Field Structure Research Articles

Single versus Double Plate Fixation in Condylar Neck Fractures: Clinical Results and Biomechanics Simulation.

The open reduction of mandibular condyle neck fractures is difficult due to the limited surgical field and complex facial nerve structures. The most effective fixation method for narrow fractured segments is debated as standard double four-hole plate fixation is often not feasible. This research compared bone stability and force resistance between single-long-plate and double-short-plate fixations using clinical outcomes, a Sawbones mandible model, and finite element analysis. In patients with condyle neck fractures, nine were fixed with single-long-plate and twelve with double-short-plate fixations, with no significant differences in malocclusion and facial palsy rates. In compression tests with a Sawbones model, displacements in the posterior part were similar in both fixation groups. In contrast, the anterior part had significantly higher displacements in the single-long-plate group. Finite element analysis showed higher displacements in both anterior and posterior parts in the single-plate group compared to the double-short-plate group. Maximum stresses were at the second screw hole in single-long-plate fixation and the turning point of the upper plate at the condyle neck in double-short-plate fixation. Double-short-plate fixations demonstrated better stability and force resistance than single-long-plate fixations.

Numerical simulations of a stochastic dynamics leading to cascades and loss of regularity: Applications to fluid turbulence and generation of fractional Gaussian fields

Motivated by the modeling of the spatial structure of the velocity field of three-dimensional turbulent flows, and the phenomenology of cascade phenomena, a linear dynamics was recently proposed that can generate high velocity gradients from a smooth-in-space forcing term. It is based on a linear partial differential equation stirred by an additive random forcing term that is δ-correlated in time. The underlying proposed deterministic mechanism corresponds to a transport in Fourier space that aims to transfer energy injected at large scales towards small scales. The key role of the random forcing is to realize these transfers in a statistically homogeneous way. Whereas at finite times and positive viscosity the solutions are smooth, a loss of regularity is observed for the statistically stationary state in the inviscid limit. We present here simulations, based on finite volume methods in the Fourier domain and a splitting method in time, which are more accurate than the pseudospectral simulations. We show that our algorithm is able to reproduce accurately the expected local and statistical structure of the predicted solutions. We conduct numerical simulations in one, two, and three spatial dimensions, and we display the solutions both in physical and Fourier space. We additionally display key statistical quantities such as second-order structure functions and power spectral densities at various viscosities. Published by the American Physical Society 2024

Two-Field Excitation for Contactless Inductive Flow Tomography.

Contactless inductive flow tomography (CIFT) is a flow measurement technique allowing for visualization of the global flow in electrically conducting fluids. The method is based on the principle of induction by motion: very weak induced magnetic fields arise from the fluid motion under the influence of a primary excitation magnetic field and can be measured precisely outside of the fluid volume. The structure of the causative flow field can be reconstructed from the induced magnetic field values by solving the according linear inverse problem using appropriate regularization methods. The concurrent use of more than one excitation magnetic field is necessary to fully reconstruct three-dimensional liquid metal flows. In our laboratory demonstrator experiment, we impose two excitation magnetic fields perpendicular to each other to a mechanically driven flow of the liquid metal alloy GaInSn. In the first approach, the excitation fields are multiplexed. Here, the temporal resolution of the measurement needs to be kept as high as possible. Consecutive application by multiplexing enables determining the flow structure in the liquid with a temporal resolution down to 3 s with the existing equipment. In another approach, we concurrently apply two sinusoidal excitation fields with different frequencies. The signals are disentangled on the basis of the lock-in principle, enabling a successful reconstruction of the liquid metal flow.

Interaction of acoustic pressure and heat release rate fluctuations in a model rocket engine combustor.

