Distinct Phase Shift Research Articles

Twists through turbidity: propagation of light carrying orbital angular momentum through a complex scattering medium

We explore the propagation of structured vortex laser beams-shaped light carrying orbital angular momentum (OAM)-through complex multiple scattering medium. These structured vortex beams consist of a spin component, determined by the polarization of electromagnetic fields, and an orbital component, arising from their spatial structure. Although both spin and orbital angular momenta are conserved when shaped light propagates through a homogeneous, low-scattering medium, we investigate the conservation of these angular momenta during the propagation of Laguerre–Gaussian (LG) beams with varying topological charges through a turbid multiple scattering environment. Our findings demonstrate that the OAM of the LG beam is preserved, exhibiting a distinct phase shift indicative of the ‘twist of light’ through the turbid medium. This preservation of OAM within such environments is confirmed by in-house developed Monte Carlo simulations, showing strong agreement with experimental studies. Our results suggest exciting prospects for leveraging OAM in sensing applications, opening avenues for groundbreaking fundamental research and practical applications in optical communications and remote sensing.

Developmental dynamics in oral fluency and learner motivation: A dual‐focus approach

AbstractAdopting a comprehensive dual‐focus approach to oral fluency development, the present study examined the developmental trajectories of oral fluency in tertiary‐level Chinese EFL learners and identified the motivational attractor states helpful for shaping their oral production. Quantitative and qualitative data were collected over two semesters with monologue tasks and semi‐structured interviews, respectively. Oral fluency development was examined using moving min–max graphs, change point analysis, and Monte Carlo simulations, while the retrodiction approach was utilized to identify influential motivational attractor states. Results showed that, over the course of the study, the two learners experienced distinct variability and phase shifts in their development of oral fluency, largely attributable to their unique motivational attractor states. By employing such a dual‐focus approach, the present study provided a nuanced picture of Chinese EFL learners’ developmental dynamics in terms of both oral fluency and learning motivation and the adaptive interactions between them, thus enriching our understanding of how oral fluency development relates to learner motivation.

Time‐Resolved Photoemission Electron Microscopy on a ZnO Surface Using an Extreme Ultraviolet Attosecond Pulse Pair

AbstractElectrons photoemitted by extreme ultraviolet attosecond pulses derive spatially from the first few atomic surface layers and energetically from the valence band and highest atomic orbitals. As a result, it is possible to probe the emission dynamics from a narrow 2D region in the presence of optical fields, as well as obtain elemental specific information. However, combining this with spatially‐resolved imaging is a long‐standing challenge because of the large inherent spectral width of attosecond pulses, as well as the difficulty of making them at high repetition rates. Here, this work demonstrates an attosecond interferometry experiment on a zinc oxide (ZnO) surface using spatially and energetically resolved photoelectrons. Photoemission electron microscopy is combined with near‐infrared pump ‐ extreme ultraviolet probe laser spectroscopy and the instantaneous phase of an infrared field is resolved with high spatial resolution. Results show how the core level states with low binding energy of ZnO are well suited to perform spatially resolved attosecond interferometry experiments. A distinct phase shift of the attosecond beat signal is observed across the laser focus which is attributed to wavefront differences between the pump and the probe fields at the surface. This work demonstrates a clear pathway for attosecond interferometry with high spatial resolution at atomic scale surface regions opening up for a detailed understanding of nanometric light‐matter interaction.

Inhomogeneity identification by measuring magnetic quantum oscillations

This study explores the identification of sample inhomogeneity via magnetic quantum oscillations analysis in semimetal NbSb2. By doping Bi and Cr, we obtained a homogenous Bi-doped sample and an inhomogeneous Cr-doped sample, whose homogeneity was confirmed by comparing the magnetic quantum oscillation before and after grinding the samples. The magnetic quantum oscillations in the inhomogeneous sample exhibited a distinct phase shift and unusual field-dependent amplitude, believed to result from a non-uniform Fermi energy. The analysis of the magnetic quantum oscillations demonstrated that the homogeneous Bi-doped sample can be interpreted by the symmetric and Lorentzian effective Fermi energy distribution, while the inhomogeneous Cr-doped sample exhibited an asymmetric distribution, illustrating an unconventional violation of the Lifshitz-Kosevich formula. This research provides a novel method for identifying material inhomogeneity and mitigating potential misinterpretations of magnetic quantum oscillations' unusual phase, commonly seen as a nontrivial Berry phase indicator in topological materials studies.

Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions.

