Dynamics Interface Research Articles

Quasiperiodic Oscillations of Flare Loops and Slipping Motion of Ribbon Substructures during a C-class Flare

Quasiperiodic oscillations in solar-flaring emission have been observed over the past few decades. To date, the underpinning processes resulting in the quasiperiodic oscillations remain unknown. In this paper, we report a unique event that exhibits both the long-duration quasiperiodic intensity oscillations of flare loops and the quasiperiodic slipping motion of ribbon substructures during a C9.1-class flare (SOL2015-03-15-T01:15), using the observations from the Solar Dynamics Observatory and Interface Region Imaging Spectrograph. The high-temperature flare loops rooted in the straight part of ribbons display a “bright–dim” intensity oscillation, with a period of about 4.5 minutes. The oscillation starts just after the flare onset and lasts over 3 hr. Meanwhile, the substructures within the ribbon tip display the quasiperiodic slipping motion along the ribbon at 1400 Å images, which has a similar periodicity to the stationary intensity oscillation of the flare loops in the straight part of the flare ribbons. We suggest that the quasiperiodic pattern is probably related to the loop-top dynamics caused by the reconnection outflow impinging on the flare loops.

Dynamical and combinatorial coding by MAPK p38 and NFκB in the inflammatory response of macrophages

Macrophages sense pathogens and orchestrate specific immune responses. Stimulus specificity is thought to be achieved through combinatorial and dynamical coding by signaling pathways. While NFκB dynamics are known to encode stimulus information, dynamical coding in other signaling pathways and their combinatorial coordination remain unclear. Here, we established live-cell microscopy to investigate how NFκB and p38 dynamics interface in stimulated macrophages. Information theory and machine learning revealed that p38 dynamics distinguish cytokine TNF from pathogen-associated molecular patterns and high doses from low, but contributed little to information-rich NFκB dynamics when both pathways are considered. This suggests that immune response genes benefit from decoding immune signaling dynamics or combinatorics, but not both. We found that the heterogeneity of the two pathways is surprisingly uncorrelated. Mathematical modeling revealed potential sources of uncorrelated heterogeneity in the branched pathway network topology and predicted it to drive gene expression variability. Indeed, genes dependent on both p38 and NFκB showed high scRNAseq variability and bimodality. These results identify combinatorial signaling as a mechanism to restrict NFκB-AND-p38-responsive inflammatory cytokine expression to few cells.

Magnetic Fields and Plasma Heating in the Sun’s Atmosphere

We use the first publicly available data from the Daniel K. Inouye Solar Telescope to track magnetic connections from the solar photosphere into the corona. We scrutinize relationships between chromospheric magnetism and bright chromospheric, transition region, and coronal plasmas. In 2022 June, the Visible Spectro-Polarimeter (ViSP) instrument targeted unipolar network within a decaying active region. ViSP acquired rastered scans with longitudinal Zeeman sensitivities of 0.25 Mx cm−2 (Fe i, 630.2 nm) and 0.5 Mx cm−2 (Ca ii, 854.2 nm). ViSP was operated in a “low” resolution mode (0.″214 slit width, spectral resolution R≈70,000 ) to produce polarization maps over a common area of 105″ × 50″. Data from the Solar Dynamics Observatory and Interface Region Imaging Spectrograph are combined to ask: Why is only a fraction of emerging flux filled with heated plasma? What is the elemental nature of the plasmas? No correlations were found between heated plasma and the properties of chromospheric magnetic fields derived from the weak field approximation, on scales below supergranules. Processes hidden from our observations control plasma heating. While improved magnetic measurements are needed, these data indicate that “the corona is a self-regulating forced system.” Heating depends on the state of the corona, not simply on boundary conditions. Heating models based upon identifiable bipolar fields, including cool loops, tectonics, and observable magnetic reconnection, are refuted for these regions with unipolar chromospheric magnetic fields.

