Mechanical Oscillator Research Articles

Preparation and evaluation of microcapsules of sodium alginate based on microfluidic technology

Many active ingredients in food products are destroyed by gastric acids and enzymes as they pass through the stomach, thereby reducing the desired effect of the target ingredient. In addition, traditional microcapsule preparation methods usually break up the dispersion by mechanical stirring or oscillation, which generates droplets of uneven size and inconsistent inclusion content, and mechanical external forces may cause denaturation and inactivation of active substances. This study aimed to use microfluidics to generate Oil-in-water-in-oil (O/W/O) droplet structures with good monodispersity and highly tunable properties, and to further prepare microcapsules with high encapsulation rate and targeted intestinal release by taking advantage of the cross-linking properties of alginate that reacts with Ca2+ under acidic conditions. Finally, the particle size distribution, release effect, encapsulation effect and oxidative stability of the core-shell microcapsules were evaluated. In this study, two types of microcapsules, homogeneous and core-shell microcapsules, were prepared by selecting tea polyphenols and vitamin E as models for hydrophilic and lipophilic bioactive compounds, respectively. Thin shell microcapsules with a shell thickness of about 25 μm were prepared using PDMS chip conditioning. Large microcapsules with a particle size of 230 μm were generated by using capillary glass tube chips, which had an excellent antioxidant property with a retention rate of 88.66 ± 1.25% of VE after 20 days of storage at 4 °C, while all of the VE was oxidized in the bare environment. In addition, in simulated gastric fluid, the release of VE was only about 20%, while in artificial intestinal fluid, the release was close to 100%, so the microcapsules also had intestinal targeting properties.

On phase correspondence between chemical oscillations in liquid Belousov-Zhabotinsky mixture filling catalyst-containing matrix and resulted gel's chemomechanical oscillations

We investigated phases and phase differences between coupled mechanical and chemical self-oscillations running in two kinds of newly synthesised chemomechanical gels. Processing of experimental data was model-free and it was based on spectral and wavelet approaches of the theory of dynamical systems. It was applied to samples of different sizes and compositions (Ru- and Fe-based gels). It was revealed that the Ru-based gels demonstrate a faster mechanical response to the redox changes of the Ru-moiety coupled to the Belousov-Zhabotinsky chemical reaction than the Fe-based gels. This demonstrated a significant phase difference between the redox changes of the Fe-moiety and the mechanical oscillations. Special attention was paid to the phase-coupling features for averaged higher harmonics, which are significant due to the high degree of nonlinearity of the chemomechanical oscillatory process.

Exact instanton transseries for quantum mechanics

We calculate the instanton corrections to energy spectra of one-dimensional quantum mechanical oscillators to all orders and unify them in a closed form transseries description. Using alien calculus, we clarify the resurgent structure of these transseries and demonstrate two approaches in which the Stokes constants can be derived. As a result, we formulate a minimal one-parameter transseries for the natural nonperturbative extension to the perturbative energy, which captures the Stokes phenomenon in a single stroke. We derive these results in three models: quantum oscillators with cubic, symmetric double well and cosine potentials. In the latter two examples, we find that the resulting full transseries for the energy has a more convoluted structure that we can factorise in terms of a minimal and a median transseries. For the cosine potential we briefly discuss this more complicated transseries structure in conjunction with topology and the concept of the resurgence triangle.

Harmonic resonance and entrainment of propagating chemical waves by external mechanical stimulation in BZ self-oscillating hydrogels

Smart polymer materials that are nonliving yet exhibit complex "life-like" or biomimetic behaviors have been the focus of intensive research over the past decades, in the quest to broaden our understanding of how living systems function under nonequilibrium conditions. Identification of how chemical and mechanical coupling can generate resonance and entrainment with other cells or external environment is an important research question. We prepared Belousov-Zhabotinsky (BZ) self-oscillating hydrogels which convert chemical energy to mechanical oscillation. By cyclically applying external mechanical stimulation to the BZ hydrogels, we found that when the oscillation of a gel sample entered into harmonic resonance with the applied oscillation during stimulation, the system kept a "memory" of the resonant oscillation period and maintained it post stimulation, demonstrating an entrainment effect. More surprisingly, by systematically varying the cycle length of the external stimulation, we revealed the discrete nature of the stimulation-induced resonance and entrainment behaviors in chemical oscillations of BZ hydrogels, i.e., the hydrogels slow down their oscillation periods to the harmonics of the cycle length of the external mechanical stimulation. Our theoretical model calculations suggest the important roles of the delayed mechanical response caused by reactant diffusion and solvent migration in affecting the chemomechanical coupling in active hydrogels and consequently synchronizing their chemical oscillations with external mechanical oscillations.

