Vibrational Distortion Research Articles

The Effect of Formal Specifications and Working Conditions on the Resistance and Vibration of the NACA 4415 Aircraft Wing Model

Due to their role in airplane performance, wings receive much attention considering their strength enhancement and vibration reduction. Many parameters have been considered and various materials have been used to achieve these objectives. The current work studies numerically the effect of the number of ribs and the angle of attack, on strength, response, and natural frequency at various speed values, using the ANSYS 2021 R1 solver. The adopting material is the AA 7075 T6 aluminum alloy with 71.7 GPa modulus of elasticity, 503 MPa tensile yield strength, 2810 kg/m3 density, and 0.33 Poisson’s ratio. Results show that when the velocity is increased by 30%, a corresponding elevation of 11% can be seen in vibrational distortion. Regarding the angle of attack, it was noted that doubling its value leads to a 28% reduction in vibration-induced deformation. This phenomenon occurs as a result of the alteration in the pressure distribution on the wing caused by the change in the angle of attack.

Interferometric image reorganization and screening method based on phase-shift convergence criterion

To address the challenge of obtaining high-quality interferometric images in the presence of environmental disturbances, this paper proposes a method for interferometric image reorganization and screening based on the phase-shift convergence criterion. The method begins with the acquisition of multiple sets of interferometric images, which are subsequently classified and reorganized according to the amount of phase shift. A mean absolute deviation metric is then employed to systematically screen the classified images, allowing for the selection of a subset that exhibits accurate phase shifts. Finally, the screened and combined interferometric images are evaluated for phase shift centralization through the calculation of the coefficient of variation, ensuring that the screened images conform to the expected criteria. The experimental results indicate that the average coefficient of variation of the screened interferometric images obtained using the proposed method is significantly reduced by 0.1236, 0.0968, and 0.1042 when compared to the nine sets of directly acquired interferometric images subjected to high-frequency vibration, high-amplitude vibration, and transverse distortion vibration, respectively. These data demonstrate that the proposed method can effectively adapt to various vibration environments while screening interferometric images of higher quality. Consequently, this method offers a novel approach to enhancing the vibration resistance of interferometers.

Dynamic behaviors of multiphase vortex-induced vibration for hydropower energy conversion

To satisfy the growing electricity demand, continuous and stable hydropower conversion is particularly critical in tidal power station operation. In the above industrial application, multiphase vortices will be formed, and they suck air and floating items into the flow tube, thus causing irregular pulsation that affects turbine performance. Due to nonlinear characteristics of gas-liquid coupling transfer, dynamic modeling and transition behavior of the multiphase vortex-induced vibration have improtant difficulties. This paper conducts a fluid-structure mechanic optimization model with the dynamic mesh technology to investigate multiphase vortex-induced vibration (MVIV) dynamic behaviors and reveal the internal relation between displacement responses and multiphase flow states. The fluid-induced vibration sensing platform is developed to validate MVIV transition behaviors, and a wavelet packet signal analyzing approach is adopted to acquire energy-spectrum distribution regularities of the vibration distortion state. Results show that the presented optimization modelling strategy can well obtain the MVIV transition behaviors and energy transfer mechanism. The flow flux can control the Ekman transfer intensity, and vibration energy waves take on various frequency components at the critical penetration state. Moreover, impulse energy components and structure evolution properties of high-frequency bands can be utilized to recognize the MVIV distortion peak. It can supply theoretical guidance and technology support for hydropower conversion.

Fiber Bragg grating scanning spectral distortion caused by vibration in a rotor temperature monitoring system

To improve the accuracy of the rotor temperature monitoring system using the spatial coupling method, the vibration distortion of the scanning spectra was investigated theoretically and experimentally. Vibration causes a shifted reflection peak and a narrower 3 dB bandwidth. The maximum scanning error of the FBG center wavelength plummetes, decreases slowly, and finally stabilizes with increasing g (the ratio of the coupling loss period between the collimators to the scanning spectrum time). Coordinating the vibration frequency with the demodulator scanning frequency so that the g-value is greater than 10 is the key to improving the accuracy. The scanning error increases slowly and then rapidly as the radial vibration amplitude or the shaft tilt amplitude increases. As the axial ratio of the rotor trajectory increases, the error first soars and then stabilizes when the ratio reaches 2.5. It's also been found that using the centroid peak method helps reduce errors.

Watching the Interplay between Photoinduced Ultrafast Charge Dynamics and Nuclear Vibrations.

