Bridging Effect Research Articles

Thermal analysis of the window-wall interface for renovation of historical buildings

Due to the long time since their construction, some old buildings have experienced a decline in performance and do not meet contemporary requirements. Retrofitting methods, as opposed to demolition and reconstruction, are considered a more cost-effective and energy-efficient approach, particularly applicable to historical buildings with conservation significance. Exterior windows account for a significant amount of heat loss within the building envelope, but it is a challenge to improve its performance while retaining the historical appearance of the building when retrofitting. In this paper, a new design of the window-wall interface structure was proposed, which facilitated the incorporation of additional thermal insulation materials and mitigated the thermal bridge effect at the joint between the window frame and the wall. Comparative analysis with existing window-wall interface structures revealed the superior thermal performance of the proposed structure, with less heat transfer as well as smaller surfaces at risk of condensation. The structure was first implemented in a renovation project in Nanjing, providing an innovative approach for future exterior window renovations of historical buildings.

Acoustic emission for exploring loading rate impact on type I fracture mechanism of engineering cementitious composites after subjected to sub-high temperature

To investigate the crack extension mechanism of engineered cementitious composite (ECC) after sub-high temperature. This paper studies the mode I fracture properties of ECC after sub-high temperatures (20 °C, 100 °C, 200 °C) at three strain rates (2 × 10-5s-1,10-4s-1,10-3s-1), and monitors the damage process in real-time by acoustic emission (AE) technology. Crack evolution and failure modes of ECC during loading are investigated by AE signal parameters. The results show that compared with 20 °C, the fracture energy of ECC increases after 100 °C, and decreases after 200 °C. The damage characteristics of ECC after 100 °C are similar to those at room temperature. Due to the bridging effect of the PVA fibers, their internal microcracks spread around from the tip of the prefabricated cracks. The percentage of shear type cracks gradually increases. The damage types are dominated by matrix cracking and fiber pull-out. While the PVA fibers deteriorated after 200 °C, the damage within the ECC was more concentrated, and the width of the fracture process zone was reduced. The crack types were dominated by tensile cracks. The failure mode was dominated by fiber pull-off and matrix cracking. Construction of an AE energy-based damage model. The b-value can reflect the whole process of crack evolution from multi-cracks to main cracks within ECC.

Integrated comprehensive protection coating achieved by ligand engineering modulated MXene@LDH heterojunction with anti-corrosion, electromagnetic wave absorption and fire safety

Harsh marine environment poses great threat to the service of offshore equipment, and the development of multifunctional coatings is crucially important at present. Herein, layered double hydroxides (LDH) was loaded onto transition metal carbides (MXene) to construct MXene@LDH heterojunction via electrostatic self-assembly strategy. Supramolecular ligand (TT) formed by tannic acid and 4′-(4-Boronatophenyl)[2,2′:6′,2'']terpyridine modulated the compatibility of MXene@LDH in epoxy resin (EP) based on ligand engineering strategies, forming TT-MXene@LDH hybridized filler. EP doped TT-MXene@LDH coating (TT-MXene@LDH/EP) exhibited outstanding anti-corrosion, electromagnetic wave absorption (EWA) and flame retardant performance. The charge transfer resistance and minimum reflection loss of TT-MXene@LDH/EP were reached at 4.09×1010 Ω⋅cm2 and −37.05 dB. The total heat release and total smoke production of TT-MXene@ LDH/EP were reduced 24.5 % and 47.2 % in combustion. Thermal conductivity of composite sample was also enhanced with the bridging effect of TT-MXene@LDH. Summarily, prepared comprehensive protective coating with anti-corrosion, EWA and fire safety provides a promising candidate for offshore equipment in harsh environments.

