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Both straight and curved carbon fibers are widely used in various commercial gas diffusion layer (GDL) fabrications. The effect of the different carbon fiber curvatures on two-phase flow dynamics within the cathode GDLs of proton exchange membrane fuel cells remains unclear. In this study, we investigate liquid transport in three types of GDLs with varying fiber curvatures using the two-phase volume of fluid simulations in OpenFOAM. For the first time, a rod periodic surface model is combined with a layer-by-layer fiber stacking strategy, to stochastically reconstruct GDL structures while incorporating crucial parameters from physical (experimental) GDLs. A grid independence study and model validation are conducted. Following pore network analysis of pore size distribution and connectivity, we study the time-varying GDL total and local water saturation and capillary pressure. Despite maintaining similar layer and bulk porosity, increased fiber curvature enhances pore connectivity but raises water saturation and capillary pressure, increasing the risk of flooding. Additionally, droplets in gas channels with straight-fiber GDLs are larger and have slower movement than those in curved-fiber GDLs. Fiber curvature inversely affects drainage capacity in GDLs and connected channels. With comparable water saturation and capillary pressure, curved-fiber GDLs exhibit lower discrepancies, suggesting improved uniformity in water distribution. [Display omitted] • Curved and straight fiber GDLs are reconstructed with similar bulk and layer porosity. • Increasing fiber curvature enhances pore connectivity and pore quantity. • GDL water saturation and capillary pressure increase with an increased fiber curvature. • Increasing the amount of small pores results in stronger water spreading within GDLs. • Detached droplets in GCs have smaller sizes and longer liquid bridge when using curved-fiber GDLs. [ABSTRACT FROM AUTHOR]

• Bubble cluster behaviour in froth characterised by dynamic X-ray radiographic setup. • Particle reattachment, dropback, and accumulation were visualised. • X-ray radiography is a valuable tool for investigating froth dynamics. X-ray radiography presents a non-invasive and dynamic approach for examining multiphase flows, particularly in complex systems like flotation froths. While this technique has been applied successfully in various multiphase studies, such as granular flows and fluidised beds, its utilisation in understanding flotation froths is novel. This study aimed to investigate the behaviour of particles and bubbles within the froth phase using a unique flotation rig combined with an X-ray radiographic setup. Specifically, it sought to understand how the pulp-froth interface influences the entry of bubble clusters into the froth phase and to observe the journey of particles within the froth. The results provided tangible evidence supporting previously inferred phenomena. It was found that the interface between the pulp and froth acted as a barrier, impeding the entry of bubble clusters into the froth phase. However, what was particularly noteworthy about the study was its revelation of extraordinary dynamics in particle movement within the froth phase. These dynamics included the occurrence of reattachment and dropback at critical solid fractions, phenomena that were visually observed for the first time. [ABSTRACT FROM AUTHOR]

• the percentage of release signals typically ranged between 5 and 30% per decade; • release frequency per decade was over-dispersed compared to the random (Poisson) model; • cadences of increasing/decreasing tree growth lasted between 24 and 54 years (30 years on average); • stand-level fluctuations in tree growth were small compared to the total variation in tree increment; • a mixed-severity disturbance regime suggests unsteady gap-phase dynamics. Disturbances have been recognized as a key factor shaping the species composition, structure and dynamics of natural forest ecosystems. In Europe, where forests driven by spontaneous processes have survived in relic form, knowledge about natural disturbance regimes is still fragmentary. To expand this knowledge, we reconstructed stand-level growth and analyzed the spatio-temporal pattern of release signals in the increment chronologies of individual trees as indicators of disturbance events in the Western Carpathians (Central Europe). The study was carried out in five old-growth forests formed by Fagus sylvatica L., Abies alba Mill. and Picea abies (L.) H. Karst. Depending on the stand, the analyses included tree-ring series of 84–193 trees sampled over areas of 5.9–13.6 ha and aimed at determining (1) the spatio-temporal pattern of disturbance severity over the last two centuries, (2) whether disturbances have been synchronized in time across the study sites and (3) whether disturbances have induced pulsed dynamics of stand development manifested as fluctuations in radial tree increment at the level of entire stands. In the period 1850–2010, the percentage of decades with the proportion of released trees < 10, 10–20, 20–30 or more than 30% was 38, 41, 14 and 7%, respectively, and no instances of severe disturbances simultaneously impacting an extensive area and releasing the vast majority of trees were found. The release events were only weakly synchronized at the between-stand level. The spatial distribution of released trees varied over the decades, with a shift toward spatial independence for the most severe disturbances. At the stand level, the interchanging periods of increasing/decreasing tree growth lasted between 24 and 36 years, with the exception of one stand in which this period lasted 54 years. The revealed fluctuations in tree growth attributable to changes in stand density were relatively small and accounted on average for 7% of the total variation in annual tree increments. This suggests that local level disturbances introduce structural heterogeneity and strongly modify tree growth, but at the stand level, their effect is dispersed and causes only minor fluctuations. An over-dispersion of decadal release frequencies compared to the random model and spatial correlation of disturbing events on the one hand, and the lack of extensive disturbances, frequent occurrence of multiple releases in tree life histories, and small fluctuations in the reconstructed growth at the stand level on the other hand, suggest a disturbance regime which goes beyond random processes in a strict sense and is thus not entirely compatible with the classical model of gap-phase stand dynamics. [ABSTRACT FROM AUTHOR]

The CALPHAD system of fundamental phase-level databases, now known as the Materials Genome, has enabled a mature technology of computational materials design and qualification that has already met the acceleration goals of the national Materials Genome Initiative. As first commercialized by QuesTek Innovations, the methodology combines efficient genomic-level parametric design of new material composition and process specifications with multidisciplinary simulation-based forecasting of manufacturing variation, integrating efficient uncertainty management. Recent projects demonstrated under the multi-institutional CHiMaD Design Center notably include novel alloys designed specifically for additive manufacturing. With the proven success of the CALPHAD-based Materials Genome technology, current university research emphasizes new methodologies for affordable accelerated expansion of more accurate CALPHAD databases. Rapid adoption of these new capabilities by US apex corporations has compressed the materials design and development cycle to under 2 years, enabling a new "materials concurrency" integrated into a new level of concurrent engineering supporting an unprecedented level of manufacturing innovation. [ABSTRACT FROM AUTHOR]

A novel structural dynamic model for free standing hybrid riser (FSHR) is established based on the absolute nodal coordinate formulation (ANCF) in the present study. The position and slope coordinates are used in global framework to avoid coordinate transformation, and an accurate geometric relationship is introduced to describe geometric nonlinearity. The current loads on the risers and buoyancy can are simulated by Morrison equation and wake oscillator, respectively. After case validations, the vortex-induced motion (VIM) regimes of the buoyancy can and the phase dynamics of the riser and jumper in a FSHR system, subjected to the ocean current and vessel motion, is numerically investigated. It is found that the VIM of the buoyancy can experiences multiple motion switches among the periodic, quasiperiodic, multiple periodic, transition I and transition II regimes under different vessel motions. The y -motion of the jumper and both x - and y -motions of the riser present the phase trapping phenomenon along the structures. The phase trapping and locking, phase drifting and slipping, and other states are observed for x -motion of the jumper, which form a shape of "fish head" with opening mouth towards lower amplitude or higher period of vessel motion in regime map. • A novel structural dynamic model for FSHR system is established based on the ANCF. • Periodic, quasiperiodic, multiple periodic, transition I and II regimes of VIM are found under different vessel motions. • Three transition and multiple periodic bands are interspersed in the quasiperiodic regime of VIM. • The phase trapping and locking, drifting and slipping, and other states are captured for in-line motion along the jumper. • The phase dynamics of the jumper form a shape of "fish head" in the regime map. [ABSTRACT FROM AUTHOR]

