Large-scale Compression Research Articles

Large-scale hyperspectral image compression via sparse representations based on online learning

Abstract In this study, proximity based optimization algorithms are used for lossy compression of hyperspectral images that are inherently large scale. This is the first time that such proximity based optimization algorithms are implemented with an online dictionary learning method. Compression performances are compared with the one obtained by various sparse representation algorithms. As a result, proximity based optimization algorithms are listed among the three best ones in terms of compression performance values for all hyperspectral images. Additionally, the applicability of anomaly detection is tested on the reconstructed images.

Simulated Test on Compression Deformation Characteristics and Mechanism of Fractured Rock in Mined Out Area

In order to study the whole compression process deformation characteristics, the compression test of fractured rock in goaf was carried out by using the large-scale compression deformation seepage experiment system of fractured rock. Through the Taibo theory, the particle size gradation of the fractured rock mass was determined as n is 0.5. Loaded prepared dry fractured rock into the experimental cabin, and carried out the short-time creep test for 2.5 h at different gradients in a graded loading manner. After level 5 gradient loading for 1.25 h, carried out the long-term creep test under immersion condition. After the creep test, additional stress was added and the additional deformation was observed. The results show that the fractured rock compaction process includes initial compaction, crushing compaction; under the influence of load gradient and water, the fractured rock compaction process has accelerated deformation, which threatens the goaf stability; under creep condition, compaction deformation shows logarithmic growth, slows down gradually and tends to be stable; After fractured rock in the mined out area is stabilized by compaction, it is still possible to be activated under the influence of building load.

Study of Compressive Deformation Tests on Vegetation-recovery Earthbags

Vegetation-recovery earthbags have good adaptability to deformation. Uniaxial cyclic compression test and large-scale triaxial compression test are designed for the bags used in the Three Gorges Reservoir, where the water level fluctuates periodically greatly. The results show the stress-strain curves have a strainhardening tendency, which means the vegetation-recovery earthbags have good resistance to vertical deformation. The deformation modulus of the earthbags in first compression is much less than the compression modulus of the fillings. But after cyclic compression, the deformation modulus of the earthbags approaches to the compression modulus of the fillings, and so does the deformation modulus of the earthbags under confining pressure. So it is advised that the compressive modulus of the fillings can be used for calculating the surface settlement of the structures made of vegetation-recovery earthbags under great hydraulic pressure in the later period; and it would be better to construct in stages, temporary safe measures should be taken; and after the greatest hydraulic pressure in one period, proper methods should be taken for anchoring the surface and the basement of the earthbags structure.

The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Survey Overview and Results of an Exemplar Source, PGCC G26.53+0.17

The low dust temperatures (<14 K) of Planck Galactic Cold Clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase of star formation. TOP-SCOPE is a joint survey program targeting ~2000 PGCCs in J=1-0 transitions of CO isotopologues and ~1000 PGCCs in 850 micron continuum emisison. The objective of the TOP-SCOPE survey and the joint surveys (SMT 10-m, KVN 21-m and NRO 45-m) is to statistically study the initial conditions occurring during star formation and the evolution of molecular clouds, across a wide range of environments. The observations, data analysis and example science cases for these surveys are introduced with an exemplar source, PGCC G26.53+0.17 (G26), which is a filamentary infrared dark cloud (IRDC). The total mass, the length and the mean line-mass (M/L) of the G26 filament are ~6200 Msun, ~12 pc and ~500 Msun/pc, respectively. Ten massive clumps including eight starless ones are found along the filament. The most massive Clump as a whole may be still in global collapse while its denser part seems to be undergoing expansion due to outflow feedback. The fragmentation in G26 filament from cloud scale to clump scale is in agreement with gravitational fragmentation of an isothermal, non-magnetized, and turbulent supported cylinder. A bimodal behavior in dust emissivity spectral index ($\beta$) distribution is found in G26, suggesting grain growth along the filament. The G26 filament may be formed due to large-scale compression flows evidenced by the temperature and velocity gradients across its natal cloud.

