Incremental Compression Research Articles

Modewise Johnson–Lindenstrauss embeddings for nuclear many-body theory

In this work, we explore modewise Johnson-Lindenstrauss embeddings (JLEs) as a tool to reduce the computational cost and memory requirements of nuclear many-body methods. JLEs are randomized projections of high-dimensional data tensors onto low-dimensional subspaces that preserve key structural features. Such embeddings allow for the oblivious and incremental compression of large tensors, e.g., the nuclear Hamiltonian, into significantly smaller random sketches that still allow for the accurate calculation of ground-state energies and other observables. Their oblivious character makes it possible to compress a tensor without knowing in advance exactly what observables one might want to approximate at a later time. This opens the door for the use of tensors that are much too large to store in memory, e.g., complete two-plus three-nucleon Hamiltonians in large, symmetry-unrestricted bases. Such compressed Hamiltonians can be stored and used later on with relative ease. As a first step, we analyze the JLE's impact on the second-order Many-Body Perturbation Theory (MBPT) corrections for nuclear ground-state observables. Numerical experiments for a wide range of closed-shell nuclei, model spaces and state-of-the-art nuclear interactions demonstrate the validity and potential of the proposed approach: We can compress nuclear Hamiltonians hundred- to thousand-fold while only incurring mean relative errors of 1\% or less in ground-state observables. Importantly, we show that JLEs capture the relevant physical information contained in the highly structured Hamiltonian tensor despite their random characteristics. In addition to the significant storage savings, the achieved compressions imply multiple order-of magnitude reductions in computational effort when the compressed Hamiltonians are used in higher-order MBPT or nonperturbative many-body methods.

Abnormal grain growth of FeMnAlNiCo shape memory alloys during directional recrystallisation

Polycrystalline FeMnAlNi-based alloys generally exhibit poor pseudoelasticity owing to grain constraint. A promising method to improve the pseudoelasticity involves increasing the grain size by directional recrystallisation (DR). To improve the efficiency of obtaining large grain size, the effect of DR parameters—hot zone temperature (HZT) and drawing velocity—on the columnar grain size and the mechanisms of grain growth were investigated. The results showed that samples of FeMnAlNiCo shape memory alloys (SMAs) with an average grain size of over 20 mm and the largest grain size exceeding 50 mm were obtained after DR. The apparent activation energy of the columnar grain growth for DR was ≈135 kJ/mol, which was much lower than that of the equiaxed grain growth for isothermal annealing (≈384 kJ/mol). The lateral growth of the columnar grains was probably because the boundaries between columnar grains tend to form random high-angle grain (HAG) boundaries. By incremental compression test, at an applied strain of 7.0%, nearly <104> oriented single crystal exhibited a recoverable strain of ≈6.0%, while the polycrystal had a recoverable strain of only ≈3.4%. This work provides important guidance and inspires new strategies for microstructural control in FeMnAlNi-based SMAs.

Microstructure, deformation behaviors and GND density evolution of Ti-Al laminated composites under the incremental compression test

It is extremely difficult to study the deformation behaviors through the direct experimental observations. In this work, GND density was used to study the deformation process of composites under the incremental compression test. The SEM and EBSD techniques were used to investigate the microstructure, phase formation process and deformation process of Ti-Al laminated composites in detail. Results show that: during the deformation process, the GND density of the Al and Ti layers gradually increased, while the Al 3 Ti layer decreased first and then increased. And the Al 3 Ti layer was a coordinated deformation under the constraint of layered structure and then plastic deformation occurred. GND was uniformly distributed in the Al layer first and then concentrated at the Al/Al 3 Ti interface, while it was not uniformly distributed in the Ti layer. The formation process of the Al 3 Ti layer and the fracture surface morphology have also been studied.

