Polyphenylene sulfide (PPS) is a high-performance semi-crystalline thermoplastic polymer that is widely used in the automotive, electronics, and aerospace industries, as well as other fields. ...However, PPS introduces several challenges in fused deposition modeling owing to its inherent properties of crystallization and thermal crosslinking. The present study demonstrates the effects of the thermal processing and heat treatment conditions on the accuracy and mechanical properties of PPS samples three-dimensionally printed through fused deposition modeling. By measuring the degree of crystallinity and thermal crosslinking of three-dimensionally printed PPS samples, we found that the thermal history affects the three-dimensionally printed PPS properties. Results show that the accuracy of three-dimensionally printed PPS samples can be improved by means of air-forced cooling in fused deposition modeling. The balance between mechanical strength and ductility was regulated by altering the heat treatment conditions. This approach is applicable to eliminating the warpage of semi-crystalline polymer in three-dimensional printing (not only for PPS) and provides a method of improving the mechanical properties of three-dimensionally printed PPS samples.
Biodegradable stents offer the potential to reduce the in-stent restenosis by providing support long enough for the vessel to heal. The polylactic acid (PLA) vascular stents with negative Poisson's ...ratio (NPR) structure were manufactured by fused deposition modeling (FDM) 3D printing in this study. The effects of stent diameter, wall thickness and geometric parameters of arrowhead NPR structure on radial compressive property of 3D-printed PLA vascular stent were studied. The results showed that the decrease of stent diameter, the increase of wall thickness and the increase of the surface coverage could enhance the radial force (per unit length) of PLA stent. The radial and longitudinal size of PLA stent with NPR structure decreased simultaneously when the stent was crimped under deformation temperature. The PLA stent could expand in both radial and longitudinal direction under recovery temperature. When the deformation temperature and recovery temperature were both 65 °C, the diameter recovery ratio of stent was more than 95% and the maximum could reach 98%. The length recovery ratio was above 97%. This indicated the feasibility of utilizing the shape memory effect (SME) of PLA to realize the expansion of 3D-printed PLA vascular stent under temperature excitation.
Accumulating evidence has indicated that Complement factor H-related 3 (CFHR3) plays an essential role in various diseases. However, the biological functions of CFHR3 in hepatocellular carcinoma ...(HCC) remain largely unclear. Therefore, we perform a further study on CFHR3 in HCC. In this article, we report the suppressive role of CFHR3 in the proliferation and metastasis of HCC cells. CFHR3 downregulation is closely associated with large (T3-T4) HCC, tumor recurrence, and advanced (stage III-IV) clinical stage, functioning as an independent factor for the prognoses of HCC patients. Knockdown of CFHR3 promotes proliferation, migration, and invasion of HCC cells. Mechanistically, downregulation of CFHR3 is induced by miR-590-3p binding to the 3’ untranslated region (UTR) of CFHR3. CFHR3 downregulation promotes the phosphorylation of STAT3 protein, thereby suppressing p53 expression. The promotional effect upon downregulation of CFHR3 induced by CFHR3 stable knockdown or miR-590-3p on HCC cell malignant phenotypes is attenuated by STAT3 inhibitor, S3I-201. In conclusion, our results reveal that CFHR3 is a protective biomarker for HCC patients, and targeting the miR-590-3p/CFHR3/p-STAT3/p53 signaling axis provides a promising strategy for HCC therapeutics.
In addition to the social economy and the rapid development of industry and agriculture, water demand is increasing and poses challenges in the over-exploitation of water resources. This research ...establishes a model to assess the sustainable exploitation of water resources based on system dynamics theory and STELLA software, which solves the imbalanced allocation of industrial water, agricultural water and domestic water. The model is composed of two parts: the water quantity system (including economy, population, water availability and water demand) and the water quality system (composed of the aquatic environment), which is suitable for Chengde City with a water resource shortage. The proposed model is established by data of Chengde City from 2007 to 2016 and is verified by 2017 data. Furthermore, in order to compare the water quality and water utilization of Chengde City under different development scenarios up to 2025, the sensitivity analysis of each variable (e.g., population) is carried out in this model, and thereby the water resource utilization scenarios are acquired. Specifically, four scenarios are designed and denoted: Scenario 1: keeping the status quo unchanged, Scenario 2: slowing down economic development and devoting more energy to environmental protection, Scenario 3: only focusing more on economic development and Scenario 4: aiming at steady and rapid economic growth and an eco-friendly environment. The results shows that Scenarios 2 and 3 facilitate high-effective water resource utilization compared with the current development, Scenario 1. Scenario 4 fosters the balance of water resources supply–demand in the future and preserves the water quality. This study provides an inspiring method for realizing the sustainable utilization and optimizing allocation of water resources in Chengde City.
