Periodic Sequence Research Articles

Power leakage minimization in time‐modulated linear antenna array with optimized switching strategies employing modified harmony search algorithm

Time-modulated linear antenna array (TMLAA) with periodic time modulation of antenna elements radiates infinite inevitable harmonic beams. The infinite harmonic sideband radiation is a wastage of power unless the power is exploited. This paper aims to minimize inevitable power wastage in the harmonic beams radiated from TMLAA by employing an optimized periodic timing sequence. The optimization of the timing sequence is conducted employing harmony search (HS) to suppress the power wastage, However, conventional HS achieves an acceptable sidelobe level (SLL) below – 30 dB. Nevertheless, a modified harmony search algorithm (MHSA) is proposed to attain more power in the desired fundamental beam. The algorithm is validated using an array of 4-, 10-, and 16-element uniform half-wavelength spacing TMLAA. The optimization is conducted on the ON and OFF time instants and the real current of the elements. The simulation results exhibit that HS and MHSA perform potentially alike to suppress the SLL of fundamental below –30 dB. However, the further suppression of the sideband levels employing MHSA justifies the modification proposed in this work. The MHSA performance in terms of radiation parameters is compared with the HS and also with previous works to show the potentiality of the modification.

Micro–Macro Changepoint Inference for Periodic Data Sequences

Existing changepoint approaches consider changepoints to occur linearly in time; one changepoint happens after another and they are not linked. However, data processes may have regularly occurring changepoints, for example, a yearly increase in sales of ice-cream on the first hot weekend. Using linear changepoint approaches here will miss more global features such as a decrease in sales of ice-cream due to other product availability. Being able to tease these global changepoint features from the more local (periodic) ones is beneficial for inference. We propose a periodic changepoint model to model this behavior using a mixture of a periodic and linear time perspective. Built around a Reversible Jump Markov chain Monte Carlo sampler, the Bayesian framework is used to study the local (periodic) changepoint behavior. To identify the optimal global changepoint positions we integrate the local changepoint model into the pruned exact linear time (PELT) search algorithm. We demonstrate that the method detects both local and global changepoints with high accuracy on simulated and motivating applications that share periodic behavior. Due to the micro–macro nature of the analysis, visualization of the results can be challenging. We additionally provide a unique perspective for changepoint visualizations in these data sequences. Supplementary Materials for this article are available online.

Interplay between quantum diffusion and localization in the atom-optics kicked rotor.

Atom-optics kicked rotor represents an experimentally reliable version of the paradigmatic quantum kicked rotor system. In this system, a periodic sequence of kicks are imparted to the cold atomic cloud. After a short initial diffusive phase the cloud settles down to a stationary state due to the onset of dynamical localization. In this paper, to explore the interplay between localized and diffusive phases, we experimentally implement a modification to this system in which the sign of the kick sequence is flipped after every M kicks. This is achieved in our experiment by allowing free evolution for half the Talbot time after every M kicks. Depending on the value of M, this modified system displays a combination of enhanced diffusion followed by asymptotic localization. This is explained as resulting from two competing processes-localization induced by standard kicked rotor type kicks, and diffusion induced by the half Talbot time evolution. The experimental and numerical simulations agree with one another. The evolving states display localized but nonexponential wave function profiles. This provides another route to quantum control in the kicked rotor class of systems.

Within- and between-subject consistency of perceptual segmentation in periodic noise: A combined behavioral tapping and EEG study.

It is remarkable that human listeners can perceive periodicity in noise, as the isochronous repetition of a particular noise segment is not accompanied by salient physical cues in the acoustic signal. Previous research suggested that listeners rely on short temporally local and idiosyncratic features to perceptually segment periodic noise sequences. The present study sought to test this assumption by disentangling consistency of perceptual segmentation within and between listeners. Presented periodic noise sequences either consisted of seamless repetitions of a 500-ms segment or of repetitions of a 200-ms segment that were interleaved with 300-ms portions of random noise. Both within- and between-subject consistency was stronger for interleaved (compared with seamless) periodic sequences. The increased consistency likely resulted from reduced temporal jitter of potential features used for perceptual segmentation when the recurring segment was shorter and occurred interleaved with random noise. These results support the notion that perceptual segmentation of periodic noise relies on subtle temporally local features. However, the finding that some specific noise sequences were segmented more consistently across listeners than others challenges the assumption that the features are necessarily idiosyncratic. Instead, in some specific noise samples, a preference for certain spectral features is shared between individuals.

