Dielectric losses in ammonium fluorosilicates

Cubic and trigonal (NH₄)₂SiF₆ have low-temperature dielectric-loss maxima with activation energies E_a (cubic) = 5.4 kcal/mol and E_a(trig.) = 8.7 kcal/mol, not related to ionic reorientation and probably caused by OH^? impurities.     

Allocation of long-term financial transmission rights for transmission expansion

Long-term financial transmission rights (FTRs) could be used to create incentives for small-scale transmission investments. However, these new investments may cause negative externalities on existing FTRs. Therefore the system operator needs a protocol for awarding incremental FTRs for new transmission capacity that maximize investors’ preferences while simultaneously accounting for under-allocation of the existing network capacity by existing FTRs. To preserve revenue adequacy, the system operator calculates a minimum amount of currently unallocated FTRs (or proxy FTRs) that satisfies the power flow constraints in the existing network. The challenge is to define the proxy awards. Hogan proposes to define them as the best use of the current network along the same direction as the incremental FTR awards. This includes allowing positive or negative incremental FTR awards. In this paper we present an implementation through bi-level programming of Hogan’s proposal for allocation of long-term FTRs and apply it to a radial line and one of Hogan’s examples. Our results show that the simultaneous feasibility of the transmission investment depends on factors such as investor and preset proxy preferences, existing FTRs, and transmission capacity in both the existing network and all proposed expansions of it.     

Using a multi-layered transducer model to estimate the properties of paraffin wax deposited on steel

When using ultrasound for detecting low impedance materials on the surface of high impedance materials, a major challenge is the contrast difference between the strong reverberations from the high impedance material and the weak echoes received from the low impedance material. The purpose of this work is to present the theoretical and experimental validation of an ultrasonic methodology for estimating the acoustical properties of paraffin wax on the surface of steel. The method is based on modeling and inversion of the complete electro-acoustic channel from the transmitted voltage over the active piezoelectric element, to the received voltage resulting from the acoustic reverberations in the multilayered structure. In the current work, two conceptually different models of the same multi-layer transducer structure attached to steel is developed and compared with measurements. A method is then suggested for suppressing the strong reverberations in steel, hence isolating the wax signals. This contrast enhancement method is fitted to the model of the structure, facilitating parameter inversion from the wax layer. The results show that the models agree well with measurements and that up to three parameters (travel time, impedance and attenuation) can be inverted from the wax simultaneously. Hence, given one of the three parameters, density, sound speed or thickness, the other two can be estimated in addition to the attenuation.