Low-cost metal additive manufacturing remains difficult but would be of great practical value. To prepare slurry distributed evenly and stably, the present study thoroughly mixed metal powder, as a ...base material, with corresponding monomers, crosslinking agents, dispersant, initiator, and catalysts. A complex three-dimensional structure of iron powder slurry was built using a pneumatic injection additive manufacturing system. The effects of the injection pressure, platform speed, and nozzle diameter on the width of printed lines were studied. The stability of the width of a single printed line was investigated. It was found that the line width increases with an increase in the injection pressure or nozzle diameter and decreases with an increase in the moving speed of the platform. A reasonable drying, debinding, and sintering schedule was established, and the microstructures of dried, debinding, and sintered parts were analyzed. The sintered parts were denser than dried and debinding parts. The pneumatic injection additive manufacturing technology adopted in this study has the advantages of low manufacturing costs and a wide range of printing materials, and is applicable in the additive manufacturing of iron powder and a variety of other metal powders, thus widening the range of materials used in additive manufacturing.
Fe-based metallic glasses are amorphous alloys with high strength, high hardness, and excellent corrosion resistance; however, the immaturity of processing methods has prevented their wide ...application in industrial production. Fe-based metallic glass parts were manufactured employing pneumatic injection additive manufacturing in this study. An evenly dispersed and stable Fe-based metallic glass powder slurry with a solids content of 50% was prepared firstly. Then the Fe-based metallic glass parts were printed. The printed parts were dried, debinded, and sintered for strengthening. The deformations of the printed parts and sintered parts relative to the original model were then analyzed by a 3D scanning reconstruction method. The slightly average bulging and sunken deformation of the printed parts and sintered parts confirmed the good printing accuracy of the pneumatic injection manufacture system. The effects of the sintering temperature and holding time on the properties of the sintered parts were studied. For a sintering temperature of 580 °C and holding time of 1 h, the surface quality of the sintered parts was better. The sintering of 3D-printed Fe-based metallic glass parts was preliminarily realized in this study, and the feasibility of preparing Fe-based metallic glass using pneumatic injection additive manufacture was verified.
In recent years, pedestrian detection has become one of the core issues in self-driving car and automatic alert in video surveillance. However, the efficiency and accuracy are not ideal in ...multi-pedestrian scenarios because of the occlusion by other pedestrian or non-human objects. Here, the authors design a pedestrian-detection framework based on region proposal network and convolutional neural network. Magnetic region regression strategy was proposed to reduce locating errors and false detection in the process of region regression. Meanwhile, semantic segmentation is integrated into authors’ framework to improve the accuracy of classification. Additionally, the authors used soft- non-maximum suppression (NMS) to reduce the impact of NMS threshold on the model. Authors’ framework has average miss rate of 6.94% on Improved Caltech-USA dataset. The experiments show that authors’ framework achieves significant advantages.
Thermal images could help visual images to improve object detection performance under low illumination. On the other hand, the complementary fusion of visual and thermal features can be challenging. ...In RGB-T object detection, the two-stream network structure has been widely used, in which addition operation and concatenation operation are utilized to merge feature maps. However, the addition compacts two-stream feature with inevitable distortion, while direct concatenation may bring redundancy to features. In this paper, we show that the addition operation is more suitable for common features from RGB and thermal, while the concatenation operation is more suitable for specific features unique to RGB or thermal. Then we take the divide-and-conquer strategy to propose an RGB-T detector named Divide-and-Conquer Fusion Network (DaCFN), which divides RGB and thermal features into common and specific ones and applies category-customized operations to them. Specifically, we design the Partial Coupling Net Block (PCNB), in which common features are extracted by coupled parameters and specific features by independent ones. Then the Selective Common Addition (SCA) and the Independent Specific Concatenation (ISC) are designed to fuse common and specific features, respectively. Experiments on FLIR and KAIST datasets demonstrate that our approach achieves high accuracy with high speed against other state-of-the-art RGB-T detectors.
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