Multiscale Investigation Research Articles

Multi-scale investigation on curing time effect of lime stabilized red mudstone as fill material for high-speed railway subgrade

The utilisation of red mudstone waste as subgrade fill material after lime stabilization can meet the requirements of green development. This study aims at investigating the lime stabilization effect on the changes in mechanical properties and microstructure of compacted red mudstone fill material, with particular emphasis on the curing time effect. Red mudstone fill material were stabilized by 4 % lime, and the unconfined compressive strength, direct shear strength and microstructure of the lime-stabilized fill material specimens were determined at various curing times. Results show that the lime stabilization can significantly improve the unconfined compressive strength, modulus and direct shear strength and effectively mitigate the water sensitivity of the red mudstone fill material. The density function curve of the saturated red mudstone fill material shows monomodal characteristic, but the saturated lime stabilized fill material still maintains bimodal characteristic even with only one day of curing. The microstructure modification induced by lime stabilization mainly results from the rapid flocculation of soil particles and the formation of hydration product. During curing, the percentage of the nano-pores increases, mainly attributes to the formation of C-A-S-H which fills the micro-pores gradually.

Multi-scale investigation on staged deterioration mechanism of sliding-zone soils induced by reservoir fluctuations

Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by drying-wetting (D-W) cycles, which results in a significant decrease in mechanical properties. A comprehensive understanding of deterioration mechanism of sliding-zone soils is of great significance for interpreting the deformation behavior of landslides. However, quantitative investigation on the deterioration characteristics of soils considering the structural evolution under D-W cycles is still limited. Here, we carry out a series of laboratory tests to characterize the multi-scale deterioration of sliding-zone soils and reveal the mechanism of shear strength decay under D-W cycles. Firstly, we describe the micropores into five grades by scanning electron microscope and observe a critical change in porosity after the first three cycles. We categorize the mesoscale cracks into five classes using digital photography and observe a stepwise increase in crack area ratio. Secondly, we propose a shear strength decay model based on fractal theory which is verified by the results of consolidated undrained triaxial tests. Cohesion and friction angle of sliding-zone soils are found to show different decay patterns resulting from the staged evolution of structure. Then, structural deterioration processes including cementation destruction, pores expansion, aggregations decomposition, and clusters assembly are considered to occur to decay the shear strength differently. Finally, a three-stage deterioration mechanism associated with four structural deterioration processes is revealed, which helps to better interpret the intrinsic mechanism of shear strength decay. These findings provide the theoretical basis for the further accurate evaluation of reservoir landslides stability under water level fluctuations.

Structural and Magnetic Properties of Ferrofluids Composed of Self-Assembled Cobalt Ferrite Nanoflowers: A Multiscale Investigation

Structural and Magnetic Properties of Ferrofluids Composed of Self-Assembled Cobalt Ferrite Nanoflowers: A Multiscale Investigation

Multi-scale investigation of silane coupling agent for enhanced corrosion resistance in reinforced concrete

Reinforcement corrosion is a significant factor leading to the deterioration of building performance. In order to enhance the serviceability of reinforced concrete under corrosive environments, this study employs a silane coupling agent (γ-aminopropyltriethoxysilane) for steel reinforcement treatment. The anti-corrosion mechanism, crack propagation patterns, and modified corrosion resistance of the steel are investigated at multiple scales. Experimental techniques such as scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR) are utilized to explore the influence of the self-assembled coating of the silane coupling agent on the microscopic morphology, elements, and functional groups of the steel. Concrete specimens with treated reinforcement are fabricated, and electrochemical accelerated corrosion tests are conducted to compare corrosion differences among different specimens. Using untreated specimens as a control group, digital image correlation (DIC) technology is employed to capture the full-field strain and displacement distribution during the loading process. The crack propagation and slip behavior at the steel-concrete interface in the composite specimens are analyzed. The research findings indicate that, at the optimal concentration of 1.2 %, the self-assembled coating of the silane coupling agent successfully adheres to the steel surface, significantly enhancing the interfacial abrasion resistance and mechanical strength of the steel-concrete interface, thereby validating the improved corrosion resistance of the steel. This study proposes the self-assembly mechanism and interfacial enhancement mechanism of the silane coupling agent on steel at multiple scales, contributing to a comprehensive understanding of its effectiveness.

