The advent of digital computing in the 1950s sparked a revolution in the science of weather and climate. Meteorology, long based on extrapolating patterns in space and time, gave way to computational ...methods in a decade of advances in numerical weather forecasting. Those same methods also gave rise to computational climate science, studying the behaviour of those same numerical equations over intervals much longer than weather events, and changes in external boundary conditions. Several subsequent decades of exponential growth in computational power have brought us to the present day, where models ever grow in resolution and complexity, capable of mastery of many small-scale phenomena with global repercussions, and ever more intricate feedbacks in the Earth system. The current juncture in computing, seven decades later, heralds an end to what is called Dennard scaling, the physics behind ever smaller computational units and ever faster arithmetic. This is prompting a fundamental change in our approach to the simulation of weather and climate, potentially as revolutionary as that wrought by John von Neumann in the 1950s. One approach could return us to an earlier era of pattern recognition and extrapolation, this time aided by computational power. Another approach could lead us to insights that continue to be expressed in mathematical equations. In either approach, or any synthesis of those, it is clearly no longer the steady march of the last few decades, continuing to add detail to ever more elaborate models. In this prospectus, we attempt to show the outlines of how this may unfold in the coming decades, a new harnessing of physical knowledge, computation and data. This article is part of the theme issue 'Machine learning for weather and climate modelling'.
Eutrophication, or excessive nutrient enrichment, threatens water resources across the globe. We show that climate change–induced precipitation changes alone will substantially increase (19 ± 14%) ...riverine total nitrogen loading within the continental United States by the end of the century for the “business-as-usual” scenario. The impacts, driven by projected increases in both total and extreme precipitation, will be especially strong for the Northeast and the corn belt of the United States. Offsetting this increase would require a 33 ± 24% reduction in nitrogen inputs, representing a massive management challenge. Globally, changes in precipitation are especially likely to also exacerbate eutrophication in India, China, and Southeast Asia. It is therefore imperative that water quality management strategies account for the impact of projected future changes in precipitation on nitrogen loading.
The chiral oxazoline motif is present in many ligands that have been extensively applied in a series of important metal-catalyzed enantioselective reactions. This Review aims to provide a ...comprehensive overview of the most significant applications of oxazoline-containing ligands reported in the literature starting from 2009 until the end of 2018. The ligands are classified not by the reaction to which their metal complexes have been applied but by the nature of the denticity, chirality, and donor atoms involved. As a result, the continued development of ligand architectural design from mono(oxazolines), to bis(oxazolines), to tris(oxazolines) and tetra(oxazolines) and variations thereof can be more easily monitored by the reader. In addition, the key transition states of selected asymmetric transformations will be given to illustrate the features that give rise to high levels of asymmetric induction. As a further aid to the reader, we summarize the majority of schemes with representative examples that highlight the variation in % yields and % ees for carefully selected substrates. This Review should be of particular interest to the experts in the field but also serve as a useful starting point to new researchers in this area. It is hoped that this Review will stimulate both the development/design of new ligands and their applications in novel metal-catalyzed asymmetric transformations.
End-functionalised polymer grafted nanoparticles (PGNs) form bonds when their coronas overlap. The bonded interactions between the overlapping PGNs depend on the energy of the bonds (
U
). In the ...present study, oscillatory deformation imposed on a simple system with interacting PGNs placed on the vertices of a triangle is employed to examine the local dynamics as a function of energy of the bonds and the frequency of oscillation relative to the characteristic rupture frequency,
ω
0
= 2π
ν
exp(−
U
/
k
B
T
), of the bonds. In particular, the effect of functional anisotropy is studied by introducing bonds of two different energies between adjacent PGNs. A multicomponent model developed by Kadre and Iyer,
Macromol. Theory Simul.
, 2021,
30
, 2100005, that combines the features of effective interactions between PGNs, self-consistent field theory and master equation approach to study bond kinetics is employed to obtain the local dynamics. The resulting force-strain curves are found to exhibit a simple broken symmetry where
F
x
(
γ
,
&z.ggrda;
) ≠ −
F
x
(−
γ
,−
&z.ggrda;
) and
F
y
(
γ
,
&z.ggrda;
) ≠
F
y
(−
γ
,−
&z.ggrda;
) in systems with functional anisotropy. Fourier analysis of the dynamic response reveals that functional anisotropy leads to finite even harmonic terms and systematic variation of both the elastic and dissipative response from that of the isotropic systems. Furthermore, the intra-cycle variations in the strain stiffening and shear thickening ratios obtained from the analysis indicate that functional anisotropy leads to anisotropic nonlinear response.
Dynamics depends on anisotropy introduced
via
energy of bonded interactions between end-functionalised polymer grafted nanoparticles (PGNs).
Asymmetric A3 coupling has emerged as an important class of reactions to synthesise chiral propargylamines. In this tutorial review, an up to date progress of this reaction, with significant recent ...advancements in terms of ligand development, is presented. Applications of asymmetric A3 coupling in natural product synthesis and in tandem processes are also discussed.
Asymmetric A3 coupling has emerged as an important class of reactions to synthesise chiral propargylamines.
Axially chiral P,N-ligands have emerged as a powerful ligand class over time with significant recent advances in terms of their synthesis, resolution, and applications to a broad range of ...synthetically important asymmetric transformations. This Perspective describes the evolution of this ligand class from Quinap, the first member of the family, to the most recent UCD-Phim/StackPhim analogues, a journey with many “twists and turns”.