Mixer-setters units are widely used in uranium purification processes. For efficient operations of mixer-settler units, it is essential to measure the hydrodynamics parameters of the different phases involved. The residence time distribution (RTD) measurement is commonly used method to estimate the hydrodynamics parameters of process reactors. In the present study, RTD of the aqueous phase was measured in different stages mixer-settler unit (mixers, settlers and mixer-settler units) used for stripping operation using Iodine-131 as a radiotracer. For the RTD measurements, radiotracer was injected as an impulse in aqueous phase feed line and its movement was monitored at different locations in the stripping unit using NaI(Tl) detectors. The mean residence times (MRTs) of the aqueous phase were estimated from measured RTD curves. For quantification of the degree of mixing, suitable flow models were proposed based on design and nature of the measured RTD curves and subsequently used for simulation. Based on the results of the RTD study, the mixing of aqueous phase was characterized and design of the stripping unit and its sub-units were validated. The optimum conditions were identified for efficient for the operation of the stripping unit. • The aqueous phase RTD in stripper unit and its sub-units was measured. • The MRT of the aqueous was estimated at different operating conditions. • Different flow models were used to quantify degree of mixing of aqueous phase. • The operating conditions of the stripping unit were optimized. [ABSTRACT FROM AUTHOR]

In DC microgrids, the cascade operation of the DC-DC converters leads to a constant power load fed by the boost converter, resulting in unstable behavior in addition to the non-minimum phase dynamics. An enhanced load disturbance rejection control scheme based on partial pole placement and an approximate model matching technique is proposed. This approach is inspired by the well-known direct synthesis method to achieve optimal load disturbance rejection performance. The effectiveness of the proposed control scheme has been validated through hardware implementation, demonstrating its capability in setpoint tracking and load disturbance rejection under variations in load power and input voltage. The robust stability of the suggested scheme has been investigated through the Kharitonov theorem and Monte-Carlo simulation, considering different performance matrices. The suitability of the presented scheme has been established by analyzing the comparative performance of recently reported works. The proposed controller reduces peak overshoot and settling time by ∼ 50 % , handles system uncertainties up to 75 % , and outperforms FOPID controllers tuned with particle swarm optimization, queen bee genetic algorithm, and chaos game optimization methods. [ABSTRACT FROM AUTHOR]

• Delta-alpha coupling functions from EEG (electroencephalogram) of whole night sleep. • Use of dynamical Bayesian inference for phase dynamics from brainwave oscillations. • δ - α coupling function increased gradually from Awake to NREM3(non-rapid eye movement). • δ - α coupling function is significant to surrogates only for NREM2 and NREM3. • Spatially – significance is strong within region and in front-to-back direction. The human brain presents a heavily connected complex system. From a relatively fixed anatomy, it can enable a vast repertoire of functions. One important brain function is the process of natural sleep, which alters consciousness and voluntary muscle activity. On neural level, these alterations are accompanied by changes of the brain connectivity. In order to reveal the changes of connectivity associated with sleep, we present a methodological framework for reconstruction and assessment of functional interaction mechanisms. By analyzing EEG (electroencephalogram) recordings from human whole night sleep, first, we applied a time–frequency wavelet transform to study the existence and strength of brainwave oscillations. Then we applied a dynamical Bayesian inference on the phase dynamics in the presence of noise. With this method we reconstructed the cross-frequency coupling functions, which revealed the mechanism of how the interactions occur and manifest. We focus our analysis on the delta-alpha coupling function and observe how this cross-frequency coupling changes during the different sleep stages. The results demonstrated that the delta-alpha coupling function was increasing gradually from Awake to NREM3 (non-rapid eye movement), but only during NREM2 and NREM3 deep sleep it was significant in respect of surrogate data testing. The analysis on the spatially distributed connections showed that this significance is strong only for within the single electrode region and in the front-to-back direction. The presented methodological framework is for the whole-night sleep recordings, but it also carries general implications for other global neural states. [ABSTRACT FROM AUTHOR]

The catastrophic effects of climate change can be mitigated by transitioning to renewable energy sources such as wind, solar, and hydropower while utilizing hydrogen (H 2) as an energy carrier. As renewable fuel sources are intermittent and location-specific, large-scale, long-term storage options for H 2 must be explored with high necessity. Subsurface hydrogen storage in saline aquifers provides a vital scope to store H 2 gas in available pore voids with minimal environmental risk. In this work, a highly heterogeneous porous micromodel was used to study the immiscible two-phase dynamics at high-temperature, high-pressure saline aquifer conditions using computational fluid dynamics (CFD) simulation based on volume of fluid (VOF) method. A set of microfluidic experiments were carried out under atmospheric conditions to validate the numerical model. The VOF model was observed to show good agreement with microfluidic experiments. An unstable displacement pattern with viscous fingering was observed during various flow conditions that captured high pressure (15 and 25 MPa) and temperature conditions (323 and 343 K). It was observed that fingering displacement of brine limits the storage spaces for hydrogen, which consequently follows the high permeable path. As a result, only 0.272 fraction of brine was invaded by the H 2 at a temperature of 323 K and pressure of 15 MPa. A comparison between H 2 -brine and nitrogen (N 2)-brine flow dynamics revealed a 46% less storage capacity of porous media for H 2. Formations bearing high temperature (343 K) showed an 11.27% increase in H 2 storage capacity, while pressure increase had negligible effect. At low capillary number (Ca), more snap-off effects resulted in higher trapping of H 2 gas. This study aims to provide meaningful insights into the complexities of flow dynamics and displacement patterns that are crucial for optimizing hydrogen storage efficiency in saline aquifers and for potential 'white' hydrogen production. [Display omitted] • Hydrogen-brine two-phase flow was simulated in a heterogeneous porous media. • Simulation captures pressure and temperature conditions of geological aquifers. • Microfluidic experiments were carried out to validate the numerical model. • Viscous fingering under high-pressure and temperature limits hydrogen storage. • More snap-off effects lead to increased hydrogen trapping in porous media. [ABSTRACT FROM AUTHOR]

