Ultrahigh step-up dc-dc converter for distributed generation by three Degrees of Freedom (3DoF) approach

This paper proposes a novel dc-dc converter topology to achieve an ultrahigh step-up ratio while maintaining a high conversion efficiency. It adopts a three degree of freedom approach in the circuit design. It also demonstrates the flexibility of the proposed converter to combine with the features of modularity, electrical isolation, soft-switching, low voltage stress on switching devices, and is thus considered to be an improved topology over traditional dc-dc converters. New control strategies including the two-section output voltage control and cell idle control are also developed to improve the converter performance. With the cell idle control, the secondary winding inductance of the idle module is bypassed to decrease its power loss. A 400-W dc-dc converter is prototyped and tested to verify the proposed techniques, in addition to a simulation study. The step-up conversion ratio can reach 1:14 with a peak efficiency of 94% and the proposed techniques can be applied to a wide range of high voltage and high power distributed generation and dc power transmission.

Bailando con Dioniso: el mito de Leucipo y Daphne de Richard Strauss y Joseph Gregor

Primera parte de un artículo dividido en dos que analiza la profunda reinterpretación que del mito de Dafne llevaron a cabo, a partir del relato alternativo de Partenio de Nicea más que del célebre relato de Ovidio, Richard Strauss y su libretista Joseph Gregor en su versión operística Daphne (1938). El objetivo final es someter a examen la declaración expresa de Strauss sobre el significado de su nueva ópera y si a través de la manipulación del argumento mítico los autores lograron alcanzar su objetivo.

Two-dimensional short surface-waves of an oscillating cylinder with arbitrary shape of cross-section

The 2-D short surface waves produced by a partially submerged cylinder which performsarbitrary oscillating motion are discussed. The uniformly valid solution which is applicableto all kinds of cylinder wall cases at waterline point is obtained. It is pointed out that thesolution obtained by Holford[J] for the vertical oscillating motion of a cylinder is incomplete.The reason why his solution cannot go over to that for the case of vertical cylinder wall atwaterline point is also pointed out.

Measurement of two-photon excitation cross-section of a new symmetric-type fluorene derivative

A new dye, 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene, has been synthesized, which is a D-pi-D symmetrical-type fluorene derivative. The two-photon absorption (TPA) of this new dye has been experimentally studied by comparable two-photon-induced fluorescence method. This new dye has a TPA cross-section of 84 x 10(-50) cm(4) s/photon at 790 nm/13 fs. (c) 2004 Elsevier GmbH. All rights reserved.

Resonant two-photon cross-section calculations for transitions to 4f5d state in Pr3+: YAG using density matrix theory

The density matrix resonant two-photon absorption (TPA) theory is applied to a rare-earth ion-doped laser crystal. TPA cross sections for transitions from the ground state to the first 4f5d state in Pr3+:YAG are calculated. The results indicate the density matrix TPA theory is attractive in studying TPA in laser crystals. (C) 2000 Elsevier Science B.V. All rights reserved.

A fast two-grid and finite section method for a class of integral equations on the real line with application to an acoustic scattering problem in the half-plane

We consider the numerical treatment of second kind integral equations on the real line of the form ∅(s) = ∫_(-∞)^(+∞)▒〖κ(s-t)z(t)ϕ(t)dt,s=R〗 (abbreviated ϕ= ψ+K_z ϕ) in which K ϵ L_1 (R), z ϵ L_∞ (R) and ψ ϵ BC(R), the space of bounded continuous functions on R, are assumed known and ϕ ϵ BC(R) is to be determined. We first derive sharp error estimates for the finite section approximation (reducing the range of integration to [-A, A]) via bounds on (1-K_z )^(-1)as an operator on spaces of weighted continuous functions. Numerical solution by a simple discrete collocation method on a uniform grid on R is then analysed: in the case when z is compactly supported this leads to a coefficient matrix which allows a rapid matrix-vector multiply via the FFT. To utilise this possibility we propose a modified two-grid iteration, a feature of which is that the coarse grid matrix is approximated by a banded matrix, and analyse convergence and computational cost. In cases where z is not compactly supported a combined finite section and two-grid algorithm can be applied and we extend the analysis to this case. As an application we consider acoustic scattering in the half-plane with a Robin or impedance boundary condition which we formulate as a boundary integral equation of the class studied. Our final result is that if z (related to the boundary impedance in the application) takes values in an appropriate compact subset Q of the complex plane, then the difference between ϕ(s)and its finite section approximation computed numerically using the iterative scheme proposed is ≤C_1 [kh log⁡〖(1⁄kh)+(1-Θ)^((-1)⁄2) (kA)^((-1)⁄2) 〗 ] in the interval [-ΘA,ΘA](Θ<1) for kh sufficiently small, where k is the wavenumber and h the grid spacing. Moreover this numerical approximation can be computed in ≤C_2 N log⁡N operations, where N = 2A/h is the number of degrees of freedom. The values of the constants C1 and C2 depend only on the set Q and not on the wavenumber k or the support of z.