Surgical outcomes of anterior column reconstruction for spinal fractures caused by minor trauma-preoperative examination of the number of intervertebral bone bridges is key to obtaining good bone fusion-

BackgroundTo achieve good bone fusion in anterior column reconstruction for vertebral fractures, not only bone mineral density (BMD) and bone metabolism markers but also lever arms due to bone bridging between vertebral bodies should be evaluated. However, until now, no lever arm index has been devised. Therefore, we believe that the maximum number of vertebral bodies that are bony and cross-linked with the contiguous adjacent vertebrae (maxVB) can be used as a measure for lever arms. The purpose of this study is to investigate the surgical outcomes of anterior column reconstruction for spinal fractures and to determine the effect of bone bridging between vertebral bodies on the rate of bone fusion using the maxVB as an indicator of the length of the lever arm.MethodsThe clinical data of 81 patients who underwent anterior column reconstruction for spinal fracture between 2014 and 2022 were evaluated. The bone fusion rate, back pain score, between the maxVB = 0 and the maxVB ≥ 2 patients were adjusted for confounding factors (age, smoking history, diabetes mellitus history, BMD, osteoporosis drugs, surgical technique, number of fixed vertebrae, materials used for the anterior props, etc.) and analysed with multivariate or multiple regression analyses. The bone healing rate and incidence of postoperative back pain were compared among the three groups (maxVB = 0, 2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\leqq$$\\end{document}maxVB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\leqq$$\\end{document}8, maxVB ≧ 9) and divided by the maxVB after adjusting for confounding factors.ResultsPatients with a maxVB ≥ 2 had a significantly higher bone fusion rate (p < 0.01) and postoperative back pain score (p < 0.01) than those with a maxVB = 0. Among the three groups, the bone fusion rate and back pain score were significantly higher in the 2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\leqq$$\\end{document}maxVB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\leqq$$\\end{document}8 group (p = 0.01, p < 0.01).ConclusionsExamination of the maxVB as an indicator of the use of a lever arm is beneficial for anterior column reconstruction for vertebral fractures. Patients with no intervertebral bone bridging or a high number of bone bridges are in more need of measures to promote bone fusion than patients with a moderate number of bone bridges are.

Seismic performance and flexural strength prediction of high-strength bar reinforced UHPFRC walls under high axial load ratio

A new-type shear wall built with high-strength reinforcement and ultra-high performance fiber reinforced concrete (UHPFRC) is proposed in this paper, aiming to solve the problem of too large cross-section size of bottom shear wall members of high-rise and super high-rise buildings. Four UHPFRC wall specimens built with high-strength reinforcement were tested under cyclic loading to examine the influence of the parameters of fiber volume fractions (0 vs. 1.5% vs. 2.5%) and the spaces of horizontal distribution reinforcing bars (150 mm vs. 300 mm) on the seismic performance. In addition, a calculation method of flexural strength of UHPFRC shear wall is established. The research results show that: the UHPC wall specimen without fibers failed in the axial compression brittle mode, and the UHPFRC wall specimens with fibers failed in flexure-dominated ductile mode. The bridging effect of steel fibers at the cracks kept the integrity of the UHPFRC. The drift ratio capacities of the UHPFRC wall specimens under high axial compression ratio of 0.5 were 3.56%. Increasing the fiber volume fractions can improve the strength, initial stiffness, and cumulative energy consumption of the wall specimens, reduce the damage degree of the UHPFRC at the toes of the wall specimens, and can also reduce the reinforcement ratio of horizontal reinforcement without influence on the seismic performance. The proposed method of flexural strength of UHPFC walls shows reasonable prediction accuracy.

Revealing the effect of bridges in the multi-filamentary Bi-2212 wires

As the excellent current carrying capacity in ultra-high magnetic fields, Bi-2212(Bi2Sr2CaCu2O8+x ) has attracted much attention. In view of the unique nature of Bi-2212, high-temperature heat treatment is highly needed for the formation of the continuous textured structure in the multi-filamentary Bi-2212 wire. In the meanwhile, bridges between filaments can also be produced in the heat treatment process, which brings structural changes in the wires. However, the mechanism of the effect of the bridges is yet to be understood. In this work, systematical research was carried out on the multi-filamentary Bi-2212 wire for the effect mechanism. Based on the results of the four-probe method and the magnetic moment results, inferiority in Ic combined with a larger magnetic moment at high magnetic fields was detected in samples that have a large number of bridges. Further analysis indicates the inferiority in Ic can be attributed to the reduced cross-sectional area of the filaments and the inferiority in the quality of texture on the basis of results of a series of structural characterizations.

