Showing papers in "Journal of Low Frequency Noise Vibration and Active Control in 2022"
TL;DR: The pull-in voltage is crucial in designing an optimal nano/micro-electromechanical system (N/MEMS) as discussed by the authors , and it is vital to have a simple formulation to calculate the pullin voltage with relatively high accuracy; two simple and effective methods are suggested for this purpose; one is an ancient Chinese algorithm and the other is an extension of He's frequency formulation.
Abstract: The pull-in voltage is crucial in designing an optimal nano/micro-electromechanical system (N/MEMS). It is vital to have a simple formulation to calculate the pull-in voltage with relatively high accuracy. Two simple and effective methods are suggested for this purpose; one is an ancient Chinese algorithm and the other is an extension of He’s frequency formulation.
20 citations
TL;DR: In this article , a comprehensive formularization of the frequency-amplitude formula is presented to cover higher powers of the restoring force which are not limited to cubic powers, and three equivalent styles of the generalized frequency amplitude have been performed.
Abstract: The comprehensive formularization of the frequency–amplitude formula is the main interest in this work to cover higher powers of the restoring force which are not limited to cubic powers. Three equivalent styles of the generalized frequency amplitude have been performed. In addition, the restoring force is not restricted to an odd function in which the non-secular forces are included. Three forms of the non-secular forces have been formulated for the first time and treated as non-homogenous of the linearized Duffing oscillator. The modified style of He’s formula has been applied to the singular oscillator using the enhanced potential function. The simplicity of the present approach provides extra advantages for high nonlinearity vibration. This method enriches the analysis with more details in new dimensions.
17 citations
TL;DR: In this paper , the authors proposed a fractal optimal control of a system governed by fractal variational principle to deal with unsmooth boundaries, which has obvious advantages in low differentiability for an unsmoot boundary problem.
Abstract: The optimal control of a system governed by an elliptic equation has been widely applied in engineering, and it requires twice differentiability. Furthermore, the optimal control cannot effectively deal with unsmooth boundaries. Now, the condition will not be maintained for a long time because this paper suggests a fractal optimal control of a system governed by a fractal variational principle to deal with unsmooth boundaries. The new optimal theory has obvious advantages in low differentiability for an unsmooth boundary problem. The air conditioning in a room is used as an example to show how to maintain maximum comfortableness of the workplace and maximum efficiency of energy saving.
12 citations
TL;DR: In this article , a modified Kadomtsev-Petviashvili (mKP) equation is derived by employing the weak turbulence theory for studying the characteristics of the nonlinear dust-acoustic waves (DAWs) in the model under consideration.
Abstract: Motivated by the observations of Voyager 1 and 2 spacecraft and Freja satellite observations in Saturn’s magnetosphere, the formation of dust-acoustic (DA) localized and periodic waves in a complex plasma having superthermal electrons and ions are reported. In this regard, a modified Kadomtsev–Petviashvili (mKP) equation is derived by employing the weak turbulence theory for studying the characteristics of the nonlinear dust-acoustic waves (DAWs) in the model under consideration. The localized and periodic wave solutions to the mKP equation are derived using ansatz method in terms of Jacobi elliptic functions (JEFs). It is reported that the phase velocity of the DAWs in the Saturn’s magnetosphere is lower for kappa distributed ions and electrons by comparison with regions of space plasmas where the electrons and ions follow the Maxwellian distribution. The conditions for the existence of both localized and periodic waves are also presented. Estimates are also given of the spatial scales over which the dust-acoustic solitary/periodic structures form in Saturn’s magnetosphere.
12 citations
TL;DR: In this article , the authors proposed an underwater acoustic structure, which can improve and obtain low-frequency and broadband sound absorption performance by embedding local resonators into functionally graded materials (FGMs).
Abstract: The underwater anechoic coating with local resonant units is an effective method to achieve low-frequency sound absorption. However, the structure obtained in this way is not satisfactory in the sound absorption effect of mid-high frequency bands. Capitalizing on the impedance gradient characteristics of functionally graded materials (FGMs) can improve the impedance matching between the structure and the medium, and enhance the dissipation of sound waves inside the structure. Based on these, we propose an underwater acoustic structure, which can improve and obtain low-frequency and broadband sound absorption performance by embedding local resonators into FGMs. To reveal the sound-absorbing mechanism and further optimize the low-frequency absorption performance of the structure, we conduct quantitative analyses on the parameters of FGMs, the materials and forms of resonators. The results indicate that by appropriately adjusting the studied parameters, different low-frequency sound-absorbing peak can be obtained and the absorption effects are also further improved.
