Compact Structure Research Articles

Super-Tough, Non-Swelling Zwitterionic Hydrogel Sensor Based on the Hofmeister Effect for Potential Motion Monitoring of Marine Animals.

Hydrogel-based electronic devices in aquatic environments have sparked widespread research interest. Nevertheless, the challenge of developing hydrogel electronics underwater has not been profoundly surmounted because of the fragility and swelling of hydrogels in aquatic environments. In this work, a zwitterionic double network hydrogel comprisedof polyvinyl alcohol (PVA), poly(sulfobetaine methacrylate) (PSBMA), and sulfuric acid (H2SO4) demonstrates super-tough and non-swelling performance. The Hofmeister effect of H2SO4 and PSBMA induces the PVA chains to form numerous nanocrystalline domains, which serve as the primary physical crosslinking points and provide effective energy dissipation. H2SO4 induces a strong salting-out effect to facilitate PVA crystallization and the formation of a dense and stable network structure that inhibits swelling. The resulting hydrogel exhibits an ultra-high toughness of 4.61MJm-3, non-swelling, and long-term stability for up to a month in pure water and seawater. Based on this, a hydrogel-based seawater strain sensor has been developed to monitor the underwater movements of marine animal models. Reliable and stable sensing performance ensures real-time collection of underwater motion signals, despite the impacts of water flow and the interference of ions. This study provides a facile approach to designing super-tough and non-swelling hydrogels and further expands the application of underwater electronic devices.

Influences of Zr and V Addition on the Crystal Chemistry of θ-Al13Fe4 and the Grain Refinement of α-Al in an Al-4Fe Alloy Based on Experiment and First-Principle Calculations

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al13Fe4, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with more compact structures, such as α-Al15(Fe,Mn)3Si2. The addition of alloying elements is a crucial strategy for modifying the microstructure during the solidification process of aluminum alloys. This study investigates the effects of adding vanadium (V) and zirconium (Zr) on the morphology and crystal chemistry of θ-Al13Fe4 in an Al-4Fe alloy, employing a combination of experimental observations, first-principle calculations, and thermodynamic analysis. Our findings indicate that zirconium significantly refines both the primary θ-Al13Fe4 particles and the α-Al grains. Additionally, a small amount of vanadium can be incorporated into one of the Wyckoff 4i Al sites in θ-Al13Fe4, rather than occupying any Fe sites, under casting conditions, in addition to the formation of binary Al-V phases.

Study on the anchoring properties of new water glass-modified alkali-activated portland cement materials

This study developed a novel water glass-modified alkali-activated portland cement (WGSC) anchoring agent, characterized by low cost, rapid setting, early strength, and slight expansion. It is suitable for fully bonded anchor rod anchoring in soft rock tunnels. Using orthogonal experiments and range analysis, the optimal composition of WGSC was determined: silicate cement as the matrix, water-cement ratio of 0.3, 20 % sodium silicate with a modulus of 3.3, 2.5 % early strength agent, and 9 % UEA. The initial/final setting times were 6.72/8.63 minutes, linear expansion rates at 3 days/7 days were 0.32 %/0.54 %, and compressive strengths at 1 hour/24 hours were 16.4/28.2 MPa. Pull-out model tests demonstrated a 47.95–92.85 % increase in 24 h tensile bond strength compared to conventional silicate cement anchoring agents. Corrosion resistance tests indicated WGSC maintained a stable appearance compared to traditional agents. SEM analysis revealed a dense structure and clear network in WGSC, while XRD analysis identified microcomponents mainly as CSH, active silica (SiO2), and CASH, contributing to its dense structure and ideal expansion properties, facilitating superior anchoring and durability. This research elucidates the mechanism of WGSC, confirming its rapid setting, compressive strength, and corrosion resistance advantages, making it economically feasible and advantageous for application and promotion, thereby providing insights for the development of anchoring materials in highly deformed soft rock tunnels.