We experimentally clarify the interaction of acoustic pressure and heat release rate fluctuations during a transition to high-frequency combustion instability in a model rocket engine combustor. The dynamical state of acoustic pressure fluctuations undergoes a transition from high-dimensional chaotic oscillations to strongly correlated limit cycle oscillations. The coherent structure in the heat release rate field emerges with the initiation of weakly correlated limit cycle oscillations. The effect of the heat release rate on acoustic pressure fluctuations predominates during high-dimensional chaotic oscillations. In contrast, the effect of acoustic pressure on the heat release rate fluctuations markedly increases during the correlated limit cycle oscillations. These are reasonably shown by an ordinal pattern-based analysis involving the concepts of information theory, synchronization, and complex networks.

Effect of bridge height on airflow and aeolian sand flux near surface along the Qinghai-Tibet Railway, China

In this work, we studied the near-surface flow field structure of railway bridges with different heights through field investigation and wind tunnel simulation experiments. Meanwhile, we simulated the distribution of sand accumulation around a bridge via CFD software based on the sand accumulation around the Basuoqu bridge in the Cuona Lake section of the Qinghai–Tibet Railway. Results show that the sand around this railway bridge is mainly from the lake sediment on the west side of the railway and the weathered detritus on the east side. The height of the railway bridge in the sandy area affects the distribution of the near-surface flow field and the variation in speed on both sides of the bridge. The wind speed trough on both sides of the 6 m high bridge is higher, and the horizontal distance between the wind speed trough and the bridge section is 1.5 times that of the 3 m high bridge. Wind speed attenuates in a certain range on the windward and leeward sides of the bridge, forming an aeolian area; under the beam body, it is affected by the narrow tube effect, forming a wind erosion area. The height of the bridge determines its sand transport capacity. Under certain wind conditions, the overhead area at the bottom of the 3 m high bridge and its two sides do not have the sand transport capacity, so sand accumulates easily. Nevertheless, the sand accumulation phenomenon gradually disappears with the increase in bridge clearance height. The objectives of this study are to reveal the formation mechanism of sand damage for railway bridges, provide theoretical support for the scientific design of railway bridges in sandy areas, and formulate reasonable railway sand prevention measures to ensure the safety of railway running, which have certain theoretical significance and practical value.

High-resolution relative paleointensities over the last 40 ka from marine sediments in the western equatorial pacific: Magnetic events and interhemispheric correlation

Core MD01-2385 retrieved in the western equatorial Pacific (Northwest of Papua-New Guinea) has been sampled every 2 cm for paleomagnetic and radiocarbon measurements. The age model, well constrained by 47 14C ages (both new and former), indicates that our record spans approximately the last 38 ka. The average sedimentation rate is ∼30 cm/ka. Analysis of the magnetic mineralogy revealed that the natural remanent magnetization (NRM) is predominantly carried by magnetite. A relative paleointensity record (RPI) was derived, allowing us to estimate a lock-in depth of approximately 18 cm, corresponding to ∼600 years in our case, by comparing it with the CALS10k.2 model. Comparison with two other western Equatorial Pacific RPI, selected for their geographical proximity (∼1000 km) and high resolution, allowed us to compile a regional reference record (WEPEQ). Several intervals of lower intensities have been identified and may correspond to the known events of Mono Lake (∼34 ka), Rockall (∼27 ka), Hilina Pali (∼18 ka) and possibly Tianchi (∼5–8 ka). Overall, our equatorial curve exhibits strong similarities with RPI curves from mid to low latitudes, such as those from the Iberian Margin and Black Sea. A detailed investigation hints at the presence of non-dipolar structures in the Earth's magnetic field at the shorter time scale, especially during the low intensity intervals. In contrast, notable differences are observed when compared to high-latitude stacks, especially from the North Atlantic (NAPIS). This points to the potential climatic bias that may affect high-latitude records during the glacial maximum and glacial-interglacial transition.

