Marketized allocation of factors is an important means to promote regional development, while the property rights system also has an important role in promoting regional development. In this paper, ...after constructing the index system of factor marketized allocation and rural property right legal system, respectively, taking 16 villages in X place as examples, the indexes are normalized, and the entropy method is used to measure the development level of the two over time. Combining the grey correlation analysis method can solve the correlation between factor marketized allocation and rural property rights legal system after completing the measurement. The study shows that the levels of factor marketization allocation and the development level of the property rights system are not high in place X from 2015 to 2020, with most of them located below 0.2 and 0.3, respectively. The mean level of the property rights system fluctuated greatly from 2015 to 2020, with the fastest growth rate of 12.38% in 2020. Overall, the factor of marketization allocation has the lowest correlation with the legal and political environment (0.69-0.79) and the highest correlation with property rights (0.72-0.90). The correlation between external capital acquisition and property rights is the highest (0.843), while the correlation between labor output and intellectual property rights is the lowest (0.693). By optimizing the legal system of property rights, it is possible to promote the development level of regional factor market allocation, according to this study.
Self‐healing polymers crosslinked by solely reversible bonds are intrinsically weaker than common covalently crosslinked networks. Introducing covalent crosslinks into a reversible network would ...improve mechanical strength. It is challenging, however, to apply this concept to “dry” elastomers, largely because reversible crosslinks such as hydrogen bonds are often polar motifs, whereas covalent crosslinks are nonpolar motifs. These two types of bonds are intrinsically immiscible without cosolvents. Here, we design and fabricate a hybrid polymer network by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks. The randomly branched polymer links such two types of bonds and forces them to mix on the molecular level without cosolvents. This enables a hybrid “dry” elastomer that is very tough with fracture energy 13500 Jm−2 comparable to that of natural rubber. Moreover, the elastomer can self‐heal at room temperature with a recovered tensile strength 4 MPa, which is 30% of its original value, yet comparable to the pristine strength of existing self‐healing polymers. The concept of forcing covalent and reversible bonds to mix at molecular scale to create a homogenous network is quite general and should enable development of tough, self‐healing polymers of practical usage.
A tough, self‐healing polymer network is fabricated by crosslinking randomly branched polymers carrying motifs that can form both reversible hydrogen bonds and permanent covalent crosslinks. The randomly branched polymer forces such two types of bonds to mix on the molecular level without cosolvents; this enables a hybrid “dry” elastomer with an exceptional combination of toughness and self‐healing ability.
Inspired by the electrostatic interaction between the oppositely charged ions, here we report the fabrication of a series of MXene-filled polymeric films possessing superior EMI shielding ...performance, accompanied with excellent in-plane TC, as well as distinguished Joule heating performance that allows for fast deicing.
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•Fabricating CS/MXene alternating layered films via LBL strategy.•Successful construction of continuous electrical/thermal conductive channel.•Absorption dominant (92%) EMI shielding with SSEt of 10, 650 dB cm2 g−1.•Excellent anisotropic thermal management capacity.•Distinguished Joule heating performance that allows for rapid deicing.
Polymeric composites that feature both highly efficient EMI shielding and rapid heat dissipation have long been attractive, but it remains a significant challenge to fulfill such goals by virtue of lower film thickness and less filler. Inspired by the electrostatic interaction between oppositely charged chitosan (CS) solution and transition metal carbide (MXene) slurry, here we report a series of CS/MXene alternating layered films by taking advantage of layer by layer assembly strategy. The resultant 35-μm thick CS/MXene multilayer film presents a maximum EMI SE of 40.8 dB, a high specific EMI SE (SSEt) of 10, 650 dB cm2 g−1, together with superior thermal conductivity (6.3 W m−1 K−1) and excellent Joule heating capacity. Thus, this research opens up a new horizon for achieving satisfying EMI shielding and heat dissipation capacity, which will further benefit the development of MXene‑based composite materials in next-generation electrical devices.
A strong and tough self-healing elastomer is prepared based on double reversible networks consisting of ionic interactions and Diels-Alder (D-A) crosslinks. The elastomer is synthesized through ...one-pot copolymerization of a pair of oppositely charged monomers and furan functionalized methacrylate (FMA), which is then crosslinked with 1,1'-(Methylenebis(4,1-phenylene))bis(1H-pyrrole-2,5-dione) (BMI) via Diels-Alder (D-A) reaction. The oppositely charged monomers form ionic bonds which can segregate into aggregates with a wide distribution of size. Under heating or external force, the aggregates can dissociate from small to big ones to dissipate amount of energy and endow the materials with high mechanical properties (13 MPa in strength, 480% in stretchability). While the D-A crosslinks act as covalent bonds at room temperature and endow the materials with high elasticity and fast shape recovery ability. These two reversible networks with different dynamics contribute to the multi-scale self-healing properties of the elastomer. As a result, the self-healing efficiency of the elastomer is as high as 86%.
