Dense State Research Articles

Novel vibratory compaction quality indices developed from particle migration and distribution characteristics for unbound aggregate materials

Unbound aggregate materials (UAM) with large air voids are increasingly used to construct pavement base and subbase layers as part of the initiative to create sponge cities and improve drainage performance. However, the motion of particles and the spatial distribution of kinetic energy during the particle rearrangement process induced by vibratory loading remain unclear. This study presents the results of laboratory vibratory plate compaction tests conducted on UAM specimens under various combinations of vibratory parameters and different levels of Gravel to Sand ratio (G/S). SmartRock (SR) sensors were placed within the specimens to monitor particle motion in real-time while kinematic energy and its spatial distribution were analyzed from the acceleration time-history signals collected by the SR sensors. Based on high-precision industrial X-ray computed tomography (XCT) and 3D reconstruction technology, this study analyzed the motion and migration rules of the UAM particles. A new compaction index was proposed based on particle motion and kinematic energy to evaluate the compaction quality of the specimens.The findings of this study reveal that vibratory compaction can be divided into two distinct stages. During the first stage, coarse particles primarily move vertically while energy dissipation occurs mainly through compression of air voids but does not form a dense skeleton structure. In the second stage, coarse particles translate horizontally while rotating vertically, resulting in a tendency of the particles to lie flat with their long axes oriented horizontally. During this stage, most of the energy is used to fill air voids, leading to the formation of a densely packed skeleton structure. Kinematic energy indices and particle movement in the middle of the specimen can be used to evaluate the compaction stage and quality. Additionally, the lateral particle motion in the specimen transitions from continuous ascent to gradual descent to almost no kinematic energy, indicating a relatively dense state of compaction. Reducing the void ratio and increasing the contact area between particles in these size ranges of 4.75-9.5mm and 2.36-4.75mm can significantly increase the compaction density and improve the stability and deformation resistance of the subgrade bed.The results of this study provide valuable insights into the mechanisms of vibratory compaction and can be used to optimize compaction methods and improve pavement performance.

Geotechnical response of Strip footing resting on oil-contaminated sand improved with stone columns: numerical study

Ground improvement techniques are frequently employed in construction sites characterized by weak soil conditions that may result in suboptimal performance. The use of ordinary and encased stone columns aims to enhance endurance, shear strength, and soil hardness, thereby mitigating settlement issues and expediting the consolidation of contaminated sand soils. In this research, a comprehensive investigation involving 74 cases was conducted to assess the behavior of both ordinary stone columns and encased stone columns under strip footing in contaminated sand subgrade. The objective was to discern the impact and characteristics of encapsulation in comparison to encapsulated stone columns, employing a Finite Element Model (FEM) within the PLAXIS 3D software package. The study focused on stone columns with two different diameters (D = 0.5 m and 0.6 m), while the column length was 12 m across all cases. As the contamination level increases—at the variable contaminated sand levels of (2%, 5%, and 10%)—the viscosity of the soil rises, leading to a reduction in cohesion between soil granules. Consequently, the internal friction angle decreases, with values diminishing from 31° to 27° and then to 24°, respectively. The clean sand was placed to achieve relative density, a medium dense sand state (Dr = 50%). The two categories of stone columns examined were ordinary stone columns (OSC) without encapsulation and encased stone columns (ESC) encapsulated with varying degrees of hardening. Results obtained at variable internal friction angles (35, 40, and 45 degrees) revealed a notable increase in the endurance of ordinary stone columns on untreated soil conditions, reaching 100%, 125%, and 148% for column diameters (D = 0.5 m) and 130%, 145%, and 180% for column diameters (D = 0.6 m), respectively. The corresponding increase in the endurance of encased stone columns under untreated soil conditions was found to be 275%, 33%, and 345% for column diameters (D = 0.5 m) and reached 313%, 350%, and 375% for column diameters (D = 0.6 m), respectively. All preceding results were obtained under the condition of a contaminated sand content of 5%. The investigation aimed to provide valuable insights into the performance and efficacy of ordinary stone columns (OSC) and encased stone columns (ESC) as a geotechnical solution for improving soil conditions in construction projects.

