Irregular Modulation Research Articles

Irregular RIS Pattern Array-Based Index Modulation for Next-Generation RIS Communication

Irregular RIS Pattern Array-Based Index Modulation for Next-Generation RIS Communication

Call for Your Life: Acoustic Structure and Age‐Sex Differences in Distress Calls of Red‐Necked Nightjars

ABSTRACTPredatory interactions result in strong selection pressures acting on multiple aspects of animal behaviour. Anti‐predator strategies are therefore common in most animals, typically signalling at various stages of a predation event. Many species of caprimulgids perform conspicuous anti‐predator displays, including stereotyped behaviours and vocal signals. Here, we described distress calls of red‐necked nightjars (Caprimulgus ruficollis), produced when birds are trapped and unable to escape during a predatory interaction. Distress calls are harsh, low‐frequency guttural vocalisations with irregular amplitude modulations. The age and sex of birds partially explained the acoustic variation observed, whereas size‐related morphological features were poor predictors of the acoustic structure. Age‐sex differences in distress calls may respond to physiological constraints associated with sexual dimorphism and/or developmental variation. Alternatively, directional selection associated with differential predation risk on each age‐sex class may have resulted in the observed differences in distress calls. The extremely deep voice and the harsh quality of distress calls fit the structure of aggressive signals and may resemble those produced by a larger animal. We propose that these calls serve as a last resort strategy to reduce post‐encounter risk of predation, either as a startling effect to facilitate escape or to attract other predators that could intimidate the captor.

A semantic segmentation scheme for night driving improved by irregular convolution.

In order to solve the poor performance of real-time semantic segmentation of night road conditions in video images due to insufficient light and motion blur, this study proposes a scheme: a fuzzy information complementation strategy based on generative models and a network that fuses different intermediate layer outputs to complement spatial semantics which also embeds irregular convolutional attention modules for fine extraction of motion target boundaries. First, DeblurGan is used to generate information to fix the lost semantics in the original image; then, the outputs of different intermediate layers are taken out, assigned different weight scaling factors, and fused; finally, the irregular convolutional attention with the best effect is selected. The scheme achieves Global Accuracy of 89.1% Mean and IOU 94.2% on the night driving dataset of this experiment, which exceeds the best performance of DeepLabv3 by 1.3 and 7.2%, and achieves an Accuracy of 83.0% on the small volume label (Moveable). The experimental results demonstrate that the solution can effectively cope with various problems faced by night driving and enhance the model's perception. It also provides a technical reference for the semantic segmentation problem of vehicles driving in the nighttime environment.

Low-complexity amplitude-division irregular QAM formats for short-reach unamplified coherent optical systems.

A low-complexity scheme is proposed to realize irregular uniform quadrature amplitude modulation (QAM) formats with Gray mapping, which are named amplitude-division irregular QAM (AD-Ir-QAM) formats. Compared to conventional probabilistic shaping (PS) with the Maxwell-Boltzmann (MB) distribution (PS-MB), irregular QAM formats show a smaller peak-to-average power (PAPR) and achieve a better performance in systems with the peak-power constraint. Compared with irregular QAM formats realized by PS (PS-Ir-QAM), AD-Ir-QAM formats realize a more flexible rate adaptation and have a lower implementation complexity. Experimental results obtained in an unamplified coherent optical system show that, at a generalized mutual information (GMI) of 4.5 bits/2D-symbol, AD-Ir-100QAM achieves gains of 2.1 and 0.5 dB in the power budget over PS-MB-100QAM and PS-Ir-100QAM, respectively.

An End-to-End Scheme for Learning Over Compressed Data Transmitted Through a Noisy Channel

Within the emerging area of goal-oriented communications, this paper introduces a novel end-to-end transmission scheme dedicated to learning over a noisy channel, under the constraint that no prior training dataset is available. In this scheme, the transmitter makes use of powerful Spherical Harmonic Transform and Irregular Hexagonal Quadratic Amplitude Modulation techniques, while the receiver relies on a Complex-Valued Neural Network (CVNN) so as to realize the learning task onto the received noisy data. As a main feature of the proposed scheme, the transmitter is fixed and does not depend on the source statistics, while the receiver is trained from a first data transmission phase, thus providing an efficient transmission-versus-learning approach under the considered constraint. The proposed transmission scheme may be adapted to a variety of learning problems, and the paper specifically investigates clustering and classification, two very common learning tasks. In the last part of the paper, the source/channel coding rate of the proposed transmission scheme is evaluated theoretically and from numerical simulations. This analysis shows a clear advantage in terms of coding rate of our scheme compared to conventional coding approaches, when targeting the same learning performance level.