Acoustic Torsional Mechanical Oscillator Driven by Wave‐Matter Orbital Angular Momentum Transfer with Quality Factor >1000

AbstractThe experimental realization of a macroscopic mechanical oscillator driven by the nondissipative transfer of angular momentum from sound waves to matter is presented, with quality factor up to Q ≈ 2000. This performance is two orders of magnitude higher than previously reported values Q ≈ 10. This result is achieved through the use of a monolithic metallic torsional pendulum and improved assembling method of the constitutive parts of the apparatus. This allows a substantial reduction of the internal losses associated with the imaginary part of the complex shear modulus compared with previous attempts using photocurable resin materials.

Thermoacoustic Fano-based bistable energy converters: A new concept of thermoacoustic engine

In this work, we propose a highly efficient thermoacoustic energy converter based on the concept of Fano-based bistable systems. The proposed device, in its simplest version consists of a bilayer polymeric cylinder with harder core and softer and thinner shell. The heat source enforced at the core-shell interface induces thermo-mechanical stress fields. The stress field causes the occurrence of wrinkling patterns in the shell and the release of acoustic energy by a snap-through-buckling mechanism. We show that, when the shell is acoustically resonant at a specific frequency, the synergetic interplay of snap-through and Fano-resonances is capable of producing high amplitude and long-lasting pressure oscillations. In other words, under specifics conditions, the synergetic interaction between wrinkling instabilities and Fano resonance is able to extract mechanical energy from the heat source. The efficiency of the system in converting heat-into-work under resonant conditions is at least 6 times higher than that out of resonance. Notably, for a temperature difference of 1 K between the heat source (the hot thermal reservoir beneath the resonant shell) and the surrounding water (the cold thermal reservoir above the resonant shell), the system may reach a conversion efficiency above 70% of the theoretical Carnot efficiency. The so-generated mechanical oscillations can be converted in electrical energy for instance by using sound-to-energy converting systems such as conventional loudspeakers. The characteristics of the heat source have been selected to be representative of low-grade thermal sources (e.g. waste-heat, in particular intermittent sources) abundantly available in natural, and industrial contexts. Importantly, the systems may be adapted to many different geometries spanning from the proposed core-shell cylinders in which the heat source can be either inside the tube (for instance an exhaust gas/liquid outlet) or outside the tube, to plates (like a solar panel system).

Coherent control of an optical tweezer phonon laser

The creation and manipulation of coherence continues to capture the attention of scientists and engineers. The optical laser is a canonical example of a system that, in principle, exhibits complete coherence. Recent research has focused on the creation of coherent, laser-like states in other physical systems. The phonon laser is one example where it is possible to amplify self-sustained mechanical oscillations. A single mode phonon laser in a levitated optical tweezer has been demonstrated through appropriate balance of active feedback gain and damping. In this work, coherent control of the dynamics of an optical tweezer phonon laser is used to share coherence between its different modes of oscillation, creating a multimode phonon laser. The coupling of the modes is achieved by periodically rotating the asymmetric optical potential in the transverse focal plane of the trapping beam via trap laser polarization rotation. The presented theory and experiment demonstrate that coherence can be transferred across different modes of an optical tweezer phonon laser, and are a step toward using these systems for precision measurement and quantum information processing.