Behaviour of sand under the constant shear drained stress path: the role of fines

This paper presents a specifically designed experimental study aimed at exploring the role of fines in altering the behaviour of sand under a constant shear drained (CSD) stress path. The novelty of this study includes that the interplay of several key factors (fines shape, fines content, void ratio) was investigated systematically and the true constant shear stress condition was fulfilled by means of an advanced servo system, which allowed the entire loading response to be captured. One of the marked findings is that the presence of fines not only alters the onset of instability of loose sand but also affects the deformation development thereafter. Drained instability can be triggered more easily in loose sand mixed with silica fines compared with the sand on its own. At the same quantity of fines, instability can be triggered more easily for sand mixed with rounded fines. However, the effect of fines appears to be marginal for sand at a dense state. For all tested specimens, values of the axial strain rate at instability fall in a narrow range (0·008–0·016%/min), meaning that the axial strain rate can potentially be a useful guide for quantitatively determining the inception of instability under CSD conditions. The stress ratio q/p′ at onset of instability under the CSD conditions is also state dependent, as under the undrained conditions.

The effect of working fluid and compressibility on the optimal solidity of axial turbine cascades

The blade solidity, namely the blade chord-to-pitch ratio, largely affects the fluid-dynamic performance of turbomachinery and its cost. For turbo-machines operating with air or steam, the optimal value of the solidity which maximizes the efficiency is estimated with empirical correlations such as the ones proposed by <xref ref-type="bibr" rid="fn19">Zweifel (1945)</xref> and <xref ref-type="bibr" rid="fn17">Traupel (1966)</xref>. However, if the turbomachine operates with unconventional fluids, the accuracy of these correlations is questionable. Examples of such fluids are the organic compounds (e.g., hydrocarbons, siloxanes) used in organic Rankine cycle (ORC) power systems. This study concerns an investigation on how the working fluid, its thermodynamic state, and flow compressibility influence the optimum pitch-to-chord ratio of turbine stages. A first principle reduced-order model (ROM) for the computation of profile losses was developed for this purpose. The ROM results are compared with those obtained from numerical simulations of the flow over two axial turbine cascade geometries. The influence of both the working fluid, the flow compressibility, and the solidity value on both the boundary layer state at the blade trailing edge and the base pressure are evaluated. Models to compute mixing and passage losses in the compressible regime as a function of the axial solidity are proposed and discussed. Results show that the value of the optimal solidity of turbine cascades significantly increases with the flow compressibility, and mildly increases if the fluid is in the dense vapor state. Moreover, the optimal solidity value is strongly affected by the mixing process occurring downstream of the blade trailing edge. Therefore, currently available models for its estimation, which are solely based on the minimization of the profile losses, are inaccurate.

Structural Evolution of Basaltic Melts in the Deep Earth: Insights From High‐Pressure Sound Velocity of Glass

AbstractThe densification mechanisms of silicate melts under high pressure are of key interest in understanding the evolution of the early Earth and its present‐day internal structure. Here, we report Brillouin spectroscopy‐derived transverse acoustic wave velocities from a basaltic glass at high pressures up to 163 GPa and ambient temperature to provide insight into pressure‐induced changes in its elasticity and, by extension, its density. We find that the pressure dependence of below 110–140 GPa follows a trend nearly tantamount to those of pyrolite and Fe‐ and (Fe,Al)‐bearing MgSiO3 glasses, indicating that the large compositional differences among these glasses do not exert variable acoustic wave velocity trends. However, at higher pressures we observe a small departure from the profiles of the Al‐poor compositions toward higher acoustic wave velocities to eventually become stiffer. This pressure‐induced steepening in is comparable to that of (Mg, Fe, Al)(Si, Al)O3 glass, and suggests a possible structural change toward a denser state caused by more rapidly changing Al–O coordination in network‐forming Al. Coupled with the high Fe content in basalt, this may render basaltic melt denser than surrounding minerals in the deep lower mantle, and may provide an additional mechanism for the existence of ultralow‐velocity zones.

