Showing papers on "Frequency response published in 2010"
TL;DR: In this paper, a distributed vibration sensor was developed by using heterodyne detection and signal processing of moving averaging and moving differential for the phase optical time domain reflectometry system for detecting pencil break vibration.
Abstract: We developed a distributed vibration sensor by using heterodyne detection and signal processing of moving averaging and moving differential for the phase optical time domain reflectometry system. The broadband acoustic frequency components generated by pencil-break vibration have been measured and identified in location by our distributed vibration sensor for the first time. Pencil break measurement is a standard technique to emulate the acoustic emission of cracks in concrete or steel bridges for early crack identification. The spatial resolution is 5m and the highest frequency response is 1 kHz, which is limited by the trigger frequency of data acquisition card. This new sensing system can be used for vibration detection of health monitoring of various civil structures as well as any dynamic monitoring requirement.
576 citations
TL;DR: In this paper, a nonlinear electromagnetic energy harvesting device with a broadly resonant response was presented, which is generated by a particular arrangement of magnets in conjunction with an iron-cored stator.
Abstract: In this paper, we present a nonlinear electromagnetic energy harvesting device that has a broadly resonant response. The nonlinearity is generated by a particular arrangement of magnets in conjunction with an iron-cored stator. We show the resonant response of the system to both pure-tone excitation and narrow-band random excitation. In addition to the primary resonance, the superharmonic resonances of the harvester are also investigated and we show that the corresponding mechanical upconversion of the excitation frequency may be useful for energy harvesting. The harvester is modeled using a Duffing-type equation and the results are compared with the experimental data.
324 citations
TL;DR: In this paper, a laser and sunlight driven, fast and large oscillation of cantilevers composed of photoresponsive liquid crystal polymer materials was reported. But the experimental frequency response is accurately described by the calculated natural resonant frequency for a non-damped cantilever.
Abstract: We report on the laser and sunlight driven, fast and large oscillation of cantilevers composed of photoresponsive liquid crystal polymer materials. The oscillation frequency, driven with a focused 100 mW laser of multiple wavelengths (457, 488, 514 nm), is as high as 270 Hz and is shown to be strongly correlated to the physical dimensions of the cantilever. The experimental frequency response is accurately described by the calculated natural resonant frequency for a non-damped cantilever. To further understand the conversion efficiency of light energy to mechanical work in the system, the oscillatory behavior of a 2.7 mm × 0.7 mm × 0.04 mm cantilever was examined at pressures ranging from 1 atm to 0.03 atm. A large increase in amplitude from 110° at STP to 250° at low pressure was observed. A first approximation of the system efficiency was calculated at 0.1%. The large increase in amplitude at low pressure indicates strong hydrodynamic loss and thus, the material efficiency is potentially much greater. Using a simple optical setup, oscillatory behavior was also demonstrated using sunlight. This work indicates the potential for remotely triggered photoactuation of photoresponsive polymer cantilevers from long distances with lasers or focused sunlight.
278 citations
TL;DR: In this paper, the relationship between the total stored turbine kinetic energy and the total system power production for wind is studied in detail using simplified frequency control models and extensive simulations of wind penetration scenarios over an extended multi-year timeframe.
Abstract: Rising wind generation penetrations and the distinctive inertial characteristics of associated turbine technology will impact system frequency control. While wind production will displace conventional synchronous plant, empirical study data presented also suggest that the relationship between the total stored turbine kinetic energy and the total system power production for wind is a variable that exhibits significant nonlinearity. Changing trends in system frequency behavior of a power system following the loss of the largest generator are studied in detail here, using simplified frequency control models and extensive simulations of wind penetration scenarios over an extended multiyear timeframe. The system frequency response is characterized by the rate of change of frequency and the frequency nadir. Results show that increasing levels of doubly fed induction generators and high-voltage dc interconnection alter the frequency behavior significantly, and that system operators may have to be proactive in developing solutions to meet these challenges.
265 citations
TL;DR: In this paper, the authors present a comprehensive synthesis procedure for designing low profile, band-pass frequency selective surfaces composed of non-resonant constituting elements, which can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave.
