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The transmission of external jet noise through the double-leaf skin plate of an aircraft cabin fuselage in the presence of external mean flow is analytically studied. An aeroacoustic--elastic theoretical model is developed and applied to calculate the sound transmission loss versus frequency curves. Four different types of acoustic phenomenon (i.e., the mass--air--mass resonance, the standing-wave attenuation, the standing-wave resonance, and the coincidence resonance) for a flat double-leaf plate as well as the ring frequency resonance for a curved double- leaf plate are identified. Independently of the proposed theoretical model, simple closed-form formulas for the natural frequencies associated with the preceding acoustic phenomena are derived using physical principles. Excellent agreement between the model predictions and the closed-form formulas is achieved. Systematical parametric investigation with the model demonstrate that the presence of the mean flow as well as the sound incidence angles substantially affect the sound transmission behavior of the double-leaf structure. The influences of the panel curvature together with cabin internal pressure on jet noise transmission are also significant and should be taken into account when designing aircraft cabin fuselages. DOI: 10.2514/1.42426

Subsynchronous resonance (SSR) performance of various control schemes of a thyristor controlled series compensator (TCSC) has been studied in the previous literature using digital simulation based analyses. With the availability of a modular, high bandwidth (six-sample per cycle), discrete-time model of a TCSC, accurate eigen-analysis of a TCSC compensated system has become feasible. Therefore, we revisit the issue of SSR performance in order to gain additional insight provided by this analytical model. We use the model to assess fixed firing angle delay (FFAD) and synchronous voltage reversal (SVR) under different situations. The performance of synchronization schemes and an output feedback subsynchronous damping controller (SSDC) is also evaluated. The derivation of the model is outlined and validated by comparing the results of eigen-analysis with those obtained by detailed digital simulation. Index Terms--Discrete time systems, dynamic modeling, subsynchronous resonance (SSR), synchronous voltage reversal (SVR), thyristor controlled series compensator (TCSC).

The HVDC converter control can destabilize torsional modes of nearby turbogenerators. The first experience of HVDC-turbine generator torsional interaction was observed in 1977 during field tests at Square Butte. The development of power semiconductors, specially insulated-gate bipolar transistors and gate turnoff thyristors (GTOs) has led to the small power HVDC transmission based on voltage-source converters (VSCs). The self-commutated VSC-based HVDC installations have several advantages compared to conventional HVDC-based online-commutated current source converter. The main objective of this paper is to investigate and present the detailed analysis of subsynchronous resonance (SSR), arising from a VSC-based HVDC system connected close to generating units. The analysis considers different operating modes of the converters. Based on a case study, it is shown that the dc voltage control mode of VSC operation (rectifier/inverter) close to the generator units can contribute positive damping in the torsional-mode frequency range of interest. The investigations of SSR with VSC-based HVDC is carried out based on linear (damping torque and eigenvalue) analysis and nonlinear transient simulation. While the damping torque, eigenvalue analysis, and controller design are based on the D-Q model, the transient simulation considers the D IQ model and the three-phase detailed model of VSC using switching functions. The influence of the operating modes of the converters and effects of some important parameters, such as effective short circuit ratio and generator rating are investigated. Index Terms--Damping torque, eigenvalue analysis, HVDC, parameter optimization, transient simulation, voltage-source converters (VSCs).

Determination of strain in resonant column and torsional shear (RC/TS) tests is complicated due to nonuniform stress--strain variation occurring linearly with the radius in a soil specimen in torsion. The equivalent radius approach is adequate when calculating strain at low to intermediate levels, however, the approach is less accurate when performing the tests at higher strains. The stress integration approach involving integration of an assumed soil stress--strain model was developed to account for this problem more precisely. This approach was used to generate the plots of equivalent radius ratio versus strain developed based upon shear modulus and damping. Results showed that the equivalent radius ratio curves converge to a value of approximately 0.8 at low strains and decrease as strain increases. The equivalent radius ratio curves based upon damping decrease to significantly lower values at high strain than curves based upon shear modulus. This study suggests that using the same values of equivalent radius ratio to calculate strains for both shear modulus and damping is not appropriate. The stress integration approach provides an accurate analysis technique for evaluating both modulus and damping behavior of soil, over any range of strains in RC/TS testing. CE Database subject headings: Shear modulus; Damping; Shear strain; Resonance; Hysteresis; Soil dynamics; Dynamic properties; Soil tests.

