Snow wetness measurements for melt forecasting

A microwave technique for directly measuring snow pack wetness in remote installations is described. The technique, which uses satellite telemetry for data gathering, is based on the attenuation of a microwave beam in transmission through snow

Particle-scale structure in frozen colloidal suspensions from small angle X-ray scattering

During directional solidification of the solvent in a colloidal suspension, the colloidal particles segregate from the growing solid, forming high-particle-density regions with structure on a hierarchy of length scales ranging from that of the particle-scale packing to the large-scale spacing between these regions. Previous work has mostly concentrated on the medium- to large-length scale structure, as it is the most accessible and thought to be more technologically relevant. However, the packing of the colloids at the particle-scale is an important component not only in theoretical descriptions of the segregation process, but also to the utility of freeze-cast materials for new applications. Here we present the results of experiments in which we investigated this structure across a wide range of length scales using a combination of small angle X-ray scattering and direct optical imaging. As expected, during freezing the particles were concentrated into regions between ice dendrites forming a microscopic pattern of high- and low-particle-density regions. X-ray scattering indicates that the particles in the high density regions were so closely packed as to be touching. However, the arrangement of the particles does not conform to that predicted by any standard inter-particle pair potentials, suggesting that the particle packing induced by freezing differs from that formed during equilibrium or steady-state densification processes

Dynamics of colloidal particles in ice

We use X-ray Photon Correlation Spectroscopy (XPCS) to probe the dynamics of colloidal particles in polycrystalline ice. During freezing, the dendritic ice morphology and rejection of particles from the ice created regions of high-particle-density, where some of the colloids were forced into contact and formed disordered aggregates. We find that the particles in these high density regions underwent ballistic motion coupled with both stretched and compressed exponential decays of the intensity autocorrelation function, and that the particles’ characteristic velocity increased with temperature. We explain this behavior in terms of ice grain boundary migration

Advanced prevention against icing on high voltage power lines

Historical meteorological data indicates, that our weather is becoming more and more extreme. For the electrical utility operators (Distribution System Operators - DSOs and Transmission System Operators - TSOs), these changes arise in new operation challenges that need to be addressed. For example, frequent icing phenomenon affects all the components of the power line by a significant mechanical overload: it endangers the conductors, the insulators and the towers, as well. The result is often fatal and beside serious failures, it effects on operators’ decisions. These not only endanger the reliability of electrical grids by the loss of a power line for weeks or even months, but in general, the safety in the surroundings of the power line. As technology advances, we will be able to collected, analyses and predict very large databases in the field of meteorology and electrical engineering. The ability of processing mentioned data, combined with know-how results in the capacity to operate power lines at their thermal limits during different ambient parameters. This technology called Dynamic Line Rating (DLR) – is not only a great way to increase the transmission capacity of a given line, but can also be effectively used to prevent, or even solve icing-related issues. Higher currents result in higher Joule-heats, that consequently heat the conductors. If limits can be reached or approached, icing can be prevented. If prevention is not possible, detection and removal of ice layer is necessary. The proper handling of this icing issues, requires advanced algorithms (expert systems) and reliable measuring equipment. The combination and synchronization between algorithms, weather service and measuring equipment is the key of the successful operation. An EU H2020 financed project called FLEXITRANSTORE has just been launched to develop a cross-country co-operation, with objective to improve anti-icing and de-icing solutions. To establish and analyse different solutions, the project includes several universities, TSOs and DSOs. To solve mentioned icing issues Budapest University of Technology and Economics’ (BME) developed an advanced neural-network based algorithm which use OTLM system. It is planned to install and demonstrate the capabilities of this new technology on the DSOs grid (Electro Ljubljana - ELJ). Besides the introduction of DLR and icing, this paper also focuses on the preparation/organisation of co-operation between different companies and universities

Performance of shallow anchor in ice-rich silt

Thesis (M.S.) University of Alaska Fairbanks, 2014Shallow anchor systems have been widely used for decades due to their time and cost efficiency. Yet when it comes to cold regions like Alaska, new challenges caused by the harsh environment need to be resolved before they are used extensively in cold regions. One challenge associated with anchor installation could be the potential thawing of warm permafrost due to the grout mortar hydration, which might undermine the capacity of the anchor. Another challenge is that due to low temperature the grout may cure slower or not cure at all, which will also result in a significant decrease in the ultimate strength of the anchor. Field tests were conducted to evaluate the performance of shallow anchors including duckbill anchors and grouted anchors with three types of different grouting materials, including Microsil Anchor Grout, Bentonite Clay and a newly-developed Antifreeze Grout Mortar. Constant-load creep test and pullout test were conducted to evaluate the performance of the anchors. Test results indicated that the anchors grouted with Antifreeze Grout Mortar caused the least permafrost disturbance and degradation, gained the largest tensile strength, exhibited the least creep displacement, and showed relatively large pullout capacity, and thus achieved the best performance among all types of shallow anchors

ОЦЕНКА ЧАСТОТЫ ОДНОПОЛУВОЛНОВОЙ ПЛЯСКИ ПРОВОДОВ РАСЩЕПЛЕННОЙ ФАЗЫ ЛЭП (АНКЕРНЫЙ ПРОЛЕТ)

In the presence of wind and the deposition of ice on the overhead power lines, mechanical oscillations of the wires are observed, characterized by a relatively low frequency and considerable amplitude ("dance" of wires). As a result of the “dance”, melting and burning of wires occurs due to short circuits, damage and breakage of supports, garlands of insulators and other elements of transmission lines. The article reviews a brief overview of the current state of the issue and formulates the purpose and objectives of the study. The main goal of the scientific article is the development of an engineering method for calculating the frequency characteristics of a split-phase dance with reference to an anchor span. The basis of the developed method is the analysis of the energy balance of the oscillatory process and the mathematical model of the dance of wires. The problem is limited to vertical one-half-wave oscillations of the split phase. The developed calculation formula establishes the relationship between the frequency of dancing, wind speed, aerodynamic characteristics of the icy wire and the parameters of the overhead line. The formula for determining the dance frequency can be used to solve various applied problems