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© 1972-2012 IEEE. Techniques for parameter determination of induction and doubly fed induction machines are well established. However, these techniques do not apply directly to the brushless doubly fed reluctance machine (BDFRM). Even though the mathematical model for this machine is like that of a double-fed induction machine, the complexity of the machines magnetic fields due to differing winding pole numbers interacting with a reluctance rotor preclude standard testing. Very high leakage inductances affect the use of the normal locked rotor test, and nonsinusoidal air gap fluxes complicate modeling for stand still frequency domain and time domain testing. This paper examines the validity of a combination of testing and analysis techniques, including open circuit and pulse testing, which were eventually used to determine the BDFRM inductance parameters over a range of operating points. The accuracy of the results are validated by machine testing and comparison with the finite element analysis machine design.

We present a suite of seven 3D supernova simulations of non-rotating low-mass progenitors using multi-group neutrino transport. Our simulations cover single star progenitors with zero-age main sequence masses between $9.6 M_\odot$ and $12.5 M_\odot$ and (ultra)stripped-envelope progenitors with initial helium core masses between $2.8 M_\odot$ and $3.5 M_\odot$. We find explosion energies between $0.1\,\mathrm{Bethe}$ and $0.4\,\mathrm{Bethe}$, which are still rising by the end of the simulations. Although less energetic than typical events, our models are compatible with observations of less energetic explosions of low-mass progenitors. In six of our models, the mass outflow rate already exceeds the accretion rate onto the proto-neutron star, and the mass and angular momentum of the compact remnant have closely approached their final value, barring the possibility of later fallback. While the proto-neutron star is still accelerated by the gravitational tug of the asymmetric ejecta, the acceleration can be extrapolated to obtain estimates for the final kick velocity. We obtain gravitational neutron star masses between $1.22 M_\odot$ and $1.44 M_\odot$, kick velocities between $11\, \mathrm{km}\, \mathrm{s}^{-1}$ and $695\, \mathrm{km}\, \mathrm{s}^{-1}$, and spin periods from $20\, \mathrm{ms}$ to $2.7\,\mathrm{s}$, which suggests that typical neutron star birth properties can be naturally obtained in the neutrino-driven paradigm. We find a loose correlation between the explosion energy and the kick velocity. There is no indication of spin-kick alignment, but a correlation between the kick velocity and the neutron star angular momentum, which needs to be investigated further as a potential point of tension between models and observations., Comment: 18 pages, 14 figures. Submitted to MNRAS

The recent discoveries of many double neutron star systems and their detection as LIGO-Virgo merger events call for a detailed understanding of their origin. Explosions of ultra-stripped stars in binary systems have been shown to play a key role in this context and have also generated interest as a potential explanation for rapidly evolving hydrogen-free transients. Here we present the first attempt to model such explosions based on binary evolution calculations that follow the mass transfer to the companion to obtain a consistent core-envelope structure as needed for reliable predictions of the supernova transient. We simulate the explosion in 2D and 3D, and confirm the modest explosion energies ~10^50erg and small kick velocities reported earlier in 2D models based on bare carbon-oxygen cores. The spin-up of the neutron star by asymmetric accretion is small in 3D with no indication of spin-kick alignment. Simulations up to shock breakout show the mixing of sizeable amounts of iron group material into the helium envelope. In view of recent ideas for a mixing-length treatment (MLT) of Rayleigh-Taylor instabilities in supernovae, we perform a detailed analysis of the mixing, which reveals evidence for buoyancy-drag balance, but otherwise does not support the MLT approximation. The mixing may have implications for the spectroscopic signatures of ultra-stripped supernovae that need to be investigated in the future. Our stellar evolution calculation also predicts presupernova mass loss due to an off-centre silicon deflagration flash, which suggests that supernovae from extremely stripped cores may show signs of interactions with circumstellar material., Comment: 15 pages, 15 figures, submitted to MNRAS