Conceptual design and experimental investigation of regolith bag structures for lunar in situ construction

Lunar habitat construction is a critical engineering requirement in lunar exploration missions, characterized by unique structural and material challenges distinct from Earth. To meet the demands of in situ large-scale construction in extreme lunar environments, a general mode of “Prefabricated core module & Inflatable structure &In situ materials structure” is adopted. This work analyzed the structural internal forces and foundation bearing capacity for lunar habitats, highlighting the significance of structural tensile performance and the foundation's allowable bearing capacity. A construction scheme based on regolith bags is proposed, encompassing architectural and structural design, and long-term planning. Multiscale experimental investigations conducted on “material, component, structure, and construction” levels confirm the excellent properties of regolith bag. Aramid fabric and CUG lunar regolith simulant were chosen for material and component testing, focusing on evaluating the regolith bag's performance under tension and compression. Successful construction demonstrations of a regolith bag arch structure and a regolith bag – airbag structural unit validate the feasibility of this construction scheme. Conclusively, the proposed lunar habitat construction scheme based on regolith bag technology provides a viable and efficient method for in situ lunar construction.

Molecular Regulator Driving Endometriosis Towards Endometrial Cancer: A Multi-Scale Computational Investigation to Repurpose Anti-Cancer drugs.

Endometriosis is a gynecological disorder among reproductive-aged women. Recent epidemiological investigations suggest endometriosis increases the risk of endometrial cancer. However, the molecular entity leading to endometriosis-to-endometrial cancer is largely unknown. This study aimed to combine a variety of computational approaches to identify the key therapeutic target promoting endometriosis-to-endometrial cancer and screen potential inhibitors against target to prevent cancer development. Our systematic investigations, includes transcriptomic profiling, protein network, pharmacophore modeling, docking, binding free energy calculation, dynamics simulation, and quantum mechanics. The gene expression analysis on endometriosis and endometrial cancer was performed and showed 108 shared upregulated genes in both conditions. Further construction of interaction network with 108 genes showed intercellular adhesion molecule 1 (ICAM1) to be a crucial molecule with a high degree of connectivity that influences vital mechanisms related to cancer pathways. We then generated ligand-based pharmacophore models using established ICAM1 inhibitors. Among the models, the ADRRR_8 pharmacophore exhibited a robust area under curve (AUC = 0.83), was employed to screen 1739 anti-cancer drugs. On screening, 421 anti-cancer drugs displayed ICAM1-inhibiting pharmacophore features. Further, the docking of 421 drugs with ICAM1 showed lanreotide (-7.80 kcal/mol) with better affinity than the reference ICAM1 inhibitor (-3.59 kcal/mol). Further validation though binding free energy and dynamics simulation of the lanreotide-ICAM1 complex showed a high binding affinity of -55.90 kcal/mol and contributed stable confirmation. According to quantum chemical calculations, lanreotide's electronic properties favour ICAM1 binding with highest occupied molecular orbital was -6.91 eV and lowest unoccupied molecular orbital was -3.93 eV. Our study supports using lanreotide to treat endometriosis, which could delay or prevent endometrial cancer. These predictions need to be confirmed and examined to determine the use of lanreotide in endometriosis treatment.