Abstract: We present a comprehensive synthesis procedure for designing low-profile, band-pass frequency selective surfaces composed of non-resonant constituting elements. The proposed FSSs use arrays of sub-wavelength periodic structures with non-resonant constituting unit cells with unit cell dimensions and periodicities in the range of , where is the free space wavelength. The main advantages of this type of FSS, compared to traditional ones, are that they allow for the design of low-profile and ultra-thin FSSs that can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave. An order FSS designed using this technique typically has an electrical thickness in the order of which is significantly smaller than the overall thickness of a traditionally designed order FSS . The proposed synthesis procedure is validated for two FSS prototypes having third- and fourth-order band-pass responses. Principles of operation, detailed synthesis procedure, measurement results of a fabricated prototype, and implementation guidelines for this type of FSS are presented and discussed in this paper.
232 citations
TL;DR: In this article, the authors propose and experimentally validate a first-principles based model for the nonlinear piezoelectric response of an electroelastic energy harvester.
Abstract: We propose and experimentally validate a first-principles based model for the nonlinear piezoelectric response of an electroelastic energy harvester The analysis herein highlights the importance of modeling inherent piezoelectric nonlinearities that are not limited to higher order elastic effects but also include nonlinear coupling to a power harvesting circuit Furthermore, a nonlinear damping mechanism is shown to accurately restrict the amplitude and bandwidth of the frequency response The linear piezoelectric modeling framework widely accepted for theoretical investigations is demonstrated to be a weak presumption for near-resonant excitation amplitudes as low as 05 g in a prefabricated bimorph whose oscillation amplitudes remain geometrically linear for the full range of experimental tests performed (never exceeding 025% of the cantilever overhang length) Nonlinear coefficients are identified via a nonlinear least-squares optimization algorithm that utilizes an approximate analytic solution obta
228 citations
TL;DR: Estimates of the dynamic phasor and its derivatives are obtained through the weighted least squares solution of a Taylor approximation using classical windows as weighting factors, which leads to differentiators with ideal frequency response around the fundamental frequency.
Abstract: Estimates of the dynamic phasor and its derivatives are obtained through the weighted least squares solution of a Taylor approximation using classical windows as weighting factors. This solution leads to differentiators with ideal frequency response around the fundamental frequency and to very low sidelobe level over the stopband, which implies low noise sensitivity. The differentiators are maximally flat in the interval centered at the fundamental frequency and have a linear phase response. Therefore, their estimates are free of amplitude and phase distortion and are obtained at once. No further patch is needed to improve their accuracy. Examples of dynamic phasor estimates are illustrated under transient conditions. Special emphasis is put on frequency measurements.
202 citations
TL;DR: A detailed comparison with the classical spectral analysis based on correlation techniques shows that the proposed procedures are more robust than those of Schoukens et al.
181 citations
TL;DR: This paper proposes a new approach which is based on a system-theoretic tool, the Loewner matrix pencil constructed in the context of tangential interpolation, which is fast, accurate, they build low order models and are especially designed for a large number of terminals.
Abstract: This paper addresses the problem of modeling systems from measurements of their frequency response. For multiport devices, currently available techniques are expensive. We propose a new approach which is based on a system-theoretic tool, the Loewner matrix pencil constructed in the context of tangential interpolation. Several implementations are presented. They are fast, accurate, they build low order models and are especially designed for a large number of terminals. Moreover, they identify the underlying system, rather than merely fitting the measurements. The numerical results show that our algorithms yield smaller models in less time, when compared to vector fitting.
167 citations
TL;DR: In this paper, the authors proposed a decentralized power system stabilizer for interconnected multi-machine power systems based on the information available at the high voltage bus of the step-up transformer and a modified Heffron-Phillips model.
