Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Chenglong Wu, Hao Li, Ruizhe Sun et al.

Md Tarikal Nasir, Qingchao Fang, Hanqing Yin et al.

Electrochemical reduction of nitrate ( ${\text{NO}}_3^ - $ ) to ammonia is a sustainable strategy to convert the pollutant nitrate into high-valued chemicals. Currently, the nitrate reduction reaction (NO _3 RR) is mainly based on transition metal catalysts. Here, by using density functional theory calculations, we studied six p -block atoms doped in 2D boron nitride (BN) monolayers for the NO _3 RR. Our results reveal that the doped BN monolayers are thermodynamically stable, and that ${\text{NO}}_3^ - $ can be strongly absorbed and activated on the In@BN, Si@BN, Ge@BN and Sn@BN monolayers. BN is a promising substrate support for catalysts due to high stability and thermal resistance. Among the six doped BN monolayers, In@BN and Sn@BN exhibit exceptional NO _3 RR performance with a limiting potential of only −0.30 V. Additionally, the hydrogen evolution reaction can be completely suppressed due to the weak adsorption of protons on the catalyst surfaces. Our work provides a new avenue on designing p -block atom-based catalyst’s for efficient NO _3 RR.

Hongyu Wu, Wenliang Shi, Ri He et al.

Abstract Determining thermodynamic properties in disordered systems remains a formidable challenge because of the difficulty in incorporating nuclear quantum effects into large‐scale and nonperiodic atomic simulations. In this study, we employ a machine learning deep potential model in conjunction with the quantum thermal bath method, enabling machine learning molecular dynamics to simulate thermodynamic quantities of liquid materials with satisfactory accuracy without significantly increasing computational costs. Using this approach, we accurately calculate the variations in various thermodynamic quantities of liquid metal gallium at temperatures ranging from zero to room temperature. The calculated thermodynamic properties accurately capture the solid‐liquid phase transition behavior of gallium, whereas classical molecular dynamics methods fail to reproduce realistic results. Through this approach, we offer a potential method for accurately calculating the thermodynamic properties of liquids and other disordered systems.

C. Chen, J. Li, J. Li et al.

<p>Pedestrian detection is one of the most widely applied tasks in industrial computer vision. It encapsulates three core challenges of object detection: detecting small objects, handling heavy occlusion, and balancing speed and accuracy for deployment on mobile devices. In targeting scenarios relating to the Internet of Things (IoT), we propose a dedicated lightweight pedestrian detector that is robust to occlusions. First, we redesign the decoupled prediction head with a hierarchical structure, separating classification confidence estimation from bounding box regression. We then decode the offsets from the regression branch, extract features from high-confidence predictions, and fuse these with classification feature maps to enhance the local reliability of semantic features. Furthermore, we introduce a label-dynamic matching strategy that increases the number of high-quality positive samples, particularly improving matching for small and occluded objects. Finally, an optimized knowledge distillation framework significantly boosts the prediction accuracy of the compact model, facilitating deployment on edge devices. Experimental results on the CrowdHuman test set show that our proposed approach achieves comparable accuracy to the baseline (53.8 %) with an inference latency of only 7.1 ms – 281.7 % faster than the baseline.</p>

Jie Gao, Guodong Yang, Wanwen Huang et al.

By forming alloys with Li ions, silicon (Si) can possess an energy capacity ten times that of graphite anodes, making it a promising candidate for the next generation anode materials for lithium-ion batteries. However, the large volumetric changes of Si during the lithiation/delithiation process result in unstable electrochemical cycling performance, and the deficiencies in electrical and ionic conductivity limit its rate performance, thereby constraining the large-scale application of Si-based anode. Due to its strong interaction with Si particles and its convenience in constructing doped carbon layers and carbon layers with special structures, polymers are regarded as low-cost (for example, the price of lignin is as low as 200–600 $/ton) and effective carbon sources to prepare core-shell structured Si@C composite materials and optimize the shortcomings of Si-based anodes.In this review, we first discuss surface modification methods for Si particles aimed at enhancing the adhesion to polymers and effectively improving the dispersibility of Si nanoparticles in polymers. Subsequently, the roles and methods for improving the electronic/ionic conductivity and structural stability of carbon layers, including doping and the construction of various special structures, are summarized and compared. These advancements position Si@C composites as viable candidates for next-generation high-energy batteries. Finally, the prospects for Si anodes coated with polymer-derived carbon layers are proposed.

