Wide Range Of Aspect Ratios Research Articles

Modeling of equivalent strain in 2D cross-sections of open die forged components using neural networks

Open die forging is one of the oldest manufacturing methods known to remove defects in the ingot resulting from the casting process. The improved properties of the final component are highly dependent on the strain distribution. Although sinusoidal equations and empirical formulations have been already used to estimate the strain, they have been applied only to the core of the workpiece. In this work, a novel approach is presented to model the equivalent strain distribution in 2D cross-sections, in the direction of the press, of open die forged components using neural networks. The proposed method efficiently combines a parametric sinusoidal function with a neural network to learn the complex relationships between the process parameters and the resulting local strain. The neural network is trained on a dataset of finite element (FE) simulations of rectangular geometries that cover a wide range of aspect ratios, bite ratios, and height reductions. The presented methodology with near real-time prediction capabilities shows good agreement with FE results. Moreover, the parametric function captures the characteristic pattern of the strain distribution and reveals certain physical relationships affecting the deformation of the material. These patterns are later examined by analyzing the parameters identified in the parametric sinusoidal function.

TSAF-Net: a rotated two-stage Cnaphalocrocis medinalis damage detection method based on anchor-free arbitrary-oriented proposal network.

Cnaphalocrocis medinalis (C.medinalis) is an agricultural pest with recurrent outbreaks. The investigation into automated pest and disease detection technology holds significant value for in-field surveys. Current generic detection methods are inadequate due to arbitrary orientations and a wide range of aspect ratios in damage symptoms. To tackle these issues, we put forward a rotated two-stage detection method for in-field C.medinalis surveys. This method relies on an anchor-free rotated region proposal network (AF-R2PN), bypassing the need for hyper-parameter optimization induced by predefined anchor boxes. An in-field C.medinalis dataset is constructed during on-site pest surveys to validate the effectiveness of our method. The experimental results show that our method can accomplish 80% average precision (AP), surpassing the corresponding horizontal detector by 2.3%. The visualization results of our work showcase its exceptional localization capability over generic detection methods, facilitating inspection by plant protectors. Meanwhile, our proposed method outperforms other state-of-the-art rotated detection algorithms. The AF-R2PN module can generate superior arbitrary-oriented proposals even with a decreased number of proposals, balancing inference speed and detection performance among other rotated two-stage methods. The proposed method exhibits superiority in detecting C. medinalis damage under complex field conditions. It provides greater practical applicability during in-field surveys, enhancing their efficiency and coverage. The findings hold significance for pest and disease monitoring, providing important technical support for agricultural production. © 2024 Society of Chemical Industry.

Effects of Impact Energy and Aspect Ratio on the Motion of Particle Clouds in Stagnant Water

Abstract A series of laboratory experiments was conducted to investigate the effects of impact energy and other initial controlling parameters on the motion of particle clouds in stagnant water. Experiments were performed for two median sand diameters of D50 = 0.52 mm and 0.74 mm and nozzle diameters of do = 6 mm and 8 mm. Sand masses were converted to an equivalent pipe length with the same diameter as the nozzle, Lo, and a wide range of aspect ratios, Lo/do, between 2 and 93 was tested. The impact energy of sand particles was controlled by the release height of sand particles, and it was quantified by the non-dimensional release height, η, ranging from 1 to 21.5. It was found that particle clouds with higher impact energy had smaller concentration and velocity decay rates. This indicated that by increasing the release height, the momentum transfer between sand particles and the ambient water decreases. The time-series of instantaneous sand velocity were used to determine velocity fluctuations and turbulence intensity of sand particles and a direct correlation was found between sand velocity fluctuations and aspect ratio in particle clouds. The effects of impact energy on the anatomy of the resulted particle clouds were examined in this study. It was found that the cloud width increased dramatically when the impact energy of sand particles with high aspect ratios (i.e., Lo/do > 39) increased. Furthermore, the dispersion of sand particle began earlier as the kinetic energy of sand particles increased at the water surface.

