Harmonic Behavior Research Articles

A statistical mechanics framework for polymer chain scission, based on the concepts of distorted bond potential and asymptotic matching

To design increasingly tough, resilient, and fatigue-resistant elastomers and hydrogels, the relationship between controllable network parameters at the molecular level (bond type, non-uniform chain length, entanglement density, etc.) to macroscopic quantities that govern damage and failure must be established. Many of the most successful constitutive models for elastomers have been rooted in statistical mechanical treatments of polymer chains. Typically, such constitutive models have used variants of the freely jointed chain model with rigid links. However, since the free energy state of a polymer chain is dominated by enthalpic bond distortion effects as the chain approaches its rupture point, bond extensibility ought to be accounted for if the model is intended to capture chain rupture. To that end, a new bond potential is supplemented to the freely jointed chain model (as derived in the uFJC framework of Buche and Silberstein (2021) and Buche et al. (2022)), which we have extended to yield a tractable, closed-form model of single chain behavior that should be amenable to continuum-level constitutive model development. Inspired by the asymptotically matched uFJC model response in both the low/intermediate chain force and high chain force regimes, a simple, quasi-polynomial bond potential energy function is derived. This bond potential exhibits harmonic behavior near the equilibrium state and anharmonic behavior for large bond stretches tending to a characteristic energy plateau (akin to the Lennard-Jones and Morse bond potentials). Using this bond potential, approximate yet highly-accurate analytical functions for bond stretch and chain force dependent upon chain stretch are established. Then, using this polymer chain model, a stochastic thermal fluctuation-driven chain rupture framework is developed. This framework is based upon a force-modified tilted bond potential that accounts for distortional bond potential energy, allowing for the derivation and subsequent calculation of the dissipated chain scission energy. The cases of rate-dependent and rate-independent scission are accounted for throughout the rupture framework. The impact of Kuhn segment number on chain rupture behavior is also investigated. The model is fit to single chain mechanical response data collected from atomic force microscopy tensile tests for validation and to glean deeper insight into the molecular physics taking place. Due to their analytical nature, this polymer chain model and the associated rupture framework can in the future be implemented in finite element models accounting for fracture and fatigue in polydisperse elastomer networks.

Plasmon resonances in silicon nanowires: geometry effects on the trade-off between dielectric and metallic behaviour

Surface plasmons (SP) arising from nanometer silicon objects allow control and manipulation of light at the nanoscale exhibiting significant advantages in a plethora of applied research areas such as nanophotonic, environment, energy, biology, and medicine. These SP can achieve more significant potential, thanks to the industrial scalability and low cost offered by silicon compared with other metals and semiconductor nanosized materials. However, as they have not yet been fully understood and exploited, silicon’s plasmon mechanisms need to be thoroughly studied. In particular, the influence of nanowire shape on surface plasmon behavior and the existence of physical constraints for surface plasmon excitation remains to be fully understood. In a previous study, we have demonstrated that thanks to their anisotropic one-dimensional shape, silicon nanowires sustain two types of plasmon resonances, the longitudinal ones along the main nanowire axis, with harmonic behavior and the transversal resonance, which takes place along the diameter. We demonstrated our data on a particular set of sizes, 30 nm for the diameter and about 400 nm for the length. Here we show how the resonances change when the diameter is smaller than 30 nm and the length is smaller than 400 nm. We use electron energy loss spectroscopy to map the several plasmonic modes from the fundamental one to the higher orders, with the goal of understanding how the SP resonances change when the diameter and length are smaller than 30 nm and 400 nm, respectively. We then use modeling to support the experimental findings. According to the mode order, the study illustrates the various locations inside the nanowires where discrete resonance spots can be found. Another important finding of this work is the disappearance of the surface plasmon modes for nanowires shorter than a predetermined threshold for any diameter in the range investigated, showing that the nanowire length is a key factor in maintaining electron oscillations. With this finding, a crucial physical limit for this phenomenon in silicon is established.

