Experimental Investigation on the Acoustic Insulation Properties of Filled Paper Honeycomb-Core Wallboards.

Honeycomb plates, due to their multi-cavity structure, exhibit excellent mechanical properties and sound insulation. Previous studies have demonstrated that altering the cell size and arrangement of honeycomb structures impacts their acoustic performance. Based on these findings, this study developed a wallboard structure with enhanced sound insulation by filling the cavities with paper fiber/cement facesheets and designing a stacked core structure. Through the reverberation chamber-anechoic chamber sound insulation experiment under 100-6300 Hz excitation and conducting orthogonal experiments from three dimensions, it was found that: (1) Compared to no filling, the filling with straw and glazed hollow bead can increase the sound transmission loss (STL) by more than 50% in the frequency bandwidth above 2000 Hz. This indicates that both types of fillings can significantly enhance the sound insulation performance of the honeycomb structure without a significant increase in economic costs. (2) The increase in paper fiber/cement facesheets improves the STL across the entire experimental bandwidth, with a maximum improvement exceeding 70%. This structural design not only offers superior sound insulation performance but also better suits practical engineering applications. (3) Increasing the number of core stacking units (from one to three), taking straw-filled paper honeycomb-core wallboards as an example, effectively increased the STL bandwidth. (4) This test enriches the application of honeycomb plates in sound insulation. Introducing fiber paper fiber/cement facesheets and eco-friendly, low-cost straw improves sound insulation and enhances the strength of honeycomb, making them more suitable for construction, particularly as non-load-bearing structures.

Shape-Regulated Motion and Energy Conversion of Polyelectrolyte Membrane Actuators.

Smart actuators hold great potential in soft robotics and sensors, but their movement at the fluid interface is less understood and controlled, hindering their performances and applications in complicated fluids. Here an ethanol-containing polyelectrolyte actuator is prepared that demonstrates excellent actuating performance via the Marangoni effect. These actuators exhibit enduring (17 min), repeatable (50 cycles), and autonomous motion on the water surface. More importantly, the motion of actuators are dependent on their shapes. Polygonal actuators with more edges exhibit round motion attached to walls of containers, while the actuators with few edges move randomly. On the basis of this property, the circular actuators can pass through pipe bends with S-shaped complex geometry. These unique advantages lend the actuators to successful applications in wireless sensing (standard 0-5 V level signals) for locating obstructions inside invisible pipes and continuous energy harvesting (7700 nC per cycle) for micro mechanical energy.

Shearo-caloric effect enhances elastocaloric responses in polymer composites for solid-state cooling.

Room-temperature elastocaloric cooling is considered as a zero-global-warming-potential alternative to conventional vapor-compression refrigeration technology. However, the limited entropy and large-deformation features of elastocaloric polymers hinder the creation of the breakthrough in their caloric responses and device development. Herein, we report that the addition of a small amount of inorganic nanofillers into the polymer induces the aggregate of the effective elastic chains via shearing the interlaminar molecular chains, which provides an additional contribution to the entropy in elastocaloric polymers. Consequently, the adiabatic temperature change of -18.0 K and the isothermal entropy change of 187.4 J kg-1 K-1 achieved in the polymer nanocomposites outperform those of current elastocaloric polymers. Moreover, a large-deformation cooling system with a work recovery efficiency of 56.3% is demonstrated. This work opens a new avenue for the development of high-performance elastocaloric polymers and prototypes for solid-state cooling applications.

Recent Progress of Functional Solvent-free Nanofluids: A Review.

Nanoparticles have aroused widespread interest because of their unique surface structure and nano effect, which presents novel characteristics like as sound, light, electricity, magnetism, and thermal properties. However, two critical defects have hindered their applications: (1) poor processability resulting from the high melting temperature (e.g., >1000 °C) for some inorganic nanoparticles; (2) the restriction of the nano effect caused by the easy aggregation of the nanoparticles. To solve those issues, solvent-free nanofluids (SNFs) with hard cores and flexible organic chains were successfully designed and fabricated at the beginning of the twenty-first century. The promising technology of SNFs not only solved the dispersion problem of nanomaterials but also imparted novel functionalization to nanoparticles. Up to now, many researchers have been devoted to developing diverse cores and flexible organic polymer chains to endow SNFs with particular functions, such as conductivity, fluorescence, lubricity, and so on. However, there are few review reports on the research progress in the fabrication and applications of functional SNFs. To gain a better understanding of SNFs, this paper presents an overall investigation into the development, fabrication, as well as the applications of functional SNFs.

The Establishment of a precise intelligent evaluation system for sports events: Diving.

