Analysis of harmonics in subsea power transmission cables used in VSC-HVDC transmission systems operating under steady-state conditions

Subsea power cables are a critical component of a voltage-source converter-high-voltage direct current (VSC-HVDC) transmission system in any offshore electrical power scheme. Subsea cables have complicated structures consisting of many different layers: conductor, insulation, sheath, and armor. Harmonic performance of the system depends upon the interactions between the subsea cable, the power converters, and other system components, such as smoothing capacitors. In this paper, a mathematical model of an HVDC-VSC transmission system is developed and its harmonic performance is investigated for steady-state operating conditions. The results suggest that the design of the subsea transmission cable has important effects on harmonic levels in the voltage and current waveforms in the cable and upon power loss within the transmission system. This paper demonstrates that it is always important to consider interactions between all of the system components when predicting harmonic performance in a VSC-HVDC transmission system

Intermediate (S=1) spin state in five-coordinate cobalt(III): Magnetic properties of N-o-hydroxy-benzamido-meso-tetraphenylporphyrin cobalt(III), Co(N-NCO(o-O)C6H4-tpp)

The crystal structures of paramagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4),N-1,N-2,N-3,N-5,kappa O-2) cobalt(III) [Co(N-NCO(o-O)C6H4-tpp); 2] (S = 1) and diamagnetic N-o-oxido-benzimido-meso-tetraphenylporphyrinato (-kappa(4), N-1, N-2, N-3, N-5, kappa O-2) gallium( III) chloroform center dot methanol solvate [Ga(N-NCO(o-O)C6H4-tpp)center dot 0.5CHCl(3)center dot MeOH; 3 center dot 0.5CHCl(3) center dot MeOH] (S = 0) were determined. The coordination sphere around Co(III) in 2 [or Ga(III) in 3 center dot 0.5CHCl(3)center dot MeOH] is described as five-coordinate distorted trigonal bipyramid (DTBP) with O(1), N(1)and N(3) [or O(2), N(1), N(3)] lying in the equatorial plane for 2 [or 3 center dot 0.5CHCl(3)center dot MeOH]. The magnitude of axial (D) zero-field splitting (ZFS) for the Co(III) (S = 1) in 2 was determined as approximately 107 cm(-1) by paramagnetic susceptibility measurements. The compound (2) reacts in donor solvent such as pyridine to form six-coordinate diamagnetic species of the type Co(N-NCO(o-O) C6H4-tpp)(py) (4), whose H-1 NMR spectra can be interpreted as for Co(III) in an octahedral environment

Distinguishing d-wave from highly anisotropic s-wave superconductors

Systematic impurity doping in the Cu-O plane of the hole-doped cuprate superconductors may allow one to decide between unconvention al ("d-wave") and anisotropic conventional ("s-wave") states as possible candidates for the order parameter in these materials. We show that potential scattering of any strength always increases the gap minima of such s-wave states, leading to activated behavior in temperature with characteristic impurity concentration dependence in observable quantities such as the penetration depth. A magnetic component to the scattering may destroy the energy gap and give rise to conventional gapless behavior, or lead to a nonmonotonic dependence of the gap on impurity concentration. We discuss how experiments constrain this analysis.Comment: 5 page

Efficient Recognition of Partially Visible Objects Using a Logarithmic Complexity Matching Technique

An important task in computer vision is the recognition of partially visible two-dimensional objects in a gray scale image. Recent works addressing this problem have attempted to match spatially local features from the image to features generated by models of the objects. However, many algo rithms are considerably less efficient than they might be, typ ically being O(IN) or worse, where I is the number offeatures in the image and N is the number of features in the model set. This is invariably due to the feature-matching portion of the algorithm. In this paper we discuss an algorithm that significantly improves the efficiency offeature matching. In addition, we show experimentally that our recognition algo rithm is accurate and robust. Our algorithm uses the local shape of contour segments near critical points, represented in slope angle-arclength space (θ-s space), as fundamental fea ture vectors. These feature vectors are further processed by projecting them onto a subspace in θ-s space that is obtained by applying the Karhunen-Loève expansion to all such fea tures in the set of models, yielding the final feature vectors. This allows the data needed to store the features to be re duced, while retaining nearly all information important for recognition. The heart of the algorithm is a technique for performing matching between the observed image features and the precomputed model features, which reduces the runtime complexity from O(IN) to O(I log I + I log N), where I and N are as above. The matching is performed using a tree data structure, called a kD tree, which enables multidi mensional searches to be performed in O(log) time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66975/2/10.1177_027836498900800608.pd

Spin-Charge Separation in the t−Jt-J Model: Magnetic and Transport Anomalies

A real spin-charge separation scheme is found based on a saddle-point state of the $t-J$ model. In the one-dimensional (1D) case, such a saddle-point reproduces the correct asymptotic correlations at the strong-coupling fixed-point of the model. In the two-dimensional (2D) case, the transverse gauge field confining spinon and holon is shown to be gapped at {\em finite doping} so that a spin-charge deconfinement is obtained for its first time in 2D. The gap in the gauge fluctuation disappears at half-filling limit, where a long-range antiferromagnetic order is recovered at zero temperature and spinons become confined. The most interesting features of spin dynamics and transport are exhibited at finite doping where exotic {\em residual} couplings between spin and charge degrees of freedom lead to systematic anomalies with regard to a Fermi-liquid system. In spin dynamics, a commensurate antiferromagnetic fluctuation with a small, doping-dependent energy scale is found, which is characterized in momentum space by a Gaussian peak at ($\pi/a$, $\pi/a$) with a doping-dependent width ($\propto \sqrt{\delta}$, $\delta$ is the doping concentration). This commensurate magnetic fluctuation contributes a non-Korringa behavior for the NMR spin-lattice relaxation rate. There also exits a characteristic temperature scale below which a pseudogap behavior appears in the spin dynamics. Furthermore, an incommensurate magnetic fluctuation is also obtained at a {\em finite} energy regime. In transport, a strong short-range phase interference leads to an effective holon Lagrangian which can give rise to a series of interesting phenomena including linear-$T$ resistivity and $T^2$ Hall-angle. We discuss the striking similarities of these theoretical features with those found in the high-$T_c$ cuprates and give aComment: 70 pages, RevTex, hard copies of 7 figures available upon request; minor revisions in the text and references have been made; To be published in July 1 issue of Phys. Rev. B52, (1995