10 citations
TL;DR: In this article , a novel approach has been introduced to facilitate the analysis of the oscillation having fractional-order derivatives and to obtain the analytical solution easily, where the similitude between the analytical and numerical solution verifies and gives satisfactory precision to the equivalent solution.
Abstract: The existence of the derivative with a fractional-order in a class of differential equations could lead to complicating the analysis. In this paper, a novel approach has been introduced to facilitate the analysis of the oscillation having fractional-order derivatives and to obtain the analytical solution easily. The present technique is formulated to provide an easy way of understanding. The suggested technique has been utilized to study two examples for illustration. The similitude between the analytical and numerical solution verifies and gives satisfactory precision to the equivalent solution. The new technique is represented to be the best tool for solving the nonlinear oscillation problems in physics and engineering which have a fractional-order.
10 citations
TL;DR: In this paper , the Khater II analytical technique is used to examine novel soliton structures for the fractional nonlinear third-order Schrödinger (3-FNLS) problem.
Abstract: In this paper, the Khater II analytical technique is used to examine novel soliton structures for the fractional nonlinear third-order Schrödinger (3-FNLS) problem. The 3-FNLS equation explains the dynamical behavior of a system’s quantum aspects and ultra-short optical fiber pulses. Additionally, it determines the wave function of a quantum mechanical system in which atomic particles behave similarly to waves. For example, electrons, like light waves, exhibit diffraction patterns when passing through a double slit. As a result, it was fair to suppose that a wave equation could adequately describe atomic particle behavior. The correctness of the solutions is determined by comparing the analytical answers obtained with the numerical solutions and determining the absolute error. The trigonometric Quintic B-spline numerical (TQBS) technique is used based on the computed required criteria. Analytical and numerical solutions are represented in a variety of graphs. The strength and efficacy of the approaches used are evaluated.
10 citations
TL;DR: In this article , the coupling damping effect of a parallel-connected viscous mass damper (PVMD) and a grounded cross-tie on a single stay cable is investigated.
Abstract: Recent studies have shown that the combination of external dampers and cross-ties can overcome their respective deficiencies while retaining their respective merits. Inspired by the advantages of a viscous damper (VD) and a cross-tie on a single stay cable, the coupled damping effect of a parallel-connected viscous mass damper (PVMD) and a grounded cross-tie on a single stay cable is investigated in this paper. The complex wave number equations of the cable–PVMD–cross-tie system are first formulated through the complex modal analysis. Subsequently, the asymptotic and iterative complex wave numbers are compared to evaluate the applicability of the asymptotic and iterative solutions. Furthermore, parametric studies are carried out to investigate the effects of the stiffness coefficients and the installation positions of the cross-tie on the first supplemental modal damping ratio and frequency of the cable. Finally, the installation positions of the cross-tie are optimized to achieve the optimal vibration control of the cable with the PVMD and the cross-tie.
6 citations
TL;DR: In this paper , the authors investigated the computational complex wave solutions of the modified Korteweg-de-Vries equation combined with an adverse order of the Korthe-de Vries model.
Abstract: This article investigates the computational complex wave solutions of the modified Korteweg–de Vries equation combined with an adverse order of the Korteweg–de Vries model. This model was derived in 2017, where the recursion and inverse recursion operators are employed to select the integrable merged MKdV with a negative MKdV model. This integrable property is tested utilizing the Painlevé property. Verosky gave the description and properties of the opposing order recursion operator. We handle this model by implementing eleven contemporary techniques. We obtain a novel formula of complex solitary wave solutions for this model. Complex solitary wave solutions describe wave propagation, and it is also considered more mathematically concise tools to explain more details about the physical properties of models. The main goals of our paper are a comparison between these methods and introducing a novel modified method. All solutions are checked for accuracy by putting them back into the model via two different software (Maple 17 and Mathematica 12).
6 citations
TL;DR: In this article , a non-perturbative linearization approach is proposed to obtain a quasi-exact solution of the non-conservative coupled nonlinear forced oscillators in the presence of periodic forces.
