High Compression Research Articles

Sub-Nanosecond Microwave Passive Pulse Generation With High Power Compression Factor Using Structural Reflection

Sub-Nanosecond Microwave Passive Pulse Generation With High Power Compression Factor Using Structural Reflection

VNVC: A Versatile Neural Video Coding Framework for Efficient Human-Machine Vision.

Almost all digital videos are coded into compact representations before being transmitted. Such compact representations need to be decoded back to pixels before being displayed to humans and - as usual - before being enhanced/analyzed by machine vision algorithms. Intuitively, it is more efficient to enhance/analyze the coded representations directly without decoding them into pixels. Therefore, we propose a versatile neural video coding (VNVC) framework, which targets learning compact representations to support both reconstruction and direct enhancement/analysis, thereby being versatile for both human and machine vision. Our VNVC framework has a feature-based compression loop. In the loop, one frame is encoded into compact representations and decoded to an intermediate feature that is obtained before performing reconstruction. The intermediate feature can be used as reference in motion compensation and motion estimation through feature-based temporal context mining and cross-domain motion encoder-decoder to compress the following frames. The intermediate feature is directly fed into video reconstruction, video enhancement, and video analysis networks to evaluate its effectiveness. The evaluation shows that our framework with the intermediate feature achieves high compression efficiency for video reconstruction and satisfactory task performances with lower complexities.

Lightweight rPPU Eco-block Using Recycled Plastic (rP) and Polyurethane (PU) for Soft Subgrade Soil Stabilisation

The stability of the soil plays a crucial role in the safety and longevity of various civil engineering structures. However, problematic soil conditions, such as clay soil and peat soil, often pose challenges due to their high-water content, poor strength, low bearing capacity, and high compressibility. This research focuses on addressing these challenges by utilizing lightweight fill materials as an effective solution for backfilling applications. The study aims to investigate the characteristics and performance of a novel lightweight fill material using recycled plastic (rP) and polyurethane (PU) known as rPPU ecoblock. The eco-block is mainly fabricated using recycled plastic bottles, recycled plastic packaging, and polyurethane, offering a sustainable approach to waste management and construction materials. To achieve the research objectives, a series of experiments will be conducted. The strength and density of plastic bottles filled with recycled plastic packaging will be analyzed, providing insight into their mechanical properties. Furthermore, the water absorption and buoyancy of the lightweight rPPU eco-block are evaluated, considering its suitability for various construction scenarios. The research findings contribute to the understanding of the physical and mechanical characteristics of the rPPU eco-block, providing valuable information for its potential application as a backfill material. The compressive strength, water absorption, and buoyancy tests conducted per ASTM standards provide quantitative data on the eco-block's performance. The use of lightweight fill materials, particularly the rPPU eco-block, offers benefits such as reduced embankment self-weight, improved stability, and minimized environmental impact. Moreover, the recycling of plasticwaste contributes to the circular economy and aligns with sustainable development goals (SDG): SDG9 and SDG11. The results of this research provide valuable insights for engineers, construction professionals, and stakeholders involved in geotechnical and civil engineering projects.

DEVELOPMENT OF AEROSPACE IMAGES PRELIMINARY PROCESSING METHOD FOR SUBSEQUENT RECOGNITION AND IDENTIFICATION OF VARIOUS OBJECTS

Nowadays, the application of hyperspectral images is vital for every section of the humanity life such as agrotechnical research for the field condition state and water security. This article presents a new lossless data compression algorithm focused on the processing of hyperspectral aerospace images. The algorithm takes into account inter-band correlation and difference transformations to effectively reduce the range of initial values. correlation allows you to find the best reference channel that defines the sequence of operations in the algorithm, which contributes to a significant increase in the compression ratio while maintaining high data quality. The practical implementation of the algorithm lies in the process of the transfer the lower size file with high efficiency for unmanned aerial vehicle and satellites to save more computational resources. This method demonstrates high computational efficiency and can be applied to various tasks that require efficient storage and transmission of hyperspectral images. The importance of processing hyperspectral data and the problems associated with their volume and complexity of analysis were described. Current approaches to data compression are considered and their limitations are identified, which justifies the need to develop new methods. The relevance and necessity of effective compression algorithms for aerospace applications is emphasized. An analysis of existing methods and algorithms for compressing hyperspectral data was carried out. Particular attention is paid to approaches that use cross-channel correlation and difference transformations. The effectiveness of current methods is evaluated and their shortcomings are identified, which serves as a justification for the development of a new algorithm. A developed lossless data compression algorithm based on the use of inter-band correlation and difference transformations was described. The stages of forming groups of channels and the selection of optimal compression parameters are considered in detail. The method of determining the reference channel, which sets the sequence of operations in the algorithm, which provides more efficient data compression, is especially noted. The advantages and possible limitations of the new approach, as well as its potential for practical use, are discussed. It was noted that the developed method successfully solves the problems associated with the volume of hyperspectral data, providing a high compression ratio without quality loss. The prospects for further development of the algorithm and its application in various fields of science and technology are discussed.