[Display omitted] • Menthol and C8 – C10 fatty form a paradigmatic type V hydrophobic eutectic solvent (V-HDES). • Both H-bond and dispersive interactions contribute to the liquid structuration. • The formation of cyclic hetero-dimers via intermolecular and interspecies H-bonds is predicted by DFT and MD. • COSMO-RS predicts several thermodynamic properties of V-HDES. • In silico toxicological profile suggests V-HDES - human target proteins interactions. In this work, we present experimental and molecular modeling results on archetypal hydrophobic natural deep eutectic solvents (NADES) based on fatty acids (octanoic and dodecanoic acid) and menthol, a representative monoterpenoid. Our goal is to provide a multiscale characterization to enhance the understanding of this field by studying these selected archetypical mixtures. We examine their liquid state properties, intermolecular forces, nanoscopic arrangements, toxicity, and environmental impact. The computational study integrates quantum chemistry, molecular dynamics (both all-atom and coarse-grained approaches), and thermodynamic modeling (COSMO-RS approach) to analyze the fluids and their interactions with biological entities, such as proteins and plasma membranes. The experimental characterization focuses on elucidating intermolecular interactions and liquid phase dynamics using NMR spectroscopy, visible and UV Resonance Raman spectroscopy (UVRR). Notably, this is the first report of UVRR data on NADES. Additionally, we simulate the effect of the molecular moieties forming the solvents on biological targets—specifically, protein and cell membrane models –. This in silico analysis aims to rationalize and predict their potential toxicity. Overall, our experimental findings and in silico simulations contribute to a deeper understanding of these novel solvents in terms of their network of interactions. Additionally, they highlight the potential impact on biological targets, providing new data to accurately define the eco-friendliness of type V DES and their suitability as sustainable alternatives to traditional molecular solvents. [ABSTRACT FROM AUTHOR]

[Display omitted] • The non-isothermal crystallization behavior and kinetics of polytetrafluoroethylene (PTFE) composites with boron nitride nanobarb (BNNB), a new generation nanostructure with unique surface morphology and mechanical "barbs" have been analyzed, understanding these properties is essential for their high-end applications as thermal interface materials (TIM) for microwave, 5G and microelectronic devices. • The analysis of the crystallization parameters includes crystallization onset, peak and end temperatures, crystallization half-life and overall crystallinity of PTFE, modified PTFE and their BNNB composites. The results were further analyzed using theoretical models such as the combined Avrami-Ozawa model. It was found that BNNB supports crystallization in the modified PTFE but shows minimal effect on the crystallization of PTFE. • Due to the limitation of the classical theoretical models used above in fully characterizing the multi-step crystallization process of PTFE, an in-depth analysis using the model-free advanced isoconversional computation was used to characterize the PTFE crystallization based on the evolution of activation energy with fractional crystallinity and for the first time with temperature. Three kinetic regions were identified in the crystallization mechanism. • The study investigated the molecular organization and microstructural evolution of PTFE, modified PTFE and their composites during non-isothermal crystallization using advanced X-ray scattering measurements. An insight into the changes undergone by the material's microstructural units including crystallite size and morphology, lamellar thickness and lamellar interfacial layer thickness, and crystallographic phase dynamics during non-isothermal cooling from the melt, was provided in this work. • The effect of copolymer modification of PTFE and the inclusion of pristine and fucntionalized BNNB (a thermally conductive and electrically insulating ceramic) are both new investigations that provide valuable knowledge for the development of materials with strong matrix-nanofiller interaction and guidance for optimizing sintering and cooling cycles, two key steps in PTFE processing that largely affect the material microstructural features. Overall, the result of the three-part investigation demonstrates that BNNB supports crystallization in the modified PTFE up to 20 wt% concentration and at low and high cooling rates typically used in the industrial processing of PTFE. [ABSTRACT FROM AUTHOR]

Macroscopic oscillations in the brain are involved in various cognitive and physiological processes, yet their precise function is not completely understood. Communication through coherence (CTC) theory proposes that these rhythmic electrical patterns might serve to regulate the information flow between neural populations. Thus, to communicate effectively, neural populations must synchronize their oscillatory activity, ensuring that input volleys from the presynaptic population reach the postsynaptic one at its maximum phase of excitability. We consider an Excitatory–Inhibitory (E–I) network whose macroscopic activity is described by an exact mean-field model. The E–I network receives periodic inputs from either one or two external sources, for which effective communication will not be achieved in the absence of control. We explore strategies based on optimal control theory for phase–amplitude dynamics to design a periodic control that sets the target population in the optimal phase to synchronize its activity with a specific presynaptic input signal and establish communication. The control mechanism resembles the role of a higher cortical area in the context of selective attention. To design the control, we use the phase–amplitude reduction of a limit cycle and leverage recent developments in this field in order to find the most effective control strategy regarding a defined cost function. Furthermore, we present results that guarantee the local controllability of the system close to the limit cycle. • Optimal-control strategies provide controls that suitably adjust the dynamics for enhanced communication. • Controlled synchronization is decisive for effective communication in mean-field models of E–I networks. • Using phase–amplitude description, optimal periodic controls minimally alter the oscillation, while enhance communication. [ABSTRACT FROM AUTHOR]

Solitons, which can form soliton molecules analogous to the molecular structure of matter, are currently being investigated in multi-wavelength passively mode-locked fiber lasers. In this paper, four-soliton molecules are numerically obtained in a passively mode-locked fiber laser with all-normal dispersion. It is found that a number of structures of soliton molecular complexes can be created by adjusting polarization. It is possible to create four-soliton molecules of single-wavelength featuring vibrating and sliding phase dynamics. Furthermore, three different types of dual-wavelength four-soliton molecules can be achieved. Importantly, it is found that the wavelength spacing is not affected by the polarization shift, but only the existence of multiple wavelengths is determined. This work contributes to the generation of dual-wavelength pulses and the creation of soliton molecular complexes with diverse structural compositions. • A novel design based on a Yb-doped passively mode-locked fiber laser is proposed for wavelength-switchable soliton molecules. • The group velocity-locked vector soliton molecules of single-wavelength feature vibrating and sliding phase dynamics. • Three different types of dual-wavelength four-soliton molecules can be achieved, namely '1+3', '2+2', and '3+1'. • The variety of polarization direction θ causes a filtering effect, generating the dual-wavelength pulses. [ABSTRACT FROM AUTHOR]

• Three-dimensional symmetric phase-change lattice Boltzmann model is built up to investigate sessile droplet boiling on micro-pillar array surface in the nucleate boiling regime. • Effects of micro-pillar size on bubble evolution behaviors accompanied with droplet boiling morphologies, manifested in bubble nucleation, growth, coalescence and rupture are studied. • Quantitatively assessed include nucleation activation time, droplet total evaporation time, isolated bubble nuclei density, bubble size and substrate heat flux. • Temperature, confined space and fluid flow are discussed as key factors affecting the preferential activation location and the distribution of nucleation sites. • Understanding of droplet/bubble two-phase dynamics gives some insights to optimizing droplet nucleate boiling heat transfer performance by manipulating surface properties. Despite spray cooling in the form of droplet boiling on a textured surface being a very promising phase-change heat dissipating method, the understanding of droplet/bubble two-phase dynamics in the nucleate boiling is extraordinarily limited. In this study, we report sessile droplet boiling on micro-pillar array surface in the nucleate boiling regime using a three-dimensional lattice Boltzmann model comprehensively. Effects of micro-pillar size on bubble behaviors inside droplet are discussed in detail, covering bubble nucleation, growth, coalescence, and rupture. For the micro-pillars with large side length or small spacing, nucleation sites are activated around micro-pillar top surface. The preferential activation location of nucleation sites is determined by temperature, confined space and fluid flow. In bubble growth stage, the variation of bubble radius with time follows the square root law, being consistent with previous experiments. Bubbles merge into a large central bubble beneath droplet for the short micro-pillars while into a vapor layer for the long micro-pillars. Emergence of large central bubble prolongs droplet lifetime but deteriorates heat transfer. In addition, increasing micro-pillar side length or decreasing micro-pillar height can delay activation of nucleation sites. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of traditional sliding mode control design subject to the mismatched disturbance. Existing methods fail to provide an efficient and simple solution. To counteract the unmatched disturbance in the system, a new sliding mode control strategy based on a non-smooth integral sliding manifold is proposed. The proposed sliding manifold has two important features. First, it acts like a reduced order disturbance observer since it estimates the mismatched disturbances by itself without any requirement of an additional observer design. Secondly, the system always starts from the sliding surface, hence, there is no reaching phase dynamics. Thus, the system trajectory is insensitive towards the disturbance from the initial point. The proposed method is tested on a coupled tank system to demonstrate its effectiveness. Both the simulation and experimental results are provided. • A non-smooth integral sliding manifold is proposed with modified sliding mode control design. • Act as reduced order disturbance observer to estimate mismatched disturbances without any additional observer design. • System trajectory is insensitive towards the disturbance as there is no reaching phase dynamics. • Proposed work is tested on a coupled tank system to demonstrate its effectiveness. [ABSTRACT FROM AUTHOR]

