In this paper, the sensitivity of flexural and torsional vibration modes of a rectangular cantilever immersed in a fluid to surface stiffness variations has been analyzed and a closed-form expression is derived. To represent this sensitivity, we use the analytical formulas for the vibrational resonant frequencies of a rectangular cantilever beam immersed in an inviscid fluid. The effect of the surface contact stiffness on both flexural and torsional sensitivities in a fluid is investigated and compared with the case that cantilever operates in the air. The results show that in the low surface stiffness, the first mode is the most sensitive mode. As the sample surface stiffness is increased, higher resonant frequencies show a larger shift as compared with lower resonant frequencies. In addition, comparison between modal sensitivities in air and fluid shows that the resonance frequency shifts in the air are greater than the resonant frequency shifts in the fluid.

An accurate model named as the Modified Wolff Model (MWM) is presented as an efficient CAD tool for determination of resonant frequency of the dominant and higher order modes under the multi-layer condition in thin and thick circular microstrip patch antennas. The effects of dielectric cover on the resonant frequency obtained from MWM have been compared against the result of theoretical method of Spectral Domain Analysis (SDA). The accuracy of calculated resonant frequency by the MWM for dominant mode is about 0.5% and the average error for higher order modes is about 0.88%. Sensitiveness of higher order modes and also uncertainty effect on the resonant frequency are calculated by the MWM.

Microstrip circular and square structural ring patch antenna because of most plasticity for receiving an transmitting the signals and also application to driver the active devices are used. An accurate modified wolfe model (MWM) is applied to compute the effective dynamic dielectric constant for detremination of resonant frequency microstrip patch antenna circular and square ring without cover. The results obtained from (MWM) have been compared against the result of experimental and other theoretical methods which have very good agreement. Then accuracy of calculated resonant frequency by the (MWM) for dominant mode is about 0.5%. Moreover we calculate the supperstrate effect on the resonant frequency dominant and higher order modes of circular and square ring, but the other methods dose not applicable for calculation of the supperstrate effects on the resonant frequency.

In this paper, a new method is developed to detect and track the resonance frequency of ultrasonic transducers. In order to have an acceptable performance of transducers, power supplies should be able to detect and track the resonance frequency. Different methods have been used for this purpose. In this research, the voltage of the transducer and the phase difference between the voltage and current are used to find the resonant frequency. The maximum voltage of a transducer is founded in a predefined frequency interval. Afterward, the minimum phase difference between the voltage and current is obtained in a smaller interval around it. The simultaneous use of the voltage and phase shift increases the accuracy and speed of the algorithm. Since the transducer's voltage variations are relatively large near the resonant frequency, it is a versatile parameter compared to the current used in other methods to indicate the resonance frequency. The algorithm is implemented within a microcontroller. An FPGA is used to generate accurate frequency using the Direct Digital Synthesis (DDS) method. The algorithm can detect the resonant frequency under free conditions. Applying force to transducers or emerging the transducer's head to the water changes the resonant frequency. The experimental tests showed that the algorithm could find and track the resonant frequency automatically under loading conditions.

An analysis of resonant modes in ladder networks is performed using di erence equations. Linear and loop con gurations are studied and analytical relations are derived for the mode distributions and resonant frequencies of these networks, having arbitrary elements. Furthermore, it is shown that a) Modes with an exponential distribution along network nodes may exist in some cases and b) The mode distributions in loop networks are independent of network elements. Finally, a simple criterion is obtained for a loop structure to control the spacing between resonant frequencies.

In this paper, the effect of temperature on electrical impedance, resonant frequency and antiresonance of a plural acoustic piezoelectric transducer has been investigated. These effects are being studied in the design of electronic circuits connected to the high-power Tonpillos projector that is used to clean oil pipelines using acoustic waves. A special oil storage tank, converter, heating equipment and control were designed and constructed. Two sensitive thermometers, oil temperature and converter are accurately measured. The impedance behavior was performed in the temperature range of 20-120 ° C and in the frequency range 18-25 kHz. The results show that with increasing temperature, the frequency of the resonance is 480 Hz and the antiresonance of 400 Hz is decreased. Changes in the magnitude of the impedance increase of 43 ohms in the resonant frequency and a decrease of 965 ohms at the antiresonance frequency. The results of the experiments show that impedance, resonant frequency and antiresonance are strongly dependent on temperature. This could be considered for future research on increasing the acoustic efficiency of high-capacity converters in cleaning systems, especially in oil pipelines.

The electric field in cavity accelerates charged particles and magnetic field of magnets changes the direction of these particles in cyclotrons. In order to establish the electric field inside the cavity, a noiseless radio frequency (RF) signal should be generated, amplified and sent to cavity. The resonant frequency of the cavity could be changed by temperature variation. Variation of resonant frequency will cause reflected power from the cavity. in this work the low level RF circuits with task of signal generation, phase and frequency Adjustment, cavity resonant frequency Adjustment, protection of the RF set from the reflected power and stability of RF system was designed.

In this article, the sensitivity and resonant frequency of the atomic force microscope made of functionally graded materials is investigated by couple stress theory (MCST). In MCST, the size effect of the system is taking into account by means of the material length scale parameter. is made of a mixture of metal and ceramic with properties varying through the thickness following a simple In this work, due to the kinematic energy and potential energy of , the governing equations of motion and corresponding boundary conditions are derived on the basis of Hamilton principle by considering Euler-Bernoulli beam theory. Based on the results, it is clear that when the contact stiffness increases, the sensitivity of the system decreases, and resonant frequency increases. Moreover, when the thickness comes approximately close to material length scale parameter, the difference between MCST and classical continuum mechanic becomes significant. Furthermore, in low contact stiffness, increasing the power reduces the sensitivity of , while in high contact stiffness, increasing the power  increases the sensitivity of the system. Results also show that at each value of contact stiffness, as ceramic volume fraction increases the resonant frequency will be increased, too.

Considering the challenges in fabrication and electromagnetic characterization of linear accelerator tube, first four major effective parameters in cavity fabrication, including cavity material, dimension agreement, surface roughness and concentricity of cavities have been studied. Then, considering appropriate electromagnetic properties, fabrication results of cavities, techniques for their resonant frequency and quality factor measurement are presented. Then, plunger test is done by designing special fixtures for double checking the resonant frequency of each cavity. Finally, the bead-pull test is accomplished after brazing the cavities together, to check the RF field profile and tuning.

The most important quality indicator of fruits is the flesh firmness which is well correlated to their young’s modulus. In this research variation of vibration characteristics (shape modes, natural frequency) of apple due to change of material characteristics (density, young's models, Poisson ratio) and apple volume was investigated using Finite Element simulation. An image processing technique was used to obtain an unsymmetrical and non-spherical geometric model of apple. The exact three-dimensional shape of the fruit was created by determining the coordinates of apple surface and forming uneven rotational curvatures. Modal analysis with no boundary constraints has been applied. The first 20 Eigen frequencies and the corresponding mode shape were determined. Six rigid body modes possess zero resonant frequency which is related to the degree of freedom of a rigid body in space indicated the validity of finite element model. The modal analysis results showed that resonant frequency increased by increasing young's modulus of the fruit, while it decreased by increasing apple density. First mode torsion has a mean resonant frequency of 584 Hz. Variations of natural frequency due to change in young's modulus, density, and Poisson ratio were 80%, 11% and 4%, respectively. Coefficient of variation of resonant frequency in response to changing young's modulus was 2-3 times of that of density which shows the greatest effect of young modulus changes on natural frequency of fruits. Consequently with determination of fruit's natural frequency, their young modulus and firmness can be estimated.