Investigation of corrosion inhibition and adsorption properties of quinoxaline derivatives on metal surfaces through DFT and Monte Carlo simulations

Abstract This work presents a multiscale theoretical investigation into the potential of quinoxaline derivatives (Q1–Q6) as corrosion inhibitors for various metals (Fe(110), Cu(111), and Al(110)). Employing a combined approach combining density functional theory (DFT) and Monte Carlo simulations, we explore the relationship between molecular structure, electronic properties, and adsorption behavior. Density functional theory (DFT) and molecular dynamics simulations (MDS) were used to investigate the electronic characteristics of diverse compounds. The study included key parameters including highest occupied molecular orbital energy (E HOMO), lowest unoccupied molecular orbital energy (E LUMO), energy gap (E g) between E LUMO and E HOMO, dipole moment, global hardness, softness (σ), ionization energy (I), electron affinity (A), electronegativity (χ), back-donation energy E b−d, global electrophilicity (ω), electron transfer, global nucleophilicity (ε), and total energy (sum of electronic and zero-point energies). These properties, alongside adsorption energies (following the trend Q6 > Q2 > Q3 > Q4 > Q5 > Q1), are used to identify promising inhibitor candidates and establish structure–property relationships governing their effectiveness. The results suggest that inhibitor efficiency increases with a decreasing energy gap between frontier orbitals. Notably, the protonated state of Q6 exhibits high reactivity, low stability, and strong adsorption, making it a potential candidate for further exploration. This comprehensive theoretical approach offers crucial insights for the conceptual development of new and powerful corrosion inhibitors.

Virological characteristics of the SARS-CoV-2 Omicron EG.5.1 variant.

In middle to late 2023, a sublineage of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron XBB, EG.5.1 (a progeny of XBB.1.9.2), is spreading rapidly around the world. We performed multiscale investigations, including phylogenetic analysis, epidemic dynamics modeling, infection experiments using pseudoviruses, clinical isolates, and recombinant viruses in cell cultures and experimental animals, and the use of human sera and antiviral compounds, to reveal the virological features of the newly emerging EG.5.1 variant. Our phylogenetic analysis and epidemic dynamics modeling suggested that two hallmark substitutions of EG.5.1, S:F456L and ORF9b:I5T are critical to its increased viral fitness. Experimental investigations on the growth kinetics, sensitivity to clinically available antivirals, fusogenicity, and pathogenicity of EG.5.1 suggested that the virological features of EG.5.1 are comparable to those of XBB.1.5. However, cryo-electron microscopy revealed structural differences between the spike proteins of EG.5.1 and XBB.1.5. We further assessed the impact of ORF9b:I5T on viral features, but it was almost negligible in our experimental setup. Our multiscale investigations provide knowledge for understanding the evolutionary traits of newly emerging pathogenic viruses, including EG.5.1, in the human population.

Multiscale investigation on the formation path of the apatite phase in bioactive glasses

Mesoporous bioactive glasses (MBGs) have been reported as promising biomaterials to stimulate and promote the growth of bones. When exposed to Simulated Body Fluid (SBF), MBGs develop an apatite phase called carbonate hydroxyapatite (H(C)A) on their surfaces that closely mimics the mineral phase of bones. In order to gain deeper insights into the key stages of the surface reactions of two different types of MBGs (58S and 70S30C) soaked in SBF, we have used high energy total X-ray scattering coupled to Pair Distribution Function (PDF) analysis, along with Raman spectroscopy and scanning electron microscopy. This type of coupled analytical approach can ultimately help to unravel the details of the reaction kinetics in the complex calcium phosphate environment around the BGs surfaces. The data obtained in our in-vitro study point to the formation of other intermediate phases like amorphous calcium phosphate (ACP) and calcite (CC), that transform after a specific time into H(C)A depending on the composition of the MBGs, their surface properties and their interaction times with SBF.