Utilization of composite particles with customizable cross-linked lignin patches for dental cleansing

Lignin, a natural polyphenol polymer, is a biocompatible, cost-effective and accessible material. To fully utilize the benefits of lignin, it is crucial to transform its complex macromolecules into nanoscale particles in a single solvent. In this research, an assembly-mediated internal cross-linking method in single solvent was proposed to manufacture cross-linked lignin colloidal particles with nanoscale particle size controlled to be around 50 nm. Then, cross-linked lignin composite particles with a unique “patchy” structure for dental cleansing were obtained by rapidly grafting the cross-linked lignin colloidal particles onto the surface of silica microspheres through the bridging effect of silane coupling agent. The resulting composite particles have rivets with adjustable hardness, significantly lower than traditional abrasives like silica in both hardness and modulus. Through the group cleansing behavior of soft interlocking, a breakthrough has been achieved in the high solid content agglomeration friction mode of traditional abrasives, which effectively reduces tooth wear and exhibits an excellent plaque removal effect.

Upcycling of End-of-Life-Vehicle (ELV) plastics as a replacement for natural fine aggregate in concrete

End-of-life vehicle (ELV) plastics pose technical challenges in conventional recycling due to their diverse polymer compositions. Consequently, landfilling remains the prevailing disposal method. This study explores an innovative approach by upcycling ELV plastics as a substitute for natural sand in concrete. The study investigates the physical, mechanical and economic performance of ELV plastic-containing concrete. Plastic aggregates were prepared from real-world ELV plastics, featuring particle sizes below 4.75 mm, with over 90 % falling within the range of 1.18–4.75 mm. The research involves replacing natural sand with ELV plastics at varying volumes (0 %, 15 %, 25 %, 35 %, and 40 %) and examines the effect of sand replacement on various concrete properties. The results suggest that as the replacement ratio increases, the workability, density, and strength of concrete decrease. However, the 28-day compressive strength of concrete at the maximum replacement rate of 40 % was found to be 39 MPa, which suffices for certain non-structural strength applications, such as traffic routes, shared-use paths, local streets and curbs. In addition, compared to previous studies using mixed commodity plastics, ELV plastics lead to significantly lower strength reductions at high replacement ratios. Scanning Electron Microscopy (SEM) analysis reveals a distinctive rough and fibrous aggregate morphology, which enhances physical binding and provides bridging effects within the concrete matrix, potentially mitigating strength loss. Moreover, the economic analysis highlights a significant potential to commercialize ELV plastics for concrete applications. This study demonstrates that ELV plastics can be effectively used at high replacement rates (up to 40 % by volume) in non-structural applications.

Study on shrinkage and creep effect of steel truss-stiffened continuous rigid frame bridge considering variable temperature and relative humidity

In this study, indoor-outdoor comparison tests of shrinkage and creep were carried out in northwest China. The experimental results were compared with commonly used models of shrinkage and creep, some of which have adapted different methods for temperature and humidity correction. A finite element model for a continuous rigid-frame bridge with steel truss bracing was established. The calculated values from different shrinkage and creep models were then compared with the measured deflection values. An analysis was conducted to determine the influence of variable temperature and humidity on the long-term mechanical behavior of the steel truss-stiffened continuous rigid-frame bridge.The results show that when the concrete reaches the age of one year, the creep coefficient for the outdoor environment is 18.5% smaller than that in the indoor environment, while the outdoor shrinkage strain is 16.0% smaller. The CEB 90 model agrees best with the indoor test results. The corrected shrinkage and creep model (CSCM) is the closest to the outdoor test results, and the fib2010 model ranked second. The predicted values from CSCM exhibit the best agreement with the measured deflection values after the bridge completion. The CEB 90 model's predicted values for deflection of the main girder, longitudinal displacement of the pier, the maximum stress in steel trusses, and prestressing loss are lower than those in the CSCM after 20 years of construction, indicating that the influence of temperature and relative humidity variations on shrinkage and creep effect of the bridge can not be negligible.