Geotechnical issues of investigation of the technical condition of the structure on weak soils according to the boundary element method

The article considers the controversial issue of the need to take into account the increasing coefficient to the soil deformation modulus obtained on the basis of compression studies for the design of loess frozen soils. It is well known that weak soils can have low bearing capacity and high compressibility, which makes them difficult to construct and operate structures. It is known that in laboratory conditions, the modulus of soil deformation is usually determined by compaction with a static load without the possibility of lateral expansion in a rigid ring. The disadvantage of the compression device is the low accuracy of measurements, which is emphasised by many researchers due to the fact that the friction forces of the soil sample on the ring walls reduce, depending on the moisture content and soil type, the vertical pressure applied to the sample during the test. This leads to a false decrease in the actual value of the soil deformation modulus. To determine the reliability of the two approaches to determining the soil deformation modulus, the settlements of the foundations of grain storage silos on dangerous degraded loess soils were calculated by the numerical method of boundary element (MBE) using an elastic-plastic model, with and without taking into account the soil deformation modulus. It has been found that solving the problems of assessing the technical condition of a building is associated with geodetic and engineering-geological surveys and the analysis of these results, since the stress-strain state of the building-foundation system and the peculiarities of deformation of the soil base depend on them. After all, the problem of protecting a building from rolling is quite relevant. The design or reconstruction of structures on foundations with weak soils (with a deformation modulus E < 5 MPa) is also associated with the problem of ensuring that the calculated deformation values do not exceed their maximum permissible values for the experimental structure. The results of numerical studies are compared with the method of finite element (MFE) calculation and experiment.

Fabrication of matrix graphite with a high degree of graphitization for spherical fuel elements by using natural microcrystalline graphite fillers

Matrix graphite is used as a structural material, thermal conductor, moderator, and secondary fission product barrier for fuel elements in high-temperature gas-cooled reactors (HTRs). Due to its high graphitization degree and compressibility, natural flake graphite (NFG) is used as the main filler in traditional A3-3 matrix graphite, whereas artificial graphite (AG), with a lower graphitization degree than NFG, serves as an additive for toughness and gas permeability. Matrix graphite could be improved in terms of thermal conductivity, oxidation resistance, and irradiation performance by increasing the degree of graphitization. However, reports on the development of new matrix graphite formulations are scarce. In this study, MG-20 matrix graphite was prepared by mixing 60 wt% NFG, 20 wt% natural microcrystalline graphite (MG), and 20 wt% phenolic resin. Due to the high graphitization degree (higher than AG) and low coefficient of thermal expansion (CTE) of MG, MG-20 exhibited higher thermal conductivity (∼6%) and lower CTE (∼2.4%) than A3-3. Thus, MG-20 with higher graphitization degree and better thermal properties than A3-3 could improve the performance of HTR fuel elements in the future.