Abstract: The current article is concerned with a comprehensive investigation of achieving the simplest solution of non-conservative coupled nonlinear forced oscillators. The article mainly depends on a non-perturbative method. It depends on yielding an equivalent linear system. The advantage of this linear system is that its coefficients are easily computed and that they include the effects of the original nonlinear coefficients. This linearization approach allows achieving quasi-exact solutions even in the presence of periodic forces. The relationships of frequencies with amplitudes are easily established. The analytical solution so yielded may serve as a basis for a qualitative understanding of the actual behavior of the coupled nonlinear oscillators. Additionally, numerical calculations are carried out graphically to address the validation of the new approach and to further illustrate the effectiveness and convenience of the method. The results are compared with the exact numerical solutions which show perfect accuracy. The method can be easily extended to other nonlinear systems and can therefore be exceedingly applicable in engineering and other sciences.
4 citations
TL;DR: In this paper , an alternative modification of He's frequency formulation was proposed by dividing the oscillators into two extreme conditions when the amplitude is either extremely small or remarkably large, and a final frequency formulation is obtained by matching the two extremes.
Abstract: Recently Shen suggested a modification of He’s frequency formulation using Lagrange interpolation with great success for the cubic-quintic Duffing oscillator. This paper proposed an alternative modification of He’s frequency formulation by dividing the oscillators into two extreme conditions when the amplitude is either extremely small or remarkably large, and He’s frequency formulation is used for each case, and a final frequency formulation is obtained by matching the two extreme conditions. Comparison of the approximate frequency with the exact one for various amplitudes shows good agreement.
TL;DR: In this article , the authors investigated the nonlinear Chiral Schrödinger equation (CNLSE) in two dimensions where noise term affected randomly with time, and the presented solutions are periodic envelopes, explosive, dissipative, symmetric solitons, and blow up waves.
Abstract: In this paper, we investigate the nonlinear Chiral Schrödinger equation (CNLSE) in two dimensions where noise term affected randomly with time. This equation characterized some edges states of fractional-Hall Effect features in quantum. The CNLSE with multiplicative noise effects is studied as dynamical system to specify the acceptable solution types and then solved by unified solver method. The presented solutions are periodic envelopes, explosive, dissipative, symmetric solitons, and blow up waves. It was confirmed that the noise factor is dominant on all the wave conversion, growing and damping of envelopes and shocks. The presented technique in this study can be easily utilized for other nonlinear equations in applied science. Mathematics Subject Classification (2010): 35C08, 65C20, 60H15, 35Q40, 35Q55, 35Q62
TL;DR: In this article , a strongly nonlinear oscillator with cubic and harmonic restoring force is considered and a Taylor approximation is provided using the global residue harmonic balance method (GRHBM) without any discretization or restrict assumptions.
Abstract: Abstract This paper focuses on the numerical investigation of a strongly nonlinear oscillator with cubic and harmonic restoring force. We transform this oscillator as a free damped cubic-quintic Duffing oscillator equation by Taylor approximation. The approximated solutions with high accuracy are provided by using the global residue harmonic balance method (GRHBM) without any discretization or restrict assumptions. The sensitive analysis of the approximation or the frequency with respect to the amplitude is considered in detail. Numerical comparisons with Runge–Kutta method and harmonic balance method are given to show the efficiency and stability of GRHBM.
TL;DR: In this article , the authors applied the unified solver method in order to extract some new stochastic solutions for three types of NLSEs forced by multiplicative noise in Itô sense.
Abstract: The nonlinear Schrödinger’s equations (NLSEs) is a famous model used to investigate the propagation of optical solitons via nonlinear optical fibers. We applied the unified solver method in order to extract some new stochastic solutions for three types of NLSEs forced by multiplicative noise in Itô sense. The acquired solutions describe the propagation of solitons in nonlinear optical fibers. We exhibit the influence of presence of noise term on the solution for the NLSEs. The theoretical analysis and presented solutions illustrate that the proposed solver is powerful and efficient. Finally, the wave amplitudes may be controlled by the effects performance of physical parameters of the NLSEs in the presence of noise term in Itô sense. Finally, we present He’s frequency formulation.
TL;DR: In this paper , a general algebraic method is proposed for finding some solutions of a conformable fractional coupled nonlinear Schrödinger equation with variable coefficients arising in inhomogeneous fibers with two orthogonal polarization states.
