Rigid Groups Research Articles

Bus Network Adjustment Pre-Evaluation Based on Biometric Recognition and Travel Spatio-Temporal Deduction

A critical component of bus network adjustment is the accurate prediction of potential risks, such as the likelihood of complaints from passengers. Traditional simulation methods, however, face limitations in identifying passengers and understanding how their travel patterns may change. To address this issue, a pre-evaluation method has been developed, leveraging the spatial distribution of bus networks and the spatio-temporal behavior of passengers. The method includes stage of travel demand analysis, accessible path set calculation, passenger assignment, and evaluation of key indicators. First, we explore the actual passengers’ origin and destination (OD) stop from bus card (or passenger Code) payment data and biometric recognition data, with the OD as one of the main input parameters. Second, a digital bus network model is constructed to represent the logical and spatial relationships between routes and stops. Upon inputting bus line adjustment parameters, these relationships allow for the precise and automatic identification of the affected areas, as well as the calculation of accessible paths of each OD pair. Third, the factors influencing passengers’ path selection are analyzed, and a predictive model is built to estimate post-adjustment path choices. A genetic algorithm is employed to optimize the model’s weights. Finally, various metrics, such as changes in travel routes and ride times, are analyzed by integrating passenger profiles. The proposed method was tested on the case of the Guangzhou 543 route adjustment. Results show that the accuracy of the number of predicted trips after adjustment is 89.6%, and the predicted flow of each associated bus line is also consistent with the actual situation. The main reason for the error is that the path selection has a certain level of irrationality, which stems from the fact that the proportion of passengers who choose the minimum cost path for direct travel is about 65%, while the proportion of one-transfer passengers is only about 50%. Overall, the proposed algorithm can quantitatively analyze the impact of rigid travel groups, occasional travel groups, elderly groups, and other groups that are prone to making complaints in response to bus line adjustment.

Synergy between biphenyl mesomorphic structure and organic crystal phenazine for improving the intrinsic thermal conductivity of epoxy

The inherent low intrinsic thermal conductivity of epoxy resin severely restricts its potential application, making it difficult to meet the growing demand of energy, electrical and electronic technologies. The liquid crystal epoxy resin, which is wildly employed to improve the intrinsic thermal conductivity of epoxy resin, is constrained by its complex molecular structure design and synthesis procedures. In this work, the rigid group of 4,4’-dihydroxybiphenyl was introduced into the main chain of epoxy resin by ring-opening polymerization (ROP) to change the molecular structure of epoxy resin. The introduction of biphenyl groups enhances the orderliness of molecular structure and forms hydrogen bonds between molecules, which further enhances the transport of intramolecular phonons. The thermal conductivity of the graft modified epoxy resin (GMR) after DDM curing is 0.30 W·m-1·K-1. After adding of organic crystal phenazine (PNE) to the GMR matrix, the inherent strong crystallization behaviors of PNE can accelerate the regularity arrangement of rigid groups in GMR, and promote the nucleation and crystallization process of GMR/PNE. The thermal conductivity of GMR/PNE after DDM curing can reach 0.33 W·m-1·K-1. It is 165% of the thermal conductivity of traditional epoxy resin, which is 0.2 W·m-1·K-1. This study will provide a new method to improve the intrinsic thermal conductivity of polymer materials.

Comparison of Glisson traction, soft or rigid cervical collars for the treatment of acute atlantoaxial rotatory subluxation in children: a retrospective study