MPPT Design for PV-Powered WPT System with Irregular Pulse Density Modulation

Electric vehicles (EVs) are well-known as environmentally friendly systems. Therefore, the demand for EVs is rapidly increasing every day, but for charging batteries of EVs eco-friendly electrical energy sources are needed. To use a clean energy source, this article proposes a wireless power transfer (WPT) system energized by photovoltaic panels. In this study, pulse density modulation technique controlled with incremental conductance algorithm is preferred in the WPT system for both transferring power from primary to secondary windings and for tracking maximum power point (MPP). The proposed system was tested with an experimental prototype and the results were presented. As a result, both 99.22% MPPT efficiency was obtained and power was transferred from primary to secondary with 90% efficiency.

Investigation of Vocal Bifurcations and Voice Patterns Induced by Asymmetry of Pathological Vocal Folds.

Vocal fold asymmetry creates irregular entrainments and modulations in voice, which may lead to rough perceptual quality. The presence of asymmetry can also cause mid-phonation bifurcations where a small change in the phonatory system causes a drastic change in vibration pattern, resulting in transitions in and out of rough voice. This study surveys sustained phonation recordings of speakers with the diagnoses of vocal fold polyp or unilateral vocal fold paralysis to investigate the resulting voice patterns. This retrospective study observed 71 sustained phonation recordings from 48 patients. Segments with distinctive signal patterns were identified within each recording with narrowband spectrogram and computer-assisted analysis of spectral peaks. Phonation segmentation yielded 240 segments across all the recordings. Five voice patterns were recognized: (regularly or irregularly) entrained, modulated, uncoupled, unstable, and pulsed. Thirty-six patients (75%) exhibited irregular patterns. No single irregular pattern lasted for the entire phonation and was always accompanied by at least one mid-phonation bifurcation. Durations of the irregular segments (M = 0.4 s) were significantly shorter than the segments with the regular pattern (M = 1.4 s). The results suggest that vocal fold pathology frequently introduces dynamic vibratory patterns that affect both the acoustic signals and perceptions. Due to these abnormalities, it is important for clinical voice assessment protocols, both perceptual and acoustic, to account for these possible bifurcations, irregular signal patterns, and their tendencies.

Irregular Autonomic Modulation Predicts Risky Drinking and Altered Ventromedial Prefrontal Cortex Response to Stress in Alcohol Use Disorder.

Autonomic dysfunction has been associated with risky drinking and alcohol use disorder (AUD). Although autonomic nervous system (ANS) activity has been attributed to the ventromedial prefrontal cortex (VmPFC)-limbic-striatal regions, the specific role of ANS disruption in AUD and its association with these regions remain unclear. Using functional magnetic resonance imaging (fMRI) and concurrent electrocardiogram (ECG), the current study examined neural correlates of ANS activity in AUD and its role in AUD pathology. Demographically matched 20 AUD patients and 20 social drinkers (SD) completed an fMRI task involving repeated exposure to stress, alcohol-cue and neutral-relaxing images in a block design. Based on the known VmPFC-limbic-striatal functions involved in emotions, reward and the ANS, we performed a regions of interest (ROI) analysis to examine the associations between ANS activity and neural responses in the VmPFC, amygdala, and ventral striatum. Across conditions, AUD patients showed significantly higher levels of overall heart rate (HR) and approximate entropy (ApEn) compared to SD (Ps < 0.05). In all participants, increased HR was associated with greater drinking volume (P < 0.05). In addition, higher ApEn levels were associated with greater drinking volume (P < 0.05) and decreased right VmPFC response to stress (P < 0.05). Our findings demonstrate ANS disruption in AUD indexed by high overall HR and ApEn. The association between ApEn and rVmPFC response suggests that ApEn may play a role in modulating drinking via interactions with neural regions of emotion regulation. These findings provide insight into patterns of ANS disruption and their relevance to AUD pathology.

