Temporal Evolution Research Articles

Extended Shock Breakout and Early Circumstellar Interaction in SN 2024ggi

We present high-cadence photometric and spectroscopic observations of supernova (SN) 2024ggi, a Type II SN with flash spectroscopy features, which exploded in the nearby galaxy NGC 3621 at ∼7 Mpc. The light-curve evolution over the first 30 hr can be fit by two power-law indices with a break after 22 hr, rising from M V ≈ −12.95 mag at +0.66 day to M V ≈ −17.91 mag after 7 days. In addition, the densely sampled color curve shows a strong blueward evolution over the first few days and then behaves as a normal SN II with a redward evolution as the ejecta cool. Such deviations could be due to interaction with circumstellar material (CSM). Early high- and low-resolution spectra clearly show high-ionization flash features from the first spectrum to +3.42 days after the explosion. From the high-resolution spectra, we calculate the CSM velocity to be 37 ± 4 km s−1. We also see the line strength evolve rapidly from 1.22 to 1.49 days in the earliest high-resolution spectra. Comparison of the low-resolution spectra with CMFGEN models suggests that the pre-explosion mass-loss rate of SN 2024ggi falls in the range of 10−3–10−2 M ☉ yr−1, which is similar to that derived for SN 2023ixf. However, the rapid temporal evolution of the narrow lines in the spectra of SN 2024ggi (R CSM ∼ 2.7 × 1014 cm) could indicate a smaller spatial extent of the CSM than in SN 2023ixf (R CSM ∼ 5.4 × 1014 cm), which in turn implies a lower total CSM mass for SN 2024ggi.

Enhanced erosion and silicate weathering of the West African craton during the late Cretaceous cooling evidenced by mineralogical and Hf[sbnd]Nd isotope proxies

The evolution of oceanic temperatures between the Turonian and the K/T boundary indicates a long-term cooling coincident with a decrease of atmospheric CO2 levels, yet the cause of climate cooling at that time still remains debated. In this study, we evaluated the possible implication of enhanced silicate weathering as a sink for atmospheric CO2 by applying paired NdHf isotope measurements to detrital clay records from the West African margin. The use of this novel proxy for chemical weathering intensity (ΔɛHf(t)clay) was complemented by additional mineralogical and major-trace element analyses in order to investigate the variability of mechanical erosion patterns and further explore potential linkages between tectonics, weathering and climate during the late Cretaceous.Our ΔɛHf(t)clay data suggest more intense silicate weathering on the West African Craton during the Santonian to the middle Campanian period, coincident with enhanced physical erosional inputs as inferred from higher Quartz/Clays and Feldspar/Clays ratios. This observation suggests that the shift towards intensified chemical weathering at that time was driven by enhanced mechanical erosion, possibly related to a moderate tectonic event on the West African craton. Evidence for increasing kaolinite contents and higher ΔɛHf(t)clay values during the Maastrichtian point towards more hydrolysing conditions, inducing either destabilization of older Mesozoic lateritic material or favouring the development of kaolinite-rich soils.Overall, this study was compared with several new data of chemical weathering evolution along the south Atlantic margins, adding new insights on tectonic-weathering-climate interactions during the late Cretaceous, suggesting a possible link between silicate weathering feedbacks and global cooling at that time.

Remote sensing monitoring of irrigated area in the non-growth season and of water consumption analysis in a large-scale irrigation district