Synergistic enhancement in mechanical properties of graphene/MWCNT reinforced Polyaryletherketone – carbon fiber multi-scale composites: Experimental studies and finite element analysis

This investigation focuses on the synergistic performance improvement in graphene/MWCNT reinforced Polyaryletherketone (PAEK) - carbon fiber (CF) multi-scale composites. FTIR revealed the chemical interactions while HRTEM, XRD and 3D X-ray microscopy gave insight into nanofiller dispersion and microstructural features. The functional groups on nanofillers along with structural features integrated various components of the multi-scale composites by formation of graphene/MWCNT/CF complex network that provided larger interfacial area, bridging effect and physico-chemical interaction with PAEK while restricting its segmental mobility. Multi-scale composites displayed significantly improved strength, fracture toughness, interlaminar shear strength, glass transition temperature and tribological performance. Under dynamic load, graphene/MWCNT reinforcement of matrix and CF synergistically increases the storage modulus and energy absorption characteristics. Wear and fracture surface morphology of nano and multi-scale composites showed ductile failure confirming interfacial adhesion. The failure behavior in experimental studies was supported by Abaqus/Explicit-based FEM models of fracture toughness response. This work provides a promising avenue to develop next generation high performance thermoplastic composites for structural applications.

Prediction of Electromagnetic Performance for IPMSM Based on Improved Analytical Model Considering Saturation Effects

Unlike surface-mounted permanent magnet synchronous motors (SPMSM), the rotor structure of interior permanent magnet synchronous motors (IPMSM) is irregular and relatively complex. This makes the analytical calculation for IPMSM quite complicated. Except for the use of some equivalent methods to make irregular permanent magnets (PMs) regular, existing subdomain models often cannot effectively and directly account for the complex rotor structure and cannot be easily applied to IPMSM. For this reason, an improved analytical model applicable to IPMSM is presented, studied, and developed in this article. First, a novel subdomain model division method is innovatively introduced. Complex rotor structure can be well accounted for. This not only facilitates the expression of vector potential and satisfies the establishment of subdomain model, but also recovers the original rotor topology to the maximum extent and effectively avoids many uncertainties and unreliability caused by over-equivalence. Afterwards, the magnetic equivalent circuit and equivalent surface current method are combined to fully consider the saturation effects of magnetic isolation bridges, rotor ribs, and cores. Model analysis accuracy is well guaranteed. Further, the precise subdomain method is investigated to achieve fast prediction of key electromagnetic performance. Both finite element analysis (FEA) and prototype experiment strongly highlight the validity of the improved analytical model. In addition, compared to FEA, the improved analytical model does not require tens of thousands of computation cells, which saves a lot of time and storage while ensuring the same prediction accuracy. This opens up unlimited possibilities for the design and optimization of IPMSM.

Bond strength model between steel rebar and ultrahigh performance concrete containing coarse aggregates

