Effect Of Excitation Frequency Research Articles

Review on flow separation control: effects of excitation frequency and momentum coefficient

This paper presents a comprehensive review of the studies and research conducted on flow separation control on lifting surfaces. In this paper, two critical parameters, namely, the momentum coefficient and excitation frequency, that significantly impact flow separation control are analyzed in detail. Through a comprehensive literature review, experimental and numerical studies are examined in order to gain insight into the underlying mechanisms of momentum injection and excitation frequency on the shear layer and wake dynamics and to quantify the impact of these parameters on the flow separation control. Effective flow control on lifting surfaces can modify the streamlines and pressure distribution, thereby increasing their aerodynamic efficiency. This paper focuses on the control of flow separation on airfoils, with particular attention paid to the benefits of such control, including lift enhancement, drag reduction, aerodynamic efficiency enhancement, performance enhancement, and other important features. This paper presents a review of studies that have employed blowing actuators, as well as zero net mass flux, plasma, and acoustic actuators, in order to provide an appropriate historical context for recent developments. The findings of this review paper will contribute to a better understanding of the optimal conditions for efficient flow separation control on lifting surfaces using unsteady excitation, which can have significant implications for improving the performance and efficiency of various aerodynamic applications. This paper aims to elucidate and emphasize the positive and negative aspects of existing research, while also suggesting new interesting areas for future investigation.

Modelling the effect of excitation frequency on the shape of hysteresis loop in permalloy

Modelling the effect of excitation frequency on the shape of hysteresis loop in permalloy

Formation of cell spheroids using Standing Surface Acoustic Wave (SSAW).

3D bioprinting becomes one of the popular approaches in the tissue engineering. In this emerging application, bioink is crucial for fabrication and functionality of constructed tissue. The use of cell spheroids as bioink can enhance the cell-cell interaction and subsequently the growth and differentiation of cells in the 3D printed construct with the minimum amount of other biomaterials. However, the conventional methods of preparing the cell spheroids have several limitations, such as long culture time, low-throughput, and medium modification. In this study, the formation of cell spheroids by SSAW was evaluated both numerically and experimentally in order to overcome the aforementioned limitations. The effects of excitation frequencies on the cell accumulation time, diameter of the formed cell spheroids, and subsequently, the growth and viability of cell spheroids in the culture medium over time were studied. Using the high-frequency (23.8 MHz) excitation, cell accumulation time to the pressure nodes could be reduced in comparison to that of the low-frequency (10.4 MHz) excitation, but in a smaller spheroid size. SSAW excitation at both frequencies does not affect the cell viability up to 7 days, > 90% with no statistical difference compared with the control group. In summary, SSAW can effectively prepare the cell spheroids as bioink for the future 3D bioprinting and various biotechnology applications (e.g., pharmaceutical drug screening and tissue engineering).

Crack monitoring in concrete beams under bending using ultrasonic waves and coda wave interferometry: the effect of excitation frequency on coda

Crack monitoring in concrete beams under bending using ultrasonic waves and coda wave interferometry: the effect of excitation frequency on coda

桑葚机械振动收获参数优化与试验研究

The mechanized harvesting of mulberry is important for its production. In the process of harvesting, it is considered not only the mechanical damage of mulberry fruit but also its harvesting efficiency. It is very important to improve the vibration harvesting efficiency of mulberry. In this study, modal analysis of mulberry trees and harmonic response analysis of branches were carried out to determine the harvesting frequency of the branch's vibration and other parameters. The effects of excitation frequency and vibration position on the triaxial acceleration of the mulberry branch at different positions were analyzed by vibration test. Then the triaxial acceleration of branches at different positions was analyzed. The conditions of the mulberry fruit shedding were obtained through theoretical analysis. Through the 20-order modal analysis of mulberry, it is concluded that a better vibration effect can be achieved when the vibration frequency is controlled at 4-16 Hz. According to the harmonic response analysis, the best excitation frequencies are 5-6 Hz, 10-13 Hz, and 14-16 Hz. The harmonic response analysis of fruit branches was carried out, and the stress of fruit stalks at 5 Hz, 10 Hz, and 15 Hz were analyzed. The result shows that the maximum stress is 2.9252×107 Pa, the excitation position is the first-order branch, and the excitation frequency is 15 Hz. The frequencies obtained from modal analysis and harmonious response analysis were used to conduct experiments. When the excitation frequency was 15 Hz, the triaxial accelerations aX, aY, and aZ were 2.12 g, 4.16 g, and 3.99 g, respectively, which were more conducive to the shedding of mulberry fruits.

