Distinct Wave Research Articles

Gain Stabilization Method for Wideband Slot-Coupled Microstrip Antenna

Wideband slot-coupled microstrip antenna (SCMSA) is a distinctive electromagnetic wave radiator in recent years with wide bandwidth and low profile. In such a wide frequency range, the electrical distance, i.e., normalized to operating wavelength, between dual equivalent magnetic currents increases obviously with upward frequency. Therefore, the realized gain is usually with a large variation, which limits the wideband performance of SCMSA. In this communication, a feasible method is proposed to stabilize the realized gain of an SCMSA over its entire impedance bandwidth by utilizing a properly designed reflector-plus-sidewall structure (RPSS), which includes a reflector with an optimized height and two vertical sidewalls. Each part has its own function in realized gain compensation and enhancement, performing a flatter and higher realized gain in a wide frequency range. To validate this method, an antenna prototype is fabricated and tested. Compared with the referenced SCMSA, the measured results indicate that the proposed one adding RPSS maintains a wide impedance bandwidth of 24.8% (3.75–4.81 GHz), but reduces gain variation from 4.1 to 0.5 dB (10.5–11 dBi) with an average realized gain increment of 2.1 dB.

Microscopic multifrequency magnetic resonance elastography of ex vivo abdominal aortic aneurysms for extracellular matrix imaging in a mouse model

An abdominal aortic aneurysm (AAA) is a permanent dilatation of the abdominal aorta, usually accompanied by thrombus formation. The current clinical imaging modalities cannot reliably visualize the thrombus composition. Remodeling of the extracellular matrix (ECM) during AAA development leads to stiffness changes, providing a potential imaging marker. 14 apolipoprotein E-deficient mice underwent surgery for angiotensin II-loaded osmotic minipump implantation. 4 weeks post-op, 5 animals developed an AAA. The aneurysm was imaged ex vivo by microscopic multifrequency magnetic resonance elastography (µMMRE) with an in-plane resolution of 40 microns. Experiments were performed on a 7-Tesla preclinical magnetic resonance imaging scanner with drive frequencies between 1000 Hz and 1400 Hz. Shear wave speed (SWS) maps indicating stiffness were computed based on tomoelastography multifrequency inversion. As control, the aortas of 5 C57BL/6J mice were examined with the same imaging protocol. The regional variation of SWS in the thrombus ranging from 0.44 ± 0.07 to 1.20 ± 0.31 m/s was correlated fairly strong with regional histology-quantified ECM accumulation (R2 = 0.79). Our results suggest that stiffness changes in aneurysmal thrombus reflect ECM remodeling, which is critical for AAA risk assessment. In the future, µMMRE could be used for a mechanics-based clinical characterization of AAAs in patients. Statement of significanceTo our knowledge, this is the first study mapping the stiffness of abdominal aortic aneurysms with microscopic resolution of 40 µm. Our work revealed that stiffness critically changes due to extracellular matrix (ECM) remodeling in the aneurysmal thrombus. We were able to image various levels of ECM remodeling in the aneurysm reflected in distinct shear wave speed patterns with a strong correlation to regional histology-quantified ECM accumulation. The generated results are significant for the application of microscopic multifrequency magnetic resonance elastography for quantification of pathological remodeling of the ECM and may be of great interest for detailed characterization of AAAs in patients.

Soliton structures in optical fiber communications with Kundu–Mukherjee–Naskar model

Abstract In the present work, we investigate soliton structures in optical fiber communications. The medium is described by the Kundu–Mukherjee–Naskar model. With the aid of the ansatz approach, the exact solutions are constructed. Consequently, distinct wave structures including W-shaped, bright and dark solitons are derived. These new soliton solutions are retrieved under certain parametric conditions. Besides, it is found that the bright soliton has two different types in a particular limit. Optical solitons are displayed graphically to shed light on their behaviors.