Experimental study on thermo-mechanical properties of Beishan granite under mild temperature

Temperature is believed to have an important influence on the mechanics behavior of granite. To investigate thermo-mechanical properties of Beishan granite, the host rock of China's preselected underground laboratory of high-level radioactive waste (HLW) geological repository, mechanical tests including uniaxial compression test and incremental cyclic loading-unloading test under mild temperature range (room temperature to 300 °C) were carried out with Acoustic emission (AE) activity monitoring. Results show: (1) The temperature threshold for Beishan granite is 150 °C. The UCS (uniaxial compressive strength) is increasing and pore is healing with increasing temperature in the range of room temperature to 150 °C, while the UCS is decreasing and pore is enlarging with increasing temperature in the range of 150 °C–300 °C. (2) The cracking activity in the compression process is significantly influenced by the ambient temperature. The AE activity of Beishan granite under different temperature exhibits three patterns (inactive-active for granite under room temperature, active-inactive-active under 60 °C–150 °C, active-inactive for granite under 200 °C and 300 °C). (3) Results of incremental cyclic loading-unloading compression tests show that the peak stress, peak strain and AE energy of granite increase with the elevated temperature. The strength and ductility are enhanced with increasing temperature in the mild range. (4) AE activity during the incremental cyclic loading-unloading test is used for loading-unloading response ratio (LURR) and felicity ratio (FR) analysis. The LURR value keeps increasing before pre-failure stress under lower temperature, but shows decrease trend before failure under higher temperature. The stress corresponding to the sharp drop on FR is identified as the stress threshold for rock damage, which are 0.57σc to 0.66σc for Beishan granite under the mild temperature conditions. This work will provide support for the long-term safety assessment for the HLW geological disposal engineering.

Sudden Slide Mechanism of a Rock Block in Road Cutting Slope with Soft and Hard Interlayered Bedding Structure Based on Energy Balance Theory

After the road excavation of the hard and soft interlayered bedding slope in the mountainous region's valley area, the bedding slope often results in a catastrophic phenomenon, especially in the project's construction and operation where existed severe safety hazards. A geomechanical two-component model consisting of the slider and the underlying layer is proposed to analyze the rock block instability under the fissure water pressure, the shear deformation, and the compression deformation. The slider's complex stress field is derived by using elastic mechanics. The incremental energy equilibrium Equation is established based on the energy balance theory, and the generalized sliding force relative function of the slider and the generalized shear force relative function of the underlying soft rock are obtained. The deformation energy accumulation, transfer, and energy dissipation characteristics are analyzed. Put a rock slide in the bedding rock cutting slope happened at Jiaojiatan, Pengshui County, Chongqing municipality, China as a case. Results indicate that considering both the compression deformation and the shear deformation of the slider, the kinetic energy, the rapid launch speed of the projectile, the average projectile acceleration, and the failure stroke increase about 15.7 times, 4.0 times, 1.8 times, and 8.9 times respectively than that of only considering the shear deformation, and the dynamic disaster intensity is more severe and worthy of attention. The results that ignored the fissure water pressure and the compressive deformation energy coincide with the existing literature, which verifies the reasonable applied method in this paper. Considering the slider's different displacements and the height-length ratios, when the energy ratio function that represents the ratio of the incremental compression energy to the incremental shear energy concludes that when the range of the height-length ratio is between 0 to 0.95(flat and narrow sliders), the compression energy's contribution to the system's elastic energy should be taken into consideration. The advantage of the energy balance method applied in the stability analysis of the bedding rock slope is that the potential unstable rock block's status can be predicted dynamically according to the variation of the underlying soft rock's deformation and that the elastic impact dynamic parameters can also be obtained compared with other instability analysis approach.

Depth camera based remote three-dimensional reconstruction using incremental point cloud compression

Real-time three-dimensional reconstruction is a fundamental technology applied by robots in unknown environments, especially in remote operating systems. This paper proposes a remote indoor environment reconstruction method based on incremental point cloud compression, which improves the effectiveness of teleoperation-based 3D mapping in the context of hazardous area work environments. First, due to the influence of data bandwidth in remote map building, this paper adds point cloud compression to the keyframe-based building method to form a new reconstruction technique using incremental point cloud compression, so as to realize the mapping of the remote environment with small data transmission. Second, a teleoperation system that integrates a remote robot platform and a local operation platform is constructed. Remote robot equipped with a depth camera can better complete the environmental reconstruction under the guidance of the local operator. Finally, we build the actual scene for 3D construction and perform task planning in the reconstruction model. Experimental results and data prove the practicality of our system.

Nonlinear Characterization of Tissue Viscoelasticity With Acoustoelastic Attenuation of Shear Waves.