Heterochromatin protein 1 alpha (HP1α) undergoes a monomer to dimer transition that opens and compacts live cell genome architecture.

Our understanding of heterochromatin nanostructure and its capacity to mediate gene silencing in a living cell has been prevented by the diffraction limit of optical microscopy. Thus, here to overcome this technical hurdle, and directly measure the nucleosome arrangement that underpins this dense chromatin state, we coupled fluorescence lifetime imaging microscopy (FLIM) of Förster resonance energy transfer (FRET) between histones core to the nucleosome, with molecular editing of heterochromatin protein 1 alpha (HP1α). Intriguingly, this super-resolved readout of nanoscale chromatin structure, alongside fluorescence fluctuation spectroscopy (FFS) and FLIM-FRET analysis of HP1α protein-protein interaction, revealed nucleosome arrangement to be differentially regulated by HP1α oligomeric state. Specifically, we found HP1α monomers to impart a previously undescribed global nucleosome spacing throughout genome architecture that is mediated by trimethylation on lysine 9 of histone H3 (H3K9me3) and locally reduced upon HP1α dimerisation. Collectively, these results demonstrate HP1α to impart a dual action on chromatin that increases the dynamic range of nucleosome proximity. We anticipate that this finding will have important implications for our understanding of how live cell heterochromatin structure regulates genome function.

Adaptive No‐Tip Distribution of Rich Charge‐Density‐Clusters Guiding Confinement Deposition with Repair Function toward Highly Reversible Zinc Anode

AbstractThe plating/stripping behavior of Zn ions on the Zn anode, driven by an electric field, is a key process in determining the performance of aqueous zinc ion batteries (AZIBs). Process‐induced unevenness of commercial Zn foils results in poor reversibility of Zn anodes. Herein, a self‐healing dynamic anode/electrolyte interface is constructed by incorporating hydroxyl‐rich alcohols with high charge density and zincophilicity into the original electrolyte. These alcohols selectively anchor on electron‐poor sites in the charging state, inducing domain‐limited deposition of Zn2+ to achieve a dense, uniform, and flat deposition state. As a result, a durable Zn anode with excellent electrochemical reversibility can be realized in practical cycling (average Coulombic efficiency of 99.5%). Even under deep plating/stripping conditions (5 mA cm−2 and 5mAh cm−2), the modified electrolyte exhibits a remarkable repair effect on corroded Zn anodes that have been cycled in base electrolyte, extending the lifespan to over 1,020 h. This represents a 15.6‐fold enhancement in lifespan compared to recycling in the base electrolyte. This strategy for electrolyte additive directly influences the design of ultra‐long‐life AZIBs and provides concrete concepts for the recovery of zinc anodes.

Strength and fabric anisotropy of granular materials under true triaxial configurations using DEM

This paper investigates the strength and fabric anisotropy of granular materials under true triaxial configurations using the discrete element method. A clump logic based on the multi-sphere approach was utilized to replicate realistic particle shapes. The evolutions of deviatoric stress and volumetric strains were found to be independent of mean effective stress, and intermediate principal stress parameter (b). From a macroscopic viewpoint, all samples exhibited initial strain hardening followed by softening behaviour, stabilizing at large deviatoric strains due to the dense state of assemblies. The peak state friction angles showed dependency on the b-value, aligning closely with experimental findings. Microscopic parameters such as mechanical coordination number and sliding fraction were found to be approximately independent of b-values. Additionally, non-coaxiality was observed for various b-values except for specific shear modes, aligning with previous findings using spherical particles. These results highlight the capability of clumped particles to simulate the true mechanical behaviour of granular materials and contribute to our understanding of their complex response under different loading conditions.

Angle-Resolved Linear Dichroism to Probe the Organization of Highly Ordered Collagen Biomaterials.