We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field and report on phase shifts in the current-phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to φ0 = 0.5π, which are consistent with a Zeeman field coupling to highly transmissive Andreev bound states via Rashba spin-orbit interaction. A distinct phase shift emerges at larger fields, concomitant with a switching current minimum and the closing and reopening of the superconducting gap. These signatures of an induced phase transition, which might resemble a topological transition, scale with the superconducting lead size, demonstrating the crucial role of orbital effects. Our results elucidate the interplay of Zeeman, spin-orbit, and orbital effects in InAs/Al JJs, giving improved understanding of phase transitions in hybrid JJs and their applications in quantum computing and superconducting electronics.

Modeling and estimation of synchronization in size-sorted portfolio returns

This paper examines the lead/lag relations between size-sorted portfolio returns through the lens of financial cycles governing these returns using a novel econometric methodology. Specifically, we develop a Markov-switching vector autoregressive model that allows for imperfect synchronization of cyclical regimes such as bull and bear market regimes in US large-, mid- and small-cap portfolio returns. This is achieved by characterizing the cycles of the mid- and small-cap portfolio returns in concordance with the cycle of large-cap portfolio returns together with potential phase shifts. We find that a three-regime model with distinct phase shifts across regimes characterizes the joint distribution of returns most adequately. These regimes are closely linked to the business cycle and small-cap portfolio returns are more sensitive to the cyclical phases than the large-cap portfolios. While all portfolios switch contemporaneously into boom and crash regimes, the large-cap portfolio leads the small-cap portfolio for switches to a moderate regime from a boom regime by a month. This suggests that small-cap portfolio adjusts with a delay to the relatively negative news compared to portfolios with larger market capitalization. We document that information diffusion accelerates in response to surprises related to the monetary policy. This reflects a link between financial returns and real economic activity from the viewpoint of ‘financial accelerator theory’ where portfolios with distinct size serve as a proxy for firm characteristics.

Rational design of mixed ionic–electronic conducting membranes for oxygen transport

The mixed ionic–electronic conducting (MIEC) oxides have generated significant research efforts in the scientific community during the last 40 years. Since then, many MIEC compounds, most of which are based on perovskite oxides, have been synthesized and characterized. These compounds, when heated to high temperatures, form solid ceramic membranes with high oxygen ionic and electrical conductivity. The driving force for oxygen ion transport is the ionic transfer of oxygen from the air as a result of the differential partial pressure of oxygen across the membrane. Electronic and ionic transport in a range of MIEC materials has been studied using the defect theory, particularly when dopants are introduced to the compound of interest. As a result, many types of ionic oxygen transport limits exist, each with a distinct phase shift depending on the temperature and partial pressure of oxygen in use. In combination with theoretical principles, this work attempts to evaluate the research community's major and meaningful achievements in this subject throughout the preceding four decades.

Non-destructive lock-in thermography of green powder metallurgy component inhomogeneities: A predictive imaging method for manufactured component flaw prevention

Pre-sintered (“green”) compressed metal powder components were studied using non-destructive imaging by means of Lock-In Thermography (LIT) for assessing the capability of this methodology to produce quantitative information on crucial material integrity properties through preventive non-destructive evaluation (P-NDE). A major goal of the work was to develop the LIT potential to reduce economic and environmental waste in automotive manufacturing that impacts mechanical strength and integrity, such as density non-uniformity. Using pre-optimized experimental parameters including infrared-camera phase stabilization by means of high sampling rates, highly reproducible quantitative phase image results from LIT were shown to reveal distinct phase shift bi-modalities and widespread non-uniformity in an industrial sample which exhibited surface cracks in the green (pre-sintered) state. In juxtaposition, LIT phase images from another green sample without cracks were much more uniform across the entire sample. A regression-fitting program was used to determine the local thermal diffusivity at critical phase-varying locations of the cracked sample in the green state and a positive correlation was found between the thermal diffusivity and the measured phase shift with a lone exception occurring at the exact location of cracks. Local sample porosity measurements in selected regions of interest (ROI) of the sample using concomitant high-resolution optical imaging were introduced and revealed a positive correlation between the experimental LIT phase shift results and porosity which determines local density. The combination of these procedures led to the development of a potential industrial imaging modality for P-NDE as an important new inspection approach. This approach may lead to identifying catastrophic flaws/cracks before the emergence of such flaws and before proceeding to irreversible sintering of manufactured products, thereby allowing the operator to minimize material waste and effectively optimize production costs with the added advantage of developing environmentally friendly manufacturing processes.

