Anomalous Fluctuations Research Articles

Odd Viscosity Suppresses Intermittency in Direct Turbulent Cascades.

Intermittency refers to the broken self-similarity of turbulent flows caused by anomalous spatiotemporal fluctuations. In this Letter, we ask how intermittency is affected by a nondissipative viscosity, known as odd viscosity (also Hall viscosity or gyroviscosity), which appears in parity-breaking fluids such as magnetized polyatomic gases, electron fluids under magnetic field, and spinning colloids or grains. Using a combination of Navier-Stokes simulations and theory, we show that intermittency is suppressed by odd viscosity at small scales. This effect is caused by parity-breaking waves, induced by odd viscosity, that break the multiple scale invariances of the Navier-Stokes equations. Building on this insight, we construct a two-channel helical shell model that reproduces the basic phenomenology of turbulent odd-viscous fluids including the suppression of anomalous scaling. Our findings illustrate how a fully developed direct cascade that is entirely self-similar can emerge below a tunable length scale, paving the way for designing turbulent flows with adjustable levels of intermittency.

Characteristics and Effects of the Last Kilometre of the Tourist City from the Dynamic and Static Perspectives

The accessibility of the “last kilometre” of a tourist city has a profound impact on the travelling experience of tourists. In-depth understanding of the characteristics and spatial effects of the “last-kilometre” traffic accessibility in tourist cities is conducive to further enhancing the accessibility of traffic travel and forming a new industry development pattern of deep integration of traffic and tourism. The results show that: (1) Private transport accessibility is significantly better than public transport accessibility, and the strong economic strength of large cities such as Peking, Shanghai, and Nanjing support a wider coverage of public transport compared with cities such as Qinhuangdao, Dalian, Ningbo, etc. Even for the middle-income and high-income groups of the large cities, the advantage of the broader travelling cost of public transport is still significant. (2) The average values of the fluctuation coefficients of travel time of public transport in tourist cities are all smaller than those of private transport, and public transport is less sensitive to traffic congestion, making it a more reliable choice for tourist travel. The higher number of public transport grids with more anomalous fluctuations and much larger fluctuations than private transport grids suggests that there is an urgent need to strengthen the standardisation of public transport services in the corresponding areas. (3) Urban tourism development has been moving from single-line to network development, and the impact of urban transport on urban–regional tourism development has been manifested in the place fission effect, corridor diffusion effect, and regional equilibrium effect. In general, our findings have been useful in understanding the accessibility characteristics of the “last kilometre” in tourist cities, optimizing the efficiency of inter-regional and intra-city transport connections, constructing a fast and convenient travel transport system, improving the accessibility of transport trips, and forming a new development pattern for the deep integration of transport and tourism.

Novel drainage pipeline breakages detection based on MEMS inertial sensor: From mechanism to application

Urban water environment pollution is a global concern, in developing countries, sewage infiltration resulting from urban drainage pipelines breakage is an essential element in the urban groundwater pollution and the recurrence of black odor water bodies, it is crucial to accurately and efficiently detection and localisation of urban drainage pipelines breakage to protect the urban water resources. In this paper, a device for detecting defects in drainage pipelines was developed and assembled using microelectromechanical systems (MEMS) inertial sensors as the core components, and the improved cumulative sum (CUSUM) model was used for anomalous detection of the pitch angle of the device's movement along the course of the pipeline as a method of detecting pipeline breakage. In the laboratory simulation of drainage pipeline tests, the CUSUM peaks (0.709, 1.102, 3.038, 7.990) for the case of external water infiltration rates into the pipeline at the point of pipe breakage (2.9%, 4.6%, 5.8%, 9.2%), and for the cases of sewer exfiltration rates in the pipeline of 4.2% and 6.4% (0.760, 1.382). CFD simulations of the water flow in the laboratory pipeline show a high degree of overlap between the trend of the water surface near the point of breakage and the anomalous fluctuations in the pitch angle of the device motion in the laboratory tests. Finally, the authors tested the device on municipal drains in the city of A. The results demonstrated the reliability and high accuracy of the device. The device enables to improve the ecological quality of urban water environment by accelerating the rate of defect detection in urban drainage pipelines and reducing the detection expenses.

Dynamic magnetic characteristics of the kinetic Ising model under the influence of randomness.

