Canadian Field Soils I. Mineral Composition by XRD/XRF Measurements

Forty Canadian soils were laboratory tested for the presence of quartz and other minerals using X-ray diffraction/X-ray fluorescence techniques. On average, the highest quartz content was observed in soil samples from sites in Nova Scotia followed by Prince Edward Island sites, whereas soil sample from British Columbia sites had the lowest quartz content. The second most abundant mineral was albite that mainly occurred in soil samples from Ontario and Quebec sites. Illite was the third most abundant and prevailed in soils mainly from British Columbia and New Brunswick sites. Soil samples from British Columbia sites had the highest combined clay and silt content and were composed of illite, albite, kaolinite, and chlorite. The lowest clay content was found in the samples from the Quebec sites. The highest microcline (a potassium feldspar) content was observed in Quebec, Ontario, and Prince Edward Island sites. In contrast to other provinces, samples from Quebec and Ontario sites also included amphibole. Soil samples from Saskatchewan and Manitoba sites also comprised carbonates, i.e., calcite and dolomite. Iron oxides (e.g., goethite) were present in all soils, except the Quebec sites, but their occurrence was rather insignificant.     

Development of a Comprehensive Oxide Scale Failure Diagram

This paper describes a new approach towards the development of a comprehensive oxide scale failure diagram (OSFD) that delineates the mechanical limits of scales for the different types of failure mechanisms. While former diagrams of a similar type were based on relating the critical strain to scale failure to oxide scale thickness, the new approach replaces scale thickness with a comprehensive operational parameter ω_o that summarizes in a multi-level treatment all contributing factors, e.g. physical defect size, interface roughness, scale thickness, Young’s modulus, fracture toughness, etc., that influence failure strain. While this approach should ideally be based on a comprehensive treatment of ω_o using fully implemented coding, further considerations based on the identification of “low-impact” and “high-impact” parameters lead to a simplified OSFD where only the physical defect size is needed. This simplified approach can be used to assess the strain tolerance of oxide scales in industrial operation once the particular diagram has been established from laboratory data.     

<Emphasis Type="Italic">μ</Emphasis>DTNSec: a security layer with lightweight certificates for Disruption-Tolerant Networks on microcontrollers

In Delay/Disruption-Tolerant Networks, man-in-the-middle attacks are easy: due to the store-carry-forward principle, an attacker can simply place itself on the route between source and destination to eavesdrop or alter bundles. This weakness is aggravated in networks, where devices are energy-constrained but the attacker is not. To protect against these attacks, we design and implement μDTNSec, a security layer for Delay/Disruption-Tolerant Networks on microcontrollers. Our design establishes a public key infrastructure with lightweight certificates as an extension to the Bundle Protocol. It has been fully implemented as an addition to μDTN on Contiki OS and uses elliptic curve cryptography and hardware-backed symmetric encryption. In this enhanced version of μDTNSec, public key identity bindings are validated by exchanging certificates using neighbor discovery. μDTNSec provides a signature mode for authenticity and a sign-then-encrypt mode for added confidentiality. Our performance evaluation shows that the choice of the curve dominates the influence of the payload size. We also provide energy measurements for all operations to show the feasibility of our security layer on energy-constrained devices. Because a high quality source of randomness is required, we evaluated the random number generators by the AT86RF231 radio, its successor AT86RF233, and one based on the noise of the A/D converter. We found that only AT86RF233 provides the required quality.     

Spatio-Temporal Correlations in Memristive Crossbar Arrays due to Thermal Effects

Memristive valence change memory (VCM) cells show a strong non-linearity in the switching kinetics which is induced by a temperature increase. In this respect, thermal crosstalk can be observed in highly integrated crossbar arrays which may impact the resistance state of adjacent devices. Additionally, due to the thermal capacitance, a VCM cell can remain thermally active after a pulse and thus influence the temperature conditions for a possible subsequent pulse. By using a finite element model of a crossbar array, it is shown that spatio-temporal thermal correlations can occur and are capable of affecting the resistive state of adjacent cells. This new functional behavior can potentially be used for future neuromorphic computing applications.     

A game-based algorithm for fair bandwidth allocation in Fibre-Wireless access networks

Fibre-Wireless (FiWi) access networks have been proposed as flexible and cost-effective solutions for future access networks. At the wireless mesh section, wireless routers have to forward both local traffic from directly connected users and foreign traffic from neighbour wireless routers. How to allocate resources to local and foreign traffic at each router in a balanced way, while avoiding starvation of routers requiring less resources, is a fundamental issue that must be solved so that new services emerge. Here, we develop a repeated game framework for bandwidth allocation and propose an algorithm that allocates bandwidth in a fair manner. The algorithm is able to detect over claiming routers and avoid possible denial of service that these may cause to others. Moreover, unfruitful use of resource is prevented, avoiding the forwarding of packets that would be dropped at some point later in the path, and queueing delay conditions are kept similar among local and foreign traffic. These fair network conditions open way for QoS support since it is easier to ensure the operationality of services.     

Specific features of the current–voltage characteristics of SiO2/4H-SiC MIS structures with phosphorus implanted into silicon carbide

The effect of phosphorus implantation into a 4H-SiC epitaxial layer immediately before the thermal growth of a gate insulator in an atmosphere of dry oxygen on the reliability of the gate insulator is studied. It is found that, together with passivating surface states, the introduction of phosphorus ions leads to insignificant weakening of the dielectric breakdown field and to a decrease in the height of the energy barrier between silicon carbide and the insulator, which is due to the presence of phosphorus atoms at the 4H-SiC/SiO₂ interface and in the bulk of silicon dioxide.     

Universal Polarization Switching Behavior of Disordered Ferroelectrics

Universal scaling features of polarization switching are established experimentally in rather different classes of disordered ferroelectrics: in well‐studied lead‐zirconate titanate (PZT) ferroelectrics, in recently synthesized Cu‐stabilized 0.94(Bi_1/2Na_1/2)TiO₃–0.06BaTiO₃ (BNT‐BT) relaxor ferroelectrics, and in classical organic ferroelectrics P(VDF‐TrFE). These scaling properties are explained by an extended concept of an inhomogeneous field mechanism (IFM) of polarization dynamics in ferroelectrics. Accordingly, disordered ferroelectrics exhibit a wide spectrum of characteristic switching times due to a statistical distribution of values of the local electric field. How this distribution can be extracted from polarization measurements is demonstrated. Generally, it is shown that the polarization response is primarily controlled by the statistical characteristics of disorder rather than by a temporal law of the local polarization switching.