Abstract: This paper proposes a method of designing fixed parameter decentralized power system stabilizers (PSS) for interconnected multi-machine power systems. Conventional design technique using a single machine infinite bus approximation involves the frequency response estimation called the GEP(s) between the AVR input and the resultant electrical torque. This requires the knowledge of equivalent external reactance and infinite bus voltage or their estimated values at each machine. Other design techniques using P-Vr characteristics or residues are based on complete system information. In the proposed method, information available at the high voltage bus of the step-up transformer is used to set up a modified Heffron-Phillip's model. With this model it is possible to decide the structure of the PSS compensator and tune its parameters at each machine in the multi-machine environment, using only those signals that are available at the generating station. The efficacy of the proposed design technique has been evaluated on three of the most widely used test systems. The simulation results have shown that the performance of the proposed stabilizer is comparable to that which could be obtained by conventional design but without the need for the estimation and computation of external system parameters.
161 citations
25 Jul 2010
TL;DR: In this paper, three different control concepts that enable wind turbines to participate on grid frequency control are introduced, including pitch control together with the provision of reserve capacity by operating the wind turbine in part load mode.
Abstract: The speed of modern converter controlled wind turbines is almost completely decoupled from the grid frequency. Accordingly, wind turbines do not possess a natural response to frequency excursions. In this paper three different control concepts that enable wind turbines to participate on grid frequency control are introduced. The first uses pitch control together with the provision of reserve capacity by operating the wind turbine in part load mode. The second and third strategies utilize the kinetic energy of wind turbines to provide frequency support for a limited time following a disturbance. One involves a control scheme which initiates the partial release of the kinetic energy immediately after the frequency drop is detected. Replenishing the stored energy and thus accelerating the wind turbine then follows during the frequency recovery phase. The third option calls for the wind turbine to accelerate first, and then decelerate by discharging energy during the phase of the disturbance in which the frequency is approaching its minimum, thus limiting the frequency drop more effectively. For all three concepts the control structures are presented, and the effectiveness of the suggested methods is demonstrated using simulation results.
TL;DR: Recommendations on desirable microphone characteristics, while preliminary and in need of further numerical justification, should provide the basis for better accuracy and repeatability of studies on voice and speech production in the future.
Abstract: Purpose This tutorial addresses fundamental characteristics of microphones (frequency response, frequency range, dynamic range, and directionality), which are important for accurate measurements of voice and speech. Method Technical and voice literature was reviewed and analyzed. The following recommendations on desirable microphone characteristics were formulated: The frequency response of microphones should be flat (i.e., variation of less than 2 dB) within the frequency range between the lowest expected fundamental frequency of voice and the highest spectral component of interest. The equivalent noise level of the microphones is recommended to be at least 15 dB lower than the sound level of the softest phonations. The upper limit of the dynamic range of the microphone should be above the sound level of the loudest phonations. Directional microphones should be placed at the distance that corresponds to their maximally flat frequency response, to avoid the proximity effect; otherwise, they will be unsuit...
TL;DR: In this paper, a high-performance top-gate graphene field effect transistor (G-FET) is fabricated and used for constructing a high efficient frequency doubler, taking the advantages of the high gate efficiency and low parasitic capacitance of the top gate device geometry.
Abstract: A high-performance top-gate graphene field-effect transistor (G-FET) is fabricated, and used for constructing a high efficient frequency doubler. Taking the advantages of the high gate efficiency and low parasitic capacitance of the top-gate device geometry, the gain of the graphene frequency doubler is increased about ten times compared to that of the back-gate G-FET based device. The frequency response of the frequency doubler is also pushed from 10 kHz for a back-gate device to 200 kHz, at which most of the output power is concentrated at the doubled fundamental frequency of 400 kHz.
TL;DR: In this article, a frequency selective surface (FSS) that is electronically switchable between reflective and transparent states is tested, which can be used to provide a spatial filter solution to reconfigure the electromagnetic architecture of buildings.
Abstract: A frequency selective surface (FSS) that is electronically switchable between reflective and transparent states is tested. It can be used to provide a spatial filter solution to reconfigure the electromagnetic architecture of buildings. The FSS measurements show that the frequency response of the filter does not change significantly when the wave polarization changes or the angle of incidence changes up to ±45° from normal. The FSS is based on square loop aperture geometry, with each unit cell having four PIN diodes across the aperture at 90 degree intervals. Experiments demonstrated that almost 10 dB additional transmission loss can be introduced on average at the resonance frequency, for both polarizations, by switching PIN diodes to on from off state.