Shear-wave elastography (SWE) measures shear-wave speed (SWS), which is related to the underlying shear modulus of soft tissue. SWS in soft tissue changes depending on the amount of external strain that soft tissue is subjected to due to the acoustoelastic (AE) phenomenon. In the literature, variations of SWS as a function of applied uniaxial strain were used for nonlinear characterization, assuming soft tissues to be elastic, although soft tissues are indeed viscoelastic in nature. Hence, nonlinear characterization using SWS alone is insufficient. In this work, we use SWS together with shear-wave attenuation (SWA) during incremental quasi-static compressions in order to derive biomechanical characterization based on the AE theory in terms of well-defined storage and loss moduli. As part of this study, we also quantify the effect of applied strain on measurements of SWS and SWA since such confounding effects need to be taken into account when using SWS and/or SWA, e.g., for staging a disease state, while such effects can also serve as an additional imaging biomarker. Our results from tissue-mimicking phantoms with varying oil percentages and ex vivo porcine liver experiments demonstrate the feasibility of our proposed methods. In both experiments, SWA was observed to decrease with applied strain. For 10% compression in ex vivo livers, shear-wave attenuation decreased, on average, by 28% (93 Np/m), while SWS increased, on average, by 20% (0.26 m/s).

Smart Table Tennis Racket with Tunable Stiffness for Diverse Play Styles and Unconventional Technique Training

AbstractSmart technologies bring innovation to the life and sports arena. To adapt to diverse play styles and improve unconventional technique of table tennis players, a smart table tennis racket with tunable stiffness based on anisotropic electrorheological elastomers (EREs) is developed. The EREs are prepared in the designed mold under the electric field to form an anisotropic structure that consisted of electrorheological particles and facilitated the generation of interparticle saturation surface polarization and the local electric field. Therefore, the electrorheological property of anisotropic EREs is significantly promoted, attaining a relative electrorheological effect of 17 160% in shear mode, and the incremental shear storage and compression modulus of 5.2 and 6.4 MPa. By applying an electric field, the smart racket successfully changes the trajectory of balls, reduced ejection angle by 11% and increased ejection velocity by 2%.

Mesoscale hetero-deformation induced (HDI) stress in FeAl-based metallic-intermetallic laminate (MIL) composites

Single-phase intermetallic FeAl layered material is synthesized using a layered foil approach to study the fracture mechanisms of FeAl-based metallic-intermetallic laminate (MIL) composites containing a similarly fabricated structure. The mechanical properties and crack evolution of the single-phase FeAl are investigated via incremental compression testing. Microstructure and composition assessment confirm a similar intermetallic layer laminate microstructure of single-phase FeAl and FeAl-based MIL composites. When compressed perpendicular to the layers, both materials fail by the axial splitting of the FeAl phase along the loading direction. Mesoscale hetero-deformation induced (HDI) stress, which is tensile on the FeAl layers of MIL composites, accelerates crack nucleation and crack propagation, eventually inducing failure. The HDI stress evaluated via finite element analysis (FEA) simulation provides an explanation for the difference between 430SS-FeAl and 304SS-FeAl MIL composites, which posses similar microstructure and composition, but very different strengths. When compressed parallel to the layers, mesoscale HDI stress is expected to be negligible, whereas the geometrically necessary dislocation (GND) pile-up induced HDI stress can enhance the performance of the composites. Fracture toughness is characterized via four-point bend testing, and the results demonstrate improvement of the FeAl-based MIL composites over the single-phase FeAl material.

Remote Sensing and Remote Actuation via Silicone-Magnetic Nanorod Composites.

The capacity for a soft material to combine remote sensing and remote actuation is highly desirable for many applications in soft robotics and wearable technologies. This work presents a silicone elastomer with a suspension of a small weight fraction of ferromagnetic nickel nanorods, which is capable of both sensing deformation and altering stiffness in the presence of an external magnetic field. Cylinders composed of silicone elastomer and 1% by weight nickel nanorods experience large increases in compressive modulus when exposed to an external magnetic field. Incremental compressions totaling 600 g of force applied to the same silicone-nanorod composites increase the magnetic field strength measured by a Hall effect sensor enabling the material to be used as a soft load cell capable of detecting the rate, duration, and magnitude of force applied. In addition, lattice structures are 3D printed using an ink composed of silicone elastomer and 1% by weight nickel nanorods, which possess the same sensing capacity.