Regimes identification of the viscous flow past an elliptic cylinder for Reynolds number up to 10000

In the present paper, the study of different regimes arising from the incompressible planar viscous flow past an elliptical cylinder is presented. In order to highlight the effect of the different parameters on the onset of the regimes, two different aspect ratios, 0.10 and 0.40, are considered and the angles of attack span from 0∘ to 90∘, while the Reynolds number is gradually increased from 100 to 10000. The analyses are focused on the lift force acting on the ellipse in order to identify the regime, with a consideration on the vorticity field patterns of the wake fields. The different regimes are investigated and the chaotic behaviour is established through different tools such as the Fourier spectra, phase maps and Poincaré sections. The investigation of the periodic regimes revealed several possible conditions in terms of lift time signal: monochromatic, non-monochromatic and sub-harmonic regimes. In addition, a quasi-periodic time behaviour with an underlying irregular amplitude modulation was also found among the test matrices performed. Increasing the Reynolds number the periodic regimes are lost, giving the place to chaotic behaviour. The numerical solutions are obtained through a vortex particle method called Diffused Vortex Hydrodynamics (DVH). Long time simulations have been carried out in order to guarantee the correct identification of the attained regime.

Bursting during intermittency route to thermoacoustic instability: Effects of slow-fast dynamics.

Intermittency observed prior to thermoacoustic instability is characterized by the occurrence of bursts of high-amplitude periodic oscillations (active state) amidst epochs of low-amplitude aperiodic fluctuations (rest state). Several model-based studies conjectured that bursting arises due to the underlying turbulence in the system. However, such intermittent bursts occur even in laminar and low-turbulence combustors, which cannot be explained by models based on turbulence. We assert that bursting in such combustors may arise due to the existence of subsystems with varying timescales of oscillations, thus forming slow-fast systems. Experiments were performed on a horizontal Rijke tube and the effect of slow-fast oscillations was studied by externally introducing low-frequency sinusoidal modulations in the control parameter. The induced bursts display an abrupt transition between the rest and the active states. The growth and decay patterns of such bursts show asymmetry due to delayed bifurcation caused by slow oscillations of the control parameter about the Hopf bifurcation point. Further, we develop a phenomenological model for the interaction between different subsystems of a thermoacoustic system by either coupling the slow and fast subsystems or by introducing noise in the absence of slow oscillations of the control parameter. We show that interaction between subsystems with different timescales leads to regular amplitude modulated bursting, while the presence of noise induces irregular amplitude modulations in the bursts. Thus, we speculate that bursting in laminar and low-turbulence systems occurs predominantly due to the interdependence between slow and fast oscillations, while bursting in high-turbulence systems is predominantly influenced by the underlying turbulence.

Optimization of Emission Waveform by Accelerated Particle Swarm Algorithm Based on Logarithmic Frequency Offset Mathematical Model

In this article, a novel technique is applied to achieve time-invariant spatial focusing performance for static and moving target by applying an irregular frequency modulation method to a frequency diverse array (FDA) waveform transmission system. The FDA radar can improve the anti-noise ability of the system by the means of concentrating the waveform energy on the required range or angle sector. However, the synthesized waveform has high sidelobes and is time-varying during the transmission waveform. In view of the above problems, a new waveform synthesis model of rang compensation frequency diverse array (TMRC-FDA) is established and the effect of parameter $$\varsigma$$ on the waveform synthesis is analyzed. A new accelerated particle swarm optimization algorithm is used to optimize the distribution of parameter $$\varsigma$$. The numerical simulation results show that the proposed TMRC-FDA waveform synthesis method achieves the goal of time invariance and reduces the waveform sidelobes. At the same time, it has better performance in terms of waveform focus compared to log-frequency offset FDA based on time-modulated and fixed parameters $$\varsigma$$.

Examples of hypergeometric twistor 𝒟-modules

We show that certain one-dimensional hypergeometric differential systems underlie objects of the category of irregular mixed Hodge modules, which was recently introduced by Sabbah, and compute the irregular Hodge filtration for them. We also provide a comparison theorem between two different types of Fourier-Laplace transformation for algebraic integrable twistor $\mathcal{D}$-modules.

Vocalizations, tadpole, and natural history of Crossodactylus werneri Pimenta, Cruz Caramaschi, 2014 (Anura: Hylodidae), with comments on distribution and intraspecific variation.