Globally, water scarcity threatens food security, especially in arid and semi-arid food-producing regions, such as the Hetao Irrigation District (HID), where the water consumption during the non-growth season (spring irrigation, autumn irrigation) accounts for more than 30 % of the total irrigation volume. Meanwhile, mapping the characteristics of spatial and temporal evolution of the area of cropland irrigated in the spring and autumn and the pattern of water consumption is crucial for strengthening the management of agricultural water use. Evaporation and infiltration of irrigation water are difficult to capture in time due to insufficient timeliness or accuracy of single remote sensing data. This study integrates seven remote sensing datasets (Landsat5, Landsat7, Landsat8, HJ-1A/B, GF-1, Sentinel-2 and MODIS) for the first time to build a high spatial-temporal resolution dataset, and combines the water index NDWI and MNDWI to extract the maximum water range formed after irrigation by manually adjusting the threshold method. In addition to the global land use/cover dataset (GLC FCS30–1985_2020), the cropland layer was superimposed to accurately identify the cropland spring irrigation and autumn irrigation range from 2000 to 2021 in the HID. In the past 20 years, spring-irrigated (SI) areas increased by 1012.60 km2 (+49.96 %), and the autumn-irrigated (AI) areas decreased by 512.63 km2 (-11.02 %). Combined with the quantity of water diversion and displacement, the characteristics of irrigation water consumption in the non-growth season were further analysed. The results showed that the water consumption of spring irrigation increased by 0.67×108 m3 (+22.26 %), and that of autumn irrigation increased by 4.34×108 m3 (+38.82 %). The decrease of autumn- irrigated area and the increase of water consumption were mainly related to the stability of autumn irrigation water, imperfect irrigation and drainage conditions and insufficient field water management. In 2020­2021, the area of non-growth “autumn irrigation - spring irrigation” repeated irrigation is about 1271.52 km2, which can be used as a key control area. This study provides a theoretical basis and direction for rational water use in non-growth seasons of irrigation districts.

Real-time capture of nuclear motions influencing photoinduced electron transfer.

Although vibronic coupling phenomena have been recognized in the excite state dynamics of transition metal complexes, its impact on photoinduced electron transfer (PET) remains largely unexplored. This study investigates coherent wavepacket (CWP) dynamics during PET processes in a covalently linked electron donor-acceptor complex featuring a cyclometalated Pt(ii) dimer as the donor and naphthalene diimide (NDI) as the acceptors. Upon photoexciting the Pt(ii) dimer electron donor, ultrafast broadband transient absorption spectroscopy revealed direct modulation of NDI radical anion formation through certain CWP motions and correlated temporal evolutions of the amplitudes for these CWPs with the NDI radical anion formation. These results provide clear evidence that the CWP motions are the vibronic coherences coupled to the PET reaction coordinates. Normal mode analysis identified that the CWP motions originate from vibrational modes associated with the dihedral angles and bond lengths between the planes of the cyclometalating ligand and the NDI, the key modes altering their π-interaction, consequently influencing PET dynamics. The findings highlight the pivotal role of vibrations in shaping the favorable trajectories for the efficient PET processes.

Co-seismic and post-seismic slip associated with the 2021 Mw5.9 Arkalochori, Central Crete (Greece) earthquake constrained by geodetic data and aftershocks

The co-seismic and post-seismic deformation field associated with the Mw5.9 Arkalochori main shock that occurred in central Crete (Greece) on 27 September 2021 is analyzed using Copernicus Sentinel-1A & 1B images, GNSS measurements and seismological data. The fault geometry is constrained through the joint inversion of multiple datasets and the slip distribution for the co-seismic and post-seismic period is obtained using a homogeneous half-space elastic model and the Steepest Descent Method. The results indicate a blind normal fault striking 215° with a 55° dip to the northwest and the co-seismic slip model suggests a nearly circular main slip patch (8 × 6 km2) with a maximum slip of 0.98 m. Post-seismic displacements started rapidly after the main shock followed by a gradual decay as highlighted by the calculated InSAR time series. The temporal evolution of post-seismic slip is described by a simple logarithmic function, decaying faster at the southwest part of the fault. The cumulative afterslip model suggests that the maximum post-seismic slip of 0.23 m occurred within a similar depth range compared to the co-seismic one, yet with a shift towards the southwest. Post-seismic slip inside the main shock rupture area is sustained, highlighting the slow recovery of locking in the co-seismic slip region. Afterslip (seismic or aseismic) played a dominant role in the early post-seismic period acting complementarily to the main rupture. Indications suggest that the spatiotemporal evolution of the productive aftershock sequence may be driven afterslip, alongside other potential factors.