Examining the ability of big data analytics to investigate financial reporting quality: a comprehensive bibliometric analysis

Purpose This study aims to examine the ability of big data analytics (BDA) to investigate financial reporting quality (FRQ), identify the knowledge base and conceptual structure of this research field and explore BDA techniques used over time. Design/methodology/approach This study uses a comprehensive bibliometric analysis approach (performance analysis and science mapping) using software packages, including Biblioshiny and VOSviewer. Multiple analyses are conducted, including authors, sources, keywords, co-citations, thematic evolution and trend topic analysis. Findings This study reveals that the intellectual structure of using BDA in investigating FRQ encompasses three clusters. These clusters include applying data mining to detect financial reporting fraud (FRF), using machine learning (ML) to examine FRQ and detecting earnings management as a measure of FRQ. Additionally, the results demonstrate that ML and DM algorithms are the most effective techniques for investigating FRQ by providing various prediction and detection models of FRF and EM. Moreover, BDA offers text mining techniques to detect managerial fraud in narrative reports. The findings indicate that artificial intelligence, deep learning and ML are currently trending methods and are expected to continue in the coming years. Originality/value To the best of the authors’ knowledge, this study is the first to provide a comprehensive analysis of the current state of the use of BDA in investigating FRQ.

Mode Transition Of A Flexible Film Motion In The Circular Cylinder Wake

The fluid-structure interaction between a flexible film and the wake of a circular cylinder is an abstract of a series of natural phenomena like flag flapping and fish swimming. Diverse patterns of both solid deformation and fluid dynamics arise in this coupling system as the nondimensional parameters are varied. In our recent experiments, we find that beyond the extensively studied periodic coupling process, irregular processes also emerge in this system under specific conditions. However, due to the complexity inherent in the irregular coupling processes, no in-depth investigation into this topic is available yet. In this work, we delve into the irregular aperiodic flutter of a flexible film behind a circular cylinder in the uniform flow as well as the related irregular evolution of flow structures. Two representative cases of film streamwise length (L/D) pertinent to the irregular process, specifically L/D=3 and L/D=4, have been investigated experimentally in the wind tunnel with time-resolved synchronized measurements of both film deformation and flow field. Continuous wavelet transform and virtual dye visualization are employed to extract the time-frequency characteristics of film motion and Lagrangian coherent structures in the flow fields during the film’s irregular flutter, respectively. It is determined that the irregular flutter is aperiodic in terms of the overall view, but it also encompasses transient quasi-periodic stages as its motion modes alter. Hence, we term this irregular flutter as the “hybrid flutter” state. In the quasi-periodic stages of the hybrid flutter, the large-scale vortex structures are periodically formed on the surfaces of the film and evolve in the wake as a Kármán vortex street. The periodic formation of large-scale vortices exerts periodic alternating force on the film, which, therefore, leads to the quasi-periodic flutter of the film with the second-order mode. By comparison, the aperiodic stage entails the significant extension of the separated shear layers in such a way that the whole film is enveloped by the shear layers; then, large-scale vortices are formed downstream of the film’s trailing edge. In this scenario, no periodic force is acted on the film; as a result, the film flutters aperiodically with the first-order mode.

Towards Time-Resolved Multi-Property Measurements By Single-Frequency FRS

The filtered Rayleigh scattering technique (FRS), extended by the method of frequency scanning, has historically been limited to time-averaged multi-property flow measurements. In our recently published work, we present a concept that potentially enables the combined measurement of time-resolved pressure, temperature and three-component (3C) velocity fields. It is based on the observation of the region of interest from six perspectives and a single excitation frequency. This work summarizes and expands on a follow-up publication that experimentally verifies this concept on an aspirated circular duct flow. For this purpose, the results obtained from single-frequency data processing are compared with reference pressures, temperatures and corresponding LDA velocity measurements. Overall, a very good agreement is found for all operating points with accuracies of 3.4% in pressure, 1.3% in temperature and ±2 m/s in axial velocity. Concerning precision, a newly developed multistage evaluation procedure enables values for pressure, temperature and velocity as low as 3 hPa, 2.2 K and 1.7 m/s. In a second flow configuration, an axial swirler is introduced into the duct. The resulting secondary flow structure and deformation of the axial velocity field caused by swirler geometry and support are very well captured with the single-frequency analysis. A closing discussion on the implementation challenges of a single-frequency multi-property FRS instrument with pulsed laser radiation reveals significant obstacles to overcome. Due the considerable optimization potential identified, chances are high that true time-resolved multi-property measurements by FRS will become a reality.