In this paper, we propose to solve the issues of long-range or next-neighbor interactions by introducing randomness. This approach is applied to the square lattice Ising model. The Monte Carlo method with the Metropolis algorithm is utilized to calculate the critical temperature T_{C}^{*} under equilibrium thermodynamic phase transition conditions and to investigate the characterization of randomness in terms of magnetization. In order to further characterize the effect of this randomness on the magnetic system, clustering coefficients C_{p} are introduced. Furthermore, we investigate a number of dynamic magnetic behaviors, including dynamic hysteresis behaviors and metamagnetic anomalies. The results indicate that noise has the effect of destabilizing the system and promoting the dynamic phase transition. When the system is subjected to noise, the effect of this noise can be mitigated by the addition of a time-oscillating magnetic field. Finally, the evolution of anomalous metamagnetic fluctuations under the influence of white noise is examined. The relationship between the bias field corresponding to the peak of the curve h_{b}^{peak} and the noise parameter σ satisfies the exponential growth equation, which is consistent with other results.

Anomalous Fluctuations in a Droplet of Chemically Active Colloids or Enzymes.

Chemically active colloids or enzymes cluster into dense droplets driven by their phoretic response to collectively generated chemical gradients. Employing Brownian dynamics simulation techniques, our study of the dynamics of such a chemically active droplet uncovers a rich variety of structures and dynamical properties, including the full range of fluidlike to solidlike behavior, and non-Gaussian positional fluctuations. Our work sheds light on the complex dynamics of the active constituents of metabolic clusters, which are the main drivers of nonequilibrium activity in living systems.

Cumulative frost heave and hydrothermal process of the high-speed railway subgrade under extreme climate conditions in northwest China

The mechanisms underlying the long-term deformation response and hydrothermal processes of high-speed railway subgrades in high altitude, seasonally frozen regions remain poorly understood, especially under extreme weather conditions. This study, based on an eight-year continuous field monitoring of the Lanzhou-Xinjiang High-Speed Railway (LXHR), presents several novel findings. From 2015 to 2022, air temperature, ground surface temperature, and subgrade surface temperature consistently increased, while the average annual rainfall showed a decreasing trend. During this period, sporadic heavy rainfall events occurred, and the climate demonstrated anomalous fluctuations. Such occasional heavy rainfall can cause a rise in the groundwater table, leading to an increase in frost heave within the subgrade. Given the same climatic conditions, embankments display a greater frozen depth compared to road cuts, but experience relatively less frost heave. Frost heave deformation within the subgrade comprises two components: residual deformation and inherent frost heave deformation. Residual deformation primarily contributes to the annual cumulative increase in frost heave, a process succinctly described as the transportation and deposition of fine particles (less than 2 mm in diameter) in coarse fillers by water, in close proximity to the frozen edge, ranging from 0.8 m to 1.2 m of the subgrade. In summary, the results of this study serve as a reminder for engineering designers and researchers to give more attention influence of residual deformation and the current climate change, in consideration of the stability and long-term service performance of subgrade under extreme weather conditions in the future.

Correlated frequency noise in a multimode acoustic resonator

Frequency instabilities are a major source of errors in quantum devices. This Letter investigates frequency fluctuations in a surface acoustic wave (SAW) resonator, where reflection coefficients of 14 SAW modes are measured simultaneously for more than 7 h. We report two distinct noise characteristics. Multimode frequency noise caused by interactions with two-level system (TLS) defects shows significant degrees of correlation that diminish with increased detuning. This finding agrees with the current understanding of the parasitic TLS behavior as one of the dominant noise sources in quantum devices. In addition to the TLS-induced noise, we observe strong anomalous frequency fluctuations with slow, anticorrelated dynamics. These noise bursts resemble signatures of cosmic radiation observed in superconducting quantum systems. Published by the American Physical Society 2024

Work hardening and X-ray diffraction studies on ASS 304 at high temperatures

Abstract One of the most common characteristics of metallic alloys is work hardening, which is most beneficial as it is the primary reason for the alloys’ tenacity to withstand loading even in the presence of internal flaws or geometrical errors. Thus, the work hardening coefficient gives the maximum amount of homogeneous plastic deformation in tensile straining. Thus, complex-forming operations are facilitated by a high coefficient without experiencing premature failure. Naturally, work hardening has a significant impact on the mechanical energy required to shape a material by plastic deformation, such as rolling, forming, etc. The quantity of energy that the material stores during plastic deformation is also managed by work hardening. As a result, it significantly influences how the metal behaves when it is subsequently softened during annealing. Finally, the hardening capacity and durability of the work hardened state are significant practical challenges because many high-volume stretch formed components are directly used. Typically, the current study begins, at homologous temperatures above 0.4 times melting point, with a description of work hardening at 700, 800, and 900°C temperatures in three different orientations with respect to rolling direction R 0, R 45, and R 90 and 10−1−10−3 s−1 strain rates, where thermally triggered processes exhibit a prominent role in work hardening. Three stages of behavior were identified by analyzing the tensile work hardening of ASS 304 steel. Dynamic strain aging is the cause of the anomalous fluctuation in the work hardening rate that is seen in hot working temperatures. X-ray diffraction examination is conducted to introspect any phase changes occurring in hot working regions improving plasticity of ASS 304.

