Possible shunt compensation strategies based on conservative power theory

Considering the Conservative Power Theory (CPT), this paper proposes some novel compensation strategies for shunt passive or active devices. The CPT current decompositions result in several current terms, which are associated with specific physical phenomena (average power consumption P, energy storage Q, load and source distortion D, unbalances N). These current components were used in this work for the definition of different current compensators, which can be selective in terms of minimizing particular disturbing effects. Compensation strategies for single and three-phase four-wire circuits have also been considered. Simulation results have been demonstrated in order to validate the possibilities and performance of the proposed strategies. © 2010 IEEE.

Shunt active compensation based on the Conservative Power Theory current's decomposition

Considering the operation of shunt active compensators, such as active power filters, this paper proposes possible compensation strategies by means of the recent formulation of the Conservative Power Theory (CPT). The CPT current's decomposition results in several current components, which are associated with specific load characteristics (power transfer, energy storage, unbalances and/or non linearities). These current components are used for the definition of different compensation strategies, which can be selective in terms of minimizing particular disturbing effects. In order to validate the applicability of these new compensation strategies, simulation and experimental results for three-phase four-wire systems are presented. © 2011 IEEE.

Application of Conservative Power Theory to load and line characterization and revenue metering

This paper proposes a set of performance factors for load characterization and revenue metering. They are based on the Conservative Power Theory, and each of them relates to a specific load non-ideality (unbalance, reactivity, distortion). The performance factors are capable to characterize the load under different operating conditions, considering also the effect of non-negligible line impedances and supply voltage deterioration. © 2012 IEEE.

Cálculo K: uma abordagem alternativa para a relatividade especial

In this paper we present an alternative approach due to Bondi for the special theory of relativity. During the development, we analyse the Bondi diagrams, visual resources from which we can take some information about the analysed systems, and we discuss the K factor of Bondi's theory, which is in the core of this work. We then discuss some of the main results obtained from Einstein's special theory of relativity such as the time dilation, spatial contraction and simultaneity of spatially separated events, besides the Lorentz transformations. We also show other two important results in physics coming from K calculus: the relativistic linear momentum and the total relativistic energy.

The Epstein-Glaser causal approach to the light-front QED(4). I: Free theory

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Non-renormalization conditions for four-gluon scattering in supersymmetric string and field theory

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Constant Pioneers: The Citation Frontiers of Indexing Theory in the ISKO International Proceedings

Presents a citation analysis of indexing research in the two Proceedings. Understanding that there are different traditions of research into indexing, we look for evidence of this in the citing and cited authors. Three areas of cited and citing authors surface, after applying Price's elitism analysis, each roughly corresponding to geographic distributions.

Analytic perturbation theory for bound states in the transfer matrix spectrum of weakly correlated lattice ferromagnetic spin systems

We consider general d-dimensional lattice ferromagnetic spin systems with nearest neighbor interactions in the high temperature region ('beta' << 1). Each model is characterized by a single site apriori spin distribution taken to be even. We also take the parameter 'alfa' = ('S POT.4') - 3 '(S POT.2') POT.2' > 0, i.e. in the region which we call Gaussian subjugation, where ('S POT.K') denotes the kth moment of the apriori distribution. Associated with the model is a lattice quantum field theory known to contain a particle of asymptotic mass -ln 'beta' and a bound state below the two-particle threshold. We develop a 'beta' analytic perturbation theory for the binding energy of this bound state. As a key ingredient in obtaining our result we show that the Fourier transform of the two-point function is a meromorphic function, with a simple pole, in a suitable complex spectral parameter and the coefficients of its Laurent expansion are analytic in 'beta'.

Multibrane solutions in cubic superstring field theory

Using the elements of the so-called KBc gamma subalgebra, we study a class of analytic solutions depending on a single function F(K) in the modified cubic superstring field theory. We compute the energy associated to these solutions and show that the result can be expressed in terms of a contour integral. For a particular choice of the function F(K), we show that the energy is given by integer multiples of a single D-brane tension.