Torsors on semistable curves and degenerations Balaji, V
Proceedings of mathematical science/Proceedings of the Indian Academy of Sciences. Mathematical sciences,
06/2022, Letnik:
132, Številka:
1
Journal Article
Recenzirano
Odprti dostop
In this paper, we answer two long-standing questions on the classification of
G
-torsors on curves for an almost simple, simply connected algebraic group
G
over the field of complex numbers. The ...first is the construction of a flat degeneration of the moduli of
G
-torsors on smooth projective curves when the smooth curve degenerates to an irreducible nodal curve and the second one is to give an intrinsic definition of (semi)stability for a
G
-torsor on an
irreducible projective nodal curve
. A generalization of the classical Bruhat–Tits group schemes to two-dimensional regular local rings and an application of the geometric formulation of the McKay correspondence provide the key tools.
Adaptive hill-climbing MPPT algorithms have superior performance as opposed to their conventional counterparts under medium-high irradiance. However, the performance of these hill-climbing algorithms ...remains mostly unknown under low irradiance condition. The low irradiance conditions are prominent in tropical countries during rainy seasons and niche PV applications. Additionally, several thin-film photovoltaic (PV) technologies have better efficiency under low irradiance conditions. Hence, the optimum operation of MPPT algorithms under low irradiance conditions is vital. In the real-time implementation, MPPT algorithms can fail to detect the incremental changes in voltage and current under low irradiance conditions. Hence, analog to digital converter (ADC) resolution becomes a critical constraint that governs the performance of hill-climbing (HC) MPPT algorithms. This work entails a detailed calculation to determine the perturbation step-sizes of the MPPT algorithms under a wide range of irradiance. Two distinct perturbation step-sizes are determined corresponding to the minimum and optimum change in voltage and current due to perturbation, that is sensed by the ADC. The authors also defined a general expression to determine the optimum digitized step-size for duty-based perturb and observe algorithm under low irradiance condition. This expression is formulated by considering the resolution of the ADC and the desirability of keeping the power oscillations at an acceptable level. Finally, the performance of eight hill-climbing algorithms for two distinct step-sizes is analyzed on a small-scale experimental prototype under both uniform and sudden changes in low values of irradiance. The statistical analysis validates that the adaptive HC drift-free MPPT algorithm outperforms other HC algorithms when implemented with the optimum perturbation step-size under low irradiance conditions.
•The perturbation step-size should be evaluated based on the resolution of the analog to digital converter (ADC) of the controller.•The performance of the HC algorithms are similar when implemented with the large perturbation step-size which is determined corresponding to the resolution of the ADC.•Among P&O, INC and INR algorithms, the P&O algorithm has the highest tracking speed due to the use of duty as a perturbation parameter which helps in reducing the tracking time.•The perturbation step-size should be optimized for the worst condition, i.e. analysis should be carried out for the lower end of irradiance.•The proposed methodology to determine the optimum step-size helped in lowering the steady-state oscillations and maintaining a good tracking speed.
•Proposed framework combines grid-side & demand-side measures to enhance resilience.•Monte-Carlo based probabilistic earthquake hazard model is developed.•Three-dimensional hardening methodology is ...proposed to enhance system resilience.•Case study is conducted on practical distribution system of Dehradun, India.
The electrical distribution grid is unremittingly vulnerable to natural disasters. Many researchers propose strategies mainly based on grid-side solutions to improve critical load's survivability during the targeted emergency period. However, the main agenda of resilience enhancement is to improve the overall system resilience. Therefore, this paper proposes a proactive framework that combines the grid-side and demand-side solutions to enhance the overall system resilience. Here, the grid-side approach presents optimal hardening of the distribution grid by using resilient energy storage units (ESUs), underground cables (UCs), and the demand-side by using home battery inverters (HBIs) & its communication infrastructure. For resilient hardening against earthquakes, it is essential to identify it's all possible occurrences. Therefore, a Monte-Carlo-based probabilistic earthquake hazard model is developed through which the vulnerability is characterized using the peak ground acceleration (PGA) model and fragility curves. For optimized hardening investments, the vulnerable zones of the system are identified via clustering algorithms. With the formulated mixed-integer nonlinear problem, the optimal ESUs and UCs are identified for each cluster. The proposed methodology is tested on a real-world 156-bus distribution system of Dehradun district, India, under seismic zone IV.
This study focuses on the microstructure and mechanical properties while incorporating zirconium oxide and coconut shell ash particles in Al 6082 matrix composites. Zirconium oxide and coconut shell ...ash particles were varied from 0 to 10% and fabricated by stir casting process. The fabricated composites were subjected to X-ray diffractometer and SEM to confirm the presence of zirconium oxide and coconut shell ash particles. Hardness, density, impact strength, tensile strength, ductility and flexural strength analysis were carried on the developed hybrid composites to study the mechanical properties of composites. Scanning electron microscopy study were carried on the fractured tensile and impact test specimen to analyse the fracture mechanism.
•ZrO2 and CSA reinforced Al hybrid composites were fabricated by stir casting.•Addition of ZrO2 and CSA increased and decreased the hardness respectively.•Tensile & yield strength of composites increased by 23.17% & 26.78% respectively.•Increase by 9.52% and decrease by 5.95% in flexural strength were observed.•Dimples, pits, necking, particle cracks etc. are seen in the fractured specimen.
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