A novel battery abnormality diagnosis method using multi-scale normalized coefficient of variation in real-world vehicles

Accurate and efficient diagnosis of battery voltage abnormality is crucial for the safe operation of electric vehicles. This paper proposes an innovative battery voltage abnormality diagnosis method based on a normalized coefficient of variation in real-world electric vehicles. Vehicle and laboratory data are collected and analyzed, with joint preprocessing to improve data quality, and battery voltages are log-transformed to improve the contribution of anomalous voltage fluctuations. The normalized coefficient of variation is proposed to detect the fluctuation inconsistency of cell voltage, and the risk coefficient rule is formulated by Z-score and normalization. Furthermore, the validity and robustness are verified by laboratory and real-world battery faults. The results demonstrate that the optimal slide step and calculation window for real-world under-voltage fault are 10 and 40, and those for laboratory lithium plating and real-world thermal runaway are both 10 and 50, respectively. More importantly, this study introduces a battery abnormality diagnosis strategy based on the vehicle T-box, anticipated to be widely implemented to ensure the safety of real-vehicle operations. This method not only enhances the accuracy and efficiency of detecting electric vehicle battery abnormalities, but also offers a practical solution to prevent battery related faults.

Characteristics of mesoscale eddies in the Mozambique Channel.

The mesoscale eddy characteristics of the Mozambique Warm Current were investigated by detecting and tracking satellite altimetry data from 2010 to 2019. A total of 1,086 eddies were identified in the Mozambique Channel, comprising 509 cyclonic eddies and 577 anticyclonic eddies. The results revealed that the bay area on the northwest coast of Madagascar was the main hotspot of eddy generation, and the mean amplitude and radius of the anticyclonic eddies in the Mozambique Channel were 24.23 cm and 82.7 km, respectively, which are larger than those of the cyclonic eddies. Local wind forcing had a significant impact on the formation of mesoscale eddies in the Mozambique Channel. In winter, the wind stress in the northern and southern areas of the Mozambique Channel exhibited a strong correlation with the distribution of eddy kinetic energy (EKE), where both monsoonal winds in the north and trade winds in the south could facilitate mesoscale anticyclonic eddy formation. In addition, the variability in the number of anticyclonic and cyclonic eddies in the Mozambique Channel may have exerted a significant influence on the seasonal anomalous fluctuations in local sea surface temperatures (SSTs). This study presented a novel analysis of the mesoscale eddy characteristics in the Mozambique Channel.

On the detection, modeling, and mitigation of anomalous QoT fluctuations in optical networks

Monitoring data from deployed backbone networks shows that many lightpaths present large fluctuations of their quality of transmission (QoT), beyond 1 dB in range. In this paper, we investigate the hypothesis that the evidenced fluctuations stem from anomalies in polarization-dependent loss (PDL), equivalent to one large PDL element. We eventually propose and experimentally test a closed-loop automation designed to stabilize the QoT at a maximal level for lightpaths impaired by such a PDL anomaly.

Anomalous Luttinger equivalence between temperature and curved spacetime: From black holes to thermal quenches

Building on the idea of Tolman and Ehrenfest that heat has weight, Luttinger established a deep connection between gravitational fields and thermal transport. However, this relation does not include anomalous quantum fluctuations that become paramount in strongly curved spacetime. In this work, we revisit the celebrated Tolman-Ehrenfest and Luttinger relations and show how to incorporate the quantum energy scales associated with these fluctuations, captured by gravitational anomalies of quantum field theories. We point out that such anomalous fluctuations naturally occur in the quantum atmosphere of a black hole. Our results reveal that analogous fluctuations are also observable in thermal conductors in flat-space time provided local temperature varies strongly. As a consequence, we establish that the gravitational anomalies manifest themselves naturally in non-linear thermal response of a quantum wire. In addition, we propose a systematic way to identify thermal analogues of black hole’s anomalous quantum fluctuations associated to gravitational anomalies. We identify their signatures in propagating energy waves following a thermal quench, as well as in the energy density of heating Floquet states induced by repeated thermal quenches.