TL;DR: In this paper, a full-order small-signal modeling and dynamic analysis of zero-voltage-switching (ZVS) phase-shift bidirectional DC-DC converters is studied.
Abstract: Full-order small-signal modelling and dynamic analysis of zero-voltage-switching (ZVS) phase-shift bidirectional DC-DC converters is studied. A general modelling method is proposed to develop the discrete-time average model. This full-order model takes into account the leakage inductance current and the resonant transition intervals in order to realise ZVS. Both the leakage inductance current and the resonant transition intervals are the key to accurately predict the dynamic behaviour of the converter. A control-to-output-voltage transfer function is derived for the dual active bridge DC-DC converter, which is taken as an example to illustrate the modelling procedure. Experimental results confirm that the new model correctly predicts the small-signal frequency response up to one-third of the switching frequency and is more accurate than the previously presented models.
01 Jan 2010
TL;DR: In this paper, a two-pole filter with an internal volume of 1.5 cm and an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, is presented.
Abstract: This paper presents a miniature high- tunable evanescent-mode cavity filter using planar capacitive RF micro- electromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm , results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ulti- mate rejection of 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured of the filter is 300-500 over the tuning range, which is the best reported using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.
TL;DR: In this paper, double-sided parallelstrip line (DSPSL) was used to build a novel differential filter with ultra- wideband (UWB) response, and swap structures, based on DSPSL, are employed in the design to realize 180° phase shift.
Abstract: In this letter, double-sided parallel-strip line (DSPSL) has been used to build a novel differential filter with ultra- wideband (UWB) response. Swap structures, based on DSPSL, are employed in the design to realize 180° phase shift. So the swap structures can realize the conversion between differential- and common-mode. Utilizing the characteristic, the input common- mode signals will be cancelled at the center of the filter, while the input differential-mode signals can propagate in the proposed filter. The proposed new differential filter was calculated in analytical method, and was simulated by the full-wave electromagnetic simulator, and was validated by the measurement. The last results show they have a good in-band and out-band performance. With fractional bandwidth of 110% centered at 3 GHz, the differential-mode signals can propagate with UWB frequency response, while the common-mode signals are suppressed below -20 dB in the whole frequency band.
TL;DR: In this paper, a two-pole filter with an internal volume of 1.5 cm3 and an insertion loss of 4.91-3.18-and 1-dB bandwidth of 17.8-41.1 MHz, respectively, is presented.
Abstract: This paper presents a miniature high-Q tunable evanescent-mode cavity filter using planar capacitive RF microelectromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm3, results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ultimate rejection of > 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured Qu of the filter is 300-500 over the tuning range, which is the best reported Q using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.
TL;DR: In this article, a dual-band frequency selective surface (FSS) with closely spaced bands of operation and a highly selective frequency response at each band is presented, which is attributed to the extremely small overall thickness of the structure as well as its small unit cell dimensions.
Abstract: We present a new design of a dual-band frequency selective surface (FSS) with closely spaced bands of operation and a highly-selective frequency response at each band. A multi-stage design procedure is also proposed for the design and synthesis of this class of frequency selective surfaces. The design procedure is based on synthesizing the desired device from its equivalent circuit parameter values. An approximate analytical technique is provided, which can be used to determine the values of the equivalent circuit parameters of this dual-band device from the basic system level characteristics of its transfer function including the center frequencies of operations of its two bands of operation and the bandwidth at each of these bands. The use of this design procedure is described in detail by a design example which follows the proposed design procedure step by step; the validity of the procedure is verified using full-wave EM simulations and experimental characterization of a fabricated prototype of the proposed device. Experimental characterizations of this device show that it has a stable frequency response as a function of angle of incidence for both the transverse electric (TE) and the transverse magnetic (TM) polarizations. This stability is attributed to the extremely small overall thickness of the structure as well as its small unit cell dimensions.
Patent•
16 Sep 2010
TL;DR: In this paper, an ultrasonic system consisting of an elongated member and a resonator was provided to impart ultrasonic energy to tissue and a generator to supply power to the resonator of the ultrasonic device.
Abstract: An ultrasonic system is provided that includes an ultrasonic device having an elongated member configured to impart ultrasonic energy to tissue and a resonator configured to impart a frequency to the elongated member. The system also includes an ultrasonic generator configured to supply power to the resonator of the ultrasonic device. The ultrasonic generator has a drive signal generator configured to provide a drive signal, a noise signal generator configure to provide a noise signal, and a controller. The controller receives an output signal from the ultrasonic device and the noise signal from the noise signal generator, calculates a transfer function based on the output signal and the noise signal, and adjusts the drive signal generator based on the calculated transfer function.
TL;DR: A new adaptive algorithm for situations where the plant is unknown and may be time-varying is presented, which consists in obtaining online estimates of the plant frequency response and of the disturbance parameters and which can be divided into stable and unstable subsets.
Abstract: The rejection of periodic disturbances is a problem frequently encountered in control engineering, and in active noise and vibration control in particular. The paper presents a new adaptive algorithm for situations where the plant is unknown and may be time-varying. The approach consists in obtaining online estimates of the plant frequency response and of the disturbance parameters. The estimates are used to continuously update control parameters and cancel or minimize the effect of the disturbance. The dynamic behavior of the algorithm is analyzed using averaging theory. Averaging theory is used to approximate the nonlinear time-varying closed-loop system by a nonlinear time-invariant system. It is shown that the four-dimensional averaged system has a two-dimensional equilibrium surface, which can be divided into stable and unstable subsets. Trajectories generally converge to a stable point of the equilibrium surface, implying that the disturbance is asymptotically canceled even if the true parameters of the system are not exactly determined. Simulations, as well as extensive experiments on an active noise control testbed, illustrate the results of the analysis and demonstrate the ability of the algorithm to recover from abrupt system changes or track slowly-varying parameters. Extensions of the algorithm to systems with multiple inputs/outputs and disturbances consisting of multiple frequency components are provided.
26 Jul 2010
TL;DR: A method for real-time sound propagation that captures all wave effects, including diffraction and reverberation, for multiple moving sources and a moving listener in a complex, static 3D scene and applies a novel technique to extract and compactly encode the perceptually salient information in the resulting acoustic responses.
Abstract: We present a method for real-time sound propagation that captures all wave effects, including diffraction and reverberation, for multiple moving sources and a moving listener in a complex, static 3D scene. It performs an offline numerical simulation over the scene and then applies a novel technique to extract and compactly encode the perceptually salient information in the resulting acoustic responses. Each response is automatically broken into two phases: early reflections (ER) and late reverberation (LR), via a threshold on the temporal density of arriving wavefronts. The LR is simulated and stored in the frequency domain, once per room in the scene. The ER accounts for more detailed spatial variation, by recording a set of peak delays/amplitudes in the time domain and a residual frequency response sampled in octave frequency bands, at each source/receiver point pair in a 5D grid. An efficient run-time uses this precomputed representation to perform binaural sound rendering based on frequency-domain convolution. Our system demonstrates realistic, wave-based acoustic effects in real time, including diffraction low-passing behind obstructions, sound focusing, hollow reverberation in empty rooms, sound diffusion in fully-furnished rooms, and realistic late reverberation.
TL;DR: In this paper, the nonlinearity of the attachment is derived from a geometric configuration consisting of a mass suspended on two springs which are adjusted to achieve a quasi-zero stiffness characteristic with pure cubic non-linearity.
TL;DR: Stability of the string is characterized by a dc gain condition that can be expressed as a continued fraction with verifiable convergence properties and the derived results are applied to locally decentralized control of large vehicle platoons.
