Observability analysis of electric networks considering branch impedance

This paper presents an analytical method to analyze the effect of X to R ratio as well as impedance value of branches on observability of a network based on un-decoupled formulation of state estimation (SE) and null space of matrices. The results showed that the X to R ratio of branches had no effect on the observability of networks. In addition, it was shown that observability of some networks was affected by impedance values while some others were not affected. In addition, for branch observability analysis of radial network, a simple and quick method is developed. Illustrative examples of the network under transmission and distribution voltages demonstrate the effectiveness of the proposed methods.

An efficient hybrid evolutionary optimization algorithm for daily volt/var control at distribution system including DGs

This paper presents a new hybrid evolutionary algorithm based on Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO) for daily Volt/Var control in distribution system including Distributed Generators (DGs). Due to the small X/R ratio and radial configuration of distribution systems, DGs have much impact on this problem. Since DGs are independent power producers or private ownership, a price based methodology is proposed as a proper signal to encourage owners of DGs in active power generation. Generally, the daily Volt/Var control is a nonlinear optimization problem. Therefore, an efficient hybrid evolutionary method based on Particle Swarm Optimization and Ant Colony Optimization (ACO), called HPSO, is proposed to determine the active power values of DGs, reactive power values of capacitors and tap positions of transformers for the next day. The feasibility of the proposed algorithm is demonstrated and compared with methods based on the original PSO, ACO and GA algorithms on IEEE 34-bus distribution feeder.

Distribution harmonic state estimation based on a modified PSO considering parameters uncertainty

This paper presents a new algorithm based on a Modified Particle Swarm Optimization (MPSO) to estimate the harmonic state variables in a distribution networks. The proposed algorithm performs the estimation for both amplitude and phase of each injection harmonic currents by minimizing the error between the measured values from Phasor Measurement Units (PMUs) and the values computed from the estimated parameters during the estimation process. The proposed algorithm can take into account the uncertainty of the harmonic pseudo measurement and the tolerance in the line impedances of the network as well as the uncertainty of the Distributed Generators (DGs) such as Wind Turbines (WTs). The main features of the proposed MPSO algorithm are usage of a primary and secondary PSO loop and applying the mutation function. The simulation results on 34-bus IEEE radial and a 70-bus realistic radial test networks are presented. The results demonstrate that the speed and the accuracy of the proposed Distribution Harmonic State Estimation (DHSE) algorithm are very excellent compared to the algorithms such as Weight Least Square (WLS), Genetic Algorithm (GA), original PSO, and Honey Bees Mating Optimization (HBMO).

Distribution harmonic state estimation based on a hybrid PSO and SA algorithm considering parameters uncertainty

This paper presents a new algorithm based on a Hybrid Particle Swarm Optimization (PSO) and Simulated Annealing (SA) called PSO-SA to estimate harmonic state variables in distribution networks. The proposed algorithm performs estimation for both amplitude and phase of each harmonic currents injection by minimizing the error between the measured values from Phasor Measurement Units (PMUs) and the values computed from the estimated parameters during the estimation process. The proposed algorithm can take into account the uncertainty of the harmonic pseudo measurement and the tolerance in the line impedances of the network as well as uncertainty of the Distributed Generators (DGs) such as Wind Turbines (WT). The main feature of proposed PSO-SA algorithm is to reach quickly around the global optimum by PSO with enabling a mutation function and then to find that optimum by SA searching algorithm. Simulation results on IEEE 34 bus radial and a realistic 70-bus radial test networks are presented to demonstrate the speed and accuracy of proposed Distribution Harmonic State Estimation (DHSE) algorithm is extremely effective and efficient in comparison with the conventional algorithms such as Weight Least Square (WLS), Genetic Algorithm (GA), original PSO and Honey Bees Mating Optimization (HBMO) algorithm.

Distribution state estimation based on particle swarm and doubly loop mutant optimization (DLM-PSO)

This paper presents a novel algorithm based on particle swarm optimization (PSO) to estimate the states of electric distribution networks. In order to improve the performance, accuracy, convergence speed, and eliminate the stagnation effect of original PSO, a secondary PSO loop and mutation algorithm as well as stretching function is proposed. For accounting uncertainties of loads in distribution networks, pseudo-measurements is modeled as loads with the realistic errors. Simulation results on 6-bus radial and 34-bus IEEE test distribution networks show that the distribution state estimation based on proposed DLM-PSO presents lower estimation error and standard deviation in comparison with algorithms such as WLS, GA, HBMO, and original PSO.

Numerical modelling of porous injection in a radical farming scramjet

A numerical investigation of the behaviour of fuel injection through a porous surface in an inlet-fuelled, radial-farming scramjet is presented. The performance of porous fuel injection is compared to discrete port hole injection at an equivalence ratio of φ ≈ 0.4 for both cases. The comparison is performed at a Mach 6.5 flow condition with a total specific enthalpy of 4.3 MJ/kg. The numerical results are compared to experiments performed in the T4 shock tunnel where available. The presented results demonstrate for the first time, that porous fuel injection has the potential to outperform port hole injectors in scramjet engines in terms of fuel-air mixing, ignition delays and achievable combustion efficiencies despite reduced fuel penetration heights.

