In traditional aqueous slurry freezing casting processing, the growth method of ice crystals is hard to control, resulting in the uncontrollable pore's morphologies of the porous ceramics. In the ...experimental, the pure Al
2O
3 sol was used to substitute water as a medium for preparing ceramic slurry. With Al
2O
3 sol addition, it becomes easy to control the microstructure and pore's morphologies of the porous Al
2O
3 ceramics via adjusting of the solid loading, composition of the ceramic slurries, as well as the cooling methods. The SEM micrographs showed that the sol-contained ceramic slurry combined with freeze casting processing can easily prepare the porous Al
2O
3 ceramics with different pore sizes and different morphologies. The porous Al
2O
3 ceramics prepared from 70
wt.% to 90
wt.% solid loading sol-contained Al
2O
3 slurries and sintered at 1500
°C for 2
h have open porosities from 81.7% to 64.6%.
Typical visual simultaneous localization and mapping (SLAM) systems rely on front-end odometry for feature extraction and matching to establish the relations between adjacent images. In a low-light ...environment, the image obtained by a camera is dim and shows scarce information, hindering the extraction of sufficient stable feature points, consequently undermining visual SLAM. Most existing methods focus on low-light enhancement of a single image, neglecting the strong temporal correlation across images in visual SLAM. We propose a method that leverages the temporal information of an input image sequence to enhance the low-light image and employed the enhanced result to improve the feature extraction and matching quality of visual SLAM. Our method trains a three-dimensional convolutional neural network to estimate pixelwise grayscale transformation curves to obtain a low-light enhancement image. Then, the grayscale transformation curves are iteratively applied to obtain the final enhanced result. The training process of the network does not require any paired reference images. We also introduced a spatial consistency loss for the enhanced image to retain the content and texture of the original image. We further integrated our method into VINS-Mono and compared with similar low-light image enhancement methods on the TUM-VI public dataset. The proposed method provides a lower positioning error. The positioning root-mean-squared error of our method is 19.83% lower than that of Zero-DCE++ in low-light environments. Moreover, the proposed network achieves real-time operation, being suitable for integration into a SLAM system.
A new algorithm, Yolov8n-FADS, has been proposed with the aim of improving the accuracy of miners’ helmet detection algorithms in complex underground environments. By replacing the head part with ...Attentional Sequence Fusion (ASF) and introducing the P2 detection layer, the ASF-P2 structure is able to comprehensively extract the global and local feature information of the image, and the improvement in the backbone part is able to capture the spatially sparsely distributed features more efficiently, which improves the model’s ability to perceive complex patterns. The improved detection head, SEAMHead by the SEAM module, can handle occlusion more effectively. The Focal Loss module can improve the model’s ability to detect rare target categories by adjusting the weights of positive and negative samples. This study shows that compared with the original model, the improved model has 29% memory compression, a 36.7% reduction in the amount of parameters, and a 4.9% improvement in the detection accuracy, which can effectively improve the detection accuracy of underground helmet wearers, reduce the workload of underground video surveillance personnel, and improve the monitoring efficiency.
Microwave technology was applied in two combined freezing-based processes to desalinate raw seawater. The two processes employed freezing, microwaving and centrifugal desalination (FMCD) process and ...freezing, microwaving, gravity-induced and centrifugal desalination (FMGCD) process respectively. The removal efficiencies of salt, TDS (total dissolved solids), Cl−, Ca2+ and Mg2+, the ice yield rate as well as the duration time of the two desalination processes were studied. The results were compared with that of our previous study using combined freezing, gravity-induced and centrifugal desalination (FGCD) process. The study showed that microwave treatment can greatly accelerate the desalination in the two combined processes. By applying a two-minute microwave treatment, the desalination effect of FMGCD process is similar to or better than that of FGCD process. Taking TDS and Cl− concentration as reference indicators, the ice product quality of FMGCD process can meet the drinking water standard requirement when the brine reject proportion is >54%.
•Two combined freezing-based desalination processes with microwave treatment i.e. freezing, microwaving and centrifugal desalination (FMCD) process and freezing, microwaving, gravity-induced and centrifugal desalination (FMGCD) process were studied.•Comparing with another combined freezing, gravity-induced and centrifugal desalination (FGCD) process, the application of microwave treatment accelerates greatly both FMCD and FMGCD desalination processes.•For FMGCD process, taking TDS and Cl- concentration as reference indicators, the ice product quality meets the requirement of some China’s water quality standards depending on the brine reject proportion Pbr. When Pbr is ≥ 54%, the ice product quality can meet the requirements of drinking water and surface water standards.
A strategy to fabricate a stable and site-isolated Ni catalyst is reported. Specifically, Mo3S4 clusters allowed individual Ni atoms to bond with Mo and S to create a type of active site. A ...site-isolated Ni1MoS/Al2O3 sample exhibited high performance in the selective hydrogenation of acetylene. Concretely, 90% ethylene selectivity was achievable at full acetylene conversion under relatively mild reaction conditions without any obvious decay in performance observed during longer testing periods. In contrast, a reference catalyst with Ni ensembles exhibited poor selectivity and stability. Density functional theory (DFT) calculations suggested that H2 molecules were activated by a heterolytic route over Ni1MoS/Al2O3, which enhanced the reaction rate. Improved selectivity originated from the unique isolated Niδ+ structure induced by Mo and S, which facilitated product desorption as opposed to overhydrogenation or oligomerization. This work provides a feasible way to construct site-isolated catalysts with higher active metal loadings and opens up an opportunity for selective hydrogenation.