Degradable biporous polymeric networks based on 2-methylene-1,3-dioxepane: Towards hierarchically structured materials meant for biomedical applications

For the first time, the preparation of doubly porous “poly(ε-caprolactone)-like” networks through free-radical ring-opening copolymerization of 2-methylene-1,3-dioxepane with divinyl adipate was achieved via a double porogen templating approach. This versatile strategy allowed for the formation of macropores of around 150 μm generated by removal of sieved and sintered NaCl particles in water, while smaller pores in the 1–10 μm range were created by phase separation during the copolymerization process through a syneresis mechanism in the presence of a porogenic solvent. The chemical nature of the as-obtained scaffolds was evidenced by Raman spectroscopy. The two distinct porosity levels could be examined by scanning electron microscopy and mercury intrusion porosimetry. The nature of the porogenic solvent as well as its volume proportion and the amount of crosslinking agent in the polymerization feed allowed for finely tuning the porous features of the micropores. The crucial role of the double porosity of such biporous scaffolds on their water uptake and mechanical properties under compression was assessed by comparing them with their monoporous analogues, while their degradability was investigated in different alkaline aqueous media. The double porosity enabled a synergistic effect regarding the water uptake of the resulting scaffolds when compared to their monoporous counterparts. Doubly porous polymeric materials with appropriate mechanical properties were obtained, possessing high compressibility and shape memory behavior upon consecutive compression cycles. Finally, these materials display degradation rates that could be controlled depending on medium pH.

Fabrication of strong and elastic HIPPEs gel by rigid-flexible double network structure as a novel adipose tissue substitutes

Fat mimics are one of the most common substitutes for animal fats in processed foods. However, basing on high internal phase Pickering emulsion (HIPPEs) gel imitate adipose tissue to achieve the desired strength and elastic, while the formation and stabilization mechanism are barely understood. Here, we proposed a strategy to fabricate rigid-flexible double network using κ-carrageenan (CA) and bacterial cellulose (BC), in oder to improve the mechanical performance of HIPPEs gel. The effects of different ratios of CA/BC (2:1, 4:1, 8:1) and K+ addition on the properties of HIPPEs-CA/BC gels were investigated. Results showed that HIPPEs-CA/BC 8:1 & K+ exhibited better rheological, textural, oil holding capacity and organoleptic properties. Thermal softening behavior of HIPPEs-CA/BC 8:1 & K+ was similar to the pork adipose tissue. The microstructure of gel demonstrated that HIPPEs-CA/BC 8:1 & K+ was featured with honeycomb-like pore and network walls, which in turn comprise interpenetrated double network structures. Meanwhile, it showed an ultrahigh stress, high Young's modulus and good cyclic compress behavior. Additionally, the hydrogen bonds and K+-cross-linked were proved to play crucial roles in facilitating the formation of a stable and elastic CA/BC matrix. This study establishes structure-performance mechanisms in strongly and elastically structured HIPPEs gels, providing an advanced strategy for developing HIPPEs gel with promising applications in adipose tissue substitutes.

Lightweight porous mullite-silica ceramics with multistage pore structure, low thermal conductivity and improved strength

Thermal protection was always a prominent issue in the aerospace industry. For vehicle safety, reliability and payload requirements, thermal protection materials were usually expected to possess low density, superior mechanical and thermal insulation properties. Here, lightweight and high-strength porous mullite-silica ceramics were manufactured using particle-stabilized foaming technique. The strength and thermal insulation properties of porous ceramics modified with hollow silica spheres were significantly enhanced. A 10 wt% hollow spheres addition achieved a 28.9 % increase in strength and a 33.4 % decrease in thermal conductivity with almost constant porosity (from 86.39 % to 87.04 %). Considering the characteristics of light weight, high compression strength and superior thermal insulation performance, porous ceramics could be applied as thermal protection materials in the aerospace sector.

Hierarchical Indexing and Compression Method with AI-Enhanced Restoration for Scientific Data Service

In the process of data services, compressing and indexing data can reduce storage costs, improve query efficiency, and thus enhance the quality of data services. However, different service requirements have diverse demands for data precision. Traditional lossy compression techniques fail to meet the precision requirements of different data due to their fixed compression parameters and schemes. Additionally, error-bounded lossy compression techniques, due to their tightly coupled design, cannot achieve high compression ratios under high precision requirements. To address these issues, this paper proposes a lossy compression technique based on error control. Instead of imposing precision constraints during compression, this method first uses the JPEG compression algorithm for multi-level compression and then manages data through a tree-based index structure to achieve error control. This approach satisfies error control requirements while effectively avoiding tight coupling. Additionally, this paper enhances data restoration effects using a deep learning network and provides a range query processing algorithm for the tree-based index to improve query efficiency. We evaluated our solution using ocean data. Experimental results show that, while maintaining data precision requirements (PSNR of at least 39 dB), our compression ratio can reach 64, which is twice that of the SZ compression algorithm.