This paper presents a DSP method that allows decomposing conducted electromagnetic interference (EMI) emissions from different sources in large power electronics systems. The estimation process is carried out by a number of Wiener filters (WFs), which represent all different converter states. These are determined by initial commutation event conditions and propagation paths layout. Filters are fed by a semiconductor power switch voltage or current waveforms regarded as sources of perturbation. The EMI emissions are measured on the line impedance stabilization network (LISN) terminals. Optimal filter adaptation is carried out in the frequency domain by measuring and computing input and cross-power signal spectra. Analysis of a parallel quasi-resonant dc-link voltage inverter (PQRDCLI) is outlined to distinguish filters assigned for inverter operation from those for external dc/dc converter interaction. Experimental results are given to illustrate the WF estimation quality. The possibility of detailed decomposition of the LISN-EMI waveforms is depicted in both time and frequency domains. Comparative analysis of frequency responses for PQRDCLI-Iink voltage changes is given. Index Terms--DC-DC power conversion, electromagnetic interference (EMI), resonant power conversion, Wiener filtering (WF).

A theoretical analysis of corrugated transducers in cylindrical motions is presented. It is shown that an insensitive resonant frequency is present at which the flexure of the central pieces has decreased as the number of pieces has increased.

The development of a robust multichannel hybrid algorithm which is able to process NQR signals from mixtures while also allowing for errors in the assumed amplitudes is reported. The newly developed algorithm provides significantly improved performance compared to existing algorithms in the case when there are multiple polymorphs present and/or when uncertainties in the amplitudes exist.

For the explanation of the enhanced transmission through the perforated metal plate with below-cutoff holes, the eigenoscillations of the double-periodic screen are studied. It is found that the origin of the recently discovered effects is the existence of the eigenoscillations of the interface between the free halfspace and the metal halfspace perforated with double-periodic set of channels and the formation of the corresponding symmetrically and anti-symmetrically coupled 'supermodes' when two such interfaces form a screen of finite thickness. The amplitude and polarization structure of the eigenfields and the behavior of the complex-valued eigenfrequencies depending on the geometry parameters are studied by the mode-matching technique (MMT) both for a finite-thickness screen and for an interface. The symmetrical oscillation of the perforated screen is shown to be the cause of both the well-known phenomenon of total transmission through frequency selective surfaces (FSS), and the recently discovered enhanced transmission through cutoff holes. When the holes shrink, the field pattern of this eigenoscillation transforms from the one concentrated within the holes to that concentrated in the form of Floquet-waves above and below the screen, i.e., out of the holes. In contrast, the antisymmetrical oscillations are always located in frequency near the Floquet-waves grazing points at any hole dimensions and cause the so-called Wood anomalies. Index Terms--Below-cutoff holes, double-periodic metal screen, eigenoscillations, resonant holes, total transmission.

To avoid the acoustic resonance on operating metal halide lamps, an autofrequency-searching method is implemented on the high-frequency electronic ballast. The proposed method allows the use of a high-frequency electronic ballast, making the ballast able to adjust the operating frequency automatically as soon as the acoustic resonance is detected and, consequently, to locate it at a stable frequency. The electronic ballast achieves a high efficiency and a high power density through the employment of a high-frequency resonant inverter with an embedded buck-boost converter for power-factor correction and lamp power regulation. The control strategy is realized by a microprocessor along with the acoustic-resonance detection circuit. The operation of autofrequency searching is illustrated by the experiments on an electronic ballast designed for 70-W metal halide lamps. Index Terms--Acoustic resonance, autofrequency searching, electronic ballast, metal halide lamp.

The analysis of the nonlinear behavior of a power harvester consisting of a circular piezoelectric plate and an electric resistance is reported. The analysis performed on the bases of the von Karman thin circular plate theory showed that the output power exhibits multivaluedness and a jump phenomenon near resonance.

The development of a method to determine the equivalent circuits of broadband transducers with 2 resonances in the frequency band of interest is reported. The application of the method is illustrated by computing and comparing the conductance and susceptance of the equivalent circuits of three types of broadband transducer.

A numerical eigenmode solver is used to analyze the behavior of two-, four-, and six-arm small multielement spherical antennas. The resonant frequency and radiation Q-factor of the natural modes of the shorted antenna structure are determined from eigenmode simulations using perfectly matched layer outer boundaries. The radiation resistance of each eigenmode at resonance is determined using a D feed geometry that excites the modes individually. The impedance response of the antenna when driven on a single arm can then be described as a multipole RLC network, where the component values of the network are directly related to the parameters and relative excitation amplitudes of the various eigenmodes of the antenna. A good match between the modal analysis and the full harmonic simulation is observed, and the analysis also predicts the far-field cross-polarization levels arising from energy radiated by the higher-order modes. The analysis provides physical insight into the multiresonant impedance behavior of these antennas, clearly illustrating their ultimate performance limits and yielding ideas for improved designs. The analysis can be applied towards understanding the behavior of other multielement antenna structures. Index Terms--Q-factor, resonant antennas, small antennas.

