The fire detection plays a critical role in the maintenance of public security. Previous approaches of early fire warning, based on smoke or temperature response must be set in the proximity of a ...fire. They cannot provide the additional information of fire location or size and are susceptible to complicated situations. It is still a big challenge to make rapid and accurate early fire warning in precombustion because of the lack of reliable alarm signals. Herein, a precursor molecular sensor (PMS) is designed and synthesized that can present the chemical structure transformation to form phthalocyanines (Pcs) and release a color change signal at about 180 °C, learning from the plant chlorophyll metabolism. Further, the PMS is assembled to an early fire warning component (EWC) and an intelligent image recognition algorithm is introduced for unburned fire detection. The EWC generates a colorful alarm within 20 s at 275 °C. Therefore, the facile PMS provides a reliable real‐time monitoring strategy to the early fire warning detection in precombustion.
A bioinspired color changing molecular sensor is designed to achieve early fire detection based on transformation of phthalonitrile to phthalocyanine, learning from the plant chlorophyll metabolism. An intelligent image recognition algorithm is applied and the sensor generates colorful alarm within 20 s at 275 °C. This study provides a reliable real‐time monitoring strategy to the early fire detection in precombustion.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Bioresorbable electronics refer to a new class of advanced electronics that can completely dissolve or disintegrate with environmentally and biologically benign byproducts in water and biofluids. ...They have provided a solution to the growing electronic waste problem with applications in temporary usage of electronics such as implantable devices and environmental sensors. Bioresorbable materials such as biodegradable polymers, dissolvable conductors, semiconductors, and dielectrics are extensively studied, enabling massive progress of bioresorbable electronic devices. Processing and patterning of these materials are predominantly relying on vacuum‐based fabrication methods so far. However, for the purpose of commercialization, nonvacuum, low‐cost, and facile manufacturing/printing approaches are the need of the hour. Bioresorbable electronic materials are generally more chemically reactive than conventional electronic materials, which require particular attention in developing the low‐cost manufacturing processes in ambient environment. This review focuses on material reactivity, ink availability, printability, and process compatibility for facile manufacturing of bioresorbable electronics.
Bioresorbable electronics, a new class of advanced electronics that can completely disintegrate or dissolve in water/biofluids, has drawn tremendous attention with applications in biomedical implantable devices and environmental sensors. Material reactivity, ink availability, and printability and process compatibility are reviewed, aiming at realizing nonvacuum, low‐cost, and facile manufacturing of bioresorbable electronics.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To systematically study how the H‐bonding interaction affect the flame retardancy and anti‐dripping behavior of poly(ethylene terephthalate) (PET), two series of PET‐based copolyesters are prepared ...by introducing two benzimidazole monomers with similar structure. One (2‐(4‐methoxycarbonyl‐phenyl)‐1H‐benzimidazole‐5‐carboxylic acid methyl ester, PBM) contains H‐bonding donor, the other (2‐(4‐methoxycarbonyl‐phenyl)‐1‐methylbenzimidazole‐5‐carboxylic acid methyl ester, PNM) weeds out the H‐bonding donor by replacing NH group with NCH3. The dynamic rheological behavior, fire resistance and fire‐retardant mechanism of the PET‐co‐PBMs and PET‐co‐PNMs are contrastively investigated. PET‐co‐PNMs have flow behaviors similar to neat PET. While, for PET‐co‐PBMs, the movements of the molecular chains are restricted due to the H‐bonding interaction, leading to higher melt viscosity, which is conducive to the anti‐dripping property. It can be proved that benzimidazole groups promote the carbonization of substrates to form more stable charred layers in combustion, showing an obvious barrier action in condensed phase. Unfortunately, the enhancement of carbonization alone is not enough to inhibit the dripping behavior satisfactorily, and PET‐co‐PNMs fail to pass UL‐94 V‐0 rating. While, PET‐co‐PBMs exhibit better self‐extinguishing and anti‐dripping performances benefiting from strong H‐bonding interactions. The revealed effects of H‐bonding interactions on the fire resistance and anti‐dripping behavior of polymers will guide further design of flame retardants.