Combination of roots and boolean operations: An application to state complexity

Operations on regular languages that commute with any inverse alphabetic morphism are called 1-uniform transformations. In a previous work we have shown that these operations are encoded by operations on automata, called modifiers, that can be described in terms of functions acting on monoids of transformations. We study the special case where these functions are morphisms and show that the encoded operations are compositions of roots and boolean operations. We first show that there is a bijection between these operations and subsets of eventually periodic sequences of boolean values. We then deduce a tight bound for the state complexity of these operations.

First-photon target detection: Beating Nair's pure-loss performance limit

In 2011, Nair published a no-go theorem for quantum radar target detection [Phys. Rev. A {\bf 84}, 032312 (2011)]. He showed, under fairly general assumptions, that a coherent-state radar's error probability was within a factor of two of the best possible quantum performance for the pure-loss (no background radiation) channel whose roundtrip radar-to-target-to-radar transmissivity $\kappa$ satisfies $\kappa \ll 1$. We introduce first-photon radars (FPRs) to circumvent and beat Nair's performance limit. FPRs transmit a periodic sequence of pulses, each containing $N_S$ photons on average, and perform ideal direct detection (photon counting at unit quantum efficiency and no dark counts) on the returned radiation from each transmission until at least one photon has been detected or a pre-set maximum of $M$ pulses has been transmitted. They decide a target is present if and only if they detect one or more photons. We consider both quantum (each transmitted pulse is a number state) and classical (each transmitted pulse is a coherent state) FPRs, and we show that their error-probability exponents are nearly identical when $\kappa \ll 1$. With the additional assumption that $\kappa N_S \ll 1$, we find that their advantage in error-probability exponent over Nair's performance limit grows to 3 dB as $M \rightarrow \infty$. However, because FPRs' pulse-repetition period must exceed the radar-to-target-to-radar propagation delay, their use in standoff sensing of moving targets will likely employ $\kappa N_S \sim 1$ and $M \sim 10$ and achieve ~2 dB advantage. Our work constitutes a new no-go theorem for quantum radar target detection.

ASSESSMENT OF ZOOPLANKTON DIVERSITY OF NEW CONSTRUCTED RESERVOIR BISNOOR PACHDHAR RESERVOIR IN DISTRICT, BETUL, MP

The status of healthiness of any freshwater ecosystem is basically depends on the diversity and density of zooplankton inhabiting the freshwater resources. Zooplanktons are considered as fundamental source for primary consumer in any aquatic environment. Which influence greatest scope in decisive the total productivity of freshwater body. The present study is attempted to the qualitative and quantitative distribution of zooplankton in different sites of Bisnoor Pachdhar reservoir. The study was carried out seasonally from July 2020 to June 2021. The whole assessment was divided into four major seasons viz monsoon, post monsoon, winter and summer. The compilation of the zooplankton samples and their qualitative and quantitative was through followed the standard procedures of limnological analysis. During the study period sequence of dominant groups Rotifera > Copepoda > Protozoa > Cladocera > Ostracoda was observed at dam site and mid site of all season. On another hand at tail end site major dominant group was Copepoda > Protozoa > Cladocera > Rotifera > Ostracoda noted during monsoon, post monsoon and winter and during summer the order of dominant group Copepoda > Rotifera > Protozoa > Ostracoda > Cladocera was recorded in Bisnoor Pachdhar reservoir.

Density matrix theory of the charge and current wave formation at fast pulsed photoemission through a double quantum well

Within the framework of the density matrix method, general formulas are obtained that are convenient for describing fast pulsed photoemission that occurs in a time less than or on the order of the times of relaxation processes inside the photocathode. Expressions for the elements of the density matrix are found by solving the kinetic equation that takes into account the alternating electromagnetic field of light pumping and inelastic scattering of electrons. The derived formulas are applied for the numerical-analytical study of a one-dimensional model of wavelike spatiotemporal modulation of a photoelectron pulse of suitable duration during its passage through a double-well quantum-well heterostructure deposited on a volumetric planar photocathode. This modulation is a quantum beat that occurs as a result of excitation and subsequent slow oscillatory decay of the superposition of the doublet of quasistationary states of the heterostructure. It is possible to provide prolongation of generation and even amplification of waves of charge density and current density of photoelectrons when the photocathode is exposed to a periodic sequence of light pulses.