Surface dosimetry for very small X-ray beams

Introduction The dose to skin surface is an important factor for many radiotherapy treatment techniques. It is known that TPS predicted surface doses can be significantly different from actual ICRP skin doses as defined at 70 lm. A number of methods have been implemented for the accurate determination of surface dose including use of specific dosimeters such as TLDs and radiochromic film as well as Monte Carlo calculations. Stereotactic radiosurgery involves delivering very high doses per treatment fraction using small X-ray fields. To date, there has been limited data on surface doses for these very small field sizes. The purpose of this work is to evaluate surface doses by both measurements and Monte Carlo calculations for very small field sizes. Methods All measurements were performed on a Novalis Tx linear accelerator which has a 6 MV SRS X-ray beam mode which uses a specially thin flattening filter. Beam collimation was achieved by circular cones with apertures that gave field sizes ranging from 4 to 30 mm at the isocentre. The relative surface doses were measured using Gafchromic EBT3 film which has the active layer at a depth similar to the ICRP skin dose depth. Monte Carlo calculations were performed using the BEAMnrc/EGSnrc Monte Carlo codes (V4 r225). The specifications of the linear accelerator, including the collimator, were provided by the manufacturer. Optimisation of the incident X-ray beam was achieved by an iterative adjustment of the energy, spatial distribution and radial spread of the incident electron beam striking the target. The energy cutoff parameters were PCUT = 0.01 MeV and ECUT = 0.700 - MeV. Directional bremsstrahlung splitting was switched on for all BEAMnrc calculations. Relative surface doses were determined in a layer defined in a water phantom of the same thickness and depth as compared to the active later in the film. Results Measured surface doses using the EBT3 film varied between 13 and 16 % for the different cones with an uncertainty of 3 %. Monte Carlo calculated surface doses were in agreement to better than 2 % to the measured doses for all the treatment cones. Discussion and conclusions This work has shown the consistency of surface dose measurements using EBT3 film with Monte Carlo predicted values within the uncertainty of the measurements. As such, EBT3 film is recommended for in vivo surface dose measurements.

Quantitative sensory measures distinguish office workers with varying levels of neck pain and disability

This study was undertaken to investigate any relationship between sensory features and neck pain in female office workers using quantitative sensory measures to better understand neck pain in this group. Office workers who used a visual display monitor for more than four hours per day with varying levels of neck pain and disability were eligible for inclusion. There were 85 participants categorized according to their scores on the neck disability index (NDI): 33 with no pain (NDI < 8); 38 with mild levels of pain and disability (NDI 9–29); 14 with moderate levels of pain (NDI ⩾ 30). A fourth group of women without neck pain (n = 22) who did not work formed the control group. Measures included: thermal pain thresholds over the posterior cervical spine; pressure pain thresholds over the posterior neck, trapezius, levator scapulae and tibialis anterior muscles, and the median nerve trunk; sensitivity to vibrotactile stimulus over areas of the hand innervated by the median, ulnar and radial nerves; sympathetic vasoconstrictor response. All tests were conducted bilaterally. ANCOVA models were used to determine group differences between the means for each sensory measure. Office workers with greater self-reported neck pain demonstrated hyperalgesia to thermal stimuli over the neck, hyperalgesia to pressure stimulation over several sites tested; hypoaesthesia to vibration stimulation but no changes in the sympathetic vasoconstrictor response. There is evidence of multiple peripheral nerve dysfunction with widespread sensitivity most likely due to altered central nociceptive processing initiated and sustained by nociceptive input from the periphery.

Generalized azimuthal shear deformations in compressible isotropic elastic materials

In this article we study the azimuthal shear deformations in a compressible Isotropic elastic material. This class of deformations involves an azimuthal displacement as a function of the radial and axial coordinates. The equilibrium equations are formulated in terms of the Cauchy-Green strain tensors, which form an overdetermined system of partial differential equations for which solutions do not exist in general. By means of a Legendre transformation, necessary and sufficient conditions for the material to support this deformation are obtained explicitly, in the sense that every solution to the azimuthal equilibrium equation will satisfy the remaining two equations. Additionally, we show how these conditions are sufficient to support all currently known deformations that locally reduce to simple shear. These conditions are then expressed both in terms of the invariants of the Cauchy-Green strain and stretch tensors. Several classes of strain energy functions for which this deformation can be supported are studied. For certain boundary conditions, exact solutions to the equilibrium equations are obtained. © 2005 Society for Industrial and Applied Mathematics.