Effect of local mechanical oscillation on the performance of PCM thermal energy storage with various unit configurations

The low thermal conductivity of phase change materials is an essential restriction to their usage in thermal energy storage units. In this research, applying local oscillation by an oscillator on the portion of a side wall of RT35 enclosure is presented as a novel method to enhance the charging rate. The finite volume method is conducted for the numerical study on the effect of different configuration parameters including enclosure aspect ratios in the range of 1: 6, 1:2, 1:1, and 2:1, various oscillator lengths of 5, 10, 15, and 20 mm, as well as different oscillation frequencies of 10, 100 and 1000 Hz on the melting performance. Results indicate that applying local oscillation enhances the melting rate by more than 50 % as compared to without using oscillator because of enhancing convection heat transfer originating from vorticity intensification. The improvement of required time for melting the PCM is 91.55 %, 54.66 %, 67.7 % and 71.4 % for aspect ratios of 1:6, 1:2, 1:1 and 2:1, respectively.Results show that the melting performance is enhanced as the length of the oscillator increases. The required time for complete melting is obtained equal to 24, 26, 28, and 33 min at the oscillator length of 20, 15, 10, and 5 mm, respectively. The finding on the effect of oscillation frequency reveals that the liquid fraction, mean temperature, and heat flux at a specified time of melting process becomes higher as the oscillation frequency increases with significant enhancement of vorticity around the oscillator. At the frequency of 1000 Hz, the required time for melting is reduced by 9.5 % and 20.8 % as compared to frequencies of 100 Hz and 10 Hz, respectively. Other results also indicate that the higher Nusselt number is obtained for a higher enclosure aspect ratio.

Proposal for observing nonclassicality in highly excited mechanical oscillators by single photon detection

Proposal for observing nonclassicality in highly excited mechanical oscillators by single photon detection

Indirect Cooling of Weakly Coupled Trapped-Ion Mechanical Oscillators

Cooling the motion of trapped ions to near the quantum ground state is crucial for many applications in quantum information processing and quantum metrology. However, certain motional modes of trapped-ion crystals can be difficult to cool due to weak or zero interaction between the modes and the cooling radiation, typically laser beams. We overcome this challenge by coupling a mode that interacts weakly with cooling radiation to one that interacts strongly with cooling radiation using parametric modulation of the trapping potential, thereby enabling indirect cooling of the weakly interacting mode. In this way, we demonstrate near-ground-state cooling of motional modes with weak or zero cooling radiation interaction in multi-ion crystals of the same and mixed ion species, specifically Be+9−Be+9, Be+9−Mg+25, and Be+9−Mg+25−Be+9 crystals. This approach can be generally applied to any Coulomb crystal where certain motional modes cannot be directly cooled efficiently, including crystals containing molecular ions, highly charged ions, charged fundamental particles, or charged macroscopic objects. Published by the American Physical Society 2024

On the Synchronization of Parallel Power Converters via Emulation of Linear Mechanical Oscillators

On the Synchronization of Parallel Power Converters via Emulation of Linear Mechanical Oscillators

ABORDARE NUMERICĂ ASUPRA DETERMINĂRII FRECVENȚELOR DE REZONANȚĂ ALE STÂLPILOR TURBINELOR EOLIENE

The study presents an approach based on 3D numerical methods for estimating the resonant frequencies of the mast of a wind turbine. This system comprises components that operate on electromechanical principles that are sources of mechanical oscillations. The FreeCAD environment is used to create geometries with complex structures, and the MATLAB environment is used to perform the numerical study specific to mechanical analysis. A comparison with experimental data is carried out for a given configuration to validate the method.

Vibration mitigation using dual-open and infilled trenches in layered soil media: Field tests and numerical simulations

Ground-borne vibrations are increasing at a rapid rate due to the rise in urban expansion and industrial activities. The current solution to mitigate the unwanted vibrations is limited to the use of single trenches that require unrealistic depths. This paper presents the possibilities of using dual open and infilled trenches to mitigate the vibrations generated due to continuous harmonic motions. Full-scale field tests and comprehensive numerical studies were performed to systematically design dual trenches. The field vibration tests were performed under a wide range of frequencies using the Lazan-type mechanical oscillator. Similarly, numerical studies have been performed using finite element analysis software, PLAXIS 2D. Expanded polystyrene (EPS) geofoams of different densities, bentonite, ceramsite, concrete, and sand-rubber mixture were used as the infill materials. The normalized depths of 0.40 and 0.50 were observed as the optimal values to reach an average amplitude reduction ratio (average ARR) of 0.25 for the dual open and EPS15-infilled trenches, respectively. The isolation efficiency of EPS15-infilled trenches was observed to be 178 % higher compared to the EPS48-infilled trenches. The performance difference between EPS15 and ceramsite-filled dual trenches was observed to be only 4 % in terms of average ARR, the former being superior.

