As the interface between frozen and unfrozen soil, the ice front is not only a spatial location concept, but also a potentially dangerous interface where the mechanical properties of soil could change abruptly. Accurately identifying its spatial position is essential for the safe and efficient execution of large-scale frozen soil engineering projects. Electrical capacitance tomography (ECT) is a promising method for the visualization of frozen soil due to its non-invasive nature, low cast, and rapid response. This paper presents the design and optimization of a mobile circular capacitance sensor (MCCS). The MCCS was used to measure frozen soil samples along the depth direction to obtain moisture distribution and three-dimensional images of the ice front. Finally, the experimental results were compared with the simulation results from COMSOL Multiphysics to analyze the deviations. It was found that the fuzzy optimization design based on multi-criteria orthogonal experiments makes the MCCS meet various performance requirements. The average permittivity distribution was proposed to reflect moisture distribution along the depth direction and showed good correlation. Three-dimensional reconstructed images could provide the precise position of the ice front. The simulation results indicate that the MCCS has a low deviation margin in identifying the position of the ice front.

Nanometer scale planar Schottky barrier diodes (SBDs) with realistic geometries have been studied by means of a 2-D ensemble Monte Carlo simulator. The topology of the devices studied in this paper is based in real planar GaAs SBDs used in terahertz applications, such as passive frequency mixing and multiplication, in which accurate models for the diode capacitance are required. The intrinsic capacitance of such small devices, which due to edge effects strongly deviates from the ideal value, has been calculated. In good agreement with the classical models, we have found that the edge capacitance is independent of the properties of the semiconductor beneath the contact and, as novel result, that the presence of surface charges at the semiconductor dielectric interface can reduce it almost 15%. We have finally provided a compact model for the total capacitance of diodes with arbitrary shape that could be easily implemented in design automation software such as Advance Design System (ADS).

Published literature suggests that water ice might be unambiguously detected in the presence of background contaminants by developing a frequency swept sensor to obtain the dielectric spectrum. Such a sensor could be incorporated into the tip of a spike and driven into the lunar regolith to detect moisture as a function of depth. A sensor was created to test this concept for varying concentrations of ice in lunar soil simulant under vacuum conditions. Ice relaxation occurs at frequencies well below 1 Hz at temperatures present on the Lunar surface, making it difficult to distinguish ice from the surrounding regolith. So, a heating element was incorporated with the sensor to capture the dielectric spectra as the ice warms, allowing the relaxation to be detected in a shorter period of time. The test results show the ability of this sensor to detect the presence of varying quantities of ice in the soil simulant and the need for more complex non-linear mixing models to quantify the amount of ice present in the mixture. Published by Elsevier Ltd.