To examine the clinical effect of different conservative therapies (Glisson traction, soft and rigid cervical collar) in the treatment of children with acute atlantoaxial rotatory subluxation. One hundred and forty-four children with acute atlantoaxial rotatory subluxation treated conservatively at our hospital from June 2017 to June 2022 were retrospectively analyzed. The children were divided into three groups consisting of patients treated with Glisson traction (n = 37), patients treated with soft cervical collar (n = 55), and patients treated with rigid cervical collar (n = 52). Clinical and functional results were compared among the three groups. Success outcomes were achieved at the end of treatment in the Glisson traction group (94.59%, 35/37), soft cervical collar group (83.64%, 46/55), and rigid cervical collar group (92.31%, 48/52). There was no significant difference between the success rates among the three groups (P > 0.05). At the last follow-up, the overall scores based on our scoring scale for the Glisson traction, soft cervical collar and rigid cervical collar groups were 95.95 ± 6.11 (range: 75–100), 94.64 ± 6.30 (range: 75–100) and 95.00 ± 6.02 (range: 70–100), respectively. There was no significant difference in the overall scores among the three groups (P > 0.05). All three conservative therapies for the treatment of acute atlantoaxial rotatory subluxation can attain a good clinical outcome. Treatment using a cervical collar should be given priority as it does not require the child to be hospitalized. Rigid cervical collar provides good immobilization and can possibly lead to better clinical outcomes compared to a soft cervical collar.

Comparative Study of Polymer of Intrinsic Microporosity-Derivative Polymers in Pervaporation and Water Vapor Permeance Applications

This study assesses the gas and water vapor permeance of PIM-derivative thin-film composite (TFC) membranes using pervaporation and “pressure increase” methods, and provides a comparative view of “time lag” measurements of thick films obtained from our previous work. In this study, TFC membranes were prepared using PIM-1 and homopolymers that were modified with different side groups to explore their effects on gas and water vapor transport. Rigid and bulky aliphatic groups were used to increase the polymer’s free volume and were evaluated for their impact on both gas and water transport. Aromatic side groups were specifically employed to assess water affinity. The permeance of CO2, H2, CH4 and water vapor through these membranes was analyzed using the ‘pressure increase’ method to determine the modifications’ influence on transport efficiency and interaction with water molecules. Over a 20 h period, the aging and the permeance of the TFC membranes were analyzed using this method. In parallel, pervaporation experiments were conducted on samples taken independently from the same membrane roll to assess water flux, with particular attention paid to the liquid form on the feed side. The significantly higher water vapor transport rates observed in pervaporation experiments compared to those using the “pressure increase” method underline the efficiency of pervaporation. This efficiency suggests that membranes designed for pervaporation can serve as effective alternatives to conventional porous membranes used in distillation applications. Additionally, incorporating “time lag” results from a pioneering study into the comparison revealed that the trends observed in “time lag” and pervaporation results exhibited similar trends, whereas “pressure increase” data showed a different development. This discrepancy is attributed to the state of the polymer, which varies significantly depending on the operating conditions.

19F NMR relaxation of buried tryptophan side chains suggest anisotropic rotational diffusion of the protein RfaH.

The recent application of 19F NMR in the study of biomolecular structure and dynamics has made it a potentially attractive probe to complement traditional 15N/13C labelled probes for backbone and sidechain dynamics, albeit with some complications. The utility of 15N relaxation rates of rigid backbone amide groups to determine the rotational diffusion tensor of proteins is well established. Here we show that the measured 19F relaxation rates of two buried and possibly immobile 19F labelled tryptophan sidechains for the multidomain protein RfaH, in its closed conformation, are in reasonable agreement with the calculated values, only when anisotropic rotational diffusion of the protein is considered. While the sparsity of 19F relaxation data from a limited number of probes precludes the experimental determination of the rotational diffusion tensor here, these results demonstrate the influence of rotational diffusion anisotropy of proteins on 19F NMR relaxation of rigid tryptophan sidechains, while adding to the expanding literature of 19F NMR relaxation data sets in biomolecules.

