Resonant Branch Research Articles

HF Multiresonant Electronic Ballast for Fluorescent Lamps With Constant Filament Preheat Voltage

A novel HF multiresonant ballast for fluorescent lamps is analyzed, simulated, and tested experimentally. The ballast includes two major resonant networks. The lamp is driven by a parallel resonance arrangement that acts as a current source. During warm-up the filaments are driven by a secondary winding of a series-resonant inductor. The series resonance branch, which is active during warm-up, feeds the filament and shorts out the voltage across the lamp. Simulation and experimental results suggest that the inherent features of the proposed ballast topology will prolong lamp life.

Dual-Band Planar Monopole Antenna for Multiband Mobile Systems

In this letter, a simple planar monopole antenna with two operating bands for multiband mobile systems application is proposed. The proposed antenna is composed of two inverted-L branches and an open stub for impedance tuning. Both branches are resonating as quarter-wavelength monopole structures. The antenna covers the 890970-MHz and 16702350-MHz bands. A modified design for 824895-MHz and 14402180-MHz bands can be easily achieved by narrowing the widths of the lower resonant branch and the open stub. Both simulation and experimental results for the antenna characteristics are presented and discussed.

Convergence in gradient systems with branching of equilibria

The basic model is a semilinear elliptic equation with coercive non-linearity: in , on , where is a bounded smooth domain. The main hypothesis about resonance branching is as follows: if a branching of equilibria occurs at a point with -dimensional kernel of the linearized operator , then the branching subset at is a locally smooth -dimensional manifold. For the first result on the stabilization to a single equilibrium is due to Zelenyak (1968). It is shown that Zelenyak's approach, which is based on the analysis of Lyapunov functions, can be extended to general gradient systems in Hilbert spaces with smooth resonance branching. The case of asymptotically small non-autonomous perturbations of such systems is also considered. The approach developed here represents an alternative to Hale's stabilization method (1992) and other similar techniques in the theory of gradient systems. Bibliography: 32 titles.

Spin susceptibility in bilayered cuprates: Resonant magnetic excitations

We study the momentum and frequency dependences of the dynamical spin susceptibility in the superconducting state of bilayer cuprate superconductors. We show that there exists a resonance mode in the odd as well as the even channel of the spin susceptibility, with the even mode being located at higher energies than the odd mode. We demonstrate that this energy splitting between the two modes arises not only from a difference in the interaction, but also from a difference in the free-fermion susceptibilities of the even and odd channels. Moreover, we show that the even resonance mode disperses downward at deviations from $\mathbf{Q}=(\ensuremath{\pi},\ensuremath{\pi})$. In addition, we demonstrate that there exists a second branch of the even resonance, similar to the recently observed second branch (the ${Q}^{*}$ mode) of the odd resonance. Finally, we identify the origin of the qualitatively different doping dependence of the even and odd resonances. Our results suggest further experimental tests that may finally resolve the longstanding question regarding the origin of the resonance peak.

Experimental investigation of coupled vibrations in piezoelectric cylindrical shells

An experimental investigation of the electromechanical properties of radially polarized thin-walled piezoelectric ceramic cylinders as a function of the height-to-diameter aspect ratio is presented. The focus of this investigation is on the lowest order axially symmetric modes of vibration for cylinders with free ends having aspect ratio less than 3 with emphasis on the region of strongest coupling around aspect ratio π∕2. The resonance frequencies and coupling coefficients are presented vs aspect ratio and quantify the lower, upper, and an intermediate resonance branch. It is shown that the intermediate branch is flexural in origin and clearly crosses the so-called “dead zone,” which is an inadequacy of the membrane theory applied to the vibration of thin shells [Junger and Rosato, J. Acoust. Soc. Am., 26, 709–713 (1954)]. The coupling coefficient for the lower branch is shown to drop to zero at h∕2a=π∕2, whereas the coupling coefficient associated with the upper branch reaches a maximum at an aspect ratio near this region. As an example of the practical application of this study, the performance of two underwater electroacoustic transducers comprised of cylindrical elements having different aspect ratios is reported.