Investigation of control performance on an absorption/stripping system to remove CO2 achieving clean energy systems

Control study is crucial to ensure smooth operation of any unit operation for clean energy system. There has been growing attention on the utilization of advanced model-based controllers in control studies for CO2 capture. However, such advanced controllers are expensive hence proper performance justifications are needed prior to investment. In the current study, both Proportional-Integral (PI) and Model Predictive Control (MPC) control strategies are investigated and implemented on a pilot scale natural gas CO2 absorption/ stripping system running at higher pressure as well as higher CO2 content, utilizing MATLAB/SIMULINK-Aspen Plus Dynamics interface. The novelty of the work is mainly on the investigation study between the efficiency of the standard PI and MPC controllers for a high pressure and high CO2 content pilot-scale CO2 absorption system. For such high pressure and high CO2 content system, it is imperative to evaluate whether special focus on the control strategy is needed or not. This work simulates and investigates the dynamic behavior and performances of PI and MPC controllers of a high-pressure absorption/stripping system. In addition, a second order model of the system has been developed, which is useful for future studies. Controller performance of the Proportional-Integral (PI) and Model Predictive Controller (MPC) are compared using the features of the responses as well as the residual error index i.e., Integral Absolute Error (IAE). The performance of the PID and MPC controllers based on set point tracking of both the controlled variables for 5% and 15% step changes have been evaluated. Compared to the PI controller, the MPC controller has no peak overshoots, i.e., it shows 10% and 2.86% lower error in the IAE index, and it is capable of handling interactions between the variables of the absorption/stripping system.

Theoretical and experimental study on interface stiffness measurement of rough surface using improved acoustic model

Structural health monitoring (SHM) of interface stiffness is of great significance in many fields, such as accurate rotor dynamics modeling and interface friction performance analysis. Acoustic wave is an important interface detection method. However, the interface mechanics and elastic wave theory are relatively independent, and the interaction mechanism between the contact asperity parameters and the energy transfer of elastic waves has not been thoroughly explored. The existing interface stiffness detection indexes do not consider the uncertainty of boundary parameters, which easily leads to the degradation of detection performance and limits the promotion of interface stiffness detection. In this paper, we proposed an acoustic model considering contact interface and boundary effects integrating microwave transmission line theory. A new interface stiffness detection index is constructed to ensure the robustness of the detection results. The relationship between contact parameters and elastic wave energy transfer is analyzed, and the robustness of different detection indexes and the uncertainty of different detection methods are compared. The experimental results of the pressure-bearing connection structure are obtained to verify the correctness of the acoustic model and the feasibility of the detection method. The proposed method is further applied to multi-bolted structures, and the robustness of the proposed method is discussed. The results show that the proposed method has the ability of in-situ interface stiffness detection and potential engineering utility.

A Novel Dynamic and Fuzzy Value Stream Mapping (DFVSM): System Dynamics and Fuzzy Logic Integration

Value stream mapping (VSM) is a method to identify waste and activities that do not add value. One of its main disadvantages is that the parameters used in the process and material flows are deterministic. The motivation of this research is to improve the reliability of the estimation of the lead time in VSM, transitioning from a static model to a dynamic model that incorporates uncertainty and imprecision in the data, as well as to develop a novel dynamic and fuzzy value stream mapping (DFVSM) based on integrating system dynamics and fuzzy logic. One of the main contributions of this research is to develop a fuzzy system in the same system dynamics interface that incorporates uncertainty and vagueness to the efficiency and effectiveness percentage variable (OEE%) to increase the reliability of the delivery time planning. The stages of DFVSM are explicitly described and applied to real data for a textile company in southern Guanajuato. A sensitivity analysis of the proposed model was integrated which identifies the critical factors for the delivery of the order, and achievable times were proposed for the delivery times of the supplier and the client, thus reducing the expected delivery time by 28%. One of the relevant conclusions of this work is that, to plan the lead time of an order, the uncertainty of the main parameters such as supplier and customer shipping times be considered to satisfy the customer.