Three-dimensional numerical analysis of the effect of foundation stiffness on soil-structure interaction

Stiffness-related geometric characteristics are closely linked to the performance of structural systems. The influence of foundation stiffness on the soil-structure interaction (SSI) mechanism was investigated by numerical modeling of different building foundations. Numerical tools (PLAXIS 3D and TQS/CAD) were used for decoupling analyses of the interaction between the structural components. Results obtained from instruments installed in a building case study were used to refine the numerical calculations. Linear elastic constitutive models and beam elements were useful in reducing computational processes and ensuring study feasibility. The simulation results provided a satisfactory representation of field observations. Interaction between piles and the environment governs the relationship between foundation stiffness and uniform settlement. Rigid pile groups are achieved with greater pile length, diameter and spacing. This study highlights the different effects of pile geometric parameters on loading and unloading rates in pillars, demonstrating that the SSI mechanism is more sensitive to less rigid foundations, particularly those with greater pile embedment. It was concluded that numerical simulations to predict settlement as realistically as possible require understanding and selecting the most appropriate model and type of calculation.

Flexible reamer use to overcome entry point errors in proximal femoral nail application in severe obese intertrochanteric fracture patients

IntroductionProximal femoral nailing (PFN) offers biomechanical benefits for intertrochanteric fractures but can lead to higher complication rates from poor reduction and technique errors, particularly in obese patients. Incorrect entry points may cause reduction loss, iatrogenic fractures, and misplaced lag screws. The study aims to investigate the effect of using an oriented flexible reamer instead of a rigid reamer on clinical and radiological results to obtain a medial entry point and better positioning of the nail in the intramedullary area in obese intertrochanteric fracture patients.Materials and methodsA retrospective analysis was conducted on patients aged 65 years and older who underwent PFN treatment between March 2020 and June 2022 at a single institution, with at least 1-year postoperative follow-up. Patients were divided into two groups: those applied with a flexible reamer and a rigid reamer. Parameters analyzed from postoperative radiographs included tip-apex distance (TAD), calcar-referenced tip-apex distance (CalTAD), reduction quality, femoral neck-shaft angle, and lag screw placement. Complication rates and types were recorded for each group.ResultThe analysis included 91 patients, with 45 treated using a flexible reamer and 46 treated using a rigid reamer. There was no statistical difference between the two groups regarding age, gender, BMI, and AO class distributions of the patients (p > 0.05). The Femur neck shaft angle was significantly higher in the flexible reamer group (p < 0.001). As a result of the reduction types analysis, medial type reduction was significantly higher in the group where the flexible reamer was applied (p < 0.001). The CalTAD was shorter in the Flexible reamer group (p = 0.005). Complications and the need for reoperation were statistically significantly higher in the rigid reamer group (p < 0.048).ConclusionThe oriented flexible reamer reduces application-related errors in patients undergoing proximal femoral nail (PFN) treatment due to intertrochanteric fracture. The oriented flexible reamer technique allows a more medial entry point. Oriented flexible reamer creates enough space on both fracture sides at the level of intertrochanteric fracture to avoid nail pass-related complications.Level of evidenceLevel III, Case-control study.

Carbocyclic setmelanotide analogs maintain biochemical potency at melanocortin 4 receptors.

The melanocortin 4 receptor (MC4R) plays a critical role in satiety and energy homeostasis, and its dysregulation is implicated in numerous hyperphagic and obese disease states. Setmelanotide, a disulfide-based cyclic peptide, can rescue MC4R activity and treat obesities caused by genetic defects in MC4R signaling. But this peptide has moderate blood-brain barrier penetrance and metabolic stability, which can limit its efficacy in practice. Based on the cryo-electron microscopy structure of setmelanotide-bound MC4R, we hypothesized that replacing its lone disulfide bond with more metabolically stable and permeability-enhancing carbon-based linker groups could improve pharmacokinetic properties without abolishing activity. To test this, we used chemistry developed by our lab to prepare 11 carbocyclic (alkyl, aryl, perfluoroalkyl, and ethereal) analogs of setmelanotide and determined their biochemical potencies at MC4R in vitro. Ten analogs displayed full agonism, showing that disulfide replacement is tolerant of linkers ranging in size, rigidity, and functional groups, with heteroatom- or aryl-rich linkers displaying superior potencies.

Flexible versus Rigid Bronchoscopy for Tracheobronchial Foreign Body Removal in Children: A Comparative Systematic Review and Meta-Analysis.