Percolation mechanism and effective conductivity of mechanically deformed 3-dimensional composite networks: Computational modeling and experimental verification

In this work, the structural evolution of conductive polymer composites (CPCs) in response to mechanical deformation (uniaxial and biaxial compressive and tensile strains) is theoretically modeled and experimentally verified. The structural responses in mechanically deformed CPCs were simulated by incorporating the corresponding topological changes in representative volume element (RVE) and embedded filler networks. The percolating filler networks were then modeled as an equivalent electrical circuit consisting of tunneling and intrinsic resistances to examine the effect of deformation on the percolation threshold and the effective electrical conductivity. The results revealed that the filler alignment caused by strain changed both the vertical and lateral percolation thresholds, albeit with different trends. With an increase of uniaxial tensile (or equivalently, biaxial compressive) strain, applied on the vertical direction, the vertical percolation threshold initially reached a minimum value before rising, while the lateral percolation threshold monotonically increased. On the other hand, following incremental uniaxial compression (or equivalently, biaxial tension), the lateral percolation threshold reached a minimum value before increasing, while the vertical percolation threshold monotonically increased. The same relationship was observed in CPCs containing 1D fillers with different aspect ratios. The validity of the theoretical models was verified by comparing the predicted electrical conductivity values with the experimentally observed data obtained from polypropylene - multiwalled carbon nanotube nanocomposites.

A theory of incremental compression

The ability to find short representations, i.e. to compress data, is crucial for many intelligent systems. We present a theory of incremental compression showing that arbitrary data strings, that can be described by a set of features, can be compressed by searching for those features incrementally, which results in a partition of the information content of the string into a complete set of pairwise independent pieces. The description length of this partition turns out to be close to optimal in terms of the Kolmogorov complexity of the string. Exploiting this decomposition, we introduce ALICE – a computable ALgorithm for Incremental ComprEssion – and derive an expression for its time complexity. Finally, we show that our concept of a feature is closely related to Martin-Löf randomness tests, thereby formalizing the meaning of “property” for computable objects.

Design, fabrication and optimization of FeAl–FeAl2 eutectoid metallic-intermetallic laminate (MIL) composites

FeAl/FeAl2 eutectoid metallic-intermetallic laminate (MIL) composites were synthesized using a “multiple-thin-foil” configuration and a “two-stage reaction” strategy. Microstructure analysis via scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS) and electron backscatter diffraction (EBSD) confirms the formation of a two-intermetallic eutectoid structure, which decomposes from the high-temperature Fe5Al8 phase. The metal layers of eutectoid-MIL composites are fabricated with either pure iron or two different stainless steels without altering the intermetallic regions. The volume fraction of eutectoid layers is adjusted for optimizing the performance. The off-eutectoid phase is switched between FeAl and FeAl2 to investigate the effect on strength and ductility. The microstructure of the interfacial regions is fine-tuned, further demonstrating the ability to independently control the constituents of MIL composites. Additionally, a hybrid MIL composite of FeAl and the eutectoid structure is synthesized as a ‘proof-of-concept’. Finite element analysis (FEA) simulation is utilized to study the internal stress in the MIL composites from a macroscopic point of view. Incremental compression tests were conducted to track the fracture evolution from a microscopic point of view.

Deformation and fracture evolution of FeAl-based metallic-intermetallic laminate (MIL) composites

FeAl-based Metallic-Intermetallic Laminate (MIL) composites exhibit enhanced strength and ductility compared to previously studied MIL composites. The deformation and fracture evolution of the FeAl-based MIL composites are investigated here via incremental compression testing. Microstructure assessment via electron backscatter diffraction suggests that deformation proceeds in a fairly homogeneous manner across gradients in the microstructure. Eventual failure is mainly induced by normal stresses, whereas other MIL composites typically fail by shear induced localizations. Geometrically necessary dislocation analysis indicates the FeAl regions deform in similar manners for the three MIL composites (Fe-FeAl-MIL, 430SS-FeAl-MIL, and 304SS-FeAl-MIL), and each fails in a similar mode. While the FeAl phase is the majority constituent of the composites, the mechanical properties are significantly influenced by the softer metal layers. The transition layer formed between the Fe-based metal layers and FeAl regions is the most critical constituent of the composites. Although the volume fraction of the transition layer is only ∼15%, a stronger transition layer can improve the work hardening behavior of the FeAl phase, increasing MIL composite strength by as much as 1 GPa. The findings can guide the design of the MIL composites to achieve even better mechanical properties.