A Compact Multiband Planar Antenna for Mobile Handsets

A novel compact planar antenna is presented in this letter, which can operate in five bands: GSM (890-960 MHz), DCS (1710-1880 MHz), PCS (1850-1990 MHz), UMTS (1920-2170 MHz), and WLAN (2400-2484 MHz). Consisting of three resonant branches and one tuning branch, the antenna occupies an area of 38.5 times 15 mm2. Due to its two-dimensional (2-D) structure, the antenna is directly printed on the circuit board with low cost, and can be easily integrated with other parts of the circuits of mobile handsets. A prototype has been fabricated and tested, and the experimental results validate the design procedure

Coupling of flexural and longitudinal wave motion in a periodic structure with asymmetrically arranged transverse beams

In this paper we investigate the coupling of flexural and longitudinal wave motions in a waveguide with structural side branches attached at regular intervals. The analysis is based on periodic structure theory, and considers wave transmission in a fully tricoupled and semidefinite periodic assembly of beam-type elements (or plane-wave transmission for normal incidence in a similar plate assembly). Receptances of a composite periodic element with offset resonant beams are derived and used for computing the frequency-dependent propagation constants of three coupled wave types as well as the distribution of motion displacements in each wave type. This is used for calculating the spatial variation of the forced harmonic responses of a semi-infinite periodic structure to point excitations by a longitudinal force and by a moment. Numerical simulations reveal the complicated wave coupling phenomena, which are clarified by calculating the ratio of flexural and longitudinal kinetic energies in the wave-carrying component for each wave type. In contrast to a corresponding, but uncoupled, system with significant broadband attenuation of flexural waves, the numerical results further show that the flexural-longitudinal wave coupling in a system with resonant side branches results in a highly enhanced wave transmission with very little attenuation from element to element.

High‐frequency Alfvén waves in multi‐ion coronal plasma: Observational implications

We investigate the effects of high‐frequency (of order ion gyrofrequency) Alfvén and ion‐cyclotron waves on ion emission lines by studying the dispersion of these waves in a multi‐ion coronal plasma. For this purpose we solve the dispersion relation of the linearized multifluid and Vlasov equations in a magnetized multi‐ion plasma with coronal abundances of heavy ions. We also calculate the dispersion relation using nonlinear one‐dimensional hybrid kinetic simulations of the multi‐ion plasma. When heavy ions are present the dispersion relation of parallel propagating Alfvén cyclotron waves exhibits the following branches (in the positive Ω − k quadrant): right‐hand polarized nonresonant and left‐hand polarized resonant branch for protons and each ion. We calculate the ratio of ion to proton velocities perpendicular to the direction of the magnetic field for each wave modes for typical coronal parameters and find strong enhancement of the heavy ion perpendicular fluid velocity compared with proton perpendicular fluid velocity. The linear multifluid cold plasma results agree with linear warm plasma Vlasov results and with the nonlinear hybrid simulation model results. In view of our findings we discuss how the observed nonthermal line broadening of minor ions in coronal holes may relate to the high‐frequency wave motions.

Mitigation of Multi-Oscillation in a Low Voltage Colpitts Crystal Oscillator

A variation of the Colpitts crystal oscillator based on a modification of the Butler structure and capable of driving the quartz crystal when the power supply has a low voltage value is presented. The addition of a grounded inductor with an appropriate value to the Colpitts circuit, without the need of a series resonance branch, is a non-bridged single solution that improves the excitation gradient of the crystal and, moreover, the spectral purity of the generated wave is enhanced. Also, it is reduced the circuit sensitivity with respect to crystal parameters. The resulting circuit requires only a reduced number of components, thus being suitable to be implemented as analogue integrated circuits.