Dynamic properties of soils are commonly evaluated at resonance; thus, their variation with frequency is difficult to measure. A nonresonance (NR) method has been recently used for testing soils at low frequencies and strain levels below the linear threshold shear strain. However, the NR method has not been validated with the standard resonant method for different shear strain levels. In this study, the NR method is used to measure the dynamic properties of soils at low and midstrain levels for a maximum frequency bandwidth between 5 and 100 Hz using the resonant-column device. A new transfer function (NTF) equation is introduced to compare the dynamic properties measured using the NR method and the conventional transfer function approach. Experimental results for two sands and a sand--bentonite--mud mixture are presented for different strain and stress confinement levels. Results from the NR method compare well with the standard resonant column method at the resonant frequency if the strain levels are the same. The NTF approach can be used to measure the dependence of phase velocity of shear waves with frequency. However, the NTF method cannot be used to measure the variation of material damping with frequency. On the other hand, the NR method can be used to measure the degradation curves of wave velocity and material damping ratio as a function of frequency. CE Database subject headings: Resonance; Velocity; Damping; Soil dynamics; Soil properties; Soil tests.

A generalized study of the parallel connection of N Class-D parallel resonant (L[C.sub.p]) inverters is presented. Steady-state analysis and design considerations are provided in detail, evaluating the current distribution, output power and efficiency of the circuit as a function of the number, N, of phases. Inductor equivalent series resistance and MOSFET conduction losses are considered in order to foresee and optimize the inverter efficiency. The power supplied to the load can be controlled at constant switching frequency by using the phase displacement of the output voltages of each Class-D leg, although for the interests of this specific application, only one inverter is phase shifted. The applicability of the general analysis is demonstrated on two practical designs with three and five phases, resulting in 400-W and 1-kW high-pressure sodium lamp ballasts, respectively. Index Terms--Conduction losses, electronic ballast, high efficiency, high-power applications, high-pressure sodium (HPS) lamps, mnltiphase parallel resonant inverter, resonant inverters.

Capacitors provide well-known benefits to electric power systems. These benefits include power factor correction, voltage support, release of system capacity, and reduced system losses. As with any piece of electrical equipment, there are a number of application issues that engineers need to be aware of. These issues range from the very basic to the very complex. Most of these application issues can be, and have been, the subject of their own detailed technical papers. This paper does not get into rigorous detail but rather discusses these issues with the goal of making the reader aware of many of the traps one can fall into when applying capacitors. The application issues are addressed based on the authors' experiences working in various capacities (performing power system measurements and studies, performing engineering service failure investigations, advising capacitor sales personnel, consulting with end users, and building custom capacitor banks), thus seeing these problems from many different angles. Index Terms--Capacitors, demand, filters, harmonics, penalties, power factor, resonance, transients.

An ultrawideband stubby antenna that covers all frequency bands between 824 MHz and 6 GHz, which include GSM 850 and 900, GPS, DVB-H US, DCS, PCS, UMTS, BT, WLAN 802.11b/g and WLAN 802.11a, with a VSWR better than 2.7:1 is described in this paper. The design procedure involves obtaining a wideband resonance from 1-6 GHz and using a matching network to compensate for the high capacitance of the antenna at the lower frequency hand below 1 GHz. Parametric studies of this antenna are presented in this paper. The design was experimentally verified by constructing an ultrawidehand antenna with a volume of 5 * 8 * 30 [mm.sup.3]. It is significant that the designed ultrawideband stubby antenna maintained a good impedance matching and radiation efficiency at all bands. An efficiency between 55 ~ 65% is achieved in the lower band including 824 ~ 960 MHz hand required for the GSM 850 and GSM 900 systems, and an efficiency value of 67 ~ 88% is achieved at the rest of the bands starting with the GPS at 1575 MHz in 6 GHz. Index Terms--Matching network, monopole antennas, multihand antennas, wideband antennas.

For the renewable energy sources whose outputs vary continuously, a Z-source current-type inverter has been proposed as a possible buck-boost alternative for grid-interfacing. With a unique X-shaped LC network connected between its dc power source and inverter topology, Z-source current-type inverter is however expected to suffer from compounded resonant complications in addition to those associated with its second-order output filter. To improve its damping performance, this paper proposes the careful integration of Posicast or three-step compensators before the inverter pulse-width modulator for damping triggered resonant oscillations. In total, two compensators are needed for wave-shaping the inverter boost factor and modulation ratio, and they can conveniently be implemented using first-in first-out stacks and embedded timers of modern digital signal processors widely used in motion control applications. Both techniques are found to damp resonance of ac filter well, but for cases of transiting from current-buck to boost state, three-step technique is less effective due to the sudden intermediate discharging interval introduced by its non-monotonic stepping (unlike the monotonic stepping of Posicast damping). These findings have been confirmed both in simulations and experiments using an implemented laboratory prototype. Index Terms--Buck-boost, current source inverters (CSIs), posicast control, pulsewidth modulation (PWM), resonant damping, Z-source inverters.