Direct observation of sodium dendrites to decipher the complicated behavior of electrolyte systems

The compatibility of the electrolyte system with the metal anode, which is often overlooked, is pivotal in realizing the development of a long-life battery. In the present contribution, the compatibility of the diglyme-based electrolyte systems with the sodium metal anode is examined and found that the solvation structure of the electrolyte plays a central role in controlling the sodium deposition morphology. The localized Raman and 1H NMR spectroscopy reveals that the solvation structure for ClO4—, PF6—, and CF3SO3— is distinct and differs from each other. While a loose solvation structure is observed for ClO4—, CF3SO3— based electrolytes exhibit a compact solvation structure. In-situ optical microscopy provides real-time information about the sodium deposition morphology, varying from needle-, tree- and moose-like morphology in ClO4—, PF6—, and CF3SO3— based electrolytes, respectively. The Coulombic efficiency (Na//Cu) and stripping/plating overpotential of sodium (Na//Na) are also sensitive to the structure of the solvation shell. In addition, the post-cycle XPS analysis suggests that the CF3SO3— based electrolytes lead to the formation of an inorganic-rich SEI. This comprehensive study underscores the importance of electrolyte composition in achieving stable sodium metal anodes, providing valuable insights for the development of high-performance sodium metal batteries.

Protein digestibility in wheat noodles: The inhibitory effect and its mechanism of wheat bran dietary fiber

This study investigated the effects of different wheat flour extraction rate (35–95%) on the protein digestibility of those noodles. And to further elucidate the internal mechanism of above phenomenon, wheat flour with different amounts of wheat bran dietary fiber (WBDF) was produced by adding endogenous WBDF. Results indicated that protein digestibility rose significantly with increasing flour extraction rate, peaking at 91.85% at 80% extraction, before trending downward to 85.71% at 95% extraction. Further, among noodles containing different WBDF content, increasing WBDF content to 6% enhanced the formation of β-sheets, boosting I755 levels and reducing I854/I830 levels, thus decreasing protein digestibility. As WBDF content rose further, it promoted transition from β-sheets to β-turn, decreasing I755 and increasing I854/I830, enhancing protein digestibility slightly. The changes indicated that low level of WBDF induced a more compact protein secondary structure to inhibit protein digestion. Conversely, in noodles with high level of WBDF (>6%), the looser protein secondary structure partially alleviated the inhibitory effect of WBDF on protein digestion, which was caused by part of WBDF penetrating the protein's hydrophobic core. Moreover, the static quenching effect of WBDF on pepsin hydrolysis sites through hydrophobic interaction, especially the tyrosine, was another significant factor inhibiting protein digestion.

Deep eutectic solvent (DES) pretreatment and lignin regeneration for the development of a bamboo leaf-based bioplastic.

The excessive utilization of petroleum-based plastic products has led to a pervasive environmental and human health threat. In response, the adoption of bioplastics derived from biomass has emerged as the foremost alternative to conventional plastics, owing to their inherent biodegradability and sustainability. The present study demonstrates the preparation of a biodegradable and cost-effective lignocellulosic bioplastic by utilizing dissolving bamboo leaf powder with deep eutectic solvents (DES) and regenerating lignin in situ. The DES was synthesized through a one-step heating and stirring method using choline chloride (ChCl) and anhydrous oxalic acid. The crystallinity of the bioplastics is enhanced by DES pretreatment, thereby improving the internal structural order of the material. Moreover, lignin regeneration reduces the pore size within the bioplastics and contributes to a more compact internal structure. The prepared lignocellulosic bioplastics exhibit remarkable mechanical strength, with a tensile strength of 113MPa. Additionally, they demonstrate good water stability, as evidenced by a contact angle of 55.52°. Moreover, these bioplastics possess an exceptional biodegradability with a degradation rate exceeding 98% after 60days. This study presents an innovative approach for the high-value utilization of bamboo leaf resources.