Wenzhuo Ma, Libo Yan, Bohumil Kasal

This study investigated the bond properties between flax fibre reinforced polymer (FFRP) mesh and various cementitious matrices, examining the impact of incorporating medium-sized recycled aggregates (2 – 8 mm). Enhancement strategies included modifying the FFRP surface with rice husk ash (RHA) and incorporating RHA into the cementitious matrix. Pull-out and uniaxial tensile tests were performed on FFRP reinforced mortar, FFRP reinforced recycled aggregate concrete (RAC), RAC reinforced with RHA-modified FFRP and RAC (containing RHA) reinforced with RHA-modified FFRP. The results showed that FFRP surface modification with RHA significantly improved bond strength, by 32 % compared to pulling normal FFRP from RAC. This was attributed to increased surface roughness of FFRP, enhanced chemical bonding due to pozzolanic reaction of RHA, and improved interfacial transition zone resulting from increased wettability and decreased water absorption ratio of the treated FFRP. Additionally, the inclusion of medium-sized recycled aggregates mitigated debonding by enhancing mechanical interlocking with the FFRP mesh. Compared to FFRP reinforced mortar, FFRP reinforced RAC and RHA-modified FFRP reinforced RAC exhibited increased strain capacity and refined crack propagation, indicating improved stress distribution. However, the enhanced anchoring reduced tensile strength by restricting the full utilisation of strain capacity in the post-cracking phase. These findings highlight the potential of surface modification of reinforcement with supplementary cementitious materials and the incorporation of medium recycled aggregates in the matrix to enhance bond performance and optimise the mechanical behaviour of cementitious composites.

Yang Yaqian, Xing Weiwei, Ding Leilei et al.

The effects of 0.000 1%， 0.001 8% and 0.003 7% S content on the solidification characteristics of K417G alloy were studied by isothermal solidification experiment in the temperature range of 1 340-1 230 ℃. The results show that S can reduce the solidus temperature of the alloy and enlarge the solid-liquid two phase region. When the S content increases from 0.000 1% to 0.003 7%， the solidus temperature of the alloy decreases from 1 255 ℃ to 1 245 ℃. During the solidification process， the S element segregates in the liquid phase and precipitates out as the Y phase in the final solidification zone. And S promotes the enrichment of Al and Cr elements at the solid-liquid interface. At the same isothermal temperature， the increase of S content promotes the increase of the volume fraction of MC carbide， γ+γ΄ eutectic and Y phase， and has little effect on the morphology and precipitation temperature of MC carbide and γ+γ΄ eutectic， but the precipitation temperature of the Y phase is increased from 1 230 ℃ to 1 240 ℃.

Shunhong Zhang, Xiaoyin Li, Huisheng Zhang et al.

Abstract Two-dimensional magnets have been discovered recently as a new class of quantum matter exhibiting a broad wealth of exotic phenomena, including notably various topological excitations rooted in emergent exchange couplings between the localized magnetic moments. By analyzing the anisotropies in the single-ion magnetization and two-body exchange couplings obtained from first-principles calculations, we reveal coexistence of both giant Dzyaloshinskii–Moriya interaction and strong anisotropic XXZ-type biquadratic coupling in a recently predicted monolayer CrMnI6 magnet. The former is induced by the spontaneous in-plane inversion symmetry breaking in the bipartite system, the latter is inherently tied to the distinct high-spin state of the Mn sublattice, while the large magnitudes of both stem from the significant spin-orbit coupling. Next, we use atomistic magnetics simulations to demonstrate the vital role of Dzyaloshinskii–Moriya interaction in harboring topological bimeronic excitations, and show that the biquadratic coupling favors a Berezinskii–Kosterlitz–Thouless-like transition as the system reduces its temperature from the paramagnetic phase. These findings substantially enrich our understanding of the microscopic couplings in 2D magnets, with appealing application potentials.

Ali Payami Golhin, Chaman Srivastava, Are Strandlie et al.