Comparative study of ESR spectra in incommensurate antiferromagnets

The electron spin resonance is studied for noncollinear low-dimensional antiferromagnets RbMnBr3 and RbFe(MoO4)2 in a wide range of frequencies and fields. Both compounds have incommensurate spin structures appearing due to a low-symmetry distortion of an ideal hexagonal crystal lattice. Magnetic field applied in the spin plane induces a first-order transition into the commensurate phase. The low-energy resonance branch corresponding to a uniform oscillation of the spin system in the easy plane is observed in the two compounds in both incommensurate and commensurate phases, with a dramatic change of the spectra taking place near the transition field. The resonance spectrum of a nearly commensurate spin structure with long-wave modulations is analyzed in clean and dirty limits in the framework of a hydrodynamic approach. The resonance branch with steep field dependence in the incommensurate state is attributed to the acoustic mode with the gap resulted from pinning of local domain walls (discommensurations) on defects of the crystal structure.

Chaotic Third Sound Resonances

There are three independent phenomena that compete to determine the line shapes of third sound resonances in a circular cavity. First, anharmonic terms in the hydrodynamic equations of motion lead to the usual hysteresis on a mugti-valued response function. Second, wave coupling to vortices pinned in the film modify the resonant frequency as changes in the persistent current are induced. Finally, nonlinear dissipation can lead to saturation. The first two of these have been observed to resugt in continuous (not just transient) temporal behavior of the resonance amplitude with a fixed drive. Both cyclical and chaotic behaviors have been observed. The effects are dependent on the ability of the driven wave to either accelerate or decelerate the persistent current onto different amplitude branches of the mugti-valued resonance.

Circular Polarization of Ion Fluorescence Completing the Analysis of Resonant Xe*4d5/2−16pAuger Decay

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.e., branching ratios and relative phases of the Auger decay amplitudes.

Modelling and quantitative direct digital control for a DSP-based soft-switching-mode rectifier

The dynamic modelling and digital controller design for a soft-switching mode rectifier (SSMR) are presented. First, the design and implementation of an SSMR are described. This SSMR is formed from the conventional boost-type SMR by adding an auxiliary resonant branch, and zero-voltage-transition (ZVT) soft switching is achieved by applying suitably delayed pulse width modulation (PWM) signals to the main and auxiliary switches. In addition to the power circuit, sophisticated control is indispensable for the SSMR to have good sinusoidal line current tracking performance under a well-regulated DC output voltage. In dealing with the current control loop, the small-signal model is first derived using a state-space averaging method, and accordingly, the digital current-controlled PWM scheme is designed. As to the voltage control loop, its dynamic model is first estimated from measurements. Then, a quantitative design procedure is developed to find the parameters of the digital voltage controller according to the prescribed control specifications. The PWM switching scheme and the designed controllers of the SSMR are realised digitally using a DSP-based control computer. The effectiveness of the designed controllers is verified by some simulation and experimental results.

The15N(α,γ)19Freaction and nucleosynthesis of19F

Several resonances in the $^{15}$N($\alpha$,$\gamma$)$^{19}$F reaction have been investigated in the energy range between 0.6 MeV and 2.7 MeV. Resonance strengths and branching ratios have been determined. High sensitivity could be obtained by the combination of the {\sc{dynamitron}} high current accelerator, the windowless gas target system {\sc{rhinoceros}}, and actively shielded germanium detectors. Two levels of $^{19}$F could be observed for the first time in the ($\alpha$,$\gamma$) channel, and several weak branchings below the detection limits of previous experiments were measured. Two observed resonances correspond to $\alpha$-cluster states in $^{19}$F which have been assigned unambiguously. The astrophysical reaction rate is derived from this set of resonance strengths.

Analysis and design of a multiple-loop control system for a hybrid active filter

This paper investigates the control of a hybrid active filter consisting of a single tuned resonant branch and an active element. This filter is capable of suppressing multiple harmonics using a multiple-loop control system. Linear continuous-time models are first developed in the dq reference frame. This results in a two-input/two-output system with cross coupling. The continuous model is discretized and the design of a multiple-loop discrete-time controller is examined. Wideband current feedback loops are shown to affect the coupling between the d- and q-axis controllers and provide a resistance-like damping effect. Variations in stability with processing delay times are examined. Finally, this work is extended to include narrowband harmonic specific controls. The results of the control study are confirmed by simulation and experimental results.