Two PET‐based copolyesters containing benzimidazole structure, one with hydrogen bond donor (2‐(4‐methoxycarbonyl‐phenyl)‐1H‐benzimidazole‐5‐carboxylic acid methyl ester, PBM), the other without hydrogen bond donor (2‐(4‐methoxycarbonyl‐phenyl)‐1‐methylbenzimidazole‐5‐carboxylic acid methyl ester, PNM), show different rheological behavior and fire resistance. H‐bonding can reduce the fluidity of burning melt and provide more time for charring, endowing PET‐co‐PBMs with better self‐extinguishing and anti‐dripping performances than PET‐co‐PNMs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The practical problems of insufficient mechanical strength, poor processability, tedious synthesis and flammability facing shape memory polymers have limited their further usage in industrial fields, ...especially in construction and aerospace. A novel and very simple method of ternary polymerization is presented here to prepare multi-functional copolyesters from general poly(ethylene terephthalate) (PET) through the new well-designed third monomer that features pendent phenylacetylene–phenylimide units. The π–π stacking between phenylacetylene groups as a reversible net-point not only endows the copolyesters with good shape memory and self-healability, but also reinforces the interchain interaction, leading to high tensile strength (79.6–89.6 MPa). Interestingly enough, the phenylacetylene can synergistically crosslink with the unsaturated CN group generated from the phenylimide during burning, resulting in excellent flame retardancy. Thermoplastic smart copolyesters can be designed into fire alarms and can also be used for 3D printing. The printed geometries exhibit good shape memory behaviors, which could be deformed into a small size to save space during transportation/storage and allow manufacturing freedom for space applications.
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•A fire-safe tactic with nitrogen/phosphorus-free molecules is proposed.•Aryl ether ketone structure decreases the chemical risks of flame retardant issues.•Fire safety is acchieved ...by binding aliphatic fragments and aromatized charring.
Previous approaches to suppressing fire hazards are concentrated on brominated flame retardants (BFRs) or phosphorus flame retardants (PFRs). However, their chemical hazards to health and environment have not been able to be ignored currently. It is quite urgent to propose a durable and environmentally-friendly fire-safe strategy, which can eliminate migration, release, and environmental hazards of traditional flame retardants during their use, disposal, and recycling. Herein, we design a fire-responsive molecule (FRM) only containing C, H, and O elements based on full-life-cycle consideration and achieve fire safety via the synergy of specifically binding aliphatic fragments and aromatized charring in combustion. The resulting polymer shows low fire hazard with excellent self-extinguish, low organic volatiles/heat/smoke release, and good comprehensive performance. This polymer can be fabricated to fibres with potential applications for textiles, and electronics, etc. Therefore, we achieve a durable fire-safe strategy without flame-retardant chemicals hazard. This approach can fundamentally eliminate the potential chemical hazards associated with the introduction of halogen or phosphorus flame retardants and give a new vision about solving the “flame retardant chemical hazard issues” that are debated, tracked, and evaluated for several decades.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The pseudospin symmetry (PSS) is an important physical concept in atomic nuclei. The relativistic point-coupling model is first used to explore the origin and breaking mechanism of PSS in ...real nuclei with
208
Pb as an illustrated example. PSS observed in the single particle spectra of heavy nuclei is reproduced in the present calculation. The influences of the different point-coupling interactions on PSS are investigated, it is found that the four-fermion scalar and vector couplings play a dominate role at PSS. The quality of PSS depends on the competition of four-fermion scalar and vector couplings. Those the PSS is better for the weakly bound levels and the energy splittings are more sensitive to the interaction strengths for the deeply bound levels are well explained in terms of the derivative of Σ potential with
r
. In combination with the similarity renormalization group, the origin and breaking mechanism of PSS are clarified.