[Display omitted] Understanding the complex multi-phase interactions are vital for defects reduction in additive manufacturing (AM) of metal matrix composites. In this study, we propose a high-fidelity model to reveal the dynamics of molten pool and reinforcing solid particles during the AM process, using the resolved Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) with bi-directional momentum and energy exchange. Our model is validated against the electron beam melting (EBM) experiments of tungsten-copper composites fabricated with elemental powder blends. The results demonstrate that the interface effect, including the dynamic wetting phenomena and Laplace pressure, play significant roles in the dynamics of reinforcing solid particles. On the other hand, the existence of reinforcing solid particles in the molten pool changes the molten pool size and alters the flow field during the melting process. Although the interface effect causes tungsten particle agglomeration at single track surface, the layer-wise deposition scheme with proper layer thickness eliminates the cluster and promotes the uniform tungsten distribution in the densified bulk sample, which shows the capability of AM to achieve spontaneous dispersion of reinforcing solid particles in the metal matrix. This work provides unprecedented details about the multi-phase dynamics in metal matrix composite AM process. [ABSTRACT FROM AUTHOR]

The study investigates the structural transition pathways of U 3 O 8 under varying temperature and pressure conditions, focusing on both bulk and nanocrystalline forms. The bulk U 3 O 8 is known to undergo reversible phase transitions to a hexagonal structure at temperatures above 150°C and irreversible transitions to a fluorite structure under pressure at ambient temperature. High-pressure XRD experiments reveal a significant decrease in transition pressure for the hexagonal to fluorite phase transition in bulk U 3 O 8 , with the HT-hex phase exhibiting a bulk modulus of 155 ± 21 GPa at 450°C. In 82 nm nanocrystalline U 3 O 8 , the transition from orthorhombic to hexagonal phase is reversible up to 1.0 GPa and 500°C but becomes irreversible above 1.7 GPa. The bulk modulus of the hexagonal phase of nanocrystalline U 3 O 8 is estimated to be 168±12 GPa and 146±16 GPa at 400°C and 500°C, respectively. The findings highlight the complexity of structural transformations in U 3 O 8 and their dependence on temperature and pressure, offering insights valuable for materials science and nuclear reactor engineering. • In U 3 O 8 phase dynamics, pressure triggers fluorite transformation, while temperature increases its kinetics. • Elevated temperatures quadruple the kinetics of the pressure-induced transition to the fluorite structure. • The transition from orthorhombic to hexagonal phases becomes irreversible at ∼ 2 GPa and 500°C. • The hexagonal form of U 3 O 8 exhibits a bulk modulus value of 155 GPa at 450°C. [ABSTRACT FROM AUTHOR]

• Image-based reconstruction and characterization of GDL are conducted considering different fractions of binder, PTFE, and carbon fiber. • Gas-water displacement phase diagram and its correlation with the pore structures are predicted by pore network modeling. • The phase diagram shows a tendency to transit from the viscous to capillary fingering (unfavorable), and capillary fingering to stable displacement (favorable) with an increase in binder content. • Increasing binder content will promote effective water permeability under real operating conditions. Understanding the gas-water flow dynamics in the gas diffusion layer (GDL) is one of the keys to improving the proton exchange membrane fuel cell's (PEMFC) overall performance and avoiding water flooding. Yet, the relationship between the two-phase flow and micro-scale GDL structures (including binder, PTFE, and fiber skeleton) is not well understood. In this study, three-dimensional GDL structures with different fractions of binder contents (φ b = 0 % ∼ 50 %) and a fixed porosity of 75.6 % are confidently reconstructed based on high-resolution images from the confocal microscope, implying that the addition of binder will increase the number of large pores and cause a bimodal throat size distribution through morphology analysis. Thereafter, drainage simulations are performed under a wide range of capillary number (−9 < log Ca <0) and viscosity ratio (−3 < log M < 2) by the pore network model (PNM), which robustly predicts the displacement phase diagram of viscous fingering, capillary fingering, stable displacement, and transitional regime. In the viscous fingering and stable displacement regime, the nonwetting phase saturation (S n w) is nearly the same for different φ b , implying the fluid invading pathway does not change much with the addition of binder. However, in the capillary fingering regime (refer to the actual operating conditions), S n w increases rapidly with φ b at the breakthrough time and its transient value continues to increase until the steady state, which may be attributed to the increased fractions of pores above the capillary threshold attributed by the bimodal throat size distribution. In addition, the effective water permeability increases sharply with φ b , whereas the gas permeability remains almost constant, which means such pore structure alteration by adding the binder is beneficial to water disposal in PEMFC. This research provides insights into delineating the effect of pore and throat size distribution alteration by adding binder on two-phase dynamics in GDL. [ABSTRACT FROM AUTHOR]

Knowledge of the underlying physical mechanisms responsible for the triggering of high-frequency transverse combustion dynamics is of fundamental importance in the development of heavy-duty gas turbine combustors, aircraft engine afterburners, and bipropellant liquid rocket engines. Detailed information about three-dimensional thermoacoustic interactions and local flame dynamics, however, remains largely unknown and unanticipated, mainly because high-amplitude transverse mode instabilities are challenging to excite and detect in well-controlled sub-scale laboratory environments. To overcome this impasse, here we exploit a spatially tailored rectangular injector assembly consisting of ten equidistant horizontal slit nozzles to eliminate the complications of out-of-plane flame dynamics characterization. A total of 56 datasets of self-induced instabilities were acquired over a wide range of operating conditions to understand spatiotemporal phase dynamics and important mode shapes, in conjunction with 2D Rayleigh angle reconstruction and phase-resolved OH PLIF-based local flame front identification. Experimentally, we show that high-frequency transverse instabilities are excited only under high temperature and high thermal power conditions, manifested as non-evanescent pressure fluctuations at 6.50 kHz strongly coupled to the second-order tangential mode of the rectangular combustion chamber. Two vertically-oriented pressure nodal planes and the characteristic phase transition perpendicular to the horizontal slit injector direction are accurately measured and reconfirmed by Helmholtz simulations in terms of their interpositions and spatial orientation. Remarkably, the periodic formation of co-propagating coherent structures and concomitant local flame displacement/pinch-off are revealed to play an important role in driving the high-frequency hydrogen combustion dynamics. [ABSTRACT FROM AUTHOR]