Hydrodynamic force and torque models for cylindrical particles in a wide range of aspect ratios

During the pneumatic conveyance of biomass in a coal-fired power station boiler, biomass particles have cylindrical shapes with different aspect ratios. They move through the fluid at any angle and rotate strongly. However, highly accurate and general models of the drag, lift, and torque coefficients (CD, CL, and CT) for biomass particles in a wide range of aspect ratios, especially the CT model and the high aspect ratios, are currently lacking. This paper presents detailed direct numerical simulations of the flow around cylindrical cylinders with varying aspect ratios (6 ≤ AR ≤ 22), Reynolds numbers (100 ≤ Re ≤ 2000), and angles of incidence (0° ≤ θ ≤ 90°). The simulation was conducted using the OpenFOAM solver with the body-fitted mesh method. The flow characteristics and force coefficients of cylindrical particles with different AR were systematically analyzed. New functional correlations between CD, CL, and CT and AR, Re, and θ values were established. The mean squared errors for CD, CL, and CT were 8.8 × 10–2, 2.4 × 10–2, and 4.7 × 10–2, with average relative errors of 5.8%, 3.5%, and 8.17%, respectively. A comparison of the results with other experimental and simulation data in previous literatures showed that the new CD and CL models have considerable higher predictive ability. The generality of the new CD model expanding to low ARs of 1.5 and 3 is verified finally. The new force and torque models are expected to improve the accuracy of Eulerian–Lagrangian simulations of various cylindrical particle-laden flows in the utility of biomass energy.

Topography prediction of high-aspect ratio features milled with overlapping abrasive slurry jet footprints considering fluid confinement effects

Overlapping adjacent passes of abrasive slurry jets can be used to fabricate micro-pockets or blind micro-slots. This study investigates the propagation of surfaces milled using overlapping passes of a high-pressure abrasive slurry jet on a ductile 6061-T6 target over a wide range of aspect ratios. Features such as shallow pockets with low aspect ratios to deep slots with aspect ratios ∼1.5 were fabricated to investigate the correlations between the aspect ratio, degree of pass overlap, and number of repeating passes with the machined surface evolution characteristics. A comprehensive model was presented that combined computational fluid dynamics (CFD) with surface evolution to predict the evolving machined feature topography after each of the overlapping and repeating passes, and to provide insights into experimental observations. The model explicitly considered the CFD-predicted local particle impact angles and velocities as well as effects due to secondary impacts, high sidewall slopes, and stagnation effects. For larger degrees of overlap, measurements revealed a more than linear rate of increase in depth after each repeat of two adjacent overlapped passes, as opposed to a linear depth increase for smaller overlaps and blind pockets. Large overlaps were found to result in asymmetric features. Up to a critical aspect ratio of ∼0.65, the model predicted the surface evolution of the features to within <8.6% of those measured. Beyond that, randomness in the machined feature shape and size made the process challenging to control and the surface evolution difficult to predict. Nevertheless, the model was able to elucidate the reasons for the randomness and other observed phenomena such as the more than linear growth in etch rate, and the occurrence of feature asymmetry. The findings emphasize that flow confinement, increases in the jet's turbulent kinetic energy, and the formation of vortices at the bottom of the machined features are critical factors influencing the machining process, and that in these cases explicit modeling approaches like the one presented in this study must be used.

Bio-Inspired Magnetically Responsive Silicone Cilia: Fabrication Strategy and Interaction with Biological Mucus.

Cilia are biological structures essential to drive the mobility of secretions and maintain the proper function of the respiratory airways. However, this motile self-cleaning process is significantly compromised in the presence of silicone tracheal prosthesis, leading to biofilm growth and impeding effective treatment. To address this challenge and enhance the performance of these devices, we propose the fabrication of magnetic silicone cilia, with the prospect of their integration onto silicone prostheses. The present study presents a fabrication method based on magnetic self-assembly and assesses the interaction behavior of the cilia array with biological mucus. This protocol allows for the customization of cilia dimensions across a wide range of aspect ratios (from 6 to 85) and array densities (from 10 to 80 cilia/mm2) by adjusting the fabrication parameters, offering flexibility for adjustments according to their required characteristics. Furthermore, we evaluated the suitability of different cilia arrays for biomedical applications by analyzing their interaction with bullfrog mucus, simulating the airways environment. Our findings demonstrate that the fabricated cilia are mechanically resistant to the viscous fluid and still exhibit controlled movement under the influence of an external moving magnet. A correlation between cilia dimensions and mucus wettability profile suggests a potential role in facilitating mucus depuration, paving the way for further advancements aimed at enhancing the performance of silicone prostheses in clinical settings.

Numerical Evaluation of the Elastic Moduli of AlN and GaN Nanosheets.