Improving the performance of nonlinear isolator through triboelectric nanogenerator damper integrating energy harvesting

In order to solve the problem of integration of low-frequency vibration isolation and vibration energy harvesting, this paper proposes a novel nonlinear oscillator with triboelectric nanogenerator damper (NO-TENGD), which can realize different nonlinear characteristics of quasi-zero stiffness (QZS) and bistable by changing the length of rigid links. The mechanism of improving the isolation performance of NO-TENGD was analyzed and discussed with a dynamic model proposed, and the effects of excitation frequency, friction force, geometric parameters, and spring stiffness were studied. The damping can be increased by adjusting the pressure of TENGD, which can effectively suppress the resonance peak value of response amplitude and force transmissibility. The experimental results show that when the excitation frequency is larger, the amplitude response of NO-TENGD is smaller under frictionless condition, and the amplitude response of NO-TENGD under large friction condition is smaller than that under small friction one. NO-TENGD with QZS has a good vibration isolation effect, and the output power can light up 50 LED lights or electronic watches. Finally, NO-TENGD with QZS can achieve low frequency vibration suppression, and increasing damping can reduce the response amplitude and force transmissibility of the beam bridge in the resonance frequency range.

Nondestructive testing method for internal defects in ferromagnetic materials under weak bias magnetization

Magnetic flux leakage (MFL) testing is effective in detecting internal defects in ferromagnetic materials. However, it requires the saturation magnetization of materials, which is not always practicable in complex inspection environments. Therefore, this study presents a novel dynamic permeability testing (DPT) method, in which internal defects will induce dynamic permeability variations on the surface of weakly magnetized ferromagnetic materials, and the variations are then detected by alternating current detection coils with magnetic cores, enabling the identification of internal defects. The principle of DPT is analyzed through simulations, which are subsequently verified by experiments. Furthermore, the effects of excitation frequency, probe lift-off, and defect size on the DPT signal are investigated experimentally. Finally, the comparison with conventional MFL demonstrates that the DPT method can effectively identify the internal defect using a weak magnetization current of 0.1 A (about 0.25 T in the steel plate), whereas MFL requires 0.5 A (about 1.32 T) to achieve a similar detection capability under the same probe lift-off values. This new method has significant practical value, especially in situations where saturation magnetization is not feasible.

Influence of Cold Plasma Processing on the Stability of Phenolic Compounds of Araça-Boi (Eugenia stipitata) Juice

Knowledge of the chemical changes caused during plasma treatment is essential to enhance food quality. In this work, the influence of two cold plasma technologies, dielectric barrier discharge plasma and glow discharge plasma, on the phenolic profile of araça-boi (Eugenia stipitata) juice was investigated and assessed by gas chromatography coupled to mass spectrometry. Eight phenolic compounds were identified in araça-boi, with cinnamic acid being the major phenolic compound of the fruit juice, followed by protocatechuic acid. The effects of excitation frequency and plasma flow rate were evaluated because these are the main operating conditions that can be set for plasma treatments. The phenolic profile slightly changed due to the reaction of the phenolics with the reactive plasma species produced during the treatment, with the highest increase in phenolic content observed in the dielectric barrier discharge plasma operating at 1000 Hz. Both plasma systems increased the bioavailability of phenolic compounds in the juice, which could be increased by up to 201% using the dielectric barrier discharge plasma. Plasma application increased the concentration of cinnamic, hydrocinnamic, benzoic, and p-coumaric acids. Overall, plasma treatment improved the bioavailability of the phenolic compounds and resulted in slight changes to the phenolic profile of araça-boi juice. Thus, the technology showed a positive effect on araça-boi juice. This work advanced our further understanding of the changes induced by cold plasma treatment on phenolic compounds and characterization of araça-boi (Eugenia stipatata).