A molecular dynamics study of calcium silicate hydrates-aggregate interfacial interactions and influence of moisture

The interface properties between hydrated cement paste (hcp) and aggregates largely determine the various performances of concrete. In this work, molecular dynamics simulations were employed to explore the atomistic interaction mechanisms between the commonly used aggregate phase calcite/silica and calcium silicate hydrates (C-S-H), as well as the effect of moisture. The results suggest that the C-S-H/calcite interface is relatively strong and stable under both dry and moist conditions, which is caused by the high-strength interfacial connections formed between calcium ions from calcite and high-polarity non-bridging oxygen atoms from the C-S-H surface. Silica can be also adsorbed on the dry C-S-H surface by the H-bonds; however, the presence of water molecules on the interface may substantially decrease the affinities. Furthermore, the dynamics interface separation tests of C-S-H/aggregates were also implemented by molecular dynamics. The shape of the calculated stress-separation distance curves obeys the quasi-static cohesive law obtained experimentally. The moisture conditions and strain rates were found to affect the separation process of C-S-H/silica. A wetter interface and smaller loading rate may lead to a lower adhesion strength. The mechanisms interpreted here may shed new lights on the understandings of hcp/aggregate interactions at a nano-length scale and creation of high performance cementitious materials.

EVA enhances the interfacial strength of EPS concrete: a molecular dynamics study

Expanded polystyrene (EPS) concrete has high environmental and economic benefits. However, the difference in physical and chemical properties leads to a weak interface between EPS and concrete, which limits the use of EPS concrete. Based on the macro experiment of Ethylene Vinyl Acetate Copolymer (EVA) modified EPS concrete, two molecular dynamics interface models of EPS/C-S-H and EPS/EVA/C-S-H were constructed by molecular dynamics simulation, and their interface strengthening mechanism was discussed. The results of interfacial interaction analysis show that EVA increases the interfacial interaction energy and binding energy between EPS and C-S-H, and improves the adhesion between EPS and cement base. The results of radial distribution function analysis show that in the model with the modifier, there are not only Van der Waals forces and hydrogen bonds in the model without the modifier, but also strong interactions such as Ca - = O and OT - = O. The results of mechanical property analysis show that the elastic modulus of EPS concrete interface model after adding modifier is improved, and its interface properties are improved. The molecular dynamics simulation carried out in this paper shows that EVA acts as a bridge between EPS and C-S-H and enhances its interfacial properties. This study can provide basic theoretical support for the application of EPS concrete and reference for the development of high-performance composite cement-based materials.

Analytical model for total ionizing dose-induced excess base current in PNP BJTs

This work analytically models the crucial physical mechanisms accountable for the defect kinetics and the degradation of base current in PNP BJTs. Both the space charge and bimolecular mechanisms have been incorporated to elicit the defect dynamics (oxide charge and interface trap) following ionization radiation. Thereafter, two novel insights into the ionization damage on SiO2 of bipolar structure are provided, which includes the coupled effect of the two defect mechanisms and the existence of an “additional” hydrogen sensitivity in the bimolecular mechanism. A previous device model has been updated to describe the response of base current degradation to defects build-up. Further, a closed-form compact expression for the excess base current is provided, which is an explicit function of the total ionizing dose, dose rate, and hydrogen concentration. The new model closely fits the experimental data from several devices, including RF25 capacitor, gate controlled lateral PNP BJT, and LM124 amplifier. Our model delivers a practical approach to deduct the oxide charge modulation effect on excess base current. Thereafter, the relation between the modified excess base current and total ionizing dose is linear. Furthermore, this work suggests a practical approach, called as “offset current approach”, to predict the excess base in PNP BJTs at low dose rate.