Photoionization of Be-like neon (Ne VII) from the low-lying states: Energies, widths, branching ratios, and oscillator strengths of the1s−2presonances

Seventeen-state close-coupling calculations are performed on the photoionization near the 1 s-2 p resonance region from the terms belonging to the configurations 1s 2 2s 2 ,1 s 2 2s2p, and 1s 2 2p 2 , of Be-like neon ions, Ne VII. The calculations include the total and partial photoionization cross sections and the contributions of the main ionization channels to the partial cross sections. The resonance energies, widths, and branching ratios of the 1s-2 p core-excited states are determined from these cross sections. The resonance oscillator strengths of the corresponding 1s-2 p transitions from Ne VII low-lying states are also obtained by integrating the photoionization cross sections. Our theoretical resonance energies, widths, and branching ratios are compared with existing experiments on the Auger spectra and other theoretical results. The calculated resonance energies are in rather good agreement with the latest experiment on the Auger spectra. For the autoionization width, good agreement is also found with recent theoretical results wherever available obtained using a saddle-point complex-rotation method.

Two-proton events in the17F(p,2p)16Oreaction

In a recent experimental study (Gomez del Campo et al, PRL 86, 43 (2001)) of the reaction 17F(p,2p)16O, two-proton events were measured from excitations near a 1-, E*=6.15 MeV state in 18Ne. We calculate by means of R-matrix theory the resonant two-proton production cross section and branching ratios. We conclude that it is unlikely that two-proton production via population of the 1- state is sufficient to explain the observed two-proton events. Alternative sources of such events are discussed.

Resonant photoionization cross sections and branching ratios for atomic oxygen

Total and partial photoionization cross sections for the ejection of either a $2p$ or a $2s$ electron from the ground ${2s}^{2}{2p}^{4}{}^{3}P$ state of atomic oxygen have been investigated using the R-matrix method. Cross sections are dominated by Rydberg series of autoionizing resonances converging to several ionic states. The autoionizing states are analyzed and identified using a procedure of eigenphase gradients. Comparison of our results with available previous calculations and experiments is shown to lead to some interesting conclusions regarding the importance of electron correlation and normalization of the measured relative cross sections. Our calculation removed long-standing discrepancy between theory and experiment regarding the shape of photoionization cross section near the ${}^{2}{P}^{o}$ threshold. The calculated branching ratios for the production of ${}^{4}{S}^{o},{}^{2}{D}^{o},$ and ${}^{2}{P}^{o}$ states at 584 and $304 \mathrm{\AA{}}\mathrm{}$ show good agreement with experiments.

Energetic particle effects as an explanation for the low frequencies of Alfvén modes in the DIII-D tokamak

During beam injection in the DIII-D tokamak, modes with lower frequencies than expected for toroidicity induced Alfvén eigenmodes (TAEs) are often observed. The experimental `TAE' frequency is often ≈0.8 of the nominal theoretical frequency of the TAE, fTAE, while the typical frequency of beta induced Alfvén eigenmodes (BAEs) is (0.2-0.4)fTAE. An analysis is presented of an unstable discharge with a high n stability code, HINST, that includes the effect of energetic ions on mode frequency. The analysis shows that the experimental `TAE' and `BAE' could be resonant branches of the TAE and the kinetic ballooning mode, respectively.

Design of a novel ZVT soft-switching chopper

This paper presents a simple soft-switching chopper scheme with fixed timing control. A near-zero-voltage transition (near-ZVT) switching condition is realized by adding one auxiliary resonant snubber branch to a full-bridge two-quadrant chopper. The turn-off loss is reduced by lossless snubber capacitors in parallel with the main switches. The proposed design approach is to realize true ZVT at the rated load and near-ZVT under all other load current conditions. Computer simulation and hardware experiments have been implemented to verify the proposed concept, and the resulting voltage and current waveforms are shown from 30% to 150% load conditions in this paper. Under near-ZVT switching, the switching loss and dv/dt of the power device can be significantly reduced, and the reverse recovery problem of main switches can be avoided as compared to the hard-switching case. The design criteria for the resonant components are described with a practical example that has been used in a commercial magnetic levitation system. Under different load current conditions, the proposed design methodology has been fully verified with simulation and experimental results.