Compression Process Research Articles

Sensory or Intelligence Data Compression Can Drive the Yerkes–Dodson Effect

New probability models of inherently embodied cognition derived from the asymptotic limit theorems of information and control theories show, where the Weber–Fechner, Stevens, Hick–Hyman, and Pieron’s psychophysics laws—and analogous processes of sensory data rate compression—operate, that sufficient arousal will engender the classic Yerkes–Dodson effect responses for ‘easy’ and ‘difficult’ challenges, depending on the level of ‘noise’ impeding the cognition rate. A ‘hallucination’ mode is found to arise at low arousal, and, in the face of sufficient noise, a ‘panic’ mode at high arousal. Systems that are ‘ductile’ in a formal sense, however, are not afflicted by such hallucination, although panic remains for difficult challenges. Similar dynamics that surround organized conflict on ‘Clausewitz landscapes’ of fog, friction, and deadly adversarial intent have long been studied. We find a central mechanism for cognitive failure under increasing stress across a very broad range of modalities to be enough—usually badly needed—compression of sensory/intelligence and internal information transmission rates. It seems possible, with some effort, to convert the probability models developed here into robust statistical tools for the study and limited control of critical real-time, real-world embodied cognitive phenomena associated with cellular, neural, individual, machine, and institutional systems and their many composites.

Identification of Dynamic Recrystallization Model Parameters for 40CrMnMoA Alloy Steel Using the Inverse Optimization Method

The microstructure of 40CrMnMoA during hot forging determines its macroscopic mechanical properties. Dynamic recrystallization (DRX) behavior is commonly used to refine grains and improve the microstructure of materials; therefore, it is important to be able to predict mechanical behavior during hot forging and the microstructure evolution during dynamic recrystallization. In order to accurately determine the DRX model parameters of 40CrMnMoA steel, an inverse optimization method is proposed in this work. The uniaxial isothermal compression experiment of 40CrMnMoA steel was carried out on a Gleeble-1500D thermal simulation tester (Dynamic Systems Inc. (DSI), Poestenkill, NY, USA) under the temperature range of 900~1200 °C and the strain rate range of 0.005 to 5 s−1. Based on the true stress–strain data obtained by a compression test, the DRX model of 40CrMnMoA was initially established using the traditional averaging method. Subsequently, the DRX model parameters calculated by the conventional averaging method were used as the initial values, the mean-square error between the experimental and calculated values of the DRX volume fraction was set as the objective function, and the DRX model parameters were optimized by the adaptive simulated annealing (ASA) algorithm. By comparing the correlation coefficient R, average absolute relative error (AARE), and the root mean square error (RMSE) of the predicted DRX percentage with the experimental values before and after optimization, it was found that the optimized model achieved an R-value of 0.992, with AARE and RMSE decreased by 34% and 2%, respectively, which verified the accuracy of the optimized DRX model. Through the program’s secondary development, the optimized DRX model of 40CrMnMoA was integrated into finite element software Forge® 3.2 to simulate the isothermal compression process. The comparison between grain size from the central region of simulation results and actual samples revealed that the relative error is less than 3%. This result demonstrated that the inverse optimization method can accurately identify the DRX model parameters of 40CrMnMoA alloy steel.

Well defined phase boundaries and superconductivity with high Tc in PbSe single crystal

Abstract Lead chalcogenides represent a significant class of materials that exhibit intriguing physical phenomena, including remarkable thermoelectric properties and superconductivity. In this study, we present a comprehensive investigation on the superconductivity of PbSe single crystal under high pressure. The signature of superconducting (SC) transition starts to appear at 7.2 K at 16.5 GPa. Upon further compression, the SC temperature (Tc ) decreases, and it is reduced to 3.5 K at 45.0 GPa. The negative pressure dependent behavior of Tc is consistent with the trend of Tc - P relations observed in other lead chalcogenides. The highest Tc is 8.0 K observed at 20.5 GPa during decompression process, which is also the highest record among all other PbSe derivatives, such as doped samples, superlattices, and so on. The phase boundaries of the structural and electronic transitions are well defined by Raman spectroscopy, and then phase diagrams are plotted for both compression and decompression processes. This work corrects the previous claim of positive pressure dependence of Tc in PbSe and provides clear phase diagrams for intrinsic superconductivity in PbSe under pressure.