A Widespread, Clumpy Starburst in the Isolated Ongoing Dwarf Galaxy Merger dm1647+21

Abstract Interactions between pairs of isolated dwarf galaxies provide a critical window into low-mass hierarchical, gas-dominated galaxy assembly and the build-up of stellar mass in low-metallicity systems. We present the first Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT/MUSE) optical integral field unit (IFU) observations of the interacting dwarf pair dm1647+21 selected from the TiNy Titans survey. The Hα emission is widespread and corresponds to a total unobscured star formation rate (SFR) of 0.44 M ⊙ yr−1, which is 2.7 times higher than the SFR inferred from Sloan Digital Sky Survey (SDSS) data. The implied specific SFR (sSFR) for the system is elevated by more than an order of magnitude above non-interacting dwarfs in the same mass range. This increase is dominated by the lower-mass galaxy, which has a sSFR enhancement of &gt;50. Examining the spatially resolved maps of classic optical line diagnostics, we find that the interstellar medium (ISM) excitation can be fully explained by star formation. The velocity field of the ionized gas is not consistent with simple rotation. Dynamical simulations indicate that the irregular velocity field and the stellar structure is consistent with the identification of this system as an ongoing interaction between two dwarf galaxies. The widespread, clumpy enhancements in the star formation in this system point to important differences in the effect of mergers on dwarf galaxies, compared to massive galaxies; rather than the funneling of gas to the nucleus and giving rise to a nuclear starburst, starbursts in low-mass galaxy mergers may be triggered by large-scale ISM compression, and thus may be more distributed.

Large-scale and structure-tunable laser spectral compression in an optical dispersion-increasing fiber.

Laser spectral compression by a factor of 102.8 is experimentally achieved through optical soliton propagation in a dispersion-increasing fiber. By varying the input pulse energy, the wavelength tuning range of the compressed spectral peak could exceed 115 nm. Spectrally compressed spectrum with two bright peaks is demonstrated for the first time, to our knowledge. The structure of the dual-peaked compressed spectra is adjustable through the interplay of initial pulse chirp and energy. All of the experimental data are compared to numerical results and are found in good agreement.

Sustainable Application of Unbound Quarry Byproducts in Pavement Construction through Aggregate Gradation Optimization

Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performance. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for blending and mixing proportions of fine granite tailings (FGT), a typical crushed granite mining byproduct that has long been considered “waste” materials, and coarse crushed granite aggregates (CCGA). To this goal, one of the common quarry byproduct wastes (i.e., FGT), was mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress-strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective longlife pavements.

Laboratory validation of a gradation design concept for sustainable applications of unbound granular materials in pavement construction

Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performances. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for two applications: (1) unbound permeable aggregate base (UPAB) and (2) mixing proportions of blending fine granite tailings (FGT), a typical crushed granite mining by-product that has long been considered “waste” materials, with coarse crushed granite aggregates (CCGA). To this goal, five representative gradations were first selected according to the current Minnesota DOT UPAB gradation band, and the effects of different UPAB gradation designs on the shear strength properties and particle breakage potential were investigated using a large-scale direct shear test device. In the second application, one of the common quarry byproduct wastes (i.e., FGT), were mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Both laboratory permeability and large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress–strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective long-life pavements.

Conceptual Cluster-based Large-scale Ontology Compression Approach

With the development of semantic web and ontology application, there is a large number of ontology whose scale is large and the structure is complex in different fields. The existing mapping method and mapping system perform well when dealing with the mapping between a lightweight small ontology. However, when comes to the large-scale ontology, it is full of challenges to the methods and systems。To this end, this paper proposes a method of ontology compression based on conceptual cluster to compress. Firstly, it calculates the semantic similarity and semantic correlation of ontology concepts with the DICE coefficient method and the information entropy technology to get semantic relation. Secondly according to the semantic relations, it carries on the conceptual cluster in the space so that the of semantic relations closely together in groups. The of cluster in space is reduced, and the noise concept which is independent of the mapping is removed, and the purpose of the large-scale ontology compression is realized. Experimental results show that the method is so effective that it can compress the volume of large-scale ontology in the mapping problems.