As a result of the associated costs and environmental impacts, Material Jetting (MJT) plays a limited role in Additive Manufacturing (AM). Research on the durability and long-term performance of MJT objects by evaluating their appearance is lacking. The objective of this study is to investigate the effect of aging on the color and the physico-mechanical performance of MJT parts. This work examines the influence of production settings on objects subjected to a total of 103days of accelerated aging. The studied Printing Primary Parameters (PPPs) were resin color, build platform position (swath), and finishing configurations. The results indicated the response of the studied PPP according to the aging time was non-linear due to the dynamic appearance response to aging time. VeroBlackPlus and VeroCyan photo resins demonstrated superior color fidelity through aging by a color difference of less than 10. Based on Taguchi and Redundancy Analysis (RDA), mechanical and physicochemical properties varied the most after 58 days of accelerated aging, with elastic modulus retention up to 149.21% and Glass Transition temperature (Tg) up to 116.6%. This study demonstrates the importance of considering long-term performance during the design process of AM products, depending on the intended application and service conditions.

Y. Okamura, K. Shoriki, Y. Nomura et al.

Abstract The kagome-lattice materials promise emergence of Dirac fermions thanks to the special lattice geometry, which potentially realizes intriguing quantum topological states through various many-body interactions. The low-energy electromagnetic phenomena arising from such the Dirac fermions are expected to show the remarkable enhancement and, in certain conditions, to approach the universal responses, which, however, have remained elusive experimentally. Here, we show the resonantly enhanced magneto-optical response of massive Dirac fermions in kagome-lattice magnet TbMn6Sn6. The infrared magneto-optical spectroscopy reveals that the interband transition on massive Dirac bands significantly contributes to the observed resonance in the optical Hall conductivity. The analytical model expressed by a few band parameters reproduces the spectral characteristics of the resonance, which robustly produces almost 20 % of the quantized Hall conductance per one kagome layer even at room temperature. Our findings establish the general optical response of massive Dirac fermions, which is closely related to the universal electrodynamics in quantum anomalous Hall state.

Enric Perarnau Ollé, Jasmina Casals‐Terré, Joan Antoni López Martínez et al.

Abstract Polymeric materials are widely employed for monitoring volatile organic compounds (VOCs). Compared to other sensitive materials, polymers can provide a certain degree of selectivity, based on their chemical affinity with organic solvents. The addition of conductive nanoparticles within the polymer layer is a common practice in recent years to improve the sensitivity of these materials. However, it is still unclear the effect that the nanoparticles have on the selectivity of the polymer membrane and vice versa. The current work proposes a methodology based on the Hansen solubility parameters, for assessing the selectivity of both pristine and hybrid polymer nanocomposites. The impedance response of thin polydimethylsiloxane (PDMS) films is compared to the response of hybrid polymer films, based on the addition of multi‐walled carbon nanotubes (MWCNTs). With the addition of just 1 wt.% of MWCNTs, fabricated sensors showcased a significant improvement in sensitivity, faster response times, as well as enhanced classification of non‐polar analytes (>22% increase) compared to single PDMS layers. The methodology proposed in this work can be employed in the future to assess and predict the selectivity of polymers in single or array‐based gas sensors, microfluidic channels, and other analytical devices for the purpose of VOCs discrimination.

Gokul Gopinath, Pavithra Shanmugaraj, M. Sasikumar et al.

The growing demand for environmentally friendly materials in energy storage has led to a significant focus on using biopolymer membranes derived from renewable resources. This study focuses on creating eco-friendly biopolymer electrolytes for Electric Double Layer Capacitors (EDLC) by blending Magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) with Cellulose Acetate (CA) through a solution casting method. To enhance performance, plasticized membranes were developed using nontoxic Poly(ethylene glycol) (PEG) as a plasticizer. The addition of PEG reduced membrane crystallinity, as shown by X-ray diffraction (XRD). Fourier Transform Infrared (FTIR) spectroscopy indicated complexation among electrolyte constituents. The optimal composition, containing 25 wt% PEG, exhibited the highest ion conductivity (3.76 × 10−4 S/cm) according to Electrochemical Impedance Spectroscopy (EIS). EIS data allowed determination of important ion transport parameters, such as Diffusion Coefficient, Ionic Mobility, and Carrier Density. The EDLC device showed a Specific Capacitance (Csp) of 13.14 F/g at a scan rate of 5 mV/s, with excellent stability (3.2 V) in Linear Sweep Voltammetry (LSV). Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) tests confirmed no redox processes, yielding a Csp of 12.94 F/g at 0.1 A/g. The EDLC device demonstrated exceptional cyclic stability, high coulombic efficiency, and maintained consistent results in terms of Power Density (Pd) and Energy Density (Ed) over 1000 cycles. Incorporating PEG into biopolymer membranes enhances the electrochemical energy storage of EDLC devices, contributing to sustainable energy storage solutions.

