133,855 research outputs found

    Design of Prototype Dynamic Ac Power Machine with Equivalent Circuit Modeling (Torque Speed Curve of Induction Motor 1,1, Kw)

    Full text link
    Squirrel cage induction motors are widely used in electric motor drives due to their satisfactory mechanical characteristics (torque, current, overloading) and small dimensions, as well as their low price. When starting an induction motor, a large current is required for magnetizing its core, which results in a low power factor, rotor power losses and a temperature rise in the windings. None of these parameters should reach values beyond certain limits until the motor reaches nominal speed. The speed of an induction motor 1,1kW is affected very little by fluctuations of voltage. The greater the supply voltage of the motor, the induction motor's speed will increase. The torque values (Tstart, TSmax and Tmax) are affected by the value of the motor supply voltage: (Vp-nl : 132.8, Tstart1 : 7.4, T S-max1 : 0.4, Tmax1 : 9.9) V, (Vp-nl : 127.0, Tstart2 : 4.8, T S-max1 : 0.3, Tmax1 : 8.4) V and (Vp-nl : 121.3, Tstart3 : 3.3, T S-max3 : 0.2, Tmax3 : 7.1) V. Stator current (IL-nl ; 2.5, 2.2, 1.9 ) Amp rises gradually on account of the increase in magnetising current (Im : 2.5, 2.2, 1.9) Amp. The magnetising current required to produce the stator flux. The component of the stator current which provides the ampere-turns balancing the rotor ampere-turns will steadily diminish as the rotor current (IL-nl) decrease with the increase in rotor speed (nr).&nbsp

    Gauged BPS baby Skyrmions with quantised magnetic flux

    Full text link
    A new type of gauged BPS baby Skyrme model is presented, where the derivative term is just the Schroers current (i.e., gauge invariant and conserved version of the topological current) squared. This class of models has a topological bound saturated for solutions of the pertinent Bogomolnyi equations supplemented by a so-called superpotential equation. In contrast to the gauged BPS baby Skyrme models considered previously, the superpotential equation is linear and, hence, completely solvable. Furthermore, the magnetic flux is quantized in units of 2π2\pi, which allows, in principle, to define this theory on a compact manifold without boundary, unlike all gauged baby Skyrme models considered so far.Comment: Latex, 17 page

    Integer Discontinuity of Density Functional Theory

    Full text link
    Density functional approximations to the exchange-correlation energy of Kohn-Sham theory, such as the local density approximation and generalized gradient approximations, lack the well-known integer discontinuity, a feature that is critical to describe molecular dissociation correctly. Moreover, standard approximations to the exchange-correlation energy also fail to yield the correct linear dependence of the ground-state energy on the number of electrons when this is a non-integer number obtained from the grand canonical ensemble statistics. We present a formal framework to restore the integer discontinuity of any density functional approximation. Our formalism derives from a formula for the exact energy functional and a new constrained search functional that recovers the linear dependence of the energy on the number of electrons.Comment: 5 pages, 2 figure

    Integrable subsystem of Yang--Mills dilaton theory

    Get PDF
    With the help of the Cho-Faddeev-Niemi-Shabanov decomposition of the SU(2) Yang-Mills field, we find an integrable subsystem of SU(2) Yang-Mills theory coupled to the dilaton. Here integrability means the existence of infinitely many symmetries and infinitely many conserved currents. Further, we construct infinitely many static solutions of this integrable subsystem. These solutions can be identified with certain limiting solutions of the full system, which have been found previously in the context of numerical investigations of the Yang-Mills dilaton theory. In addition, we derive a Bogomolny bound for the integrable subsystem and show that our static solutions are, in fact, Bogomolny solutions. This explains the linear growth of their energies with the topological charge, which has been observed previously. Finally, we discuss some generalisations.Comment: 25 pages, LaTex. Version 3: appendix added where the equivalence of the field equations for the full model and the submodel is demonstrated; references and some comments adde

    Theory of fluorescence excitation spectra using anharmonic-coriolis coupling in S1 and internal conversion to S0. I. General formalism

    Get PDF
    A treatment of one- or two-photon fluorescence excitation spectra is described using the vibration–rotation coupling of zeroth order states in the excited electronic state and nonadiabatic coupling to the ground state. Using perturbation theory, experimental harmonic frequencies, an anharmonic force field, and various theoretical Coriolis coupling constants, a quasistationary molecular eigenstate in an excited electronic state S1 is first calculated. The S1 eigenstate is then coupled via the nonadiabatic nuclear kinetic energy operator (internal conversion) to rovibronic states in the ground state manifold, the latter states approximated in a simple manner. A search algorithm is used to select the S1 dark states and the S0 states. Both the perturbation theory coefficient and the Franck–Condon factors are employed in the evaluation function used in the search. The results are applied in part II to the channel three problem in benzene