Squeezed Ensembles and Anomalous Dynamic Roughening in Interacting Integrable Chains.

It is widely accepted that local subsystems in isolated integrable quantum systems equilibrate to generalized Gibbs ensembles. Here, we identify a particular class of initial states in interacting integrable models that evade canonical generalized thermalization. Particularly, we demonstrate that in the easy-axis regime of the quantum XXZ chain, pure nonequilibrium initial states that lack magnetic fluctuations instead locally relax to squeezed generalized Gibbs ensembles governed by nonlocal equilibrium Hamiltonians, representing exotic equilibrium states with subextensive charge fluctuations that violate the self-affine scaling. At the isotropic point, we find exceptional behavior and explicit dependence on the initial state. Particularly, we find that relaxation from the Néel state is governed by extensive fluctuations and a superdiffusive dynamical exponent compatible with the Kardar-Parisi-Zhang universality. On the other hand, there are other nonfluctuating initial states that display diffusive scaling, e.g., a product state of spin singlets. Our predictions provide examples of anomalous quantum transport and fluctuations in strictly quantum states which can be directly tested in state-of-the-art cold atomic experimental settings.

Universal anomalous fluctuations in charged single-file systems

Introducing a general class of one-dimensional single-file systems (meaning that particle crossings are prohibited) of interacting hardcore particles with internal degrees of freedom (called charge), we exhibit a dynamical universality reflected in anomalous statistical properties of macroscopic fluctuating observables such as charge transfer. We find that stringent dynamical constraints lead to universal anomalous statistics of cumulative charge currents manifested both on the timescale characteristic of typical fluctuations and also in the rate function describing rare events. By computing the full counting statistics of net transferred charge between two extended subsystems, we establish a number of unorthodox dynamical properties in an analytic fashion. Most prominently, typical fluctuations in equilibrium are governed by a universal distribution that markedly deviates from the expected Gaussian statistics, whereas large fluctuations are described by an exotic large-deviation rate function featuring an exceptional triple critical point. Far from equilibrium, competition between dynamical phases leads to dynamical phase transitions of first and second order and spontaneous breaking of fluctuation symmetry of the univariate charge large-deviation function. The rich phenomenology of the outlined dynamical universality is exemplified on an exactly solvable classical cellular automaton of charged hardcore particles. We determine the dynamical phase diagram in the framework of Lee–Yang's theory of phase transitions and exhibit a hyper-dimensional diagram of distinct dynamical regimes. Our findings lead us to conclude that the conventional classification of dynamical universality classes based on the algebraic dynamical exponents and asymptotic scaling functions that characterize hydrodynamic relaxation of the dynamical structure factor is incomplete and calls for refinement. Published by the American Physical Society 2024

Spatiotemporal variations of inter- and intra-annual extreme streamflow in the Yangtze River Basin

Climate change has led to anomalous fluctuations in extreme streamflow from global river systems, and the superposition of human activities such as damming has compounded the changes in extreme streamflow, affecting floods and river ecosystems. However, muti-temporal scale variations of extreme streamflow and the dominant driving factors were limitedly understood. In this study, we examined the changing patterns of inter- and intra-annual extreme (maximum 1-day, consecutive 3-days and 7-days) streamflow (including magnitude and timing) in the Yangtze River Basin (YRB) from the 1940 s to 2020. Furthermore, the roles of ENSO events and dams on temporal anomalies of extreme streamflow at inter- and intra-annual scales were identified in the whole basin. We found that the annual streamflow extremes increased in the source YRB and the middle and lower YRB but decreased in the upper YRB. The extreme streamflow during spring and autumn was characterized by increasing trends in the source and decreasing trends in other reaches. The occurrence timing of winter extreme streamflow in the upper and middle YRB was significantly delayed. The inter-annual extreme streamflow in the source and upper YRB had a negative relationship with ENSO, while the positive relationship held in the middle and lower YRB. The major anomalies (>50 %) of annual extreme streamflow generally occurred in ENSO (1+2) yrs, while precipitation contributes to the seasonal distribution of extreme streamflow. There was a good correlation between precipitation and both annual and summer extreme streamflow in the lower YRB, but the relationship completely shifted in the upper YRB after 2003. Further, the construction of dams has severely affected extreme streamflow, leading to a stepwise drop in annual and summer/autumn flows and a sudden rise in spring/winter flows. This study facilitates the prediction of extreme streamflow and the development of sustainable basin management strategies.

Metamagnetic fluctuation characteristics near dynamic phase transitions.