Effect of excitation frequency and joint density on the dynamic amplification effect of slope surface on jointed rock slopes

This paper presents the slope dynamic response of jointed rock slopes containing three groups of typical joints and analyzes the effect of input harmonic frequency and joint density on the peak horizontal acceleration (PGA) of the slope surface under vertically impinging SV wave (shear vertical wave) excitation. First, the dynamic response of the slope surface of the bedding slope was investigated with a large-scale shaking table test, and the reliability of the numerical model was verified by the physical modeling. Then, a series of jointed rock slope models with different joint densities were established based on the three-dimensional discrete element software 3DEC. It is found that the natural frequency fn of the jointed slope decreases with the increase of joint density. The effect of excitation frequency f on the slope surface dynamic response of the jointed slope is stronger than that of joint density. The closer the f is to the fn, the stronger the slope surface and slope crest dynamic response is. Notably, taking fn as the critical value of f, the slope surface dynamic amplification mode of jointed slope can be divided into two types: when f ≤ fn, the acceleration amplification factor of X-direction (AAF-X) of the slope surface amplifies monotonically with increasing elevation; when f >fn, the AAF-X of the slope surface shows a fluctuated amplification pattern with the increase of elevation. The results of this paper show that in the seismic design of slope engineering, the influence of site conditions on the frequency spectrum characteristics of ground motion should be considered, and then the optimal design should be carried out.

Effect of excitation frequencies on phase contrast in tapping mode atomic force microscope

There are several imaging modes in AFM, and the tapping mode is the most commonly used scanning mode. Tapping mode can acquire the height information and phase information of the sample surface, among which the phase information has more value, which can reflect the physical properties of the sample surface. In order to understand the phase imaging mechanism of AFM, this paper uses the vibration theory to derive the theoretical expression of phase, and finds that the excitation frequency will directly affect the phase contrast. Based on this, this paper finds, through theoretical and experimental analysis, that there exists an optimal excitation frequency that maximizes the phase contrast during the scanning process. These results are important for interpreting the phase image of AFM and thus optimizing the phase imaging in experiments.

Vibration investigation of conical dielectric elastomer thin membrane for energy harvesting system

The dielectric elastomer (DE) has promising application prospects in many fields such as biomedicine, human-machine interface, soft robots, and energy harvesting. In present study, the conical energy harvesting structure is investigated and the DE is viewed as the hyperelastic neo-Hookean model. Considering the rotation and the tension of the DE membrane, the dynamic model of the conical DE thin membrane, i.e. mass-spring system is established based on the Euler-Lagrange method. The experiment is carried out to validate the output voltage of the conical thin membrane. The effects of excitation frequency, geometry size of the conical DE membrane, stiffness of the spring, pre-stretching on the resonance frequency, displacement amplitude and failed region are fully studied. The results demonstrate that the geometric size of the conical DE membrane greatly affects the resonance frequency and the amplitude. The principal resonance frequency of the quasi pointed conical DE structure is greater than the frustum conical DE structure, and the principal frequency of the quasi cylindrical conical DE structure is the lowest. The experiment result fits very well with the theoretical result for the output voltage. These findings can provide beneficial guidance for the design of the energy harvesting structures of high efficiency.

Effect of excitation frequency on dissipation behavior of vibrated granular balls.

The dissipation behavior of granular balls in a quasi-2D vertically oscillating closed container is studied by the discrete element method with varying excitation frequencies in this work. Combining the dynamic behavior with dissipation effect of vibrated granular balls, the optimal damping effect of the phase transition critical stage between granular density inversion and granular Leidenfrost effect that involves four high damping granular phases (HDGPs) is revealed. Moreover, the high damping granular phases near and away from this phase transition critical stage are compared and analyzed further, which indicates the universal dynamic behavior of dense granular clusters playing the optimal damping effect. Finally, the optimal damping mechanism of granular balls in the quasi-2D closed container is clarified. Damping properties and motion states of partic.