A Study on the Nonlinear Characteristics of Hydro-Pneumatic Suspension Systems for Mining Dump Trucks

In the current study, nonlinear characteristics of Hydro-Pneumatic Suspension (HPS) systems for mining dump trucks are proposed and analyzed for the ride comfort of off-highway vehicles. To analyze these characteristics, a mathematical HPS model was used to determine the vertical elastic and damping forces. Then, a two-degrees-of-freedom (2-DOF) quarter-vehicle dynamic model of a mining dump truck was proposed to analyze the nonlinear characteristics of the HPS systems implemented in a MATLAB/Simulink environment under low-frequency excitations of road surfaces. An experiment was set up to measure the vibration accelerations at the upper and lower positions of the HPS systems to verify the proposed HPS mathematical model. The experimental and simulation results demonstrated that both the time- and frequency-domain accelerations were consistent with the laws of physics and exhibited errors within acceptable ranges, thereby demonstrating the reliability of the proposed mathematical model. The simulation results showed that the elastic force increased rapidly during the compression process and increased slowly during the rebound process, whereas the damping force increased very slowly during the compression process but increased rapidly during the rebound process owing to the effect of the backflow valve. The results of the force characteristic curve analysis of the HPS systems with different excitation frequencies also revealed that when the vibration excitation frequency increased, the elastic, damping, and vertical total forces of the front and rear HPS systems increased quite rapidly.

Analysis on the compression process of multi-stage wobble plate compressor under full pressure condition

Analysis on the compression process of multi-stage wobble plate compressor under full pressure condition

Development of a near-isothermal transcritical CO2 compression system with a liquid piston compressor

Compressors are critical components in vapor compression cycle systems, significantly contributing to energy consumption. As global demand for HVAC&R systems rises, enhancing compressor efficiency becomes increasingly vital. This paper introduces a novel liquid piston compressor integrated with a gas cooler for the transcritical CO2 refrigeration cycle. The liquid piston enables CO2 refrigerant compression within various types of heat exchangers, facilitating the transfer of compression heat to the heat transfer fluid. By releasing significant heat, this compressor allows for removing or downsizing the traditional gas cooler in the refrigeration system. This paper presents the experimental performance of the first near-isothermal compressor utilizing a liquid piston in a vapor compression cycle. The critical parameters affecting heat transfer are analyzed by using a 1-D simulation model to achieve a near-isothermal compression process. The results show that the developed prototype successfully reduced the compression temperature increase from 95 K to 10 K, achieving 90 % isothermal efficiency. Moreover, the 1-D simulation results suggest the smaller internal diameter tubes benefit the isothermal efficiency the most.

Mechanical Properties and Energy Evolution Laws of Rocks Under Freeze–Thaw

In high-altitude mountainous areas, the phenomenon of rock frost damage under repeated freeze–thaw cycles are pronounced, with the deformation and failure processes of rock often accompanied by energy dissipation. To elucidate the energy evolution mechanism of rocks under freeze–thaw cycles, triaxial compression tests and numerical simulation tests were conducted under different freeze–thaw cycles. Results from indoor tests indicate that successive freeze–thaw cycles deteriorate the mechanical properties of rocks. Compared to conditions without freeze–thaw cycles, after 40 freeze–thaw cycles, the peak stress of the rock decreased by 42.8%, the elastic modulus decreased by 64%, and, with increasing confining pressure, the rate of decrease lessened, indicating that confining pressure can inhibit the decline in the mechanical properties of rocks. As the freeze–thaw cycles increase, the total absorption energy (TAE) of rocks gradually decreases. Meanwhile, with increasing confining pressure, the TAE, elastic strain energy (ESE) and dissipated energy (DE) of rocks all gradually increase. However, as the confining pressure increases, the TAE increases by 781%, the ESE increases by 449%, and the DE increases by 6381%. Numerical simulation results reveal that with an increase in the freeze–thaw cycles, shear failure phenomena gradually decrease while tensile failure phenomena gradually increase. During the compression process, the evolution of internal cracks in rocks demonstrates a trend of slow–steady–rapid development, with the number of cracks produced being positively correlated with the freeze–thaw cycles. The performance can provide valuable insights into the degradation mechanism of the mechanical properties of rocks and failure analysis in high-altitude mountainous areas.