Socioeconomic potential for introducing large-scale heat pumps in district heating in Denmark

Denmark has a national political goal of a 100% renewable energy supply in 2050. This requires a comprehensive transition of the energy system. For some decades, district heating in Denmark has been contributing to high fuel efficiency as well as to the integration of the electricity and heating sectors. Large-scale compression heat pumps would improve the integration between the district heating and power sectors by utilising the fluctuations in the supply from wind power, solar photo voltaic and other sources. Previous studies indicate that the introduction of heat pumps in Denmark will have a positive impact on the total costs for energy supply in the transition towards 100% renewable energy. In this paper, this is further investigated to assess the feasibility of heat pumps in the Danish energy system. The assessment is made by applying two different energy system analysis tools, named EnergyPLAN and MODEST. The comparison and discussion of these tools is a secondary purpose of the study. In general, the results show a potential for introducing heat pumps in Denmark between 2 and 4 GW-thermal power and a total potential benefit around 100 M€/year in 2025.

Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTéMiS

Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which ~ 0.1 pc-wide filaments form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because Herschel data cannot resolve the inner width of filaments in the nearest regions of massive star formation. We used the bolometer camera ArTeMiS on the APEX telescope to map the central part of the NGC6334 complex at a factor of > 3 higher resolution than Herschel at 350 microns. Combining ArTeMiS data with Herschel data allowed us to study the structure of the main filament of the complex with a resolution of 8" or < 0.07 pc at d ~ 1.7 kpc. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~ 500 Msun/pc to ~ 2000 Msun/pc over nearly 10 pc. It also demonstrates that its inner width remains as narrow as W ~ 0.15 +- 0.05 pc all along the filament length, within a factor of < 2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. While it is not completely clear whether the NGC 6334 filament will form massive stars or not in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and yet has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star forming regions.

Mesozoic tectonic and topographic evolution of Central Asia and Tibet: a preliminary synthesis

Abstract During the Late Palaeozoic–Mesozoic, Central Asia and Tibet were affected by several geodynamic episodes that induced either large-scale compression or widespread extension. The Late Palaeozoic final amalgamation of the Central Asian Orogenic Belt, the accretion of the Cimmerian blocks, the closure of the Mongol–Okhotsk Ocean and the accretion of the Neocimmerian blocks set the structural pattern of the continent. This Mesozoic tectonic heritage plays a first-order role in the localization and evolution of the Tertiary deformation of the continent. Similarly, large-scale Mesozoic topographic features are still preserved in Central Asia, where they form a non-negligible part of the present-day topography. This work aims at providing an overview of the major tectonic events that affected Central Asia and Tibet during the Late Palaeozoic and Mesozoic periods. The general topographic evolution of the continent is also described together with the accompanying climatic changes through time.

Influence of Particle Breakage on Critical State Line of Rockfill Material

AbstractThe influences of particle breakage on the position of the critical state line (CSL) were systematically investigated in this paper through a series of large-scale triaxial compression tests on Tacheng rockfill material (TRM). It was found that the critical-state stress ratio of TRM (i.e., the gradient of the CSL in the p−q space) was approximately regarded as a constant. In the e−logp space, the CSL of TRM descended with a decrease in the initial void ratio, whereas the gradient of the CSL was constant. A procedure was established for evaluating the critical state point at a same particle breakage, which comprised the breakage critical state line (BCSL). An increase of the particle breakage led to not only a vertical translation but also a rotation on the BCSL of TRM in the e−logp space, which was similar to the observation of Dog’s Bay sand. Consequently, the initial gradation (or the corresponding initial void ratio) was the dominant factor that affected the position of the CSL of TRM in the e−...