Two-dimensional (2D) nanostructures of aluminum nitride (AlN) and gallium nitride (GaN), called nanosheets, have a graphene-like atomic arrangement and represent novel materials with important upcoming applications in the fields of flexible electronics, optoelectronics, and strain engineering, among others. Knowledge of their mechanical behavior is key to the correct design and enhanced functioning of advanced 2D devices and systems based on aluminum nitride and gallium nitride nanosheets. With this background, the surface Young's and shear moduli of AlN and GaN nanosheets over a wide range of aspect ratios were assessed using the nanoscale continuum model (NCM), also known as the molecular structural mechanics (MSM) approach. The NCM/MSM approach uses elastic beam elements to represent interatomic bonds and allows the elastic moduli of nanosheets to be evaluated in a simple way. The surface Young's and shear moduli calculated in the current study contribute to building a reference for the evaluation of the elastic moduli of AlN and GaN nanosheets using the theoretical method. The results show that an analytical methodology can be used to assess the Young's and shear moduli of aluminum nitride and gallium nitride nanosheets without the need for numerical simulation. An exploratory study was performed to adjust the input parameters of the numerical simulation, which led to good agreement with the results of elastic moduli available in the literature. The limitations of this method are also discussed.

Theoretical estimation of sound absorption characteristics in a collection of rectangular holes: Comparison with experimental results

This study quantifies the sound absorption properties of small rectangular or square pores that are less than a few millimeters per side, based solely on their geometric dimensions. Analytical solutions for the sound absorption coefficient of narrow tubes with rectangular holes have not been obtained. Therefore, alternative methods of predicting the sound absorption coefficient, such as using the circular tube approximation or the two-plane approximation, are possible. In this study, the sound absorption coefficient was estimated by several theoretical models that are considered useful for estimating the sound absorption coefficient in rectangular tubes. The results were then compared with experimental values. For square holes, the accuracy of the sound absorption coefficient increased in the order of the model considering two-sided circumference only, the circular tube model, and Allard's method based on Stinson's. In rectangular holes, Allard's method based on Stinson's showed good agreement with the experimental data across a wide range of aspect ratios. For rectangular holes, the accuracy of Stinson's two-plane approximation was superior to that of the circular tube approximation when the aspect ratio was 4. Furthermore, when the aspect ratio was 8, the accuracy of Stinson's two-plane approximation became comparable to that of Allard's method based on Stinson's.

Controlling the roll-to-helix transformation in electron-beam-patterned gel-based micro-ribbons.

Helix formation has been of ongoing interest because of its role in both natural and synthetic materials systems. It has been extensively studied in gel-based ribbons where swelling anisotropies drive out-of-plane bending. In contrast to approaches based on photolithography or mechanical bilayer construction, we use electron-beam patterning to create microscale ribbons at ∼1-100 μm length scales in pure homopolymer precursor films of poly(acrylic acid) (PAA). The radiation chemistry creates a ribbon comprising a crosslinked hydrophobic top layer and a hydrophilic gel bottom layer with a continuous through-thickness variation in between. The classic roll-to-helix transition occurs as the ribbon aspect ratio increases. Notably, we see examples of single-loop rolls, multi-loop rolls, minimal-pitch helices, plus a transition structure comprising both helical and roll-like features. Finite-element modelling recapitulates key aspects of these conformations. Increasing the pH from below to above the PAA pKa increases the out-of-plane bending to the extent that the ribbons plastically deform and nonminimal-pitch helices form across a wide range of aspect ratios and irradiation conditions. The nonminimal pitch is caused by an in-plane anisotropy associated with the plastic deformation. We mimic this anisotropy by patterning ribbons comprising micro-tiles separated by gaps which receive electron exposure due to proximity effects. We observe a transition from roll to helix to tube with increasing gap angle. The chirality is completely determined by the gap orientation (±θ). However, in contrast to established approaches to generate in-plane anisotropies based on mechanical properties, finite-element modelling indicates that anisotropic through-thickness swelling of the gap material plays a dominant role in helix formation and suggests that this micro-composite ribbon behaves like a rigid origami metamaterial where deformation at the creases (the gaps) between structural elements controls the shape shifting.

Scalable and adaptable two-ligand co-solvent transfer methodology for gold bipyramids to organic solvents.