Research on weight initialization of CNN student models based on knowledge distillation

Knowledge distillation is a process of weight compression where a complex teacher model trains a simplified student model, making the weights and their distribution crucial. This paper investigates the weight distribution in convolutional and fully connected layers of both teacher and student models. For convolutional layers, it was discovered that both teacher and student models exhibit a piecewise power-law distribution. A verification method based on the piecewise power law distribution of convolutional layers was proposed, and the correctness of this law was confirmed. Detailed analysis of the breakpoints and power exponents reveals that the teacher model has smaller breakpoints than the student model; for weights smaller than the breakpoint, the teacher model’s power exponent is lower than that of the student model, whereas, for weights larger than the breakpoint, the teacher model’s power exponent is higher. Based on these findings, a new weight initialization algorithm for convolutional layers was proposed. For fully connected layers, both models demonstrate a skewed distribution. A verification method based on the skewed distribution of fully connected layers was proposed, and the correctness of this law was confirmed. Analysis of the kurtosis and skewness indicates that the student model exhibits higher kurtosis and skewness than the teacher model. Based on these observations, a new weight initialization algorithm for fully connected layers was proposed. Experimental results show that both initialization methods improve the initial and final accuracy of the student model compared to the He initialization method.

Study of energy absorption and recovery characteristics of shape memory material zero Poisson’s ratio gradient structures

The integration of smart materials with metamaterials offers significant research value in additive manufacturing. This paper proposes a novel approach combining shape memory polymers (SMP) with zero Poisson’s ratio (ZPR) metamaterials to create better space-filling, lightweight, and high-energy absorbing materials. A cellular structure with three deformation processes was designed by adjusting the rib arm lengths of the ZPR lattice AuxHex, forming a 3D gradient structure. The cellular units were also prepared using the dual-nozzle fusion filament printing technique, and the energy absorption and shape recovery properties of various hierarchical gradient structures, compared to the uniform structure, were simulated and analyzed using the viscoelastic intrinsic model. The results indicate that all gradient structures exhibit superior energy absorption capabilities compared to uniform materials, with the energy absorption performance of the optimal gradient material being 44.32% higher than that of the nongradient material, and they also enhance the shape recovery performance to some extent. Furthermore, it was observed that when a lattice layer, which avoids internal rib contact throughout the compression process, is positioned in the middle layer, it harmonizes the deformation of the upper and lower layers, thereby improving overall stability. This configuration enhances both energy absorption and partial shape recovery performance, offering a novel approach for the design of smart material assemblies with graded metamaterial structures. This study provides a new perspective and methodology for the future design of supergradient smart material collections.

Investigating the cooling effect of the inlet flow on the axial compressor performance in different operating conditions

In this article, the compressor performance in wet compression conditions is compared with that of dry compression. Wet condensation has been done through droplets with one-micron diameter and a three percent mass flow rate. The flow inside the compressor is steady and three-dimensional, using the software ANSYS CFX has been simulated. In the case of wet compression, the discrete phase transition model has been used along with the application of active input forces from the continuous phase. The comparison of the present simulation results for dry states with the experimental data reports a good agreement. The results indicate that applying wet compression in the compressor improves adiabatic efficiency by 7.21% in near-stall conditions, 5.21% in design conditions, and 1.78% in choking conditions. The use of wet compression significantly reduces the mass flow rate under operational conditions of choking, it is not recommended to use this method in the operational conditions of choking in the compressor. The results indicate that the compressor stable performance range is reduced by 18.31% with wet compression compared to dry compression, which is unfavorable. Also, the stall margin of the process of wet compression and dry compression was obtained as 2.38% and 8%, respectively. The results of the study showed that with flow injection, the stall margin of the wet compression process was reduced by 5.62% compared to the dry compression process.

