Large Compression Research Articles

Prototype Experimental Investigation of the Failure Mechanism and Crack Propagation of Segment Lining for Staggered Jointed Assembly

In order to ascertain the failure characteristics of a segment structure with distributed mortises and tenons, one should be aware of the rules of key parameters and the development of cracks during the failure process. In this paper, based on the Foguan‐Guangcheng Intercity Railway Tunnel Project, a prototype test of the structure of a segment with a staggered joint assembly was performed to study the local mechanical characteristics of the segment lining of the vault. The main conclusions were as follows: (1) The failure process in the test was classified as large eccentric compression failure, and the bearing capacity limit was M = 1993 kN m. (2) The overall displacement distribution of the segment structure was funnel‐shaped, and the failure process was divided into three stages, that is, the elastic stage, the elastoplastic stage, and the plastic stage. Thus, it is recommended that the index of the single‐point displacement limit of this tunnel be reduced appropriately to be between 1.5 and 1.8%. (3) The change rule of the longitudinal joint opening of the segment can be divided into three stages, that is, slow increase, accelerated increase, and sharp increase. For normal use, the limit of the opening of the longitudinal joint is set at 3 mm. (4) The width of the structural crack and the vertical displacement of the control section can be used as the safety evaluation index of this project. When either a large increase in the width of the crack occurs or the displacement specified above is reached, it can be considered that the structure is about to fail, and immediate protective measures must be taken.

Large negative linear compressibility of a porous molecular co-crystal.

Flexible and transformable molecules, particularly those responding to external stimuli, are needed for designing sensors and porous compounds capable of storing or separating gases and liquids. Under normal conditions the photochromic compound, 1,2-bis[2-methyl-5-(pyridyl)-3thienyl]cyclopentene (BTCP) forms a porous co-crystal with 1,4-diiodotetrafluorobenzene (dItFB). It traps acetone (Ac) molecules in the pores. Owing to a unique system of pores in the polar framework, the crystal is sensitive to the humidity in the air and to the chosen liquid environment. When compressed in non-penetrating media, the crystal displays a strong negative linear compressibility (NLC) along [100].

Large Database Compression Based on Perceived Information

Lossy compression algorithms trade bits for quality, aiming at reducing as much as possible the bitrate needed to represent the original source (or set of sources), while preserving the source quality. In this letter, we propose a novel paradigm of compression algorithms, aimed at minimizing the information loss perceived by the final user instead of the actual source quality loss, under compression rate constraints. As main contributions, we first introduce the concept of perceived information (PI), which reflects the information perceived by a given user experiencing a data collection, and which is evaluated as the volume spanned by the sources features in a personalized latent space. We then formalize the rate-PI optimization problem and propose an algorithm to solve this compression problem. Finally, we validate our algorithm against benchmark solutions with simulation results, showing the gain in taking into account users’ preferences while also maximizing the perceived information in the feature domain.

Experimental Hybrid Testing of a Concrete Filled Steel Tube (CFST) Bridge Pier Subjected to Vertical and Horizontal Ground Motions

Hybrid simulation is a form of advanced testing that combines both numerical and experimental techniques to achieve an economical seismic response assessment of structures. The technique utilises the best feature of computer simulations and combines these with experimental testing. This makes hybrid simulation a powerful platform for experimentally studying the seismic responses of structures to collapse. This paper presents an application of hybrid simulation for tracing the seismic responses of a concrete filled steel tube (CFST) column subjected to combined horizontal and vertical ground accelerations. A state-of-the-art testing facility, known as the multi axis substructure testing (MAST) system, was used to impose complex boundary effects on the physical specimen using mixed load and deformation modes. The column was subjected to five increasing ground motion levels. During the test, the column experienced large axial force variations of up to 2.2 MN and reached a maximum drift of 8.8% without significant damage. The results demonstrate that this CFST column is thus capable of resisting large compression and tension forces, offering high levels of ductility without collapse.

Biomechanics of the Sacroiliac Joint: Anatomy, Function, Biomechanics, Sexual Dimorphism, and Causes of Pain.