Peace, Protest and Precarity: Making Conceptual Sense of Young People\u2019s Non-violent Dissent in a Period of Intersecting Crises

The current young generation are living through socio-historically situated intersecting crises, including precarity and climate change. In these times of crisis, young people are also bearing witness to a distinctive global wave of youth-led activism involving protest actions. Much of this activism can be deemed dissent because many young activists are calling for systemic change, including the radical disruption, reimagining and rebuilding of the social, economic and political status quo. In this interdisciplinary article, between politics and peace studies, we investigate how the concept of peace plays an important role in some young dissent, and specifically the dissent of young people taking action on climate change. We observed that these young environmental activists often describe their actions in careful terms of positive peace, non-violence, kindness and care, in order to express their dissent as what we interpret as positive civic behaviour. They also use concepts grounded in peace and justice to navigate their economic, political and social precarity. Based on a youth-centred study, drawing on insightful face to face semi-structured interviews in Britain and France with school climate strikers, Friday For Future (FFF) and Extinction Rebellion (XR) activists, we explore how young environmental activists themselves related their dissent, and especially how they attached importance to it being non-violent and/or peaceful. Stemming from our findings, we discuss how young environmental activists’ vision of violence and non-violence adapted to the structural and personal violence they face at the complex intersections of young marginalization, global inequalities and injustices in the lived impact of climate change and the policing of protest.

Spectrogram analysis of surface elevation signals due to accelerating ships

The distinctive wave pattern that forms behind the stern of a moving ship is the result of a combination of divergent and transverse waves across all wavenumbers. At a fixed point in space, as a ship travels past, these waves produce a surface elevation signal in which properties of the ship are encoded in a complicated way. Motivated by the challenge of how to decode such signals, we explore their frequency spectrum using spectrograms. Recent findings are extended to allow for the ship to accelerate along arbitrary paths instead of simply traveling steadily in a straight line.

Multifunctional Waterborne Acoustic Metagratings: From Extraordinary Transmission to Total and Abnormal Reflection

Wavelength-thick multifunctional metagratings for waterborne sound are highly desirable in various application scenarios, such as human health monitoring and ocean exploration. In this article, we present a class of metagratings with which distinct and switchable wave manipulation functionalities, such as extraordinary transmission, total reflection, and abnormal reflection can be achieved through a single acoustic grating. Simultaneous and high-efficiency control over both reflected and transmitted waves is achieved through a systematic design approach in which wave diffraction theory, effective medium theory, and intelligent optimization algorithms are concurrently utilized. Switching between different functionalities can be achieved simply by changing the operation frequency, or by changing the incident angles. Robust and perfect wave-front manipulation effects are obtained over a wide range of incident angles and operation frequencies. Our work not only provides a design paradigm of planar acoustic devices for multiple manipulation purposes, but also presents a feasible solution for the development of integrated acoustic devices for distinct underwater applications.

Geometric transformations on a topological black hole and their applications

Topology and geometry can be used to classify interpretation of many astronomical phenomena in our universe. We characterize the spherical topology of black holes in a special case of spherical symmetry. For this purpose, we carefully consider the metrics space of topological black holes B4. By adjusting some of the parameters, we infer the appropriate components and the equatorial geodesics on the line element of the topological black holes. We also construct the minimal retraction ρ2:B4→C23. As a result, the minimal deformation retract has also been inferred to explain the effects on their center of mass in binary system. This would help us to better understand some of possible applications in astrophysics and cosmology, such as the natural phenomenon of a distinctive gravitational wave signature of merging two black holes associated with curved space–time in general relativity. In addition, we discuss the relation between limit folding and limit minimal retraction on the n-dimension. Under the folding map on the connected sum of essential sub-manifolds, the topological black hole can be constructed for different types and characteristics.

Similarity and Froude Number Similitude in Kinematic and Hydrodynamic Features of Solitary Waves over Horizontal Bed

This study presents, experimentally, similarity and Froude number similitude (FNS) in the dimensionless features of two solitary waves propagating over a horizontal bed, using two wave gauges and a high-speed particle image velocimetry (HSPIV). The two waves have distinct wave heights H0 (2.9 and 5.8 cm) and still water depths h0 (8.0 and 16.0 cm) but identical H0/h0 (0.363). Together with the geometric features of free surface elevation and wavelength, the kinematic characteristics of horizontal and vertical velocities, as well as wave celerity, are elucidated. Illustration of the hydrodynamic features of local and convective accelerations are also made in this study. Both similarity and FNS hold true for the dimensionless free surface elevation (FSE), wavelength and celerity, horizontal and vertical velocities, and local and convective accelerations in the horizontal and vertical directions. The similarities and FNSs indicate that gravity dominates and governs the wave kinematics and hydrodynamics.