Experimental characterization of a nonlinear mechanical oscillator with softening behaviour for large displacements

This paper presents an experimental insight into the performance of a mechanical oscillator consisting of an X-shaped-spring configuration. This configuration achieves an overall softening characteristic with quasi-zero stiffness behaviour far away from the static equilibrium point. Such a geometrical nonlinear configuration has attracted significant research attention in the last few years, particularly for its application as a vibration isolator with the possibility to extend the quasi-zero-stiffness region beyond that of the classical three-spring nonlinear isolator. However, previous experimental evidence has been limited to small amplitude vibration excitation only. Furthermore, it has been focused mainly on the isolation region, rather than on the large amplitude response, thus circumventing an insight on the damping effects and its modelling. To address this gap, in this paper, both frequency sweeps and random excitations are applied to a prototype device for experimental characterization. A nonlinear stiffness model is developed based on the geometry of the system and a nonlinear damping model is assumed based on experimental observation. The proposed model accurately describes the dynamic behaviour of the system as shown by comparison of theoretical and experimental data.

A statistical analysis of causal decomposition methods applied to Earth system time series

Causal Decomposition (CD) constitutes a novel and widely accepted method for discovering and quantifying the internal causal relationships inherent to complex systems. This new causality bases not on time nor state. Instead, it relies on instantaneous phase coherence between the corresponding Intrinsic Mode Functions (IMFs) of the signals, obtained via Empirical Mode Decomposition (EMD). In this paper we compare the results obtained with two noise-assisted methods: Ensemble EMD (EEMD) and Noise Assisted Multivariate EMD (NA-MEMD). Given the inherent stochastic nature of noise-assisted methods, CD was treated as a randomized experiment. Hence, we repeated procedures to perform a robust statistical analysis. Confidence intervals, adequate normality conditions and differential causality hypothesis testing were then evaluated. The methodology was adjusted through the paradigmatic case of a forced mechanical oscillator, since the causal implications are known in advance. CD was then applied to a couple of series from the Earth system: insolation and oxygen isotope rate. Differential causality was established in favor of insolation at the frequency corresponding to the obliquity cycle. The apparent causality detected with EEMD on other time scales was discarded and attributed to a mode mixing problem. Therefore, NA-MEMD outperformed EEMD with less mode mixing and sharper mode alignment.

Squeezing and entangling two microwave modes of electro-optomechanical systems with two driving lasers

We propose an effective scheme to generate the squeezed vacuum states of two microwave fields, bipartite and genuine tripartite entanglement in a compound four-mode electro-optomechanical system with two driving lasers of different amplitudes. We find that two microwave fields can be squeezed simultaneously when the effective coupling constants between mechanical oscillator and two microwave fields are chosen appropriately. In particular, the squeezing of one microwave mode can be larger than 3 dB even at high temperature. We also find that bipartite and genuine tripartite entanglement can be generated in this system which are robust against thermal fluctuations. Our scheme may have potential applications in quantum information processing and quantum metrology.

Multipole Approach to the Dynamical Casimir Effect with Finite-Size Scatterers.

A mirror subjected to a fast mechanical oscillation emits photons out of the quantum vacuum-a phenomenon known as the dynamical Casimir effect (DCE). The mirror is usually treated as an infinite metallic surface. Here, we show that, in realistic experimental conditions (mirror size and oscillation frequency), this assumption is inadequate and drastically overestimates the DCE radiation. Taking the opposite limit, we use instead the dipolar approximation to obtain a simpler and more realistic treatment of DCE for macroscopic bodies. Our approach is inspired by a microscopic theory of DCE, which is extended to the macroscopic realm by a suitable effective Hamiltonian description of moving anisotropic scatterers. We illustrate the benefits of our approach by considering the DCE from macroscopic bodies of different geometries.