The phase of signals representing cyclic behavioural patterns provides valuable information for understanding the mechanisms driving the observed behaviours. Methods usually adopted to estimate the phase, which are based on projecting the signal onto the complex plane, have strict requirements on its frequency content, which limits their application. To overcome these limitations, input signals can be processed using band-pass filters or decomposition techniques. In this paper, we briefly review these approaches and propose a new one. Our approach is based on the principles of Empirical Mode Decomposition (EMD), but unlike EMD, it does not aim to decompose the input signal. This avoids the many problems that can occur when extracting a signal's components one by one. The proposed approach estimates the phase of experimental signals that have one main oscillatory component modulated by slower activity and perturbed by weak, sparse, or random activity at faster time scales. We illustrate how our approach works by estimating the phase dynamics of synthetic signals and real-world signals representing knee angles during flexion/extension activity, heel height during gait, and the activity of different organs involved in speech production. [ABSTRACT FROM AUTHOR]

We discuss the discrete-to-continuum transition in the description of matter, starting from a cluster of flowing molecules with equal mass and ending up with a non-simple fluid. We account for the fluctuations beyond a local affine approximation of the velocity distribution of molecules within a space window adopted to compute some prominent statistics. The resulting continuum picture accounts for local mass variation in each space window corresponding to a point in the continuum scale. From a statistical viewpoint, every material element is thus considered as a grand-canonical ensemble. So-called C-derivatives account for macroscopic-to-mesoscopic relative motion. When considered for second-rank tensors, they extend Truesdell's derivative and reduce to Oldroyd's one when the macroscopic-to-mesoscopic relative motion vanishes. Fluctuations beyond an affine component best approximating the kinetic energy are summarized into a second-rank symmetric tensor whose time variation enters a balance equation governing transfer from velocity fluctuations to heat. Eventually, we discuss essential elements of thermodynamics in the present setting. What emerges is the possibility of a non-Fourier type heat transfer. The results address computational schemes for field representations of sparse phase dynamics, such as granular materials, and the one of bodies with transport of scattered molecules, such as pollutants in fluids or proteins in biological tissues. • A complete thermomechanical description of the dynamics of sparse phases. • A new view on molecular and/or grain dynamics based on objective derivatives and multi-scale approach. • A view on sparse phases compatible with finite-speed heat propagation. [ABSTRACT FROM AUTHOR]

Building thin-walled titanium alloy skin using conventional laser beam welding (LBW) frequently suffers from undesirable seam quality due to the V-shaped notch; a typical assembly error occurs after skin rolling with a specific sheet thickness range. This work proposed an improved scheme with metal bridging capacity and liquid film stability to overcome this by executing a pulsed laser beam and spot irradiation in a flat-top mode. Welding was performed on 1.5 mm-thick Ti6Al4V sheets configured in the butt joint with a reserved notch geometry, which is 20 degrees between the groove surface. We also conducted numerical modeling and solutions concerning the heat-flow-phase dynamics using an enhanced ray tracing algorithm. Results show that the as-build weld beads, characterized by middle rippers, slight depression, and edge ridges, present superb continuity and uniformity when applying an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. Effective metal bridging across the notch error is achieved at both pulse duration and interval phases due to not only the complete melting of welding side but also the enhanced melt film stability against the surface tension. The cooling of the weld pool starts with a sharp temperature drop at ∼3×105 K/s (on average) during the keyhole collapsing regime, then slows down due to the damped up-down oscillation of the free surface combined with the natural convection-conduction effect. The flow pattern of molten metal changes from squeezing-like to vortexes and finally to a backfilling mode, depending on the evolution of keyhole geometry. Although the keyhole dynamics differs, various process conditions regarding heat input and pulse energy yield effective metal bridging of a single weld spot and sufficient refusion between the adjacent weld spots, ensuring the well-overlapped weld bead formation. [Display omitted] • PLBW Tailored PLBW with top-hat beam spot were performed on Ti6Al4V skin sheets configured in butt joint with a V-shaped notch geometry. • As-build beads present superb appearance with an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. • Metal bridging across notch is initially achieved at root surface and is further enhanced as keyhole advances and grows. • Keyhole collapse promotes melt convection between cold pool edge and hot keyhole tip leading to a sharp cooling stage. • Melt can be squeezed, vortical, or in a backfilling pattern during a typical pulse cycle depending on keyhole regime. [ABSTRACT FROM AUTHOR]

• Representative simulations evaluate gas transport mechanism due to NSZD. • Soil microbiome, fluid flow, multi-component transport and partitioning are considered. • Relative pressure changes and consequent scales of advective / diffusive transport are quantified. • Findings confirm assumptions of diffusion dominance in vapour transport and NSZD. Quantifying the interlinked behaviour of the soil microbiome, fluid flow, multi-component transport and partitioning, and biodegradation is key to characterising vapour risks and natural source zone depletion (NSZD) of light non-aqueous phase liquid (LNAPL) petroleum hydrocarbons. Critical to vapour transport and NSZD is transport of gases through the vadose zone (oxygen from the atmosphere, volatile organic compounds (VOCs), methane and carbon dioxide from the zone of LNAPL biodegradation). Volatilisation of VOCs from LNAPL, aerobic biodegradation, methanogenesis and heat production all generate gas pressure changes that may lead to enhanced gas fluxes apart from diffusion. Despite the importance of the gaseous phase dynamics in the vadose zone processes, the relative pressure changes and consequent scales of advective (buoyancy and pressure driven) / diffusive transport is less studied. We use a validated multi-phase multi-component non-isothermal modelling framework to differentiate gas transport mechanisms. We simulate a multicomponent unweathered gasoline LNAPL with high VOC content to maximise the potential for pressure changes due to volatilisation and to enable the joint effects of methanogenesis and shallower aerobic biodegradation of vapours to be assessed, along with heat production. Considering a uniform fine sand profile with LNAPL resident in the water table capillary zone, results suggest that biodegradation plays the key role in gas phase formation and consequent pressure build-up. Results suggest that advection is the main transport mechanism over a thin zone inside the LNAPL/capillary region, where the effective gaseous diffusion is very low. In the bulk of the vadose zone above the LNAPL region, the pressure change is minimal, and gaseous diffusion is dominant. Even for high biodegradation rate cases, pressure build-up due to heat generation (inducing buoyancy effects) is smaller than the contribution of gas formation due to biodegradation. The findings are critical to support broader assumptions of diffusive transport being dominant in vapour transport and NSZD assessments. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we study the transverse vortex-induced vibrations (VIV) of two rigidly connected circular cylinders of equal size, arranged in a tandem configuration, by means of two-dimensional numerical computations. Results are examined for R e = 250 and a fixed center-to-center separation of 2 D. The dynamic response of the two-cylinder system is investigated in detail over a domain of reduced velocities ranging from U r = 2 to 8. The diverse types of branches are identified, on the basis of their distinct characteristics in the amplitude and frequency responses. Among them, the lower branch is of particular interest as it is quasi-periodic in nature, instead of the periodic regime that is well documented for the isolated cylinder case. By scrutinizing the vorticity dynamics, it reveals that this quasi-periodicity arises from the switching between two flow states, which are essentially distinguished by whether an active gap flow is present. The dynamically rich response leads to a rich variety of phase dynamics, involving phase locking, trapping, slipping and drifting; in particular, phase drifting is indicative of a forthcoming phase jump of 180° between the lift force and the displacement. It is also found that in the initial branch, the excitation of the system is driven by the pressure lift force on the rear cylinder; by contrast, in the lower branch, it is the pressure lift force on the front cylinder that acts as a source of excitation. • The diverse types of response branches are identified. • A rich variety of phase dynamics are captured. • The mechanism for the quasi-periodic nature of the lower branch is proposed. [ABSTRACT FROM AUTHOR]