Investigation of the two-photon absorption cross-section in perylene tetracarboxylic derivatives: Nonlinear spectra and molecular structure

We investigated the 2PA absorption spectrum of a family of perylene tetracarboxylic derivatives ( PTCDs): bis( benzimidazo) perylene ( AzoPTCD), bis( benzimidazo) thioperylene ( Monothio BZP), n-pentylimidobenzimidazoperylene ( PazoPTCD), and bis( n-butylimido) perylene ( BuPTCD). These compounds present extremely high two-photon absorption, which makes them attractive for applications in photonics devices. The two-photon absorption cross-section spectra of perylene derivatives obtained via Z-scan technique were fitted by means of a sum-over-states ( SOS) model, which described with accuracy the different regions of the 2PA cross-section spectra. Frontier molecular orbital calculations show that all molecules present similar features, indicating that nonlinear optical properties in PTCDs are mainly determined by the central portion of the molecule, with minimal effect from the lateral side groups. In general, our results pointed out that the differences in the 2PA cross-sections among the compounds are mainly due to the nonlinearity resonance enhancement.

Measurement of the hadronic activity in events with a Z and two jets and extraction of the cross section for the electroweak production of a Z with two jets in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the production cross section for a W boson and two b jets in pp collisions at root s=7 TeV

The production cross section for a Wboson and two b jets is measured using proton-proton collisions at v root s = 7 TeV in a data sample collected with the CMS experiment at the LHC corresponding to an integrated luminosity of 5.0 fb(-1). The W + bbevents are selected in the W..decay mode by requiring a muon with transverse momentum pT> 25GeVand pseudorapidity |eta| < 2.1, and exactly two b-tagged jets with pT> 25GeVand |eta| < 2.4. The measured W + bbproduction cross section in the fiducial region, calculated at the level of final-state particles, is s(pp. W + bb) xB(W..) = 0.53 +/- 0.05 (stat.) +/- 0.09 (syst.) +/- 0.06 (theo.) 0.01 (lum.) pb, in agreement with the standard model prediction. In addition, kinematic distributions of the W + bbsystem are in agreement with the predictions of a simulation usingMadGraphandpythia. (C) 2014 The Authors. Published by Elsevier B. V.

Cesarean section and increased body mass index in school children: two cohort studies from distinct socioeconomic background areas in Brazil

Abstract Background Recent studies have raised controversy regarding the association between cesarean section and later obesity in the offspring. The purpose of this study was to assess the association of cesarean section with increased body mass index (BMI) and obesity in school children from two Brazilian cities with distinct socioeconomic backgrounds. Methods Two birth cohorts respectively born in 1994 in Ribeirao Preto, a wealthy city in Southeast, and in 1997/98 in Sao Luis, a less wealthy city in Northeast of Brasil, were evaluated. After birth, 2,846 pairs of mothers-newborns were evaluated in Ribeirao Preto and 2,542 in Sao Luis. In 2004/05, 790 children aged 10/11 years were randomly reassessed in Ribeirao Preto and 673 at 7/9 years in Sao Luis. Information on type of delivery, maternal and child characteristics, socioeconomic position and anthropometric measurements were collected after birth and at school age. Obesity was defined as BMI ≥ 95th percentile at school age. Results Obesity rate was 13.0% in Ribeirao Preto and 2.1% in Sao Luis. Cesarean section was associated with obesity and remained significant after adjustment only in Ribeirao Preto [OR = 1.74 (95% CI: 1.04; 2.92)]. The association between cesarean section and BMI remained significant after adjustment for maternal schooling, maternal smoking during pregnancy, duration of breastfeeding, gender, birth weight and gestational age, type of school and, only in Sao Luis, pre-pregnancy maternal weight. In Ribeirao Preto children born by cesarean section had BMI 0.31 kg/m2 (95%CI: 0.11; 0.51) higher than those born by vaginal delivery. In Sao Luis BMI of children born by cesarean section was 0.28 kg/m2 higher (95%CI: 0.08; 0.49) than those born by vaginal delivery. Conclusion A positive association between cesarean section and increased BMI z-score was demonstrated in areas with different socioeconomic status in a middle-income country.