Interstitial doping induced superconductivity at 15.3 K in Nb5Ge3 compound

It is reported superconductivity in Nb5Ge3C0.3, an interstitial carbide compound. The temperature dependence of the electrical resistivity, ac-susceptibility, and heat capacity (HC) indicate that a bulk type-II superconductivity appears at T-C - 15.3 K. Magneto-resistance measurements suggest an upper critical field of B-C2 similar to 10.6 T and a coherence length of xi similar to 55 angstrom at zero temperature. Neutron diffraction analyzes locate the carbon atoms at the interstitial 2b site of the Mn5Si3 type-structure. Heat capacity data below T-C are well described by BCS theory. The size of the jump at T-C is in good agreement with the superconducting volume fraction observed in susceptibility measurements. A Debye temperature and Sommerfeld constant were also extracted from heat capacity data as 343 K and 34 mJ/mol K-2, respectively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730611]

Measurement of the K + - pi + pi - e + - (-) v e form factors and of the pi pi scattering length a 0 0

The quark condensate is a fundamental free parameter of Chiral Perturbation Theory ($chi PT$), since it determines the relative size of the mass and momentum terms in the power expansion. In order to confirm or contradict the assumption of a large quark condensate, on which $chi PT$ is based, experimental tests are needed. In particular, the $S$-wave $pipi$ scattering lengths $a_0^0$ and $a_0^2$ can be predicted precisely within $chi PT$ as a function of this parameter and can be measured very cleanly in the decay $K^{pm} to pi^{+} pi^{-} e^{pm} stackrel{mbox{tiny(---)}}{nu_e}$ ($K_{e4}$). About one third of the data collected in 2003 and 2004 by the NA48/2 experiment were analysed and 342,859 $K_{e4}$ candidates were selected. The background contamination in the sample could be reduced down to 0.3% and it could be estimated directly from the data, by selecting events with the same signature as $K_{e4}$, but requiring for the electron the opposite charge with respect to the kaon, the so-called ``wrong sign'' events. This is a clean background sample, since the kaon decay with $Delta S=-Delta Q$, that would be the only source of signal, can only take place through two weak decays and is therefore strongly suppressed. The Cabibbo-Maksymowicz variables, used to describe the kinematics of the decay, were computed under the assumption of a fixed kaon momentum of 60 GeV/$c$ along the $z$ axis, so that the neutrino momentum could be obtained without ambiguity. The measurement of the form factors and of the $pipi$ scattering length $a_0^0$ was performed in a single step by comparing the five-dimensional distributions of data and MC in the kinematic variables. The MC distributions were corrected in order to properly take into account the trigger and selection efficiencies of the data and the background contamination. The following parameter values were obtained from a binned maximum likelihood fit, where $a_0^2$ was expressed as a function of $a_0^0$ according to the prediction of chiral perturbation theory: f'_s/f_s = 0.133+- 0.013(stat)+- 0.026(syst) f''_s/f_s = -0.041+- 0.013(stat)+- 0.020(syst) f_e/f_s = 0.221+- 0.051(stat)+- 0.105(syst) f'_e/f_s = -0.459+- 0.170(stat)+- 0.316(syst) tilde{f_p}/f_s = -0.112+- 0.013(stat)+- 0.023(syst) g_p/f_s = 0.892+- 0.012(stat)+- 0.025(syst) g'_p/f_s = 0.114+- 0.015(stat)+- 0.022(syst) h_p/f_s = -0.380+- 0.028(stat)+- 0.050(syst) a_0^0 = 0.246+- 0.009(stat)+- 0.012(syst)}+- 0.002(theor), where the statistical uncertainty only includes the effect of the data statistics and the theoretical uncertainty is due to the width of the allowed band for $a_0^2$.