Large and faceted nanoparticles, such as gold bipyramids, presently require synthesis using alkyl ammonium halide ligands in aqueous conditions to stabilize the structure, which impedes subsequent transfer and suspension of such nanoparticles in low polarity solvents despite success with few nanometer gold nanoparticles of shapes such as spheres. Phase transfer methodologies present a feasible avenue to maintain colloidal stability of suspensions and move high surface energy particles into organic solvent environments. Here, we present a method to yield stable suspensions of gold bipyramids in low-polarity solvents, including methanol, dimethylformamide, chloroform, and toluene, through the requisite combination of two capping agents and the presence of a co-solvent. By utilizing PEG-SH functionalization for stability, dodecanethiol (DDT) as the organic-soluble capping agent, and methanol to aid in the phase transfer, gold bipyramids with a wide-range of aspect ratios and sizes can be transferred between water and chloroform readily and maintain colloidal stability. Subsequent transfer to various organic and low-polarity solvents is then demonstrated for the first time.

Sample size effects on the critical state shear strength of granular materials with varied gradation and the role of column-like local structures

Assessing the shear strength of coarse granular soils is challenging because testing devices in the laboratory often limit the maximum particle size (dmax). Although engineering standards define representative elementary volumes (REVs) using the aspect ratio α = X/dmax, where X is the characteristic sample size, they often disagree on the minimum α, as the effects of sample scale on shear strength are still not well understood. This paper presents a discrete-element study on the combined effect of specimen size and grading on the critical state shear strength of granular materials. The study covers a wide range of aspect ratios and demonstrates that the macroscopic response is stable for α ≥ 15 – which is significantly higher than the standard requirement of α ≥ 10 for simple shear tests. The granular microstructure is also strongly affected by α and the formation of column-like structures of grains carrying strong contact forces, reaching sample size independent conditions only for α ≥ 20. Such column-like structures are shown to be primarily composed of the largest classes of grains, supporting the fact that grading has no effect on the critical state shear strength and dmax correctly serves to scale a granular sample to the size of the testing device.

Designing regression approach for mode frequency prediction of empty and filled steel silos

In this study the primary objective is to design prediction model for the free vibration analysis of thin circular cylindrical steel silos having various aspect ratios in empty and varying filled conditions for different types of closures. A finite element method (FEM) is used to carry out the free vibration analysis of steel silos. It is found that the effect of different aspect ratios slender, intermediate slender and squat steel silos is very significant for dynamic response of silo. The silos are considered having open, flat and cone type of closures at its top end. The clamped-free (cantilever) boundary condition is taken for this approach as actual silos are fixed at flat-base. The structural mass of thin cylindrical shell steel silo is made constant for a particular height and diameter. The eigenvalues of the thin cylindrical shell steel silos are extracted by using block Lanczos method. The free vibrations of thin cylindrical shell steel silo with different aspect ratios, radius to thickness ratio are studied. From the present studies it is seen that as aspect ratio increases the fundamental frequency is reduced in empty silo. It is more in the case of squat silo. It can be seen that the fundamental frequency is less in the case of flat closure in all the aspect ratios of the silo. The frequency values are more in the case of cone closure is observed. Also as the mode number increases the modal frequency value increases. Further, as the filling level is increased the modal frequency also increases. Finally, regression approach is adopted for predicting the mode frequency of empty and filled silos for wide range of aspect ratios.

Evolution of wake structure with aspect ratio behind a thin pitching panel

The evolution of wake structures behind thin pitching panels at Reynolds number 1000 is studied numerically for a wide range of aspect ratios (0.54≤AR≤16). At the maximum pitching angle (θmax) of 5° and 15°, simulations are performed for pitching frequency St=0.5,1. The higher pitching angle and frequency promote thrust generation for all the AR. Although the propulsive power grows with AR in the thrust cases, the propulsion efficiency remains insensitive to the AR. Higher AR imparts stabilizing effect on the flow in the drag regime, though it triggers instabilities with asymmetric vortex pairing in the thrust cases. Wake topology for the drag cases reveals the emergence of horseshoe vortices and bridgelets-type vortex structures within the range of AR studied. The wake consists of entangled vortices undergoing subsequent reconnections in the thrust cases. A smaller θmax and St induces organized 3D structures for AR≤4, although the end instabilities diffuse for increasing AR, resulting in a 2D wake signature at larger AR. The spanwise circulation data show the dominant influence of primary instability in rendering a high horizontal velocity-compressed separated region in the drag regime.