Aggregate migration and self-organisation properties of asphalt mixtures during compaction process

The objective of this investigation is to analyze the migration behaviours and self-organisation properties of aggregate-asphalt particle system. The three-dimensional discrete element dynamic compaction model was established, and the accuracy and reliability were validated by self-developed particle migration tracking test. The evaluation indices of aggregate particles was measured to investigate the migration behaviours of aggregates and its evolution law. The self-organisation behaviours of aggregate-asphalt particle system were explored combined with the contact behaviours. The results indicate that the migration process of aggregate particles can be delimited into three stages of compaction degree lower than 50%, from 50% to 70%, and above 70%. The larger the aggregate size, the more significant the rotation migration. Under the combined effect of migration and contact, the coarse aggregates migrate to find stable contact points to self-organize the skeleton structure. Asphalt mortar fills the voids eliminated to self-organize the dense structure.

A sustainable and clean method for vanadium extraction from shale ore by suspension oxidation roasting: A comparative study of leaching behavior

Vanadium (V) is an important rare metal element that is widely applied in a variety of fields. It is necessary to develop an efficient method for the utilization of V-bearing shale ore. In this work, we investigated the mechanism of enhanced vanadium extraction from shale ore by suspension oxidation roasting (SOR) by comparing the leaching behavior between traditional direct acid leaching and SOR-acid leaching. After being roasted, the V leaching rate obviously increased from 60.33 % to 83.20 % while the H2SO4 dosage, leaching temperature, and leaching time decreased 20 wt%, 30 °C, and 5 h, respectively. The non-appearance of CaF2 alleviated environment pollution from wastewater. Roasting activation improved the chemical reaction activity and transformed the dense structure into a loose and porous structure which contributed to improving the diffusion rate of acid into particles and the solutions. Kinetic studies shown that SOR contributed to decrease the activation energy of leaching system and solid layer or solution boundary layer diffusion contributed to the control of roasted product leaching rate.

The potential of solid waste as a viable replacement for quartz sand in the ultra-high performance concrete: a comprehensive review

ABSTRACT Ultra-high performance concrete (UHPC) is renowned for its dense structure and exceptional mechanical properties, including durability. However, its widespread adoption is hindered by the high costs of essential fine aggregates like quartz sand and the associated environmental impact. Additionally, using industrial solid waste raises pollution concerns, contradicting global sustainability goals. Numerous studies have shown that it is feasible to produce eco-friendly UHPC with excellent performance by solid waste. This comprehensive review thoroughly investigates the workability, mechanical properties (including compressive strength, flexural strength and tensile strength), microstructure (encompassing pore structure and interfacial transition zone) and durability of UHPC incorporating solid waste in its production. The paper emphasizes the critical influence of factors, such as the solid waste substitution rate and the physical and chemical properties of solid waste. The paper also outlines the current application of UHPC with solid waste in pavement engineering and highlights the urgent need to address challenges such as high production costs, the lack of design standards and construction technique deficiencies, thereby emphasising the urgency surrounding the design and advancement of solid waste-incorporated UHPC in pavement engineering as it can reduce the environmental impact of traditional UHPC and improve the efficient use of solid waste.

Multi-confinement structured carbon dots with long room temperature phosphorescence lifetime and efficiency for sensing thiram residues assisted by copper ions.

Room temperature phosphorescent carbon dots(NCCDs@SiO2) were obtained by encapsulating hydrothermally synthesized CDs in a dense Si-O network structure after high-temperature calcination using silica as the matrix. Thiscan avoid the quenching effect of dissolved oxygen in water and has a phosphorescence lifetime of up to 2.41 s. Using the phosphorescence property of NCCDs@SiO2, a phosphorescence quenching sensor was developed for the sensitive and selective detection of thiram with the assistance of Cu2+. Cu2+-thiram complexesled to a rapid phosphorescence quenching of NCCDs@SiO2 within 30 s through the inner filter effect. The linear range of phosphorescence for thiram was 0.5-100 µM with a detection limit of 0.121 µM. Theproposed method was able to detect thiram in real samples and was validated by high-performance liquid chromatography (HPLC) confirmingthe potential of this phosphorescence sensing method for thiram detection. This work opens up a new avenue for the detection of thiram residues in fruits and vegetables and also provides a new idea for the design of a rapid detection platform using other room temperature phosphorescent materials.