Here is presented the ultrafast hole-electron dynamics of photoinduced metal to ligand charge-transfer (MLCT) states in a Ru(II) complex, [Ru(dcbpy)2(NCS)2]4- (dcbpy = 4,4'-dicarboxy-2,2'-bipyridine), a photoactive molecule employed in dye sensitized solar cells. Via cutting-edge computational techniques, a tailored computational protocol is here presented and developed to provide a detailed analysis of the electronic manifold coupled with nuclear vibrations to better understand the nonradiative pathways and the resulting overall dye performances in light-harvesting processes (electron injection). Thus, the effects of different vibrational modes were investigated on both the electronic levels and charge transfer dynamics through a theoretical-computational approach. First, the linear response time-dependent density functional (LR-TDDFT) formalism was employed to characterize excitation energies and spacing among electronic levels (the electronic layouts). Then, to understand the ultrafast (femtosecond) charge dynamics on the molecular scale, we relied on the nonperturbative mean-field quantum electronic dynamics via real-time (RT-) TDDFT. Three vibrational modes were selected, representative for collective nuclear movements that can have a significant influence on the electronic structure: two involving NCS- ligands and one involving dcbpy ligands. As main results, we observed that such MLCT states, under vibrational distortions, are strongly affected and a faster interligand electron transfer mechanism is observed along with an increasing MLCT character of the adiabatic electronic states approaching closer in energy due to the vibrations. Such findings can help both in providing a molecular picture of multidimensional vibro-electronic spectroscopic techniques, used to characterize ultrafast coherent and noncoherent dynamics of complex systems, and to improve dye performances with particular attention to the study of energy or charge transport processes and vibronic couplings.

Adaptive Notch Filter in a Two-Link Flexible Manipulator for the Compensation of Vibration and Gravity-Induced Distortion

This paper presents a 2-link, 2-DOF flexible manipulator control using an inverse feedforward controller and an adaptive notch filter with a direct strain feedback controller. In the flexible manipulator, transient and residue vibrations inhibit the full potential of the manipulator. Vibrations caused by abrupt changes in the direction of the links are referred to as transient vibrations, whereas residual vibrations occur when the arm takes too long to settle after engaging in the intended task. The feedforward adaptive notch filter will reduce transient vibration caused by the manipulator arm beginning and halting suddenly, while the strain feedback will assure the quick decay of leftover vibrations. Maple, Maplesim, and MATLAB tools were used to model the manipulator and create the inverse controller and adaptive notch filter. The experiments took place in the dSPACE control desk environment. The experimental results of the spectral power of strain resulting from the two strategies are compared. From the results, the adaptive notch filter control had over an 80% improvement in the reduction in resonant frequencies that contribute to vibration. The results confirmed the feasibility of the approach, characterized by very minimal transient vibrations and a quick settling of the end effector.

Aperture-dynamic properties of the sensor information in mobile object management systems

This article discusses the aperture-dynamic properties of sensor devices used in control systems for unmanned devices, in particular, automatic manipulators operating as part of robotic complexes (RTCS). The effects of interference affecting the software control systems of automatic manipulators using high-speed algorithms with interference-resistant coding under operating conditions in production are considered. It is known that in production conditions, there are sources of network interference, interference of an informational nature through communication channels, wired channels, radio engineering channels in a large radio engineering range, from vibration processes, interference and distortion in optoelectronic networks, interference that violates the safe working conditions of radioelectronic equipment. Examples of implemented algorithms based on aperture operators for controlling automatic manipulators with various program cycles, taking into account the peculiarities of production, are given. A comparative analysis was carried out with analogues having similar technological characteristics. control of automatic manipulators operating as part of robotic complexes.

Black Ecological Vibrations

Black Ecological Vibrations

Thermal performance and flexibility evaluation of metallic micro oscillating heat pipe for thermal strap