Classical nonlinear waves exhibit, as a general rule, an irreversible process of thermalization toward the Rayleigh–Jeans equilibrium distribution. On the other hand, several recent experiments revealed a remarkable effect of spatial organization of an optical beam that propagates through a graded-index multimode optical fiber (MMF), a phenomenon termed beam self-cleaning. Our aim here is to evidence the qualitative impact of disorder (weak random mode coupling) on the process of Rayleigh–Jeans thermalization by considering two different experimental configurations. In a first experiment, we launch speckle beams in a relatively long MMF. Our results report a clear and definite experimental demonstration of Rayleigh–Jeans thermalization through light propagation in MMFs, over a broad range of kinetic energy (i.e., degree of spatial coherence) of the injected speckle beam. In particular, the property of energy equipartition among the modes is clearly observed in the condensed regime. The experimental results also evidence the double turbulence cascade process: while the power flows toward the fundamental mode (inverse cascade), the energy flows toward the higher-order modes (direct cascade). In a 2nd experiment, a coherent laser beam is launched into a relatively short MMF length. It reveals an effect of beam cleaning driven by an incipient process of Rayleigh–Jeans thermalization. As discussed through numerical simulations, the fast process of Rayleigh–Jeans thermalization observed in the 1st experiment can be attributed due to a random phase dynamics among the modes, which is favored by the injection of a speckle beam and the increased impact of disorder in the long fiber system. • We compare Rayleigh–Jeans thermalization and beam self-cleaning in multimode fibers. • Beam cleaning occurs through an incipient process of Rayleigh–Jeans thermalization. • Increasing the impact of disorder, complete Rayleigh–Jeans thermalization is observed. • Numerical simulations corroborate the experimental observations. [ABSTRACT FROM AUTHOR]

Can-to-can acoustic interactions in a circumferential network of lean-premixed combustors have a prominent role in the development of complicated modal dynamics and large-scale pattern formations in can-annular gas turbine combustion systems. Despite recent progress in understanding these instabilities, however, previous relevant studies have been limited to an even number of constituent combustors; a fundamental characteristic of the modal dynamics in a can-annular arrangement consisting of an odd number of combustors remains unknown. To address this question, we compare key features of thermoacoustic instabilities in four-coupled (N = 4) and five-coupled (N = 5) can-annular combustor configurations obtained over a broad range of operating conditions. In conjunction with FEM-based Helmholtz simulations, our experimental data show that the dynamic behavior of the even- N case is characterized by the well-known interaction pattern, out-of-phase alternating modulations among the networked combustors. For the odd- N case, however, the can-annular system features complex phase dynamics originating from simultaneous excitation of the degenerate mode pair. We highlight that the development of self-excited azimuthal instabilities in the annular cross-talk section is associated with the modal interaction of the degenerate pair in the odd- N configuration. The initially degenerate pair can be split into two closely-spaced non-degenerate modes, and in consequence their modal interaction gives rise to a periodic transition between spinning and standing azimuthal modes in the annulus. Despite the formation of remarkably different inter-combustor interactions in the two can-annular configurations, however, the entire set of instability data collapses into very similar frequency regimes, suggesting the importance of flame-acoustic interactions occurring within each combustor, namely intra-combustor interactions. [ABSTRACT FROM AUTHOR]

Designing controllers directly from data often requires choosing a reference closed-loop model, whose behavior should be reproduced as tightly as possible by the actual closed-loop system via the selected controller structure (e.g., PID). Within a linear setting, we present a derivative-based approach to jointly select the reference model and controller parameters directly from data. The proposed strategy allows one to maximize closed-loop performance while enforcing user-defined constraints, and it is designed to handle non-minimum phase dynamics. The effectiveness of the proposed approach is shown through three numerical case studies. [ABSTRACT FROM AUTHOR]

Emulsion stability is important in many environmental and industrial applications. Unstable emulsions tend to have a layered structure which will evolve in space and time. Magnetic Resonance (MR) is a nondestructive method that can be used to study emulsion instability based on relaxation times (T 1 , T 2), and/or diffusion (D). The bulk transverse relaxation lifetime (T 2) is the most useful parameter for analysis. Since breaking of emulsions creates different layers and phases, spatially resolved T 2 data is more valuable than bulk whole sample data. Previous literature studies were principally based on bulk T 1 , T 2 or self-diffusion measurements without spatial resolution. In this study, for the first time, spatially resolved T 2 distributions were used to examine oil and water behavior during emulsion breaking. Diluted bitumen was used as the oil phase in a synthetic emulsion. Measurements undertaken included spatially resolved T 2 distribution measurements and T 1 -T 2 relaxation correlation measurements. The results reveal changes in the relaxation times of oil and water caused by changes in the dynamics of the water and oil during emulsion breaking. In each layer of the sample, comparing peak T 2 values with bulk T 2 values of different components gives an insight into phase environments. Water and oil content in each layer was resolved by using peak areas of the T 2 distribution. The results of T 2 distribution imaging were consistent with optical microscopy images, which showed W/O emulsions in the oil dominant region and complex W/O/W emulsions in the water dominant region of the sample. With the above information one can obtain full spatial and temporal information on evolving phases as well as kinetics of phase dynamics in emulsion breaking. [Display omitted] • MR T 2 mapping helps identify different layers of an emulsion sample and observe their evolution. • Optical microscopy images confirmed MR T 2 mapping results. • The oil- and water-dominant regions were characterized by W/O and W/O/W emulsions respectively. • Spatial and temporal information on dispersed and free phases in the emulsion breaking is obtained. [ABSTRACT FROM AUTHOR]

• A new chemical kinetic model for gas-phase CH 4 coupling in nanosecond pulsed discharges is presented. • The transient behavior of the nanosecond pulsed discharge is described. • At 1 bar and 2 bar, the production of C 2 H 2 is favoured due to the efficient dehydrogenation of C 2 H 3. • From 3 bar to 5 bar, the principal channel for C 2 H 3 conversion is the re-hydrogenation to C 2 H 4. • C 2 H 4 is the main product when operating at > 2 bar. We present a zero-dimensional kinetic model to characterise specifically the gas-phase dynamics of methane conversion in a nanosecond pulsed discharge (NPD) plasma reactor. The model includes a systematic approach to capture the nanoscale power discharges and the rapid ensuing changes in electric field, gas and electron temperature, as well as species densities. The effects of gas temperature and reactor pressure on gas conversion and product selectivity are extensively investigated and validated against experimental work. We discuss the important reaction pathways and provide an analysis of the dynamics of the heating and cooling mechanisms. H radicals are found to be the most populous plasma species and they participate in hydrogenation and dehydrogenation reactions, which are the dominant recombination reactions leading to C 2 H 4 and C 2 H 2 as main products (depending on the pressure). [ABSTRACT FROM AUTHOR]