Multibody system dynamics interface modelling for stable multirate co-simulation of multiphysics systems

Many industrial applications benefit from predictive computer simulation to reduce costs and time, and shorten product development cycle. Computational multibody system dynamics formalisms and software tools have proved to be particularly useful in the simulation of machinery and mechanical systems. Nowadays, however, the complexity of the applications under study often makes it necessary to consider the interaction of mechanical systems with other components of different nature, physical behaviour, and time scale, such as hydraulics or electronics. Co-simulation is an increasingly important approach to formulate and solve the dynamics of these multiphysics setups. In these, modelling techniques and solvers that are tailored to the requirements of each subsystem execute in parallel and are coupled via the exchange of a limited number of inputs and outputs at certain communication times. Co-simulation has clear potential in the modelling of complex engineering systems. On the other hand, there are also challenges. The use of co-simulation may compromise the stability of the numerical solution, especially when non-iterative coupling schemes are used.In this work, we introduce a modelling technique to improve the dynamic interfacing of mechanical systems in co-simulation setups, based on a reduced representation of multibody systems. This reduced order model is used to obtain a physically meaningful prediction of the evolution of the multibody subsystem dynamics that enables the improvement of the solution of other subsystems. The technique is illustrated in the co-simulation of some examples that include both mechanical and hydraulic components. Results show that dynamic interfaces based on reduced models can be used to improve the stability of non-iterative co-simulation schemes in multiphysics engineering systems, enabling the use of larger communication step-sizes.

Characteristics of the safety climate in teams with world-class safety performance on construction projects in South Africa

Accidents and incidents in the construction environment are not reduced or eliminated effectively, despite numerous efforts made to improve health and safety in the industry. An extensive field of research has been conducted on how teams in the construction environment interact to deliver a project successfully in terms of cost, quality and time. Previous research exists on how team dynamics interface with safety, but is found to be of different focus or markets than this study. This study aims to determine the characteristics of the safety climate that exists in construction teams in South Africa in terms of world-class safety performance, when compared to teams with poor safety performance. An adaptation of the modified safety pyramid (Zohar, 2010) provides a useful conceptual model to investigate the link between safety performance and safety climate related to construction teams. By combining observations from literature and predominantly adapting the Safety Climate Questionnaire (SCQ), a number of directly measurable factors are identified that can be correlated with safety performance and utilised in this investigation to identify the unique characteristics of safety climate in construction teams with world-class safety performance. The characteristics of the safety climate in construction teams were divided into eight groups, namely work pressure, incident investigation, adequacy of procedures, communication and training, relationships, personal protective equipment, spares, and safety. The framework developed in previous studies is used for assessing the responses of safety users to that of safety performance observations. It is found that relationships within an organisation are a major contributory factor in safety performance, but also the way in which the safety climate is enforced in an inclusive management style through proper procedure, training and communication. This also supports the results of Cohen (1977). Keywords: Construction teams, safety climate

Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396

AbstractImproved measurements of the photospheric and chromospheric three‐dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multiinstrument data acquired during a two‐week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near‐infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si I λ 1082.7 nm line, the chromospheric He I λ 1083.0 nm triplet, and the photospheric Ca I λ 1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick‐look maps with those obtained with the “Stokes Inversions based on Response functions” (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Charge-Disproportionation Symmetry Breaking Creates a Heterodimeric Myoglobin Complex with Enhanced Affinity and Rapid Intracomplex Electron Transfer.