Crossodactylus werneri was described based on specimens collected in the 1970's at Parque Nacional do Itatiaia, being also reported for nearby localities. We collected specimens that we assigned to C. werneri, and recorded calls of the species during fieldworks at Serra das Cabras (Campinas, state of São Paulo). In this paper, we describe for the first time the vocalizations, tadpole, coloration in life, and comment on aspects of the natural history of C. werneri. Besides, the examination of specimens in zoological collections allowed us to extend the geographic range for this species. We also make remarks on morphological/chromatic variation and provide 16S rDNA sequences for the species. Adults were found along a slow-flowing streamlet with sandy/muddy bottom within a small fragment of secondary forest. Males called between sunset and first hours of the night. Advertisement call consisted of series of pulsed notes. Call duration lasted around 3 s, emitted at the highest rate of 17 calls per minute and six notes per second. Note duration lasted around 18 ms. Notes had poorly defined pulses (irregular and/or weak amplitude modulations along the note). The dominant frequency was about 3380 Hz. Territorial call had a long, well-defined pulsed portion followed by a higher-amplitude "squeak". The dominant frequency was around 3400 Hz. Tadpoles were essentially similar to those of other Crossodactylus species, except by not having nostril ornamentation. Our record of C. werneri in Serra das Cabras might be regarded a rediscovery of this species since C. werneri had not been recorded for more than 30 years until our first record of C. werneri in the field from 2011 and subsequent years. Our record is approximately 100 km west, and Mococa 200 km northwest, from Santo Antônio do Pinhal, the westernmost previous record for C. werneri up to date. Gene sequences (16S rRNA) give insights into the genetic divergence between C. werneri and some congeners.

Nonlinear asteroseismology: insight from amplitude and frequency modulations of oscillation modes in compact pulsators fromKeplerphotometry

Nonlinear mode interactions are difficult to observe from ground-based telescopes as the typical periods of the modulations induced by those nonlinear phenomena are on timescales of weeks, months, even years. The launch of space telescopes, e.g., Kepler , has tremendously changed the situation and shredded new light on this research field. We present results from Kepler photometry showing evidence that nonlinear interactions between modes occur in the two compact pulsators KIC 8626021, a DB white dwarf, and KIC 10139564, a short period hot B subdwarf. KIC 8626021 and KIC 10139564 had been monitored by Kepler in short-cadence for nearly two years and more than three years without interruption, respectively. By analyzing these high-quality photometric data, we found that the modes within the triplets induced by rotation clearly reveal different behaviors: their frequencies and amplitudes may exhibit either periodic or irregular modulations, or remain constant. These various behaviors of the amplitude and of the frequency modulations of the oscillation modes observed in these two stars are in good agreement with those predicted within the amplitude equation formalism in the case of the nonlinear resonant mode coupling mechanism.

KIC 2831097 – a 2-yr-orbital-period RR Lyrae binary candidate

Abstract We report the discovery of a new Kepler first-overtone RR Lyrae pulsator, KIC 2831097. The pulsation shows large, 0.1-d amplitude, systematic phase variations that can be interpreted as light traveltime effect caused by orbital motion in a binary system, superimposed on a linear pulsation-period decrease. The assumed eccentric (e = 0.47) orbit with the period of ≈2 yr is the shortest among the non-eclipsing RR Lyrae binary candidates. The binary model gives the lowest estimate for the mass of the companion of 8.4 M⊙, that places it among black hole candidates. Beside the first-overtone pulsation, numerous additional non-radial pulsation frequencies were also identified. We detected an ≈47-d Blazhko-like irregular light-curve modulation.