We present a suite of seven 3D supernova simulations of non-rotating low-mass progenitors using multi-group neutrino transport. Our simulations cover single star progenitors with zero-age main sequence masses between $9.6 M_\odot$ and $12.5 M_\odot$ and (ultra)stripped-envelope progenitors with initial helium core masses between $2.8 M_\odot$ and $3.5 M_\odot$. We find explosion energies between $0.1\,\mathrm{Bethe}$ and $0.4\,\mathrm{Bethe}$, which are still rising by the end of the simulations. Although less energetic than typical events, our models are compatible with observations of less energetic explosions of low-mass progenitors. In six of our models, the mass outflow rate already exceeds the accretion rate onto the proto-neutron star, and the mass and angular momentum of the compact remnant have closely approached their final value, barring the possibility of later fallback. While the proto-neutron star is still accelerated by the gravitational tug of the asymmetric ejecta, the acceleration can be extrapolated to obtain estimates for the final kick velocity. We obtain gravitational neutron star masses between $1.22 M_\odot$ and $1.44 M_\odot$, kick velocities between $11\, \mathrm{km}\, \mathrm{s}^{-1}$ and $695\, \mathrm{km}\, \mathrm{s}^{-1}$, and spin periods from $20\, \mathrm{ms}$ to $2.7\,\mathrm{s}$, which suggests that typical neutron star birth properties can be naturally obtained in the neutrino-driven paradigm. We find a loose correlation between the explosion energy and the kick velocity. There is no indication of spin-kick alignment, but a correlation between the kick velocity and the neutron star angular momentum, which needs to be investigated further as a potential point of tension between models and observations., Comment: 18 pages, 14 figures. Submitted to MNRAS

The recent discoveries of many double neutron star systems and their detection as LIGO-Virgo merger events call for a detailed understanding of their origin. Explosions of ultra-stripped stars in binary systems have been shown to play a key role in this context and have also generated interest as a potential explanation for rapidly evolving hydrogen-free transients. Here we present the first attempt to model such explosions based on binary evolution calculations that follow the mass transfer to the companion to obtain a consistent core-envelope structure as needed for reliable predictions of the supernova transient. We simulate the explosion in 2D and 3D, and confirm the modest explosion energies ~10^50erg and small kick velocities reported earlier in 2D models based on bare carbon-oxygen cores. The spin-up of the neutron star by asymmetric accretion is small in 3D with no indication of spin-kick alignment. Simulations up to shock breakout show the mixing of sizeable amounts of iron group material into the helium envelope. In view of recent ideas for a mixing-length treatment (MLT) of Rayleigh-Taylor instabilities in supernovae, we perform a detailed analysis of the mixing, which reveals evidence for buoyancy-drag balance, but otherwise does not support the MLT approximation. The mixing may have implications for the spectroscopic signatures of ultra-stripped supernovae that need to be investigated in the future. Our stellar evolution calculation also predicts presupernova mass loss due to an off-centre silicon deflagration flash, which suggests that supernovae from extremely stripped cores may show signs of interactions with circumstellar material., Comment: 15 pages, 15 figures, submitted to MNRAS

© 2018 EPE Association. The DFIG and the BDFRM have very similar dynamic equations, however the BDFRM's complex flux coupling produces machine parameters very different to the DFIG. These parameter differences result in different intrinsic machine behaviour under fault conditions. This paper develops and uses a simple model to explain the fault performance differences between the machines, and then verifies these predictions using a combination of simulation and experimental results. The general conclusion is that the intrinsic large leakage inductances of the BDFRM assist with protecting the rotor side converter during grid side fault conditions.

The evolutionary pathways of core-collapse supernova progenitors at the low-mass end of the spectrum are beset with major uncertainties. In recent years, a variety of evolutionary channels has been discovered in addition to the classical electron capture supernova channel of super-AGB stars. The few available progenitor models at the low-mass end have been studied with great success in supernova simulations as the peculiar density structure makes for robust neutrino-driven explosions in this mass range. Detailed nucleosynthesis calculations have been conducted both for models of electron capture supernovae and low-mass iron core supernovae and revealed an interesting production of the lighter trans-iron elements (such as Zn, Sr, Y, Zr) as well as rare isotopes like Ca-48 and Fe-60. We stress the need to explore the low-mass end of the supernova spectrum further and link various observables to understand the diversity of explosions in this regime., Comment: 7 page, 3 figures, proceedings of the conference "The AGB-Supernova Mass Transition", to appear in Memorie della Societ\`a Astronomica Italiana

