Sökresultat

Contaminated sites constitute a global problem as they pollute important freshwater systems at a local scale. To effectively address these sites for remediaton, we must first characterize the sites in order to gain an understanding of the geological setting. This step is crucial as it helps determine groundwater flow pathways and the dynamics of surface water-groundwater exchange within these syst

We consider a system of equations that model the temperature, electric potential and deformation of a thermoviscoelastic body. A typical application is a thermistor; an electrical component that can be used e.g. as a surge protector, temperature sensor or for very precise positioning. We introduce a full discretization based on standard finite elements in space and a semi-implicit Euler-type metho

The treatment of the stochastic linear quadratic optimal control problem with finite time horizon requires the solution of stochastic differential Riccati equations. We propose efficient numerical methods, which exploit the particular structure and can be applied for large-scale systems. They are based on numerical methods for ordinary differential equations such as Rosenbrock methods, backward di

We consider high-order splitting schemes for large-scale differential Riccati equations. Such equations arise in many different areas and are especially important within the field of optimal control. In the large-scale case, it is critical to employ structural properties of the matrix-valued solution, or the computational cost and storage requirements become infeasible. Our main contribution is th

We consider approximations to the solutions of differential Riccati equations in the context of linear quadratic regulator problems, where the state equation is governed by a multiscale operator. Similarly to elliptic and parabolic problems, standard finite element discretizations perform poorly in this setting unless the grid resolves the fine-scale features of the problem. This results in unfeas

We consider operator-valued differential Lyapunov and Riccati equations, where the operators B and C may be relatively unbounded with respect to A (in the standard notation). In this setting, we prove that the singular values of the solutions decay fast under certain conditions. In fact, the decay is exponential in the negative square root if A generates an analytic semigroup and the range of C ha

We consider differential Lyapunov and Riccati equations, and generalized versions thereof. Such equations arise in many different areas and are especially important within the field of optimal control. In order to approximate their solution, one may use several different kinds of numerical methods. Of these, splitting schemes are often a very competitive choice. In this article, we investigate the

Major migration events in Holocene Eurasia have been characterized genetically at broad regional scales1–4. However, insights into the population dynamics in the contact zones are hampered by a lack of ancient genomic data sampled at high spatiotemporal resolution5–7. Here, to address this, we analysed shotgun-sequenced genomes from 100 skeletons spanning 7,300 years of the Mesolithic period, Neol

Forest ecosystems play a crucial role in the production and protection of economic, social, and environmental values. To understand current challenges and trajectories shaping future strategies within the Nordic forest sector, it is important to map and trace past and present policy and governance developments. The core contribution of this short communication is to present an open-access database

Western Eurasia witnessed several large-scale human migrations during the Holocene1–5. Here, to investigate the cross-continental effects of these migrations, we shotgun-sequenced 317 genomes—mainly from the Mesolithic and Neolithic periods—from across northern and western Eurasia. These were imputed alongside published data to obtain diploid genotypes from more than 1,600 ancient humans. Our anal

Med anledning av att två kulturinstitutioner – Världskulturmuseet i Göteborg och Halmstads konsthall – visade utställningar med speltema under sommaren 2023, såg Hedvig Jalhed och Mattias Rylander anledning att reflektera över spelens status i förhållande till konst och kultur av idag. Centralt i deras betraktelse är synen på agens i lek och spel, samt ludik som konstform. Med utgångspunkt i de bä

Armlängds avstånd och konstnärlig frihet är centrala begrepp i svensk kulturpolitik och -förvaltning. I denna artikel resonerar Hedvig Jalhed kring begreppen negativ och positiv frihet i förhållande till konstnärlig verksamhet. Hon problematiserar konstnärers möjlighet till inflytande över varandra och anknyter till Camille Paglias teori om konstnärlig kanon som något som istället för att etablera

Global solar radiation (GSR) prediction capability with a reliable model and high accuracy is crucial for comprehending hydrological and meteorological systems. It is vital for the production of renewable and clean energy. This research aims to evaluate the performance of combined variational mode decomposition (VMD) with a multi-functional recurrent fuzzy neural network (MFRFNN) and quantile regr

With the incorporation of the State Administration for Religious Affairs (SARA) into the Chinese Communist Party’s (CCP) United Front Work Department in 2018, religious affairs have been brought back into the direct control of the Party. While SARA has retained its name, it is no longer an independent state agency. Five further legal measures were introduced from 2019 to 2021. This review essay ex