Bird-nest inspired cellulose-based biofoam with excellent performance enabled by gas–liquid interface co-assembly and thermal welding for plastic replacement

Traditional plastic foam, typically derived from fossil fuel-based polymers that are resistant to natural degradation, faces environmental challenges. As an alternative, cellulose, a biodegradable polymer, shows promise in the production of eco-friendly foam. Nonetheless, its reliance on hydrogen bonding between fibers poses limitations for practical applications. Here, drawing inspiration from bird nest structures, a straightforward and scalable method (co-assembly and thermal welding) has been developed for creating cellulose-PLA biofoam. The resulting biofoam displays advantageous properties such as low density (12.9 ∼ 27.1 kg/m3), high compression strength (modulus of 12.1 MPa·cm3·g−1), good thermal stability, and water stability (maintaining structural integrity in water). Moreover, it exhibits exceptional degradation rates (significant degradation within 40 days) and recyclability. Thus, this biofoam holds promise as a sustainable alternative to standard plastic foams, mitigating “white pollution.”

The abnormal deformation behaviors in commercial pure Ti during high speed compression

The effect of high speed compression on the deformation behaviors of pure titanium (Ti) was investigated in this paper. The results indicated that deformation twinning dominated the entire deformation process. In addition to the commonly observed twinning modes 101̅2<101̅1>,112̅1<112̅6>and 112̅2<112̅3>twinning, the uncommon twinning modes 101̅1<101̅2>, 112̅4<224̅3> twinning, and a rare twinning mode 112̅3<112̅2> twinning which has not been reported in previous literature, were observed. The 112̅3<112̅2> twinning presented an orientation relationship of 87° <101̅0>. Moreover, deviations from the ideal twinning relationship were observed in some twins which might due to the deformation induced dislocation-twin interactions. Alongside twinning, high angle kink bands with a misorientation of 61°<71017̅3> were locally activated to accommodate the deformation. These abnormal deformation behaviors, including the formation of unusual twins and high angle kink bands, occurred in grains that were less favorable for triggering common dislocation and twinning modes, based on the Schmid factor calculations. The high strain rate during high speed compression limited heat dissipation time and generated additional energy, thereby enhancing the flow stress and raising the temperature, which facilitated the occurrence of these abnormal deformation behaviors.

Experimental investigation on lateral resistance capacity enhancement effect of a self-centering shape factor in self-centering pier systems

In self-centering (SC) pier systems, a rocking interface is typically employed at the bottom of a pier to achieve a gap-opening mechanism. However, compared with the full-section bending state of the bottom section of a ductile pier (DP), the local compressive state of the rocking interface in the SC pier inevitably leads to a significant reduction in the lateral resistance capacity. Although a prestressing tendon (PT) force can improve the lateral resistance capacity, it also induces local damage. Moreover, its enhancement effect is limited, particularly in the case of a column with a high axial compression ratio. Therefore, this study proposes an innovative measure to significantly improve the hysteretic performance of an SC pier without inducing additional damage, which is to raise the location of the rocking interface. First, the SC shape factor ξSC is innovatively defined to quantify the above-mentioned measure, and its working mechanism is investigated in detail in this study. Second, a high-lateral-resistance SC pier system (HLRSCP), which applies the concept of ξSC, is proposed and introduced for its advantages. Third, hysteretic tests of the DP and HLRSCP with high axial compression ratios are performed and analyzed. Finally, the enhancement effect of ξSC on the lateral resistance capacity is parametrically examined using a finite element model, and the feasible region of ξSC is inferred and presented. The results validate the effectiveness and feasibility of the concept of the SC shape factor in improving the hysteretic performance of the SC pier system.