Constraints on VHE gamma-ray emission of Flat Spectrum Radio Quasars with the MAGIC telescopes

Abstract Flat spectrum radio quasars (FSRQs) constitute a class of jetted active galaxies characterized by a very luminous accretion disk, prominent and rapidly moving line-emitting cloud structures (Broad Line Region, BLR), and a surrounding dense dust structure known as dusty torus. The intense radiation field of the accretion disk strongly determines the observational properties of FSRQs. While hundreds of such sources have been detected at GeV energies, only a handful of them exhibit emission in the very-high-energy (VHE, E ≳ 100 GeV) range. This study presents the results and interpretation derived from a cumulative observation period of 174 hours dedicated to nine FSRQs conducted with the MAGIC telescopes from 2008 to 2020. Our findings indicate no statistically significant (≥ 5 σ) signal for any of the studied sources, resulting in upper limits on the emission within the VHE energy range. In two of the sources, we derived quite stringent constraints on the γ-ray emission in the form of upper limits. Our analysis focuses on modeling the VHE emission of these two sources in search for hints of absorption signatures within the broad line region (BLR) radiation field. For these particular sources, constraints on the distance between the emission region and the central black hole are derived using a phenomenological model. Subsequently, these constraints are tested using a framework based on a leptonic model.

Automated Fabrication of Smart Strain Sensing Threads.

With favorable properties of stretchability, stitchability, and potential to be woven into a fabric, thread-based sensors have gained considerable interest for wearable devices for smart and connected health applications. To facilitate wearable applications, an easy and reliable way to fabricate these thread-based sensors with good performance and consistency is the key while manufacturing these smart threads. In this paper, we propose an automated thread-coating system that can fabricate thread-based strain sensors with controlled parameters. The platform uses integrated sensors for controlled manufacturing of the threads in a highly compact structure that consists of an innovative tension sensor and a closed-loop thermal management system. Using this new system, a sample thread with a gauge factor of 1.47 and tension sensitivity of 32.64 KΩ/N is prepared. Compared with hand-coated thread, the machine-fabricated thread shows much better sensitivity and consistency. The prepared strain sensor is made into a respiration sensor patch and a limb motion patch to demonstrate its application.

Anisotropic model observing pulsars from Neutron Star Interior Composition with modified Van der Waals equation of state

This paper is designed for heavy pulsars coming from the Neutron Star Interior Composition Explorer. The research model is describe by Einstein field equations for anisotropic fluid configuration with spherical symmetry. As per present perceptiveness, modified non-linear Van der Waals equation of state is used to relate physical variables. The continuity of inner and outer matter is obtained by comparing inner spacetime to outer Schwarzschild metric. The physical viability of this model is evaluated and further it is compared with observational data of pulsars PSR J0348+0432, PSR J0740+6620 and PSR J0030+0451. The model fulfils all physical and mathematical characteristics of the dense structure studies. It offers the factual proofs carried by evolution of celestial configurations. The working model presented here is physically viable and shows stable behaviour.

Alkali-Silica Reaction and Residual Mechanical Properties of High-Strength Mortar Containing Waste Glass Fine Aggregate and Supplementary Cementitious Materials

This paper presents the influence of supplementary cementitious materials (SCMs), such as fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), and waste glass fine aggregate (GA), on the alkali-silica reaction (ASR) in high-strength and normal-strength mortar using an accelerated mortar bar test (AMBT). Residual mechanical properties and scanning electron micrographs were used to assess the changes in the matrix. GA reduced the mechanical properties of both normal-strength (NGA_OPC) and high-strength mortars (HGA_OPC), contributing to a decline in overall performance. This phenomenon was a result of the slipping of the GA from the matrix owing to its smooth surface. However, the inclusion of reactive SF and GGBS in the HGA improved the slip phenomenon of the GA, leading to a significant enhancement in its mechanical properties. Following the ASR expansion measurement, HGA_OPC demonstrated an ASR expansion rate approximately three times higher than that of NGA_OPC. This was attributed to the dense structure of HGA_OPC, which resulted in greater expansion than that of NGA_OPC. However, with the incorporation of SCMs into both HGA and NGA, a significant reduction in ASR expansion was observed. This was attributed to the delayed ASR of GA due to alkali activation or the pozzolanic reaction of the SCMs. Continuous exposure to the AMBT environment can lead to the destruction of GA. This was caused by the inner ASR that originated from the surface crack of the GA, which resulted in a reduction in the flexural strength of the mortar. The HGA with SF exhibited the highest resistance to ASR expansion and residual mechanical properties’ degradation. Therefore, various durability and long-term performance-monitoring studies on ultra-high-performance concrete or high-strength cementitious composites with very high SF contents and GA can be conducted.