On shear adhesion of adhesive fibrils

Natural fibrillar adhesives, widely recognized for their strong and reversible adhesion, have inspired the development of numerous synthetic adhesive systems applied in diverse fields. These biological and bioinspired adhesive fibrils exhibit a wide range of aspect ratios spanning four orders of magnitude. Accurate prediction of their adhesion performance is crucial for their practical applications. Prior investigations have primarily focused on adhesion under normal loading, although shear loading is also commonly encountered in various scenarios. To date, only a few shear adhesion models exist, and they are limited to either high or low aspect ratios. Rigorous mechanics analysis of adhesive fibrils’ shear adhesion strength across a wide range of aspect ratios is lacking. In this study, we developed a mechanics model based on the compliance method for evaluating the energy-controlled interfacial failure of the adhesive fibrils, estimated the shear adhesion strength of a lap shear system across a wide range of fibrillar aspect ratios, and carried out the finite element analysis (FEA) to validate the model prediction. Our model reveals that, depending on the fibrillar aspect ratio, the adhesive fibril exhibits three distinct deformation regimes: thin film shearing, thick block shearing, and slender beam bending. The important parameters governing the shear adhesion of the lap shear system are the aspect ratio of fibrils, elastic moduli of the fibrils and substrates, while the Poisson's ratio of fibrils has no noticeable effect. Our model captures the shear compliance across a wide aspect ratio range from 10−4 to 102 accurately and is in excellent agreement with the FEA results. Based on this compliance solution, a rigorous scaling law for shear adhesion strength is derived, which can predict the energy-controlled adhesion regime as well as the theoretical strength-limited regime, as the aspect ratio decreases. These results reveal the underlying mechanisms governing the shear adhesion strength of fibrillar adhesives and provide guidance for future design and optimization of fibrillar adhesives.

Experimental wind-tunnel study of the dynamics of inverted foils for energy harvesting

Abstract This paper describes the methodology used to analyse oscillations of foils of a wide range of aspect ratios, 0.5 ≤ AR ≤ 4, and Reynolds numbers, 104 ≤ Re ≤ 105, for energy harvesting purposes. The foils were fixed at their trailing edge, and their dynamical behaviour was captured as the wind speed was varied. The foil response was then analysed as a function of velocity, Reynolds number, oscillation amplitude and frequency. Additionally, the forces and moments acting on the foils were measured, utilising an aerodynamic scale, designed and built in-house. An empirical power generation equation was derived to determine the foil characteristics for maximum energy harvesting production. The results show that a flexible foil with AR = 3 with oscillations in the large-amplitude regime is the most effective for energy harvesting.

Investigation of aspect ratio effects on flow characteristics and vorticity generation in shock-induced rectangular bubble

In shock-induced Richtmyer–Meshkov instability, the polygonal bubbles, including the rectangular interface can offer favorable circumstances for shock refraction research. Also, the aspect ratio is crucial in characterizing the physics behind this instability. Therefore, the aspect ratio effects on the flow characteristics and vorticity generation in the shock-induced rectangular light gas bubbles are investigated numerically in this study. This investigation is performed for a wide range of aspect ratios varying from 0.25 to 3.0. These effects are highlighted in the interface morphology, wave paradigms, vorticity generation, enstrophy evolution, and a qualitative examination of interface deformation. For simulating two-component gas flows, a high-order explicit modal discontinuous Galerkin approach is employed to solve a two-dimensional system of compressible inviscid Euler equations. Existing experimental results for shock-induced square and cylindrical light bubbles are used to validate the numerical model and solver. The results indicate that the effects of aspect ratio are critical in characterizing the interface morphology during the interaction between the shock wave and rectangular bubble. The interface morphology evolves faster as the aspect ratio increases, and the process of transverse jet formation is observed to be significantly different. The aspect ratio effects result in a substantial change in the flow field with bubble deformation, vortex development, vorticity generation, and transverse jet formation. The effects of aspect ratio are further investigated in detail through the mechanism of vorticity generation and enstrophy evolution. Finally, these effects on shock trajectories and interface characteristics over time are thoroughly explored.