• A novel hybrid concentrating photovoltaic-pumped two-phase loop system is modeled. • A multi-parameter optimization problem with several constraints is formulated. • System thermodynamic under changing solar irradiation intensity is optimized. • Efficient PV cell cooling and waste heat utilization are simultaneously addressed. • The hybrid system brings about 6.9% overall exergy efficiency improvement. Linear concentrating photovoltaic (LCPV) is a promising technology to increase the power density of the solar power generation system. However, the efficiency of LCPV is highly undermined due to inefficient thermal management. Active cooling-based thermal management via a mechanically pumped two-phase loop (MPTL) system can facilitate the heat transfer across LCPV. However, efficient thermal management and waste heat utilization are still challenges due to high heat flux, complex two-phase dynamics, strong internal couplings and dynamic external environment. To simultaneously address these crucial parameters, this paper presents a mathematical model for the hybrid LCPV-MPTL system, including two-phase flow and other auxiliary components. An iterative solution algorithm is proposed to derive the steady-state values under different conditions. Simulations under four operating conditions have been performed based on the developed model, indicating the effects of each parameter. A multi-parameter optimization problem with several constraints is formulated by taking the changing solar irradiation intensity and other environmental factors into account, maximizing the net output of electrical energy while satisfying the safety and operational requirements. Finally, exergy analysis is carried out, showing that the hybridization of MPTL with LCPV can improve its overall exergy efficiency by 6.9%, resulting in high performance PV with greatly controlled cell temperature. In all, the scientifically viable thermal management solution and the underlying design guidelines can be inferred for industrial applications. [ABSTRACT FROM AUTHOR]

• CR-SOAs are employed to realize the Set-Reset latch and D Flip-Flop at 120 Gb/s. • The Q-factor is used to evaluate the all-optical latches' performance, including ASE noise. • The results demonstrate that CR-SOAs can achieve a high Q-factor while implementing these two basic latches at high speeds. Lightwave communication systems, optical random memories, and photonic encryption/decryption are important applications that rely on all-optical latches. For the first time, the carrier reservoir semiconductor optical amplifiers (CR-SOAs) are employed to simulate two basic optical latches, Set-Reset (SR) latch, and D Flip-Flop, at a data rate of 120 Gb/s. All-optical NAND and NOT logic operations are used to build these latches, which are implemented using Mach-Zehnder interferometers (MZIs) with CR-SOAs. In the presence of the amplified spontaneous emission noise, the variation of the output quality factor (Q-factor) against the CR-SOA key operating parameters is studied. This is achieved by exploiting and numerically solving a set of coupled partial differential equations that describe the CR-SOAs gain and phase dynamics when operated as nonlinear elements and embedded in MZIs. The results demonstrate that CR-SOAs-based MZIs can achieve a high Q-factor while implementing the logical SR latch and D Flip-Flop at a high speed of 120 Gb/s. [ABSTRACT FROM AUTHOR]

• Joule heating phenomenon is incorporated in the AC Josephson effect. • The phase and temperature dynamic states are discussed for various parameters. • Device state diagrams are realized for Josephson weak-link – shunted and unshunted. • A useful thermal model as a guide for the experiments with weak-link-based devices. Superconducting weak-link (WL), behaving like a Josephson junction (JJ), is fundamental to many superconducting devices such as nanoSQUIDs, single-photon detectors, and bolometers. The interplay between unique nonlinear dynamics and inevitable Joule heating in a JJ leads to new characteristics. Here, we report a time-dependent model incorporating thermal effect in the AC Josephson regime for a Josephson WL shunted by a resistor together with an inductor to investigate the dynamics as well as the resulting current-voltage characteristics. We find that the dynamic regime where phase and temperature oscillate simply widens due to a pure resistive shunt. However, a significant inductive time-scale in the shunt loop, competing with the thermal time-scale, introduces high-frequency relaxation oscillations in the dynamic regime. Based on numerical analysis, we present state diagrams for different parameter regimes. Our model is a guide for better controlling the parameters in the experiments of WL-based devices. [ABSTRACT FROM AUTHOR]

The motion of debris flows is controlled by the interaction of their fluid and solid components. In this work, a general two-phase model framework (Pudasaini, 2012) is adopted which captures the coupled effects of the individual phase dynamics to the overall mobility. While solving the model equations, the fluid phase is treated as a viscous Newtonian liquid while the solid phase is considered to be a granular material obeying a recently developed visco-inertial constitutive rheology. Solid and fluid components in the mixture are coupled through the interaction forces, namely buoyancy, drag, and virtual mass. The model is calibrated against results from instrumented flume experiments and from field measurements of saturated, channelized debris flows. The numerical model captures the enhanced mobility of debris flows due to the presence of interstitial fluid and provides better predictions of the flow dynamics relative to those obtained from single-phase frameworks. Better modeling agreement is obtained for granular-fluid flows with relatively high fluid content. The model is then used to simulate real debris flow events, including a case that occurred in the proximity of the Sichuan-Tibet Railway, where good agreement with reported field measurements is obtained. This modeling framework is expected to improve mitigation strategies for debris flows hazards. • Debris flows are simulated as two-phase flows where the solid phase is modelled using a visco-inertial constitutive rheology. • The numerical model captures the enhanced mobility and phase separation in debris flows. • Simulations with visco-inertial model improves predictions against dry granular flow rheology. [ABSTRACT FROM AUTHOR]

The injection of liquid fuel at supercritical pressures is a relevant but overlooked topic in combustion. Typically, the role of two-phase dynamics is neglected under the assumption that the liquid will rapidly transition to a supercritical state. However, a transcritical domain exists where a sharp phase interface remains. This scenario is common in the early times of liquid fuel injection under real-engine conditions involving hydrocarbon fuels. Under such conditions, the dissolution of the oxidizer species into the liquid phase is accelerated due to local thermodynamic phase equilibrium (LTE) and vaporization or condensation can occur at multiple locations along the interface simultaneously. Fluid properties vary strongly under species and thermal mixing, with liquid and gas mixtures becoming more similar near the interface. As a result of the combination of low, varying surface-tension force and gas-like liquid viscosities, small surface instabilities develop early. The mixing process, interface thermodynamics, and early deformation of a cool liquid n -decane jet surrounded by a hotter moving gas initially composed of pure oxygen are analyzed at various ambient pressures and gas velocities. For this purpose, a two-phase, low-Mach-number flow solver for variable-density fluids is used. The interface is captured using a split Volume-of-Fluid method, generalized for the case where the liquid velocity is not divergence-free and both phases exchange mass across the interface. The importance of transcritical mixing effects over time for increasing pressures is shown. Initially, local deformation features appear that differ considerably from previous incompressible works. Then, the minimal surface-tension force is responsible for generating overlapping liquid layers in favor of the classical atomization into droplets. Thus, surface-area growth at transcritical conditions is mainly a consequence of gas-like deformations under shear rather than spray formation. Moreover, the interface can be easily perturbed in hotter regions submerged in the faster oxidizer stream under trigger events such as droplet or ligament impacts. The net mass exchange at high pressures limits the liquid-phase vaporization to small liquid structures. • Transcritical liquid injection displays different features than subcritical flows. • Phase equilibrium allows the coexistence of two fluid phases at supercritical pressures. • Surface deformation is highly affected by local mixing in both phases. • The mechanism for surface-area growth differs from traditional atomization. • Condensation at high pressure limits the global vaporization rate of the liquid phase. [ABSTRACT FROM AUTHOR]