Rotational modulation in A and F stars: magnetic stellar spots or convective core rotation?

ABSTRACT The Kepler mission revealed a plethora of stellar variability in the light curves of many stars, some associated with magnetic activity or stellar oscillations. In this work, we analyse the periodic signal in 162 intermediate-mass stars, interpreted as Rossby modes and rotational modulation – the so-called hump and spike feature. We investigate whether the rotational modulation (spike) is due to stellar spots caused by magnetic fields or due to Overstable Convective (OsC) modes resonantly exciting g modes, with frequencies corresponding to the convective core rotation rate. Assuming that the spikes are created by magnetic spots at the stellar surface, we recover the amplitudes of the magnetic fields, which are in good agreement with theoretical predictions. Our data show a clear anticorrelation between the spike amplitudes and stellar mass and possibly a correlation with stellar age, consistent with the dynamo-generated magnetic fields theory in (sub)-surface convective layers. Investigating the harmonic behaviour, we find that for 125 stars neither of the two possible explanations can be excluded. While our results suggest that the dynamo-generated magnetic field scenario is more likely to explain the spike feature, we assess further work is needed to distinguish between the two scenarios. One method for ruling out one of the two explanations is to directly observe magnetic fields in hump and spike stars. Another would be to impose additional constraints through detailed modelling of our stars, regarding the rotation requirement in the OsC mode scenario or the presence of a convective-core (stellar age).

Anti-plane shear waves in an elastic strip rigidly attached to an elastic half-space

We consider the anti-plane shear waves in a domain consisting of an infinite layer with a thin coating lying on an elastic half-space. The elastic properties of the coating, layer, and half-space are assumed to be different. On the free upper surface we assume the compatibility condition within the Gurtin–Murdoch surface elasticity, whereas at the plane interface we consider perfect contact. For this problem there exist two possible regimes related to waves exponentially decaying in the half-space. The first one, called transversely exponential–transversely exponential (TE–TE) regime, is related to waves described by exponential in transverse direction functions; the second, transversely harmonic–transversely exponential (TH–TE) regime, corresponds to waves in the upper layer which have the harmonic behaviour in the transverse direction. Detailed analysis of the derived dispersion equations for both regimes is provided. In particular, the effects of surface stresses, the layer thickness as well as of the ratio of shear moduli of the upper layer and half-space on the dispersion curves is analysed.

Selective Harmonic Elimination in a Multilevel Inverter Using Multi-Criteria Search Enhanced Firefly Algorithm

This research paper proposes the new multi-criteria search based enhanced firefly algorithm for solving selective harmonic elimination in a multilevel inverter. This new enhanced firefly utilizes adaptive nature of social and cognitive components to find the global optima. To see the effectiveness of the proposed algorithm and for the evaluation of results, a three phase nine level cascaded multilevel inverter is used. It is compared with existing meta-heuristic algorithms namely particle swarm optimization and firefly algorithm to validate its effectiveness. Crucial parameters for optimization, including population size and number of iterations, are kept same for comparison. For comparison, total harmonic distortion and convergence behaviour of algorithms against various modulation index values are considered. Moreover, results have clearly indicated that the proposed algorithm has surpassed particle swarm optimization and firefly algorithms in terms of convergence behaviour by attaining lower fitness value in lesser number of iterations. Finally, the experimental validation of selective harmonic elimination in multi-level inverter is also performed and analyzed.

A neural network assisted 171Yb+ quantum magnetometer

A versatile magnetometer must deliver a readable response when exposed to target fields in a wide range of parameters. In this work, we experimentally demonstrate that the combination of171Yb+ atomic sensors with adequately trained neural networks enables us to investigate target fields in distinct challenging scenarios. In particular, we characterize radio frequency (RF) fields in the presence of large shot noise, including the limit case of continuous data acquisition via single-shot measurements. Furthermore, by incorporating neural networks we significantly extend the working regime of atomic magnetometers into scenarios in which the RF driving induces responses beyond their standard harmonic behavior. Our results indicate the benefits to integrate neural networks at the data processing stage of general quantum sensing tasks to decipher the information contained in the sensor responses.