The introduction of action quality assessment technology in sports events to achieve precise intelligent evaluation can greatly enhance the objectivity and effectiveness of competition results. Taking diving as the specific application background, this study proposes a novel Multi-granularity Extraction Approach for Temporal-spatial features in judge scoring prediction (MEAT) under the conditions of action quality assessment. On the one hand, it uses dual-modal inflated 3D ConvNet to extract the temporal and spatial features of each modal diving video at the video granularity parallelly and to merge them to form a global feature. On the other hand, the human body pose is modeled, and the simulated athlete's three-dimensional splash state is taken as local characteristics at the object granularity. Finally, the global and local features are concatenated into the fully connected layer, and heuristic method inspired by competition rules using labeled distribution learning are employed to output the probability distribution of the average score of all referees. The maximum probability score is selected and multiplied by the difficulty coefficient to obtain the final diving score. Through comprehensive experiments, comparing the Spearman's rank correlation (SRC) evaluation results of existing methods on the UNIV-Dive dataset, this framework reflects the greater accuracy advantage and further lays the foundation for the actual implementation of the technology.

Fabrication, Performance, and Potential Applications of MXene Composite Aerogels.

Aerogel, known as one of the remarkable materials in the 21st century, possesses exceptional characteristics such as high specific surface area, porosity, and elasticity, making it suitable for a diverse range of applications. In recent years, MXene-based aerogels and MXene composite aerogels as functional materials have solved some limitations of traditional aerogels, such as improving the electrical conductivity of biomass and silicon aerogels, further improving the energy storage capacity of carbon aerogels, enhancing polymer-based aerogels, etc. Consequently, extensive research efforts have been dedicated to investigating MXene-based aerogels, positioning them at the forefront of material science studies. This paper provides a comprehensive review of recent advancements in the preparation, properties, and applications of MXene-based composite aerogels. The primary construction strategies employed (including direct synthesis from MXene dispersions and incorporation of MXene within existing substrates) for fabricating MXene-based aerogels are summarized. Furthermore, the desirable properties (including their applications in electrochemistry, electromagnetic shielding, sensing, and adsorption) of MXene composite aerogels are highlighted. This paper delves into a detailed discussion on the fundamental properties of composite aerogel systems, elucidating the intricate structure-property relationships. Finally, an outlook is provided on the opportunities and challenges for the mass production and functional applications of MXene composite aerogels in the field of material engineering.

Free vibration and sound transmission properties of beetle elytron plate: structural parametric analysis.

Honeycomb plate (HP), which is a high-strength and lightweight structure, has good vibration characteristics, while beetle elytron plate (BEP) has better mechanical properties. To promote the engineering application of BEPs, the vibration and sound transmission characteristics of aluminium BEPs were investigated in this paper with HP as the comparison object. This paper investigated the effects of the number of trabeculae, the ratio of length and width, skin thickness, core height and core thickness on the first 4 frequencies using finite element method. The results show that (1) the vibration characteristic of BEP is optimal when the number of trabeculae is 6, and its 3rd and 4th modes show mixed mode, i.e., torsion-bending or bending-torsion mode. (2) The frequencies of BEPs are generally lower than those of HPs. Compared with HPs, the ratio of length and width and core thickness have a smaller influence on the mode shapes of BEPs, and the core height has a smaller influence on BEPs' frequencies. When the skin thickness is small, increasing the thickness can effectively change the natural frequencies of BEPs and HPs. (3) Considering the common frequencies of four applications (aircrafts, unmanned aerial vehicles, high-speed trains and automobiles) of sandwich plates, the effects of the abovementioned parameters including the ratio of length and width, skin thickness, core height and core thickness are analysed. (4) Combined with the theoretical calculation formula, the effect of the above structural parameters on the sound transmission characteristic is explored using the index of sound transmission loss, and targeted recommendations are given. This paper progresses the application in engineering.

TOCN/copper calcium titanate composite aerogel films as high-performance triboelectric materials for energy harvesting.

The development of high-performance cellulose-based triboelectric nanogenerators (TENG) has been a subject widely concerned by researchers. Here, we prepared a composite aerogel film based on TEMPO-oxidized cellulose nanofiber (TOCN) and copper calcium titanate (CaCu3Ti4O12, CCTO) nanoparticles. Under their comprehensive effects of the enhanced dielectric performance, the TOCN/CCTO-20 composite film with 20 % CCTO content based TENG device showed the best output performance of an open circuit voltage of 152 V, a short circuit current of 33.8 µA and a power density of 483 mW/m2, which were 3.37, 4.07 and 3.71 times higher than that of the pure TOCN based TENG device, respectively. In addition, effects of external force conditions, aerogel film size parameters and the agglomeration state of high filler content on the output performance were also studied. These results indicated that the TOCN/CCTO composite aerogel films can be used as efficient and low-cost cellulose-based triboelectric positive materials for energy harvesting.