To clarify the bond performance between steel rebar and ultrahigh performance concrete containing coarse aggregates (UHPC-CA), a total of 33 pull out specimens was cast. The effects of coarse aggregate particle size, coarse aggregate content, and steel fiber content on the failure modes and bond stress-slip curves of the specimens were studied. Based on the virtual crack model, considering the tensile contribution of steel fibers and the bridging effect of coarse aggregates, a model for the bond strength between UHPC-CA and steel rebar was established. The research findings indicated that there was a corresponding matching relationship between coarse aggregate particle size and the spacing of steel rebar ribs. In the 5–8 mm particle size group, the specimens showed 7.95% and 9.01% increases in bond strength compared to the 3–5 mm and 8–10 mm particle size groups, respectively. When the coarse aggregate content of UHPC-CA was 20%, the bond strength was the highest, increasing by 11.39% compared to specimens without coarse aggregates. The bond strength first increased and then decreased with increasing steel fiber content. Excessive steel fiber content could lead to the clustering of steel fibers, reducing the effective number of steel fibers contributing to toughening. The calculated results from the established bond strength model were compared with experimental and literature results, yielding an average ratio of 0.993 and a standard deviation of 0.166. This model effectively predicts the bond strength between UHPC-CA and steel rebar.

Research on surface modification of polypropylene fiber and its application evaluation in oil well cement

In order to improve the compatibility and dispersibility of polypropylene fiber (PPF) in oil well cement and enhance the mechanical properties of cementing cement sheath, the surface modification of PPF was carried out in this study. After surface impurity removal of PPF, reaction of catechol with polyamines, and subsequent treatment with γ- aminopropyltriethoxysilane (KH-550) and Ethyl orthosilicate (TEOS), modified polypropylene fiber (MPF) was obtained. The MPF was characterized and analyzed using FTIR, XPS, SEM, and EDS, showing a transformation in the surface properties of the fibers. The most significant change was that the contact angle between MPF and water decreased from 123.87 ° to 46.32 °, marking the successful transition of the fiber from hydrophobicity to hydrophilicity. Image analysis showed that the dispersion of MPF improved significantly. The dispersion coefficient of MPF in water and cement stone was increased by 86.90% and 14.48% compared with PPF, respectively. The effect of MPF on mechanical properties of oil well cement stone was studied. The comparative analysis results showed that MPF can significantly improve the flexural and compressive strength of the cement matrix. The flexural and compressive strength of cement stone mixed with MPF were increased by 10.25% and 6.43%, respectively, compared to cement stone mixed with PPF. SEM, MIP, and fiber single fiber pull-out experiments showed that the porosity of cement stone added with MPF was lower, the rough surface structure of MPF enhanced the bonding between fibers and cement stone, and the bridging effect of fibers in cement stone ultimately improved the mechanical properties of oil well cement stone.

Hybrid Effect of Basalt and Polyacrylonitrile Fibers on Physico-Mechanical Properties of Tailing Mortar

In this study, 50% iron ore tailings (IOTs) were used to prepare the cemented mortar at low economic costs and with great environmental benefits. Basalt fiber (BF) and polyacrylonitrile fiber (PANF) were added to the tailing mortar to improve the comprehensive performance of tailing mortars, including BF (0~0.5%), PANF (0~0.05%) and the combination of them. The results show that the addition of BF and PANF can significantly improve the ultrasonic velocity, uniaxial compressive strength (UCS), split-tensile strength (STS), flexural strength (FS) and toughness of the tailing mortar. A novel finding is that the enhancement of hybrid fibers is much better than single fiber, and the best hybrid fiber combination is B0.25P0.05 (0.25 wt% BF and 0.05 wt% PANF), because this combination not only causes the most considerable increase in strength but also possesses great cost-effectiveness. Compared to the B0P0 group without fibers, the maximum increments of B0.25P0.05 in UCS, STS and FS are 45.74%, 52.33% and 15.65%, respectively. It is evidenced that the improvement in STS is the largest because the fibers have good cracking resistance and bridging effect in the tailing mortar. The scanning electron microscope (SEM) further confirms that too many hybrid fibers will agglomerate and produce more voids, which is harmful to the development of the internal structure. Beyond B0.25P0.05, the hydration products are also reduced due to the decrease in nucleation sites, observed by combining X-ray diffraction (XRD) tests. Therefore, it is suggested that the hybrid fibers containing 0.25% BF and 0.05% PANF should be used in this tailing mortar.