Mixed stabilized finite element methods in linear elasticity for the velocity–stress equations in the time and the frequency domains

In this work we present stabilized finite element methods for the mixed velocity–stress elasticity equations and for its irreducible velocity form. This is done both for the time and frequency domains, the latter being obtained by assuming a harmonic behavior in time. Stabilization methods that belong to the computational framework of the Variational Multi-Scale formulation are used. It is shown that the adequate selection of the algorithmic parameters on which the formulation depends allows one to switch from the primal to the dual functional framework. The performance of the method is tested through several numerical examples, one of which includes a convergence study.

Lattice dynamics of β−FeSi2 nanorods

Here we present a combined experimental and ab initio lattice dynamics study of the semiconducting $\ensuremath{\beta}$ phase of $\mathrm{Fe}{\mathrm{Si}}_{2}$. A polycrystalline $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}$ film was prepared on Si(111) and single-crystalline, self-assembled $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}$ nanorods were grown on Si(110) by molecular beam epitaxy. Both types of nanostructures were obtained by annealing of precursor structures, an epitaxial Fe film in the case of the film and high-aspect-ratio $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}$ nanowires in the case of the nanorods. The morphology and crystalline structure of the samples were investigated by reflection high-energy electron diffraction, atomic force microscopy, as well as x-ray diffraction and x-ray absorption spectroscopy. The Fe-partial phonon density of states (PDOS) was obtained from nuclear inelastic scattering. The PDOS of the film was investigated in the temperature range of 296 K down to 11 K and shows an excellent agreement with the ab initio calculations. In the PDOS of the nanorods, a shift in the number of states in the main features and an additional vibrational mode at 20 meV are observed. While the first effect can fully be explained by the specific orientation of the $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}$ unit cell on the Si(110) surface, the second effect is attributed to the formation of an $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}$ interlayer at the $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Fe}{\mathrm{Si}}_{2}/\mathrm{Si}$ interface. Furthermore, the thermoelastic properties of the film show a harmonic behavior in the investigated temperature range. For the nanorods, no significant deviation from the film is observed, except for a small decrease of the sound velocity.

Mechanical, Modal and Harmonic Behavior Analysis of Jute and Hemp Fiber Reinforced Polymer Composite

ABSTRACT In this study, the dynamic structural and mechanical properties of the polymer composite with natural fiber reinforcement have been investigated experimentally and numerically. First of all, three different types, one-, three- and five-layered jute-epoxy and hemp-epoxy laminated composite, have been manufactured using the hand lay-up method. The tensile strength, bending strength and shear strength of the fabricated composite material have been investigated experimentally using Universal Testing Machine. The density is measured using a density measurement kit using Archimedes principle. Further, frequency and damping factors are also investigated using a vibration test setup. Later on, the numerical model is developed in finite element-based software ANSYS. Different natural frequency modes and corresponding damping factors have been investigated numerically. The mechanical and structural characteristics obtained experimentally and numerically are analyzed and discussed in detail. From the investigation, it is found that the hemp-epoxy composite has a greater strength and stiffness compared to the jute-epoxy composite, irrespective of the number of fiber layers used. Further, it is also found that with the increase in fiber layers or fiber percentage in the composite, the strength and stiffness of the fabricated composite increase significantly.