Increasing the amplitude of ultrashort microwave pulses in a passive mode-locked oscillator by the method of double nonlinear filtering

We show the possibility of increasing the amplitude of ultrashort microwave pulses in a passive mode-locked oscillator in a circuit containing a chain of traveling wave tubes (TWTs) one of which operates in the amplification regime and the other two in the nonlinear Kompfner suppression regime. An increase in the number of nonlinear filtering stages makes it possible to enhance the filtering threshold level, below which low background noise is suppressed, while an almost complete transparency is maintained for peak amplitudes of the pulse signal. As a result, with an increase in the length of the amplifier, a linear growth in the peak amplitude of microwave pulses takes place because of the commutative extraction of energy from different electron fractions, along which the pulse is shifted due to the difference in its group velocity from the translational velocity of the particles. With an optimal selection of the parameters of the absorbers, the peak amplitude of the generated periodic sequence of ultrashort pulses can exceed the amplitude of stationary generation by more than an order of magnitude for given parameters of the TWT like current, voltage, and coupling impedance.

КОЛЕБАНИЯ КРУГОВОЙ ТРЕХСЛОЙНОЙ СТУПЕНЧАТОЙ ПЛАСТИНЫ ПРИ УДАРНОМ ПЕРИОДИЧЕСКОМ ВОЗДЕЙСТВИИ

Forced oscillations of a three-layer circular plate with step-variable thickness of the outer layers are analyzed. The deformation of the plate is described with the zig-zag theory. In thin border layers of plate Kirchhoff’s hypotheses are valid. In a relatively thick in thickness medium layer Timoshenko’s hypothesis on the straightness and incompressibility of the deformed normal is fulfilled. The equations of motion are derived from Hamilton’s variational principle. A special case of exposure is considered: periodic sequence of strokes with constant intensity. The problem is reduced to finding three required functions in each section, deflection, shear and radial displacement of the median plane of the filler. The solution is presented as a sum of quasi-static and dynamic components of the unknown displacements. Numerical results of the obtained solution are presented. The influence of the impact stress on the oscillatory character is analyzed.

TESS Hunt for Young and Maturing Exoplanets (THYME). VII. Membership, Rotation, and Lithium in the Young Cluster Group-X and a New Young Exoplanet

The public, all-sky surveys Gaia and TESS provide the ability to identify new young associations and determine their ages. These associations enable study of planetary evolution by providing new opportunities to discover young exoplanets. A young association was recently identified by Tang et al. and Fürnkranz et al. using astrometry from Gaia (called “Group-X” by the former). In this work, we investigate the age and membership of this association, and we validate the exoplanet TOI 2048 b, which was identified to transit a young, late G dwarf in Group-X using photometry from TESS. We first identified new candidate members of Group-X using Gaia EDR3 data. To infer the age of the association, we measured rotation periods for candidate members using TESS data. The clear color–period sequence indicates that the association is the same age as the 300 ± 50 Myr old NGC 3532. We obtained optical spectra for candidate members that show lithium absorption consistent with this young age. Further, we serendipitously identify a new, small association nearby Group-X, which we call MELANGE-2. Lastly, we statistically validate TOI 2048 b, which is a 2.1 ± 0.2 R ⊕ radius planet on a 13.8-day orbit around its 300 Myr old host star.

Optimal maintenance period and maintenance sequence planning under imperfect maintenance

AbstractMaintenance is essential for today's equipment or systems and maintenance costs account for a significant portion of the overall expenditure of devices. Maintenance period optimization and maintenance sequence planning are primary aspects of maintainability. To this end, this paper proposes an approach for maintenance period optimization and maintenance sequence planning, with the consideration of imperfect maintenance. A model of the total maintenance cost per unit time is set up, and the optimal time period for preventive maintenance is calculated. In addition, a new index is created to evaluate the maintenance efficiency of optimal maintenance sequences in different scenarios. The performance of the proposed method is validated by a maintenance sequence optimization and maintenance sequence planning of baggage handling systems. The results indicate that the proposed method is efficient and contributes to maintenance cost savings.