A new ac equivalent circuit for the CLL voltage-output resonant converter is presented, that offers improved accuracy compared with traditional FMA-based techniques. By employing describing function techniques, the nonlinear interaction of the parallel inductor, rectifier and load is replaced by a complex impedance, thereby facilitating the use of ac equivalent circuit analysis methodologies. Moreover, both continuous and discontinuous rectifier-current operating conditions are addressed. A generic normalized analysis of the converter is also presented. To further aid the designer, error maps are used to demonstrate the boundaries for providing accurate behavioral predictions. A comparison of theoretical results with those from simulation studies and experimental measurements from a prototype converter, are also included as a means of clarifying the benefits of the proposed techniques. Index Terms--DC-DC power conversion, modeling, resonant power conversion.

Nonharmonic acoustic resonance was detected in the static pressure and sound signals in a four-stage high-speed axial compressor when the compressor was operating close to the surge limit. Based on prior research reported in the literature and measurements of the resonance frequency, Mach number of the mean flow, and the axial and circumferential phase shifts of the pressure signal during resonance, it is shown that the acoustic resonance is an axial standing wave of a spinning acoustic mode with three periods around the circumference of the compressor. This phenomenon occurs only if the aerodynamic load in the compressor is high, because the mode needs a high circumferential Mach number for resonance conditions. Mathematics of existing analyses of acoustic resonances in turbomachinery complex and have therefore rarely resulted in published examples of good agreement with real engine data. The present paper provides suitable, physically based simplifications of the existing mathematical models which are applicable for modes with circumferential wavelengths of more than two blade pitches and resonance frequencies considerably higher than the rotor speed. Keywords: axial compressor, acoustic resonance, mode trapping, cut-off frequency, transmission, reflection, rotating stall, rotating instability

In this paper, a novel control strategy for subsynchronous resonance (SSR) mitigation using a static synchronous series compensator (SSSC) will be presented. The SSSC is constituted by three single-phase voltage source converters. SSR mitigation is obtained by increasing the network damping only at those frequencies that are critical for the turbine-generator shaft. This is achieved by controlling the subsynchronous component of the grid current to zero. Using the IEEE First Benchmark Model, the effectiveness of the proposed control algorithm when mitigating SSR due to torsional interaction and torque amplification effect will be shown. Index Terms--Damping controller, series compensation, static synchronous series compensator (SSSC), subsynchronous resonance (SSR), torsional oscillation.

This paper introduces an accurate transformer core model, using the Preisach theory, to represent the core magnetization characteristic. This modeling approach provides the required precision to match major and minor hysteresis loops of the model with those of the actual transformer core material. Using the proposed model, the ferroresonance phenomenon of a voltage transformer (VT) is simulated and compared to the corresponding experimental results. In addition, the simulated ferroresonance behavior of the VT based on: 1) the Electromagnetic Transients Program (EMTP)-RV hysteric reactor model, 2) the EMTP reactor type-96 model, and 3) a single-valued polynomial as magnetization characteristic, is also deduced and compared with the proposed model and the experimental results. The investigations conclude that the proposed model provides the most accurate results in terms of the VT core losses and the VT voltage waveforms and their peak values during 1) normal operating conditions, 2) ferroresonance transients and jumping from normal to ferroresonance operating conditions, and 3) ferroresonance steady-state conditions. Furthermore, higher accuracy of the proposed model in representing the hysteresis loop provides the highest and the most accurate bifurcation point and the transient loss when compared with other models. This paper also concludes that major and minor hysteresis loops must be represented in the core model to accurately simulate ferroresonance phenomenon of the VT. Index Terms--Bifurcation, ferroresonance, hysteresis, minor loops, power loss, Preisach theory, transformer.

The [TE.sub.1 1 1] resonance has been addressed in an asymmetric 'Crawford-style' transverse electromagnetic (TEM) cell using two half-wave slots cut into the septum. Surface currents generated on the septum due to the resonance are at right angles to the TEM cell axis. Appropriately sized resistors placed at the midpoint of the slots load these cross-axial septum currents. The result was a near 20-dB decrease in the total electric field inside the TEM cell at the [TE.sub.1 1 1] resonance frequency. Index Terms--Modeling, resonance, test equipment, transverse electromagnetic (TEM) cell.