Evolutionary Hypothesis in Cell Cycle of Breast Cancer Patients: Mosaic Phases in Single Cancer Cells

Introduction: Cell cycle shapes the initiation, progression and therapeutic approaches of neoplasms. An uncontrolled cell proliferation and growth are the key characteristics of either malignant or benign tumors. The programmed check points control the transition of phases through the related barriers. Therefore, balancing the carcinogenic processes may inhibit progression and facilitate a targeted-base therapy.
 Methods: The present study is performed in interphase. Detection of the Mosaic Phases (MPs) by Fluorescence In Situ Hybridization was confirmed by assaying the protein expression (PE) including immunofluorescence and flow cytometry.
 Results: The novel hypothesis reflects the presence of dual and/or multi-phases, as minor clones in single cells of breast cancer (BC) patients. This finding led to initiate a model with applicable ratio values and different MPs including G1/S, S/G2 and G1/S/G2, accompanied by normal phases (G1, S, G2). The remarkable harmonic behaviors between signal copy numbers and the corresponding PE, dual- and triple- co-expression between different cyclins combination including E/B1 and D1/E/B1 and the other involved proteins were observed. The ratio of gain to normal signals appeared to be a good prognosis for chromosome 1, but better survival was significantly obtained for this ratio in chromosome 3
 Conclusion: The predisposing-diagnostic-predictive-prognostic-preventive panels may lead to innovate the CDKs inhibitor-based therapy by considering the MPs Model; and may also be considered for clinical classification, in BC and other cancers.

Ballistic performance of novel design of bulletproof plates inspired by biomimetic approaches

AbstractMetal and polymer matrix composite materials are preferred in bulletproof applications due to their high‐impact resistance and lightness. Personal/demand‐specific designs that have become possible with the developing additive manufacturing technologies have brought a new perspective to armor technologies. At the same time, parts with complex structures designed with biomimetic approaches can be easily manufactured with additive manufacturing. In this study, biomimetic armors obtained from standard Carbon fiber reinforced polymer (CFRP) and Inconel 718 materials were compared with traditional armor structures. Within the scope of the study, 9 × 19 mm2 parabellum and 7.62 mm NATO bullets were impacted at 275 m/s and 600 m/s speeds on biomimetic and conventional armor consisting of three and five layers. Bullet velocities during impact, deformation of bullets, deformation of armor, and harmonic behavior are discussed. The results obtained were also used to calculate the damped impact energies. In the study, it was determined that biomimetic plates could absorb 22%–38% more impact energy. It has been determined that CFRP materials can absorb 45% more impact energy compared to Inconel 718.

Fitting Procedure to Reconstruct the Size Distribution and the Concentration of Silver Colloidal Nanoparticles from UV-Vis Spectra.

In this work, a complete fitting procedure of UV-Vis spectra of silver nanoparticles in colloidal solutions is reported. The fitting function, based on the Beer–Lambert law, Mie theory, and log-normal probability distribution of nanoparticles’ sizes, is developed and confirmed by 33 different independent measurements. In order to validate the accuracy of the function’s behavior on different spectra, freely accessible measurements were used, proving that the fitting function works independently of the method of their production—laser or chemical synthesis of nanoparticles. The developed fitting function is, to the best of our knowledge, novel and not based on any conventional spectral analysis approaches like the Mie–Gans procedure. Furthermore, since fitted parameters are all physical, it allows determination of the mode diameter of nanoparticles as well as the standard deviation of the log-normal distribution of sizes. It enables the reconstruction of size distribution of nanoparticles in colloidal solution. Step-by-step derivation of the fitting function is provided with a physical explanation of all parameters. The importance of Lorentzian dependence emerging at the core of Beer–Lambert law is physically discussed and linked to harmonic oscillator behavior of localized surface plasmon resonance of silver nanoparticles in a colloidal solution. Size distribution reconstruction from fitted parameters according to a log-normal distribution function is provided and a concentration calculation is presented.

Non-characteristic harmonics in modular multilevel converters—An analytical approach

This paper analyzes the harmonic content of the arm currents and voltages of the modular multilevel converter (MMC) by using the dynamic phasor (DP) theory. DP modeling of the MMC facilitates a study without relying on simplifying assumptions on the harmonic content of the currents and voltages. In doing so, the DP-MMC model used in this paper reveals generalized conditions under which non-characteristic harmonics can exist. These conditions offer a detailed insight into the transient behavior of harmonics in the MMC. An open-loop DP model of the MMC is developed, which has the harmonics of the arm currents and voltages as independent state variables. The linearized state-space matrices of the DP model are assessed under different grounding options at the ac side of the MMC, and the relationship between characteristic and non-characteristic harmonics of the MMC voltages and currents is discussed.