Effect of excitation vibration on mechanical property and stress corrosion resistance of cast steel

Cast steel parts can realize rapid prototyping effectively, which is suitable for complex structural design. However, due to the large residual stress, the problem of mechanical property degradation is more obvious. In order to solve this problem, a high temperature excitation vibration treatment scheme is proposed in this paper. By applying different excitation frequencies and impact forces, the effects of mechanical properties and stress corrosion properties are studied and verified. Based on the finite element software ANSYS, the modal shape and resonant frequency of the cast steel parts are obtained, and verified by the sweep frequency module in the excitation vibration system. According to the characteristics of modal shape, five typical detection paths are set, and stress sensors are arranged every 200 mm. In order to obtain the specific effects of excitation frequency and impact force amplitude on mechanical properties, nine parts samples were prepared on the same production line according to the matching requirements of test parameters. In addition, the main external parameters that remain unchanged during vibration excitation are set as initial 750 ℃ and vibration excitation time of 60 s, which can fully affect the effect of austenite transformation. Keeping the synchronization of test parameters in different samples, the distribution rules of residual stress under different excitation frequencies and forces are obtained and analyzed. In the aspect of mechanical properties, the microstructure, hardness, yield strength and tensile strength of the specimens subjected to vibration were compared and analyzed. In the aspect of stress corrosion performance research, stress corrosion cracking test was carried out in weak acid environment to obtain the tensile stress curve and fracture morphology of the specimen. The results show that the excitation vibration at high temperature can effectively eliminate the residual stress of cast steel parts, but the increase of excitation frequency does not correspond to the effect of residual stress elimination. When the exciting force exceeds a certain value, the stress relief effect cannot be further improved. Excitation vibration can reduce the internal hardness of cast steel parts to a certain extent, and improve the yield strength and tensile strength. At the same time, it has a positive role in promoting the improvement of stress corrosion resistance.

Influence of atmospheric and vacuum plasma processing on the organic composition of araça-boi (Eugenia stipitata) juice

Cold plasma is a novel non-thermal technology that is still under development. Cold plasma treatment of food products induces a wide range of chemical changes in food compounds, several of which can improve nutritional quality. Understanding the chemical changes caused during plasma treatment is essential to enhance food quality and avoid the formation of undesired compounds. This investigation addressed the influence of two cold plasma technologies, glow discharge plasma and dielectric barrier discharge plasma, on the organic composition of araça-boi (Eugenia stipitata) juice, which is rich in sugars, organic and amino acids. The chemical composition of the juice was assessed by 1H nuclear magnetic resonance coupled with chemometrics. The effects of excitation frequency, processing time, and plasma flow rate were investigated. Glow discharge plasma and dielectric barrier discharge plasma application tended to decrease the concentration of glucose (33%), fructose (31%), malic acid (25%), and amino acids while increasing sucrose content (23%). Overall, plasma processing changed the juices’ alcohol, sugar, and amino acids content, primarily by reducing the concentration of cysteine (33%), alanine (42%), and methionine (43%). However, the dielectric barrier discharge plasma tended to slightly increase the amino acid content (up to 9%) when operating at 200 Hz.

Excitation Frequency Effect on Breast Cancer Cell Death by Atmospheric Pressure Cold Plasma

Excitation Frequency Effect on Breast Cancer Cell Death by Atmospheric Pressure Cold Plasma

Experimental investigation of Magneto-rheological damper

In recent years, intensive research works are concentrated on the development of semi-active control devices. A semi-active control system can also be explained as a system that mainly requires a small external power source for functioning and applies the motion of the structure to generate the control forces. A semi-active control system typically begins from a passive control system, which is followed by a change to permit the flexibility of mechanical properties. The mechanical properties of the semi-active control devices may be modified depending upon the response from the excitation and/or from the calculated reaction. Magneto-rheological (MR) dampers are a type of a semi-active control device that, in the presence of Magneto-rheological (MR) fluid, responds to the applied vibrations. This type of damper has copper winding in it, forming an electronic circuit internally with a combination of MR fluids. The effectiveness of MR damper greatly depends on the command voltage to the copper winding. In the present study, the response of MR Damper to the command voltage, and the excitation frequency is experimentally evaluated. MR damper is supported by a wall mounting rigid fixture and connected to a shake table by a fixing unit. The voltage is varied from 0 V - 10 V with an interval of 2 V. Command voltages is applied to the MR damper with the help of voltage regulator and digital multi meter. The effect of excitation frequency is also studied (1 Hz – 8 Hz). While conducting the experimental work, acceleration values are obtained through the Data acquisition system. These acceleration values are integrated to get the velocity and displacement response. The relation between the displacement, velocity, acceleration of the MR damper, and the frequency of shake table and command voltage is studied. From the experimental work, it is observed that the displacement response of the damper is effectively controlled by increasing the command voltage.