Spatial effect of urban morphology on land surface tempature from the perspective of local climate zone

Urban expansion results in the intrusion of artificial surfaces into natural environments, giving rise to phenomena such as urban heat islands and heightened temperatures within inhabited areas. This study examined the dynamic evolution of urban morphology and land surface temperature through the lens of local climate zone. Furthermore, the spatial relationship between urban morphology indices and land surface temperature was analyzed within the context of loops. The investigation yielded several noteworthy findings: (1) LCZ8, LCZ6, and LCZD were the most significant transfer-in and transfer-out classes within the study area. (2) The heat contribution of residential LCZs (LCZ 2,3,5) decreased over time, ranging from 0.415 to 0.171, while that of industrial LCZs (LCZ 8,10) increased within the range of 0.348–0.553. (3) Urban heat island mitigation can be achieved by regulating building height and surface fraction. Establishing a judicious threshold for reducing LST is imperative for sky view factor and impervious surface fraction factors. Surface albedo exhibited a substantial inhibitory effect in 2020. The observation of urban morphological changes and long-term local climate zone considerations integrate the responsibility of mitigating urban heat islands into urban planning.

Investigation of anchor ice evolution in rivers and the impact of hydrometeorological conditions

The evolution of anchor ice during river freeze-up is known to significantly influence sediment transport, fish habitats, and river hydrology during winter. It may also lead to the formation of anchor ice dams and the generation of anchor ice waves that can cause flooding. Many of the previous field studies of anchor ice focused on the conditions leading to its formation and release, its crystal structure and properties, and the evaluation of its impacts. However, direct measurements of the temporal variation of anchor ice in rivers are rare, which has limited our understanding of this important and dynamic ice form. In this study, six anchor ice events were measured on two Canadian rivers using an underwater camera system, accompanied by comprehensive measurements of weather and hydraulic data and frazil ice concentrations. The temporal evolution of anchor ice was observed to occur in one of three stages: growth, stable, or decay. The direction (i.e., upward or downward) and trend of the net air–water heat flux reliably indicated the timing of these three stages. Anchor ice growth in the majority of events was through a combination of frazil accretion and in-situ crystal growth, resulting in event-averaged growth rates from 0.48 to 1.77 cm/h. Anchor ice grew solely through frazil accretion when snowfall occurred, with event-averaged growth rates from 1.64 to 3.53 cm/h. Anchor ice decay occurred through the thermal thinning of accumulations at an average decay rate of −0.48 to −2.52 cm/h. Anchor ice release was controlled by thermal factors and always occurred after the end of supercooling. Frazil accretion rates were estimated using measurements of anchor ice growth rates and suspended frazil concentrations and ranged from 2.6 × 10−3 to 6.0 × 10−3 m/s.

Rethinking real-time risk prediction from multi-step time series forecasting on highway car-following scenarios