A strong and tough self-healing elastomer with high mechanical properties (13 MPa in fracture strength, 480% in stretchability) and self-healing efficiency (86%) is prepared based on double reversible networks consisting of ionic interactions and Diels-Alder (D-A) crosslinks. Display omitted
•The elastomers have high mechanical properties (13 MPa in fracture strength, 480% in stretchability) and self-healing efficiency (86%).•The ionic aggregates have wide size distribution which can desegregate progressively to dissipate energy.•The D-A crosslinks endow the sample with fast recovery ability.•The ionic bonds are dynamic at room temperature while the D-A crosslinks are dynamic at high temperature.
Convolutional neural networks have recently been applied to ophthalmic diseases; however, the rationale for the outputs generated by these systems is inscrutable to clinicians. A visualization tool ...is needed that would enable clinicians to understand important exposure variables in real time.
To systematically visualize the convolutional neural networks of 2 validated deep learning models for the detection of referable diabetic retinopathy (DR) and glaucomatous optic neuropathy (GON).
The GON and referable DR algorithms were previously developed and validated (holdout method) using 48 116 and 66 790 retinal photographs, respectively, derived from a third-party database (LabelMe) of deidentified photographs from various clinical settings in China. In the present cross-sectional study, a random sample of 100 true-positive photographs and all false-positive cases from each of the GON and DR validation data sets were selected. All data were collected from March to June 2017. The original color fundus images were processed using an adaptive kernel visualization technique. The images were preprocessed by applying a sliding window with a size of 28 × 28 pixels and a stride of 3 pixels to crop images into smaller subimages to produce a feature map. Threshold scales were adjusted to optimal levels for each model to generate heat maps highlighting localized landmarks on the input image. A single optometrist allocated each image to predefined categories based on the generated heat map.
Visualization regions of the fundus.
In the GON data set, 90 of 100 true-positive cases (90%; 95% CI, 82%-95%) and 15 of 22 false-positive cases (68%; 95% CI, 45%-86%) displayed heat map visualization within regions of the optic nerve head only. Lesions typically seen in cases of referable DR (exudate, hemorrhage, or vessel abnormality) were identified as the most important prognostic regions in 96 of 100 true-positive DR cases (96%; 95% CI, 90%-99%). In 39 of 46 false-positive DR cases (85%; 95% CI, 71%-94%), the heat map displayed visualization of nontraditional fundus regions with or without retinal venules.
These findings suggest that this visualization method can highlight traditional regions in disease diagnosis, substantiating the validity of the deep learning models investigated. This visualization technique may promote the clinical adoption of these models.
In the present work, the influence of graphene (GE) on the vulcanization kinetics of natural rubber (NR) with sulfur curing system was investigated in detail for the first time. It is found that on ...adding graphene the induction period of the vulcanization process is remarkably depressed, whereas the vulcanization rate is enhanced at low graphene loading and then suppressed. As a result, the optimum cure time decreases dramatically at first and subsequently shows a slight increase with increasing graphene loading. At the same time, the crosslinking density of NR increases monotonically, because graphene takes part in the vulcanization process. The exothermal peak of the vulcanization reactions is split into two peaks on adding ≥0.5 phr graphene. It is interpreted in terms of two reaction stages, i.e., chemical reaction controlling stage and diffusion controlling stage. The activation energy of the former stage decreases with increasing graphene loading, while that of the latter stage is higher than the former one and increases with graphene loading. A possible mechanism was proposed to interpret the accelerating effect of graphene and the enhanced crosslinking density of NR.
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Piezoelectric materials have wide‐ranging applications owing to their capacity to convert mechanical energy into electrical energy in daily life scenarios. With rapid development in fields such as ...wearable electronics, intelligent electronic products, and medical equipment, the requirement for the elasticity of piezoelectric materials has become increasingly stringent. However, combining high piezoelectric performance with high elasticity in most conventional piezoelectric materials is challenging, limiting the application of piezoelectric elastomers in complex scenarios. Recently, several piezoelectric elastomer materials with good flexibility, high elasticity, and easy processing ability have been reported, and their applications in soft devices have rapidly developed. In this review, the current state of piezoelectric elastomers and their applications are systematically reviewed. Additionally, an overview of trends in the development of piezoelectric elastomer materials is given, providing a reference for future research in this field.