Triskeles and Symmetries of Mean Global Sea-Level Pressure

The evolution of mean sea-level atmospheric pressure since 1850 is analyzed using iterative singular spectrum analysis. Maps of the main components (the trends) reveal striking symmetries of order 3 and 4. The Northern Hemisphere (NH) displays a set of three positive features, forming an almost perfect equilateral triangle. The Southern Hemisphere (SH) displays a set of three positive features arranged as an isosceles triangle, with a possible fourth (weaker) feature. This geometry can be modeled as the Taylor–Couette flow of mode 3 (NH) or 4 (SH). The remarkable regularity and three-order symmetry of the NH triskeles occurs despite the lack of cylindrical symmetry of the northern continents. The stronger intensity and larger size of features in the SH is linked to the presence of the annular Antarctic Oscillation (AAO), which monitors the periodic reinforcement and weakening of the circumpolar vortex; it is a stationary mode. These components represent 70% of the variance in total pressure since 1850 and are stable in both time and space. In the remaining 30% of the variance, we have extracted quasi-periodical components with periods larger than 1 year (2% of the variance) and a harmonic sequence of the 1-year period (20% of the variance).

Solitons in Overdamped Brownian Dynamics.

Solitons are commonly known as waves that propagate without dispersion. Here, we show that they can occur for driven overdamped Brownian dynamics of hard spheres in periodic potentials at high densities. The solitons manifest themselves as periodic sequences of different assemblies of particles moving in the limit of zero noise, where transport of single particles is not possible. They give rise to particle currents at even low temperature that appear in bandlike structures around certain hard-sphere diameters. At high temperatures, the bandlike structures are washed out by the noise, but the particle transport is still dominated by the solitons. All these predicted features should occur in a broad class of periodic systems and are amenable to experimental tests.

Angular insensitive nonreciprocal ultrawide band absorption in plasma-embedded photonic crystals designed with improved particle swarm optimization algorithm

Using an improved particle swarm optimization algorithm (IPSO) to drive a transfer matrix method, a nonreciprocal absorber with an ultrawide absorption bandwidth and angular insensitivity is realized in plasma-embedded photonic crystals arranged in a structure composed of periodic and quasi-periodic sequences on a normalized scale. The effective dielectric function, which determines the absorption of the plasma, is subject to the basic parameters of the plasma, causing the absorption of the proposed absorber to be easily modulated by these parameters. Compared with other quasi-periodic sequences, the Octonacci sequence is superior both in relative bandwidth and absolute bandwidth. Under further optimization using IPSO with 14 parameters set to be optimized, the absorption characteristics of the proposed structure with different numbers of layers of the smallest structure unit N are shown and discussed. IPSO is also used to address angular insensitive nonreciprocal ultrawide bandwidth absorption, and the optimized result shows excellent unidirectional absorbability and angular insensitivity of the proposed structure. The impacts of the sequence number of quasi-periodic sequence M and collision frequency of plasma1 ν 1 to absorption in the angle domain and frequency domain are investigated. Additionally, the impedance match theory and the interference field theory are introduced to express the findings of the algorithm.

Lienard chaotic system based on Duffing and the Sinc function for weak signals detection

This article presents a modified Duffing system based on Lienards Theorem and the integral of Melnikov, the first is used to propose the interpolation Sinc as a non-linear damping function and the second is used to assure an asymptotically stable limit cycle. The Sin-Duffing system is driven into chaos by using its corresponding bifurcation diagram, Lyapunov exponents, and the Theory of Melnikov. Furthermore, the system is placed in a critical state which produced chaotic and periodic sequences, driving it into a regimen of intermittence between chaos and the self-sustained oscillations near the stable limit cycle. Intermittence is achieved by searching and tuning all involved parameters when a very systematic procedure is used. Also, such a regimen is presented here as a useful mechanism to estimate the frequency of a very low weak signal for detection applications. The latest is made possible because the system capabilities to distinguish the intermittent periods were strengthened by a new method based on Melnikovs function that only depends on the most influential parameter in the type-Lienard system. The complete system formed by the new Sinc-Duffing oscillator showed higher sensitivity compere to other chaotic systems such as the traditional Duffing or the Van der Pol-Duffing for weak signal detection with a signal-to-noise ratio down to -70 dB.