Diverse bistable dark novel explicit wave solutions of cubic–quintic nonlinear Helmholtz model

This paper examines three different recent computational schemes (extended simplest equation (ESE) method, modified Kudryashov (MKud) method, and modified Khater (MKha) method) for obtaining novel solitary wave solutions of cubic–quintic nonlinear Helmholtz (CQ–NLH) model. This model is considered as a general model of the well-known Schrödinger equation where it takes into account the effects of backward scattering that are neglected in the more common nonlinear Schrödinger model. Many distinct wave solutions are explained in the different formulas, such as trigonometric, rational, and hyperbolic formulas. These solutions are described in some precise sketches in two- and three-dimensional. The methods’ performance is explained to demonstrate their effectiveness and power.

Inverse scattering transform for the coupled modified Korteweg-de Vries equation with nonzero boundary conditions

In this paper, we study the inverse scattering transform for the coupled modified Korteweg-de Vries (cmKdV) equation with nonzero boundary conditions (NZBCs) at infinity. In order to deal with the direct and inverse scattering problems, a suitable uniformization variable is given on a complex plane by transforming a two-sheeted Riemann surface. In the direct scattering problem, we discuss the analyticity, three symmetries and asymptotic behaviors of the Jost functions, scattering matrices and the distribution of discrete spectral. In the inverse scattering problem, the Riemann-Hilbert (RH) problem of cmKdV equation is first found by using the analyticity of the modified eigenfunctions and scattering coefficients. The reconstruction formulae solution with simple poles, trace formulae and asymptotic phase difference are obtained. Finally, we analyze soliton solutions for eight distinct wave structures of reflectionless potential in the RH problem, include one-kink, dark, bright solitons, novel periodic solutions and two-soliton solutions.

Observation of a Dissipative Time Crystal.

We present the first experimental realization of a time crystal stabilized by dissipation. The central signature in our implementation in a driven open atom-cavity system is a period doubled switching between distinct checkerboard density wave patterns, induced by the interplay between controlled cavity dissipation, cavity-mediated interactions, and external driving. We demonstrate the robustness of this dynamical phase against system parameter changes and temporal perturbations of the driving.

High‐Frequency Sea Ice Variability in Observations and Models

AbstractWe characterize high‐frequency variability of sea ice extent (HFVSIE) in observations and climate models. We find that HFVSIE in models is biased low with respect to observations, especially at synoptic timescales (<20 days) in the Arctic year‐round and at monthly timescales (30–60 days) in Antarctica in winter. Models show large spread in HFVSIE, especially in Antarctica. This spread is partly explained by sea ice mean‐state while model biases in sea level pressure (SLP) and wind variability do not appear to play a major role in HFVSIE spread. Extreme sea ice extent (SIE) changes are associated with SLP anomaly dipoles aligned with the sea ice edge and winds directed on‐ice (off‐ice) during SIE loss (gain) events. In observations, these events are also associated with distinct ocean wave states during the cold season, when waves are greater (smaller) and travel toward (away from) the sea ice edge during SIE loss (gain) events.

Anisotropy as a diagnostic test for distinct tensor-network wave functions of integer- and half-integer-spin Kitaev quantum spin liquids

Contrasting ground states of quantum magnets with the integer- and half-integer-spin moments are the manifestation of many-body quantum interference effects. In this work, we investigate the distinct nature of the integer- and half-integer-spin quantum spin liquids in the framework of the Kitaev's model on the honeycomb lattice. The models with arbitrary spin quantum numbers are not exactly solvable in contrast to the well-known quantum spin liquid solution of the spin-1/2 system. We use the tensor-network wave functions for the integer-and half-integer-spin quantum spin liquid states to unveil the important difference between these states. We find that the distinct sign structures of the tensor-network wave function for the integer- and half-integer-spin quantum spin liquids are responsible for completely different ground states in the spatially anisotropic limit. Hence the spatial anisotropy would be a useful diagnostic test for distinguishing these quantum spin liquid states, both in the numerical computations and experiments on real materials. We support this discovery via extensive numerics including the tensor-network, DMRG, and exact diagonalization computations.