A New Approach to Evaluate Pressure of Solids at High Compression

A New Approach to Evaluate Pressure of Solids at High Compression

Computational insights into flame development and emission formation in an ammonia engine with hydrogen-assisted pre-chamber turbulent jet ignition

Ammonia, as a promising green fuel for achieving carbon neutrality and zero-carbon emissions, encounters obstacles in practical engine applications due to its intrinsic combustion properties like low burning velocity and high autoignition temperature. Hydrogen-assisted pre-chamber turbulent jet ignition (TJI) technology has recently demonstrated great potential in extending the lean limits and enhancing the stability of ammonia combustion. As such, this study conducts a comprehensive analysis on the flame development and emission formation processes under the active pre-chamber TJI mode fueled with ammonia and hydrogen using computational fluid dynamics (CFD) modeling integrated with detailed chemical kinetics, particularly focusing on the effects of hydrogen energy ratio and spark timing. It is found that the active ammonia-hydrogen TJI engine is typically characterized by four primary physical processes involving H2 mixture preparation in the pre-chamber, flame kernel formation and development within the pre-chamber, the formation and ejection of hot jet across the orifices, and the turbulent flame initiation and propagation in the main chamber. Hydrogen injection holds a scavenging effect on the residuals in the pre-chamber while forms fuel stratification near the spark plug, enhancing the ignition stability. Besides, the current combustion mode is commonly characterized by two-stage heat release in the main chamber, but exhibits a three-stage heat release as increasing the premixed H2 ratio. The first stage is dominated by a hot jet flame, the second stage is characterized by turbulent flame propagation or autoignition, and the third stage is induced by a secondary jet ejected from the pre-chamber, which becomes more prominent as the H2 ratio increases. Hydrogen blending could not only facilitate the turbulent flame propagation of NH3-air mixture in the main chamber but also enhance the initiation of flame kernel in the pre-chamber, thereby promoting the overall combustion process and potentially improving the thermal efficiency. The N2O emission is produced in two distinct stages, wherein N2O is generated and undergoes conversion during the main combustion phase, while unburned crevice gases mix with burned gases and convert into N2O during the expansion stroke. Increasing the premixed hydrogen ratio leads to an increased in-cylinder temperature, which in turn facilitates a reduction in N2O emissions and mitigates unburned ammonia. Furthermore, optimization of the spark timing is required after implementing the hydrogen addition into the intake manifold to achieve desirable combustion phasing and further improve the thermal efficiency. Finally, a novel combustion concept, denoted as TJI assisted compression ignition mode, is proposed for achieving high thermal efficiency in ammonia engines via adopting high compression ratio and premixed ammonia-hydrogen charge under the TJI strategy.

Impact on air-assisted direct injection on knock and energy conversion in a downsized elliptical rotary engine with high compression ratio

The elliptical rotor engine (ERE) is a novel engine type that enables a high power-to-weight ratio and high compression ratio (CR), resulting in a significant increase in thermal efficiency. However, the high CR also makes the engine prone to knock, limiting its performance potential. Addressing the challenge of knock induced by high CR is essential for optimizing ERE performance. This study introduces an innovative approach, combining CR with an air-assisted direct injection (AADI) device, using advanced computational fluid dynamics simulations to investigate their effects on knock and energy conversion characteristics of a downsized gasoline ERE. The findings reveal that increasing CR from 9.26 to 11 boosts indicated thermal efficiency (ITE) by 18.27%. However, knock occurrence disrupts energy distribution, leading to increased heat transfer losses. Notably, knock appears earlier and more intensely at the front end of the combustion chamber compared to the back end. The incorporation of AADI markedly reduces knock tendency, enhances ITE by 14.28% relative to the prototype, and reduces heat transfer loss by 42.41%. This study demonstrates that AADI not only effectively inhibits knocking, but also significantly improves the overall performance of the ERE, providing a promising solution for the development of high-performance rotary engines.

Multi-Dimensional Iterative Constitutive Model of Concrete under Complex Stress Conditions in Composite Structures

In composite structures or complex concrete members, some concrete bears multiple forces, called core concrete. The properties of the core concrete are variable under complex stress conditions, which will influence the structure performance analysis. Therefore, it is necessary to establish an accurate and theoretical constitutive model of concrete under complex stress conditions. The elastic–plastic properties of concrete in complex stress conditions were analyzed first. Then, the failure criterion of concrete in complex stress conditions was discussed to identify the key parameters. And the relationship between the stress–strain curve and failure criterion was analyzed through mathematical derivation. Finally, the multi-dimensional iterative constitutive model of concrete under complex stress conditions was established and verified. Based on the analysis results, the concrete under multi-axial stress conditions shows a spindle-shape stress envelope diagram. The failure criterion should be established by the analysis of concrete under high multi-axial compression conditions, tension–compression conditions, and shear–compression conditions. The plastic modulus is the key to reflecting the plastic strain development trend and the stress–strain relationship.