An extrapolation technique is presented which reduces the computational demands of obtaining a wideband electromagnetic response from a resonant antenna using traditional computational electromagnetic methods. It has been shown that a wideband response can be extrapolated by fitting early-time and low-frequency data with a summation of orthogonal polynomials. However, representing responses characteristic of resonant structures in practice proves computationally inefficient and can lead to numerical instabilities. This paper outlines the incorporation of damped sinusoids to efficiently, accurately, and reliably extrapolate both time- and frequency-domain responses of resonant antennas due to a wideband source. A genetic algorithm is used to select the necessary extrapolation parameters. The wideband driving-point current response of several resonant antennas is accurately extrapolated. The transmission-line matrix method and the method of moments are used to compute early-time and low-frequency data, respectively. Fundamentally different discretizations of the structure of interest are used, illustrating in principle the independence of the technique and the choice of computational methods used to provide the directly-computed data. Index Terms--Broadband, extrapolation, genetic algorithms, multiresonant antennas, pulse excited antennas.

A study is done to determine the in-plane resonant vibration of angle-ply laminated composites embedded with a piezoceramic layer for different stacking angles using two experimental measurement techniques. Results show that the dynamic characteristics of in-plane resonant vibrations for piezolaminated plates with different stacking angles are very different.

This article deals with a phenomenon named as cavitation resonance. Cavitationassociated pressure fluctuations in hydraulic systems affect their design, operation, and safety. Under certain conditions, the amplitude of a particular component of these fluctuations will be significantly magnified, causing a resonance. Here, the observed phenomenon from three different flow systems is briefly introduced. Based on the coupling of two subsystems, a hypothesis of (macroscopic) mechanism reduced from these experimental observations is presented. [DOI: 10.1115/1.2842149] Keywords: cavitation, resonance, system instability, pressure fluctuations

The dramatic growth of power electronics applications has led to serious harmonic pollutions in the power system. The phenomenon of harmonic resonance resulting in severe voltage distortion has been reported. Various suppression techniques have been proposed to resolve this problem. The distributed active-filter system (DAFS) is a more effective solution by deploying multiple shunt active filter units (AFUs) in the system to cooperatively damp the harmonic resonance. This paper proposes a dynamic tuning scheme for the DAFS to enhance its filtering performance. Based on the measured voltage harmonic distortion at the installation point, each AFU can dynamically adjust its own filtering volt-ampere (VA) capacity to maintain the total harmonic distortion of the line voltage at an allowable level. The proposed strategy can be integrated with the droop control between the conductance command and VA consumption so that the harmonic-filtering workload is evenly shared among various AFUs. The operation principles and dynamic analyses are presented in this paper, and test results based on simulations and experiments validate the proposed approach. Index Terms--Active filters, distributed active-filter systems (DAFSs), harmonic damping, harmonic resonance.

Vibration caused by mechanical resonance and time delay caused by signal detection and transmission degrade the control performance of a servo controller for a multimass mechanical system. A precise numerical model that represents resonance characteristics and time delay is necessary to design a desired control system. This paper presents an identification method using the iterative process of the linearized and weighted total least-squares method. The proposed method derives a transfer function without any prior knowledge of resonance characteristics and time delay. The order of the transfer function is determined with a coefficient diagram that shows coefficients of the denominator of the transfer function. Identification results with an experimental setup are shown to demonstrate the performance of the proposed method. A velocity servo controller with vibration-suppression control is designed with the transfer function, and control performance is verified with the experimental setup to validate the transfer function. Index Terms--Mechanical resonance, multimass mechanical system, system identification, time delay.

A fully integrated balanced amplifier was realized in a standard 0.18-[micro]m CMOS technology. From the measured S-parameters, a gain up to 21.5 dB was achieved at 45.4 GHz under a supply voltage of only 1 V and a total power consumption of 89 mW. An effective technique, i.e., [pi]-type parallel resonance, was proposed to enhance the device and circuit frequency response. In addition, the semicoaxial line structure was used to reduce the signal loss and physical size of the Lange couplers in the amplifier. To the best of the authors' knowledge, the proposed balanced amplifier demonstrated the highest operation frequency and the lowest operation voltage among the published millimeter-wave amplifiers using a similar technology. Index Terms--Balanced amplifier, CMOS, Lange coupler, millimeter wave, parallel resonance, semicoaxial line.

This paper presents a current-fed full-bridge boost dc/ac/dc converter with transformer isolation operating without switching power dissipation. The output voltage is regulated by dc/ac converter control frequency changes with a constant turn-off time of transistors. The proposed converter is devoid of parasitic oscillations, as all of the parasitic capacitances and inductances are included in a resonant tank circuit. In this paper, the system operation is first explained, then a mathematical description that is useful for its design is provided, and finally, a report on the implementation of a laboratory prototype with 1.4-kW power is presented. Index Terms--Bridge, current-fed, dc/ac/dc converter, resonant.