An ultrathin acoustic carpet cloak based on resonators with extended necks

By employing a set of resonators with extended necks, an ultrathin acoustic carpet cloak with a thickness of about 1/30th of the operation wavelength is proposed to achieve effective cloaking around a bump at 1000 Hz. The cloak is composed of a periodic array of supercells. The supercell is constructed by a solid unit and seven inhomogeneous resonators with different extended necks. The elements in the supercell are capable of achieving distinct phase shifts ranging from 0 to 2π in a phase increment of π/4. To demonstrate the effectiveness of the cloak, both normal incidence and oblique incidence (incident angle equals to 30°) plane waves impinging on a cloaked triangular bump are investigated numerically and validated experimentally. The results show that it is possible to conceal the bump by wrapping over the surface of the bump through using the proposed ultrathin carpet cloak. As a resonant-element based acoustic device, the cloak exhibits invisibility in the frequency range from 980 to 1070 Hz. The proposed acoustic metasurface offers a simple and compact solution for acoustic cloaking and may hold promise in realistic applications.

Unique Multimessenger Signal of QCD Axion Dark Matter.

We propose a multimessenger probe of QCD axion dark matter based on observations of black hole-neutron star binary inspirals. It is suggested that a dense dark matter spike may grow around intermediate mass black holes (10^{3}-10^{5} M_{⊙}). The presence of such a spike produces two unique effects: a distinct phase shift in the gravitational wave strain during the inspiral and an enhancement of the radio emission due to the resonant axion-photon conversion occurring in the neutron star magnetosphere throughout the inspiral and merger. Remarkably, the observation of the gravitational wave signal can be used to infer the dark matter density and, consequently, to predict the radio emission. We study the projected reach of the LISA interferometer and next-generation radio telescopes such as the Square Kilometre Array. Given a sufficiently nearby system, such observations will potentially allow for the detection of QCD axion dark matter in the mass range 10^{-7} eV to 10^{-5} eV.

Generalized 3D high cycle fatigue criteria for multiscale bridging‐based progressive damage analysis of multilayer composite parts under random loads and material deterioration

AbstractTwo frameworks are employed to develop two distinct categories of multiaxial high cycle fatigue life assessment models for composite components experiencing general and random loading conditions. In this regard, the decay in the material properties with cycles is also taken into account. It is obvious that in multilayer components, the fatigue failure is a progressive process that may be accompanied by gradual or sudden changes in the material properties and, consequently, the resulting stresses. In addition to using the traditional progressive damage analyses, a new concept is proposed for tracing of the localized fatigue failures more accurately. It is postulated that generally, the stress components have distinct frequencies, phase shifts, and mean values that all vary with time in a random manner. The proposed fatigue criteria, especially, the equivalent‐stress–based ones, are capable of predicting various fatigue failure modes, such as the fibre breakage, matrix cracking, and interfacial debonding. A special and comprehensive fatigue failure tracking and cycle counting algorithms that are capable of handling the mentioned general peculiarities are proposed. The proposed HCF criteria and the relevant fatigue life assessment algorithm are then implemented on a composite multilayer mono‐leaf spring of a realistic vehicle under a random field‐measured loading condition, as a typical component, and the results are compared and the experimental results conducted by the authors, for accuracy investigations. The considered stochastic road inputs have been chosen on the basis of the consumption times and field measurements.

Subtyping of Magnetically Isolated Breast Cancer Cells Using Magnetic Force Microscopy.

Circulating tumor cell (CTC) which recently arisen as potential sources for monitoring and characterizing non-haematologic cancers and their metastatic derivatives. Immunomagnetic microbeads and magnetic nanoparticles (MNPs) have been extensively explored to isolate CTCs from blood samples. However, MNPs attached on the membrane protein are interrupted further analysis to distinguish the cancer subtype by consumption or blocking the target surface marker. Here, an MNP-mediated analysis method for surface marker expression profile by magnetic force microscopy (MFM) is described. Two MNPs, zinc ferrite and iron oxide, are showed distinct phase shift (-16.5° and -3.7°, respectively) signal on the MFM images. The antibody conjugated MNPs are successfully isolated target cells without giving damage to the cell. The MFM image of MNP decorated cells show clear differences between two breast cancer cell lines, MCF-7 and SK-BR-3, which proof the cancer subtyping property using MFM method. To confirmation of the surface marker consumption during the cell isolation, antibody-conjugated quantum dots and drug-loaded oleosome are treated on the cells, thereby MNP decorated cells are survived. This newly developed MFM analysis method provides a new direction to utilize the MNP for the surface marker expression phenotypes.