Research on the stiffness characteristics and contact status of matched angular contact ball bearings considering the effect of varying spatial position of rolling ball

In engineering practice, bearings used as support components are usually installed in pairs in various rotating machines. The mechanical and contact characteristics of bearings play a crucial role in determining the operational accuracy, safety performance and stability of equipment. Numerous studies focused on single bearings have been reported form diffident aspects for enhancing service performance. However, the literature reports on the matched bearings are scarce due to the mutual coupling of rolling elements and the extremely complex stress conditions. Especially the stiffness fluctuation and internal contact status affected by the ball position are difficult to be observed and tested experimentally because of the complex and compact structure, which significantly impacts the safe and reliable operation of rotating machines. To overcome the above shortcomings, this paper investigates the effect of ball position on the stiffness characteristics and contact status of matched angular contact ball bearings based on the coordinate matrix transformation approach and Jones’ statics model. Then, the stiffness results of published literature are used as a benchmark to validate the accuracy of solution method of this paper. Finally, 7206B bearings with different installing forms are used as a numerical example to reveal the effect of ball position on the stiffness characteristics and contact status of matched angular contact ball bearings under different working conditions. The study provides a scientific guidance to investigate the mechanical characteristics and contact mechanism of multi-bearing system.

Nucleus-Spike 3D Hierarchical Superstructures via a Lecithin-Mediated Biomineralization Approach.

3D hierarchical superstructures (3DHSs) are key products of nature's evolution and have raised wide interest. However, the preparation of 3DHSs composed of building blocks with different structures is rarely reported, and regulating their structural parameters is challenging. Herein, a simple lecithin-mediated biomineralization approach is reported for the first time to prepare gold 3DHSs composed of 0D nucleus and 1D protruding dendritic spikes. It is demonstrated that a hydrophobic complex by coordination of disulfiram (DSF) with a share of chloroauric acid is the key to forming the 3DHSs. Under the lecithin mediation, chloroauric acid is first reduced to form the 0D nucleus, followed by the spike growth through the reduction of the hydrophobic complex. The prepared 3DHSs possess well-defined morphology with a spike length of ≈95nm. Notably, the hierarchical spike density is systematically manipulated from 38.9% to 74.3% by controlling DSF concentrations. Moreover, the spike diameter is regulated from 9.2 to 12.9nm by selecting different lecithin concentrations to tune the biomineralization process. Finite-difference time-domain (FDTD) simulations reveal that the spikes form "hot spots". The dense spike structure endows the 3DHSs with sound performance in surface-enhanced Raman scattering (SERS) applications.

Investigation of the Influence of the Oxygen Flow Rate on the Mechanical, Structural and Operational Properties of 86WC-10Co-4Cr Coatings, as Determined Using the High-Velocity Oxyfuel Spraying Method

The structural-phase composition and tribological and performance properties of coatings based on an 86WC-10Co-4Cr composition obtained by the HVOF method at varying (150 L/min, 170 L/min, 190 L/min) oxygen flow rates were studied. The results showed that the coefficient of friction of coatings in gear oil remained almost unchanged with the variation in oxygen flow rate. However, microhardness increased significantly with an increasing oxygen flow rate, reaching a maximum at 190 L/min. An increasing oxygen flow rate was also accompanied by an increase in roughness and coating thickness, with a decrease in porosity, particularly notable at 190 L/min. Adhesion strength reached the maximum values for the A2 and A3 coatings under high loads. The phase composition of the coatings included WC, W2C and CoO phases irrespective of the oxygen flow rate, and their microstructure was characterized by a more homogeneous and dense structure. Thus, this study confirmed that the optimal oxygen flow rate for achieving an improved performance and tribological characteristics of 86WC-10Co-4Cr coatings is 190 L/min.