Simplified method to detect resonance effects in railway bridges. Viaduct over Aragón River and Almonte bridge application

Detecting resonant effects in bridges has been studied for many years, but it has only been solved in a closed form for simple bridges. This article presents a simplified method that enables the calculation of resonance velocities in all types of bridges in an easy manner. The method is based on the concept of dynamic influence line and is validated through finite element models. These models range from simply supported bridges to complex real bridges such as the Almonte Viaduct, the world’s longest arch bridge of its typology. In the real bridge models, a dynamic analysis is performed according to the Eurocode to identify train velocities that induce resonant effects, and these velocities are checked against the simplified method with very good results.

A new type of high flexural strength micro-nano-composite ceramic tool material Ti(C,N)/WC/ZrO2 for integrated micro milling cutter

Ti(C,N) composites are widely applied in various advanced manufacturing industries. However, the intrinsic brittleness and relatively high metal content for Ti(C,N) composites significantly limit their further applications, especially in high-temperature and high-speed machining conditions. Herein, a new type of high flexural strength micro-nano-composite ceramic tool material Ti(C,N)/WC/ZrO2 for integrated micro milling cutter which will be used to mill difficult-to-machine material such as titanium alloy was proposed and developed successfully by hot press sintering technique under vacuum. The Ti(C,N) composites with low metal phase strengthened by nano-3Y-ZrO2 and micro-WC particles, the effect of compositions and sintering parameters on the mechanical properties and microstructure of the composite ceramic materials were systematically investigated. The results demonstrated that the Ti(C,N) composites with low metal phase containing 15 wt% nano-3Y-ZrO2 and 15 wt% micro-WC, sintered at 32 MPa and 1500 °C for 45 min had the optimal mechanical properties under vacuum and the flexural strength, Vicker's hardness, fracture toughness and relative density were 1501 ± 86 MPa, 19.97 ± 0.43GPa, 7.25 ± 0.76 MPa.m1/2 and 99.55%, respectively. Meanwhile, the superior mechanical properties of the Ti(C,N) composites with low metal binder phase could be achieved when sintered at higher temperatures and longer holding times compared to conventional cerments. Moreover, the toughening and strengthening mechanisms for Ti(C,N) composites with low metal phase are the synergistic effects of crack bridging, crack branching, crack deflection, pinning effect, particle pull-out, intragranular microstructure, transgranular and intergranular fracture. These toughening and strengthening mechanisms and the solid solution effects generated by the joint action of oxides and carbides could remarkably improve the properties for the Ti(C,N) composites. In this study, a novel insight on developing high-property Ti(C,N) composites was proposed, and it will make a significant contribution to material synthesis and design, application for cutting tools and composite ceramics investigations.

Effects of cations on biofilms in gravity-driven membrane system: Filtration performance and mechanism investigation

The gravity-driven membrane (GDM) system is desirable for energy-efficient water treatment. However, little is known about the influence of cations on biofilm properties and GDM performance. In this study, typical cations (Ca2+ and Na+) were used to reveal the combined fouling behavior and mechanisms. Results showed that Ca2+ improved the stable flux and pollutant removal efficiency, while Na+ adversely affected the flux. Compared with GDM control, the concentration of pollutants was lower in Ca-GDM, as indicated by the low biomass, proteins, and polysaccharides. A heterogeneous and loose biofilm was observed in the Ca-GDM system, with roughness and porosity increasing by 43.06 % and 32.60 %, respectively. However, Na+ induced a homogeneous and dense biofilm, with porosity and roughness respectively reduced by 17.48 % and 22.04 %. The richness of bacterial communities increased in Ca-GDM systems, while it decreased in Na-GDM systems. High adenosine triphosphate (ATP) concentration in Ca-GDM system was consistent with the abundant bacteria and their high biological activity, which was helpful for the efficient removal of pollutants. The abundance of Apicomplexa, Platyhelminthes, Annelida and Nematoda increased after adding Ca2+, which was related to the formation of loose biofilms. Computational simulations indicated that the free volumes of the biofilms in Ca-GDM and Na-GDM were 13.7 and 13.2 nm3, respectively. The addition of cations changed intermolecular forces, Ca2+ induced bridging effects led to large and loose floc particles, while the significant dehydration of hydrated molecules in the Na-GDM caused obvious aggregation. Overall, microbiological characteristics and contaminant molecular interactions were the main reasons for differences in GDM systems.