Lump chains in the KP‐I equation

AbstractWe construct a broad class of solutions of the Kadomtsev–Petviashvili (KP)‐I equation by using a reduced version of the Grammian form of the ‐function. The basic solution is a linear periodic chain of lumps propagating with distinct group and wave velocities. More generally, our solutions are evolving linear arrangements of lump chains, and can be viewed as the KP‐I analogues of the family of line‐soliton solutions of KP‐II. However, the linear arrangements that we construct for KP‐I are more general, and allow degenerate configurations such as parallel or superimposed lump chains. We also construct solutions describing interactions between lump chains and individual lumps, and discuss the relationship between the solutions obtained using the reduced and regular Grammian forms.

Flow and performance analysis of a natural gas-air rotating detonation engine with high-speed velocimetry

An experimental investigation of a high pressure, natural gas-air rotating detonation engine is presented. Simultaneous high-speed measurements of combustion chamber pressure, axially-integrated chamber chemiluminescence, and particle image velocimetry at the combustor exit plane were used to qualitatively and quantitatively analyze the exhaust flow of two test conditions with distinct wave dynamics. A single detonation wave with an intermittent counter-rotating wave was characterized in the first test case, while a steady counter-rotating mode was studied in the second. Analysis using the continuous wavelet transform informs the coupled shift in the frequency and amplitude of pressure and velocity fluctuations observed in the raw timeseries. The high-speed measurements are used to reconstruct the wave structure for each case over the course of a cycle, revealing the canonical rotating detonation engine exhaust flow structure with a trailing oblique shock sweeping through the products for the single wave case. Interactions between counter-propagating detonation fronts result in a flowfield that varies with cycle phase angle, in contrast to the self-similar field of the single propagating wave. The axial velocity profile around the circumference of the combustor is independent of wave location, while azimuthal velocity fluctuations from the trailing oblique shocks are observed to track the detonation fronts and destructively interfere at wave intersections. The total pressure and temperature of flow exiting the combustor are computed using the phase-resolved velocity measurements along with the measured reactant flowrate and thrust to close the global balance of mass and momentum. The case with counter-rotating waves delivers 5% higher performance than the single-wave case. The application of simultaneous high-speed diagnostics helps elucidate the flow structure in a rotating detonation engine and provides a connection between the local flow structure and global combustor performance.

Teleconnections Governing the Interannual Variability of Great Plains Low-Level Jets in May

AbstractA spectral analysis of Great Plains 850-hPa meridional winds (V850) from ECMWF’s coupled climate reanalysis of 1901–2010 (CERA-20C) reveals that their warm season (April–September) interannual variability peaks in May with 2–6-yr periodicity, suggestive of an underlying teleconnection influence on low-level jets (LLJs). Using an objective, dynamical jet classification framework based on 500-hPa wave activity, we pursue a large-scale teleconnection hypothesis separately for LLJs that are uncoupled (LLJUC) and coupled (LLJC) to the upper-level jet stream. Differentiating between jet types enables isolation of their respective sources of variability. In the U.S. south-central plains (SCP), May LLJCs account for nearly 1.6 times more precipitation and 1.5 times greater V850 compared to LLJUCs. Composite analyses of May 250-hPa geopotential height (Z250) conditioned on LLJC and LLJUC frequencies highlight a distinct planetary-scale Rossby wave pattern with wavenumber 5, indicative of an underlying circumglobal teleconnection (CGT). An index of May CGT is found to be significantly correlated with both LLJC (r = 0.62) and LLJUC (r = −0.48) frequencies. Additionally, a significant correlation is found between May LLJUC frequency and NAO (r = 0.33). Further analyses expose decadal-scale variations in the CGT–LLJC and CGT–LLJUC teleconnections that are linked to the PDO. Dynamically, these large-scale teleconnections impact LLJ class frequency and intensity via upper-level geopotential anomalies over the western United States that modulate near-surface geopotential and temperature gradients across the SCP.

The evolution and runup of nonbreaking undular surges

Physical experiments were conducted in a long water wave tank over a wide range of still water depths to study the evolution and runup of nonbreaking undular surges generated by the release of a given volume of water. The results demonstrated that the wavefront of a nonbreaking undular surge closely matched that of the corresponding solitary wave of the same height. The wave celerity of the surge could be accurately predicted using the solitary wave theory. Two distinct wave stages existed in the evolution process of a nonbreaking undular surge based on the wave shape asymmetry. The wave stage transition could be approximated as a surge Froude number equal to 1.15. The wave amplitude and steepness of undular surges were in reasonable agreement with the linear wave theory for surge Froude numbers greater than 1.20. However, the wave length data presented a different pattern to that predicted by either the linear wave theory or the solution of the Boussinesq equation. Furthermore, the maximum surge runup on a vertical wall was in excellent agreement with the solitary wave theory. This study provided new insights into the quantitative behavior of nonbreaking undular surges.