Influence of jet inclination on structural loading in an experimentally simulated microburst

Steady and pulsed flow stationary impinging jets have been employed to simulate the wind field produced by a thunderstorm microburst. The effect on the low level wind field due to jet inclination with respect to the impingement surface has been studied. A single point velocity time history has been compared to the full-scale Andrews AFB microburst for model validation. It was found that for steady flow, jet inclination increased the radial extent of high winds but did not increase the magnitude of these winds when compared to the perpendicular impingement case. It was found that for inclined pulsed flow the design wind conditions could increase compared to perpendicular impingement. It was found that the location of peak winds was affected by varying the outlet conditions.

Generation of uniform plasmas by crossed internal oscillating current sheets : key concepts and experimental verification

The results of comprehensive experimental studies of the operation, stability, and plasma parameters of the low-frequency (0.46 MHz) inductively coupled plasmas sustained by the internal oscillating rf current are reported. The rf plasma is generated by using a custom-designed configuration of the internal rf coil that comprises two perpendicular sets of eight currents in each direction. Various diagnostic tools, such as magnetic probes, optical emission spectroscopy, and an rf-compensated Langmuir probe were used to investigate the electromagnetic, optical, and global properties of the argon plasma in wide ranges of the applied rf power and gas feedstock pressure. It is found that the uniformity of the electromagnetic field inside the plasma reactor is improved as compared to the conventional sources of inductively coupled plasmas with the external flat coil configuration. A reasonable agreement between the experimental data and computed electromagnetic field topography inside the chamber is reported. The Langmuir probe measurements reveal that the spatial profiles of the electron density, the effective electron temperature, plasma potential, and electron energy distribution/probability functions feature a high degree of the radial and axial uniformity and a weak azimuthal dependence, which is consistent with the earlier theoretical predictions. As the input rf power increases, the azimuthal dependence of the global plasma parameters vanishes. The obtained results demonstrate that by introducing the internal oscillated rf currents one can noticeably improve the uniformity of electromagnetic field topography, rf power deposition, and the plasma density in the reactor.

Inductively coupled plasmas sustained by an internal oscillating current

A global electromagnetic model of an inductively coupled plasma sustained by an internal oscillating current sheet in a cylindrical metal vessel is developed. The electromagnetic field structure, profiles of the rf power transferred to the plasma electrons, electron/ion number density, and working points of the discharge are studied, by invoking particle and power balance. It is revealed that the internal rf current with spatially invariable phase significantly improves the radial uniformity of the electromagnetic fields and the power density in the chamber as compared with conventional plasma sources with external flat spiral inductive coils. This configuration offers the possibility of controlling the rf power deposition in the azimuthal direction.

Parameters and equilibrium profiles for large-area surface-wave sustained plasmas

The equilibrium profiles of the plasma parameters of large-area if discharges in a finite-length metal-shielded dielectric cylinder are computed using a two-dimensional fluid code. The rf power is coupled to the plasma through edge-localized surface waves traveling in the azimuthal direction along the plasma edge. It is shown that self-consistent accounting for axial plasma diffusion and radial nonuniformity of the electron temperature can explain the frequently reported deviations of experimentally measured radial density profiles from that of the conventional linear diffusion models. The simulation results are in a good agreement with existing experimental data obtained from surface-wave sustained large-diameter plasmas. © 2002 The American Physical Society.

Effect of pupil dilation and constriction on the distribution of bit errors within the iris

Texture information in the iris image is not uniform in discriminatory information content for biometric identity verification. The bits in an iris code obtained from the image differ in their consistency from one sample to another for the same identity. In this work, errors in bit strings are systematically analysed in order to investigate the effect of light-induced and drug-induced pupil dilation and constriction on the consistency of iris texture information. The statistics of bit errors are computed for client and impostor distributions as functions of radius and angle. Under normal conditions, a V-shaped radial trend of decreasing bit errors towards the central region of the iris is obtained for client matching, and it is observed that the distribution of errors as a function of angle is uniform. When iris images are affected by pupil dilation or constriction the radial distribution of bit errors is altered. A decreasing trend from the pupil outwards is observed for constriction, whereas a more uniform trend is observed for dilation. The main increase in bit errors occurs closer to the pupil in both cases.

Internal oscillating current-sustained RF plasmas : Parameters, stability, and potential for surface engineering

A new source of low-frequency (0.46 MHz) inductively coupled plasmas sustained by the internal planar "unidirectional" RF current driven through a specially designed internal antenna configuration has been developed. The experimental results of the investigation of the optical and global argon plasma parameters by the optical and Langmuir probes are presented. It is shown that the spatial profiles of the electron density, the effective electron temperature and plasma potential feature a great deal of the radial and axial uniformity compared with conventional sources of inductively coupled plasmas with external at coil configurations. The measurements also reveal a weak azimuthal dependence of the global plasma parameters at low values of the input RF power, which was earlier predicted theoretically. The azimuthal dependence of the global plasma parameters vanishes at high input RF powers. Moreover, under certain conditions, the plasma becomes unstable due to spontaneous transitions between low-density (electrostatic, E) and high-density (electromagnetic, H) operating modes. Excellent uniformity of high-density plasmas makes the plasma reactor promising for various plasma processing applications and surface engineering.