FA over a formate covered surface. Even in the presence of an oxidative environment, Ag increases the surface coverage of reduced Pd on 0.5 PdAg-CeO2 compared to Pd-CeO2, and these electronic modifications of PdAg compared to Pd decrease the apparent activation barrier over 0.5 PdAg-CeO2 (8 ± 4 kJ mol−1) compared to Pd-CeO2 (25 ± 3 kJ mol−1) and increase the H2 TOF/selectivity from the FA reaction. Similar-sized PdAg nanoparticles on CeO2 and TiO2 provide comparable rates of H2 production from the FA reaction independent of the identity of the support due to negligible differences in the support basicity. The mechanistic insights of H2 production from FA in the presence of surface oxygen on PdAg catalysts and the derived rate law will aid in the rational design of future catalysts for aerobic H2 production
Tangent cones of concatenated numerical semigroups
No full textWe study the tangent cone at the origin and the Hilbert series for a family of numerical semigroups generated by concatenation of arithmetic sequences. We prove that all the concatenation classes have Cohen-Macaulay tangent cones except the symmetric class, however, the symmetric class does satisfy Rossi's conjecture