This study investigated the wettability of tectonic soft coal by analyzing the relationship between proximate analysis indexes, oxygen-containing functional groups, pore characteristics, hardness, ...gas adsorption capacity, and contact angles. Results show that coal was more hydrophilic with the increase of gas adsorption capacity, moisture content, ash content, and the content of Si–O–Si functional groups and was more hydrophobic with the increase of the fixed carbon content and coal hardness, while the correlation between volatile matter and wettability was not obvious. The isothermal adsorption/desorption curves of coal obtained from a low-temperature nitrogen adsorption experiment show that the greater the number of open pores and the better the connectivity of pores, the better the coal wettability. The pore fractal characteristic was analyzed with respect to two aspects: the coal surface roughness represented by the surface fractal dimension D 1 and the pore irregularity and complexity represented by the structure fractal dimension D 2. The relationships between D 1, D 2, and the contact angle show that with the increase of D 1 and D 2, the coal wettability becomes better, which indicates that the rougher the coal surface and the more complex the pore structure, the better the coal wettability.
The application of poly(lactic acid) (PLA) in the packaging area is frequently dwarfed by the inadequate gas/water barrier properties, low heat resistance and high UV transmittance. Herein, an ...environmentally friendly and high-efficiency microwave-assisted functionalization (MAF) approach was proposed to aqueous grafting waste bamboo fibers with the bridging agent. It permitted significant promotion of interfacial interactions between the MAF bamboo fibers (MAFBs) and neighboring PLA chains, contributing to uniform dispersion and intimate interphase. Featuring the morphological features, the MAFB-reinforced (5, 10 and 20 wt%) PLA biocomposites achieved an unexpected combination of high mechanical properties, exceptional resistance to heat deflection and UV irradiation, and excellent water barrier performance. Upon addition of only 5 wt% MAFBs, the tensile strength and toughness of PLA composite films were increased to 46.5 MPa and 0.6 MJ/m3, increasing over 52 % and nearly 107 % compared to those of the counterpart loaded pristine bamboo fibers (PBFs), respectively. This was favorably accompanied by the remarkably reduced water vapor permeability, falling down to the lowest value of 3.5 × 10−11 g∙m/Pa∙s∙m2 for PLA/MAFB (80/20) with a decrease of nearly 79 % compared to the counterpart. It is of interest to note the MAFB-enabled nearly 100 % UV-blocking ratio for PLA loaded 10 and 20 wt% fibers, as well as excellent resistance to heat deflection even at high temperatures like 120 °C. This effort paves the way to multifunctional natural fibers with high affinity to PLA for elegant implementation of high-heat and UV-resistant packaging materials in an ecofriendly manner.
The microwave-assisted functionalization (MAF) approach was proposed to construct intimate interphase for bamboo fiber-reinforced PLA biocomposites, contributing to improvements in water vapor barrier, heat resistance and UV-blocking properties in need for green packaging. Display omitted
•An aqueous microwave-assisted functionalization (MAF) approach was established.•MAF enabled ecofriendly and high-efficiency synthesis of functionalized bamboo fibers (MAFBs).•The MAFBs exhibited intimate affinity to poly(lactic acid) (PLA).•MAFBs endowed PLA with high resistance to heat deflection and nearly 100 % UV-blocking performance.
The concept of bio-inspired gradient hierarchies, in which the well-defined MOF nanocrystals serve as active nanodielectrics to create electroactive shell at poly(lactic acid) (PLA) nanofibers, is ...introduced to promote the surface activity and electroactivity of PLA nanofibrous membranes (NFMs). The strategy enabled significant refinement of PLA nanofibers during coaxial electrospinning (∼40 % decline of fiber diameter), accompanied by remarkable increase of specific surface area (nearly 1.5 m2/g), porosity (approximately 85 %) and dielectric constants for the bio-inspired gradient PLA (BG-PLA) NFMs. It largely boosted initial electret properties and electrostatic adsorption capability of BG-PLA NFMs, as well as charge regeneration by TENG mechanisms even under high-humidity environment. The BG-PLA NFMs thus featured exceptionally high PM0.3 filtration efficiencies with well-controlled air resistance (94.3 %, 163.4 Pa, 85 L/min), in contrast to the relatively low efficiency of only 80.0 % for normal PLA. During the application evaluation of outdoor air purification, excellent long-term filtering performance was demonstrated for the BG-PLA for up to 4 h (nearly 98.0 %, 53 Pa), whereas normal PLA exhibited a gradually declined filtration efficiency and an increased pressure drop. Moreover, the BG-PLA NFMs of increased electroactivity were ready to generate tribo-output currents as driven by respiratory vibrations, which enabled real-time monitoring of electrophysiological signals. This bio-inspired gradient strategy opens up promising pathways to engender biodegradable nanofibers of high surface activity and electroactivity, which has significant implications for intelligent protective membranes.