Abstract: In this work, the general algebraic method is proposed for finding some solutions of a conformable fractional coupled nonlinear Schrödinger equation with variable coefficients arising in inhomogeneous fibers with two orthogonal polarization states. With the aid of symbolic computations, many types of new soliton pulse and periodic pulse solutions including complex doubly periodic solutions, solitary wave solutions, and trigonometric function solutions are obtained. Some 3D and 2D numerical simulations about these solutions are portraited, which show the novelty and visibility of the dynamical structure and propagation behavior of the corresponding model. Moreover, we found the W-shaped soliton pulse and the periodic wave pulse can be effectively controlled by changing the relative parameters of the frequency coefficients and orders, which will help us to have a better understanding about the internal structure of this model.
TL;DR: In this article , the authors presented the first treatment to obtain the solution of a complex Helmholtz-Duffing oscillator, which described the elevation of the surface waves in fluid mechanics.
Abstract: The current paper presents the first treatment to obtain the solution of a complex Helmholtz–Duffing oscillator. This model has described the elevation of the surface waves in fluid mechanics. The non-perturbative approach is used to convert the nonlinear oscillator to a linear oscillator to derive the solution of the complex nonlinear oscillator. This paper has opened the path for a new way to study more complex nonlinear elevation of surface waves.
TL;DR: In this paper , the authors studied the idempotents on multiplicative semigroups of tropical matrices under multiplication and gave a simple optimization where the constraint is given by the tropical algebra.
Abstract: Algorithms for noise removal are either complex or ineffective, and the optimal control with inequality constrains makes the algorithm even more complex. Now the condition is changed completely, and the tropical algebra is an extremely simple tool for this purpose. The tropical algebra-based filter has obvious advantages over traditional ones, and an inequality constrain can be converted to a tropical polynomial, making the tropical algebra much attractive in engineering applications. In this paper, idempotents on multiplicative semigroups of tropical matrices are studied. First, the concepts of tropical algebra and the semigroup of tropical matrices under multiplication are introduced. Second, the structure of idempotents on the semigroup of 3 × 3 tropical matrices under multiplication is given. Finally, as examples, the tropical addition is used as a filter for noise removal, and a simple optimization is given where the constraint is given by the tropical algebra. The paper has opened the path for a new way to noise removal and optimization.
TL;DR: In this article , a marine pump is experimentally measured under normal condition and shaft combined misalignment condition, and the frequency domain characteristics of vibration and noise are analyzed by Fast Fourier transform technique.
Abstract: Shaft combined misalignment is the main form of shaft misalignment fault in a marine centrifugal pump. To investigate the influence of shaft misalignment on the vibration and noise of marine centrifugal pumps, a marine pump is experimentally measured under normal condition and shaft combined misalignment condition. In this paper, the frequency domain characteristics of vibration and noise are analyzed by Fast Fourier transform technique. The characteristics of axis orbit, the spectral characteristics of vibration and noise, and the One-Third octave spectral distribution characteristics are also comprehensively compared. Results show that after shaft combined misalignment occurs, the maximum amplitudes of 1APF (axial passing frequency) in the X and Y directions at M1 increase by 35.06% and 24.04%, the maximum amplitudes of 2APF in the X and Y directions at M1 increase by 2.61 times and 2.61 times, and the axis orbit shows a clockwise variation of the “8” shape. As the flow rate decreases, the shape of an “8” of the rotor axis orbit becomes progressively flatter. The maximum Overall vibration velocity level (OAVL) of M2 and M5 decreases by 12.03% and 1.79%, and the maximum OAVL of M3 and M4 increases by 6.52% and 2.27%. The frequency domain amplitude of M6 increases significantly in 1APF and 2APF, and the maximum increases are 12.41% and 2.24% at different flow rates. The overall sound pressure level of M6 increases by 0.42% at 0.6Qd. These findings indicate the vibration energy of M1-M5 and noise energy of M6 are related to the running condition. The axis orbit of M1 shows the shape of 8, which can significantly judge the misalignment of the shafting. Then, combined with the amplitude variation of 1APF and 2APF of the M2-M6 spectrum, the comprehensive misalignment of shafting can be further judged. The above discoveries provide reference to the diagnosis of shaft combined misalignment fault that occurred for the marine pump.
TL;DR: In this paper , sufficient conditions for the periodic motion and the pull-in instability of a micro-electromechanical system with a current-carrying conductor are established, and a new phenomenon is called as a pseudo-pull-in stability (pseudo-periodic motion).