One-pot synthesis of robust dendritic sulfur quantum dots for two-photon fluorescence imaging and "off-on" detection of hydroxyl radicals and ascorbic acid.

The straightforward preparation of fluorescent sulfur quantum dots (SQDs) with good photostability and biocompatibility and multifunction remains a challenge. Herein, a simple method to improve the performance of SQDs is reported, that is, using hyperbranched polyglycerol (HPG) as a ligand to direct the synthesis of dendritic HPG-SQD nanocomposites from cheap elemental sulfur. Thanks to the protection of HPG, the HPG-SQDs show much better biocompatibility and photostability as compared with the widely reported polyethylene glycol (PEG) ligand-capped SQDs (PEG-SQDs). In addition, the HPG-SQDs also present excellent aqueous solubility, stable fluorescence against environmental variation, good cell uptake capability, and strong single- and two-photon fluorescence. Moreover, the HPG-SQDs display sensitive and selective fluorescence "off-on" behavior to hydroxyl radicals (˙OH) and ascorbic acid (AA), respectively, and thereby hold potential as a fluorescent switch to detect ˙OH and AA. For the first time, the utilization of two-photon fluorescence of HPG-SQDs to monitor ˙OH and AA in cells is demonstrated in this study.

Corona-Poled Porous Electrospun Films of Gram-Scale Y-Doped ZnO and PVDF Composites for Piezoelectric Nanogenerators.

For digging out eco-friendly and well-performed energy harvesters, piezoelectric nanogenerators are preferred owing to their effortless assembly. Corona-poling promotes output performance of either aligned or porous PVDF electrospun films and higher piezoelectric output was achieved by corona-poled porous PVDF electrospun films due to more poled electret dipoles in pores. Increasing the duration of electrospinning rendered more electret dipoles in PVDF porous electrospun films, resulting in higher piezoelectric output. Moreover, corona-poled PVDF/Y-ZnO porous electrospun films performed better than corona-poled PVDF/ZnO porous electrospun films because of the larger polar crystal face of Y-ZnO. Flexible piezoelectric polymer PVDF and high-piezoelectric Y-ZnO complement each other in electrospun films. With 15 wt% of Y-ZnO, corona-poled PVDF/Y-ZnO porous electrospun films generated maximum power density of 3.6 µW/cm2, which is 18 times that of PVDF/BiCl3 electrospun films.

Utilization of silt, sludge, and industrial waste residues in building materials: A review.

To promote the effective utilization of sludge and slag produced in nature and from human activities, this paper summarizes the research progress in the field of building materials on the basis of expounding their classification and characteristics. (1) Sludge and slag include silt, sludge and industrial waste residues. These three materials are mainly composed of SiO2, which can be used to produce building materials after treatment and can also be used as admixtures, including roadbed admixtures. (2) Silt and sludge are widely used in building wall materials and roadbed materials, etc. Industrial waste residues can be used in the production and processing of green concrete and glass-ceramics. (3) In addition to continuing to use existing utilization methods, key treatment technologies and new treatment devices can be further developed according to the characteristics of sludge and slag. Moreover, observations and mechanistic analysis of the microscopic structure of industrial waste residues and research on strong and weak utilization methods based on the performance of building materials can be carried out, and more efficient and energy-saving excitation or activation technologies will be developed. These efforts will eventually lead to the development of functional building materials with excellent performance and environmentally friendly characteristics to achieve the differentiated utilization of silt, sludge, and industrial waste residues and realize the efficient transformation of resources. This paper provides useful insights for the application of sludge and slag in the field of building materials.

Porous cellulose composite aerogel films with super piezoelectric properties for energy harvesting.

The piezoelectric effect is one of the most promising electromechanical coupling processes for mechanical energy conversion and energy harvesting. However, natural polymer based piezoelectric materials are of poor piezoelectric performance. we developed flexible porous piezoelectric aerogel films based on TEMPO-oxidized cellulose nanofibrils (TOCN) and MoS2 nanosheets. Those aerogel films possessed large specific surface areas and abundant mesopores. Moreover, they exhibited very good piezoelectric properties when a field strength of 20 MV/m was used to polarize MoS2 nanosheets and air in the mesopores. When assembled to piezoelectric nanogenerators (PENGs), a TOCN/MoS2 aerogel film PENG containing 6 wt% of MoS2 exhibited the best output performance. It generated an open circuit voltage of 42 V and a short-circuit current of 1.1 µA, a maximum area power density of 1.29 µW/cm2 and a maximum volume power density of 0.143 µW/cm3. These features enable them to be promising piezoelectric materials for energy harvesting.