Evolution of optical harmonic generation near bound-states in the continuum in hybrid plasmonic-photonic structures.

We investigate the nonlinear optical harmonic generation behaviors near the bound-states in the continuum (BICs) in hybrid plasmonic-photonic structures. The hybrid structures are designed to consist of a plasmonic grating covered with a nonlinear dielectric waveguide layer, which support two distinct groups of BICs, i.e. the symmetry-protected BICs and Friedrich-Wintgen BICs. The evolution of second- and third-harmonic generation (SHG and THG) near the two groups of BICs was studied. The high dependence of nonlinear response on the local field distribution and tensor components of susceptibility of nonlinear materials was determined. Especially, there exists optimized angles of incidence for efficient SHG and THG response due to the interaction of photonic and plasmonic modes. The results are important to understand the nonlinear response behaviors in hybrid plasmonic-photonic structures and to design the nonlinear photonic devices.

An Idiom of Melodic-Harmonic Divorce

Within the stratified harmonic behavior known as melodic-harmonic divorce, this paper identifies a gesture repeated idiomatically across rock repertory. Dubbed “sub-circle” motion, this idiom is specifically a form of syntax divorce wherein a melodic layer unfolds in a way consonant with and suggestive of circle-of-fifths root motion (+P4) between two accompanying major chords; however, the harmonic layer’s root instead moves up by a minor third (+m3), creating a stratified dissonance, or divorce. The paper then identifies a standard set of paradigms—specific transpositional instances of the idiom—and catalogues numerous examples of their use in rock music. One paradigm, V-".fn_flat('')."VIIadd9, is the subject of special analytic and historical inquiry, due to its proliferation as a deceptive cadence in the late twentieth century. This previously untheorized cadence is the most prominent instance of the sub-circle idiom.

Universal anharmonic potential energy surfaces for XY2-type molecules

An approach to generate anharmonic potential energy surfaces for both linear and bent XY2-type molecules from their equilibrium geometries, Hessians, and total atomization energies alone is presented. Two key features of the potential energy surfaces are that (a) they reproduce the harmonic behavior around the equilibrium geometries exactly and (b) they have the correct limiting behavior with respect to total bond dissociation. The potentials are constructed from two diatomic potentials, for which both the Morse or Varshni potentials are tested, and a triatomic potential, for which modified forms of the Anderson-n potential are tested. Potential energy surfaces for several linear and bent molecules are constructed from ab initio data, and the third-order derivatives of these surfaces at their equilibrium geometries are compared to the results of finite difference computations. For bent molecules, the vibrational spectra predicted by vibrational configuration interaction calculations on these surfaces are compared to experiment. A modified version of the Anderson-n potential, in combination with the Varshni potential, is demonstrated to predict vibrational frequencies associated with bond angle bending an average of 20 cm−1 below the harmonic oscillator approximation and with a fourfold reduction in the root-mean-square deviation from experiment compared to the harmonic oscillator approximation.

Multimode Representation of the Magnetic Field for the Analysis of the Nonlinear Behavior of Solar Activity as a Driver of Space Weather

Estimating and predicting space weather is important to the space industry and space missions. The driver of space weather, especially near the Earth, is solar activity, the study of which is an important task. In particular, there is a direction of problems based on models of solar magnetic field generation that require research. In our work, we build a nonlinear dynamic system of equations that describes the behavior of the solar magnetic field harmonics based on the alpha-omega dynamo model. We found that, at the beginning of the magnetic field generation process, when the dynamo number significantly exceeds the threshold, the most rapidly growing waves are in the lead. Then, over time, these waves stop growing quite quickly. In this case, the initially slowly increasing harmonics of the magnetic field become the leaders, which then make the main contribution to the process of magnetic field generation.