• Micro oscillating heat pipe with metal pipes and check valves is fabricated. • Thermal performance is tested in atmospheric and thermal vacuum environment. • Maximum thermal conductance of 0.8 W/K or more is achieved under both environments. • Conductance is decreased along with condenser temperature under thermal vacuum. • Dynamic stiffness of the oscillating heat pipe is less than the graphite strap. Achieving a high level of pointing accuracy in spacecraft requires that vibration and thermal distortions not be relayed to the structure. Therefore, a flexible thermal strap is essential to dissipate heat from heat-and-vibration-generating components, such as cryocoolers. This study developed a flexible and highly conductive thermal strap for space application with a micro-Oscillating Heat Pipes (OHP). So far, few studies have focused on the flexibility of a micro-OHP, particularly that of the tube type. This paper presents the results of testing strap’s thermal performance and dynamic stiffness, which is a key parameter of flexibility but has been rarely evaluated for heat pipes, including OHP. To achieve the triaxial flexibility and resistance against space environment, the OHP consists of a 10-turn micro-OHP composed of metal tubes with an inner diameter of 0.4 mm or less. It is filled with HFC-134a as the working fluid. Ten electroformed check valves are mounted in the OHP. The liquid slug is induced to flow from the condenser to the evaporator, and the OHP operates stably even in a horizontal position. Thermal performance tests have shown the maximum thermal conductance of the strap to be 0.8 W/K and the heat transfer rate to be at least 7 W. The thermal vacuum test (TVT) showed that, below 20 ℃, the thermal conductance decreases with the condenser temperature and that the OHP does not operate below −15 °C. Dynamic stiffness tests were performed on the OHP to determine the dynamic stiffness in the two directions perpendicular to the flow (along the Y and Z axes). The stiffness parallel to the flow was obtained by a finite element methods analysis using a structural model of a bent OHP based on earlier test results. The dynamic stiffness is less than 0.2 N/mm in Y and Z axis, which is less than that of the graphite thermal strap used for space application. During and after the stiffness test, the OHP continued to operate stably without any change in the temperatures of the evaporator and condenser.

Nano-Second Laser Interference Photoembossed Microstructures for Enhanced Cell Alignment

Photoembossing is a powerful photolithographic technique to prepare surface relief structures relying on polymerization-induced diffusion in a solventless development step. Conveniently, surface patterns are formed by two or more interfering laser beams without the need for a lithographic mask. The use of nanosecond pulsed light-based interference lithography strengthens the pattern resolution through the absence of vibrational line pattern distortions. Typically, a conventional photoembossing protocol consists of an exposure step at room temperature that is followed by a thermal development step at high temperature. In this work, we explore the possibility to perform the pulsed holographic exposure directly at the development temperature. The surface relief structures generated using this modified photoembossing protocol are compared with those generated using the conventional one. Importantly, the enhancement of surface relief height has been observed by exposing the samples directly at the development temperature, reaching approximately double relief heights when compared to samples obtained using the conventional protocol. Advantageously, the light dose needed to reach the optimum height and the amount of photoinitiator can be substantially reduced in this modified protocol, demonstrating it to be a more efficient process for surface relief generation in photopolymers. Kidney epithelial cell alignment studies on substrates with relief-height optimized structures generated using the two described protocols demonstrate improved cell alignment in samples generated with exposure directly at the development temperature, highlighting the relevance of the height enhancement reached by this method. Although cell alignment is well-known to be enhanced by increasing the relief height of the polymeric grating, our work demonstrates nano-second laser interference photoembossing as a powerful tool to easily prepare polymeric gratings with tunable topography in the range of interest for fundamental cell alignment studies.

Research on Vibration Saltation of the Transformer Core Caused by DC Bias of Based on Empirical Mode Decomposition

This paper presents a time–frequency analysis of the vibration of transformer under direct current (DC) bias through Hilbert–Huang transform (HHT). First, the empirical mode decomposition (EMD) process, which is the key in HHT, was introduced. The results of EMD, namely, intrinsic mode functions (IMFs), were calculated and summed by Hilbert transform (HT) to obtain time-dependent series in a 2D time–frequency domain. Next, the theory of DC bias for the transformer was analyzed. In consideration of the DC bias effect and in combination with the existing transformer vibration-related mechanism, the electromagnetic force equations of the transformer core were deduced. Lastly, a test system of vibration measurement for the transformer was set up. Three direction (x, y, and z axes) components of core vibration were measured. Decomposition of EMD and HHT spectra showed that vibration strength increased, and odd harmonics were produced with DC bias. This method illustrates the most obvious vibration distortion in the z-axis direction when the transformer is DC biased. Among them, the distortion of IMF3 has increased by more than 5 times. However, the distortion in the x-axis and y-axis directions also exists, but it is not obvious. Especially, 50 Hz component appeared in z-direction, 50 Hz component increased twofold in y-direction, and 150 Hz component increased threefold in z-direction. Results indicated that HHT can not only provide the occurrence time of DC bias but can also obtain the signal change components of the transformer vibration. Thus, HHT is a viable signal processing tool for transformer health monitoring.