We report rapid photoinitiated intracomplex electron transfer (ET) within a "charge-disproportionated" myoglobin (Mb) dimer with greatly enhanced affinity. Two mutually supportive Brownian Dynamics (BD) interface redesign strategies, one a new "heme-filtering" approach, were employed to "break the symmetry" of a Mb homodimer by pairing Mb constructs with complementary highly positive and highly negative net surface charges, introduced through D/E → K and K → E mutations, respectively. BD simulations using a previously developed positive mutant, Mb(+6) = Mb(D44K/D60K/E85K), led to construction of the complementary negative mutant Mb(-6) = Mb(K45E, K63E, K95E). Simulations predict the pair will form a well-defined complex comprising a tight ensemble of conformations with nearly parallel hemes, at a metal-metal distance ∼18-19 Å. Upon expression and X-ray characterization of the partners, BD predictions were verified through ET photocycle measurements enabled by Zn-deuteroporphyrin substitution, forming the [ZnMb(-6), Fe(3+)Mb(+6)] complex. Triplet ET quenching shows charge disproportionation increases the binding constant by no less than ∼5 orders of magnitude relative to wild-type Mb values. All progress curves for charge separation (CS) and charge recombination (CR) are reproduced by a generalized kinetic model for the interprotein ET photocycle. The intracomplex ET rate constants for both CS and CR are increased by over 5 orders of magnitude, and their viscosity independence is indicative of true interprotein ET, rather than dynamic gating as seen in previous studies. The complex displays an unprecedented timecourse for CR of the CS intermediate I. After a laser flash, I forms through photoinduced CS, accumulates to a maximum concentration, then dies away through CR. However, before completely disappearing, I reappears without another flash and reaches a second maximum before disappearing completely.

Generalization and application of the flux-conservative thermodynamic equations in the AROME model of the ALADIN system

Abstract. General yet compact equations are presented to express the thermodynamic impact of physical parameterizations in a NWP or climate model. By expressing the equations in a flux-conservative formulation, the conservation of mass and energy by the physics parameterizations is a built-in feature of the system. Moreover, the centralization of all thermodynamic calculations guarantees a consistent thermodynamical treatment of the different processes. The generality of this physics–dynamics interface is illustrated by applying it in the AROME NWP model. The physics–dynamics interface of this model currently makes some approximations, which typically consist of neglecting some terms in the total energy budget, such as the transport of heat by falling precipitation, or the effect of diffusive moisture transport. Although these terms are usually quite small, omitting them from the energy budget breaks the constraint of energy conservation. The presented set of equations provides the opportunity to get rid of these approximations, in order to arrive at a consistent and energy-conservative model. A verification in an operational setting shows that the impact on monthly-averaged, domain-wide meteorological scores is quite neutral. However, under specific circumstances, the supposedly small terms may turn out not to be entirely negligible. A detailed study of a case with heavy precipitation shows that the heat transport by precipitation contributes to the formation of a region of relatively cold air near the surface, the so-called cold pool. Given the importance of this cold pool mechanism in the life cycle of convective events, it is advisable not to neglect phenomena that may enhance it.

Stability limits of n-nonane calculated from molecular dynamics interface simulations

Based on molecular dynamics simulation of the vapor-liquid interface, the classical thermodynamic spinodal for n-nonane is estimated using an earlier developed method. The choice of n-nonane as investigated molecule originates from the question whether a deviation from the spherical symmetry of a molecule affects the prediction of the stability limit data. As a result, we find that the estimated stability limit data for n-nonane are consistent within the experimental data available for the homologous series of the n-alkanes. It turns out that the slight alignment of the molecules parallel to the interface reported in the literature does not affect the method of transferring interface properties to the bulk phase stability limit.

Atomic Structures of $$ [0\bar{1}10] $$ Symmetric Tilt Grain Boundaries in Hexagonal Close-Packed (hcp) Crystals