The removal of foreign bodies (FBs) from the airways of children is a critical procedure that can avert serious complications. While both flexible and rigid bronchoscopy techniques are employed for this purpose, their comparative efficacy and safety remain subjects of debate. Therefore, we conducted this investigation to compare between both procedures. Studies comparing flexible to rigid bronchoscopy (n = 14) were identified by searching PubMed, Scopus, Web of Science, Cochrane Library, and Google Scholar. We performed comparative meta-analyses of reported presentation characteristics and clinical outcomes, using fixed- and random-effects models. A diverse range of FB types and locations were identified. No difference was observed in the success rate of FB removal between flexible and rigid bronchoscopy (logOR = 0.27; 95%CI: -1.91:2.45). The rate of negative first bronchoscopy was higher in the flexible compared to the rigid group (logOR = 2.68; 95%CI: 1.68:3.67). Conversion rates to the alternative method were higher in the flexible bronchoscopy group. The overall complication rates were similar between both methods; however, the risk of desaturation was significantly lower with flexible bronchoscopy (logOR = -2.22; 95%CI: -3.36:-1.08). Flexible bronchoscopy was associated with a shorter length of hospital stay. The choice of bronchoscopy technique should be tailored to individual case characteristics.

Mechanically compliant locking plates for diaphyseal fracture fixation: A biomechanical study.

Axial micromotion between bone fragments can stimulate callus formation and fracture healing. In this study, we propose a novel mechanically compliant locking plate which achieves up to 0.6 mm of interfragmentary motion as flexures machined into the plate elastically deflect under physiological load. We investigated the biomechanical performance of three compliant plate variations in comparison to rigid control plates with small and large working lengths in a comminuted bridge plating scenario using humeral diaphysis surrogates. Under static axial loading, average interfragmentary motion was 6 times larger at 100 N (0.38 vs. 0.05 mm) and nearly three times larger at 350 N (0.58 vs. 0.2 mm) for compliant plates than rigid plates, respectively. Compliant plates delivered between 2.5 and 3.4 times more symmetric interfragmentary motion than rigid plates (p < 0.01). The bi-phasic stiffness of compliant pates provided 74%-96% lower initial axial stiffness up to approximately 100 N (p < 0.01), after which compliant plate stiffness was similar to rigid plates with increased working length (p > 0.3). The strength to failure of compliant plates under dynamic loading was on average 48%-55% lower than rigid plate groups (p < 0.01); however, all plates survived cyclic fatigue loading of 100,000 cycles at 350 N. This work characterizes the improvement in interfragmentary motion and the reduction in strength to failure of compliant plates compared to control rigid plates. Compliant plates may offer potential in comminuted fracture healing due to their ability to deliver symmetric interfragmentary motion into the range known to stimulate callus formation while surviving moderate fatigue loading with no signs of failure.

Influence of Connector Design on Displacement and Micromotion in Tooth-Implant Fixed Partial Dentures Using Different Lengths and Diameters: A Three-Dimensional Finite Element Study.

