The location of a resistive shunt harmonic impedance along a distribution feeder and its influence on harmonic propagation

Although complete compensation is only possible using true active filters, resistive shunt harmonic impedances (SHI) have been shown to provide a considerable reduction of the harmonic propagation. In this paper, the harmonic mitigation potential of a resistive SHI is discussed concerning its influence on the voltage distortion profile along a typical distribution feeder, with the location of the SHI along the feeder as a parameter. Although the distortion values are dependent on the SHI location, it is shown that the end of the feeder is generally a good location to install the SHI, especially when the power system parameters can vary or are unknown. Calculations are performed on a typical radial distribution feeder. Both the power factor correction capacitors and the non-linear loads are concentrated in single nodes. The linear loads are disconnected to obtain the worst case for the voltage distortion. Also some measurements on a scale model of a typical distribution feeder are done and the experimental results confirm the results obtained from simulations.     

Spectral data for doubly excited states of helium with non-zero total angular momentum

A spectral approach is used to evaluate energies and widths for a wide range of singlet and triplet resonance states of helium. Data for total angular momentum L=1,…,4 is presented for resonances up to below the fifth single ionization threshold. In addition, the expectation value of cos(θ₁₂) is given for the calculated resonances.     

Sharpened Aharanov-Bohm oscillations near resonance in a balanced ring with double quantum dots

In a balanced Aharonov-Bohm ring with an identical quantum dot (QD) in each arm, the transmission amplitude near resonance consists of a zero and pole which can be made to nearly or exactly overlap in the complex-energy plane. This presents a sensitively balanced region of parameter space in which arbitrarily sharp transmission resonance spikes manifest. Analytical results based on a tight-binding solution of the Schrödinger Equation for this system demonstrate the extreme flux sensitivity of the balanced ring in the vicinity of the resonance near the quasi-bound state energy of the QD’s. This effect may have practical applications as a sensitive monitor of magnetic flux.     

Analysis of resonances during microwave thawing of slabs

Resonances or maxima in power absorption due to microwaves incidence within a slab are analyzed via transmitted and reflected waves. A generalized mathematical formulation for uniform plane waves has been established to analyze traveling waves, stationary waves and microwave power absorption within a multiphase sample. Preliminary studies based on the generalized mathematical analysis in ice and water slabs illustrate that greater amplitudes of traveling and stationary waves occur within ice samples, whereas, greater intensity of spatial resonances in microwave power occurs for water samples due to a greater dielectric loss of water. Microwave thawing is studied for specific sample thicknesses which are selected based on greater power distribution within water samples. The enthalpy method is employed for modeling of thawing of ice samples where a superficial mushy region is assumed around the melting point. Depending on the sample thickness, thawing may occur from the unexposed face as well as both the faces when the sample is exposed to microwaves at one face only, whereas thawing may originate from both the center as well as the faces when the sample is exposed to microwaves at both faces. Our analysis based on the generalized mathematical formulation validates the local maxima in spatial power distribution during intermediate thawing stages obtained with the finite element based enthalpy formulation. The generalized mathematical analysis on multiple thawed regimes further illustrates the role of traveling waves on resonances in microwave power. The influence of resonance is attributed by a non-monotonic variation of thawing time with sample thicknesses either for one side incidence or both side incidence due to microwaves. Optimal thawing strategies are recommended based on greater power savings.     

Transport in open quantum systems: comparing classical and quantum phase space dynamics

Transport in open quantum systems is of great interest. We show that the discrete states of an open quantum system may be classified into three distinct groups, dependent upon the manner in which they influence transport when connected to an external environment. A first class of states is current-carrying states, which are naturally strongly connected to the environment. A second class of states is discrete, but stable and isolated, and thought to be the pointer states of decoherence theory. Finally, we identify backscattered states, which do not propagate through the system.     

Low-energy electron elastic collision cross sections for ground and excited Tm, Lu and Hf atoms

Low-energy 0 ? E ? 1.0 eV electron elastic scattering from ground and excited Tm, Lu and Hf atoms has been investigated. Both total and differential cross sections have been calculated; the latter at the scattering angles θ = 0°, 90° and 180°. The recent Regge-pole methodology has been used for the calculations. In the method the crucial electron-electron correlation effects are accounted for through the Mulholland formula. We find that the total cross sections are characterized generally by shape resonances, Ramsauer-Townsend minima and dramatically sharp long-lived resonances from which we extract the binding energies of the negative ions. Our extracted binding energy of the Hf⁻ negative ion from the total cross section is compared with that of Pan and Beck [14].     

Simulation of resonant tunneling heterostructures: numerical comparison of a complete Schrödinger-Poisson system and a reduced nonlinear model

Two different models are compared for the simulation of the transverse electronic transport through a heterostructure: a 1D self-consistent Schrödinger-Poisson model with a numerically heavy treatment of resonant states and a reduced model derived from an accurate asymptotic nonlinear analysis. After checking the agreement at the qualitative and quantitative level on quite well understood bifurcation diagrams, the reduced model is used to tune double well configurations for which nonlinearly interacting resonant states actually occur in the complete self-consistent model.