The sacroiliac joints (SIJs), the largest axial joints in the body, sit in between the sacrum and pelvic bones on either side. They connect the spine to the pelvis and thus facilitate load transfer from the lumbar spine to the lower extremities. The majority of low back pain (LBP) is perceived to originate from the lumbar spine; however, another likely source of LBP that is mostly overlooked is the SIJ. This study (Parts I and II) aims to evaluate the clinical and biomechanical literature to understand the anatomy, biomechanics, sexual dimorphism, and causes and mechanics of pain of the SIJ leading to conservative and surgical treatment options using instrumentation. Part II concludes with the mechanics of the devices used in minimal surgical procedures for the SIJ. A thorough review of the literature was performed to analyze studies related to normal SIJ mechanics, as well as the effects of sex and pain on SIJ mechanics. A total of 65 studies were selected related to anatomy, biomechanical function of the SIJ, and structures that surround the joints. These studies discussed the effects of various parameters, gender, and existence of common physiological disorders on the biomechanics of the SIJ. The SIJ lies between the sacrum and the ilium and connects the spine to the pelvic bones. The SIJ transfers large bending moments and compression loads to lower extremities. However, the joint does not have as much stability of its own against the shear loads but resists shear due the tight wedging of the sacrum between hip bones on either side and the band of ligaments spanning the sacrum and the hip bones. Due to these, sacrum does not exhibit much motion with respect to the ilium. The SIJ range of motion in flexion-extension is about 3°, followed by axial rotation (about 1.5°), and lateral bending (about 0.8°). The sacrum of the female pelvis is wider, more uneven, less curved, and more backward tilted, compared to the male sacrum. Moreover, women exhibit higher mobility, stresses/loads, and pelvis ligament strains compared to male SIJs. Sacroiliac pain can be due to, but not limited to, hypo- or hypermobility, extraneous compression or shearing forces, micro- or macro-fractures, soft tissue injury, inflammation, pregnancy, adjacent segment disease, leg length discrepancy, and prior lumbar fusion. These effects are well discussed in this review. This review leads to Part II, in which the literature on mechanics of the treatment options is reviewed and synthesized.

Error Resilience for Block Compressed Sensing with Multiple-Channel Transmission

Compressed sensing is well known for its superior compression performance, in existing schemes, in lossy compression. Conventional research aims to reach a larger compression ratio at the encoder, with acceptable quality reconstructed images at the decoder. This implies looking for compression performance with error-free transmission between the encoder and the decoder. Besides looking at compression performance, we applied block compressed sensing to digital images for robust transmission. For transmission over lossy channels, error propagation or data loss can be expected, and protection mechanisms for compressed sensing signals are required for guaranteed quality of the reconstructed images. We propose transmitting compressed sensing signals over multiple independent channels for robust transmission. By introducing correlations with multiple-description coding, which is an effective means for error resilient coding, errors induced in the lossy channels can effectively be alleviated. Simulation results presented the applicability and superiority of performance, depicting the effectiveness of protection of compressed sensing signals.

Experimental study of prefabricated RC column-foundation assemblies with two different connection methods and using large-diameter reinforcing bars

Prefabricated reinforced concrete (RC) column-to-foundation connections are typically located at the critical region of the columns and are subjected to a combination of large compression and bending deformation under earthquake actions. The seismic behaviour of these connections affects the structural behaviour of precast concrete frames as a whole. The prefabricated column-to-foundation connections using grouted sleeves (PC-S) and grouted corrugated ducts (PC-C) were two typical connections. However, up to now the researches on the seismic performance of the two typical connections are mainly concentrated on small-diameter reinforcing bars used in the connections. The use of large-diameter high-strength reinforcing bars in the large size precast columns has clear advantages in precast structures as it helps improve the construction efficiency due to a reduced number of connected longitudinal bars and less congestion of the reinforcing bars. In this study, two full-scale prefabricated column-foundation assemblies with different connection methods, designated as PC-S and PC-C, respectively, along with one cast-in-place reference specimen, were prepared and tested under quasi-static cyclic loading. In all three specimens, large-diameter high-strength reinforcing bars were adopted as the longitudinal reinforcing bars. The test results showed that both types of connections exhibited similar strength as compared to the cast-in-place specimen. In specimen PC-S, buckling of the longitudinal bars and rupture of stirrups at the top of the grouted sleeves were observed, and this led to lower ductility with an ultimate lateral drift ratio of 4.5%. In specimen PC-C, a more pronounced pinching behaviour was observed after a lateral drift ratio of 2%, which was due to significant bond-slip displacements of large-diameter high-strength longitudinal bars in the overlap region. The three specimens exhibited different plastic hinge mechanisms at the column bases as demonstrated from the measured steel strains, cracking patterns and failure modes. Based on the experimental results, further improvements of using large-diameter high-strength reinforcing bars in the two types of prefabricated column-to-foundation connections are recommended.