Modulation of the Physicochemical Properties of Aria (Goeppertia allouia) Starch by Cold Plasma: Effect of Excitation Frequency

Modulation of the Physicochemical Properties of Aria (Goeppertia allouia) Starch by Cold Plasma: Effect of Excitation Frequency

Defect Detection inside a Rail Head by Ultrasonic Guided Waves

Early detection of defects inside a rail is of great significance to ensure the safety of rail transit. This work investigated the ability of ultrasonic guided waves (UGWs) to detect internal defects in a rail head. First, the model of UGW propagation in rail, which has an irregular cross-section, was constructed based on the semi-analytical finite element (SAFE) method. Fundamental characteristics, such as wavenumber, phase or group velocity, and wave structure inside the rail, were then calculated. Following modal and vibration energy distribution analysis, a guided wave mode that is sensitive to transverse fissure (TF) defects was selected, and its excitation method was proposed. The effectiveness of the excitation method was confirmed by simulations performed in the ABAQUS software. According to the simulation data, the dispersion curve calculated by using the two-dimensional Fourier fast transform (2D-FFT) coincided well with that of the SAFE method. After that, the sensitivity of the selected mode to internal rail defects was validated and its ability to locate defects was also demonstrated. Finally, the effects of excitation frequency, defect size, and vertical and horizontal defect depth on the reflection waveforms were investigated.

Characterization of drilling damage in glass laminate composites using lock-in thermography nondestructive evaluation method: a feasibility study

ABSTRACT The drilling of composite structure leads to its damage, near the peripheral areas of the drilled hole, due to the laminar structure of the composites. The goodness of a drilling process can be evaluated by measuring the extent of the damage caused by it. In the present study, lock-in thermography non-destructive inspection method is proposed to characterise the drilling damages in glass fiber–reinforced polymer panel. A semi-automated image processing methodology is proposed to calculate damage parameters, namely delamination area and size, and delamination factor. The effect of excitation frequency on the damage characterisation is studied to decide the optimum frequency range to measure the damage parameters through signal-to-noise ratio and damage visibility. The damage parameters are measured at optimum frequency. The study showed that the lock-in thermography technique has the potential to characterise drilling damage.

Dipteran flight-inspired bistable triboelectric nanogenerator for harvesting low frequency vibration

Triboelectric nanogenerator (TENG) is a new type of self-powered equipment which can collect vibration energy in the environment. However, using traditional linear float technology is difficult to achieve the low frequency vibration energy harvesting of broadband. In order to solve the problem of the bandwidth limitation the output of TENG, dipteran flight-inspired bistable triboelectric nanogenerator (DFIB-TENG) was proposed in this paper, which was inspired by the flying mechanism of the double wing. The effects of excitation frequency, amplitude and the link length on the energy harvesting of the DFIB-TENG are studied. The results show that the DFIB-TENG has high output in the wide range of 3–7 Hz. The DFIB-TENG has the maximum energy output in the excitation frequency of 6 Hz, the excitation amplitude is 40 mm and the link length is 65.0 mm. The short circuit current of the DFIB-TENG is 12.17 μA, and the output voltage is 1108 V, the output power is 1.25 mW. The DFIB-TENG can drive 50 led lights or feed the electronic watch when working. The dynamic model of the DFIB-TENG was established by the Euler-Lagrange equation, and the dynamic response was analyzed by numerical analysis. The numerical simulation results are consistent with the experimental results, and the correctness of the completion results is verified. The DFIB-TENG can be used to harvest low frequency bridge vibration energy, providing electricity for its health monitoring and sensing network.