Abstract: A micro-electromechanical system’s reliability depends strongly upon its periodic motion; however, the pull-in instability might arise when the applied voltage is high enough. No criterion is available to judge the reliability condition in a simple but effective way. This paper tackles this challenge mathematically. The sufficient conditions for the periodic motion and the pull-in instability of a micro-electromechanical system with a current-carrying conductor are established, respectively. There is an uncertain area, where the system behaves firstly periodic motion, and after a certain number of cycles, the pull-in instability occurs. This new phenomenon is called as a pseudo-pull-in stability (pseudo-periodic motion); its main factors affecting the pseudo-periodic motion are elucidated.
TL;DR: In this article , the main beam of a double-beam bridge crane was extracted to determine its quality, and the corresponding value was set, where the orthogonal test table was designed to calculate the strength and stiffness.
Abstract: Large redundant metal structures have high stability with large cost. An excellent mechanical structure should have the lower weight when satisfying its stability. Aiming at the large redundancy of the main beam metal structure of the double-beam bridge crane, the paper extracts six important parameters to determine its quality, and the corresponding value is set. The orthogonal test table is designed to calculate the strength and stiffness. In order to avoid resonance, the fixed vibration frequency and excitation frequency are calculated. The experimental results are fitted to obtain the six parameters of the quality, strength, stiffness, and natural frequency. Moreover, particle swarm optimization algorithm is used to solve the multi-objective optimization mathematical model with the design quality as the goal and the stiffness, strength, and easy resonance interval as constraints. In view of the long calculation time and poor convergence of particle swarm optimization algorithm, a module that limits the particle forward speed is added and the generation conditions of particles are redefined. The improved particle swarm algorithm shows that the first-order vibration frequency of the main beam increases from 18 Hz to 27.55 Hz. It improves the stability of the overall structure and avoids resonance with the motor frequency. Under the condition of satisfying the stability of the main beam, the quality of the main beam is reduced from 1.23 tons to 0.53 tons, with a reduction of 6%.
TL;DR: In this paper , the bisection method and an iterative method are introduced to find its pull-in voltage, and the main factors affecting the pullin voltage are elucidated.
Abstract: The pull-in behavior is an inherent property of the micro-electromechanical oscillator. The bisection method and an iterative method are introduced to find its pull-in voltage, and the main factors affecting the pull-in voltage are elucidated. The simple and efficient operability is demonstrated through theoretical analysis and result comparison.
TL;DR: In this article , a new method is proposed by configuring the movement parameters of the flexible manipulator to reduce the residual vibration of the manipulator after the movement of the deceleration.
Abstract: There are three motion stages for an industrial robot manipulator, including the acceleration stage, the constant velocity stage, and the deceleration stage. Aiming at reducing the residual vibration of the manipulator after the movement of the deceleration, a new method is proposed by configuring the movement parameters of the flexible manipulator. Firstly, we conduct experiments to verify a numerical vibration model of the manipulator, and then, we analyze the vibration suppression effect under different conditions based on the numerical model. The results show that in the range of one movement, the residual vibration can be well suppressed when the acceleration and deceleration time are set as a positive integer to the natural period of the manipulator operation; otherwise, the vibration suppression effect is not obvious and proportional to the difference between the acceleration/deceleration time and the manipulator natural period.
TL;DR: In this article , the authors proposed a nonlinear model to evaluate structural change in concrete structures by combining a structural model and an unstructured model, based on the Hooke's Law principle.
Abstract: Through the combination of two approaches to evaluating structure change, a structural model and an unstructured model, a constructed model has been proposed in this article that evaluates structural change through the expansion of a linear model following the Hooke’s Law principle. The study has relied on the pure compression model of a structure’s concrete beam with elastic modulus (E) and has added the coefficient of viscosity resistance (C) to suggest a new evaluation method. By defining the aggregation of values of both coefficients C and E through the experimental model, the input parameters are the amplitude values of the vibration spectra and the values of frequencies based on machine learning, through which Z EC values are generated. The Z EC values determine a regression plane accumulated from the aggregation of values for both C and E. The article has introduced the Z EC concept as a useful parameter for the assessment of the quality of concrete structures by the nonlinear model with the appearance of the coefficient C. The results show that the Z EC values have expressed the distribution validity according to the structure’s differing degrees of change. Depending on the texture type and the structure status, these Z EC values will form different shapes. By implementing the actual surveys from many bridges with two types of beam structures, prestressed concrete and conjugated concrete, the Z EC values show the same development trend. On the contrary, in the case of a change in mechanical structure, the Z EC values tend to increase. This evidence proves, in regard to the process of structural change, that the larger the changes in the structure, the more pronounced the distribution of Z EC values, and the wider the distribution range. This shows that the ratio of the damping coefficient C to the elastic modulus E will become increasingly unstable as the structure becomes weaker and weaker. In the future, the results from this study can be applied in the assessment of many types of actual structures.