First and Second Reductions in an Aprotic Solvent: Comparing Computational and Experimental One-Electron Reduction Potentials for 345 Quinones.

Using reference reduction potentials of quinones recently measured relative to the saturated calomel electrode (SCE) in N,N-dimethylformamide (DMF), we benchmark absolute one-electron reduction potentials computed for 345 Q/Q•- and 265 Q•-/Q2- half-reactions using adiabatic electron affinities computed with density functional theory and solvation energies computed with four continuum solvation models: IEF-PCM, C-PCM, COSMO, and SM12. Regression analyses indicate a strong linear correlation between experimental and absolute computed Q/Q•- reduction potentials with Pearson's correlation coefficient (r) between 0.95 and 0.96 and the mean absolute error (MAE) relative to the linear fit between 83.29 and 89.51 mV for different solvation methods when the slope of the regression is constrained to 1. The same analysis for Q•-/Q2- gave a linear regression with r between 0.74 and 0.90 and MAE between 95.87 and 144.53 mV, respectively. The y-intercept values obtained from the linear regressions are in good agreement with the range of absolute reduction potentials reported in the literature for the SCE but reveal several sources of systematic error. The y-intercepts from Q•-/Q2- calculations are lower than those from Q/Q•- by around 320-410 mV for IEF-PCM, C-PCM, and SM12 compared to 210 mV for COSMO. Systematic errors also arise between molecules having different ring sizes (benzoquinones, naphthoquinones, and anthraquinones) and different substituents (titratable vs nontitratable). SCF convergence issues were found to be a source of random error that was slightly reduced by directly optimizing the solute structure in the continuum solvent reaction field. While SM12 MAEs were lower than those of the other solvation models for Q/Q•-, SM12 had larger MAEs for Q•-/Q2- pointing to a larger error when describing multiply charged anions in DMF. Altogether, the results highlight the advantages of, and further need for, testing computational methods using a large experimental data set that is not skewed (e.g., having more titratable than nontitratable substituents on different parent groups or vice versa) to help further distinguish between sources of random and systematic errors in the calculations.

SCAPS-1D simulation and First-principles calculation of CsSnCl3 hole transport layer-free perovskite solar cells based on gradient doping

As the photovoltaic industry continues to evolve perovskite materials that are inorganic, non-toxic, and do not require a hole transport layer are particularly promising. However, such perovskite solar cells (PSCs) generally do not perform well. Therefore, we propose a gradient doped CsSnCl3 PSCs without hole transport layer (HTL) and investigate the optical and electrical properties of its absorption layer using first principles calculations. We further simulate and optimize this PSCs using SCAPS-1D software, focusing on various factors such as charge transport layer materials, perovskite layer thickness, doping concentration, and working temperature. Our comprehensive analysis also takes changes in the internal electric field and band structure in consideration. The study's results demonstrate that gradient doping creates an additional electric field, significantly improving the solar cell's photovoltaic conversion efficiency. When G=100, even with only two sublayers of gradient doping, a considerable performance boost is observed. The performance of optimized device is as follows: Voc = 1.1841 V, Jsc = 30.13298 mA/cm2, FF = 90.08 %, and PCE = 32.14 %. Compared with the initial PSC's efficiency of 13.93 %, it has significantly improved by 130.7 %. This research provides unique insights and guidance for the future design and manufacture of efficient, all-inorganic, non-toxic PSCs HTL-free.