The atlas of mitochondrial genetic diversity for Western Palaearctic butterflies

AbstractMotivationButterflies represent a model in biology and a flagship group for invertebrate conservation. We provide four new resources for the Western Palaearctic butterflies: (1) an updated checklist comprising 552 species; (2) a curated dataset of 32,126 mitochondrial cytochrome c oxidase subunit I (COI) sequences for 532 species, including a de novo reference library for the Maghreb (Morocco, northern Algeria and Tunisia) and Macaronesia (Azores, Madeira and Canary Islands); (3) seven indexes of intraspecific genetic variation (IGV): observed and expected number of haplotypes, haplotype and nucleotide diversity, two fixation indexes and maximum p‐distance; and (4) species‐level maps illustrating the distribution of COI variability and haplotype networks. The updated checklist will be fundamental for any application dealing with butterfly diversity in the Western Palaearctic. The IGV indexes provide measures for genetic polymorphism and spatial structure and represent proxies for dispersal capacity. These resources will facilitate comparative studies of macrogenetics, foster integrative taxonomy and aid conservation strategies.Main types of variables containedA complete species checklist in table format, 32,126 mitochondrial DNA barcodes provided with metadata (species membership, WGS84 coordinates and sequence length) and a book in PDF format, including the IGV atlas and indexes, are provided.Spatial location and grainThe checklist encompasses Europe up to the Urals in the east, north Macaronesia (the Azores, Madeira and the Canary Islands) and the Maghreb (Morocco, northern Algeria and Tunisia). COI sequences have been retained in the geographical interval of −31.3 to 67.5° of longitude and 27.5–71.2° of latitude.Time period and grainCOI sequences originate from studies published between 1998 and 2022 and from de novo sequencing of 2541 specimens done between 2007 and 2022.Major taxa and level of measurementButterflies (Lepidoptera: Papilionoidea), analysed from individual to species level.Software formatData and functions to manage the dataset are provided in the iodatabase R package (https://github.com/leondap/iodatabase) and in Dryad (https://doi.org/10.5061/dryad.9w0vt4bjj).

Development of a Generator of a Periodic Sequence of Ultrashort 8-mm Electromagnetic Pulses Based on the “Saturn” Accelerator with Two Coaxial Emitting and Absorbing Electron Beams

Development of a Generator of a Periodic Sequence of Ultrashort 8-mm Electromagnetic Pulses Based on the “Saturn” Accelerator with Two Coaxial Emitting and Absorbing Electron Beams

A New Approach to Determine the Minimal Polynomials of Binary Modified de Bruijn Sequences

A binary modified de Bruijn sequence is an infinite and periodic binary sequence derived by removing a zero from the longest run of zeros in a binary de Bruijn sequence. The minimal polynomial of the modified sequence is its unique least-degree characteristic polynomial. Leveraging a recent characterization, we devise a novel general approach to determine the minimal polynomial. We translate the characterization into a problem of identifying a Hamiltonian cycle in a specially constructed graph. The graph is isomorphic to the modified de Bruijn–Good graph. Along the way, we demonstrate the usefulness of some computational tools from the cycle joining method in the modified setup.

Counteracting the dynamic degradation of high-dimensional digital chaotic systems via a stochastic jump mechanism

To analyze the periodic distribution and state-mapping structures of high-dimensional digital chaotic systems in fixed-point arithmetic domain. A chaotic cycle-finding algorithm (CCFA) can be designed to precisely calculate the period length of the orbit of digital chaos under different finite calculation accuracy. Furthermore, to test the versatility and effectiveness of our proposed algorithm, the periodic distribution and security of the digital Sprott D system are analyzed in detail. Numerical simulation results show that the chaotic system have potential security risks, such as short period and low sequence complexity. In addition, we put forward a new resistance method based on automatic cycle detection and random jump of chaotic trajectories for the objective of enhancing the dynamical properties of high-dimensional digital chaotic systems. This scheme can construct a new chaotic model with many desirable properties, such as long period, high state-space utilization, low autocorrelation, and good ergodicity.