TL;DR: Wang et al. as mentioned in this paper investigated the vibration reduction and isolation performance of the platform foundation and column base of ancient wooden buildings, taking the 1500-year-old Feiyun wooden pavilion as a case study.
Abstract: Wooden structures, as the most representative structural types of the ancient Chinese architecture, are very common and have a long history. The special construction methods adopted in ancient wooden structures, such as the platform foundations and plinth connections, enabled the ancient buildings to stand for thousands of years. However, research on the vibration reduction and isolation of the unique structures is insufficient. Thus, this paper investigates the vibration reduction and isolation performance of the platform foundation and column base of ancient wooden buildings, taking the 1500-year-old Feiyun wooden pavilion as a case study. First, using the acceleration RMS, the traffic-induced vibrations were analyzed in the time domain. It was found that the platform foundation tends to amplify the horizontal vibrations, while the column base tends to reduce them. Furthermore, background vibrations were eliminated from the measured data by using the principle of energy conservation. A frequency domain analysis of the processed data showed that the horizontal traffic-induced vibrations below 16 Hz were reduced by the platform foundation, and the column base had an obvious effect on the vibration reduction and isolation below 40 Hz. Both the platform foundation and the column base demonstrated a good effect on the reduction of traffic-induced vibrations in the vertical direction. The reported research results can be used as a basis for further studies on the dynamic performance of ancient wooden structures.
TL;DR: In this paper , the effects of damping, stiffeners, and a concrete deck on structural vibration are evaluated using the finite element method, and the simulation results indicate that installing concrete deck is the most effective approach to vibration reduction, as it can decrease overall vibration by more than 10 dB.
Abstract: The broad application of steel and steel-concrete bridges has caused significant vibration and noise problems. Although the channel steel-concrete composite girder is a commonly used bridge type, the vibration transmission performance and structural optimization design (concrete deck, stiffeners, transverse connection components, etc.) from the perspective of vibration control have not been well studied. In this paper, experimental and numerical approaches are combined to investigate the dynamic properties of a steel-channel girder in the audible frequency range (20–2000 Hz). A steel-channel girder is tested via hammering. The effects of damping, stiffeners, and a concrete deck on structural vibration are evaluated using the finite element method. The experimental results indicate negligible differences in the vibration responses on a single plate, but large differences at different sections. The results are influenced by the effects of the distance and transmission path. The numerical results reveal that increasing the damping and stiffness (e.g., setting stiffeners) are both effective in reducing vibrations. Furthermore, increasing the stiffness has a more prominent effect on structural vibrations and their frequency dependence, whereas increasing the damping ratio can stably reduce structural vibrations. The simulation results indicate that installing a concrete deck is the most effective approach to vibration reduction, as it can decrease overall vibration by more than 10 dB. Vertical web stiffeners have stronger effects on vibration reduction than other stiffening countermeasures (e.g., transverse connection components and longitudinal bottom plate stiffeners).
TL;DR: In this article , the authors explored the feasibility of using shredded tire chips as an infill material by evaluating their performance using the finite element method, and the performance of tire chips-filled trench barriers was compared with other common infill materials such as sawdust and geofoam.
Abstract: Ground vibrations induced by man-made sources like vibrating machinery, vehicular movement, traffic, construction activities involving pile driving, blasting, dynamic compaction, etc., are rising rapidly and may disrupt nearby sensitive equipment, distress, and damage sub-structures. Therefore, vibration isolation is necessary to mitigate ground-borne vibrations with suitable techniques in the present-day context. Trench barriers are one of the most efficient techniques when the other isolation techniques are inefficient at the source. Although the open trench barriers are the most efficient, their stability is still a significant concern. Hence, these trenches are generally filled with suitable absorbing materials such as sawdust, geofoam, and concrete. The present study has attempted to explore the feasibility of using shredded tire chips as an infill material by evaluating their performance using the finite element method. The performance of tire chips–filled trench barriers predicted using FE analysis is also compared with the performance of other common infill materials such as sawdust and geofoam. Numerical studies show that the vibration isolation efficiency and their performance are highly sensitive to the shear wave velocity of the soil and infill material density for infill trenches. The key findings of the study suggest that shredded tire chips can also be used as an infill material in trenches for reducing ground-borne vibrations, and its performance is comparable with geofoam-filled trenches.
