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The relaxation systems are an important subclass of the passive systems that arise naturally in applications. We exploit the fact that they have highly structured state-space realisations to derive analytical solutions to some simple H-infinity type optimal control problems. The resulting controllers are also relaxation systems, and often sparse. This makes them ideal candidates for applications i

This paper proposes a convex approach to the Frisch-Kalman problem that identifies the linear relations among variables from noisy observations. The problem was proposed by Ragnar Frisch in 1930s, and was promoted and further developed by Rudolf Kalman later in 1980s. It is essentially a rank minimization problem with convex constraints. Regarding this problem, analytical results and heuristic met

Machine and reinforcement learning (RL) are increasingly being applied to plan and control the behavior of autonomous systems interacting with the physical world. Examples include self-driving vehicles, distributed sensor networks, and agile robots. However, when machine learning is to be applied in these new settings, the algorithms had better come with the same type of reliability, robustness, a

In this paper we consider adaptive distributed stabilization for uncertain multivariable linear systems with a time-varying diagonal matrix gain. We show that an unknown system matrix being an M-matrix is a sufficient condition to ensure uncertain linear systems to be stabilizable by matrix high gains, and derive a threshold condition to ensure exponential stability of uncertain linear systems sta

The physical processes and time scales underlying the evolution of surface tension in atmospheric solution droplets are largely unaccounted for in present models describing cloud droplet formation. Adsorption of surface-active molecules at the surface of a solution droplet depresses the droplet surface tension but also depletes solute from the droplet bulk, which have opposing and sometimes cancel

In an increasingly connected world where all manner of devices can communicate over the Internet, conventional methods for developing GUIs (Graphical User Interfaces) are insufficient. For systems of such devices, it must be possible to develop the system itself independently from its GUI(s). In this paper, we present an approach for developing GUIs towards already deployed, or "live", service-bas

Fast and accurate homography estimation is essential to many computer vision applications, including scene degenerate cases and planarity detection. Such cases arise naturally in man-made environments, and failure to handle them will result in poor positioning estimates. Most modern day consumer cameras are affected by some level of radial distortion, which must be compensated for in order to get

Time-critical networks require strict delay bounds on the transmission time of packets from source to destination. Routes for transmissions are usually statically determined, using knowledge about worst-case transmission times between nodes. This is generally a conservative method, that guarantees transmission times but does not provide any optimization for the typical case. In real networks, the

Connecting calendar ages to radiocarbon (C) ages, i.e. constructing a calibration curve, requires C samples that represent, or are closely connected to, atmospheric C values and that can also be independently dated. In addition to these data, there is information that can serve as independent tests of the calibration curve. For example, information from ice core radionuclide data cannot be directl

Assessing the transport of natural radionuclides in the atmosphere provides a powerful tool to study air mass circulation. Here, we investigated the seasonal atmospheric distribution of the naturally produced 7Be in surface air over Europe between 40° N and 68° N during the period 1975–2018. The results suggest that the inter-annual variability of 7Be reflects production rates of the radionuclide

Radiocarbon (C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become availab

The research area of climate field reconstructions has developed strongly during the past 20 years, motivated by the need to understand the complex dynamics of the earth system in a changing climate. Climate field reconstructions aim to build a consistent gridded climate reconstruction of different variables, often from a range of climate proxies, using either statistical tools or a climate model

The sun is the most important energy source for the Earth’s climate system, however, influences of solar variations on climate are not fully understood. Studying past solar activity can improve our understanding of what role the sun plays in Earth’s climate. Cosmogenic radionuclides, such as 10Be in ice cores, are powerful tools to reconstruct past solar activity before the period of direct telesc

10Be in ice cores has been instrumental for reconstructing past changes in solar activity prior to direct observations. For a robust use of these records, it is pivotal to understand the 10Be transport and deposition. However, there are only few high-resolution seasonal 10Be data longer than one full solar cycle (11 years) that could enable a quantification of the influences of atmospheric circula

Land and climate interact in complex ways through changes in forcing and multiple biophysical and biogeochemical feedbacks across different spatial and temporal scales. This chapter assesses climate impacts on land and land impacts on climate, the human contributions to these changes, as well as land-based adaptation and mitigation response options to combat projected climate changes.

Stratospheric aerosol has long been seen as a pure mixture of sulfuric acid and water. Recent measurements, however, found a considerable carbonaceous fraction extending at least 8 km into the stratosphere. This fraction affects the aerosol optical depth (AOD) and the radiative properties, and hence the radiative forcing and climate impact of the stratospheric aerosol. Here we present an investiga

Several climate oscillations have been reported from the early Holocene superepoch, the best known of which is the Preboreal oscillation (PBO). It is still unclear how the PBO and the number of climate oscillations observed in Greenland ice cores and European terrestrial records are related to one another. This is mainly due to uncertainties in the chronologies of the records. Here, we present new

Here we report new reconstructions of winter temperature and summer moisture during the past millennium in southeastern Sweden, based on stable-isotope data from a composite tree-ring sequence, that further enhances our knowledge and understanding of seasonal climate variability in the Northern Hemisphere over the past millennium. Key features of these new climate proxy records include evidence fo

Knowledge on the occurrence rate of extreme solar storms is strongly limited by the relatively recent advent of satellite monitoring of the Sun. To extend our perspective of solar storms prior to the satellite era and because atmospheric ionization induced by solar energetic particles (SEPs) can lead to the production of odd nitrogen, nitrate spikes in ice cores have been tentatively used to docum