On the compressibility of tire-derived aggregate: comparison of results from laboratory and field tests

Compression behavior of tire-derived aggregate (TDA) was investigated through relatively small-scale and large-scale laboratory one-dimensional compression tests, as well as a full-scale field test. Two types of TDA produced from passenger and light truck tire (PLTT) and off-the-road (OTR) tire were tested. The influence of initial void ratio (e0), particle size, tire source, and testing method on the compression behavior of TDA was investigated. The results indicated that the compressibility of TDA was primarily dominated by its e0. OTR yielded lower e0 than PLTT with similar particle size and the same compaction method. TDA in the field was pre-compressed by self-weight, resulting in lower e0 and compressibility compared with laboratory samples. At relatively high stress levels, all TDA exhibited similar void ratio–stress curves regardless of e0, particle size, tire source or testing method. High e0, small particle size, and granular particle shape facilitated the sliding and rolling of TDA particles, resulting in high plastic strain. The elastic deformation of TDA, reflecting the elastic behavior of tire rubber, was primarily dominated by the average contact area ratio of the TDA particles, depending mainly on the sample void ratio.

Simulation of large-scale deformation of ultra-soft peaty ground under test embankment loading and investigation of effective countermeasures against residual settlement and failure

The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N-values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale settlement in excess of 11m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil–water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing residual settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against residual settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

ELECTRON HEATING BY THE ION CYCLOTRON INSTABILITY IN COLLISIONLESS ACCRETION FLOWS. I. COMPRESSION-DRIVEN INSTABILITIES AND THE ELECTRON HEATING MECHANISM

In systems accreting well below the Eddington rate, the plasma in the innermost regions of the disk is collisionless and two-temperature, with the ions hotter than the electrons. Yet, whether a collisionless faster-than-Coulomb energy transfer mechanism exists in two-temperature accretion flows is still an open question. We study the physics of electron heating during the growth of ion velocity-space instabilities, by means of multi-dimensional particle-in-cell (PIC) simulations. A large-scale compression - embedded in a novel form of the PIC equations - continuously amplifies the field. This constantly drives a pressure anisotropy P_perp > P_parallel, due to the adiabatic invariance of the particle magnetic moments. We find that, for ion plasma beta values beta_i ~ 5-30 appropriate for the midplane of low-luminosity accretion flows, mirror modes dominate if the electron-to-proton temperature ratio is > 0.2, whereas if it is < 0.2 the ion cyclotron instability triggers the growth of strong Alfven-like waves, that pitch-angle scatter the ions to maintain marginal stability. We develop an analytical model of electron heating during the growth of the ion cyclotron instability, which we validate with PIC simulations. We find that for cold electrons (beta_e < m_e/m_i), the electron energy gain is controlled by the magnitude of the E-cross-B velocity induced by the ion cyclotron waves. This term is independent of the initial electron temperature, so it provides a solid energy floor even for electrons starting with extremely low temperatures. On the other hand, the electron energy gain for beta_e > m_e/m_i - governed by the conservation of the magnetic moment in the growing fields of the instability - is proportional to the initial electron temperature. Our results have implications for two-temperature accretion flows as well as the solar wind and intracluster plasmas. [abridged]

Strength and Deformation of Rockfill Material Based on Large-Scale Triaxial Compression Tests. I: Influences of Density and Pressure

AbstractA series of large-scale triaxial compression tests were conducted to investigate the strength and deformation behaviors of Tacheng rockfill material (TRM) in relation to the initial void ratio and initial confining pressure. The critical state friction angle of TRM was expressed as a linear function of the logarithm of the initial confining pressure. The excess peak state friction angle and excess characteristic state friction angle of TRM were formulated as linear equations of a revised relative dilatancy index to capture the influences of density and pressure on the peak state and characteristic state friction angles. The initial elastic modulus, tangent modulus, and secant modulus of TRM were dependent on the initial void ratio and initial confining pressure. In addition, a formulation incorporating density and pressure was proposed to simulate the initial elastic modulus of TRM. The volumetric and deviatoric strains of TRM at the critical state were also dependent on density and pressure. The ...