Enhancement of power quality issues for a hybrid AC/DC microgrid based on optimization methods

The purpose of this paper is to study the harmonic behavior of hybrid microgrids (MGs). To achieve the desired goal, a modified active power filter (MAPF) and a power filter compensator kit (PFCK) modules have been used to improve the harmonics of the AC part of the system. The main challenge and feature of this research is the optimization of MAPF and PFCK controller gain coefficients hierarchical, using Harris hawk optimization (HHO), grasshopper optimization algorithm (GOA), artificial bee colony (ABC), and differential evolution (DE), respectively. Following, this technique was applied in the three control loops including, voltage and current harmonics, and system controller error to reduce the range of the mentioned harmonics to the permissible range. The method will be interesting considering that the PI and PID tuning is based on parallel feed-forward. The programmed objective functions include the three components current THD, voltage THD and controller error hierarchically. From the point of view of the MGs hierarchical control, the method presented in this study will be implemented in the second level of hierarchical control. In order to improve the operation of the DC part of the grid, a boost converter module (BCM) has been introduced in the form of a new synchronization scheme. The output of the simulation shows the reduction of the harmonic amplitude of the system by the mentioned modules.

Fuzzy gain Scheduled PID Controller for Power Quality Enhancement in Grid Connected Hybrid Solar PV-PEMFC Energy System

Power quality improvement is inevitable due to the presence of power converters and non-linear loads in grid connected renewable based hybrid energy system (HES). The harmonics introduced by the distributed energy systems may lead to output voltage distortion andequipment failure which may lead to system losses. It may also cause for direct and indirecteconomic impacts. Development of active filter, passive filter and hybrid filter for harmonics mitigation would be an expensive solutions. Therefore, various DC/AC converter switchingschemes are proposed for power quality improvements in grid connected Solar Photovoltaic(PV) and fuel cell based HES. Initially, Solar PV and Proton Exchange Membrane Fuel cell (PEMFC) are modeled using MATLAB/Simulink. Further the harmonic behavior withProportional plus Integral (PI), Proportional plus Integral plus Derivative (PID) and Fuzzygain scheduled PID controllers are demonstrated using Pulse Width Modulator (PWM).Converter output voltage waveform, frequency spectrum and total harmonics distortion (THD) values at the Point of Common Coupling (PCC) have witnessed that the fuzzy gain scheduled PID controller suppresses the voltage distortions completely. It also yields 4 percentage THD value which satisfies the harmonic level recommended by IEEE 519 standard. Comparative analysis shows that the fuzzy gain scheduled PID control scheme exhibits superior performance than the traditional PI and PID controllers. Therefore, it is identified as an effective control scheme for power quality improvement in hybrid renewable energy system.

Scattering analysis of linear and nonlinear symmetric Lamb wave at cracks in plates

ABSTRACT This paper presents a detailed study on detecting defects in isotropic plates by studying scattering analysis of first and second harmonics of symmetric Lamb wave (S0 ) at cracks in aluminium plates induced by Contact Acoustic Nonlinearity (CAN) using experimental and 3D Finite Element (FE) simulation approaches. In this study, a set of models with different crack sizes and orientations are studied. The effects of crack size and crack orientation on scattering behaviour of first and second harmonics of Lamb waves are investigated . The results show that the Scattering Directivity Pattern (SDP) of Lamb wave around the cracks is significantly influenced by crack size and crack orientation. It is also shown that the largest amplitude of scattered S0 wave is acquired from forward scattering waves for linear waves while the largest amplitude of scattered S0 Lamb wave is obtained from backward scattering waves for nonlinear waves. Therefore, it is expected that pulse-echo sensor configuration enhances nonlinear wave damage detection while pitch-catch configuration may suit better when linear wave is used. It is shown that selecting proper propagation direction for incident wave and proper geometry and angle for monitoring points are the key factors to achieve successful damage detection in isotropic plates.