Search

Flexible, wearable pressure sensors offer numerous benefits, including superior sensing capabilities, a lightweight and compact design, and exceptional conformal properties, making them highly sought after in various applications including medical monitoring, human–computer interactions, and electronic skins. Because of their excellent characteristics, such as simple fabrication, low power consumption, and short response time, capacitive pressure sensors have received widespread attention. As a flexible polymer material, polydimethylsiloxane (PDMS) is widely used in the preparation of dielectric layers for capacitive pressure sensors. The Young's modulus of the flexible polymer can be effectively decreased through the synergistic application of sacrificial template and laser ablation techniques, thereby improving the functionality of capacitive pressure sensors. In this study, a novel sensor was introduced. Its dielectric layer was developed through a series of processes, including the use of a sacrificial template method using NaCl microparticles and subsequent CO2 laser ablation. This porous PDMS dielectric layer, featuring an array of holes, was then sandwiched between two flexible electrodes to create a capacitive pressure sensor. The sensor demonstrates a sensitivity of 0.694 kPa−1 within the pressure range of 0–1 kPa and can effectively detect pressures ranging from 3 Pa to 200 kPa. The sensor demonstrates stability for up to 500 cycles, with a rapid response time of 96 ms and a recovery time of 118 ms, coupled with a low hysteresis of 6.8%. Furthermore, our testing indicates that the sensor possesses limitless potential for use in detecting human physiological activities and delivering signals. [ABSTRACT FROM AUTHOR]

The development of renewable polymers as alternatives to the petroleum-based ones has received significant attention due to the increasing depletion of fossil oil and the associated environmental concerns. In this study, a semi-biomass-based polyimide (PI) film was successfully synthesized, using biomass-derived furfural (HMFA) as one of the raw materials. A two-step approach was first developed for this process: (1) conversion of HMFA to 3,3,4,4-biphenyltetracarboxylic acid dianhydride (BPDA) and (2) polymerization of BPDA with p-phenylenediamine (PPD) to form a PI film. The fabricated PI film demonstrated excellent properties, such as a high thermal decomposition temperature up to 600 °C, a satisfactory glass transition temperature (Tg) exceeding 365 °C, a coefficient of thermal expansion (CTE) of ≈30 ppm/K, a tensile strength greater than 120 MPa, a dielectric constant value below 3.4, a dielectric loss value of less than 0.02, and a 24 h water absorption rate below 0.8%. These performances are comparable to the petrochemical-based PI. This work offers a promising strategy for utilizing biomass-derived materials in polyimide synthesis and would drive a new wave of advancements in polymer science. [ABSTRACT FROM AUTHOR]

The acquisition of dynamic coastline change at fine spatial and temporal resolution is essential for enhancing sustainable coastal economic development and coastal environmental conservation. Port construction, land reclamation, urban development, and sediment deposition have resulted in extensive coastline change. In this study, the coastlines along the 56 coastal countries in 1990, 2000, 2010, 2015, and 2020 were delineated and classified into six categories using Landsat time–series images. Five relevant indices, i.e., the length, length ratio, length change rate, index of coastline utilization degree (ICUD), and fractal dimension (FD), were calculated to analyze and explore the spatiotemporal pattern of the coastlines. The results indicate that: (1) The overall length of the coastlines has increased from 3.45 × 105 km to 3.48 × 105 km in the past 30 years, with a net increase of nearly 3904 km. Between 1990 and 2020, the length of the artificial coastline increased by about 13,835 km (4.9~8.8%), while the length of the natural coastline decreased by 9932 km (95.1~91.2%). The increase in artificial coastline is concentrated in Southeast Asia and South Asia. (2) The coastline fractal dimensions (FDs) of countries and continents show that the average FD values of countries in South Asia (1.3~1.4) and Southeast Asia (1.2~1.3) were higher than other countries in the study regions, meaning that the coastlines in South Asia and Southeast Asia are more complex and curved. (3) The value of the ICUD index increased consistently between 1990 and 2015 (177.7~186.6) but decreased sharply between 2015 and 2020 (186.6~162.4), implying that the impact of human activities on the coastline continued to increase until 2015 and began to decrease after 2015. Our study examined the changes in various types of coastlines, which could be significant for sustainable development and environmental protection in coastal areas. [ABSTRACT FROM AUTHOR]