Optical assessment of colored dissolved organic matter and its related parameters in dynamic coastal water systems

Prediction of the curve of the absorption coefficient of colored dissolved organic matter (CDOM) and differentiation between marine and terrestrially derived CDOM pools in coastal environments are hampered by a high degree of variability in the composition and concentration of CDOM, uncertainties in retrieved remote sensing reflectance and the weak signal-to-noise ratio of space-borne instruments. In the present study, a hybrid model is presented along with empirical methods to remotely determine the amount and type of CDOM in coastal and inland water environments. A large set of in-situ data collected on several oceanographic cruises and field campaigns from different regional waters was used to develop empirical methods for studying the distribution and dynamics of CDOM, dissolved organic carbon (DOC) and salinity. Our validation analyses demonstrated that the hybrid model is a better descriptor of CDOM absorption spectra compared to the existing models. Additional spectral slope parameters included in the present model to differentiate between terrestrially derived and marine CDOM pools make a substantial improvement over those existing models. Empirical algorithms to derive CDOM, DOC and salinity from remote sensing reflectance data demonstrated success in retrieval of these products with significantly low mean relative percent differences from large in-situ measurements. The performance of these algorithms was further assessed using three hyperspectral HICO images acquired simultaneously with our field measurements in productive coastal and lagoon waters on the southeast part of India. The validation match-ups of CDOM and salinity showed good agreement between HICO retrievals and field observations. Further analyses of these data showed significant temporal changes in CDOM and phytoplankton absorption coefficients with a distinct phase shift between these two products. Healthy phytoplankton cells and macrophytes were recognized to directly contribute to the autochthonous production of colored humic-like substances in variable amounts within the lagoon system, despite CDOM content being partly derived through river run-off and wetland discharges as well as from conservative mixing of different water masses. Spatial and temporal maps of CDOM, DOC and salinity products provided an interesting insight into these CDOM dynamics and conservative behavior within the lagoon and its extension in coastal and offshore waters of the Bay of Bengal. The hybrid model and empirical algorithms presented here can be useful to assess CDOM, DOC and salinity fields and their changes in response to increasing runoff of nutrient pollution, anthropogenic activities, hydrographic variations and climate oscillations.

Thermocline bulk shear analysis in the northern North Sea

Thermocline bulk shear is investigated in the northern North Sea using historical observations. The conventional bulk shear is modified to define a thermocline bulk shear (TBS), in order to better represent the shear across the thermocline. The TBS computed by observed currents is decomposed into components at different frequency bands. The near-inertial TBS is the largest component. Its dominance is significant during the period of high wind. It is formed by the wind-driven near-inertial current which has a distinct phase shift (∼180°) across the thermocline. A linear model is presented, which well simulates the observed near-inertial TBS, especially during the period of relatively strong wind. The semidiurnal TBS makes a secondary contribution to the total TBS. It is only slightly smaller than the near-inertial TBS when the wind is relatively weak. The large values of semidiurnal TBS are associated with semidiurnal currents which have a phase shift (∼30–40°) or a magnitude difference (∼5 cm/s) across the thermocline. The low-frequency (<0.7 cpd) TBS also makes an episodic contribution to the total. Its variation coincides with the Ekman transport during the period of relatively strong wind. The low-frequency TBS is mainly formed by an Ekman-like clockwise spiraling of velocity with depth or a distinct magnitude difference in velocities between upper and lower layers.

Efficient Recovery of Sub-Nyquist Sampled Sparse Multi-Band Signals Using Reconfigurable Multi-Channel Analysis and Modulated Synthesis Filter Banks

Sub-Nyquist cyclic nonuniform sampling (CNUS) of a sparse multi-band signal generates a nonuniformly sampled signal. Assuming that the corresponding uniformly sampled signal satisfies the Nyquist sampling criterion, the sequence obtained via CNUS can be passed through a reconstructor to recover the missing uniform-grid samples. At present, these reconstructors have very high design and implementation complexity that offsets the gains obtained due to sub-Nyquist sampling. In this paper, we propose a scheme that reduces the design and implementation complexity of the reconstructor. In contrast to the existing reconstructors which use only a multi-channel synthesis filter bank (FB), the proposed reconstructor utilizes both analysis and synthesis FBs which makes it feasitble to achieve an order-of-magnitude reduction of the complexity. The analysis filters are implemented using polyphase networks whose branches are allpass filters with distinct fractional delays and phase shifts. In order to reduce both the design and the implementation complexity of the synthesis FB, the synthesis filters are implemented using a cosine-modulated FB. In addition to the reduced complexity of the reconstructor, the proposed multi-channel recovery scheme also supports online reconfigurability which is required in flexible (multi-mode) systems where the user subband locations vary with time.