The literature presents insufficient data evaluating the displacement and micromotion effects resulting from the combined use of tooth-implant connections in fixed partial dentures. Analyzing the biomechanical behavior of tooth-implant fixed partial denture (FPD) prothesis is vital for achieving an optimum design and successful clinical implementation. The objective of this study was to determine the relative significance of connector design on the displacement and micromotion of tooth-implant-supported fixed dental prostheses under occlusal vertical loading. A unilateral Kennedy class I mandibular model was created using a 3D reconstruction from CT scan data. Eight simulated designs of tooth-implant fixed partial dentures (FPDs) were split into two groups: Group A with rigid connectors and Group B with non-rigid connectors. The models were subjected to a uniform vertical load of 100 N. Displacement, strain, and stress were computed using finite element analysis. The materials were defined as isotropic, homogeneous, and exhibiting linear elastic properties. This study focused on assessing the maximum displacement in various components, including the bridge, mandible, dentin, cementum, periodontal ligament (PDL), and implant. Displacement values were predominantly higher in Group B (non-rigid) compared to Group A (rigid) in all measured components of the tooth-implant FPDs. Accordingly, a statistically significant difference was observed between the two groups at the FPD bridge (p value = 0.021 *), mandible (p value = 0.021 *), dentin (p value = 0.043 *), cementum (p value = 0.043 *), and PDL (p value = 0.043 *). Meanwhile, there was an insignificant increase in displacement values recorded in the distal implant (p value = 0.083). This study highlighted the importance of connector design in the overall stability and performance of the prosthesis. Notably, the 4.7 mm × 10 mm implant in Group B showed a displacement nearly 92 times higher than its rigid counterpart in Group A. Overall, the 5.7 mm × 10 mm combination of implant length and diameter showcased the best performance in both groups. The findings demonstrate that wider implants with a proportional length offer greater resistance to displacement forces. In addition, the use of rigid connection design provides superior biomechanical performance in tooth-implant fixed partial dentures and reduces the risk of micromotion with its associated complications such as ligament overstretching and implant overload, achieving predictable prognosis and enhancing the stability of the protheses.

High stable poly (terphenyl-co-fluorene quinuclidinium) anion exchange membrane for alkaline water electrolysis

Developing anion exchange membranes (AEMs) is an effective way to reduce the cost of water electrolyser systems and fuel cell systems because of the no requirement of platinum-group-metal (PGM) catalysts. However, low conductivity and poor stability are the bottlenecks that constrain its development. In this work, we propose a series of performance enhanced poly (terphenyl-co-fluorene quinuclidinium) (TPFQ) AEMs. The hydroxide conductivity of TPFQ-10 reached 178.5 mS cm−1 at 80 °C. The rigid fluorene group gives the membrane better dimensional stability (swelling ratio: 7.7% in pure water and 1.2% in 10 M NaOH at 80 °C for TPFQ-10). In particular, the membranes exhibit extremely high alkaline stability, with almost no conductivity loss over more than 2000 h in a 10 M NaOH solution. The AEM water electrolysers (AEMWEs) with nickel-alloy foam electrodes shows an excellent current density of 2.32 A cm−2 at 2.0 V. The AEMWEs can work steadily at a current density of 0.5 A cm−2 in 5 M NaOH at 80 °C for more than 500 h, with a low voltage rising rate of 56 μV h−1.

Bio-derived Schiff base vitrimer with outstanding flame retardancy, toughness, antibacterial, dielectric and recycling properties

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP1.0) was prepared. The CIP1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2%. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP1.0 with outstanding fire retardancy. The CIP1.0 shows excellent toughness with high elongation at break of 45.0% due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP1.0 result in a low dielectric constant. The CIP1.0 exhibits superior antimicrobial properties. The CIP1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins.

Research on Improving the Thermal Conductivity of Epoxy Resin with Flexible Assisted Rigid Groups

Research on Improving the Thermal Conductivity of Epoxy Resin with Flexible Assisted Rigid Groups

Rigid–flexible coupling design and reusable impact mitigation of the hierarchical-bistable hybrid metamaterials

Mechanical metamaterials with multistable unit cells featured by negative stiffness or quasi-zero stiffness is attracting increasing attention owing to their unique mechanical properties and reusable potential. In this paper, a hierarchical-bistable hybrid metamaterial with rigid–flexible coupling design is proposed, demonstrating excellent mitigation performance and protection against multiple impacts. The metamaterial consists of a multi-layer bistable beams with a central honeycomb and is manufactured by 3D printing. Firstly, the negative stiffness characteristics of the curved beams in the metamaterial are theoretically determined, and the convergence of the finite element model under different mesh sizes is analyzed. And the quasi-zero stiffness characteristics of the metamaterial have been confirmed, along with its more stable and uniform deformation pattern, through the quasi-static compression experiment. Then the buffering performance of the metamaterial is studied in ball impact tests, showing an average improvement of about 65% compared to the rigid control group, while verifying the accuracy of the finite element model. With the analysis of the deformation modes and strain energy, the mitigation mechanism of metamaterials is demonstrated to extend the contact time and disperse the impact load through the layered deformation to reduce the peak response, instead of relying on plastic strain. Finally, the reusability of the metamaterial is explored by the ten-times plate impacts simulation. The results demonstrate that the metamaterial decreases the plastic strain of its structure by 60% while reducing impact response, thereby preventing the premature failure of core components. These results demonstrate the great potential of the proposed metamaterials for various engineering applications, including aircraft or spacecraft landing protection, vehicle pedestrian protection, and the transportation protection of fragile objects or precision instruments.