Multipoint study of the rapid filament evolution during a confined C2 flare on 28 March 2022, leading to eruption

This study focuses on the rapid evolution of the solar filament in active region 12975 during a confined C2 flare on 28 March 2022, which finally led to an eruptive M4 flare 1.5 h later. The event is characterized by the apparent breakup of the filament, the disappearance of its southern half, and the flow of the remaining filament plasma into a new, longer channel with a topology very similar to an extreme ultraviolet (EUV) hot channel observed during the flare. In addition, we outline the emergence of the original filament from a sheared arcade and discuss possible drivers for its rise and eruption. We took advantage of Solar Orbiter's favorable position, 0.33 AU from the Sun, and $83. 5^ west of the Sun-Earth line, to perform a multi-point study using the Spectrometer Telescope for Imaging X-rays (STIX) and the Extreme Ultraviolet Imager (EUI) in combination with the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) and Halpha images from the Earth-based Kanzelhöhe Observatory for Solar and Environmental Research (KSO) and the Global Oscillation Network Group (GONG). While STIX and EUI observed the flare and the filament's rise from close up and at the limb, AIA and HMI observations provided highly complementary on-disk observations from which we derived differential emission measure (DEM) maps and nonlinear force-free (NLFF) magnetic field extrapolations. According to our pre-flare NLFF extrapolation, field lines corresponding to both filament channels existed in close proximity before the flare. We propose a loop-loop reconnection scenario based on field structures associated with the AIA 1600 Å flare ribbons and kernels. It involves field lines surrounding and passing beneath the shorter filament channel, and field lines closely following the southern part of the longer channel. Reconnection occurs in an essentially vertical current sheet at a polarity inversion line (PIL) below the breakup region, which enables the formation of the flare loop arcade and EUV hot channel. This scenario is supported by concentrated currents and free magnetic energy built up by antiparallel flows along the PIL before the flare, and by non-thermal X-ray emission observed from the reconnection region. The reconnection probably propagated to involve the original filament itself, leading to its breakup and new geometry. This reconnection geometry also provides a general mechanism for the formation of the long filament channel and realizes the concept of tether cutting. It was probably active throughout the filament's continuous rise phase, which lasted from at least 30 min before the C2 flare until the filament eruption. The C2 flare represents a period of fast reconnection during this otherwise more steady period, during which most of the original filament was reconnected and joined the longer channel. These results demonstrate how rapid changes in solar filament topology can be driven by loop-loop reconnection with nearby field structures, and how this can be part of a long-lasting tether-cutting reconnection process. They also illustrate how a confined precursor flare due to loop-loop reconnection (Type I) can contribute to the evolution towards a full eruption, and that they can produce a flare loop arcade when the contact region between interacting loop systems has a sheet-like geometry similar to a flare current sheet.

Effect of inlet water vapor mass fraction on flow characteristics in Laval nozzle

Abstract The Laval nozzle is an important component of the supersonic cyclone to achieve the change of gas–liquid two-phase, and the condensation characteristics of the Laval nozzle have an important influence on the separation performance of the supersonic cyclone. In this work, the effect of inlet water vapor mass fraction on the condensation characteristics in the Laval nozzle was investigated using numerical simulation and experimental methods by establishing a three-dimensional numerical model of air-water vapor supersonic condensation flow. The flow field structures in the Laval nozzle under different inlet water vapor mass fractions were investigated, including Mach number, pressure, and temperature and the effects of the inlet water vapor mass fraction on the liquefaction characteristics in the Laval nozzle were investigated. In addition, the droplet distribution in the Laval nozzle were also tested by a particle image velocimetry (PIV) experimental system. The comparison of simulation and experimental results indicates that the numerical model established in this work can effectively describe the real flow situation in the Laval nozzle. The results show that the inlet water vapor mass fraction has a little effect on the flow field structure in the Laval nozzle, and has the significant impact on the water vapor condensation characteristics. With increasing the inlet steam mass fraction from 5 % to 12.5 %, the nucleation rate, droplet number, and separation efficiency in the Laval nozzle increase to 4.05 × 1021 kg−1 s−1, 3.67 × 1014 kg−1, and 79.4 %, respectively, and when further increasing the inlet steam mass fraction to 15 %, these parameters decrease.