No cigarette smoke test matrix is without limitation, due to the complexity of the starting aerosol and phase to phase dynamics. It is impossible to capture all chemicals at the same level of efficiency, therefore, any test matrix will inadvertently or by design fractionate the test aerosol. This case study examines how four different test matrices derived from cigarette smoke can be directly compared. The test matrices assessed were as follows, total particulate matter (TPM), gas vapour phase (GVP), a combination of TPM + GVP and whole aerosol (WA). Here we use an example assay, the mouse lymphoma assay (MLA) to demonstrate that data generated across four cigarette smoke test matrices can be compared. The results show that all test matrices were able to induce positive mutational events, but with clear differences in the biological activity (both potency and toxicity) between them. TPM was deemed the most potent test article and by extension, the particulate phase is interpreted as the main driver of genotoxic induced responses in the MLA. However, the results highlight that the vapour phase is also active. MLA appeared responsive to WA, with potentially lower potency, compared to TPM approaches. However, this observation is caveated in that the WA approaches used for comparison were made on a newly developed experimental method using dose calculations. The TPM + GVP matrix had comparable activity to TPM alone, but interestingly induced a greater number of mutational events at comparable relative total growth (RTG) and TPM-equivalent doses when compared to other test matrices. In conclusion, this case study highlights the importance of understanding test matrices in response to the biological assay being assessed and we note that not all test matrices are equal. • Four cigarette smoke test matrices were assessed using mouse lymphoma assay (MLA). • Total particulate matter (TPM), gas vapour phase (GVP) and TPM + GVP were assessed. • Whole aerosol was also compared against fractionation approaches. • All cigarette smoke test matrices were able to induce positive mutational events. • Differences in both potency and toxicity were observed between test matrices. [ABSTRACT FROM AUTHOR]

We report a procedure for measuring variations of the magnetic field gradients generated by a macroscopic coil. A micromechanical cantilever oscillator covered with a magnetic material is used to detect variations of the magnetic force field at distances exceeding several times the coil diameter (4 mm). The detection is based on the phase of the first eigenmode of the cantilever while modulating the magnetic field at low frequencies. The nanoscale oscillation of the cantilever along with the high-quality resonance factor are responsible for a coherent oscillation allowing high sensitivity. A detection sensitivity, under ambient conditions, of the order of 10−13 T/nm2 is estimated with the help of numerical calculations. The approach is useful for evaluating the spatial variation of the magnetic field gradients generated by any source of magnetic field when the magnetic field can be modified at rates below the resonant frequency of the cantilever. These results can be useful for gradient fields monitoring in macro- and micro-scale magnetic resonance imaging, non-contact electric currents identification from stray magnetic fields, electrical power monitoring, 3D-magnetic fields mapping, or miniature orientation devices. [Display omitted] • The detection of magnetic field gradients of macroscopic coils is realized with a micromechanical cantilever oscillator. • The detection results from the magnetostatic interaction being possible at large distances. • A sensitivity of the order of 10−13 T/nm2 is estimated. [ABSTRACT FROM AUTHOR]

We explore the structural, energetic and dynamic aspects of the excited-state intramolecular proton transfer process of 5-hydroxychromone using the trajectory surface hopping method. Gas-phase dynamics simulations show that the proton transfer on the "bright" S 1 (π π ∗ ) is essentially a barrierless event and occurs on a timescale of about 24 fs. Our findings also demonstrate the possible proton transfer via "dark" S 2 (n π ∗) after a successful hop from S 1 to S 2 via an accessible conical intersection that lies energetically and spatially nearby the Franck–Condon point of S 1. An intrinsic barrier on S 2 would delay the proton transfer dynamics (∼ 100 fs). The proton transfer occurs entirely via S 1 in the presence of acetonitrile as a solvent. Computed energetics and geometries associated with key stationary points in the solvent environment are similar to gas-phase estimates, suggesting negligible solvation effects on the rapidity of the proton transfer via S 1 in 5-hydroxychromone. [Display omitted] • Barrierless proton transfer on S 1. • Extremely rapid ESIPT (∼ 25 fs). • Negligible implicit solvation effects on the excited-state dynamics. • Predicted single emission with large Stokes shift. [ABSTRACT FROM AUTHOR]

• First interface-resolved computational study of its kind on the simultaneous breakup and vaporization of hydrocarbon fuel droplets as they interact with shocks. • Shock induced interfacial instabilities are suppressed when the liquid droplet undergo phase change. • Lower Mach number shock waves lead to faster vaporization as compared to higher Mach number shocks. This study investigates the fundamental mechanisms underlying the deformation, fragmentation, and vaporization of volatile liquid fuel droplets impacted by a normal shock wave using a high-fidelity, VOF-DIM (volume of fluid - diffuse interface method)-based framework. The theoretical and mathematical formulation of this multiphase, multi-fluid problem is based on a modified 5-equation Kapila formulation with pressure-relaxation, viscous, and surface tension effects. A thermal-mechanical-chemical equilibrium relaxation procedure is implemented to simulate vaporization. The framework is first validated against measurements of shock impact on a non-vaporizing water droplet; the computations agree well with the experimental data. Next, the vaporization model is validated against the d 2 law, showing excellent agreement. This is followed by a systematic investigation of the atomization and vaporization physics of a n -dodecane droplet as it interacts with a shock wave traveling at a Mach number of 6.5. To compare and contrast the effect of vaporization on breakup physics, two numerical experiments were conducted with and without the vaporization model. It is found that when the vaporization model is not enabled, the gaseous and liquid phase dynamics are similar to that of non-vaporizing water droplet-shock wave interactions. However, when vaporization is enabled, aerothermal heating from the shock impact and high temperatures in the post-shock region provide sufficient heating for volatile liquid droplets to undergo phase change and the breakup behaviors are significantly different from the non-vaporizing counterpart. Furthermore, it is found that vaporization is a strong function of the shock strength – low Mach number shock waves lead to higher vaporization. [ABSTRACT FROM AUTHOR]

In the data analysis of oscillatory systems, methods based on phase reconstruction are widely used to characterize phase-locking properties and inferring the phase dynamics. The main component in these studies is an extraction of the phase from a time series of an oscillating scalar observable. We discuss a practical procedure of phase reconstruction by virtue of a recently proposed method termed iterated Hilbert transform embeddings. We exemplify the potential benefits and limitations of the approach by applying it to a generic observable of a forced Stuart–Landau oscillator. Although in many cases, unavoidable amplitude modulation of the observed signal does not allow for perfect phase reconstruction, in cases of strong stability of oscillations and a high frequency of the forcing, iterated Hilbert transform embeddings significantly improve the quality of the reconstructed phase. We also demonstrate that for significant amplitude modulation, iterated embeddings do not provide any improvement. • Hilbert transform is used for phase reconstruction from scalar signals. • A signal from a driven oscillator has both phase and amplitude modulation. • Iterated Hilbert transform embeddings provide a significant improvement. [ABSTRACT FROM AUTHOR]