TL;DR: In this article , an asymmetric hybrid supported beam piezoelectric vibration energy harvester was proposed to reduce the natural frequency of the PVE, improve the output power of PVE and meet the demand of power supply for the low-power wireless switch.
Abstract: In order to reduce the natural frequency of the piezoelectric vibration energy harvester, improve the output power of the piezoelectric vibration energy harvester, and meet the demand of power supply for the low-power wireless switch in the low-frequency vibration environment, an asymmetric hybrid supported beam piezoelectric vibration energy harvester is proposed. The theoretical model of the hybrid support beam was established. The correlation factors affecting the open-circuit voltage and the total output power of the hybrid braced beam were analyzed. The dimensional parameters of the hybrid supported beam piezoelectric energy harvester were optimized by using the optimization method of orthogonal experiments. Different coincidence degrees experiments were used to further optimize the structural design of the hybrid support beam. The test results show that the maximum output power is 770 μW, when the external excitation frequency is 1.0 g and the external resistance is 50 kΩ. Finally, a wireless switch test system was established, and the piezoelectric vibration energy harvester was experimentally verified to be capable of powering the wireless switch.
TL;DR: In this article , the modified harmonic balance method (MHBM) was used to solve the nonlinear differential equation of the circular sector oscillator analytically via the MHBM and compared the obtained results with the global residue harmonic balance, Akbari-Ganji method, and numerical Runge-Kutta method.
Abstract: This paper aims to solve the nonlinear differential equation of the circular sector oscillator analytically via the modified harmonic balance method (MHBM). To assess the reliability and the precision of the present method, we have compared the obtained results with the global residue harmonic balance method, Akbari–Ganji’s method, and numerical Runge–Kutta method which reveals that the MHBM is more reliable than others methods.
TL;DR: In this article , the conversion relationship between PA and MA (or %HA) of substations noise was established and the rationality of the model was verified, and the maximum value of the difference of MA between the calculation result of model and experimental result was less than 0.89 (or 15%).
Abstract: The level of annoyance is an important basis to determine the acceptable degree of noise and develop noise standards. Psychoacoustic annoyance (PA) calculated by Zwicker’s model and perceived annoyance (such as mean annoyance, MA and the percentage of highly annoyed population, %HA) obtained through individual self-reports are widely used. PA and MA (or %HA) cannot be directly compared because the ranges of their values are different. Thus, the conversion relationship of PA and MA (or %HA) needs to be developed. As a case study, the model between PA and MA (or %HA) of substations noise was established and the rationality of model was verified. Results showed that the maximum value of the difference of MA (or %HA) between the calculation result of model and experimental result was less than 0.89 (or 15%). In this way, the perceived annoyance of substation noise samples can be determined by calculation without experiments.
TL;DR: In this article, a coupled dynamic model for artillery launching is developed, which can predict the performance of the engraving process of the rotating band and the projectile motion in the barrel.
Abstract: The artillery launch system directly influences the muzzle energy and launching accuracy, and therefore it is important to optimize the artillery launch system’s complete process to improve the launch performance. As the objective function of the artillery launch system is non-smooth with coupling parameters in sequential processes, conventional optimization methods are hard to converge for the muti-sequential process of the interaction between the projectile and the barrel. This paper develops a coupled dynamic model for artillery launching, which can predict the performance of the engraving process of the rotating band and the projectile motion in the barrel. The independent optimization problem of the artillery launch system is divided into two subspace problems, and a modified enhanced collaborative optimization (MECO) method with global search capability is proposed, in which the distance criterion and penalty design boundary method are implemented. Results show that the MECO is dedicated not only to satisfying compatibility between coupling parameters of the two sequential processes effectively but also to improving the projectile axial speed at the muzzle and launching accuracy. The MECO maintains a much stable level of convergence than the ECO when the original optimization problem is multimodal.