Highly Sensitive Multifunctional Electronic Skin Based on Nanocellulose/MXene Composite Films with Good Electromagnetic Shielding Biocompatible Antibacterial Properties.

Electronic skin has aroused extensive research interest due to high similarity with human skin. Realizing a multifunctional electronic skin that is highly consistent with skin functions and endowed with more other functions is now a more urgent need and important challenge. Here, we use 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) dispersion and highly conductive Ti3C2TX dispersion to prepare TOCN/Ti3C2TX composite film through vacuum-assisted filtration. The obtained composite film imitating the nacre-like lamellar structure of natural shells has good mechanical properties (124.6 MPa of tensile strength). Meanwhile, the composite film also showed excellent electromagnetic shielding performance (36 dB), biocompatibility, and antibacterial properties. In addition, the piezoresistive sensor assembled from the composite film exhibited a high sensitivity (11.6 kPa-1), fast response and recovery time (≤10 ms), ultralow monitoring limit (0.2 Pa), and long-term stability (>10 000 cycles). It also could detect human daily activities such as finger bent, chewing, and so on.

High energy, high brightness picosecond master oscillator power amplifier with output power 65.5 W.

In this article, it is demonstrated the generation of high pulse energy, high beam quality and high brightness mode-locked picosecond pulses from a compact Nd:YVO4 master oscillator power amplifier system. This system mainly consisted of a SESAM mode-locked picosecond seed generator and four-stage multi-pass amplifiers. A pulse picker was adopted prior to power amplifiers to efficiently reduce the pulse repetition rate. The maximum average output power of 65.5 W was obtained with a repetition rate of 496.85 kHz and a pulse duration of 16.9 ps, corresponding to a maximum pulse energy of 131.83 µJ and a peak power of 7.8 MW. While simultaneously, the output beam quality factors along the x axis and the y axis were measured to be Mx 2=1.36 and My 2=1.32, respectively, therefore, a brightness as high as 3.22 × 109 W·cm-2·Sr was achieved. As far as we all know, this is the highest brightness for a picosecond pulsed Nd:YVO4 MOPA laser at 1064 nm.

Facile synthesis of polyamidoamine dendrimer gel with multiple amine groups as a super adsorbent for highly efficient and selective removal of anionic dyes.

Preparation of excellent dye adsorbent that simultaneously displays convenient separation capability, high adsorption capacity, fast removal rate, superior adsorption selectivity, and favorable reusability remains a challenge. Herein, we present a simple and feasible one-step method to prepare amine-rich porous polyamidoamine (PAMAM) dendrimer gel adsorbent. The PAMAM gel could be readily separated from water by filtration. The adsorption properties of PAMAM gel was systematically examined by adsorption of anionic methyl orange (MO) and tartrazine (TTZ) dyes. The PAMAM gel exhibited superior adsorption selectivity and removal efficiency towards anionic MO and TTZ dyes. The adsorption process could be completed within around 15 min and presented fine correlation with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacity of PAMAM gel towards MO and TTZ was as high as 680.2 mg g-1 and 689.7 mg g-1, respectively. Additionally, the dye-adsorbed PAMAM gel could be readily desorbed in alkaline solution. Considering the simple synthetic process and outstanding adsorption performance of PAMAM gel, this paper provides an effective approach to prepare high-performance anionic dye adsorbents.

Oxygen accelerated scalable synthesis of highly fluorescent sulfur quantum dots.

Here, we report a facile and efficient approach for the large-scale synthesis of highly fluorescent sulfur quantum dots (SQDs) from inexpensive elemental sulfur under a pure oxygen (O2) atmosphere. The important finding of this work is that the polysulfide (S x 2-) ions could be oxidized to zero-valent sulfur (S[0]) by O2, which is the accelerator of the reaction. The SQDs prepared by this method possess nearly monodisperse size (1.5-4 nm), high fluorescence quantum yield (21.5%), tunable emission, and stable fluorescence against pH change, ionic strength variation and long-term storage. Moreover, the reaction yield of SQDs reached as high as 5.08% based on the content of S element in SQDs, which is much higher than other reported approaches (generally <1%). The prepared SQDs could be easily processed for widespread applications thanks to their low toxicity and superior dispersibility both in water and common organic solvents. These high-quality SQDs may find applications similar to or beyond those of carbon QDs and silicon QDs.