Measurement of K +- pi +- gamma gamma decays

The goal of this thesis was an experimental test of an effective theory of strong interactions at low energy, called Chiral Perturbation Theory (ChPT). Weak decays of kaon mesons provide such a test. In particular, K± → π±γγ decays are interesting because there is no tree-level O(p2) contribution in ChPT, and the leading contributions start at O(p4). At this order, these decays include one undetermined coupling constant, ĉ. Both the branching ratio and the spectrum shape of K± → π±γγ decays are sensitive to this parameter. O(p6) contributions to K± → π±γγ ChPT predict a 30-40% increase in the branching ratio. From the measurement of the branching ratio and spectrum shape of K± → π±γγ decays, it is possible to determine a model dependent value of ĉ and also to examine whether the O(p6) corrections are necessary and enough to explain the rate.About 40% of the data collected in the year 2003 by the NA48/2 experiment have been analyzed and 908 K± → π±γγ candidates with about 8% background contamination have been selected in the region with z = mγγ2/mK2 ≥ 0.2. Using 5,750,121 selected K± → π±π0 decays as normalization channel, a model independent differential branching ratio of K± → π±γγ has been measured to be:BR(K± → π±γγ, z ≥ 0.2) = (1.018 ± 0.038stat ± 0.039syst ± 0.004ext) ∙10-6. From the fit to the O(p6) ChPT prediction of the measured branching ratio and the shape of the z-spectrum, a value of ĉ = 1.54 ± 0.15stat ± 0.18syst has been extracted. Using the measured ĉ value and the O(p6) ChPT prediction, the branching ratio for z =mγγ2/mK2 <0.2 was computed and added to the measured result. The value obtained for the total branching ratio is:BR(K± → π±γγ) = (1.055 ± 0.038stat ± 0.039syst ± 0.004ext + 0.003ĉ -0.002ĉ) ∙10-6, where the last error reflects the uncertainty on ĉ.The branching ratio result presented here agrees with previous experimental results, improving the precision of the measurement by at least a factor of five. The precision on the ĉ measurement has been improved by approximately a factor of three. A slight disagreement with the O(p6) ChPT branching ratio prediction as a function of ĉ has been observed. This mightrnbe due to the possible existence of non-negligible terms not yet included in the theory. Within the scope of this thesis, η-η' mixing effects in O(p4) ChPT have also been measured.

Mode-coupling theory: generalizations, high dimensions and microscopic dynamics

This work contains several applications of the mode-coupling theory (MCT) and is separated into three parts. In the first part we investigate the liquid-glass transition of hard spheres for dimensions d→∞ analytically and numerically up to d=800 in the framework of MCT. We find that the critical packing fraction ϕc(d) scales as d²2^(-d), which is larger than the Kauzmann packing fraction ϕK(d) found by a small-cage expansion by Parisi and Zamponi [J. Stat. Mech.: Theory Exp. 2006, P03017 (2006)]. The scaling of the critical packing fraction is different from the relation ϕc(d)∼d2^(-d) found earlier by Kirkpatrick and Wolynes [Phys. Rev. A 35, 3072 (1987)]. This is due to the fact that the k dependence of the critical collective and self nonergodicity parameters fc(k;d) and fcs(k;d) was assumed to be Gaussian in the previous theories. We show that in MCT this is not the case. Instead fc(k;d) and fcs(k;d), which become identical in the limit d→∞, converge to a non-Gaussian master function on the scale k∼d^(3/2). We find that the numerically determined value for the exponent parameter λ and therefore also the critical exponents a and b depend on the dimension d, even at the largest evaluated dimension d=800. In the second part we compare the results of a molecular-dynamics simulation of liquid Lennard-Jones argon far away from the glass transition [D. Levesque, L. Verlet, and J. Kurkijärvi, Phys. Rev. A 7, 1690 (1973)] with MCT. We show that the agreement between theory and computer simulation can be improved by taking binary collisions into account [L. Sjögren, Phys. Rev. A 22, 2866 (1980)]. We find that an empiric prefactor of the memory function of the original MCT equations leads to similar results. In the third part we derive the equations for a mode-coupling theory for the spherical components of the stress tensor. Unfortunately it turns out that they are too complex to be solved numerically.