Driving risk prediction emerges as a pivotal technology within the driving safety domain, facilitating the formulation of targeted driving intervention strategies to enhance driving safety. The driving safety undergoes continuous evolution in response to the complexities of the traffic environment, representing a dynamic and ongoing serialization process. The evolutionary trend of this sequence offers valuable information pertinent to driving safety research. However, existing research on driving risk prediction has primarily concentrated on forecasting a single index, such as the driving safety level or the extreme value within a specified future timeframe. This approach often neglects the intrinsic properties that characterize the temporal evolution of driving safety. Leveraging the high-D natural driving dataset, this study employs the multi-step time series forecasting methodology to predict the risk evolution sequence throughout the car-following process, elucidates the benefits of the multi-step time series forecasting approach, and contrasts the predictive efficacy on driving safety levels across various temporal windows. The empirical findings demonstrate that the time series prediction model proficiently captures essential dynamics such as risk evolution trends, amplitudes, and turning points. Consequently, it provides predictions that are significantly more robust and comprehensive than those obtained from a single risk index. The TsLeNet proposed in this study integrates a 2D convolutional network architecture with a dual attention mechanism, adeptly capturing and synthesizing multiple features across time steps. This integration significantly enhances the prediction precision at each temporal interval. Comparative analyses with other mainstream models reveal that TsLeNet achieves the best performance in terms of prediction accuracy and efficiency. Concurrently, this research undertakes a comprehensive analysis of the temporal distribution of errors, the impact pattern of features on risk sequence, and the applicability of interaction features among surrounding vehicles. The adoption of multi-step time series forecasting approach not only offers a novel perspective for analyzing and exploring driving safety, but also furnishes the design and development of targeted driving intervention systems.

Electron-ion relaxation times in 1–100 eV warm dense aluminum and gold

We calculated the electron-ion energy relaxation times in warm dense aluminum and gold. Our calculations span a wide temperature range from a thousand to a million kelvins for both dense aluminum and gold. To determine the temporal evolution of electron and ion temperatures, we employed the two-temperature model with the SESAME equation-of-state tables, and well-known electron-ion coupling factors. Our calculations indicate that the relaxation times for warm dense aluminum were within 5 ps, whereas they were within 20 ps for warm dense gold. The maximum relaxation times were observed at initial electron temperatures of approximately 30,000 K for both aluminum and gold. Our calculated relaxation times using the SESAME database agree very well with the existing theories both in the cold-solid and hot-plasma limits. Furthermore, we found that the melting times calculated using the Lindemann criterion were in good agreement with the melting times for gold from measurements in recent literature.

Mathematical study of a new coupled electro-thermo radiofrequency model of cardiac tissue

This paper presents a nonlinear reaction–diffusion-fluid system that simulates radiofrequency ablation within cardiac tissue. The model conveys the dynamic evolution of temperature and electric potential in both the fluid and solid regions, along with the evolution of velocity within the solid region. By formulating the system that describes the phenomena across the entire domain, encompassing both solid and fluid phases, we proceed to an analysis of well-posedness, considering a broad class of right-hand side terms. The system involves parameters such as heat conductivity, kinematic viscosity, and electrical conductivity, all of which exhibit nonlinearity contingent upon the temperature variable. The mathematical analysis extends to establishing the existence of a global solution, employing the Faedo–Galerkin method in a three-dimensional space. To enhance the practical applicability of our theoretical results, we complement our study with a series of numerical experiments. We implement the discrete system using the finite element method for spatial discretization and an Euler scheme for temporal discretization. Nonlinear parameters are linearized through decoupling systems, as introduced in our continuous analysis. These experiments are conducted to demonstrate and validate the theoretical findings we have established.

Optimal groundwater depth and irrigation amount can mitigate secondary salinization in water-saving irrigated areas in arid regions