A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O

Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies that have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit–cell parameters as well as on the bond and polyhedral compressibility. A Birch–Murnaghan equation of state has been fitted to the unit–cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42–49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies experimentally determined is also reported.

The image-based multiscale multigrid solver, preconditioner, and reduced order model

We present a novel image-based multiscale multigrid solver that can efficiently address the computational complexity associated with highly heterogeneous systems. This solver is developed based on an image-based, multiresolution model that enables reliable data flow between corresponding computational grids and provides large data compression. A set of inter-grid operators is constructed based on the microstructural data which remedies the issue of missing coarse grid information. Moreover, we develop an image-based multiscale preconditioner from the multiscale coarse images which does not traverse through any intermediate grid levels and thus leads to a faster solution process. Finally, an image-based reduced order model is designed by prolongating the coarse-scale solution to approximate the fine-scale one with improved accuracy. The numerical robustness and efficiency of this image-based computational framework is demonstrated on a two-dimensional example with high degrees of data heterogeneity and geometrical complexity.

Sketch distance-based clustering of chromosomes for large genome database compression

BackgroundThe rapid development of Next-Generation Sequencing technologies enables sequencing genomes with low cost. The dramatically increasing amount of sequencing data raised crucial needs for efficient compression algorithms. Reference-based compression algorithms have exhibited outstanding performance on compressing single genomes. However, for the more challenging and more useful problem of compressing a large collection of n genomes, straightforward application of these reference-based algorithms suffers a series of issues such as difficult reference selection and remarkable performance variation.ResultsWe propose an efficient clustering-based reference selection algorithm for reference-based compression within separate clusters of the n genomes. This method clusters the genomes into subsets of highly similar genomes using MinHash sketch distance, and uses the centroid sequence of each cluster as the reference genome for an outstanding reference-based compression of the remaining genomes in each cluster. A final reference is then selected from these reference genomes for the compression of the remaining reference genomes. Our method significantly improved the performance of the-state-of-art compression algorithms on large-scale human and rice genome databases containing thousands of genome sequences. The compression ratio gain can reach up to 20-30% in most cases for the datasets from NCBI, the 1000 Human Genomes Project and the 3000 Rice Genomes Project. The best improvement boosts the performance from 351.74 compression folds to 443.51 folds.ConclusionsThe compression ratio of reference-based compression on large scale genome datasets can be improved via reference selection by applying appropriate data preprocessing and clustering methods. Our algorithm provides an efficient way to compress large genome database.

Explicit nonlinear and plastic analysis model of steel–concrete–steel sandwich panels

This paper presents an explicit nonlinear and plastic analysis model (ENPAM) for steel–concrete–steel (SCS) panels. This model considers the behavior of concrete under biaxial stresses and the post-yield stress-strain relationship of steel plates. A simplified measure is utilized for the simulation of concrete. The elastic–plastic stiffness of steel plates is derived from the Prandtl–Reuss model. ENPAM fully embodies the stress redistribution during the plastic flow after steel plate yielding. The model's effectiveness is demonstrated based on comparisons with experimental data obtained for SCS panels subjected to pure shear and shear with a small compression. A finite element model is also established to verify the effectiveness of ENPAM for the load cases of shear with large compression.

Effects of sucrose, glucose and fructose on the large deformation behaviors of fish skin gelatin gels

Fish gelatin extracted from tilapia (Oreochromis niloticus) skins was used to investigate the large deformation behaviors of gelatin gels (2, 4 and 6.67 g/100 g H2O) under uniaxial compression as affected by sugars (0, 5, 10, 15 and 20 g/100 g H2O) including sucrose, glucose and fructose. The first order Ogden model was applied to understand the mathematical relationship between the true stress and true strain of tilapia skin gelatin (TSG) gels under large compression deformation (stretch ratio λ = 0.35–1). The results indicated that the addition of sucrose, glucose or fructose in a TSG gel led to a decrease in the gel strength, but the extent of this gel-weakening effect depended on the types and concentrations of sugar. The first order Ogden models fitted very well with the compression responses of TSG gels with or without sugar (R2 = 0.9949–0.9998). Significant difference (p < 0.05) in the initial shear modulus (μ) and/or the Ogden constant were found among TSG gels with a specific gelatin concentration but different levels of a sugar. The reduction of the μ value was as much as 11–22% for TSG-sugar gels compared to the corresponding gels without sugar. There were power law relationships between the μ values and gelatin concentrations (μ∝c1.49−1.65) for TSG-sugar gels. This study showed the great fit of the Ogden model for the large deformation responses of gelatin gels and the gel-weakening effects of sugars, which is of significant importance from both theoretical and application aspects.

Effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled TRIP steel

The scanning electron microscope, transmission electron microscope, optical microscope, X-ray diffraction and hardness tests were used to investigate the effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled transformation-induced plasticity steel. The thermomechanical-controlled processing was carried out with thermomechanical simulation machine, and the samples were compressed to compression strains of 0, 0.15, 0.25 and 0.35 at compression temperatures of 850, 900 and 950 °C. The results showed that the volume fraction of polygonal ferrite increased with the increasing compression strain, while the volume fraction of retained austenite reached the maximum value at compression strain of 0.25. The volume fraction of polygonal ferrite decreased with the increasing compression temperature, whereas the volume fraction of retained austenite possessed the maximum value at compression temperature of 850 °C. Some granular retained austenite was present in uncompressed samples, and some pearlite appeared at large compression strain, while the hardness of the samples exhibited the similar variation tendency to the volume fraction of retained austenite.

Experimental study of the impedance behavior of 18650 lithium-ion battery cells under deforming mechanical abuse

Due to rising safety requirements for lithium-ion batteries, the detection of mechanical failure of such batteries is becoming increasingly important. As publications investigating electrochemical impedance spectroscopy (EIS) of lithium-ion battery cells under deforming mechanical abuse as a potential damage detection method are sparse, this work presents tests with stepwise loading of 18,650 lithium-ion battery cells with various impactors (nails, cylindric, hemispheric) and simultaneous EIS measurements to search for indicators which could be used to anticipate hazardous events. The occurrence of different damage mechanisms of the jelly roll is evaluated via computed tomography (µ-CT) and correlated to the measured changes in EIS. For internal short circuits (ISCs) without instantaneous thermal runaway, the results show a decrease of ohmic resistance in the EIS for high measurement frequencies, which is possibly linked to temperature increase, while low frequencies indicate deviations from stationarity or linearity requirements. In the case of large area compression, the EIS measurements display an increase of ohmic resistance, which may be connected to various mechanisms, such as the decrease of porosity of the separator and the active materials or delamination.

Acoustic sound speed profile inversion based on orthogonal matching pursuit

The estimation of ocean sound speed profiles (SSPs) requires the inversion of an acoustic field using limited observations. Such inverse problems are underdetermined, and require regularization to ensure physically realistic solutions. The empirical orthonormal function (EOF) is capable of a very large compression of the data set. In this paper, the non-linear response of the sound pressure to SSP is linearized using a first order Taylor expansion, and the pressure is expanded in a sparse domain using EOFs. Since the parameters of the inverse model are sparse, compressive sensing (CS) can help solve such underdetermined problems accurately, efficiently, and with enhanced resolution. Here, the orthogonal matching pursuit (OMP) is used to estimate range-independent acoustic SSPs using the simulated acoustic field. The superior resolution of OMP is demonstrated with the SSP data from the South China Sea experiment. By shortening the duration of the training set, the temporal correlation between EOF and test sets is enhanced, and the accuracy of sound velocity inversion is improved. The SSP estimation error versus depth is calculated, and the 99% confidence interval of error is within ±0.6 m/s. The 82% of mean absolute error (MAE) is less than 1 m/s. It is shown that SSPs can be well estimated using OMP.

Study on mechanics damage mechanism of arch surround reinforced structure under loose load

Lining crack is a typical disease of highway tunnels in operation, which affects the long-term operation safety of tunnels. The arch surround is suitable for strengthening tunnel projects with serious cracks due to its characteristics of significantly increasing structural bearing capacity and prolonging service life. However, at present, the damage evolution mechanism of arch surround reinforcement structures under loose loads based on the secondary stress mode is not well understood. Aiming at the above problems, in this paper, based on the load structure method, indoor 1:10 model test of arch surround reinforcement for Grade VI surrounding rock and damaged lining structure is carried out and the stress and deformation law, failure mode and ultimate bearing capacity of tunnel after arch surround reinforcement is explored. On this basis, finite element software is used to simulate the whole process of damage evolution of arch surround reinforced the structure, and to explore the mechanism of mechanical damage evolution of arch surround structure after reinforcement. The results show that the arch surround reinforcement can effectively repair the damaged tunnel and greatly improve its bearing capacity. When the residual bearing capacity of lining is 48.4%, the bearing capacity is increased by 164%. The original structure of the second lining and the reinforced structure of the arch surround are both in large eccentric compression failure. The main damaged parts are the vault and the haunch. The failure of the reinforcing structure of the arch surround is caused by the slip cracking of the combined surface between the second lining and the arch surround. Anchor bolts should be added to improve the shear bearing capacity of the combined surface.