Piezoelectric materials enable the interconversion of mechanical and electrical energy, which are widely used for energy harvesting. Flexible piezoelectric elastomers are rapidly developed and have achieved many interesting applications in areas including wearable devices, medical equipment, and smart robots. In this context, a review aims to provide an update on the latest developments in elastomeric piezoelectric materials is imperative.
In the present work, we report for the first time the use of surface functionalized graphene oxide (SGO) with bis(triethoxysilylpropyl)tetrasulfide (BTESPT) as a multi-functional nanofiller for ...natural rubber (NR). Through a facile approach BTESPT molecules are successfully grafted onto the surface of graphene oxide. The resulting SGO can be finely dispersed in NR via solution mixing. It is found that SGO is prominent in improving the mechanical and gas barrier properties of NR at significantly low filler loading. The percolation point of SGO in the nanocomposites takes place at a content of less than 0.1 wt%. With incorporation of as low as 0.3 wt% of SGO, a 100% increase in the tensile strength, a 66% improvement in the tensile modulus and a 48% reduction in the air permeability are achieved without sacrificing the ultimate strain. This remarkable improvement in the mechanical and gas barrier properties of NR nanocomposites at such low filler loading is attributed to the strong interfacial interaction and the molecular-level dispersion of SGO in the NR matrix.
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To study the effect of aging on the low-temperature crack resistance of fiber asphalt mixes, three kinds of fibers (lignin fiber, polyester fiber, and basalt fiber) were dry blended into AC-13 ...asphalt mixes to prepare unaged, asphalt aged (that is, the original asphalt material is subjected to aging treatment), short-term aged, and long-term aged fiber reinforced asphalt mixes. Semicircular bending (SCB) tests and scanning electron microscopy tests were used to analyze and study the effects of aging time and fiber type on the low-temperature properties of asphalt mixtures at an ambient temperature of −5 °C. The SCB test results indicated that: with the deepening of aging, the fracture toughness and fracture energy of the fiber asphalt mixture specimens will tend to decrease, and the aging of the original asphalt has a greater impact on the specimens without fiber; there was great variability in the effect of lignin fibers on the crack resistance of the mix, but it could be a good promoter in unaged asphalt mixes; polyester fiber is the material of choice for improving low-temperature crack resistance in long-term aging pavements; the incorporation of basalt fiber greatly enhances the crack resistance of asphalt mixes and is an excellent material for improving aging asphalt mixes. It is clearly seen by the scanning electron microscope test that with the deepening of aging, the adhesion of asphalt and aggregate gradually deteriorates, and even more so, there is the phenomenon of fine aggregate flaking, and the fiber cannot play an excellent role in reinforcement and crack resistance.
The self-healable biomass aerogel is achieved by electrostatic interaction between the chitosan (CS) and itaconic acid (IA). Once the aerogel is cut apart, it can repair both its structure and ...mechanical performance within 30 s at room temperature via treatment of wetting. After self-healing for 100 s, it can even bear a weight which is almost 3300-fold heavier than the original weight of the aerogel itself.
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•Disclosing a new strategy for the fabrication of self-healable aerogels.•Ultrafast self-healing capacity was achieved under the stimulus of water.•CSA aerogels display excellent recyclability.•Showing outstanding mechanical property before and after self-healing.
Achieving self-healing capacity in porous materials is highly attractive, but still remains a huge challenge. Here we disclosed a new strategy for the fabrication of self-healable biomass aerogels, which is achieved by assembling the positively charged chitosan (CS) and negatively charged itaconic acid (IA) in aqueous solution, followed by a freeze-drying process. Due to relatively strong electrostatic interaction and unique morphology, the aerogel shows outstanding mechanical property even at very low apparent density. More importantly, it possesses ultrafast self-healing ability at room temperature. Once the aerogel is cut apart, it can repair both its structure integrity and mechanical performance within 30 s at room temperature via wetting one fractured surface. After self-healing, its compression strength is almost twice the value of the original one. In addition, the aerogel can be completely dissolved and reshaped, thus displaying excellent recyclability of the materials. Since both CS and IA are derived from natural resources, this work provides a promising solution to the fabrication of self-healable biomass aerogels with both high-performance and sustainability.
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