The evolutionary pathways of core-collapse supernova progenitors at the low-mass end of the spectrum are beset with major uncertainties. In recent years, a variety of evolutionary channels has been discovered in addition to the classical electron capture supernova channel of super-AGB stars. The few available progenitor models at the low-mass end have been studied with great success in supernova simulations as the peculiar density structure makes for robust neutrino-driven explosions in this mass range. Detailed nucleosynthesis calculations have been conducted both for models of electron capture supernovae and low-mass iron core supernovae and revealed an interesting production of the lighter trans-iron elements (such as Zn, Sr, Y, Zr) as well as rare isotopes like Ca-48 and Fe-60. We stress the need to explore the low-mass end of the supernova spectrum further and link various observables to understand the diversity of explosions in this regime., Comment: 7 page, 3 figures, proceedings of the conference "The AGB-Supernova Mass Transition", to appear in Memorie della Societ\`a Astronomica Italiana

© 2017 IEEE. In this paper a prototype brushless doubly-fed reluctance machine is investigated which is aimed a meeting commercial machine performance figures. The machine has 4 and 8 pole 3-phase stator windings and a 6 pole radiallylaminated ducted rotor. The machine is investigated using finite element analysis (FEA), static torque tests with DC current excitation, a MATLAB/Simulink model, and experimentally using direct torque control (DTC). The investigations show that the machine can perform and match performance found in commercial industrial drives and is controllable. This is a step forward from the work that has been published because the machine is shown to be of a design that is commercially viable, and controllable using known control techniques adapted for the machine. Most previous reports use proof-of-concept machines or machines that are not suitable for commercial operation. This machine is designed to be more commercial in its design.

© 2017 IEEE. This paper examines several techniques for determining the parameters of the Brushless Doubly Fed Reluctance Machine (BDFRM). Even though the mathematical model for this machine is like that of a double-fed induction machine, the very high leakage inductances prevent the use of the normal locked rotor/unloaded rotor tests. The accuracy of the parameters found is validated by machine testing and comparison with the FEA machine design.

Given a smooth, closed, oriented 4-manifold X and alpha is an element ofH(2)(X, Z) such that alpha . alpha > 0, a closed 2-form omega is constructed, Poincare dual to alpha, which is symplectic on the complement of a finite set of unknotted circles Z. The number of circles, counted with sign, is given by d = (c(1)(s)(2)-3sigma(X)-2chi(X))/4, where s is a certain spin(C) structure naturally associated to omega.

Given a smooth, closed, oriented 4-manifold X and alpha is an element ofH(2)(X, Z) such that alpha . alpha > 0, a closed 2-form omega is constructed, Poincare dual to alpha, which is symplectic on the complement of a finite set of unknotted circles Z. The number of circles, counted with sign, is given by d = (c(1)(s)(2)-3sigma(X)-2chi(X))/4, where s is a certain spin(C) structure naturally associated to omega.

To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall–degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7–38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a 'symbiosis toolkit', with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.

As demand for power increases in rural areas serviced by Single Wire Earth Return (SWER) networks, distribution issues are becoming increasingly evident. Voltage regulation and system capacity concerns are driving utilities toward using smarter compensation devices for network control in an attempt to provide longevity for aging SWER infrastructure. To date, despite increasing complexity in power delivery over SWER, no effective network monitoring solutions have been proposed. This paper examines the case for network monitoring and centralised management of smart compensation devices via Power Line Communications (PLC). After establishing advantages in network monitoring, regulation and maintenance for SWER networks, narrowband and broadband PLC issues are reviewed. The channel capacity of typical SWER conductors is then evaluated and compared to data throughput requirements derived from existing infrastructure to validate the applicability of developing PLC over SWER infrastructure.