In order to obtain the leakage characteristics of an upstream pumping face seal with inclined ellipse dimples under high-temperature and high-speed liquid lubricating conditions, a thermo-hydrodynamic lubricating model is developed. The novelty of this model is that it takes the thermo-viscosity effect and cavitation effect into account. The influence of operating parameters, such as rotational speed, seal clearance, seal pressure, ambient temperature and structural parameters, such as dimple depth, inclination angle, slender ratio and dimple number on the opening force and leakage rate, is numerically calculated. The results obtained show that the thermo-viscosity effect makes the cavitation intensity decrease noticeably, leading to an increase in the upstream pumping effect of ellipse dimples. Moreover, the thermo-viscosity effect may make both the upstream pumping leakage rate and opening force increase by about 10%. It can also be found that the inclined ellipse dimples can produce an obvious upstream pumping effect and hydrodynamic effect. Based on the reasonable design of the dimple parameter, not only can the sealed medium achieve zero leakage, but the opening force can also increase by more than 50%. The proposed model has the potential to provide the theoretical basis for and guide the future designs of upstreaming liquid face seals. [ABSTRACT FROM AUTHOR]

Furan-based compounds are a new class of compounds characteristic of wide abundance, feasible availability, and environmental friendliness. Presently, polyimide (PI) is the best membrane insulation material in the world, which is widely used in the fields of national defense, liquid crystals, lasers, and so on. At present, most polyimides are synthesized using petroleum-based monomers bearing benzene rings, while furan-based compounds bearing furan rings are rarely used as monomers. The production of petroleum-based monomers is always associated with many environmental issues, and their substitution with furan-based compounds seems a solution to addressing these issues. In this paper, t-butoxycarbonylglycine (BOC-glycine) and 2,5-furandimethanol, bearing furan rings, were employed to synthesize BOC-glycine 2,5-furandimethyl ester, which was further applied for the synthesis of furan-based diamine. This diamine is generally used to synthesize bio-based PI. Their structures and properties were thoroughly characterized. The characterization results showed that BOC-glycine could be effectively obtained using different posttreatment methods. And BOC-glycine 2,5-furandimethyl ester could be effectively obtained by optimizing the accelerating agent of 1,3-dicyclohexylcarbodiimide(DCC) with either 1.25 mol/L or 1.875 mol/L as the optimum value. The PIs originated from furan-based compounds were synthesized and their thermal stability and surface morphology were further characterized. Although the obtained membrane was slightly brittle (mostly due to the less rigidity of furan ring as compared with benzene ring), the excellent thermal stability and smooth surface endow it a potential substitution for petroleum-based polymers. And the current research is also expected to shed some insight into the design and the fabrication of eco-friendly polymers. [ABSTRACT FROM AUTHOR]

As the boundary between the sea and the land, information on the location and type of coastline constantly changes with environmental changes in coastal zones. Monitoring of coastline changes in long time series becomes important for the monitoring and assessment of the coastal zone environment. In this study, Landsat series images from five time periods (1990, 2000, 2010, 2015, and 2020) were selected for monitoring and analyzing the changes in coastline length, sea–land pattern, the index of coastline diversity, and fractal dimension characteristics. Our conclusions are as follows: (1) The lengths of the entire coastline and the artificial coastline of mainland China increased from 30,041.22 km and 10,022.49 km in 1990 to 32,977.34 km and 17,660.84 km in 2020, with annual change rates of 97.87 km/year and 254.61 km/year, respectively. From 1990 to 2020, the rate of natural coastline decreased from 66.68% to 42.29%, and the artificial coastline increased from 33.32% to 57.71%. (2) The length of natural coastline decreased from 20,018.73 km to 15,316.5 km; among the types of natural coastline, the length of sandy coastline and bedrock coastline decreased the most, at 2062.95 km and 1815.8 km, respectively. (3) The coastal zone of mainland China had a significant increase in land area, with a net increase of about 10,902.55 km2. (4) The index of coastline diversity continued to decrease, and the coastline structure tended to be simple. The fractal dimension of the mainland coastline was consistent with the trend of the length of the coastline, which basically shows an increasing trend. Therefore, the length of the mainland coastline and artificial coastline displayed an upward trend between 1990 and 2020, which also led to simpler coastline diversity and more complex coastline shapes. Since the first year of the SDGs (2015), the growth rate of the artificial coastline has decreased by 158.32 km/year compared with that between 2010 and 2015. In recent years, China has enacted a number of laws, regulations, and action plans to protect its coastline, and it has proposed that by 2020, the proportion of natural coastline will be no less than 35%. The rapid development of China's coastal areas drives the construction of coastal zone cities but also creates a variety of challenges for the ecological environment of the coastal zone, and the management and sustainable use of the mainland coastline resources should be further strengthened. [ABSTRACT FROM AUTHOR]