Electron Bernstein waves and narrowband plasma waves near the electron cyclotron frequency in the near-Sun solar wind

Context. Recent studies of the solar wind sunward of 0.25 AU reveal that it contains quiescent regions, with low-amplitude plasma and magnetic field fluctuations, and a magnetic field direction similar to the Parker spiral. The quiescent regions are thought to have a more direct magnetic connection to the solar corona than other types of solar wind, suggesting that waves or instabilities in the quiescent regions are indicative of the early evolution of the solar wind as it escapes the corona. The quiescent solar wind regions are highly unstable to the formation of plasma waves near the electron cyclotron frequency (fce). Aims. We examine high time resolution observations of these waves in an effort to understand their impact on electron distribution functions of the quiescent near-Sun solar wind. Methods. High time resolution waveform captures of near-fce waves were examined to determine variations of their amplitude and frequency in time as well as their polarization properties. Results. We demonstrate that the near-fce wave intervals contain several distinct wave types, including electron Bernstein waves and extremely narrowband waves that are highly sensitive to the ambient magnetic field orientation. Using the properties of these waves, we suggest possible plasma wave mode classifications and possible instabilities that generate these waves. The results of this analysis indicate that these waves may modify the cold core of the electron distribution functions in the quiescent near-Sun solar wind.

Improved full waveform moment tensor inversion of Cratonic intraplate earthquakes in southwest Australia

SUMMARYIn contrast to global observations in stable continental crust, the present-day orientation of the maximum horizontal stress in Western Australia is at a high angle to plate motion, suggesting that in addition to large-scale plate driving forces, local factors also play an important role in stress repartitioning. As a reliable stress indicator, full waveform moment tensor solutions are calculated for earthquakes that occurred between 2010 and 2018 in the southern Yilgarn Craton and the adjacent Albany-Fraser Orogen in southwestern Australia. Due to regional velocity heterogeneities in the crust, we produced two geographically distinct shear wave velocity models by combining published crustal velocity models with new ambient noise tomography results. We applied a full waveform inversion technique to 15 local earthquakes and obtained 10 robust results. Three of these events occurred near Lake Muir in the extreme south of the study area within the Albany-Fraser Orogen. The focal mechanism of the 16th September 2018 Lake Muir event is thrust; two ML≥ 4.0 aftershocks are normal and strike-slip. Our results are consistent with field observations, fault orientations inferred from aeromagnetic data and surface displacements mapped by Interferometric Synthetic Aperture Radar which are all consistent with reactivation of existing faults. The other seven solutions are in the southeastern Yilgarn Craton. These solutions show that the faulting mechanisms are predominantly thrust and strike-slip. This kinematic framework is consistent with previous studies that linked active seismicity in the Yilgarn Craton to the reactivation of the NNW–SSE oriented Neoarchean structures by an approximately E–W oriented regional stress field. Our results suggest that the kind of faulting that occurs in southwest Australia is critically dependent on the local geological structure. Thrust faulting is the dominant rupture mechanism, with some strike-slip faulting occurring on favourably oriented structures.

Four distinct Northeast US heat wave circulation patterns and associated mechanisms, trends, and electric usage

Northeastern US heat waves have usually been considered in terms of a single circulation pattern, the high-pressure circulation typical of most heat waves occurring in other parts of the world. However, k-means clustering analysis from 1980–2018 shows there are four distinct patterns of Northeast heat wave daily circulation, each of which has its own seasonality, heat-producing mechanisms (associated moisture, subsidence, and temperature advection), and impact on electricity demand. Monthly analysis shows statistically-significant positive trends occur in late summer for two of the patterns and early summer for a third pattern, while the fourth pattern shows a statistically significant negative trend in early summer. These results demonstrate that heat waves in a particular geographic area can be initiated and maintained by a variety of mechanisms, resulting in heat wave types with distinct impacts and potential links to climate change, and that pattern analysis is an effective tool to distinguish these differences.