The subject matter of the first part of this study is the derivation of coupled bending-torsion relations characterizing the dynamical behaviour of unsymmetrical cross-section beams. This allows for the further definition of a beam element with seven degrees of freedom per node. The numerical results obtained with the FEM are compared to experiment in some section shape cases. In order to characterize the displacement field of considered beams, the method of integrated displacements allows us to consider the so-called secondary effects: longitudinal warping inertia, and shear deformation due to both shearing forces and nonuniform warping. The literature on dynamical flexure and torsion of beams is extensive. Cowper for flexure and Gay-Boudet for torsion introduce integrated displacements. We extend in the following this notion to the study of coupled bending-torsion of an homogeneous straight beam., This article is from 'Proceedings of the International Conference on Recent Advances in Structural Dynamics (2nd) held at the University of Southampton (England) on 9-13 April 1984. Volume 1,' ADA143300, p109-117.

The study of coupled flexure-torsion of beams by means of a finite element procedure needs the foregoing knowledge of a set of coefficients to be introduced in the corresponding program., This article is from 'Proceedings of the International Conference on Recent Advances in Structural Dynamics (2nd) held at the University of Southampton (England) on 9-13 April 1984. Volume 1,' AD-A143 300, p119-125.

Udgivelsesdato: 1988-Aug, The membrane protein CD4 is commonly found on mature T cells specific for antigen in association with class II major histocompatibility complex (MHC; Ia) proteins. This correlation has led to the suggestion that CD4 binds to a monomorphic region of the Ia molecule on the antigen-presenting cell (APC) and functions either by enhancing interaction between the T cell and the APC, or conversely, by transducing negative signals to the T cell. To address this hypothesis, we have made use of sublines from an unusual T hybrid that is class I MHC restricted but also CD4+. By incorporating purified MHC proteins into a planar membrane system, we show that different Ia molecules can greatly enhance the ability of a CD4+ but not a CD4- variant of this class I-restricted T hybrid to respond to isolated class I molecules. T-cell responses can be strongly augmented by the concurrent expression of CD4 on the T cell and any of four different Ia proteins on planar membranes, thus supporting the idea that CD4 binds to a monomorphic region of the Ia molecule and increases the avidity with which the T cell can interact with its target.

Udgivelsesdato: 1988-Aug, The membrane protein CD4 is commonly found on mature T cells specific for antigen in association with class II major histocompatibility complex (MHC; Ia) proteins. This correlation has led to the suggestion that CD4 binds to a monomorphic region of the Ia molecule on the antigen-presenting cell (APC) and functions either by enhancing interaction between the T cell and the APC, or conversely, by transducing negative signals to the T cell. To address this hypothesis, we have made use of sublines from an unusual T hybrid that is class I MHC restricted but also CD4+. By incorporating purified MHC proteins into a planar membrane system, we show that different Ia molecules can greatly enhance the ability of a CD4+ but not a CD4- variant of this class I-restricted T hybrid to respond to isolated class I molecules. T-cell responses can be strongly augmented by the concurrent expression of CD4 on the T cell and any of four different Ia proteins on planar membranes, thus supporting the idea that CD4 binds to a monomorphic region of the Ia molecule and increases the avidity with which the T cell can interact with its target.

Udgivelsesdato: 1988-Aug, The membrane protein CD4 is commonly found on mature T cells specific for antigen in association with class II major histocompatibility complex (MHC; Ia) proteins. This correlation has led to the suggestion that CD4 binds to a monomorphic region of the Ia molecule on the antigen-presenting cell (APC) and functions either by enhancing interaction between the T cell and the APC, or conversely, by transducing negative signals to the T cell. To address this hypothesis, we have made use of sublines from an unusual T hybrid that is class I MHC restricted but also CD4+. By incorporating purified MHC proteins into a planar membrane system, we show that different Ia molecules can greatly enhance the ability of a CD4+ but not a CD4- variant of this class I-restricted T hybrid to respond to isolated class I molecules. T-cell responses can be strongly augmented by the concurrent expression of CD4 on the T cell and any of four different Ia proteins on planar membranes, thus supporting the idea that CD4 binds to a monomorphic region of the Ia molecule and increases the avidity with which the T cell can interact with its target.