The spallation characteristics of polycrystalline aluminum with helium bubbles under a wide range of shock stresses

The spallation behavior of polycrystalline Al with helium (He) bubbles (poly Al–He) under unsupported shock loadings at a wide range of impact velocities was investigated via molecular dynamics simulations. We found that the microstructural features during shock compression and release processes for the poly Al–He are highly analogous to those observed in polycrystalline Al (poly Al), indicating that the bubbles studied here do not have a significant influence on the mechanical deformation before tension. During the tension process, the expansion-merging of He bubbles dominates damage accumulation and leads to the ultimate fracture of the metal, the same as that in a single crystal with He bubbles. The presence of grain boundaries (GBs) does not exhibit an apparent effect on the evolution of He bubbles, resulting in comparable expansion rates for the bubbles in different locations (i.e., near GBs or at grain interiors). Additionally, the nucleation of voids occurs subsequent to bubble expansion due to the much higher critical stress. Voids are preferentially nucleated on GBs when the material is solid and at liquid parts when the material is partially molten, demonstrating that GBs and melting can strongly facilitate void nucleation. However, He bubbles significantly impede void nucleation and growth, resulting in a much smaller quantity and volume of voids formed in the poly Al–He, compared to the poly Al. Furthermore, the critical stress for void nucleation and the spall strength of the metal matrix are reduced by He bubbles.

A method for diagnosing the implosion symmetry in inertial confinement fusion with wide-angle VISAR

Abstract A method for diagnosing implosion symmetry in inertial confinement fusion(ICF) with wide-angle velocity interferometer system for any reflector(VISAR)was proposed in this study. The method considers the object-image relationship of the wide-angle VISAR, characteristics of the fringe pattern, and the symmetry theory; the fringe pattern must be continuous in space to apply this method. Hydrodynamic calculations showed that the radiation-temperature distribution on the surface of capsule was spatially continuous, indirectly proving the applicability of the method. The evolution of P2 asymmetry at different positions of the capsule was examined through an eight-beam laser indirect-drive experiment at a 10 kJ-level laser facility, proving the feasibility of the method. The application of wide-angle VISAR for the diagnosis of implosion symmetry in ICF was more accurate and intuitive and demonstrated high spatiotemporal resolution and wide detection range. This method can provide reference data for the micro-mechanism study of hydrodynamic instability and radiation-driven asymmetry, as well as support for optimizing the implosion compression process to achieve efficient and stable ignition.

Modeling and Simulation of Dynamic Recrystallization Microstructure Evolution for GCr15 Steel Using the Level Set Method.

The microstructure of metallic materials plays a crucial role in determining their performance. In order to accurately predict the dynamic recrystallization (DRX) behavior and microstructural evolution during the hot deformation process of GCr15 bearing steel, a microstructural evolution model for the DRX process of GCr15 steel was established by combining the level set (LS) method with the Yoshie-Laasraoui-Jonas dislocation dynamics model. Firstly, hot compression tests were conducted on GCr15 steel using the Gleeble-1500D thermal simulator, and the hardening coefficient k1 and dynamic recovery coefficient k2 of the Yoshie-Laasraoui-Jonas model were derived from the experimental flow stress data. The effects of temperature, strain, and strain rate on DRX behavior and grain size during the hot working process of GCr15 steel were investigated. Through secondary development of the software, the established microstructural evolution model was integrated into the DIGIMU® software. Metallographic images were imported in situ to reconstruct its initial microstructure, enabling GCr15 steel DRX microstructure finite element simulation of the hot compression process. The predicted mean grain size and flow stress demonstrated a strong correlation and excellent agreement with the experimental results. The results demonstrate that the established DRX model effectively predicts the evolution of the DRX fraction and average grain size during the hot forging process and reliably forecasts DRX behavior.