The aim of this contribution is a practice-oriented prediction of environmental building vibrations. A Green's functions method for layered soils is used to build the dynamic stiffness matrix of the soil area that is covered by the foundation. A simple building model is proposed by adding a building mass to the dynamic stiffness of the soil. The vertical soil-building transfer functions with building-soil resonances are calculated and compared with a number of measurements of technically induced vibrations of residential buildings. In a parametrical study, realistic foundation geometries are modeled and the influence of incompressible soil, deep stiff soil layering, soft top layers, and increasing soil stiffness with depth is analyzed. All these special soil models reduce the resonant frequency compared to a standard homogeneous soil. A physically motivated model of a naturally sedimented soil has a stiffness increasing with the square root of the depth and yields a foundation stiffness that decreases with foundation area considerably stronger than the relatively insensitive homogeneous soil. This soil model is suited for the Berlin measuring sites and reproduces satisfactorily the experimental results. DOI: 10.1061/(ASCE)1090-0241(2008)134:3(328) CE Database subject headings: Stiffness; Foundations; Predictions; Resonance; Vibration.

We present a single-stage electronic ballast with a high power factor feature for driving high-intensity discharge (HID) lamps. A new frequency-modulation technique is proposed to eliminate the acoustic resonance problem in HID lamps under high-frequency operation. The proposed method has the merits of simple circuit and low cost; thus, it is suitable for use in commercial applications. The conducted emission caused by the high-frequency electronic ballast can be also effectively reduced. The operating principles and design considerations of the proposed electronic ballast are analyzed and discussed in detail. A 35-W laboratory prototype is designed and implemented. Simulation and experimental waveforms are given to verify the feasibility of the proposed method. The results are satisfactory. Index Terms--Acoustic resonance, frequency-modulation technique, high-intensity discharge (HID) lamp, single-stage electronic ballast.

In this paper, we present a technique to discriminate between two complex bodies with minor structural variations using the high frequency poles as the discriminating feature in the extinction-pulse (E-pulse) scheme. A full scale model of MiG-29 aircraft is considered for discrimination against another with stores (missiles) attached below the wings. The MiG-29 aircraft is impinged with a radar impulse to excite the electrical natural resonance frequencies of the aircraft. These natural resonance frequencies are unique to any aircraft and are used as distinct features for discriminating it against another MiG-29 aircraft with stores. Prony's method is used to extract the natural frequencies from the impulse response of the aircraft.

This paper explores the design and performance of dc-dc power converters operating in the very high frequency (VHF, 30-300 MHz) range. Methods are presented for assessment and comparison of device losses in VHF operation under soft switching and soft gating conditions. These methods are applied to the development of a 2 W resonant boost converter operating at a switching frequency of 30 MHz. Design of the power stage, resonant gate drive, and control circuitry are treated in detail, and experimental results demonstrating the performance of the converter are presented. Index Terms--Class E inverter, multiresonant converter, ON-OFF control, resonant converter, resonant gating, zero-voltage switching.

A high-density transformer using nanocrystalline core is developed for a 30 kW, 200 kHz resonant converter. Loss models are established for nanocrystalline cores through experimental characterization. The important parasitic models are also developed considering litz wire effects. Following a minimum size design procedure, several transformers with both nanocrystalline and ferrite cores are designed and prototyped. While all transformers meet the converter performance requirement during testing, using nanocrystalline core can achieve a significantly higher power density even at 200 kHz. Index Terms--High-frequency transformer design, high power density, nanocrystalline material, resonant converter.

In this paper, the problem of online estimation of subsynchronous frequency components in the measured grid voltage is treated. Two estimation methods, one based on the use of low-pass filters and a recursive least square algorithm, are investigated and compared. In particular, due to its higher degree of freedom in the design, the lowpass filters-based estimation method is found to be the most appropriate and accordingly further analyzed. The method is improved to cope with inaccurate knowledge of the subsynchronous frequency. The simulation results prove the effectiveness of the investigated method both for the ideal and the disturbed case. Index Terms--Filters, frequency-component estimation, recursive least square (RLS), subsynchronous resonance (SSR), torsional oscillations.

This paper proposes a metal halide lamp electronic ballast based on the integration of Zeta and Flyback converters, which are used to achieve power factor correction and lamp current stabilization, respectively. The proposed integrated converter allows to reduce the nmnber of ballast components without increasing the current stress in the shared switch. Thus, the lamp is supplied with a low-frequency square waveform that avoids the acoustic resonance phenomenon. The proposed topology has been implemented and validated by experimental results. Index Terms--Acoustic resonance (AR), ballast, high-intensity discharge (HID) lamps, integrated circnits, power electronics.