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•A bio-inspired strategy was unraveled to engender hierarchically gradient poly(lactic acid) (PLA) nanofibers.•The bio-inspired gradient PLA nanofibers exhibited high surface activity and enhanced electret mechanisms.•An impressive combination of efficient PM0.3 filtration and favorable breathability were demonstrated for the PLA NFMs.•The NFMs enabled real-time respiratory monitoring and self-powered wireless signal transmission.
Due to the complexity of head shape, limited 1D or 2D head anthropometry fail to fully capture its shape characteristics. Currently, there is limited research on clustering analysis of head shape ...from a shape difference perspective, especially for the head shape of Chinese people. Head shape is influenced by factors such as race, sex, and age, making it imperative to create a head shape database for Chinese individuals. In this study, three-dimensional head data of 339 Chinese young adult were collected, and the head shapes were clustered into 7 clusters using an improved k-medoids algorithm. The differences between clusters and the average head shape were further analyzed. It can be foreseen that the head shape database for Chinese young adult constructed in this study has important reference value for the ergonomic design of head-related products and head morphology research, among other fields.
Due to the complexity of head shape, limited 1D or 2D head anthropometry fail to fully capture its shape characteristics. Currently, there is limited research on clustering analysis of head shape ...from a shape difference perspective, especially for the head shape of Chinese people. Head shape is influenced by factors such as race, sex, and age, making it imperative to create a head shape database for Chinese individuals. In this study, three-dimensional head data of 339 Chinese young adult were collected, and the head shapes were clustered into 7 clusters using an improved k-medoids algorithm. The differences between clusters and the average head shape were further analyzed. It can be foreseen that the head shape database for Chinese young adult constructed in this study has important reference value for the ergonomic design of head-related products and head morphology research, among other fields. KEY WORDS: Anthropometry; Three-Dimensional Head; Shape Clustering; Shape Difference. Debido a la complejidad de la forma de la cabeza, la antropometria limitada de esta, en 1D o 2D, no logra capturar completamente sus caracteristicas de forma. Actualmente, existen estudios limitados sobre el analisis de agrupamiento de la forma de la cabeza, desde una perspectiva de diferencia de forma, especialmente en el caso de la poblacion china. La forma de la cabeza esta influenciada por factores como la raza, el sexo y la edad, por lo que resulta imperativo crear una base de datos sobre la forma de la cabeza de los individuos chinos. En este estudio, se recopilaron datos tridimensionales de la cabeza de 339 adultos jovenes chinos, y las formas de la cabeza se agruparon en 7 grupos utilizando un algoritmo k-medoids mejorado. Las diferencias entre los grupos y la forma promedio de la cabeza se analizaron a profundidad. Se puede prever que la base de datos sobre la forma de la cabeza de adultos jovenes chinos construida en este estudio, tiene un valor de referencia importante para el diseno ergonomico de productos relacionados con la morfologia de la cabeza, entre otros campos. PALABRAS CLAVE: Antropometria; Cabeza Tridimensional; Aglomeracion de formas; Diferencia de forma.
Despite great potential in fabrication of biodegradable protective membranes by electrospinning of poly(lactic acid) (PLA) nanofibers, it is still thwarted by smooth surfaces and poor electroactivity ...that challenge the promotion of electret properties and long-term air filtration performance. Here, a microwave-assisted synthetic method was used to customize dielectric TiO2 nanocrystals of ultrasmall and uniform dimensions (∼30 nm), which were homogeneously embedded at beaded PLA nanofibers (PLA@TiO2, diameter of around 280 nm) by the combined “electrospinning-electrospray” approach. With small amounts of TiO2 (2, 4 and 6 wt%), the nanopatterned PLA@TiO2 nanofibrous membranes (NFMs) were characterized by largely increased dielectric constants (nearly 1.9), surface potential (up to 1.63 kV) and triboelectric properties (output voltage of 12.2 V). Arising from the improved electroactivity and self-charging mechanisms, the nanopatterned PLA@TiO2 NFMs exhibited remarkable PM0.3 filtration properties (97.9 %, 254.6 Pa) even at the highest airflow rate of 85 L/min, surpassing those of pure PLA membranes (86.2 %, 483.7 Pa). This was moreover accompanied by inhibition rates of 100 % against both E. coli and S. aureus, as well as excellent UV-blocking properties (UPF as high as 3.8, TUVA of 50.9 % and TUVB of 20.1 %). The breathable and electroactive nanopatterned PLA NFMs permit promising applications in multifunctional protective membranes toward excellent UV shielding and high-efficiency removal of both PMs and pathogens.