Superior amine-rich gel adsorbent from peach gum polysaccharide for highly efficient removal of anionic dyes.

Herein, we demonstrated the potential of peach gum polysaccharide-based amine-rich gel (ARG) as an efficient adsorbent for removal of anionic dyes from water. The adsorption performance of ARG was systematically studied by choosing methyl orange (MO) and amaranth (ART) as representative anionic dyes. The effects of various parameters such as pH, ionic strength, temperature, initial dye concentration and contact time on the adsorption were investigated. The ARG exhibited superior adsorption selectivity and stable adsorption behaviors against variation of pH and ionic strength for anionic dyes. Adsorption process reached equilibrium within 10 min and showed good correlation with pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacity of ARG for MO and ART can reach 1949.5 and 1082.2 mg g-1, respectively. Based on its sustainable characteristic, low cost and excellent adsorption property, the ARG holds great promise for utilizing as an adsorbent for practical water treatment applications.

Multi-carboxylic magnetic gel from hyperbranched polyglycerol formed by thiol-ene photopolymerization for efficient and selective adsorption of methylene blue and methyl violet dyes.

Synthesis of adsorbents that simultaneously possess high adsorption performance and convenient separation characteristic remains a big challenge. Herein, we report a viable strategy to prepare hyperbranched polyglycerol (HPG)-based multi-carboxylic magnetic gel (MMG) based on the thiol-ene click chemistry. The obtained HPG-based MMG adsorbent with porous structure and multiple carboxylic groups not only exhibited fast adsorption rate, superior adsorption capacity, and favorable adsorption selectivity towards cationic dyes (e.g., methylene blue (MB) and methyl violet (MV)) but also presented convenient magnetic separation characteristic. The adsorption data showed nice correlation with pseudo-second-order kinetic model and Langmuir isotherm. The optimal adsorption capacity of HPG-based MMG for MB and MV can reach as high as 458.7 and 400.0 mg g-1, respectively. Moreover, the dye-adsorbed HPG-based MMG could be regenerated in ethanol for reuse without obvious decline of removal efficiency. On the basis of the superior adsorption property of HPG-based MMG, this work offers an effective strategy to prepare advanced adsorbent for dye removal from wastewater.

Versatile magnetic gel from peach gum polysaccharide for efficient adsorption of Pb2+ and Cd2+ ions and catalysis.

In this paper, we report a facile approach to prepare magnetic gel based on the simultaneous formation of Fe3O4 nanoparticles and crosslinking of natural peach gum polysaccharide. The obtained magnetic gel with porous structure, high specific surface area and numerous oxygen-containing functional groups exhibited fast and efficient adsorption capability towards Pb2+ and Cd2+ ions. The adsorption isotherms and kinetics presented good correlation with Langmuir isotherm and pseudo-second-order model, respectively. The maximum adsorption capacity of the magnetic gel for Pb2+ and Cd2+ ions can reach 277.0 and 141.4mgg-1, respectively, which is much higher than many other reported magnetic adsorbents. In addition, the magnetic gel can serve as a magnetic support for in situ growth of Pt nanocatalyst with high catalytic activity, as demonstrated by the reduction of 4-nitrophenol. Moreover, the magnetic gel exhibited excellent magnetic separation capability and superior reusability both for the adsorption and catalysis applications.

Facile Functionalization of Natural Peach Gum Polysaccharide with Multiple Amine Groups for Highly Efficient Removal of Toxic Hexavalent Chromium (Cr(VI)) Ions from Water.

The development of low-cost adsorbent with excellent adsorption property remains a big challenge. Herein, the functionalization of natural peach gum polysaccharide (PGP) with multiple amine groups for the removal of toxic Cr(VI) ions from water was studied. The obtained PGP-NH2 gel exhibited high-removal efficiency (>99.5%) toward Cr(VI) ions, especially with relatively low initial concentration of Cr(VI) ions (≤250 mg/L). The influences of pH, ionic strength, contact time, initial concentration, and temperature on the adsorption of Cr(VI) ions were systematically investigated. The PGP-NH2 gel showed rapid adsorption rate and could reach adsorption equilibrium within about 40 min. The Cr(VI) ion uptake process could be described by pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of PGP-NH2 gel could reach 188.32 mg/g. Thermodynamic investigation results indicated the spontaneous and exothermic characteristic of the uptake process. Moreover, the PGP-NH2 gel also exhibited favorable reusability, and 135.52 mg/g of adsorption capacity was retained even after being reused for five times. Considering its low cost and superior uptake property, the PGP-NH2 gel holds a great promise for employing as an adsorbent to treat Cr(VI) ion-containing wastewater.