Compressive behavior and energy absorption of polymeric lattice structures made by additive manufacturing

Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat dissipation. In this work, by combining experimental and numerical methods, we investigate the compressive behavior and energy absorption of lattices made through the stereolithography apparatus process. Four types of lattice structures are considered: (i) Uniform body-centered-cubic (U-BCC); (ii) graded body-centered-cubic (G-BCC); (iii) uniform body-centered-cubic with z-axis reinforcement (U-BCCz); and (iv) graded body-centered-cubic with z-axis reinforcement (G-BCCz). We conduct compressive tests on these four lattices and numerically simulate the compression process through the finite element method. Analysis results show that BCCz has higher modulus and strength than BCC. In addition, uniform lattices show better energy absorption capabilities at small compression distances, while graded lattices absorb more energy at large compression distances. The good correlation between the simulation results and the experimental phenomena demonstrates the validity and accuracy of the present investigation method.

Absence of Interlayer Tunnel Coupling of K-Valley Electrons in Bilayer MoS_{2}.

In Bernal stacked bilayer graphene interlayer coupling significantly affects the electronic band structure compared to monolayer graphene. Here we present magnetotransport experiments on high-quality n-doped bilayer MoS_{2}. By measuring the evolution of the Landau levels as a function of electron density and applied magnetic field we are able to investigate the occupation of conduction band states, the interlayer coupling in pristine bilayer MoS_{2}, and how these effects are governed by electron-electron interactions. We find that the two layers of the bilayer MoS_{2} behave as two independent electronic systems where a twofold Landau level's degeneracy is observed for each MoS_{2} layer. At the onset of the population of the bottom MoS_{2} layer we observe a large negative compressibility caused by the exchange interaction. These observations, enabled by the high electronic quality of our samples, demonstrate weak interlayer tunnel coupling but strong interlayer electrostatic coupling in pristine bilayer MoS_{2}. The conclusions from the experiments may be relevant also to other transition metal dichalcogenide materials.

Two-channel depth encoding for 3D range geometry compression.

This paper presents a novel method for accurately encoding 3D range geometry within only two channels of a 2D RGB image using a two-frequency phase-shifting approach. Once encoded within a 2D image, 3D geometry can be further compressed with conventional lossless or lossy image compression methods. The nature of the proposed two-channel encoding is relatively smooth; thus, large compression ratios with high reconstruction accuracies can be achieved and are experimentally demonstrated. For example, a compression ratio of 2883:1 was achieved, compared with the STL format, with a reconstruction RMS error of 0.45mm (99.8% accuracy) when JPEG 85 was used with the proposed method. This paper also demonstrates how a 24-bit color texture map can be encoded alongside 3D geometry within a single 2D image.

Reinforced high-strength engineered cementitious composite (ECC) columns under eccentric compression: Experiment and theoretical model

Engineered cementitious composites (ECC) with a tensile rupture strain larger than 3%, has won itself wide attention at the material level. To further investigate its performance at the structural component level, a series of reinforced ECC (R/ECC) columns with the cross-section dimensions of 120 mm × 120 mm were tested under large eccentric compressive loading at the eccentricity of 80 mm. One reinforced concrete (RC) column was also fabricated for reference. The compressive strengths of both ECC and concrete were controlled at 60 MPa. The displacement at half height point, the strains of longitudinal bars and the crack patterns of columns were monitored. The experimental results showed that the peak load of the plain ECC column approached 50% of the value of the RC column with a reinforcement ratio of 4.3% (RC-4.3%). The peak load of R/ECC column was found to gain an increase of 35.2% compared to the RC column with the same reinforcement ratio. The multiple-crack patterns were fully developed along the height of the column. An analytical model was proposed for the load-bearing capacity of R/ECC columns under large eccentric compression, and was validated by the experimental results. Finally, parametric analyses showed that the peak load of plain ECC-90 column (i.e., compressive strength = 90 MPa) was similar to the value of RC-4.3%, while the peak load of plain ECC-120 column (i.e., compressive strength = 120 MPa) exceeded that of RC column, implying that high-strength ECC could be applied to completely replace the steel bars in columns.