Jason Mulderrig, Bin Li, Nikolaos Bouklas

Antonios Kanellopoulos, Magdalini Theodoridou, Michael Harbottle et al.

Kai Zhang, Wenjuan Yang, Zaochuan Ge et al.

Abstract The sluggish full visible light response of organic supramolecular catalysts is a challenge that greatly restricts their development in the photocatalytic field. Herein, we successfully fabricated a K, Cl‐codoped Bi2WO6/perylene‐diimide(PDI) catalyst with a novel, general, and facile ultrasound assisted water bath heating method. The UV adsorption onset of K, Cl‐codoped Bi2WO6/PDI is redshifted from 750 to 760 nm compared with that of the heterojunction of Bi2WO6/PDI. Under visible light, the phenol is thoroughly mineralized into CO2 and H2O, and the phenol degradation rate was three times higher than that of pure Bi2WO6/PDI. The electrons transfer from PDI to K‐ and Cl‐codoped Bi2WO6/PDI according to the charge density difference calculation. The built‐in potential of K‐ and Cl‐codoped Bi2WO6/PDI could increase from 2.09 to 5.54 eV. The excellent full visible light spectrum photooxidation of phenol is attributed to the suitably strong built‐in potential at the heterojunction between PDI and K, Cl‐codoped Bi2WO6.

Cheng Yu-qiang, Shuai Chang-geng, Gao Hua

In this article, the parametric model for the stiffness characteristic and burst pressure of cord-reinforced air spring with winding formation is developed. Based on the non-geostrophic winding model and the assumption of cord cross-stability, the cord winding trajectory model of the capsule is established. Then, the anisotropic and nonlinear mechanics model of the capsule with complex cord winding trajectory variation characteristics is constructed by the classical thin-shell theory. The capsule state vector is solved by the extended homogeneous capacity precision integration method. Due to the complex coupling relationship between the capsule state vector and the internal air pressure, the stiffness characteristic is solved by the iterative integration method. The burst pressure of the air spring is solved by the Tsai–Hill strength theory. Eventually, the accuracy and reliability of the proposed method are verified by the experimental results. The effects of the material properties, winding parameters, and geometric structure parameters on stiffness characteristics and burst pressure are discussed. The results of this article provide an important theoretical basis for the performance design of cord-reinforced air springs with winding formation.

Youqiang Huang, Yingjie Zhao, Yuan Liu et al.

At present, the shortage of potable water is still a critical issue. The emerging of solar-driven evaporation technique offers a promising way to solve freshwater scarcity. However, developing highly efficient evaporation system is still a challenge. Herein, this work developed two-dimensional heterostructure nanosheets as the photothermal agent. We used the WSe2 nanosheets to enhance the absorption of graphene and facilitate the heat localization due to its higher visible light absorption and ultralow thermal conductivity. And graphene provided the low surface reflection and a broad absorption spectrum. Moreover, the enhanced near infrared photothermal conversion of the heterostructure nanosheets is realized to be 41.4% higher than some previous works by introducing lanthanide ions. A series of experiments are performed to determine its heterostructure. Besides, the interfacial evaporation system has been constructed based on as-prepared nanosheets, exhibiting excellent solar-to-heat efficiency of 91.8% and water evaporation rate of 1.672 kg m−2h−1 under stimulated 1 sun irradiation. It is suggested that developed nanosheets have the potential application for highly effective solar-driven evaporation.

A. F. Qasrawi, Hadeel M. Zyoud

In this work, the optical dynamics and the structural properties of the zinc phthalocyanine which are coated onto 150 nm thick Au substrates are studied by the X-ray diffraction and optical spectrophotometry techniques. The Au/ZnPc interfaces appears to be strongly affected by the large lattice mismatches at the interface. It is observed that the coating ZnPc onto Au substrates increases the light absorbability by 4.7 and 128.2 times in the visible and infrared regions of light, respectively. Au substrates activated the free carrier absorption mechanism in the ZnPc thin films in the infrared range of light. In addition, the transparent Au substrates forced narrowing the energy band gap in both of the Q and B bands. It also increased the dielectric constant value by ~3.5 times in the IR range. The enhancements in the optical properties of ZnPc that resulted from the thin Au substrates make the ZnPc more suitable for optoelectronic, nonlinear optical applications and for electromagnetic energy storage in the infrared range of light.

Hassan Al-Nageim, Monower Sadique