Compact design of universal gates with non-aligned gate technology and assessment of its performance in a TCAD Environment

ABSTRACT This paper proposes a technology computer-aided design (TCAD) of a compact single-device NAND and NOR logic gates in 215 nm device length along with speed and power performance results. The universal gates are designed with non-aligned double gate technology, and this helps to reduce the transistor count, giving a compact design structure. The static characteristics and input pattern sensitivity of the NAND and NOR structures are investigated in this work. By using graphical method, the optimal supply voltage of the universal gates was determined. The optimal supply voltage of the NAND gate and NOR gate was 0.9 V and 0.84 V, respectively, at an input frequency of 1 GHz. Further, the device scalability of the proposed structures was analysed. When compared to the past work, the proposed NAND gate and NOR gate improves delay performance by 25.02% and 35.63%, respectively. Additionally, a reduction of 10% and 16% in its supply voltage is achieved. Therefore, the proposed gate has potential to operate at higher frequency with reduced supply voltage, making them suitable in circuit applications.

Slowly rotating charged Bardeen stellar structure

This paper is devoted to investigating the dynamics of charged stellar structures with Bardeen exterior geometry. For this purpose, firstly a proposed metric coefficient is utilized, which is defined as a=N1+2hr2m/2. Here, h and N are arbitrary constants determined from matching conditions and m is a positive integer. The pressure and density profiles are found to be positive and monotonically decreasing, with maximum values occurring at the center. Furthermore, the energy conditions and causality conditions are satisfied, and the adiabatic index falls within an acceptable range. The second part of the paper focuses on the dynamics of rotating stars. Numerical values for relevant parameters are assumed to obtain the masses and radii of stars within the desired range. Five different compact stars, namely, VelaX−1, CenX−3, 4U1820−30, 4U1608−52, and PSR1903+327, are considered. The behavior of the moment of inertia of the sphere against the solar mass is investigated, revealing an increase in the moment of inertia with an increase in solar mass. Furthermore, the relationships of mass and energy density against the radius of the compact structure exhibit natural behavior, supporting the acceptability of the analysis. Overall, the study supports the existence of realistic charged compact structures with Bardeen exterior geometry.

Lifespan Evaluation for a Standard RV Reducer based on Fatigue Strength Theory

Rotate vector (RV) reducers are the two-stage deceleration device comprising involute and cycloid-pin gear transmission mechanisms. As the typical deceleration elements, they are widely applied in industrial robots, digitally controlled machine tools and automation fields due to their compact structure and high precision. However, a reducer may lose precision after a long-term operation. Moreover, pitting and metal peeling of internal components may also occur, leading to a fatigue failure. Therefore, it is necessary to conduct investigations on lifespan evaluation for RV reducers. In this study, the CRV-80E reducer is taken as the research object. Firstly, according to its transmission characteristics, the lifespan evaluation model for a standard RV reducer is established based on fatigue strength theory and Palmgren-Miner linear cumulative damage law, with the internal crankshaft bearing is considered as the key component. Then, the simulations are carried out on crankshaft bearing by the ANSYS Workbench and SKF SimPro. The contact stress, deformation on bearing rollers, and the rated lifespan of the reducer are simulated. Finally, the accelerated life test is conducted on an RV reducer by increasing the external load with the positioning precision as an output and criterion. After the test, the reducer is disassembled, and metal peeling failure is observed on the crankshaft bearing while other parts are relatively intact. The test results validate the feasibility and accuracy of the service life evaluation model and simulation analysis. This study provides a new research approach for researchers and manufacturers and a design reference for engineers to improve the lifespan of RV reducers by optimizing crankshaft bearings, which have a certain academic value.