Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Vibration of geometrically imperfect panels subjected to thermal and mechanical loads

Abstract: The results of a study of the vibration response of transversely isotropic flat and curved panels subjected to temperature fields and to mechanical loads into the postbuckling load range are presented. The results were obtained using a higher-order transverse-shear-deformation theory of shallow shells that includes the effects of geometric nonlinearities and initial geometric imperfections. The results focus on the interaction between the temperature field, the applied mechanical load, and the fundamental frequency associated with small vibrations about the prebuckling and postbuckling equilibrium states. Results are presented for a wide range of temperatures and mechanical load magnitudes and of geometric parameters. The results show that transverse-shear flexibility has a significant effect on the analytical prediction of panel response and that the fundamental frequency of a panel may be substantially overestimated in the prebuckling load range and underestimated in the postbuckling load range. Results are also presented that indicate that the fundamental frequency of flat panels generally increases as the initial geometric imperfection amplitude increases for both the prebuckling and postbuckling load ranges. The results, however, also indicate that the fundamental frequency of curved panels generally decreases in the prebuckling load range and increases in the postbuckling load ranges.

Speech transformations based on a sinusoidal representation

Abstract: This paper presents a new speech analysis/synthesis technique based on a sinusoidal representation of the speech production mechanism but which is independent of pitch and the voiced/unvoiced speech state. The resulting synthetic speech preserves the waveform shape and is essentially perceptually indistinguishable from the original. The method provides the basis for a general class of speech transformations and is successfully applied to time-scale modification, frequency scaling, and scaling of pitch. Furthermore, these modifications can be performed with a time-varying rate of change, allowing, for example, continuous adjustment of a speaker's fundamental frequency and rate of articulation. Although the analysis/synthesis system was originally designed for single-speaker signals, it is equally capable of recovering and modifying nonspeech signals such as music, multi-speakers, marine biologic sounds, and speech in the presence of interferences such as noise and musical backgrounds.

The Artificial Bee Colony algorithm in layer optimization for the maximum fundamental frequency of symmetrical laminated composite plates

Abstract: In this study the layer optimization was carried out for maximizing the lowest (first) fundamental frequency of symmetrical laminated composite plates subjected to any combination of the three classical boundary conditions, and the applicability of the Artificial Bee Colony (ABC) algorithm to the layer optimization was investigated. The finite element method was used for calculating the first natural frequencies of the laminated composite plates with various stacking sequences. The ABC algorithm maximizes the first natural frequency of the laminated composite plate defined as an objective function. The optimal stacking sequences were determined for two layer numbers, twenty boundary conditions and two plate length/width ratios. The outer layers of the composite plate had a stiffness increasing effect, and as the number of clamped plate edges was increased both he stiffness and natural frequency of the plate increased. The optimal stacking sequences were in good agreement with those determined by the Ritz-...

Novel oscillator incorporating a compact microstrip resonant cell

Abstract: A novel transistor oscillator incorporating a compact microstrip resonant cell (CMRC) as its terminating resonance is proposed. Adjusting the dimensions of the cell, it is possible that the fundamental frequency can be positively fed back and the second harmonic negatively fed back at the input port of the oscillator. The fundamental output is enhanced with the second harmonic being suppressed. The output power of the proposed CMRC oscillator is 14.7 dBm at 2.5 GHz with 27.1 dB rejection of the second harmonic, outperforming the conventional microstrip termination with a 40% size reduction.