De-mystifying Diagrids: Expressive Structural System for Skyscrapers

The word “diagrid” is a blend of the words “diagonal” and “grid” and refers to a structural system that is single thickness in nature and gains its structural integrity through triangulation. Diagrid structural systems have enabled significant transformation in the design of tall buildings. Diagrids are unique in their ability to assume the entire lateral and gravity loading of towers up to at least 50 storeys in height, eliminating the need for traditional columns and cores. Even in super-tall towers, it is possible to reduce or eliminate dependence on the core in the top 15–30%, allowing for unique spatial opportunities.Diagrids have rendered a particular elegance and lightness to buildings through efficiency, geometry and form. While other contemporary structural systems such as megaframes and outriggers are typically repressed in the detailing of the façade and dependent building elements, diagrids are chosen to form the basis of the architectural expression of the building.This article presents a methodology for the design of diagrid structures based on the systematic analysis of major buildings constructed from 2004 to the present as documented in Ref. in 2014. The design of diagrid towers will be demonstrated through primary choices in module size, member type, node design, function of the core and the desired expression in the façade system. These translate into additional concerns of constructability and customized fabrication. Fire control systems impact the ability to architecturally expose or conceal the steel, leading to detailing decisions.This article also looks at more recent trends in construction, such as the move away from optimization through increase in irregular modules, the use of composite construction and the potential inclusion of cast nodes.

Linear Physical-Layer Network Coding and Information Combining for the &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$K$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-User Fading Multiple-Access Relay Network

We propose a new linear physical-layer network coding (LPNC) and information combining scheme for the $K$ -user fading multiple-access relay network (MARN), which consists of $K$ users, one relay, and one destination. The relay and the destination are connected by a rate-constraint wired or wireless backhaul. In the proposed scheme, the $K$ users transmit signals simultaneously. The relay and the destination receive the superimposed signals distorted by fading and noise. The relay reconstructs $L$ linear combinations of the $K$ users’ messages, referred to as $L$ network-coded (NC) messages, and forwards them to the destination. The destination then attempts to recover all $K$ users’ messages by combining its received signals and the NC messages obtained from the relay. We develop an explicit expression on the selection of the coefficients of the NC messages at the relay that minimizes the end-to-end error probability at a high signal-to-noise ratio. We develop a channel-coded LPNC scheme by using an irregular repeat-accumulate modulation code over GF( $q$ ). An iterative belief-propagation algorithm is employed to compute the NC messages at the relay, while a new algorithm is proposed for the information combining decoding at the destination. We demonstrate that our proposed scheme outperforms benchmark schemes significantly in both un-channel-coded and channel-coded MARNs.

Irregular matrix model with symmetry

We present an irregular matrix model which has and Virasoro symmetry. The irregular matrix model is obtained using the colliding limit of the Toda field theories and produces the inner product between irregular modules of symmetry. We evaluate the partition function using the flow equation which is the realization of Virasoro and symmetry.

Transient evolution of eigenmodes in dynamic cavities and time-varying media

In this paper, we investigate the perturbation of natural eigenmodes of dynamic cavities with boundaries moving at quasi-static speeds relative to the wave velocity. For an arbitrarily shaped source-free cavity, the amplitude of the irrotational mode is modeled as a damped harmonic oscillator with time-varying eigenfrequency, i.e., a parametric oscillator. It is found that the effect of the pure Doppler shift of the resonance frequencies of the eigenmodes is small at nonrelativistic speeds. However, it is known that any spectrum of eigenenergies that is perturbed by a space- and/or time-fluctuating medium can develop frequency shifts of arbitrary magnitude. By using a linear dynamic (time-dependent) shift for the cavity broad resonances, we find that Doppler-like large shifts result in a mere frequency modulation of the total (resultant) field amplitude, while nonuniform red or blue shift can create a hybrid amplitude and frequency modulation. Interestingly, the combined action of red and blue shifts of uniform magnitude can also create a hybrid modulation. If the angle between modal wave vector and stirrer speed is accounted for in the static (time-independent) shift, the resulting red and blue shifts lead to irregular hybrid modulations. This can occur even for regular perturbations in regular cavities. In addition, owing to the stochastic nature of mode-stirred cavities, the effect of random Doppler-like shifts is also investigated, leading to a Fokker-Planck equation whose diffusion coefficient shows quadratic dependence on the mode amplitude. Thus, the analysis of random perturbations offers an effective framework for observed instantaneous Doppler effects in closed electromagnetic environments. The mathematical framework obtained in terms of stochastic differential equations is useful to predict the nonstationary response of dynamic cavities with complicated or unknown boundary geometry.

A novel phase-sensitive scanning near-field optical microscope**Project supported by the National Natural Science Foundation of China (Grant Nos. 61177089, 61227014, and 60978047).

Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton (SPP) devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field optical microscope (SNOM) with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization.