Longitudinal vibration of piano strings greatly contributes to the distinctive character of low piano notes. In this paper a simplified modal model is developed, which describes the generation of phantom partials and longitudinal free modes jointly. The model is based on the simplification that the coupling from the transverse vibration to the longitudinal polarization is unidirectional. The modal formulation makes it possible to predict the prominent components of longitudinal vibration as a function of transverse modal frequencies. This provides a qualitative insight into the generation of longitudinal vibration, while the model is still capable of explaining the empirical results of earlier works. The semi-quantitative agreement with measurement results implies that the main source of phantom partials is the transverse to longitudinal coupling, while the string termination and the longitudinal to transverse coupling have only small influence. The results suggest that the longitudinal component of the tone can be treated as a quasi-harmonic spectrum with formantlike peaks at the longitudinal modal frequencies. The model is further simplified and applied for the real-time synthesis of piano sound with convincing sonic results.
The effect of irradiance during low temperature hardening was studied in a winter wheat variety. Ten-day-old winter wheat plants were cold-hardened at 5 ∞C for 11 days under light (250 μmol m Ð2 s Ð1 ) or dark (20 μmol m Ð2 s Ð1 ) conditions. The effectiveness of hardening was significantly lower in the dark, in spite of a slight decrease in the F v /F m chlorophyll fluorescence induction parameter, indicating the occurrence of photoinhibition during the hardening period in the light. Hardening in the light caused a downshift in the far-red induced AG (afterglow) thermoluminescence band. The faster dark re-reduction of P700 + , monitored by 820-nm absorbance, could also be observed in these plants. These results suggest that the induction of cyclic photosynthetic electron flow may also contribute to the advantage of frost hardening under light conditions in wheat plants.
This paper presents a new nonlinear least-squares algorithm for fitting band-limited periodic signals with unknown frequency and harmonic content. The new solution features a model-based recursive calculation method that requires less memory space and has smaller computational demand than the known matrix-based algorithms.
AbstraeC A noq"ebic i&nti&&n method for linear system is proposed The i & n t i m n is done v i a synchronized mdtisine measurements whem the sywhronidon is ensured by a resonator based generator-o b server p i x The advantuge of the pposed sftucture is that it works as a fiuer lwtR andpvkies the measrement results omfine. Exponemi2 avemging is an option of the me#wdandPrequin?s 110 extm c o l c~i z s. A further advmrfqge is that the & n t i. n m be done over anyjkquenq set wiulout any loss of Mornmnce. Explicit fonruJas m given for noise sl(ppresSi0nandseluingtime. ThemethodisUwbutedbyapmchlem Pk?.
Section 11. recalls the identification problem and the resonator based observer. Section In. introduces the resonator based identification and a detailed analysis is given. Real measurement data are provided in section IV., while section V. is the conlusion.
PRELIMINARIES I. INTRODUCTIONFourier analysis is a well-known method for non-parametric frequency domain identification of linear systems [l]. IFrequency domain data are often inputs for parametric identification [2]. The utilization of multisine excitation provides the possibility of the elimination of the systematic errors like leakage and picket fence [3]. In most cases the output of the system is analyzed by the discrete Fourier transform (DFT), while the frequency domain parameters of the excitation are known in advance. The DFT is calculated via the fast Fourier transform (FFT). In order to suppress the measurement noise, averaging on the analysis results is also necessary.Resonator based observers were developed earlier to perform the recursive discrete Fourier transform (RDFT) [41, [5]. In these observers the resonators work in a common feedback loop providing zero steady-state feedback error at the resonator frequencies. The summed output of such resonators can generate any periodic signal up to the half of the sampling frequency. It is straightforward to utilize such a generator -observer pair for frequency domain non-parametric system identification: the system to be identified has to be in between the generator and the observer and the ratio of the state variables of the observer and the generator supplies the estimated transfer function. This arangement can be an alternative of the ITTbased analysis since it works as a filter bank and provides the measurement results on-line.
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