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•Dielectric TiO2 nanocrystals of ultrasmall and uniform size were customized by a microwave-assisted approach.•A combined “electrospinning-electrospray” strategy was proposed to embed TiO2 nanoparticles at beaded poly (lactic acid) (PLA) nanofibers (PLA@TiO2).•Electret and tribo-output properties were largely promoted for the nanopatterned electroactive PLA@TiO2 nanofibrous membranes (NFMs).•The air-permeable and antibacterial PLA@TiO2 NFMs exhibited remarkable PM0.3 filtration (97.9 %, 85 L/min) and UV-shielding performance (UPF of 3.8).
Biodegradable polylactic acid (PLA) nanofibrous membranes (NFMs) hold great potential to address the increasing airborne particulate matter (PM) and dramatic accumulation of plastic/microplastic ...pollution. However, the field of PLA NFM-based filters is still in its infancy, frequently dwarfed by the bottlenecks regarding relatively low surface activity, poor electroactivity, and insufficient PM capturing mechanisms. This effort discloses a microwave-assisted approach to minute-level synthesis of dielectric ZIF-8 nanocrystals with high specific surface area (over 1012 m2/g) and ultrasmall size (∼240 nm), which were intimately anchored onto PLA nanofibers (PLA@ZIF-8) by a combined “electrospinning–electrospray” strategy. This endowed the PLA@ZIF-8 NFMs with largely increased electroactivity in terms of elevated dielectric coefficient (an increase of 202%), surface potential (up to 5.8 kV), and triboelectric properties (output voltage of 30.8 V at 10 N, 0.5 Hz). Given the profound control over morphology and electroactivity, the PLA@ZIF-8 NFMs exhibited efficient filtration of PM0.3 (97.1%, 85 L/min) with a decreased air resistance (592.5 Pa), surpassing that of the pure PLA counterpart (88.4%, 650.9 Pa). This was essentially ascribed to realization of multiple filtration mechanisms for PLA@ZIF-8 NFMs, including enhanced physical interception, polar interactions, and electrostatic adsorption, and the unique self-charging function triggered by airflow vibrations. Moreover, perfect antibacterial performance was achieved for PLA@ZIF-8, showing ultrahigh inhibition rates of 99.9 and 100% against E. coli and S. aureus, respectively. The proposed hierarchical structuring strategy, offering the multifunction integration unattainable with conventional methods, may facilitate the development of biodegradable long-term air filters.
The rapid development of signal processing technology has improved the stability and anti-interference ability of gas sensors in electronic noses (E-noses). However, the interference and noise caused ...by temperature and humidity in the environment are still inevitable in real detection conditions, which can cause data fluctuation during the recognition process. In traditional pattern recognition, the data fluctuation would reduce the difference between extracted features and the accuracy of gas classification. This study proposes a 1-D convolutional neural network (1DCNN) with the Savitzky-Golay (SG) filter. The SG filter is added before the convolution layer in the 1DCNN to automatically remove the noise of the sensor array data. The model can improve the effectiveness of the convolution layer to obtain features, omit the tedious preprocessing steps, and directly complete the identification process from raw data to results. The 1DCNN with SG filter is employed for the recognition of four gases: methane, ethanol, ethylene, and carbon monoxide. The results show that the accuracy of the 1DCNN with SG filter (99.21%) is 4% higher than that of the CNN (95.31%). Furthermore, the 1DCNN with SG filter is utilized for classifying a diverse assortment of mixed gases, ultimately achieving a classification accuracy of 99.8%. This study demonstrates the effectiveness of a novel CNN model with an SG filter, which streamlines the data processing and significantly improves the accuracy and efficiency of gas recognition in E-noses.
The presence of leakage in respiratory protective equipment undermines its intended efficacy in protection. Therefore, the real-time monitoring of leakage in respiratory protective equipment is of ...paramount importance. In this work, a lead-free humidity sensor based on Cs3Cu2I5 nanorods was utilized to achieve the leakage detection of respiratory protective equipment. Addition of the organometallic ligand Al(acac)3 improved the stability of the material and contributes to long-lasting stable applications. Cyclic response testing demonstrated rapid response/recovery times of 2.98/2.96 s in the humidity range 20∼80% RH. Further explanation of the moisture sensitivity mechanism and rationalization of RPE leakage monitoring through humidity were explored by density functional theory calculation and computational fluid dynamics calculation. Then, the sensor array was integrated into the respirator and combined with a deep learning algorithm to detect leakage. The results showed that respirator leakage can be effectively identified with an average accuracy of 94.4%, which contributes to the protection of workers’ health.
