Design, modelisation and optimisation of high efficiency miniature E-field probes performed on 3D ceramic prisms for SAR evaluation

A comprehensive design methodology is proposed in this paper in order to optimise E-field probes used for evaluating the specific absorption ratio within liquid equivalent tissues exposed to radiofrequency signals. Hybrid analysis approaches are investigated, combining both electromagnetic (three dimensional) and circuit simulators. This design environment can therefore be considered for enhancing E-field detectors’ performances in terms of sensitivity, isotropy, dimensions and shape. Comparisons between simulations and measurements are presented and discussed.     

Electricity System Reliability Issues During Energy System Transformation

Energy system transformation in the electric energy industry encompasses a broad range of changes in how primary energy is produced, transported, converted, priced, and delivered to consumers. Minnesota Power (ALLETE) is responding to these changes by implementing strategies like our EnergyForward resource strategy. EnergyForward describes the transition to a diverse and balanced generation portfolio that meets customers' desires for clean, safe, flexible, and affordable electricity.     

Large‐Scale Diffusion Barriers from CVD Grown Graphene

Graphene has been long thought of as a perfect barrier material due to its impermeability to all gases as well as mechanical and chemical durability. Moreover, graphene layers are transparent and conductive, significantly widening the field of potential applications beyond simple barrier coatings. However, it is very challenging to realize such barriers on a macro­scopic scale as immaculate large area films are not available. In this work, a highly effective oxygen gas barrier made from multiple layers of chemical vapor deposited graphene is presented. The individual graphene layers are stacked using a modified polymer‐assisted transfer method, avoiding polymer residue yielding an oxygen‐tight arrangement. A stack of three layers of graphene transmitted 6.9 cm³ m⁻² d⁻¹ of O₂ which corresponds to 1.10 × 10⁻¹⁷ cm³ cm/cm² s (cm Hg) when normalized to thickness and pressure. This is several orders of magnitude better than any macroscale graphene coating reported to date and performs on a level that can compete with most modern coatings while being much thinner and conductive.     

Nanoscale FeS2 (Pyrite) as a Sustainable Thermoelectric Material

We have synthesized undoped, Co-doped (up to 5%), and Se-doped (up to 4%) FeS₂ materials by mechanical alloying in a planetary ball mill and investigated their thermoelectric properties from room temperature (RT) to 600 K. With decreasing particle size, the undoped FeS₂ samples showed higher electrical conductivity, from 0.02 S cm^?1 for particles with 70 nm grain size up to 3.1 S cm^?1 for the sample with grain size of 16 nm. The Seebeck coefficient of the undoped samples showed a decrease with further grinding, from 128 μV K^?1 at RT for the sample with 70-nm grains down to 101 μV K^?1 for the sample with grain size of 16 nm. The thermal conductivity of the 16-nm undoped sample lay within the range from 1.3 W m^?1 K^?1 at RT to a minimal value of 1.2 W m^?1 K^?1 at 600 K. All doped samples showed improved thermoelectric behavior at 600 K compared with the undoped sample with 16 nm particle size. Cobalt doping modified the p-type semiconducting behavior to n-type and increased the thermal conductivity (2.1 W m^?1 K^?1) but improved the electrical conductivity (41 S cm^?1) and Seebeck coefficient (-129 μV K^?1). Isovalent selenium doping led to a slightly higher thermal conductivity (1.7 W m^?1 K^?1) as well as to an improved electrical conductivity (26 S cm^?1) and Seebeck coefficient (110 μV K^?1). The ZT value of FeS₂ was increased by a factor of five by Co doping and by a factor of three by Se doping.     

Sicherheit und rechtliche Herausforderungen in Bezug auf Cloud Computing und Kritische Infrastruktur-IT

The prevalence of machine-to-machine (M2M) will continue to increase because of the connection and interlinking of services in the domain of critical infrastructures (e.g. “smart grids”, traffic management or surveillance systems). This is leading to a constant rise of required computational and storage resources. As field systems typically offer only limited computing and storage capabilities and as many applications require a global view to integrated data from various devices, a natural location to store data and perform analysis tasks is in the Cloud, where an abundance of flexible resources can be used. However, this results in a number of security and privacy challenges in combination with some legal and technical considerations that need to be addressed. In this paper, we will investigate and categorize the above challenges associated with using the Cloud in a critical infrastructure and M2M context.     

Stacked GaAs quantum dots fabricated by refilling of self-organized nanoholes: optical properties and post-growth annealing

We study the photoluminescence and impact of post-growth annealing of stacked, strain-free GaAs quantum dots fabricated by refilling of self-organized nanoholes using molecular beam epitaxy. Temperature- and power-dependent photoluminescence studies reveal an excellent optical quality of the quantum-dot stack. After high-temperature post-growth annealing only slight blueshifts and an increase in full width at half-maximum of the photoluminescence peak are observed, indicating very high-temperature stability and crystalline quality of the stacked GaAs quantum-dot structure.