Mechanically Robust Lubricating Hydrogels Beyond the Natural Cartilage as Compliant Artificial Joint Coating.

Natural cartilage exhibits superior lubricity as well as an ultra-long service lifetime, which is related to its surface hydration, load-bearing, and deformation recovery feature. Until now, it is of great challenge to develop reliable cartilage lubricating materials or coatings with persistent robustness. Inspired by the unique biochemical structure and mechanics of natural cartilage, the study reports a novel cartilage-hydrogel composed of top composite lubrication layer and bottom mechanical load-bearing layer, by covalently manufacturing thick polyelectrolyte brush phase through sub-surface of tough hydrogel matrix with multi-level crystallization phase. Due to multiple network dissipation mechanisms of matrix, this hydrogel can achieve a high compression modulus of 11.8MPa, a reversible creep recovery (creep strain: ≈2%), along with excellent anti-swelling feature in physiological medium (v/v0 < 5%). Using low-viscosity PBS as lubricant, this hydrogel demonstrates persistent lubricity (average COF: ≈0.027) under a high contact pressure of 2.06MPa with encountering 100k reciprocating sliding cycles, negligible wear and a deformation recovery of collapse pit in testing area. The extraordinary lubrication performance of this hydrogel is comparable to but beyond the natural animal cartilage, and can be used as compliant coating for implantable articular material of UHMWPE to present, offering more robust lubricity than current commercial system.

Experimental Behavior of a Prototype 3m-Span Modular Glass Pedestrian Bridge

This research is related to the structural performance of a shell-type system made of hollow glass units (HGU) that utilizes glass as the primary structural material. The efficient structural function of the proposed shell-type system is designed using Polyhedral Graphic Statics to achieve a system geometry that maximizes in-plane compression and limits the presence of tension. The large-scale shell structure is constructed using a modular assembly of individual hollow glass units. To date, the research team has completed studies on individual HGU strength and stiffness, and the performance of the interface material necessary to transmit the high in-plane compression forces between neighboring HGUs. As well, the feasibility of the proposed modular system has also been demonstrated through the successful assembly and disassembly of a 3 m span prototype pedestrian bridge known as Tortuca. Tortuca is comprised of 13 individual interlocking HGUs assembled into a compression-dominant form supported on steel abutments. In the current research study, the physical performance of Tortuca is experimentally investigated under controlled laboratory testing and using an extensive assortment of displacement and strain sensors. Significant findings related to experimental testing of Tortuca will be reported.

Comparison of two ablation procedures combined with high ligation and foam sclerotherapy and compression therapy for patients with venous leg ulcers

ABSTRACT Aim To compare the ablation techniques’ efficacy of endovenous microwave ablation (EMA) combined with high ligation (HL), foam sclerotherapy (FS) and compression therapy (CT) and endovenous laser ablation (EVLA) combined with HL-FS-CT in the treatment of VLUs. Method 301 consecutive patients with VLUs from 2013 to 2022 in a 3200-bed hospital were intervened by EMA combined with HL-FS-CT and EVLA combined with HL-FS-CT were retrospectively compared. Results One hundred thirty-four patients underwent EMA+HL-FS-CT and 167 patients underwent EVLA+HL-FS-CT. The primary outcome of the ulcer healing time was 1.45(0.75–1.5) months and 1.86(0.5–2.5) months, respectively, in the two groups (HR for ulcer healing was 1.26, 95% CI [0.96–1.66], p = 0.097). Secondary outcomes included that no significant difference was found in ulcer recurrence and GSV recanalization and complications between the two groups, and the postoperative VCSS and AVVQ were significantly lower than the baseline values in the respective groups (p = 0.0001). Conclusion EMA+HL-FS-CT and EVLA+HL-FS-CT are both effective at treating VLUs. Both of the two comprehensive treatments were beneficial to the healing of ulcers, but no evidence showed which one was superior in the ulcer healing time.