We experimentally explore the magnetization dynamics of thin ferromagnetic Co films with uniaxial in-plane anisotropy near the dynamic phase transition (DPT) and, in particular, we study the temporal characteristics of anomalous metamagnetic fluctuations that occur in its vicinity, and for which no thermodynamic equivalent exists. For this purpose, we measure the real-time evolution of magnetization trajectories in the relevant dynamic phase space, conduct a Fourier analysis of these experimental results and compare it to a model, in which the fluctuating metamagnetic behavior occurs in a purely random manner, following individual state probability distributions. We find excellent quantitative agreement in between our experimental results and the random state model, clearly indicating that multiperiod time-correlations of magnetic states are not relevant in our DPT system, not even for the occurrence of the anomalous metamagnetic fluctuations that are nonetheless associated with nonperiodic magnetic state evolutions.

MTTF: a multimodal transformer for temperature forecasting

Accurate weather forecasting is crucial for various applications, including agriculture and environmental monitoring. However, existing deep learning based methods typically use only temperature observations as input, which do not consider spatial location (e.g. neighboring regions usually show similar temperature trends) and increase the difficulty in predicting anomalous fluctuations in temperature. To address the issue, a multimodal transformer model for temperature forecasting is proposed. This model not only uses observational data (time series data) as input but also incorporates spatially rich ERA5 reanalysis temperature data (spatio-temporal data). The proposed method has two distinctive features: (1) a sequence merging module to highlight dominating features and reduce the cost of attention calculations. (2) a cross-all-modal attention mechanism to capture dependencies between the current modality and all modalities. The method was evaluated on three temperature datasets from a plain and two challenging high-altitude mountainous regions. Results showed that the proposed method outperforms existing methods in terms of MAE and MSE, offering a promising new solution for temperature prediction. Our code and data are available at https://github.com/Adam618/MTTF.

Energy transfer of imbalanced Alfvénic turbulence in the heliosphere

Imbalanced Alfvénic turbulence is a universal process playing a crucial role in energy transfer in space, astrophysical, and laboratory plasmas. A fundamental and long-lasting question about the imbalanced Alfvénic turbulence is how and through which mechanism the energy transfers between scales. Here, we show that the energy transfer of imbalanced Alfvénic turbulence is completed by coherent interactions between Alfvén waves and co-propagating anomalous fluctuations. These anomalous fluctuations are generated by nonlinear couplings instead of linear reflection. We also reveal that the energy transfer of the waves and the anomalous fluctuations is carried out mainly through local-scale and large-scale nonlinear interactions, respectively, responsible for their bifurcated power-law spectra. This work unveils the energy transfer physics of imbalanced Alfvénic turbulence, and advances the understanding of imbalanced Alfvénic turbulence observed by Parker Solar Probe in the inner heliosphere.

Generalized disorder averages and current fluctuations in run and tumble particles.

We present exact results for the fluctuations in the number of particles crossing the origin up to time t in a collection of noninteracting run and tumble particles in one dimension. In contrast to passive systems, such active particles are endowed with two inherent degrees of freedom, positions and velocities, which can be used to construct density and magnetization fields. We introduce generalized disorder averages associated with both these fields and perform annealed and quenched averages over various initial conditions. We show that the variance σ^{2} of the current in annealed versus quenched magnetization situations exhibits a surprising difference at short times, σ^{2}∼t vs σ^{2}∼t^{2}, respectively, with a sqrt[t] behavior emerging at large times. Our analytical results demonstrate that in the strictly quenched scenario, where both the density and magnetization fields are initially frozen, the fluctuations in the current are strongly suppressed. Importantly, these anomalous fluctuations cannot be obtained solely by freezing the density field.

Statistics of the number of renewals, occupation times, and correlation in ordinary, equilibrium, and aging alternating renewal processes.

The renewal process is a point process where an interevent time between successive renewals is an independent and identically distributed random variable. Alternating renewal process is a dichotomous process and a slight generalization of the renewal process, where the interevent time distribution alternates between two distributions. We investigate statistical properties of the number of renewals and occupation times for one of the two states in alternating renewal processes. When both means of the interevent times are finite, the alternating renewal process can reach an equilibrium. On the other hand, an alternating renewal process shows aging when one of the means diverges. We provide analytical calculations for the moments of the number of renewals, occupation time statistics, and the correlation function for several case studies in the interevent-time distributions. We show anomalous fluctuations for the number of renewals and occupation times when the second moment of interevent time diverges. When the mean interevent time diverges, distributional limit theorems for the number of events and occupation times are shown analytically. These are known as the Mittag-Leffler distribution and the generalized arcsine law in probability theory.