Secondary salinization poses a significant threat to the sustainable development of water-saving irrigation districts. This study aims to explore the spatial and temporal variations in soil salinity and the factors influencing these changes in water-saving irrigation areas in the inland arid regions of Northwest China. The Manas River Irrigation District was selected as the study area. A grid measuring 10 km × 14 km grid was designed to determine the latitude and longitude coordinates of the grid centers, resulting in 66 sample points. Soil samples were collected from these points in 2013, 2014, 2020, and 2021 from the 0100 cm layer to obtain salinity data. Based on existing research and practical conditions in water-saving irrigation areas, 11 factors influencing soil salinity changes were identified, including irrigation area and irrigation amount. Classical statistical methods and interpretable machine learning techniques were employed to analyze the distribution characteristics of soil salinity and the influencing factors. This analysis proposes effective solutions to mitigate potential secondary salinization in irrigation areas. The results revealed that soil salinity in the irrigation area belonged to moderate variation (Cv = 46.74 %51.80 %). The horizontal direction of the irrigation area shows higher salt content in the upstream and downstream areas, and a gradual decrease in variability with increasing depth characterizes the vertical direction. From 2013–2021, soil salinization in the irrigation area gradually decreased. In 2013 and 2014, the area was predominantly covered by mild saline-alkali soil, accounting for 75.1 % and 76.6 % of the total area, respectively. However, in 2020 and 2021, non-saline soils became dominant, covering 60.9 % and 66.5 % of the total irrigation area, respectively. In order of importance, the factors affecting the spatial and temporal evolution of soil salinity are groundwater depth, annual water surface evaporation, water-saving irrigation area, underground water diversion amount, mineralization of groundwater, irrigation amount, surface water diversion amount, and annual rainfall. In the oasis irrigation area, maintaining a groundwater depth of 4.06.0 m and an irrigation amount of 55006000 m3 ha−1 can alleviate the problem of secondary salinization that may result from large-scale development of water-saving irrigation. The findings of this study provide a basis for the prevention and control of soil salinization in water-saving irrigation areas and the development and management of saline land in oasis areas.

CONTRIBUTION OF SEISMIC AND GEOTHERMAL DATA ANALYSIS TO THE ASSESSMENT OF THE HYDROCARBON POTENTIAL OF THE CENTRAL BASIN OF THE D.R. CONGO

This paper presents an evaluation of the hydrocarbon potential of the Cuvette Centrale basin in the Democratic Republic of Congo (DRC) using an integrated approach that combines seismic and geothermal data. The envelope attribute of seismic data was used to identify different rocks of the petroleum system, including potential gas-prone zones. The interpretation of seismic profiles helped to delineate geological units and determine their lithology. Isobath maps based on seismic data revealed the presence of grabens and anticlines, which are favorable geological structures for hydrocarbon accumulation. Analysis of the geothermal gradient and temperature evolution in the formations allowed us to establish source rock maturity maps, highlighting two distinct zones: an overmature zone favorable for gas and a mature zone favorable for oil. These results suggest a strong hydrocarbon potential in the Cuvette Centrale basin.

Heat transfer deformation test and model of coal during LN2 cyclic freezing and thawing process

Exploring the temperature response and deformation characteristics of coal during the freeze–thaw process is crucial for maintaining coal seam stability under liquid nitrogen (LN2) treatment and enhancing gas extraction efficiency. This study investigates the temperature diffusion and deformation characteristics of coal during LN2 cyclic freeze–thaw processes, using saturated and dry anthracite samples. Real-time monitoring of the freeze–thaw characteristics of the anthracite samples was conducted using temperature and strain detectors to quantitatively analyze the evolution of coal temperature and strain. Additionally, a nuclear magnetic resonance (NMR) testing system was used to monitor the pore evolution characteristics of the coal before and after LN2 treatment. The results indicate: After LN2 cyclic freeze–thaw, the internal pores of the saturated samples were highly developed, and fracture connectivity was enhanced, whereas the pores in the dry samples significantly decreased, leading to a sharp reduction in overall connectivity. The cooling and heating rates of the saturated samples were higher than those of the dry samples, both exhibiting exponential trends. This variation is primarily due to the phase change of pore water and the formation and expansion of the internal fracture network within the coal. The deformation magnitude of both sample types showed an overall exponential decline, with the saturated samples exhibiting higher deformation magnitudes than the dry samples. The presence of fracture water not only accelerates coal deterioration during the freeze–thaw process but also enhances coal cementation, maintaining deformation stability. Furthermore, this paper derives a temperature-strain coupling model for coal subjected to LN2 F-T cycles, aiming to provide a reference for understanding the freeze–thaw damage mechanism of coal and the practical application of LN2 fracturing.

Using Dynamic Laser Speckle Imaging for Plant Breeding: A Case Study of Water Stress in Sunflowers.