Performance and Configuration Analysis of Tracking Time Anti-Windup PID Controllers

As popular as the application of Proportional Integral Derivative (PID) controller is, issues relating to saturation effects are still being addressed using different techniques. Amongst such techniques are clamping anti-windup technique and back-calculation anti-windup techniques which primary prevent the integral term of the PID control action from reaching saturation. Separate tracking time technique was applied to both cases of anti-windup techniques investigated in this research unlike the conventional tracking time. These anti-windup controllers were used to control the operation of a motorized globe valve. The results obtained after simulation in MATLAB Simulink environment showed that both techniques gave similar outputs with a stable response of magnitude 0.95 at 1.5 seconds settling time when a unit step reference input signal was applied as compared to conventional PID controller that had an overshoot of 1.04 before settling to a magnitude of 1.0 at 1.5 seconds. Vibration, instability, and operational distortion were experienced when the anti-windup techniques were cascaded. The same responses were obtained when their outputs were combined to control the motorized globe valve. Other interesting mathematical models of important components are contained in the full paper.

Vibronic resonance is inadequately described by one-particle basis sets

Vibrational-electronic (vibronic) resonance and its possible role in energy and charge transfer have been experimentally and theoretically investigated in several photosynthetic proteins. Using a dimer modeled on a typical photosynthetic protein, we contrast the description of such excitons provided by an exact basis set description, as opposed to a basis set with reduced vibrational dimensionality. Using a reduced analytical description of the full Hamiltonian, we show that in the presence of vibrational excitation both on electronically excited as well as unexcited sites, constructive interference between such basis states causes vibronic coupling between excitons to become progressively stronger with increasing quanta of vibrational excitation. This effect leads to three distinguishing features of excitons coupled through a vibronic resonance, which are not captured in basis sets that restrict ground state vibrations: (1) the vibronic resonance criterion itself, (2) vibronically assisted perfect delocalization between sites even though purely electronic mixing between the sites is imperfect due to energetic disorder, and (3) the nuclear distortion accompanying vibronic excitons becoming increasingly larger for resonant vibronic coupling involving higher vibrational quanta. In terms of spectroscopically observable limitations of reduced basis set descriptions of vibronic resonance, several differences are seen in absorption and emission spectra but may be obscured on account of overwhelming line broadening. However, we show that several features such as vibronic exciton delocalization and vibrational distortions associated with electronic excitations, which ultimately dictate the excited state wavepacket motions and relaxation processes, are fundamentally not described by basis sets that restrict ground state vibrations.

Digital domain dynamic path accumulation method to compensate for image vibration distortion for CMOS-time-delay-integration image sensor

A digital domain dynamic path accumulation method for a time-delay-integration (TDI) image sensor that can realize on-chip compensation for image distortion caused by sensor vibration is proposed. Through the proposed method, the exposure signals are controlled to enter the corresponding accumulator according to the vibration vector, ensuring the synchronous accumulation of different stages of pixels on the same object. The behavior level model of the method is established. The structural similarity (SSIM) between images without distortion, distorted images, and images compensated for by the proposed method is simulated and analyzed to verify the effectiveness of the method. Compared with conventional TDI, the SSIM between images with and without vibration is improved from 0.2322 to 0.9858, as the vibration level is 1 pixel per stage. With fixed TDI stages and the vibration level varying from 0 to 2 pixels per stage, the SSIM of conventional TDI drops rapidly to about 0.2 while that of the dynamic path accumulation method maintains at about 0.95. The proposed method is suitable for an antivibration CMOS-TDI image sensor of remote imaging systems.

Comparison of the Vibration Response of a Rotary Dobby with Cam-Link and Cam-Slider Modulators

Abstract This article presents the kinematic modeling and analysis of cam profiles of two different types of modulator: a cam-link and a cam-slider modulators. Kinematic and dynamic models of the two different modulators were established based on the motion curves of the main shaft of the rotary dobby. Simulations were carried out in Simulink to analyze the vibration responses under different rotary speeds, and vibration responses of the two mechanisms were compared. The results show that the cam-link modulator vibrates smoothly at speeds of <700 rpm, and theoretically, the speed should not exceed 1,400 rpm. The cam-slider modulator vibrates smoothly at speeds of <500 rpm, and theoretically, the speed should not exceed 1,000 rpm. The cam-slider modulator is more suitable for use at low speeds, whereas the cam-link modulator is more appropriate for high speeds. When both the cam-slider and cam-link modulators operate at high speeds, vibration distortion occurs, leading to bifurcation and chaotic vibration. Further knowledge of the complex behaviors associated with detachment of the follower from the cam can support the design of more sophisticated controllers aimed at avoiding follower detachment.