Aircraft type recognition from remote sensing images has many civil and military applications. In images obtained with modern technologies such as high spatial resolution remote sensing, even details ...of aircraft can become visible. With this, the identification of aircraft types from remote sensing images becomes possible. However, the existing methods for this purpose have mostly been evaluated on different data sets and under different experimental settings. This makes it hard to compare their results and judge the progress in the field. Moreover, the data sets used are often not publicly available, which brings difficulties to reproduce the works for fair comparison. This severely limits the progress of research and the state of the art is not entirely clear. To address this problem, we introduce a new benchmark data set for aircraft type recognition from remote sensing images. This data set is called Multi-Type Aircraft Remote Sensing Images (MTARSI), which contains 9’385 images of 20 aircraft types, with complex backgrounds, different spatial resolutions, and complicated variations in pose, spatial location, illumination, and time period. The publicly available MTARSI data set allows researchers to develop more accurate and robust methods for both remote sensing image processing and interpretation analysis of remote sensing object. We also provide a performance analysis of state-of-the-art aircraft type recognition and deep learning approaches on MTARSI, which serves as baseline result on this benchmark.
•A diverse remote sensing image data set for aircraft type recognition is presented.•Up-to-date algorithms for aircraft recognition of remote sensing images is reviewed.•The results obtained with state-of-the-art approaches can be served as baseline.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A novel benzimidazole monomer was incorporated into the chain structure of PET.•Physical networks are formed in the copolyesters via H-bonding and π-π stacking.•Physical networks ...improve the melt strength and retard the melt-dripping greatly.•Copolyesters with no-dripping and low smoke release show excellent fire safety.•Copolyesters exhibit high Tg, high tensile strength and good processability.
Currently, it is still a huge challenge to prepare flame-retardant polymeric materials with excellent fire safety, high strength, good durability and processability. We here propose a H-bonding cross-linking strategy that can simultaneously endow polymers with excellent flame retardancy, non-dripping behavior and enhanced strength. In this work, a novel benzimidazole monomer, 2-(4-methoxycarbonyl-phenyl)-1H-benzimidazole-5-carboxylic acid methyl ester (PBM) has been designed as a H-bonding cross-linking monomer to prepare poly(ethylene terephthalate)-based copolyesters (PET-co-PBMs). Interestingly, along with the hydrogen bonding, the π-π stacking interactions from the benzimidazole groups also exist. Due to the formation of physical crosslinking network via hydrogen bonding and π-π stacking, the melt strength of copolyesters are greatly improved. Combining with char forming ability of benzimidazole, PET-co-PBMs display excellent fire safety. Moreover, PET-co-PBMs also exhibit higher glass transition temperature, higher mechanical strength and good processability. This work provides a promising strategy to design polymers with high strength, good processability, excellent flame retardance and anti-dripping performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Background： The lateral pillar of the femoral head is an important site for disease development such as osteonecrosis of the femoral head. The femoral head consists of medial, central, and lateral ...pillars. This study aimed to determine the biomechanical effects of early osteonecrosis in pillars of the femoral head via a finite element （FE） analysis. Methods： A three-dimensional FE model of the intact hip joint was constructed from the image data of a healthy control. Further, a set of six early osteonecrosis models was developed based on the three-pillar classification. The von Mises stress and surface displacements were calculated for all models. Results： The peak values of von Mises stress in the cortical and cancellous bones of normal model were 6.41 MPa and 0.49 MPa, respectively. In models with necrotic lesions in the cortical and cancellous bones, the von Mises stress and displacement of lateral pillar showed significant variability： the stress of cortical bone decreased from 6.41 MPa to 1.51 MPa （76.0% reduction）, while cancellous bone showed an increase from 0.49 MPa to 1.28 MPa （159.0% increase）; surface displacements of cortical and cancellous bones increased from 52.4 μm and 52.1 μm to 67.9 μm （29.5%） and 61.9 μm （18.8%）, respectively. In addition, osteonecrosis affected not only pillars but also adjacent structures in terms of the von Mises stress and surface displacement levels. Conclusions： This study suggested that the early-stage necrosis in the femoral head could increase the risk of collapse, especially in lateral pillar. On the other hand, the cortical part of lateral pillar was found to be the main biomechanical support of femoral head.
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