A combined freezing, soaking, and centrifugal desalination (FSCD) process was employed to desalt seawater taken from Bohai Bay. The seawater was frozen into two kinds of sea water ice having ...different texture and size using either commercial refrigerator or experimental setup. For both kinds of ice samples, the influences of soaking-related parameters on the desalination effect were studied. For most ice samples treated with FSCD process, the salt removal efficiencies are higher than 90%. The purity of ice product increases as increasing soaking time and at higher initial soaking liquid temperature, while the ice yield rate decreases. At the same ice yield rate, the salt removal efficiency for ice flakes is higher than that for crushed ice samples, whereas when the raw seawater of 27 °C is used as soaking liquid, FSCD process is not feasible due to too lower ice yield rate.
A capacitive humidity sensor based on graphene oxide/cellulose nanofibers (GO/CNF) is proposed in this work. The sensing characteristics of the humidity sensor at different relative humidities (RH) ...are investigated. The results demonstrate that the GO/CNF-based sensor has a high humidity sensitivity (1146.8 pF /% RH), which is nearly 19 times higher than the pure CNF sensor and almost 2.6 times greater than the pure GO sensor. This is due to the fact that the incorporation of CNF into the GO/CNF film introduces additional hydrophilic functional groups and causes an increase in film roughness and wrinkling. This increases the number of water molecule adsorption sites on the GO/CNF composite film on the one hand, and expands the contact area of the GO/CNF composite film with water molecules on the other hand, resulting in a GO/CNF-based humidity sensor with high response sensitivity. Moreover, the sensor shows rapid response and recovery rates, as well as low hysteresis characteristics. Therefore, this research suggests that GO/CNF hybrid films possess considerable potential for the production of high-performance humidity sensors.
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•The introduction of cellulose nanofibers greatly improved the humidity response sensitivity of GO/CNF composites.•A highly responsive capacitive humidity sensor is proposed.•The mechanism of humidity sensing in CNF/GO-based capacitive humidity sensors is discussed in detail.
Abstract
In our previous study, it was noticed that the combined freezing, soaking and centrifugal desalination (FSCD) process is unsuitable to be applied in summer, because very little pure ice can ...be produced when the temperature of raw seawater used as soaking liquid reaches 27 °C. Therefore, two main efforts on the process optimization were made in this paper. One is that low-temperature seawater served as soaking liquid in all the experiments. In real industrial practice, the low-temperature soaking liquid can be obtained through melting pure ice products or recovering cold energy from cold concentrated brine. The effects of centrifugal parameters and soaking time on salt removal efficiency and ice yield rate were investigated. Second, the gravity-induced method was combined to form freezing, soaking, gravity-induced and centrifugal desalination (FSGCD) processes for further improvement of the salt removal efficiency. The influence of melting time of gravity-induced process was studied by keeping the samples ambient with an air temperature of 30 °C. Finally, the performance among different processes was compared. Results showed that the salt removal efficiency of the FSGCD process can reach up to 97.03%. The study is helpful to improve the process performance of soaking treatment in summer application.
A guided bone regeneration (GBR) membrane can act as a barrier to prevent the invasion and interference from foreign soft tissues, promoting infiltration and proliferation of osteoblasts in the bone ...defect area. Herein, a composite scaffold with dual functions of osteogenesis and antibacterial effects was prepared for GBR. A polycaprolactone (PCL)/nano-hydroxyapatite (n-HA) aerogel produced by electrospinning and freeze-drying techniques was fabricated as the loose layer of the scaffold, while a PCL nanofiber membrane was used as the dense layer. Chitosan (CS) solution served as a middle layer to provide mechanical support and antibacterial effects between the two layers. Morphological results showed that the loose layer had a porous structure with n-HA successfully dispersed in the aerogels, while the dense layer possessed a sufficiently dense structure.
antibacterial experiments illustrated that the CS solution in the middle layer stabilized the scaffold structure and endowed the scaffold with good antibacterial properties. The cytocompatibility results indicated that both fibroblasts and osteoblasts exhibited superior cell activity on the dense and loose layers, respectively. In particular, the dense layer made of nanofibers could work as a barrier layer to inhibit the infiltration of fibroblasts into the loose layer.
osteogenesis analysis suggested that the PCL/n-HA aerogel could enhance the bone induction ability of bone mesenchymal stem cells, which was confirmed by the increased expression of the alkaline phosphatase activity. The loose structure facilitated the infiltration and migration of bone mesenchymal stem cells for better osteogenesis. In summary, such a composite scaffold exhibited excellent osteogenic and antibacterial properties as well as the barrier effect, thus holding promising potential for use as GBR materials.
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