Abstract: For a string of (possibly arbitrarily many) coupled stable subsystems that are equipped with a dynamic property of negative imaginary frequency response, we characterize stability of the string by a dc gain condition that can be expressed as a continued fraction with verifiable convergence properties. Through analysis of the convergence of the continued fraction, we establish stability results for the string with various coupling gains and patterns. The derived results are applied to locally decentralized control of large vehicle platoons, possibly with heterogenous neighboring coupling.
TL;DR: In this paper, a finite element code is developed for structural response analysis of the free and forced vibration of a sandwich beam with composite faces and viscoelastic core, where independent transverse displacements on two faces and linear variations through the depth of the beam core are considered.
TL;DR: In this article, a modified beam theory is presented by incorporating surface elasticity and the Galerkin method is used to give a reduced-order model of the problem and numerical results show that the mechanical buckling and free vibration phenomena of nanobeams are size-dependence.
Abstract: A modified continuum model of the nanoscale beams is presented by incorporating surface elasticity in this paper. The classical beam theory is adopted to model the bulk, while the bulk stresses along the surfaces of the bulk substrate are required to satisfy the surface balance equations of the continuum surface elasticity. On the basis of this modified beam theory the governing equation of the nanobeam is derived where the effect of the geometry nonlinearity is also considered. The Galerkin method is used to give a reduced-order model of the problem. Beams made from two materials: aluminum and silicon are chosen as examples. The numerical results show that the mechanical buckling and free vibration phenomena of nanobeams are size-dependence. The effects of the surface energies on the critical axial force of buckling, post-buckling and linear free vibration frequency are discussed. Finally, the amplitude frequency response is given numerically through the incremental harmonic balanced method.
TL;DR: In this paper, a new technique for designing tunable frequency selective surfaces (FSSs) with the second-order band-pass response is presented and experimentally verified, which is applied to an FSS utilizing nonresonant, subwavelength, constituting unit cells.
Abstract: In this letter, a new technique for designing tunable frequency selective surfaces (FSSs) with the second-order band-pass response is presented and experimentally verified. The technique is applied to an FSS utilizing nonresonant, subwavelength, constituting unit cells. Frequency tuning is achieved by adjusting the location of a liquid metal slug within capillary tubes embedded between the FSS's metallic layers. A wideband flexible frequency tuning covering nearly the entire X band is tested in a waveguide environment and excellent agreement between the measured and simulated results is demonstrated.
TL;DR: In this article, the dynamics of trapping coupled with charge transfer is analyzed in the frequency domain for a model of the dye-sensitized solar cell, and the steady state occupations of the surface state and the resulting recombination currents are solved based on the assumption of detailed balance.
TL;DR: It is shown that the proposed method can be used for nonlinear systems and for parametric identification of the system dynamics in a generalized output error framework and illustrated on simulations and real measurements examples.
01 Jan 2010
TL;DR: The response on a broadband signal is measured, resulting in a multisine SSFR test, which allows swift evaluation of the influence of frequency, saturation, and cross saturation on the q-and d-axis parameters with a signal generator that is often already available to control the machine.
Abstract: With the standstill frequency-response (SSFR) test, accurate electrical-machine models can be identified. However, it can be a time-consuming method, particularly in case the machine has to be identified at low frequencies. To shorten the required time for identification, in this paper, the response on a broadband signal is measured, resulting in a multisine SSFR test. To generate the broadband signal, a high-power linear amplifier can be applied as a waveform generator. As this signal generator is not commonly available in the field, the application of a voltage-source inverter (VSI) is discussed. The multisine SSFR test with a VSI allows swift evaluation of the influence of frequency, saturation, and cross saturation on the q-and d-axis parameters with a signal generator that is often already available to control the machine. Extensive measurements are performed on several permanent-magnet synchronous machines and the method can be extended to synchronous machines with rotor-field winding. By applying a switching converter instead of a linear amplifier, it can be expected that the identification results are affected by the switching actions. Therefore, multisine SSFR tests with either a VSI or a high-power linear amplifier as well as conventional tests as described in the IEEE standard are performed, and the results are compared.