Bile Acid-conjugate as a Promising Anticancer Agent: Recent Progress.

Bile acids have outstanding chemistry due to their amphiphilic nature and have received a lot of interest in the last few decades in the fields of biomedicine, pharmacology, and supramolecular applications. Bile acids are highly sought after by scientists looking for diverse and effective biological activity due to their chirality, rigidity, and hydroxyl group. The hydroxyl group makes it simple to alter the structure in a way that improves bioactivity and bioavailability. Bile acid-bioactive molecule conjugates are compounds in which a bile acid is linked to a bioactive molecule by a linker in order to increase the bioactivity of the bioactive molecule against the target cancer cells. This method has been used to improve the therapeutic efficacy of cytotoxic drugs while reducing their adverse side effects. These new bile acid conjugates are gaining attention because they overcome bioavailability and stability issues. The design, synthesis, and anticancer effectiveness of various bile acid conjugates are discussed together with recent advances in understanding in this review.

Is orthotic treatment beneficial for fresh osteoporotic vertebral fractures? A propensity score matching study

BACKGROUND CONTEXTOrthotic treatment is a common option for the conservative treatment of osteoporotic vertebral fractures (OVF). However, there is insufficient evidence of its clinical benefit. PURPOSETo investigate the effectiveness of orthotic treatment for OVF. STUDY DESIGN/SETTINGRetrospective cohort study with data from two prospective studies. PATIENT SAMPLEThis study included 160 patients with fresh OVF enrolled in 2012 and 2020 prospective cohort studies. OUTCOME MEASURESThe visual analog scale (VAS) score for low back pain was used for clinical outcomes, and radiographic parameters included the percent height of the vertebra and angular change of the vertebral body. Moreover, the occurrence of secondary vertebral fractures was followed-up over time. METHODSThe patients were divided into brace and no-brace groups and were matched according to propensity score for age, sex, anterior percent height at the initial examination, and presence of old OVFs. Hazard ratio for the cumulative incidence of secondary vertebral fractures with and without bracing were calculated and analyzed using the generalized Wilcoxon test. In addition, the brace group was divided into soft and rigid brace groups and compared with the no-brace group. RESULTSEach group had 61 cases after propensity score matching. There were no significant differences in the VAS improvement for low back pain and the change in percent height of the anterior and posterior walls from initial examination to 6 months after injury (p=.87, p=.39 and p=.14, respectively, mixed-effect models). Meanwhile, the mean angular change of fractured vertebrae was 4.3° / 3.2° initially and 1.2° / 2.5° at 6 months (the brace group / no-brace group, respectively; p=.007, mixed-effect models). A significant difference was also observed between the rigid brace group and the no-brace group (p=.008, mixed effect models). The incidence of secondary vertebral fractures was 1.6% / 11.4% at 1 month, indicating a significant difference (the brace group / no-brace group, respectively; p = .028). The hazard ratio for the cumulative incidence of secondary fractures due to orthotic treatment was 0.47 (95% confidence interval 0.20–1.09, p=.054). CONCLUSIONSAlthough orthotic treatment for fresh OVF did not relieve pain, it might contribute to the stabilization of the fractured vertebra, especially using a rigid brace. Moreover, it might influence a reduction of the imminent vertebral fracture risk immediately after the onset of OVF. ClassificationsClinical study

Strong yet Tough Catalyst-Free Transesterification Vitrimer with Excellent Fire-Retardancy, Durability, and Closed-Loop Recyclability.