Effects of intergranular deformation incompatibility on stress state and fracture initiation at grain boundary: Experiments and crystal plasticity simulations

The heterogeneous deformation of polycrystalline metals inherently originates from the intergranular deformation incompatibility. This paper proposes physical parameters related to the crystal orientations, the Schmid factor of the most activated slip system, and the misorientation angle to characterize the deformation incompatibility between the adjacent grain couple. A comprehensive multiscale investigation is conducted to reveal the mechanism from intergranular deformation incompatibility to fracture initiation at grain boundaries. At the specimen scale, experimental and numerical uniaxial tensile tests are performed on smooth and pre-notched dog-bone specimens to achieve different loading paths on the materials. The heterogeneous fields of stress triaxiality explains the heterogeneous size of the dimples observed in fractography. At the grain scale, electron backscatter diffraction analysis is conducted to characterize the microstructural properties around the nucleated voids within the materials. Voids are captured at the grain boundaries with directions parallel to the loading direction and intergranular deformation incompatibility is characterized using the proposed parameters. Simulations on the plastic deformation of realistic microstructures are performed to clarify the phenomenon. The results reveal that the fluctuation in stress triaxiality at grain boundaries is ascribed to intergranular deformation incompatibility, leading to fracture initiation at these sites. The relationships between the proposed physical parameters of intergranular deformation incompatibility and fluctuation in stress triaxiality are summarized in all circumstances. Finally, the ductile damage at the grain scale is predicted by the Rice–Tracey model, and the results show that the effects of microstructures on heterogeneous plastic deformation and stress state can be well considered.

Phollow: Visualizing Gut Bacteriophage Transmission within Microbial Communities and Living Animals.

Bacterial viruses (known as "phages") shape the ecology and evolution of microbial communities, making them promising targets for microbiome engineering. However, knowledge of phage biology is constrained because it remains difficult to study phage transmission dynamics within multi-member communities and living animal hosts. We therefore created "Phollow": a live imaging-based approach for tracking phage replication and spread in situ with single-virion resolution. Combining Phollow with optically transparent zebrafish enabled us to directly visualize phage outbreaks within the vertebrate gut. We observed that virions can be rapidly taken up by intestinal tissues, including by enteroendocrine cells, and quickly disseminate to extraintestinal sites, including the liver and brain. Moreover, antibiotics trigger waves of interbacterial transmission leading to sudden shifts in spatial organization and composition of defined gut communities. Phollow ultimately empowers multiscale investigations connecting phage transmission to transkingdom interactions that have the potential to open new avenues for viral-based microbiome therapies.

Multiscale Investigation of Switchable Metallicity in Tunable Conductance Devices

The project “Multiscale Investigation Of Switchable Metallicity In Tunable Conductance Devices” en- compasses a comprehensive web application designed to revolutionize the way businesses handle MnS2 components, such as pressure switches, variable resistors, memory devices, batteries, and supercapacitors, through a series of interconnected modules. At its core, this application streamlines client interactions, optimizes MnS2 material processing, and ensures seamless application integration, all while leveraging advanced porosity analysis techniques. A significant enhancement in the Porosity Analysis module is the incorporation of the Decision Tree Regressor, a machine learning algorithm, to accurately evaluate the conductivity of materials. This addition not only boosts the precision of porosity and conductivity assessments but also empowers the system to predict material performance with higher accuracy, thereby enabling more tailored solutions for client requirements.

Role of polyferric sulphate in hydration regulation of phosphogypsum-based excess-sulphate slag cement: A multiscale investigation