This study focuses on the promising use of biospeckle technology to detect water stress in plants, a complex physiological mechanism. This involves monitoring the temporal activity of biospeckle pattern to study the occurrence of stress within the leaf. The effects of water stress in plants can involve physical and biochemical changes. Some of these changes may alter the optical scattering properties of leaves. The present study therefore proposes to test the potential of a biospeckle measurement to observe the temporal evolution in different varieties of sunflower plants under water stress. An experiment applying controlled water stress with osmotic shock using polyethylene glycol 6000 (PEG) was conducted on two sunflower varieties: one sensitive, and the other more tolerant to water stress. Temporal monitoring of biospeckle activity in these plants was performed using the average value of difference (AVD) indicator. Results indicate that AVD highlights the difference in biospeckle activity between day and night, with lower activity at night for both varieties. The addition of PEG entailed a gradual decrease in values throughout the experiment, particularly for the sensitive variety. The results obtained are consistent with the behaviour of the varieties submitted to water stress. Indeed, a few days after the introduction of PEG, a stronger decrease in AVD indicator values was observed for the sensitive variety than for the resistant variety. This study highlights the dynamics of biospeckle activity for different sunflower varieties undergoing water stress and can be considered as a promising phenotyping tool.

Systematic study of polymer gas sampling bags for offline analysis of exhaled breath

Polymeric bags are a widely applied, simple, and cost-effective method for the storage and offline analysis of gaseous samples. Various materials have been used as sampling bags, all known to contain impurities and differing in their cost, durability, and storage capabilities. Herein, we present a comparative study of several well-known bag materials, Tedlar (PVF), Kynar (PVDF), Teflon (PTFE), and Nalophan (PET), as well as a new material, ethylene vinyl copolymer (EVOH), commonly used for storing food. We investigated the influences of storage conditions, humidity, bag cleaning, and light exposure on volatile organic compound concentration (acetone, acetic acid, isoprene, benzene, limonene, among others) in samples of exhaled human breath stored in bags for up to 48 h. Specifically, we show high losses of short-chain fatty acids (SCFAs) in bags of all materials (for most SCFAs, less than 50% after 8 h of storage). We found that samples in Tedlar, Nalophan, and EVOH bags undergo changes in composition when exposed to UV radiation over a period of 48 h. We report high initial impurity levels in all the bags and their doubling after a period of 48 h. We compare secondary electrospray ionization and proton transfer reaction mass spectrometry in the context of offline analysis after storage in sampling bags. We provide an analytical perspective on the temporal evolution of bag contents by presenting the intensity changes of all significantm/zfeatures. We also present a simple, automated, and cost-effective offline sample introduction system, which enables controlled delivery of collected gaseous samples from polymeric bags into the mass spectrometer. Overall, our findings suggest that sampling bags exhibit high levels of impurities, are sensitive to several environmental factors (e.g. light exposure), and provide low recoveries for some classes of compounds, e.g. SCFAs.

Identification of an optimal ground-based validation site for FLEX and quantification of uncertainties using airborne HyPlant data - A case study in Italy