Strength and Deformation of Rockfill Material Based on Large-Scale Triaxial Compression Tests. II: Influence of Particle Breakage

AbstractThe amount of particle breakage of Tacheng rockfill material (TRM) in the process of shearing was quantitatively measured by a relative breakage index. The fractal dimension of TRM at the final state of the tests was found to be linearly related to the void ratio and logarithm of the confining pressure. The influences of the relative breakage index on the friction angle, modulus, and deformation were investigated based on a series of large-scale triaxial compression tests on TRM. An increase in the relative breakage index leads to an increase in the volumetric strain and to decreases in the peak state friction angle, critical state friction angle, deviatoric strain, and critical state void ratio. The test results were used to propose simple formulations pertaining to the relative breakage index for the strength and deformation indexes (e.g., peak state friction angle, critical state friction angle, initial elastic modulus, secant modulus at 50% of the peak strength, volumetric strain, deviatoric s...

Behavior of geogrid–reinforced sand and effect of reinforcement anchorage in large-scale plane strain compression

This paper presents experimental investigations on the behavior of geogrid–reinforced sand featuring reinforcement anchorage which simulates the reinforcement connected to the wall facings in numerous in-situ situations. A series of large plane strain compression tests (the specimen 56 cm high × 56 cm wide × 45 cm long) was conducted. Standard Ottawa sand and 4 types of PET geogrids exhibiting 5% stiffness in the range of 750–1700 kN/m were used in this study. The specimens were tested by varying the relative density of sand, confining pressures, geogrid types, and reinforcement-anchorage conditions. Experimental results indicate that relative to unreinforced specimens, both anchored and non-anchored geogrid reinforcements can enhance the peak shear strength and suppress the volumetric dilation of reinforced soil. The studies on anchorage revealed that anchoring the reinforcement can restrain the lateral expansion of reinforced specimens, resulting in a substantial increase in shear strength and a reduction in volumetric dilation. The strength ratios of non-anchored specimens appeared to be insensitive to the reinforcement stiffness, whereas the strength ratios of the anchored specimens increased markedly with increases in soil density, reinforcement stiffness, and system deformation (i.e., axial stain). Geogrid anchorage contributed a large percentage of the total shear-strength improvement, nearly 3-times more than the contribution of the soil–geogrid interaction in non-anchored specimens. Lastly, an analytical model was developed based on the concept that additional confinement is induced by reinforcement anchorage, and the predicted shear strength of the anchored soil was verified based on the experimental data.

A constitutive model for the state-dependent behaviors of rockfill material considering particle breakage

The particle breakage during specimen compaction had more significant influence on the position of the breakage critical-state line (BCSL) of Tacheng rockfill material (TRM) in the e-lnp′ plane than the particle breakage during shearing, based on the large-scale triaxial compression tests on TRM in a wide range of densities and pressures. The state-dependent dilatancy and the plastic modulus were correlated to the breakage index, based on the formulations of the BCSL of TRM in the e-lnp′ plane. The state-dependent model considering particle breakage was proposed for TRM within the framework of the generalized plasticity theory. The proposed model contained fourteen material constants. The test data of TRM from Group A were adopted to determine these material constants, while the test data from Group B were used independently to validate the model predictive capacity. The comparisons between model simulations and test data illustrated that the model with consideration of particle breakage could well represent the stress-strain behaviors of TRM, e.g., the strain hardening and volumetric contraction behaviors at a loose state and the strain softening and volumetric expansion behaviors at a dense state, and also the particle breakage behaviors of TRM.