The design of a resonant inverter for high-frequency ac (HFAC) power distribution systems is complicated by the following three factors: 1) A number of electronic loads located in different locations are connected to the resonant inverter, the impedance, and the power factor of the equivalent load of which varies over a wider range than a system with a certain load; 2) the resonant inverter is subject to an input-line voltage varying over a wide range; and 3) the characteristics of the resonant inverter depend on the load impedance. It is mandatory to operate the inverter with zero-voltage switching under various load conditions of different power factors and over wide input variations. It is further desirable that multiple resonant inverters can be paralleled with simple current-sharing control (CSC). A phase-shift-modulation (PSM)-controlled full-bridge series-parallel resonant inverter is proposed for the HFAC power distribution architectures. A new PSM method is proposed with which the phase angle of the inverter output voltage is independent of the modulation signal of the phase-shift modulator. Such a feature allows multiple resonant inverters to operate in parallel with a magnitude CSC. The resonant inverter is analyzed with a general nonresistive load model, and the design curves are developed. A prototype resonant inverter system is designed and implemented with an operation frequency of 1 MHz, a rated output power of 150 W, and a sinusoidal output voltage of 1-MHz 28-V rms. The proposed resonant inverter has the advantages of high efficiency over wide input/output line variations, high waveform quality of the output voltage, and phase-angle independence of the voltage-feedback/feed-forward control and CSC. Index Terms--Full bridge, phase-shift modulation (PSM), power distribution architecture, resonant inverter, soft switching.

A high-efficiency two-stage resonant inverter with effective control of both the magnitude and phase angle of the output voltage was proposed in this paper for high-frequency ac (HFAC) power-distribution applications, where a number of resonant inverters need to be paralleled. In order to parallel multiple resonant inverters of the same operation frequency, each inverter module needs independent control of the phase angle and magnitude of the output voltage. It is also desirable that the output voltage has very low total harmonics distortion, as well as high efficiency over wide input and load ranges. The proposed resonant inverter consists of two stages. The first stage is a two-switch dc/dc converter with zero-voltage transition, and the second stage is a half-bridge resonant dc/ac inverter with fixed duty ratio. A series-parallel resonant tank is used to achieve high waveform quality of the output voltage. The magnitude of the output voltage is regulated through the duty-ratio control of the first stage with pulsewidth modulation. The phase angle of the output voltage is regulated through a pulse-phase-modulation control of the second stage. The proposed resonant inverter has the advantages of better waveform quality, wide range of input and load variations for soft-switching, and independent control of the phase angle and magnitude of the output voltage, making it an attractive candidate for applications where a number of resonant inverters need to be placed in parallel to the HFAC bus and a number of distributed loads are connected to the HFAC bus. The performance is verified with both simulation and experiments. Index Terms--High-frequency ac (HFAC), power-distribution architecture, pulse-phase modulation (PPM), pulsewidth modulation (PWM), resonant inverter, zero-voltage switching (ZVS).

Inverters adopted in distributed power generation, active filter, and uninterruptible power supply are often connected to the grid through an inductance--capacitor--inductance (LCL) filter. The impedance of the LCL filter has a typical frequency characteristic with a resonance peak. Hence, the LCL filter has to be damped in order to avoid instability. However, the resonance of the LCL filter can be also excited in a controlled way in order to individuate the resonance frequency in the spectrum (using for example the fast Fourier transform). This paper proposes to use a controlled excitation in measuring the grid impedance, since this one influences also the resonance frequency. This paper will address some possible limits, some solutions, and some implementation issues (e.g., how to obtain a controlled resonance in the filter without damaging the system) in order to use the resonant peak for grid impedance detection. The analysis is validated both by simulations and experimental results. Index Terms--Impedance measurement, power-system parameter estimation, resonance.

This paper describes an automatic computer-controlled acoustic resonance detection workbench for high-intensity-discharge (HID) lamps. The detection method is based on optical measurements of the discharge arc path. With the aid of a dual lens projection system, relative light intensity measurements at different points of the arc are guided by fiber optic to a photodiode array. These measurements are statistically analyzed to identify when acoustic resonance occurs. Experimental results confirm this method to be a valuable tool to automatically obtain an acoustic-resonance-frequency map for HID lamps. Index Terms--Acoustic resonance, high-intensity-discharge (HID) lamp, LabVIEW.