Experimental study of the vertical structure of internal solitary waves in the continuous pycnocline

In order to reveal the complex structural characteristics of internal solitary waves (ISWs) in the actual ocean, an experimental study of the vertical structure of ISWs in the continuous pycnocline (a transition layer with sharp density changes) was conducted in a stratified fluid flume. The gravity collapse method was used to generate ISWs, and their wave-flow fields were measured using a coupled wave-flow measurement technique. The vertical structure of wave-flow fields was investigated as was the applicability of the Dubreil–Jacotin–Long (DJL) equation. The results show that the waveform of ISWs contains multiple isodensity lines that varied with fluid depth. The wave amplitude and wavelength of ISWs exhibited depth-dependent changes, which were negatively correlated. The vertical structure of the flow fields exhibited an approximate circular wave packet, with stronger horizontal flow than vertical flow. The larger the characteristic amplitude, the stronger the intensity of the flow field, and the faster the intensity of the vertical flow field increased. The applicability of the DJL equation was closely related to the stratified environment, with better agreement when the upper layer fluid constituted a larger ratio of the total fluid thickness.

Analysis of the structure of the information field of perception of risk factors for non-communicable diseases

When studying the attitude of the population to saving their own health, the question of the connection between abstract knowledge about the harm caused to health by risk factors and a real understanding of the harm caused by these factors to their own health remains poorly understood.The purpose of this work is to analyze the structure of the information field of the population’s attitude to the impact of FR on health.Materials and methods. The material for the analysis was the results of a sociological survey in three pilot regions of the Russian Federation – Tula Region, Stavropol Territory and the Republic of Crimea. The questionnaire consisted of 33 questions concerning risk factors and their impact on the human body and a block of questions concerning sources of medical information and trust in them. The sample size was 1,718 respondents. The following methods were used: descriptive statistics and the sociological method of questioning. Statistical data processing and reweighing were carried out in the statistical data processing package SPSS22.0. In general, the sampling error in the study does not exceed 1.99% for a confidence level of p<0.1.Results. The study showed that abstract knowledge about the harm of a particular FR in almost all FR is quite high, since it is precisely on them that the efforts of the medical community have been directed in recent decades. Moreover, the highest values are expected to have such factors as tobacco use, alcohol consumption, elevated blood sugar (glucose) and high blood pressure. The level of knowledge of the harm of FR, to which the medical community paid less attention, was expected to be lower. The lowest value is such a FR as a low iodine content in salt, which is consumed in food. An assessment of the relationship of variables such as abstract knowledge of harm about FR and understanding of their harm to one’s body using a two-way T-criterion showed that these variables are completely independent of each other at the significance level p<0.001. This result made us look more closely at the factor structure of the studied field of reality and put forward the assumption of independence of knowledge about the harm caused to the human body by FR and behavioral patterns in relation to FR. As a result of factor analysis of 73 variables, 9 factors were identified: the first and most powerful factor (10.33%) – knowledge of the effect of FR on one’s own health; the second most powerful factor (8.71%) – knowledge of the harm of FR; the third highlighted factor (5.46%) – trust in information sources, which included both trust in the media and trust in TV presenters, popular personalities and trust in the leaders of the region and the city; the fourth highlighted factor (4.67%) is the gender characteristics of the control of the FR by the population; the fifth highlighted factor (4.59%) is the sources of information about the FR; the sixth highlighted factor (4.30%) – age–related features of FR control; the seventh highlighted factor (3.32%) – the use of gadgets to control FR and exercise; the eighth highlighted factor (3.00%) – trust in health workers as a source of information; the ninth highlighted factor (2.59%) – smoking and alcohol consumption.Conclusion. The assessment of the effect of FR on the respondents’ own health in the framework of the conducted study turned out to be significantly lower than abstract knowledge about the harmful effects of these FR. The analysis of the factor structure of the studied field confirmed the validity of such a division of knowledge based on ideas about its various forms – «knowledge in itself» and «knowledge for oneself». The analysis made it possible to formulate a number of conditions for improving the effectiveness of preventive work with the population, including to increase the impact of population prevention: it is necessary to more actively involve the most important sources for the population – medical workers, scientific medical workers and health managers; more fully take into account the gender and age characteristics of audiences in preventive measures; the use of mass media should be preceded by an analysis of the level of trust in them from the target audience; the information messages themselves must first be checked for memorability. Preventive measures should change the personal meanings of specific people in relation to FR and HLS, and not be limited to stating general knowledge about them. The study also allows us to determine the directions for further research of the population’s attitude to the FR and their own health as an interdisciplinary task with the necessary involvement of specialists in medical and general psychology, personality psychology and motivation psychology, as well as sociologists.