Reachability preserving compression for dynamic graph

Reachability preserving compression generates small graphs that preserve the information only relevant to reachability queries, and the compressed graph can answer any reachability query without decompression. Existing reachability preserving compression algorithms either require a long compression time or include redundant data in the compressed graph. In this paper, we propose a novel edge sorting alogrithm for fast, non-redudant reachability preserving compression. On the other hand, we found that the current incremental reachability compression algorithms for dynamic graphs may return incorrect results in some cases. Therefore, we propose two novel incremental reachability compression algorithms. An algorithm called incremental reachability preserving compression with optimum compression ratio, which generates an update compressed graph that is exactly the same as the graph computed by recompression. The other algorithm called fast incremental reachability preserving compression, which can update the compressed graph in a short time. Extensive experiments on real datasets show the efficiency and the effectiveness of our methods.

In vitro test methods for seating and fretting corrosion behavior of modular metal-on-metal acetabular tapers.

Retrieval studies show that metal-on-metal acetabular shell-liner tapers are susceptible to corrosion, which is hypothesized to arise from mechanically-assisted crevice corrosion (MACC). The role of materials on MACC of acetabular tapers has not been previously studied. In vitro tests of seating, pushout, and fretting corrosion performance of acetabular tapers are presented to assess the role of material combinations (Ti-6Al-4V shells, HC CoCrMo, LC CoCrMo, and 316L SS liners). The acetabular tapers were wet-assembled to a seating load of 1,000 N. The liner load-displacement seating mechanics were measured. Fretting corrosion currents were evaluated using a uniaxial incremental cyclic compression test up to 4,000 N, with the load applied at a 55° angle to the taper interface. Fretting currents, fretting onset loads, taper disengagement strength were measured and load-displacement plots were obtained. Pushout tests were also performed pre- and post-fretting corrosion. The average liner seating displacements varied from 134 to 226 μm across groups. Fretting currents at 3,600 N cyclic load were low and ranged between 0.05 and 0.27 μA and were independent of material combination (p > 0.05), reflecting small amounts of fretting. Fretting corrosion onset loads were between 1,800 and 2,100 N, and did not differ across groups (p > 0.05). Pushout loads were 27-43% of the maximum load applied. Fretting corrosion levels were very low for all material combinations and not different from one another. The seating and pushout responses were also not material dependent. The low fretting currents measured imply that MACC may not be a major cause for acetabular taper corrosion.© 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:00-111089, 2020.

Influence of slenderness ratio on the structural performance of lightweight foam concrete composite panel

In this research paper is reported the analytical and experimental investigations on the influence of slenderness ratio on the structural performance of lightweight foam concrete composite panel (LFCCP). Six full-scale tests of LFCCP panels differing in thickness were implemented under compression load. Compression load strength, load-strain profiles, load-deflection curves, influence of slenderness ratio, deformation, cracking patterns and classic modes of failure under incremental compression loads were analysed and deliberated. Nonlinear finite element modeling (FEM) using commercial software named LUSAS was used to simulate the structural behavior of LFCCP. The calculated ultimate compression strength capacity using empirical formulas established by many researchers, to expect the ultimate strength capacity of composite LFCCP panels were in comparison with the laboratory test results and FEM data attained; thus, a substantial agreement with the FEM data that were obtainable with a reasonable degree of accuracy, presented the increase in slenderness function.

Digital and Mechanical Characterization of Ureteral Stent Luminal Reduction in Response to Extrinsic Compression Forces.