Controlling the assembly of high-order structures is central to soft-matter and biomaterial engineering. Angle-resolved linear dichroism can probe the ordering of chiral collagen molecules in the dense state. Collagen triple helices were aligned by solvent evaporation. Their ordering gives a strong linear dichroism (LD) that changes sign and intensity with varying sample orientations with respect to the beam linear polarization. Being complementary to circular dichroism, which probes the structure of chiral (bio)molecules, LD can shift from the molecular to the supramolecular scale and from the investigation of the conformation to interactions. Supported by multiphoton microscopy and X-ray scattering, we show that LD provides a straightforward route to probe collagen alignment, determine the packing density, and monitor denaturation. This approach could be adapted to any assembly of chiral (bio)macromolecules, with key advantages in detecting large-scale assemblies with high specificity to aligned and chiral molecules and improved sensitivity compared to conventional techniques.

Ultrafine Asymmetric Soft/Stiff Nanohybrids with Tunable Patchiness via a Dynamic Surface-Mediated Assembly.

Asymmetric soft-stiff patch nanohybrids with small size, spatially separated organics and inorganics, controllable configuration, and appealing functionality are important in applications, while the synthesis remains a great challenge. Herein, based on polymeric single micelles (the smallest assembly subunit of mesoporous materials), we report a dynamic surface-mediated anisotropic assembly approach to fabricate a new type of small asymmetric organic/inorganic patch nanohybrid for the first time. The size of this asymmetric organic/inorganic nanohybrid is ∼20 nm, which contains dual distinct subunits of a soft organic PS-PVP-PEO single micelle nanosphere (12 nm in size and 632 MPa in Young' modulus) and stiff inorganic SiO2 nanobulge (∼8 nm, 2275 MPa). Moreover, the number of SiO2 nanobulges anchored on each micelle can be quantitatively controlled (from 1 to 6) by dynamically tuning the density (fluffy or dense state) of the surface cap organic groups. This small asymmetric patch nanohybrid also exhibits a dramatically enhanced uptake level of which the total amount of intracellular endocytosis is about three times higher than that of the conventional nanohybrids.

Helical close-packing of anisotropic tubes

Helically close-packed states of filaments are common in natural and engineered material systems, ranging from nanoscopic biomolecules to macroscopic structural components. While the simplest models of helical close-packing, described by the ideal rope model, neglect anisotropy perpendicular to the backbone, physical filaments are often quite far from circular in their cross-section. Here, we consider an anisotropic generalization of the ideal rope model and show that cross-section anisotropy has a strongly non-linear impact on the helical close-packing configurations of helical filaments. We show that the topology and composition of the close-packing landscape depends on the cross-sectional aspect ratio and is characterized by several distinct states of self-contact. We characterize the local density of these distinct states based on the notion of confinement within a ‘virtual’ cylindrical capillary, and show that states of optimal density vary strongly with the degree of anisotropy. While isotropic filaments are densest in a straight configuration, any measure of anisotropy leads to helicity of the maximal density state. We show the maximally dense states exhibit a sequence of transitions in helical geometry and cross-sectional tilt with increasing anisotropy, from spiral tape to spiral screw packings. Furthermore, we show that maximal capillary density saturates in a lower bound for volume fraction of π/4 in the large-anisotropy, spiral-screw limit. While cross-sectional anisotropy is well-known to impact the mechanical properties of filaments, our study shows its strong effects to shape the configuration space and packing efficiency of this elementary material motif.