Abstract Molecular dynamics simulation and interface defect theory are used to determine the relaxed equilibrium atomic structures of symmetric tilt grain boundaries (STGBs) in hexagonal close-packed (hcp) crystals with a $$ [0\bar{1}10] $$ tilt axis. STGBs of all possible rotation angles θ from 0 deg to 90 deg are found to have an ordered atomic structure. They correspond either to a coherent, defect-free boundary or to a tilt wall containing an array of distinct and discrete intrinsic grain boundary dislocations (GBDs). The STGBs adopt one of six base structures, $$ P_{B}^{(i)} $$ , i = 1, …, 6, and the Burgers vector of the GBDs is related to the interplanar spacing of the base structure on which it lies. The base structures correspond to the basal plane (θ = 0 deg, $$ P_{B}^{(1)} $$ ); one of four minimum-energy, coherent boundaries, $$ (\bar{2}111),\;(\bar{2}112),\;(\bar{2}114) $$ , and $$ (\bar{2}116)\;\left( {P_{B}^{(2)} - P_{B}^{(5)} } \right) $$ ; and the $$ \left( {11\bar{2}0} \right) $$ plane (θ = 90 deg, $$ P_{B}^{(6)} $$ ). Based on these features, STGBs can be classified into one of six possible structural sets, wherein STGBs belonging to the same set i contain the same base boundary structure $$ P_{B}^{(i)} $$ and an array of GBDs with the same Burgers vector $$ b_{\text{GB}}^{(i)} $$ , which vary only in spacing and sign with θ. This classification is shown to apply to both Mg and Ti, two metals with different c/a ratios and employing different interatomic potentials in simulation. We use a simple model to forecast the misorientation range of each set for hcp crystals of general c/a ratio, the predictions of which are shown to agree well with the molecular dynamics (MD) simulations for Mg and Ti.

Solution of the Edges of Mode III Asymmetrical Dynamic Interface Crack Subjected to Variable Loads

By the approaches of the theory of complex functions, propagation problems concerning mode Ⅲ asymmetrical dynamic interface crack were studied. The problems can be transformed into Riemann-Hilbert problem easily by the measures of self-similar functions, and the universal expressions of analytical solutions of the edges of mode Ⅲ asymmetrical dynamics interface crack subjected to variable loads and respectively, were attained.

Interfacial structure of epitaxial SrTiO3 on Si: experiments and simulations

The interfacial structure of epitaxial SrTiO3 (STO) on Si has been investigated using combined experimental and theoretical approaches. Together with high resolution high angle annular dark field image, spatially resolved electron energy loss spectroscopy (EELS) acquired across the STO/Si interface reveals an interfacial region of 1–2 monolayer thickness, which is lacking in Sr, but contains Ti, Si and O. General agreement exists between the experimental EELS results and the simulated ones, which are obtained based on a classical molecular dynamics interface model, disclosing a gradual change in the local atomic coordination symmetry and possible defect incorporation at the interface.

A note on interface dynamics for convection in porous media

We studied the fluid interface problem through porous media given by two incompressible 2-D fluids of different densities. This problem is mathematically analogous to the dynamics interface for convection in porous media, where the free boundary evolves between fluids with different temperatures. We found a new formula for the evolution equation of the free boundary parameterized as a function in the periodic case. In this formula there is not a principal value in the non-local integral operator involved in the equation, giving a simpler system. Using this formulation, we perform numerical simulations in the stable case (denser fluid below) which shows a strong regularity effect in the periodic interface.

Enhanced-discretization space–time technique (EDSTT)

The enhanced-discretization space–time technique (EDSTT) was developed for the purpose of being able to, in the context of a space–time formulation, enhance the time-discretization in regions of the fluid domain requiring smaller time steps. Such requirements are often encountered in time-accurate computations of fluid–structure interactions, where the time-step size required by the structural dynamics part is smaller, and carrying out the entire computation with that time-step size would be too inefficient for the fluid dynamics part. In the EDSTT-single-mesh (EDSTT-SM) approach, a single space–time mesh, unstructured both in space and time, would be used to enhance the time-discretization in regions requiring smaller time steps. In the EDSTT-multi-mesh (EDSTT-MM) approach, we complement the space–time concept of the deforming-spatial-domain/stabilized space–time (DSD/SST) formulation with the multi-mesh concept of the enhanced-discretization interface-capturing technique (EDICT). In applications to fluid–structure interactions, the structural dynamics modeling is based on a single space–time mesh and the fluid dynamics modeling is based on two space–time meshes. The structural dynamics interface nodes in the space–time domain also belong to the second fluid mesh, which accommodates the time-step requirement of the structural dynamics. We apply the EDSTT-SM and EDSTT-MM approaches to a number of test problems to demonstrate how these methods work and why they would be desirable to use in time-accurate computations.