Current demand for waste recycling, phosphogypsum-based excess-sulphate slag cement (PESSC) as a sustainable cement prepared by solid wastes, urges enhancing its performance development based on microstructure optimisation. For the purpose of improving the performance and durability of PESSC used in normal or corrosive environments, it is deemed an efficient technique to produce iron-doped compounds with high thermodynamic stability. This paper presents a systematic study of the effect of iron modification on PESSC binders by introducing 0%–2% polyferric sulphate (PFS) from a multiscale viewpoint. XPS, 29Si and 27Al NMR, and TEM were used to characterise the nanostructure of solid particles firstly at Level I. Then, the chemical composition and phase assemblage of PESSC binders were revealed at Level II in terms of ICC, ICP, DTG-DSC, FTIR, BSE-EDS and XRD. Finally, setting time and strength development were determined at Level III. Results indicated that the soluble FeOH4− supplied by the hydrolysis of PFS promotes the generation of iron-doped ettringite with a greater length-to-diameter ratio and thermodynamic stability. Seeding effect of iron doping also promotes the production of spherical and retiform gels with a slight influence on the chemical components and polymerisation. Despite the fact that iron doping weakens the early strength of PESSC mortars, it promotes the persistent hydration rate by retarding precipitation and encapsulation of hydrates on the surface of the slag, showing excellent strength in the later stages. In view of microstructure evolution and performance development during each stage, PFS supplementation within 1.0% is considered a feasible modification of PESSC relying on the formation control of iron-doped hydrates.

Enhanced Hoek-Brown (H-B) criterion for rocks exposed to chemical corrosion

Underground constructions often encounter water environments, where water–rock interaction can increase porosity, thereby weakening engineering rocks. Correspondingly, the failure criterion for chemically corroded rocks becomes essential in the stability analysis and design of such structures. This study enhances the applicability of the Hoek-Brown (H-B) criterion for engineering structures operating in chemically corrosive conditions by introducing a kinetic porosity-dependent instantaneous mi (KPIM). A multiscale experimental investigation, including nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), pH and ion chromatography analysis, and triaxial compression tests, is employed to quantify pore structural changes and their linkage with the strength responses of limestone under coupled chemical-mechanical (C-M) conditions. By employing ion chromatography and NMR analysis, along with incorporating the principles of free-face dissolution theory accounting for both congruent and incongruent dissolution, a kinetic chemical corrosion model is developed. This model aims to calculate the kinetic porosity alterations within rocks exposed to varying H+ concentrations and durations. Subsequently, utilizing the generalized mixture rule (GMR), the kinetic porosity-dependent mi is formulated. Evaluation of the KPIM-enhanced H-B criterion using compression test data from 5 types of rocks demonstrated a high level of consistency between the criterion and the experimental results, with a coefficient of determination greater than 0.96, a mean absolute percentage error less than 4.84%, and a root-mean-square deviation less than 5.95 MPa. Finally, the physical significance of the porosity-dependent instantaneous mi is clarified: it serves as an indicator of a rock’s capacity to leverage the confining pressure effect.

Peculiar Features of Lime-Treated Pyroclastic Soils through a Multi-Scale Experimental Investigation

Peculiar Features of Lime-Treated Pyroclastic Soils through a Multi-Scale Experimental Investigation

Microwave absorption and electromagnetic properties of ultra-high-strength cementitious materials: Influence of basalt powder and underlying mechanism

The utilization of basalt powder in ultra-high-strength cementitious materials (UHSCMs) holds significant potential for application in mitigating CO2 emissions and reducing electromagnetic pollution. This study investigated the microwave absorption and electromagnetic properties of UHSCMs incorporating basalt powder, with the silica-fume-based mix as a comparison. A comprehensive multi-scale investigation was conducted to gain an in-depth understanding of the electromagnetic properties of UHSCMs. From the results, the UHSCM with basalt powder was demonstrated to possess improved microwave absorption performance, characterized by a mean reflection loss of −8.22 dB and effective bandwidths of 58.3% (<-7.0 dB) and 26.6% (<-10.0 dB). The enhanced performance of this mixture was attributed to its superior impedance-matching capability and microwave attenuation ability. The dielectric loss peaks within frequency ranges of 7.0–8.5 GHz and 10.0–11.5 GHz were caused by the interfacial polarization of macro pores and gel pores, respectively. The natural resonance, exchange resonance, and eddy current effect were the primary mechanisms of the magnetic loss. CaFeSi2O6 particles from basalt powder contributed to the enhanced natural resonance. In addition, basalt powder had the better market potentials and lower environmental impact as a supplementary cementitious material than silica fume for enhancing microwave absorption of UHSCMs. The finding of this study demonstrated the suitability of adopting basalt powder in UHSCM production with improved greenness and electromagnetic properties.