Ultracoherent Nanomechanical Resonators Based on Density Phononic Crystal Engineering

Micromechanical and nanomechanical systems with exceptionally low dissipation rates are enabling the next-generation technologies of ultrasensitive detectors and quantum information systems. New techniques and methods for lowering the dissipation rate have in recent years been discovered and allowed for the engineering of mechanical oscillators with phononic modes that are extremely well isolated from the environment and thus possess quality factors close to and beyond 1×109. A powerful strategy for isolating and controlling a single phononic mode is based on phononic crystal engineering. Here we propose a new method for phononic crystal engineering of nanomechanical oscillators that is based on a periodic variation of the material density. To circumvent the introduction of additional bending losses resulting from the variation of material density, the added mass constitutes an array of nanopillars in which the losses will be diluted. Using this novel technique for phononic crystal engineering, we design and fabricate corrugated mechanical oscillators with quality factors approaching 1×109 in a room temperature environment. The flexibility space of these new phononic crystals is large and further advancement can be attained through optimized phononic crystal patterning and strain engineering via topology optimization. This will allow for the engineering of mechanical membranes with quality factors beyond 1×109 at room temperature. Such extremely low mechanical dissipation rates will enable the development of radically new technologies such as quantum-limited atomic force microscopy at room temperature, ultrasensitive detectors of dark matter, spontaneous waveform collapses, gravity, and high-efficiency quantum information transducers. Published by the American Physical Society 2024

Control of Vibratory Feeder Device Mechanical Frequency Using the Modification of the Sinusoidal Supply Voltage Signal

In the industrial and sales processes, dosing systems of various constructions, whose operation is based on mechanical vibrations (vibratory feeders), are very often used. These systems face many problems, such as resonant frequency, flow instability of dosed product, instability of mechanical vibration amplitude, etc., because most of them are based on controlling the frequency of the electrical signal of the supply voltage. All these factors negatively affect the durability and reliability of the vibratory feeder systems. During this research, an automatic control system for vibratory feeder was created, whose control process is based on the modification of the sinusoidal signal (partially changing the signal area). In addition, such a way of controlling the vibratory feeder is not discussed in the literature. As the research conducted in this paper has shown, while using sinusoidal signal modification it was possible to achieve a stable flow rate of bulk production (the flow rate varied from 0 to 100 g/s when the frequency of mechanical vibrations changed from 1 to 50 Hz) and a stable amplitude of mechanical oscillations was achieved and equal to 1.5 mm. The control system is based on the microcontroller PIC24FV32KA302 for which the special software was developed. The thyristor BTA16 used for voltage modification of the sinusoidal signal made it possible to ensure the reliable control of the sinusoidal voltage modification process.

Molecular optomechanics in the anharmonic regime: from nonclassical mechanical states to mechanical lasing

Cavity optomechanics aims to establish optical control over vibrations of nanoscale mechanical systems, to heat, cool or to drive them toward coherent, or nonclassical states. This field was recently extended to encompass molecular optomechanics: the dynamics of THz molecular vibrations coupled to the optical fields of lossy cavities via Raman transitions. The molecular platform should prove suitable for demonstrating more sophisticated optomechanical effects, including engineering of nonclassical mechanical states, or inducing coherent molecular vibrations. We propose two schemes for implementing these effects, exploiting the strong intrinsic anharmonicities of molecular vibrations. First, to prepare a nonclassical mechanical state, we propose an incoherent analogue of the mechanical blockade, in which the molecular anharmonicity and optical response of hybrid cavities isolate the two lowest-energy vibrational states. Secondly, we show that for a strongly driven optomechanical system, the anharmonicity can suppress the mechanical amplification, shifting and reshaping the onset of coherent mechanical oscillations. Our estimates indicate that both effects should be within reach of existing platforms for Surface Enhanced Raman Scattering.