Model order reduction by convex displacement interpolation

We present a nonlinear interpolation technique for parametric fields that exploits optimal transportation of coherent structures of the solution to achieve accurate performance. The approach generalizes the nonlinear interpolation procedure introduced in [Iollo, Taddei, J. Comput. Phys., 2022] to multi-dimensional parameter domains and to datasets of several snapshots. Given a library of high-fidelity simulations, we rely on a scalar testing function and on a point set registration method to identify coherent structures of the solution field in the form of sorted point clouds. Given a new parameter value, we exploit a regression method to predict the new point cloud; then, we resort to a boundary-aware registration technique to define bijective mappings that deform the new point cloud into the point clouds of the neighboring elements of the dataset, while preserving the boundary of the domain; finally, we define the estimate as a weighted combination of modes obtained by composing the neighboring snapshots with the previously-built mappings. We present several numerical examples for compressible and incompressible, viscous and inviscid flows to demonstrate the accuracy of the method. Furthermore, we employ the nonlinear interpolation procedure to augment the dataset of simulations for linear-subspace projection-based model reduction: our data augmentation procedure is designed to reduce offline costs — which are dominated by snapshot generation — of model reduction techniques for nonlinear advection-dominated problems.

Manipulating the community structure of arthropods in rice fields with floral resources plants

Abstract Conservation biological control encourages natural enemies to suppress target pests through manipulation of environmental factors that influence natural enemy survival and effectiveness, including microclimates, availability of food for adults and alternative prey, and shelter from adverse environmental conditions. This study aimed to identify selective flowering plants that could be used to manipulate the arthropod community structure in rice fields. Three rice fields (a field without resources of flowering plants, a field with vegetable crop, and a field with ornamental plant) were used in this experiment. The flowering plants included Helianthus sp., Catharanthus roseus, and Cosmos sulphureus while the vegetable plants included eggplant, cucumber, and long beans. Arthropod recording was carried out by direct observation and yellow pan traps from 14 to 98 days after planting. We recorded 33,728 arthropods representing 153 species in 68 families, 13 orders, and 2 classes. The presence of flowering plant significantly affects abundance, species richness, diversity index, and evenness of arthropods both in dry and wet seasons. The rice field surrounded with ornamental plants or vegetables showed the lowest abundance of phytophagous arthropods, the highest abundance of parasitoid and predatory arthropods. Therefore, vegetable crops such as cucumber, long beans and eggplant have great opportunities as refugia in rice fields.