An ultrathin conformable vibration-responsive electronic skin for quantitative vocal recognition

Flexible and skin-attachable vibration sensors have been studied for use as wearable voice-recognition electronics. However, the development of vibration sensors to recognize the human voice accurately with a flat frequency response, a high sensitivity, and a flexible/conformable form factor has proved a major challenge. Here, we present an ultrathin, conformable, and vibration-responsive electronic skin that detects skin acceleration, which is highly and linearly correlated with voice pressure. This device consists of a crosslinked ultrathin polymer film and a hole-patterned diaphragm structure, and senses voices quantitatively with an outstanding sensitivity of 5.5 V Pa−1 over the voice frequency range. Moreover, this ultrathin device (<5 μm) exhibits superior skin conformity, which enables exact voice recognition because it eliminates vibrational distortion on rough and curved skin surfaces. Our device is suitable for several promising voice-recognition applications, such as security authentication, remote control systems and vocal healthcare.

Vibrational Effects in X-ray Absorption Spectra of Two-Dimensional Layered Materials

With the examples of the C $K$-edge in graphite and the B $K$-edge in hexagonal BN, we demonstrate the impact of vibrational coupling and lattice distortions on the X-ray absorption near-edge structure (XANES) in 2D layered materials. Theoretical XANES spectra are obtained by solving the Bethe-Salpeter equation of many-body perturbation theory, including excitonic effects through the correlated motion of core-hole and excited electron. We show that accounting for zero-point motion is important for the interpretation and understanding of the measured X-ray absorption fine structure in both materials, in particular for describing the $\sigma^*$-peak structure.

Structural changes upon electronic excitation in 1,2-dimethoxybenzene from rotationally resolved electronic spectroscopy of various isotopologues

The structural changes of 1,2-dimethoxybenzene upon electronic excitation have been elucidated from a comparison of ab initio calculations and fits of the structural changes to experimental inertial parameters both in the basis of internal coordinates as well as in vibrational distortion coordinates. It is shown that the use of vibrational distortion coordinates leads to better agreement with the results of ab initio optimized structures compared to the use of internal coordinates in cases, that the inertial data are not sufficient for a complete structure determination. 1,2-dimethoxybenzene has been found to be only very slightly ortho-quinoidally distorted upon electronic excitation, in contrast to former expectations.

Spectroscopy of the electronic excited states of thioxophosphane, HPS, and of its deuterated species.

The stable low energy states of the HPS and DPS molecules have been studied through multi-reference ab initio methods in conjunction with large atomic basis sets. Stable states for these species have been examined up to 7 eV above the ground state minimum. We found six stable electronic states that are mostly mono-configurational. These states may be involved in the photodynamics and photodissociation of this molecule. In particular, the 2 1A' state presents two minima on the potential energy surface, one of them close to linear configuration. This state may be populated after the absorption of a visible photon from the ground state and gives rise to large amplitude motions that may eventually induce isomerization to electronically excited HSP. Moreover, we characterized these states spectroscopically to facilitate the assignment of the vibronic spectra of the HPS and DPS species. For these low-energy states, we thus computed vertical and adiabatic excitation energies, and for the stable ones, a full set of spectroscopic constants including harmonic frequencies and anharmonic vibrational, rotational, and centrifugal distortion constants. The calculated potential energy surfaces for these states have been used in a variational procedure to deduce the pattern of vibrational levels up to 4000 cm-1 above the corresponding vibrationless level. Our data may serve for the assignment of the IR and Vis spectra of HPS and DPS.

Understanding the quantum mechanical properties of hydrogen bonds in solvated biomolecules from cluster calculations

Here we use a combination of molecular mechanics force fields and high level ab initio calculations to study hydrogen bonding interactions in small hybrid peptide-water clusters relevant for larger biological aggregates. Potential energy surfaces interrogating pairwise interactions, constructed from popular biological force fields and water models, are in relatively good agreement with those from first principles. We also examine the importance of three-body interactions in peptide-peptide and peptide-water hydrogen bonds and show that they can contribute between 4% and 19% of the total interaction energy. Using an energy decomposition analysis we show that this mostly originates from many-body polarization. The variations are caused by changes in the topology of the network and vibrational distortions of protons.