In this paper, the authors present the results of an investigation into the starting process of a small wattage metal halide lamp and address the influence of the starting process, at extra-high frequency (>350 kHz), upon the performance of two most commonly used electronic ballast circuit topologies, namely the LCC resonant inverter and LCL resonant inverter. The starting transient processes driven by both ballast systems are captured, analyzed and explained. It has been found that the starting process could affect the operating performance of an LCL ballast and may destroy its power switches in the worst case while a LCC ballast gets the advantage over the LCL ballast for the stability during the transient starting process. Index Terms--Acoustics resonance, discharge lamps, electronic ballasts.

This paper presents a constant power control circuit for a three-stage high-intensity discharge (HID) electronic ballast. The three-stage electronic ballast is composed of a boost pre-regulator to achieve a high power factor, a DC/DC buck converter to regulate lamp current with constant lamp power, and a full-bridge inverter to drive the HID lamp with a low-frequency ac squarewave current. The buck converter operating in current mode utilizes current sense level-shift technique to achieve constant power output. The proposed constant power control circuit is easily designed and implemented for the three-stage HID electronic ballast. Finally, a laboratory prototype of a 70 W HID electronic ballast is implemented. The measured results show that the proposed ballast can be applied for various HID lamps with low lamp power variation (less than 0.6%). Index Terms--Acoustic resonance, constant power, electronic ballast, HID lamps, low-frequency squarewave.

We investigated grating-coupled transmission-type surface plasmon resonance (SPR) for sensing applications. In the transmission-type SPR structure, propagating surface plasmons are outcoupled to radiation modes by dielectric and metallic gratings on a metal film. The results calculated in air and water suggest that the proposed structures present extremely linear sensing characteristics. In terms of a figure of merit, a metallic grating-based structure performs 5.4 and 3.7 times better than that of a dielectric grating in air and water, respectively. OCIS codes: 050.2770, 230.1950, 240.6680.

A method has been developed to calculate directly resonance frequencies and resonance amplitudes as functions of design parameters or as a function of excitation levels. The method provides, for the first time, this capability for analysis of strongly nonlinear periodic vibrations of bladed disks and other structures with nonlinear interaction at contact interfaces. A criterion for determination of major, sub-, and superharmonic resonance peaks has been formulated. Analytical expressions have been derived for accurate evaluation of the criterion and for tracing resonance regimes as function of such contact interface parameters as gap and interference values, friction and contact stiffness coefficients, and normal stresses. High accuracy and efficiency of the new method have been demonstrated on numerical examples including a large-scale nonlinear bladed disk model and major types of contact interfaces including friction contact interfaces, gaps, and cubic nonlinearities. [DOI: 10.1115/1.2720487]

The effectiveness of buried capacitance technology, used with discrete surface mounted decoupling capacitors, in reducing circuit malfunctions due to the noise voltage between power/ground planes in a multilayer printed circuit board is investigated in this paper. The analysis is carried out on a fully populated multilayer board, where an integrated circuit with very large package provides a lot of digital signals with measured rise/fall times equal to 400 ps. The role of the integrated circuit's package in damping out the resonance peaks at resonance frequencies on the power plane is highlighted. The relations between the power-bus transfer impedance and noise spectrum are also studied, so to better evaluate the effects of the buried capacitance technology and decoupling capacitors on the power-bus noise filtering. Index Terms--ASIC's package, bare PCB, fully populated PCB, powerbus decoupling, power/ground plane resonances, transfer impedance.

A theory is developed to describe low-frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole). The stabilizing effects of a Helmholtz resonator, which models damping through nonlinear effects, are included, together with effects of coupled pressure waves in the fuel supply system. [DOI: 10.1115/1.1370975]

We have built coils with MnZn ferrite cores that demonstrate an appreciable giant magnetoelectric effect (GME). Their maximum magnetoelectric (ME) output is as high as 87 V/[O.sub.e] at tens of kilohertz, which is remarkable for devices without any power supply. Our experimental and theoretical analyses suggest that the GME of the coils originates from LC resonances. Our results show a practical way to design ME devices such as passive high-frequency sensitive magnetic sensors. We have found as well that attention should be paid to LC resonance when performing ME spectral measurements. Index Terms--Ferrite, high-frequency magnetic sensors, LC resonance, magnetoelectric effect.

The magneto-optical Kerr effects in magnetic multilayered structures containing double-negative metamaterials are examined by using 4*4 transfer-matrix method. The studies have shown that large magneto-optical Kerr effects are obtained at very thin magnetic film by using the double-negative metamaterials.

The zero-permittivity metamaterials have provided anomalous tunneling and energy squeezing through ultranarrow waveguide channels and the bending features relative to this counterintuitive resonant effect are examined. The effectively zero permittivity is generated by using a waveguide operating at the cutoff of its dominant mode.

The dependence of the magnetically resonant transmission on the structural parameters is studied. The optimized structure of the double-ring metamaterial is used for exploring the terahertz response with all the sizes scaled down simultaneously.