Process‐based modeling of kilometer‐scale alongshore sandbar variability

AbstractSubtidal nearshore sandbars may exhibit cyclic net offshore migration during their multi‐annual lifetime along many sandy coasts. Although this type of behavior can extend continuously for several kilometers, alongshore variations in cross‐shore bar position and bar amplitude are commonly observed. Alongshore variability is greatest when bars display km‐scale disruptions, indicative of a distinct alongshore phase shift in the bar cycle. An outer bar is then attached to an inner bar, forming a phenomenon known as a bar switch. Here, we investigate such large‐scale alongshore variability using a process‐based numerical profile model and observations at 24 transects along a 6 km section of the barred beach at Noordwijk, The Netherlands. When alongshore variability is limited, the model predicts that the bars migrate offshore at approximately the same rate (i.e. the bars remain in phase). Only under specific bar configurations with high wave‐energy levels is an increase in the alongshore variability predicted. This suggests that cross‐shore processes may trigger a switch in the case of specific antecedent morphological configurations combined with storm conditions. It is expected that three‐dimensional (3D) flow patterns augment the alongshore variability in such instances. In contrast to the observed bar behaviour, predicted bar morphologies on either side of a switch remain in different phases, even though the bars are occasionally located at a similar cross‐shore position. In short, the 1D model is not able to remove a bar switch. This data‐model mismatch suggests that 3D flow patterns are key to the dissipation of bar switches. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Analysis of stator current of induction motor used in transport system at single phasing by measuring phase angle, symmetrical components, Skewness, Kurtosis and harmonic distortion in Park plane

Stator current of induction motor is analysed at single phasing by measuring phase angle, symmetrical components, Skewness, Kurtosis and harmonic distortion in Park plane. Diagnosis of single phasing of induction motor has been achieved by sequence components and stator current based pattern assessment. Distinct phase shift from 120° to 180° is observed between healthy phases. Patterns are formed using line currents and single phasing is assessed by using rule sets developed from features extracted from those patterns. Experimental result agrees with rule set and result obtained by assessment using sequence components. Then assessment is done by analysing wavelet decomposition based Skewness and Kurtosis of stator current in Park plane. At last, area based approach is used for assessment of single phasing and different distortion factors because of harmonics in Park plane are assessed. Accuracy increases with the increase of sampling rate of data acquisition system and use of Park plane has reduced computation effort by two-thirds. Thus single phasing is detected by sequence components supported by pattern formation and feature extraction and then harmonics during single phasing are assessed by wavelet decomposition and area-based approach in Park plane.

Social movements, competing rationalities and trigger events: The complexity of Chinese popular mobilizations

This article addresses popular mobilizations in repressive regimes, with China as a case in point. It argues that such mobilizations are very different from those in democratic societies and may not be captured in the single-stranded rationalism promoted by much social movement theory. Without access to political representation and stable outlets for social criticism, mobilizations are likely to be set off by ‘trigger events’, just as their growth occurs through distinct phase shifts. A range of Chinese mobilizations over the last several years are introduced. They tend to show that people initially are driven by simple causes rather than ‘ideology’, and often with an ingrained conflict of beliefs. Yet, due to regime reprisal, it may be a short step from addressing a small local issue to challenging the political system as a whole. With reference to complexity theory it is shown that emergent new forms of organized resistance will never follow a linear and predictable development but will be contextually embedded and continually exchanging with that particular cultural and political environment. Thus, when we see the sudden growth of movements which step over the threshold into open discontent and public resistance, the outcome for both the movement itself and the system as a whole is inherently unpredictable.

Multiple soliton solutions for some (3+1 )-dimensional nonlinear models generated by the Jaulent–Miodek hierarchy

In this work we study four (3+1)-dimensional nonlinear evolution equations, generated by the Jaulent–Miodek hierarchy. We derive multiple soliton solutions for each equation by using the Hereman–Nuseir form, a simplified form of the Hirota’s method. The obtained soliton solutions are characterized by distinct phase shifts.

Object selection in visual scene via oscillatory network with controllable coupling and self-organized performance

An oscillatory network model with controllable coupling and self-organized synchronization-based performance was developed for image processing. The model demonstrates the following capabilities: (a) brightness segmentation of real grey-level images; (b) colored image segmentation; (c) selective image segmentation--extraction of the subset of image fragments with brightness values contained in an arbitrary given interval. An additional capability--successive selection of spatially separated fragments of a visual scene--has been achieved via further model extension. The fragment selection (under minor natural restrictions on mutual fragment locations) is based on in-phase internal synchronization of oscillator ensembles, corresponding to all the fragments, and distinct phase shifts between different ensembles.