The Fluorescence Explorer (FLEX) satellite will carry the high-resolution Fluorescence Imaging Spectrometer (FLORIS) that measures the complete fluorescence spectrum emitted by chlorophyll of terrestrial vegetation. This small signal must be validated. One validation approach is comparing the fluorescence signal retrieved from satellite-based measurements with ground based measurements. However, the difference in spatial resolution of the satellite and ground-based instruments and a geolocation mismatch will result in differences in the detected signal and thus, in uncertainties of the validation strategy. In a case study, we identify a representative ground site for validating the fluorescence signal by analyzing surface reflectance measurements from an aeroplane.We define requirements of representativeness for a validation ground site in vegetated areas. Based on those requirements, we identify a suitable position within a case study in central Italy using surface reflectance data from the airborne High-Performance Airborne Imaging Spectrometer (HyPlant) measured in summer 2018. The representativeness is quantified by the relative difference between the single HyPlant pixel representing a ground-based measurement and the averaged signal of several HyPlant pixels that mimics a FLORIS pixel. With this measure, we quantify the validation uncertainty due to spatial resolution and geolocation mismatch. The effect of the temporal evolution of the surface properties on the validation uncertainty due to spatial resolution is investigated.We select the ground site position by minimizing the validation uncertainty due to spatial resolution. Especially for wavelengths larger than 700 nm, this uncertainty is smaller than 2 % for all different reference areas. The largest differences between ground-based like measurement and satellite-like measurement of the surface reflectance is due to geolocation mismatch. The uncertainty due the geolocation mismatch is very large for wavelengths smaller than 720 nm and moderate for wavelengths larger than 720 nm. Thus, the surface reflectance at the chosen position for the validation site is not homogeneous enough for validation purpose. Considering a reference area of 13.5 × 13.5 m2, we quantify temporal stable and small uncertainties for the spectral range between 720 and 800 nm. For an all-embracing validation of the surface reflectance of vegetated areas, the chosen site is not appropriate.

Strain rate-dependency of thermal infrared radiation of sandstone subjected to dynamic loading: Insights from a lab testing

Rocks are generally deformed and fractured upon various scales of strain rates. Understanding the strain rate effects on the thermal infrared radiation (IR) characteristics of rock materials is crucial for predicting and detecting rock failure. In the study, uniaxial compression experiments were conducted on sandstone samples at different strain rates using an Instron hydraulic servo testing machine and a split Hopkinson pressure bar (SHPB) system. Meanwhile, a thermal infrared camera was utilized to capture and record the changes in the IR temperature on the rock surface. The spatial and temporal evolution of thermograms, IR temperature distribution histograms, and average IR temperature (AIRT) during testing were obtained and analyzed. A quantitative correlation between strain rate and the variation in AIRT (ΔT) was established. Furthermore, the dissipation of heat energy (Q) in the sandstone samples during SHPB tests was estimated. Results indicated that at relatively lower strain rates (ranging from 10−6 to 10−2 s−1), the ΔT of rock sample exhibited slight dependence on strain rate. However, a significant rate sensitivity emerged when the strain rate exceeded a specific threshold (approximately 137.09 s−1 for the tested sandstone). The rate-dependent behavior of ΔT across the investigated range of strain rate (up to 102) can be characterized by an allometric power model. Notably, during SHPB testing, the proportion of Q was negligible despite the pronounced rate dependency of heat energy. The abrupt rises in ΔT and Q under dynamic loading conditions can be elucidated by the increasing occurrence of shear cracks and energy-level jumps stimulated by impact disturbance.

A complex magnetic study: evidence of spin-glass transition below long-range magnetic ordering and its correlation with renormalization of phonon modes

In this paper, we report a complex magnetic behavior arising due to the interplay of three active magnetic cations (Nd/Sm, Co and Ir), forming 3d-5d-4f magnetic sublattices. The B-site ordered double perovskites Nd2CoIrO6and Sm2CoIrO6were successfully prepared by conventional solid-state method. Detailed structural analysis revealed that both samples crystallized in monoclinic structure with P21/n (No.-14) space group. X-ray photoelectron spectroscopy analysis confirms the presence of multiple oxidation states of Ir (i.e. Ir4+and Ir5+). Both samples show a paramagnetic-ferrimagnetic (TFiM) transition around 100 K, additionally, a low temperature transition is observed at around 10 K in the SCIO sample. This FM-like behavior of the samples is attributed to the antiparallel alignment of the Co2+and Ir4+spins, resulting in FiM ordering. The ac susceptibility analysis confirms a spin glass type transition just below the long-range ordering temperature in NCIO sample, The obtained characteristic flipping time of a single spin from both the law (Power law and Vogel-Fulcher law) and nonzero Vogel-Fulcher temperature (T0≃ 89.1 K) further verified the existence of cluster spin-glass behavior below the ordering temperature. The temperature evolution of phonon modes (up to 4 K) suggests that the phonon mode above the magnetic ordering temperature is mainly governed by the lattice degrees of freedom; notable renormalization of the mode frequency below the ordering temperature is due to the coupling of lattice with the underlying magnetic degrees of freedom.