A formulation for asphalt concrete air void during service life by adopting a hybrid evolutionary polynomial regression and multi-gene genetic programming

Bitumen, aggregate, and air void (VA) are the three primary ingredients of asphalt concrete. VA changes over time as a function of four factors: traffic loads and repetitions, environmental regimes, compaction, and asphalt mix composition. Due to the high as-constructed VA content of the material, it is expected that VA will reduce over time, causing rutting during initial traffic periods. Eventually, the material will undergo shear flow when it reaches its densest state with optimum aggregate interlock or refusal VA content. Therefore, to ensure the quality of construction, VA in asphalt mixture need to be modeled throughout the service life. This study aims to implement a hybrid evolutionary polynomial regression (EPR) combined with a teaching–learning based optimization (TLBO) algorithm and multi-gene genetic programming (MGGP) to predict the VA percentage of asphalt mixture during the service life. For this purpose, 324 data records of VA were collected from the literature. The variables selected as inputs were original as-constructed VA, VAorig\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${VA}_{orig}$$\\end{document} (%); mean annual air temperature, MAAT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$MAAT$$\\end{document} (°F); original viscosity at 77 °F, ηorig,77\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\eta }_{orig,77}$$\\end{document} (Mega-Poises); and time\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$time$$\\end{document} (months). EPR-TLBO was found to be superior to MGGP and existing empirical models due to the interquartile ranges of absolute error boxes equal to 0.67%. EPR-TLBO had an R2 value of more than 0.90 in both the training and testing phases, and only less than 20% of the records were predicted utilizing this model with more than 20% deviation from the observed values. As determined by the sensitivity analysis, ηorig,77\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\eta }_{orig,77}$$\\end{document} is the most significant of the four input variables, while time is the least one. A parametric study showed that regardless of MAAT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$MAAT$$\\end{document}, ηorig,77,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\eta }_{orig,77},$$\\end{document} of 0.3 Mega-Poises, and VAorig\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${VA}_{orig}$$\\end{document} above 6% can be ideal for improving the pavement service life. It was also witnessed that with an increase of MAAT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$MAAT$$\\end{document} from 37 to 75 °F, the serviceability of asphalt concrete takes 15 months less on average.

Emerging Mesoscale Flows and Chaotic Advection in Dense Active Matter

We study two models of overdamped self-propelled disks in two dimensions, with and without aligning interactions. Both models support active mesoscale flows, leading to chaotic advection and transport over large length scales in their homogeneous dense fluid states, away from dynamical arrest. They form streams and vortices reminiscent of multiscale flow patterns in turbulence. We show that the characteristics of these flows do not depend on the specific details of the active fluids, and result from the competition between crowding effects and persistent propulsions. This observation suggests that dense active suspensions of self-propelled particles present a type of “active turbulence” distinct from collective flows reported in other types of active systems. Published by the American Physical Society 2024

How do productivity gradient and diffusion shape patterns in a plant–herbivore grazing system?

Natural systems show heterogeneous patchy distributions of vegetation over large landscapes. Reaction–diffusion systems can demonstrate such heterogeneity of species distributions. Here, we analyse a reaction–diffusion model of plant–herbivore interactions in two-dimensional space to illustrate non-homogeneous distributions of plants and herbivores. The non-spatial system shows bottom-up control, where herbivore density is low under low and high primary productivity but increased at intermediate productivity. In addition, the non-spatial system provides bistability between a dense vegetation state devoid of herbivores and a coexisting state of plants and herbivores. In the spatiotemporal model, we give analytical conditions of occurring diffusion-driven (Turing) instability, where a novel point in our model is the relative dispersal of herbivores, which represents the movement of herbivores from a higher to a lower vegetation state in addition to the self-diffusion of both species. It is shown that heterogeneity in the population distribution does not occur if the relative dispersal of herbivores is low, but it appears in the opposite case. Due to bistability in the underlying non-spatial system, the spatiotemporal model produces initial value-dependent patterns. The two initial values make different patterns despite having the same primary productivity and relative dispersal rate. As productivity increases with a given relative herbivore dispersal, pattern transition occurs from a blend of stripes and spots of low vegetation state to a predominantly low-density vegetation state with smaller patches of densely vegetated states with one initial value. On the contrary, a discernible change in vegetation patterns from cold spots in the dense vegetation to hot stripes in the primarily low-vegetated state is noticed under the other initial population value. Furthermore, the population distributions of plants and herbivores in the entire domain after a long period are heterogeneous for both initial values, provided the relative herbivore dispersal is substantial. We estimated mean population densities to observe species fitness in the whole domain under variable productivity. When productivity is high, the mean population density of plants may go up or down, depending on the herbivore’s relative dispersal rate. In contrast to the bottom-up control dynamics of the non-spatial system, the system exhibits a top-down control under high relative dispersal, where the herbivore regulates vegetation growth under high productivity. On the other hand, herbivores are extinct under high productivity if the relative dispersal is low.