Modelling of CFRP-Strengthened RC Shear Walls with a Focus on End-Anchor Effects

This study first provides an overview of the development of a novel tube anchor system for the seismic strengthening or repair of reinforced concrete (RC) shear walls with carbon fibre-reinforced polymer (CFRP) sheets. The new anchor system can significantly improve the load transfer mechanism between the CFRP and supporting RC structural elements, resulting in ductile behaviour of the strengthened shear walls with increases of lateral load capacity and ductility by up to 2.6 and 8.3 times, respectively. The study then presents a new finite element modelling technique capable of capturing the complete cyclic response, i.e., from the elastic behaviour to the ultimate collapse of CFRP-strengthened RC shear walls with the newly developed tube anchor system. Two different modelling approaches are proposed to consider the effects of the tube anchor system. Additionally, other important CFRP- and RC-related mechanisms, including CFRP debonding effects, confinement enhancement, tension stiffening, compression softening, and strength and stiffness degradation under cyclic loads, are also considered in the model. By comparing the analytical and experimental results, it is demonstrated that the proposed modelling approach can accurately replicate the complex behaviour of CFRP-strengthened shear walls with a wide range of aspect ratios, from the ductile flexural behaviour of slender walls to the brittle shear failure of squat walls, without requiring detailed modelling of the anchor system.

Two-Dimensional Energy Histograms as Features for Machine Learning to Predict Adsorption in Diverse Nanoporous Materials.

A major obstacle for machine learning (ML) in chemical science is the lack of physically informed feature representations that provide both accurate prediction and easy interpretability of the ML model. In this work, we describe adsorption systems using novel two-dimensional energy histogram (2D-EH) features, which are obtained from the probe-adsorbent energies and energy gradients at grid points located throughout the adsorbent. The 2D-EH features encode both energetic and structural information of the material and lead to highly accurate ML models (coefficient of determination R2 ∼ 0.94-0.99) for predicting single-component adsorption capacity in metal-organic frameworks (MOFs). We consider the adsorption of spherical molecules (Kr and Xe), linear alkanes with a wide range of aspect ratios (ethane, propane, n-butane, and n-hexane), and a branched alkane (2,2-dimethylbutane) over a wide range of temperatures and pressures. The interpretable 2D-EH features enable the ML model to learn the basic physics of adsorption in pores from the training data. We show that these MOF-data-trained ML models are transferrable to different families of amorphous nanoporous materials. We also identify several adsorption systems where capillary condensation occurs, and ML predictions are more challenging. Nevertheless, our 2D-EH features still outperform structural features including those derived from persistent homology. The novel 2D-EH features may help accelerate the discovery and design of advanced nanoporous materials using ML for gas storage and separation in the future.

Improved method for generating sand assembly with wide range of aspect ratios and angularities based on insights gained from comparative study of existing techniques

The generation of realistic sand assemblies with a wide range of particle shapes is important for investigating the influence of particle shape on the microscale and macroscale mechanical behaviors of sands using the discrete element method. The major contribution of this study is the development of an improved technique for such assemblies. The method generates sand assemblies with a wide range of aspect ratios and angularities and retains the particle size effects and major morphological characteristics of the original particles. First, based on the insights gained from a comparative study of existing techniques, a method that integrates principal component analysis (PCA) with coefficient standardization is selected as the basic framework for particle generation. Second, by expanding the spherical harmonics (SHs) of the compensation radii between particles and their circumscribed super-ellipsoid surfaces, a new method that can extract the aspect ratio characteristics of sand particles is proposed for particle reconstruction. Finally, a method integrating the SH expansion of the compensation radius, PCA, and coefficient standardization is formulated and demonstrated to be efficient in generating sand assemblies with a wide range of aspect ratios and angularities.

Structure of jammed ellipse packings with a wide range of aspect ratios.

Motivated in part by the recent observation of liquid glass in suspensions of ellipsoidal colloids, we examine the structure of jammed two-dimensional ellipse packings over a much wider range of particle aspect ratios (α, the ratio of the major and minor axis lengths) than has been previously attempted. We determine the jamming densities ϕJ(α) to high precision, and find empirical analytic formulae that predict ϕJ(α) to within less than 0.1% for all 1≤α≤10, for three different particle dispersities. Then we explore how these packings' local structural order varies with α. We find that the densest packings possess unusually-well-defined nearest-neighbor shells, including both a higher fraction fZ=6 of particles with exactly six contacts and a previously-unreported short-range order marked by "kinetically suppressed" regions in their positional-orientational pair correlation function g(r,Δθ). We also show that the previously-reported approach to isostaticity (coordination number ZJ → Ziso ≡ 6) with increasing α is interrupted and then reversed as local nematic order increases: ZJ(α) drops towards 4 as ellipses are more often trapped by contacts with a parallel-oriented neighbor on either side and a perpendicularly-oriented neighbor on either end. Finally we show that ϕJ/ϕs (where ϕs is the saturated RSA packing density) is nearly α-independent for systems that do not develop substantial local hexatic or nematic order during compression.