Despite great advances in vitrimer, it remains highly challenging to achieve a property portfolio of excellent mechanical properties, desired durability, and high fire safety. Thus, a catalyst-free, closed-loop recyclable transesterification vitrimer (TPN1.50) with superior mechanical properties, durability, and fire retardancy is developed by introducing a rationally designed tertiary amine/phosphorus-containing reactive oligomer (TPN) into epoxy resin (EP). Because of strong covalent interactions between TPN and EP and its linear oligomer structure, as-prepared TPN1.50 achieves a tensile strength of 86.2MPa and a toughness of 6.8MJm-3, superior to previous vitrimer counterparts. TPN1.50 containing 1.50 wt% phosphorus shows desirable fire retardancy, including a limiting oxygen index of 35.2% and a vertical burning (UL-94) V-0 classification. TPN1.50 features great durability and can maintain its structure integrity in 1M HCl or NaOH solution for 100 days. This is because the tertiary amines are anchored within the cross-linked network and blocked by rigid P-containing groups, thus effectively suppressing the transesterification. Owing to its good chemical recovery, TPN1.50 can be used as a promising resin for creating recyclable carbon fiber-reinforced polymer composites. This work offers a promising integrated method for creating robust durable fire-safe vitrimers which facilitate the sustainable development of high-performance polymer composites.

A dual cross-linking strategy enables fully bio-based epoxy thermosets with superior low dielectric properties and mechanical properties

Bio-based epoxy resins with superior low dielectric properties and mechanical properties is of great significance for sustainable development and environmental protection. Herein, a bio-based active ester curing agent with large free volume was synthesized through a substitution reaction between magnolol and cinnamoyl chloride following by curing epoxidized linseed oil for fully bio-based epoxy thermosets. The curing kinetics of the curing behavior and the curing condition was systematic studied and optimized. The relationship between chemical structure and properties (thermo-mechanical, mechanical, dielectric, and etc.) of the resulting fully bio-based epoxy thermosets was discussed in-depth. The results showed that free radical polymerization and epoxy ring-opening reactions simultaneously occurred in the curing reaction led to a dual cross-linked structure of the resulting fully bio-based epoxy thermosets. The unique structures and the introduction of the rigid benzene groups rendered the tensile strength and the thermal stability of the resulting fully bio-based epoxy thermosets high up to 33.63 MPa and 332.40 °C, respectively. The absence of the secondary hydroxyl groups and the presence of the low polar fatty acid chains in the backbone of the epoxy resins resulted in the dielectric constant and dielectric loss low to 3.19 and 0.012, which was much lower than those of the polymer previously reported. This study provides a simple and facile strategy for the design of environmentally friendly fully bio-based epoxy resins for microelectronics and electronic packaging application.

Failure envelopes of rigid tripod pile foundation under combined vertical-horizontal-moment loadings in clay

The problem considered in this computational study is for the bearing capacity determination of three-dimensional (3D) rigid tripod-pile groups subjected to combined vertical (V), horizontal (H), and bending moment (M) loads. Using the adaptive 3D finite element limit analysis (FELA) coupled with lower bound, upper bound and mixed Gauss element formulations, numerical results are compared with those of the previous study under a single-component loading (V, or H, or M). The failure envelope in the 3D V–H–M loading space is then constructed, and several failure mechanisms presented to complement the discussions on the complex 3D responses. This is followed by a parametric study for the various factors such as the pile length, pile spacing, pile-soil adhesion factors as well as the loading direction angle. Finally, a closed-form design expression of failure envelopes considering the abovementioned influential parameters and the combined load are derived. Noting that the current industry-based design procedures for tripod-pile groups are rarely found, the outcome of the present study can be used with great confidence in design practice.