Deciphering yield modification of hadron-triggered semi-inclusive recoil jets in heavy-ion collisions

In relativistic heavy-ion collisions, a hot and dense state of matter, called the Quark-Gluon Plasma (QGP), is produced. Semi-inclusive jets recoiling from trigger hadrons of high transverse momenta (pT) can serve as an effective probe of the QGP properties, as they are expected to experience jet quenching when traversing the QGP. Recent experimental results on the ratio of recoil jet yields normalized by the trigger counts in heavy-ion collisions to that in p+p collisions (IAA) pose an unexpected challenge in its interpretation. It is observed that IAA rises with the jet pT and possibly exceeds unity at high pT, while traditionally it is expected that jet quenching would lead to IAA<1. To address this challenge, we utilize the Linear Boltzmann Transport (LBT) model to simulate jet transport in the QGP, and study the effect of jet quenching for high-pT triggers and recoil jets separately on IAA. We find that the quenching of the colored triggers alone is responsible for the rising trend and larger-than-unity value observed experimentally.

Exploring physical aging in PIM-1 using molecular dynamics

This comprehensive study explored the aging process of PIM-1, a ladder polymer of intrinsic microporosity (PIM), by applying molecular dynamics simulations for the first time. Through detailed analysis, our work illustrates the evolution of the polymer structure from a loosely packed, less dense state of the pristine polymer to a more tightly packed configuration due to physical aging. For this purpose, a novel molecular dynamics (MD) methodology was employed in the process toward equilibration of PIM-1. This structural transition was quantitatively captured by measuring key parameters such as density, fractional free volume (FFV), cohesive energy density (CED), d-spacing, surface area, and gas permeabilities. The simulations demonstrate a noticeable increase in density by approximately 7 % in aged PIM-1 compared to a fresh sample. This increase in density is accompanied by a corresponding decrease in FFV, suggesting a more compact molecular arrangement. The impact of these structural changes is evident in the gas transport properties. Permeabilities of all gases tested, He, H2, O2, N2, CO2 and CH4, decreased by 33 %–80 %. Moreover, the selectivity of gas pairs like CO2/CH4 and O2/N2 exhibited increasing trends due to aging, as previously reported in experimental work. Structural analysis performed on the fresh and aged structures indicated collapse of free volume over aging, by disappearance of pores larger than ∼6.5 Å. Furthermore, no intrachain rearrangement was observed during physical aging in the ladder PIM-1 structure; rather, the aging resulted in increased interchain packing efficiency. Our methodology can be employed to other PIM architectures, such as polyimides of intrinsic microporosity (PIM-PIs) as well as low-free volume glassy polymers.

Transferable Anisotropic Mie Potential Force Field for Alkanediols.

The development of force fields for polyfunctional molecules, such as alkanediols, requires a careful account of different average intramolecular conformations for gas states compared to dense liquid states, where intra- and intermolecular hydrogen bonds compete. In the present work, the transferable anisotropic Mie (TAMie) potential is extended to 1,n-alkanediols. Using the convention that intramolecular nonbonded interactions up to and including the third neighbor are excluded, all force field parameters developed previously for 1-alcohols were transferred to 1,5-pentanediol and beyond, with good agreement with experimental phase equilibrium data. To obtain trans-gauche ratios of 1,2-ethanediol and 1,3-propanediol that are consistent with experimental results, the propensities for intra- and intermolecular hydrogen bonds had to be balanced. This was achieved by parameterizing the intramolecular dihedral energy functions governing the O-C-C-O and O-C-C-C angles while intramolecular charge-charge interactions were active. All partial charges belonging to a functional group are collected in a charge group and all interactions among two charge groups are evaluated even if they are separated by less than three bonds. With this approach, it is possible to apply the nonbonded parameters from 1-alcohols to alkanediols without further refinement. The agreement with experimental phase equilibrium and shear viscosity data is of similar quality as for the 1-alcohols and the trans-gauche ratio agrees with literature results from spectroscopic measurements and ab initio calculations.