Temperature evolution of laser-ignited micrometric iron particles: A comprehensive experimental data set and numerical assessment of laser heating impact

This study examines the effects of laser heating on the ignition and critical combustion characteristics, such as temperature and burn time, of individual iron particles. It provides time-dependent temperature profiles of laser-ignited particles across a broad spectrum of particle size distributions and oxygen concentrations obtained from experiments, which are a useful database for further development and validation of iron particle combustion models. The herein reported datasets significantly complement those existing in the literature. In the current study, the raw data are thoroughly re-evaluated using refined approaches. For the experimental canonical configuration of single iron particle combustion, an ignition system based on laser heating provides several advantages in overcoming temperature field uncertainties and facilitating controlled environments for optical diagnostics. Despite the inherent uncertainties in laser heating, associated with non-uniform intensity profiles and particle size variations, this study addresses the critical question of how these uncertainties affect in situ measurements of particle temperature and time to reach peak temperature. This study, conducted using a numerical model, reveals a dependence of the particle temperature after laser heating on particle size. However, this dependence does not significantly impact the key parameters of iron-particle combustion, such as the maximum temperature and burn time of the laser-ignited iron particle. The study also presents a comparison between the simulated particle temperature histories and those derived from two-color pyrometry measurements for a wide range of particle size distributions and oxygen concentrations. Notably, by implementing a laser-heating sub-model into an iron particle combustion model, assuming external-diffusion-limited oxidation only up to stoichiometric FeO, the temperature evolution up to the maximum temperature is reasonably captured for a wide range of particle sizes (20–53μm) and oxygen volumetric fractions (14–21vol% O2 mixed with N2). However, with increasing oxygen concentration, the external-diffusion limited model significantly overestimates the heating rate and subsequently the maximum particle temperature.

Progress on Numerical Simulation of Gas-Liquid Two-Phase Flow in Self-Priming Pump

The fundamentals of the design and operation of self-priming pumps, as indispensable equipment in industry, have been the focus of research in the field of fluid mechanics. This paper begins with a comprehensive background on self-priming pumps and gas-liquid two-phase flow, and it outlines recent advances in the field. Self-priming pumps within the gas-liquid two-phase flow state and the spatial and temporal evolution of the transient characteristics of self-priming pumps determine the self-priming pump self-absorption performance. Through mastery of the self-absorption mechanism, high-performance self-absorption pump products can be formed to provide theoretical support for the development of products. In current research, numerical simulation has become an important tool for analyzing and predicting the behavior of gas-liquid two-phase flow in self-priming pumps. This paper reviews existing numerical models of gas-liquid two-phase flow and categorizes them. Reviewing these models not only provides us with a comprehensive understanding of the existing research but also offers possible directions for future research. The complexity of gas–liquid interactions and their impact on pump performance is analyzed. Through these detailed discussions, we are able to identify the challenges in the simulation process and summarize what has been achieved. In order to further improve the accuracy and reliability of simulations, this paper introduces the latest simulation techniques and research methodologies, which provide new perspectives for a deeper understanding of gas-liquid two-phase flow. In addition, this paper investigates a variety of factors which affect the operating efficiency of self-priming pumps, including the design parameters, fluid properties, and operating conditions. Comprehensive consideration of these factors is crucial for optimizing pump performance. Finally, this paper summarizes the current research results and identifies the main findings and deficiencies. Based on this, the need to improve the accuracy of numerical simulations and to study the design parameters in depth to improve pump performance is emphasized.