A JVLA, LOFAR, e-Merlin, VLBA, and EVN study of RBS 797: can binary supermassive black holes explain the outburst history of the central radio galaxy?

The multifaceted central radio galaxy of the cluster RBS 797 shows several episodes of jet activity in multiple directions. We wish to understand the causes behind these dramatic misalignments and measure the timescales of the successive outbursts. We present a multifrequency (144 MHz -- 9 GHz) and multiscale (5 pc -- $50$ kpc) investigation of the central radio galaxy in RBS 797, by means of JVLA, LOFAR (with international stations), e-Merlin, VLBA, and EVN data. We investigate the morphological and spectral properties of the radio lobes, the jets, and the active core. We confirm the co-spatiality of the radio lobes with the four perpendicular X-ray cavities previously discovered. The radiative ages of the east-west lobes ($31.4 Myr) and of the north-south lobes ($32.1 Myr) support a coeval origin of the perpendicular outbursts, which also have similar active phase duration (sim 12 Myr). Based on the analysis of the inner north-south jets (on scales of $ kpc), we (a) confirm the S-shaped jet morphology; (b) show the presence of two hotspots per jet with a similar spectral index; and (c) estimate the age of the twisting north-south jets to be less than $ Myr. Based on these results, we determine that jet precession, with a period sim 9 Myr, half-opening angle sim circ $, and jet advance speed sim 0.01$c$, can explain the properties of the north-south jets. We also find that the synchrotron injection index has steepened from the large, older outbursts ($ to the younger S-shaped jets ($ possibly due to a transition from FR I-like to FR II-like activity. The e-Merlin, VLBA, and EVN data reveal a single, compact core at the heart of RBS 797, surrounded by extended radio emission whose orientation depends on the spatial scale sampled by the data. We explore several engine-based scenarios to explain these results. Piecing together the available evidence, we argue that RBS 797 likely hosts (or hosted) binary active supermassive black holes (SMBHs). The detection of a single component in the VLBA and EVN data is still consistent with this interpretation, since the predicted separation of the binary SMBHs (leq 0.6 pc) is an order of magnitude smaller than the resolution of the available radio data (5 pc).

Synergistic effects of recycled demolition waste and GGBS-FA based geopolymers on the mechanical properties and stabilization mechanism of high plasticity clay

Recycled demolition waste (RDW) and ground granulated blast furnace slag-fly ash-based geopolymer (GFG) are promising materials for treating high-plasticity clay (CH) in highway subgrades. However, the underlying synergistic stabilization mechanisms remain unclear. To elucidate the fundamental mechanisms governing post-treatment soil stabilization, a multi-scale laboratory investigation was undertaken. This investigation encompassed the evaluation of mechanical properties (compaction, California bearing ratio (CBR), and unconfined compressive strength (UCS)) to quantify the enhanced performance of the treated soil. Additionally, microstructural and mineralogical characterization was performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and atomic force microscopy (AFM) to elucidate the microscopic mechanisms responsible for this improvement. The results indicated that the addition of RDW led to a reduction in the optimum moisture content (OMC) while increasing the maximum dry density (MDD) of CH. Moreover, upon incorporating RDW-GFG, the mechanical properties of the cured soil exhibited significant improvement. Specifically, the addition of 25% RDW to CH resulted in a 184% increase in CBR and effective improvement in water stability (immersion swelling percentage is reduced). Furthermore, when 25% RDW and 15% GFG were added to CH, the UCS has increased significantly by 8 times. The addition of RDW effectively enhanced the particle size distribution, compacted the soil, thus increased the shear strength. The results from XRD and SEM analyses revealed that the inclusion of GFG could generate geopolymer cementitious bonding network in the soil matrix. These materials facilitated bonding between CH particles and RDW, filling the pores and densifying the overall structure, thus increasing its strength. The synergy of RDW-GFG substantially improved the highly plastic soil through physicochemical actions, markedly elevating both its strength and water stability. Consequently, the outcomes of this experimental study offer valuable insights for road engineering applications.