Experimental Characterization of Reversible Oil-Flooded Twin-Screw Compressor/Dry Expander for a Micro-Scale Compressed Air Energy Storage System

The reversible use of a volumetric machine as a compressor and expander shows potential for micro-scale compressed air energy storage systems because of lower investment costs and higher operational flexibility. This paper investigates experimentally the reversible use of a 3 kW oil-flooded twin-screw compressor as an expander for a micro-scale compressed air energy storage system to assess its operation while minimizing operating costs and the need for adjustments. As a result, the oil injection was only implemented in the compressor operation since the oil takes part in the compression process, while its use appears optional in expander operation. The results indicate that the compressor exhibited an efficiency in the range of 0.57–0.80 and required an input power from 1 kW up to 3 kW. These values decreased for the expander, whose efficiency was in the range of 0.24–0.38 and the delivered power between 300 and 1600 W. The experimental data allow assessing the operation of such machine in a hypothetical micro-scale compressed air energy storage. The calculation revealed that this machine may operate in this energy storage asset and deliver up to 90% of the power recovered in the charging process when the temperature of the stored air is 80 °C.

Analysis of mechanical properties and energy evolution mechanism of frozen calcareous clay under multi-factor interaction

Research investigating the complex mechanical properties and energy evolution mechanisms of frozen calcareous clay under the influence of multiple factors is crucial for optimizing the artificial ground freezing method in shaft sinking, thereby enhancing construction quality and safety. In this study, a four-factor, four-level orthogonal test was devised, taking into account temperature, confining pressure, dry density, and water content. The complex nonlinear curvilinear relationship between deviatoric stress, volume strain, and axial strain of frozen calcareous clay under different interaction levels was analyzed. The sensitivity of each factor to the peak volume strain was explored, and the energy evolution mechanism of frozen calcareous clay during the triaxial compression process was analyzed. The findings are summarized as follows: (1) The deviatoric stress-axial strain curves demonstrate the strain-hardening characteristics of frozen calcareous clay specimens. Furthermore, as temperature decreases, the hardening degree increases. (2) Sensitivity analysis indicates that the factors’ influence on peak volumetric strain ranks as follows: dry density > confining pressure > temperature > water content. Under the various interactions, specimens exhibit significant volumetric shrinkage. When the temperature remains constant, peak volumetric strain is negatively correlated with dry density but positively correlated with confining pressure. (3) Input energy density, elastic strain energy density, and dissipated energy density of frozen calcareous clay all increase with axial strain. (4) When temperature is held constant, both peak input energy density and peak dissipated energy density rise with increasing confining pressure. Meanwhile, peak elastic strain energy density shows a linear increase with higher confining pressure and lower temperatures.

GCom: Fine-grained Compressors in Graphics Memory of Mobile GPU

Nowadays, GPUs significantly boost rendering performance. However, the high memory requirements limit their use, especially on low-end mobile platforms. Compression techniques have been widely adopted to reduce memory consumption but face two primary issues when applied to mobile GPUs: 1) low repetition ratio caused by small raw data sizes and concurrency, and 2) low locality caused by unpredictable rendering behaviors. These two limitations result in a low compression ratio when compressors are applied to low-end mobile devices. This paper introduces gCom , a fine-grained rendering compressor accelerated by GPUs. To improve the compression ratio, gCom incorporates the following innovations: 1) Unlike other compression techniques that use frames or tiles as basic processing units, gCom is the first to employ a fine-grained processing unit (i.e., the color channel), enhancing repetition amplification without increasing raw data. 2) gCom introduces two key features, hierarchical delta , and channel decorrelator , which maximize the locality of adjacent channels and reduce raw data size. 3) To maintain the original GPU throughput, gCom revolutionizes the Golomb-Rice algorithm and proposes a new compression approach, the Parallel-Oriented Golomb-Rice (POGR) algorithm, enabling parallel execution of both decompression and compression processes. The entire design of gCom utilizes only idle resources and existing commands on mobile GPUs, thus keeping purchasing costs low. To date, gCom has improved the channel locality by nearly 50%. The best compression achievement received by gCom has reached around 20%.