Polyimide (PI) membrane is an ideal gas separation material due to its advantages of high designability, good mechanical properties and easy processing; however, it has equilibrium limitations in gas selectivity and permeability. Introducing nanoparticles into polymers is an effective method to improve the gas separation performance. In this work, nano-attapulgite (ATP) functionalized with KH-550 silane coupling agent was used to prepare polyimide/ATP composite membranes by in-situ polymerization. A series of characterization and performance tests were carried out on the membranes. The obtained results suggested a significant increase in gas permeability upon increasing the ATP content. When the content of ATP was 50%, the gas permeability of H2, He, N2, O2, CH4, and CO2 reached 11.82, 12.44, 0.13, 0.84, 0.10, and 4.64 barrer, which were 126.87%, 119.40%, 160.00%, 140.00%, 150.00% and 152.17% higher than that of pure polyimide, respectively. No significant change in gas selectivity was observed. The gas permeabilities of membranes at different pressures were also investigated. The inefficient polymer chain stacking and the additional void volume at the interface between the polymer and TiO2 clusters leaded to the increase of the free volume, thus improving the permeability of the polyimide membrane. As a promising separation material, the PI/ATP composite membrane can be widely used in gas separation industry. [ABSTRACT FROM AUTHOR]

The development of robust and efficient electrocatalysts for use in fuel cells and metal–air batteries has garnered a great deal of interest due to the quest for clean and renewable energy sources. In this paper, a promising Co-doped Pr0.5Ba0.4Ca0.1Fe1-xCoxO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8; denoted as PBCFC-x, x = 0, 2, 4, 6, 8) with enhanced durability and electrocatalytic ORR/OER activity for zinc–air battery cathode catalysts is presented. Particularly, PBCFC-6 exhibits the best bifunctional catalytic activity in alkaline media among several materials, according to research using the RDE. The zinc–air battery with PBCFC-6 as the cathode catalyst delivered the smallest discharge–charge voltage difference at the current density of 10 mA·cm−2 and only increased by 0.031 V after 220 cycles (220 h), demonstrating its superior bifunctional catalytic activity and durability. The optimized electrochemical performance of both OER and ORR as well as stability in zinc–air batteries might result from the higher electrical conductivity, increasing concentration of adsorbed oxygen, and the greater proportion of Fe4+ (t2g3eg1) with optimal electron occupancy, owing to the partial replacement of Fe with Co. [ABSTRACT FROM AUTHOR]

The preparation of powdered microcapsules of flavor substances should not only protect these substances from volatilization during storage but also improve their diffusion during use. This study aimed to investigate the effects of maltodextrin (MD) with different dextrose equivalent (DE) values on retention of flavor substances during storage, and the dynamic release of flavor substances during dissolution. MDs with three different DE values and whey protein isolate were mixed in a ratio of 4:1 as wall materials to encapsulate ethyl acetate, and powdered microcapsules were prepared by spray drying. It was proved that MD could reduce the diffusion of flavor substances under different relative humidity conditions through the interaction between core material and wall material. During dissolution, MD released flavor substances quickly owing to its superior solubility. The reconstituted emulsion formed after the powder dissolved in water recaptured flavor substances and made the system reach equilibrium. This study explored the mechanism of flavor release during the storage and dissolution of powder microcapsules and should help us understand the application of powder microcapsules in food systems. [ABSTRACT FROM AUTHOR]

Static multi-controller deployment architecture cannot adapt to the drastic changes of network traffic, which will lead to a load imbalance between controllers, resulting in a high packet loss rate, high latency, and other network performance degradation problems. In this paper, an efficient dynamic load balancing scheme based on Nash bargaining is proposed for a distributed software-defined network. Firstly, considering the connectivity of network nodes, the switch migration problem is transformed into a network mapping relationship reconstruction problem. Then, we establish the Nash bargaining game model to fairly optimize the two contradictory goals of migration cost and load balance. Finally, the model is solved by an improved firefly algorithm, and the optimal network mapping state is obtained. The experimental results show that this scheme can optimize the migration cost and load balance at the same time. Compared with the existing research schemes, the migration process of the switch is optimized, and, while effectively balancing the load of the control plane, the migration cost is reduced by 14.5%. [ABSTRACT FROM AUTHOR]

In this study, soymilk was hydrolyzed to different degrees with flavourzyme, and then soymilk and enzyme modified soymilk at various levels were added to skim milk respectively, to generate a mixed gel using rennet. Rheological properties, scanning electron microscopy imaging, and physical and chemical indexes were examined to reveal the effect of enzyme modified soymilk on rennet induced gelation of skim milk. Results showed that soymilk inhibited the aggregation of skim milk, led to a decrease in storage modulus (G'), significantly increased moisture content and curd yield, and the resulting network was coarse. Enzyme modified soymilk with a molecular weight below 20 kDa led to a more uniform curd distribution, which counteracted the reduction of G' and allowed for the formation of a stronger gel. Both the moisture content and the curd yield increased with the addition of soymilk and enzyme modified soymilk, and overall the effect of adding a high degree of hydrolysis of enzyme modified soymilk was superior. Compared to untreated soymilk, the addition of a certain amount of enzyme modified soymilk resulted in a new protein structure, which would improve the texture of blend cheese. [ABSTRACT FROM AUTHOR]