To investigate the principles that govern ureteral stent failure by digitally and mechanically characterizing their luminal reduction in response to various extrinsic compression forces. To explore the relationship between ureteral stent "material area," "luminal area," and "cross-sectional area (CSA)" for resisting extrinsic compression forces. We mechanically investigated 4.8F (n = 9), 6F (n = 9), and 7F (n = 9) ureteral stents to determine parameters that contribute to resisting radial compression forces. Digitalized images of luminal reduction values under incrementally increased reductions of stent outer diameters were obtained (0%, 25%, 50%, and 60% of original outer diameter). Forces (Newton [N]) and percentage luminal reduction that resulted in complete ureteral stent obstruction were determined. Uniaxial incremental compression in the radial direction demonstrated complete luminal reduction (95%-100%) when 58% to 62% of the outer stent diameter was compressed. The 6F ureteral stents demonstrated the greatest resistance to extrinsic compression and the greatest "material area" relative to "CSA" (mm2). The force (N) required for 50% compression of outer stent diameter was 10.44, 28.13, and 25.39 N for 4.8F, 6F, and 7F ureteral stents, respectively. The "material area"/"CSA" at 50% compression of the outer stent diameter was 76%, 86%, and 78% for 4.8F, 6F, and 7F ureteral stents, respectively. Maintenance of intraluminal stent diameter in the presence of extrinsic compressive forces is primarily dependent on the stent's ratio of "material area" to "CSA." Urologists should be aware of these findings to decrease the risk of ureteral stent failure when treating extrinsic ureteral obstruction.

Influence of effective stress and temperature on the creep behavior of a saturated compacted clayey soil

The compacted clay barrier of shallow depth repositories for wastes would be subjected to temperature variations. Consequently, the hydro-mechanical properties of compacted clays could be progressively modified, and thus affect the performance of repositories. The influence of effective stress and temperature on the creep behavior of a saturated compacted clayey soil was experimentally investigated by performing a series of incremental loading creep tests using a temperature-controlled oedometer. Applied effective vertical stress varied from 10 to 1300 kPa within a large temperature range of 5 °C to 70 °C. The results showed that the compression and swelling indices appear not to be affected by temperature, whereas the yield stress decreases as the temperature increases. The secondary compression is time-dependent; creep strains decrease with time till reaching a stable value corresponding to a period of 10 days. The creep coefficient Cαe increases with the increase of the effective stress and temperature. Moreover, relationships between the creep coefficient Cαe, incremental compression index Cc∗, effective stress and temperature were further analyzed. A linear relationship between Cαe and Cc∗ was observed in the considered stress range and the (Cαe/Cc∗) ratio appears to be temperature dependent. Finally, the main results were discussed and interpreted in the light of a suitable constitutive framework.

Experimental procedure and simplified modeling for the high strain-rate and transient hardness evolution of aluminum AA1050

This work investigates the strain-rate influence on Vickers hardness evolution of a commercially pure aluminum (AA1050). The material hardness properties are assessed by means of laboratory tests employing quasi-static indentation tests performed on samples previously submitted to dynamic plastic compression considering a wide range of strain and strain-rate levels. Total strains of approximately 1.5 are imposed at different strain-rates, ranging from quasi-static to high strain-rate (1.1×104s−1) conditions. The experiments consist of nearly constant strain-rate incremental compressions, decremental strain-rate and strain-rate jump tests. High strain-rate tests are conducted employing a specifically designed impact testing machine. It is observed that both the material hardness and the corresponding hardening-rate increase with loading-rate. However, strain-rate effects are more pronounced at earlier deformations stages. Specific experiments with abrupt (decremental or jump) changes in strain-rate reveal the loading path influence on corresponding material hardness evolution. Specifically, short inverted transients are evidenced from decremental tests. In order to macroscopically describe the experimental material hardness behavior in terms of strain and strain-rate histories, a single scalar internal variable model is formulated. The associated model parameters are calibrated using constant strain-rate experimental data, and the model validation is performed against sequential strain-rate experiments. Overall, the model performs reasonable well within considered strain and strain-rate ranges, while remaining tractable for material identification procedure. However, the inverted transient response observed in decremental tests is not fully well captured, which is clearly a counterpart of operating with a single variable approach. Additionally, the employed methodology can be viewed as an easy-to-perform and low-cost procedure to macroscopically assess the corresponding yield stress and hardening behavior of a metallic material at high strain-rate, since expensive instrumentation and high speed data acquisition systems are not necessary. Its effectiveness will rely on the ability to formulate and calibrate constitutive or empirical correlations between the current yield stress and corresponding material hardness.