Investigation of the two-phase flow and heat transfer characteristics with different inlet and outlet arrangements in the ionic liquid compressor for the hydrogen refuelling station

The ionic liquid compressor is a prospective device for hydrogen pressurisation in the hydrogen refuelling station. Ionic liquids are introduced into the compressor chamber between hydrogen and the free piston for lubrication, sealing and cooling. Therefore, it is essential to investigate the two-phase flow and heat transfer since they impact the operational efficiency of the compressor. In this research, numerical simulation using the volume of fluid method was taken out to study the two-phase flow and heat exchange characteristics of hydrogen and ionic liquids in one compression process with four different inlet and outlet arrangements. The results showed that the inlet flow shock caused severe deformation of the phase interface, producing a large number of droplets and bubbles, which significantly enhanced the heat transfer. This deformation was greatly influenced by inlet and outlet arrangements. In general, the axial inlet design caused more obvious interface distortion than the radial one, enlarging the heat transfer area while also raising the risk of the piston being exposed. The recommended structure was the axial decentralised inlet form, which avoided piston exposure while maximizing the heat transfer area, with a hydrogen temperature rise of 16.24 K and a polytropic index of 1.11.

Effect of different crystalline directions on the mechanical properties and processing maps of Zr-Nb alloy for orthopedic applications.

In the current study, the effect of direction on the hot compression behavior, processing map, and microstructure of Zr-Nb alloy after bidirectional hot forging was studied. Accordingly, the alloy billet was hot-forged and samples at different directions were extracted. Phase changes and microstructure of the samples were characterized. Additionally, hot compression tests were carried out on the samples in the temperature and strain rate ranges of 800-900°C and 0.001-1 s-1, respectively. Microstructure examinations revealed that the forging resulted in the formation of various alpha spherical grains elongated along the forging direction. Along the directions of 30 and 60°, the high strain rate during forging caused the formation of secondary recrystallized grains in addition to grains elongated in the forging direction. Hardness measurement results showed that the highest hardness was related to the zero-degree direction due to the high fraction, refinement, and morphology of the alpha phase formed during the hot forging process. Full recrystallization of hot-compression samples was evident at 850°C. Processing maps suggested the optimum deformation of the alloy to be within the strain rates 0.01-0.001at 850°C. Consequently, deformation within this range results in the desired dynamic recrystallization phenomenon.

Compressive Signal Processing for Estimating Range-Velocity-AoA in FMCW Radar Applications

Compressive Signal Processing for Estimating Range-Velocity-AoA in FMCW Radar Applications

Improved intensity rounding and division near lossless image compression algorithm using delta encoding

This paper presents RIFD-DLT, an advanced near-lossless image compression algorithm that combines Delta Encoding with the original rounding the intensity followed by division (RIFD) method. The RIFD method first minimizes the image intensities, which makes the next compression stages more efficient. Subsequently, Delta Encoding subtracts neighboring rows in each of the image's three-color matrices, using the proximity of pixel values in adjacent rows to further reduce the image intensity. Extensive investigations show that RIFD-DLT outperforms the state-of-the-art algorithms and benchmarks with respect to compression ratio and processing time. More specifically, RIFD-DLT compresses data from 11520 KBs to 2131 KBs with an 81.93% reduction and a 43.7% improvement over original RIFD-Huffman when compressing Kodak Image set. When comparing the RIFD-DLT with LICA algorithm, the total file size is reduced by 71.2%, representing a 10.73% improvement for RIFD-DLT. Also, RIFD-DLT shows notable speed gains over RIFD-Huffman, requiring only 34.62 seconds to compress and decompress all images from three datasets (Waterloo, Kodak and EPFL), as compared to 50.99 seconds for RIFD-Huffman. As for the image quality, the proposed algorithm achieved an average PSNR values of 58.51 dB, 51.3 dB, and 52.22 dB for the EPFL, Kodak, and Waterloo image sets, respectively, demonstrate the excellent image quality that persists after decompression, with a minimal distortion that is imperceptible to the human visual system and identically to the RIFD-Huffman PSNR. These findings show that, while preserving excellent image quality, RIFD-DLT provides an incredibly efficient and fast method of image compression.