Multi-scale boiling heat transfer investigation on micro-thin aluminum heaters

Nucleate boiling is a highly efficient heat transfer mode distinguished by the liquid-vapor phase change, which occurs through the formation, growth, and detachment of vapor bubbles from a heated surface. Its crucial role in various industrial applications, such as nuclear power plant operation and effective heat management in small electronic devices, has driven significant research efforts. However, despite extensive research dedicated to boiling investigations, there are still substantial knowledge gaps that hinder our ability to accurately predict heat removal rates. These knowledge gaps arise from the complex nature of small-scale boiling phenomena, which are further complicated by their strong dependence on operating conditions and the interactions between walls and fluids. In an effort to address some of these gaps, we conducted multi-scale investigations during pool boiling of de-ionized water on micro-thin aluminum heaters. We captured bubble dynamics through multiple synchronized diagnostic sources, including high-speed backlit imaging to track bubble growth, synchronized high-speed infrared thermometry to capture the corresponding thermal footprint on the boiling surface, and in-house developed fast-response micro-thermocouples to measure temperature at multiple locations within the fluid. Our study reveals peculiar aspects of heat transfer mechanisms occurring at single bubble level (low heat fluxes) and in fully developed nucleate boiling regimes (high heat fluxes).

Multi-scale investigation of heat and momentum transfer in packed-bed TES systems up to 800 K

With the rising cost of energy and the advancement of corporate social responsibility, there is a growing interest in addressing the challenge of recovering and storing high-temperature waste heat. Sensible heat storage in packed beds stands out as a cost-effective and seemingly straightforward solution for high-temperature Thermal Energy Storage (TES). Engineering models developed to design low-temperature TES systems were tentatively used to design this new generation of high-temperature systems. Delving into the physics of coupled heat and mass transfer reveals a lack of validation of this approach. This study seeks to establish a comprehensive bottom-up methodology - from the particle scale up to the system level - to provide informed and validated engineering models for the design of high-temperature TES systems. To achieve this goal, we developed a multi-scale numerical model to explore the physics of heat and momentum transfer in packed-bed TES systems. At the microscopic scale (pore/particle), we consider the flow of a compressible high-temperature gas between the particles, coupled to transient heat conduction within the particles, with particular attention given to incorporating accurate temperature-dependent viscosity for the gas phase and thermal conductivity and density for both solid and gas phases. At the macroscopic scale (engineering), we propose a high-temperature extension of state-of-the-art two-equation TES models. The governing equations considered are the volume-average conservation laws for gas-mass, gas-momentum and energy of both phases. The multi-scale strategy is applied to a randomly packed bed of spherical particles generated with the discrete element method (DEM) software LIGGGHTS. Numerical models for both scales were implemented in the Porous material Analysis Toolbox based on OpenFoam (PATO), which is made available in Open Source by NASA. Microscopic scale simulations were used to infer the effective parameters needed to inform the macroscopic model, namely, permeability, Forchheimer coefficient, effective thermal conductivities, and the heat transfer coefficient. The informed macroscopic model reproduces with excellent accuracy the average temperature fields of the physics-based microscopic model. Pore-scale analysis shows highly three-dimensional flow characterized by reverse flow and strong cross-flow in the packed bed system. Moreover, it indicates the coupling between temperature and velocity fields, where a nonuniform velocity field results in uneven temperature distributions across the fluid and the solid spheres within the packed bed, subsequently affecting the macroscopic heat transfer coefficient. The overall strategy is validated by comparison to available experimental data. This bottom-up methodology contributes to the understanding and opens new perspectives for a more precise design and monitoring of high-temperature TES systems.