    Evidence for massive neutrinos from CMB and lensing observations

    Full text link
    We discuss whether massive neutrinos (either active or sterile) can reconcile some of the tensions within cosmological data that have been brought into focus by the recently released {\it Planck} data. We point out that a discrepancy is present when comparing the primary CMB and lensing measurements both from the CMB and galaxy lensing data using CFHTLenS, similar to that which arises when comparing CMB measurements and SZ cluster counts. A consistent picture emerges and including a prior for the cluster constraints and BAOs we find that: for an active neutrino model with 3 degenerate neutrinos, mν=(0.320±0.081)eV\sum m_{\nu}= (0.320 \pm 0.081)\,{\rm eV}, whereas for a sterile neutrino, in addition to 3 neutrinos with a standard hierarchy and mν=0.06eV\sum m_{\nu}= 0.06\,{\rm eV}, mν,sterileeff=(0.450±0.124)eVm_{\nu, \, \rm sterile}^{\rm eff}= (0.450 \pm 0.124)\,{\rm eV} and ΔNeff=0.45±0.23\Delta N_{\rm eff} = 0.45 \pm 0.23. In both cases there is a significant detection of modification to the neutrino sector from the standard model and in the case of the sterile neutrino it is possible to reconcile the BAO and local H0H_0 measurements. However, a caveat to our result is some internal tension between the CMB and lensing/cluster observations, and the masses are in excess of those estimated from the shape of the matter power spectrum from galaxy surveys.Comment: 5 pages, 3 figures, clarifications added, comparison with WMAP-9 plus high-l added, version accepted in Physical Review Letter

    Forward-backward multiplicity correlations in the wounded nucleon model

    Full text link
    The forward-backward multiplicity correlation strength is calculated for arbitrary nucleus-nucleus collision in the framework of the wounded nucleon model. Discussion of our results in the context of the recent STAR data in Au+Au collisions at sqrt{s}=200 GeV is presented. It is suggested that the observed (i) growth of the correlation coefficient with centrality and (ii) approximately flat pseudorapidity dependence of the correlation strength for central collisions are due to the fluctuations of the number of wounded nucleons at a given centrality bin.Comment: 15 pages, 4 figures, accepted for publication in Phys. Rev. C. Changed content: STAR data included, extended discussion, added reference

    Oxygen Activation by Mononuclear Mn, Co, and Ni Centers in Biology and Synthetic Complexes

    Get PDF
    The active sites of metalloenzymes that catalyze O2-dependent reactions generally contain iron or copper ions. However, several enzymes are capable of activating O2 at manganese or nickel centers instead, and a handful of dioxygenases exhibit activity when substituted with cobalt. This minireview summarizes the catalytic properties of oxygenases and oxidases with mononuclear Mn, Co, or Ni active sites, including oxalate-degrading oxidases, catechol dioxygenases, and quercetin dioxygenase. In addition, recent developments in the O2 reactivity of synthetic Mn, Co, or Ni complexes are described, with an emphasis on the nature of reactive intermediates featuring superoxo-, peroxo-, or oxo-ligands. Collectively, the biochemical and synthetic studies discussed herein reveal the possibilities and limitations of O2 activation at these three “overlooked” metals

    An experimental evaluation of cattail (Typha spp.) cutting depths on subsequent regrowth

    Get PDF
    Citation: Moorberg, C. & Ahlers, A. (2020). An experimental evaluation of cattail (Typha spp.) cutting depths on subsequent regrowth.Cattail (Typha spp.) expansions can negatively affect both native wetland flora and fauna diversity, and active management is often needed to maintain wetland habitat quality. Cattail removal is often non-permanent, requiring repeated treatments to retard reestablishment. Mechanically cutting cattails is a common management technique, but it is unclear what cutting depths are optimal. We conducted an experiment at Cheyenne Bottoms Wildlife Area (Kansas, USA) during 2017-2019 to address this question. We established a randomized complete block design experiment with four blocks and three cutting treatments in July 2017, including cattail cut above water, cut below water, and an uncut control. We hypothesized that cattails cut below water would have reduced gas-exchange capabilities due to flooded aerenchyma. We quantified emergent stem densities in each plot in September 2017 to assess the effectiveness of simulated management actions. The above water treatment had significantly fewer total stems than both the control (p = 0.0003) and the below water treatments (p = 0.0203). The above water treatment also had significantly fewer stems than the control treatment (p = 0.0032). Our results suggest that management efforts focused on cutting cattails below water slow cattail reestablishment
    corecore