Promoting bridging in adhesively bonded composites with polymer inserts: A computational perspective

Preventing catastrophic failure due to delamination in adhesively bonded carbon fiber reinforced polymer (CFRP) is crucial to enhancing the reliability of structures. Experimental evidence from another study demonstrated that introducing inserts into the adhesive bond line creates bridging, effectively arresting the delamination process. In this paper, a numerical model was proposed to mimic the experiment and then utilized for conducting parametric studies. An embedded cell approach was adopted, representing a double cantilever beam (DCB) with linear-elastic continuum shell elements, beam elements for the bridging bundles, and connector elements for the adhesive. The crack propagation was initiated with adhesive failure and subsequently followed by bridging bundle failure. The numerical simulation results closely replicated the experiment’s global response in the force–displacement curve, thereby effectively validating the existence of the bridging effect. Furthermore, our study revealed that enhancing the adhesive strength and insert ductility can further improve crack resistance.

Enhancing Conjugation Effect to Develop Nitrogen-Rich Energetic Materials with Higher Energy and Stability.

This work reports a strategy by enhancing conjugation effect and synthesizes a symmetrical and planar compound, 1,2-bis (4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazol-2-yl)diazene (NL24). The incorporation of azo and 1,2,3-triazole moieties manifests a synergistic effect, amplifying the conjugation effect of the azo bridge and thereby elevating the stability of NL24 (Td: 263 °C, IS: 7 J). Notably, NL24, possessing a structural configuration comprising four tetrazoles harboring a total of 24 nitrogen atoms, exhibits excellent detonation performances (ΔHf: 6.06 kJ g-1, VD: 9002 m s-1). This strategy achieves the balance of energy and stability of polycyclic tetrazoles and provides a direction for high-performance energetic materials.

Hollow nanocages heterostructured NiCo-LDH/MWCNTs electrocatalyst for highly sensitive and non-invasive detection of saliva glucose

Monitoring salivary glucose has gained increased attention as a non-invasive approach to prevent and diagnose diabetes. Since the glucose concentration in saliva is lower than that in blood, the development of effective electrocatalysts for highly sensitive glucose detection is thus of great significance. In this study, a hollow nanocage from NiCo-layered double hydroxides (LDH) modified with multi-walled carbon nanotubes (MWCNTs) is designed and further employed as the sensing material to construct a novel non-enzymatic glucose electrochemical sensor with high sensitivity. It is synthesized by utilizing pre-synthesized zeolitic imidazolate framework (ZIF-67)/MWCNTs as a sacrificial template and subsequently conducting a simple solvent-thermal reaction with Ni(NO3)2. Such a hollow nanocage preserves the polyhedral framework structure of the used precursor, where the hollow frame-like structure of NiCo-LDH offers accessible catalytic sites, and MWCNTs provides good conductivity. Their combination brings in a bridging effect between MWCNTs and NiCo-LDH, further leading to a large electrochemical active area and excellent catalytic activity of this hollow nanocage. The constructed sensor exhibits a detection limit as low as 0.03 μM for the glucose detection as well as wide linear ranges of 0.1–3000 μM and 3000–9231.8 μM, corresponding to the sensitivity of 2.55 and 1.15 μA mM−1 cm−2, respectively. Moreover, this sensor enables the tracking of glucose concentration change in salivary before and after food intake. This work offers new highly sensitive sensing materials and potentially valuable approaches for non-invasive glucose detection.