Research on the density of underwater sand and gravel fillings based on geotechnical centrifugal tests

The density of underwater dumping materials plays a major role in cofferdam engineering designs. However, it is difficult to accurately measure the density of underwater dumping materials. This study investigated the influence of particle size distribution of granular materials on the density of underwater filling materials. Considering the underwater dumping project of a hydropower station dam in the Han River as the prototype condition, several underwater dumping density centrifugal tests were conducted on sand gravel and sand mixtures. Based on the CKY200 large-scale geotechnical centrifuge, a single-embankment vertical-blockage underwater filling test device in a centrifuge field was developed. The results demonstrated the relationship between the compactness of the dumping body and the grading of loose particles, depth of dumping, and height of the upper loading. This indicates that the underwater filling material has a higher compactness and can reach a dense state. When the grading is poor, the compactness decreases. The greater the depth of filling, the greater the compactness. When vertical compression was applied to the upper part of the backfill, the compactness of the backfill, particularly in shallow areas, was significantly improved. These results provide insights for the design and construction of underwater dumping water conservation systems.

The failure type-dependent characterization of liquefaction resistance by small-strain shear modulus for saturated sand

In this study, a re-visit of existing laboratory tests was carried out to study the relationship between the liquefaction resistance (CRR) and the small-strain shear modulus (Gmax) of saturated sands with consideration of the failure types of both cyclic mobility and flow liquefaction. The result indicates that the relationship between CRR and Gmax is failure type-dependent, and the liquefaction resistance of cyclic mobility grows faster than that of flow liquefaction. Then discrete element method was used to explore the relationship between the liquefaction resistance and the small-strain shear modulus for a typical saturated granular material, with consideration of different liquefaction types. A series of undrained stress-controlled cyclic tests together with shear wave velocity measurements were simulated, and results similar to the laboratory studies were obtained. Then a new expression is proposed to describe the relationship between CRR and Gmax for granular material. The corresponding micromechanical mechanism is further explored, which shows that there are two kinds of distinct behaviors of the particle contact structure when the granular material changes from loose to dense state under the same confining stress. Compression behavior is dominant for flow liquefaction while collapse behavior is dominant for cyclic mobility type of liquefaction. The different behaviors of the particle contact structure influence the growth of the mechanical contacts, which further leads to the failure type-dependent growth of liquefaction resistance for a saturated granular material.

Development of a Length-Based Cell-State Framework Toward the Re-Creation of Large-Scale Dense Congestion Patterns

This paper presents the results and novel findings of generating a simplified version of the prevailing traffic features that existed during a major evacuation. Leveraging the underlying framework provided by the widely used cell transmission model, the desire is to reconstruct the unique characteristics of large congestion patterns that propagate under dense traffic states, where limited attempts at scaling this base model have occurred. The length-based cell-state framework presented can reproduce large spatiotemporal congestion patterns that exist, specifically from large-scale evacuations. To further simplify, the framework considers traffic state heuristics which are calibrated through oblique cumulative count and occupancy curves. As a result of this preprocessing technique, an artifact was found from the use of the cumulative curves under the lens of Newell’s two-phase traffic flow theory where three unique, separate queued regimes were identified within the fundamental diagrams. The methodology re-created a unique large-scale congestion pattern that existed during a past regional evacuation event, Hurricane Irma, the subject of this paper. To test this methodology, a large-scale congested period was analyzed, both with probe vehicle trajectory data and stationary radar detector data. Results demonstrate that traffic re-creation into state-based contours was able to be verified near a 90% level of confidence even at large spatiotemporal extents.