Seismicity in the Weiyuan-Rongxian area, Sichuan basin, SW China

The Weiyuan-Rongxian shale gas field in the Sichuan basin, China, has experienced numerous earthquakes in recent years, causing significant casualties and property loss. To investigate the spatial–temporal evolution of seismicity and seismic fault structures, in this study, we first utilize a deep-learning-based picking algorithm –(PhaseNet) to identify seismic phases from raw seismic data between March 2019 and October 2020, and then employ a Rapid Earthquake Association and Location technique (REAL) to associate these seismic picks. Finally, the VELEST and GrowClust methods are performed to build a high-precision earthquake catalog containing 18,912 earthquakes. Our results reveal that the spatial–temporal distribution of earthquake swarms indicates a complex fault system. In the northern part of Weidong block (R1), the earthquakes illuminate a shovel-shaped structure that the dip angle of the fault plane gradually decreases with depth. In the south of Weidong block (R2), the natural fractures with dip angles of about 80° control the distribution pattern of earthquakes. In the Weixi block (R3), the Molin fault and basement fault form a typical structural wedge that bounds a triangular or wedge-shaped fault block. The majority of earthquakes located below the buried depth of the shale gas and spatio-temporal correlations between seismicity and industry operations both suggest that they are probably induced by hydraulic fracturing. The migration front of the earthquakes can be modeled by fluid diffusion with the diffusivity D between 0.2 m2/s and 3.5 m2/s. The Ms 5.2 earthquake occurring on 18 December 2019 is located in a positive ∼10 kpa Coulomb failure stress area generated by the 8 September 2019, Ms 5.4 earthquake, reaching the typical static triggering threshold. Therefore, in addition to fluid diffusion, the stress perturbation caused by previous seismic ruptures may be considered as another factor of earthquakes occurring in the Weiyuan-Rongxian. Our study provides evidences for better understanding the seismicity characteristics, seismogenic mechanism, and fault structure in Weiyuan-Rongxian shale gas field.

Coastal current convergence structures in the Bay of Biscay from optimized high-frequency radar and satellite data

The southeastern Bay of Biscay has been described as a “dead end” for floating marine litter, often accumulating along small-scale linear streaks. Coastal Current Convergence Structures (CCS), often associated with vertical motions at river plume edges, estuarine fronts, or other physical processes, can be at the origin of the accumulation. Understanding the formation of CCS and their role in the transport of marine litter is essential to better quantify and to help mitigate marine litter pollution. The Lagrangian framework, used to estimate the absolute dispersion, and the finite-size Lyapunov exponents (FSLE), have proved very effective for identifying CCS in the current velocity field. However, the quality of CCS identification depends strongly on the Eulerian fields. Two surface current velocity data sets were used in the analysis: the remotely sensed velocities from the EuskOOS High-Frequency Radar (HFR) network and velocities from three-dimensional model outputs. They were complemented by drifting buoy velocity measurements. An optimization method, involving the fusion of drifting buoys and HFR velocities is proposed to better reconstruct the fine-scale structure of the current velocity field. Merging these two sources of velocity data reduced the mean Lagrangian error and the Root Mean Square Error (RMSE) by 50 % and 30 % respectively, significantly improving velocity reconstruction. FSLE ridgelines obtained from the Lagrangian analysis of optimized velocities were compared with remotely sensed concentrations of Chlorophyll-a. It was shown that ridgelines control the spatial distribution of phytoplankton. They fundamentally represent the CCS which can potentially affect marine litter aggregation. Analysis of the absolute dispersion revealed large stirring in the alongshore direction which was also confirmed by spatial distribution of FSLE ridgelines. The alignment between FSLE ridgelines and patterns of high Chlorophyll-a concentration was observed, often determining the limits of river plume expansion in the study area.

A scaling region identification method for the divider dimension of urban thermal environments

Abstract A scaling region identification method for divider dimensions using the coefficient of determination is proposed to improve the estimation accuracy of the divider dimension in the study of urban thermal environment differentiation characteristics. The effectiveness of this method was verified by analyzing the urban surface thermal field differentiation characteristics by applying the estimated divider dimensions of Nanjing’s thermal environment surfaces and transect lines. The research results show that the urban thermal environment has fractal characteristics only within a certain temperature threshold range. When the constraint of scaling regions is considered, the calculated divider dimension of the surface thermal field surface increases, reflecting the more complex fractal structure of the thermal field. For each temperature grade, the “trough” position of the thermal field divider dimension surface estimated by the line-divider method is near the determination level of the high-temperature region based on robust statistics, allowing the spatial extent of the urban heat island (UHI) to be determined based on the “trough” feature of the thermal field divider dimension surface.