Search

3D printing technology is one of the additive manufacturing technologies for rapid process and manufacture of complex geometric components. Based on the three-dimensional data model, the material is accumulated layer by layer controlled by computer, and eventually forms the solid object. Compared to the traditional manufacturing methods, 3D printing technology has many advantages, such as time saving, low cost, easy operation, no mold and strong controllability of component geometry, etc. Along with the development of this technology, several types of 3D printing technologies, such as fused deposition modeling, selective laser sintering, stereo lithography, digital light processing and solvent casting molding, have been produced according to the core of the printing technology, applicable materials and equipment composition. The principles and characteristics of the four most representative 3D printing forming processes were introduced in this paper, and the research progress of carbon nanotubes to reinforce polymer composites with different types of 3D printing forming processes applied in recent years was summarized. At the same time, it was predicted that the 3D printing molding technology will be developed towards the direction of high precision, industrialization, popularization and high integration in this field, and the research and development of 3D printing materials will also have more prospects.

To investigate the clinical characteristics and prognosis of pneumococcal meningitis (PM), and drug sensitivity of Streptococcus pneumoniae (SP) isolates in Chinese children. Methods A retrospective analysis was conducted on clinical information, laboratory data, and microbiological data of 160 hospitalized children under 15 years old with PM from January 2019 to December 2020 in 33 tertiary hospitals across the country. Results Among the 160 children with PM, there were 103 males and 57 females. The age ranged from 15 days to 15 years, with 109 cases (68.1%) aged 3 months to under 3 years. SP strains were isolated from 95 cases (59.4%) in cerebrospinal fluid cultures and from 57 cases (35.6%) in blood cultures. The positive rates of SP detection by cerebrospinal fluid metagenomic nextgeneration sequencing and cerebrospinal fluid SP antigen testing were 40% (35/87) and 27% (21/78), respectively. Fiftyfive cases (34.4%) had one or more risk factors for purulent meningitis, 113 cases (70.6%) had one or more extra-cranial infectious foci, and 18 cases (11.3%) had underlying diseases. The most common clinical symptoms were fever (147 cases, 91.9%), followed by lethargy (98 cases, 61.3%) and vomiting (61 cases, 38.1%). Sixty-nine cases (43.1%) experienced intracranial complications during hospitalization, with subdural effusion and/or empyema being the most common complication [43 cases (26.9%)], followed by hydrocephalus in 24 cases (15.0%), brain abscess in 23 cases (14.4%), and cerebral hemorrhage in 8 cases (5.0%). Subdural effusion and/or empyema and hydrocephalus mainly occurred in children under 1 year old, with rates of 91% (39/43) and 83% (20/24), respectively. SP strains exhibited complete sensitivity to vancomycin (100%, 75/75), linezolid (100%, 56/56), and meropenem (100%, 6/6). High sensitivity rates were also observed for levofloxacin (81%, 22/27), moxifloxacin (82%, 14/17), rifampicin (96%, 25/26), and chloramphenicol (91%, 21/23). However, low sensitivity rates were found for penicillin (16%, 11/68) and clindamycin (6%, 1/17), and SP strains were completely resistant to erythromycin (100%, 31/31). The rates of discharge with cure and improvement were 22.5% (36/160) and 66.2% (106/160), respectively, while 18 cases (11.3%) had adverse outcomes. Conclusions Pediatric PM is more common in children aged 3 months to under 3 years. Intracranial complications are more frequently observed in children under 1 year old. Fever is the most common clinical manifestation of PM, and subdural effusion/emphysema and hydrocephalus are the most frequent complications. Nonculture detection methods for cerebrospinal fluid can improve pathogen detection rates. Adverse outcomes can be noted in more than 10% of PM cases. SP strains are high sensitivity to vancomycin, linezolid, meropenem, levofloxacin, moxifloxacin, rifampicin, and chloramphenicol. [ABSTRACT FROM AUTHOR]

The sizing treatments were used to introduce carbon nanotubes (CNTs) to carbon fiber (CF) surfaces for fabrication of CF/CNTs/epoxy multi-scale composites. Comparing with the base composites without CNTs, interlaminar shear strength (ILSS) and flexural strength of the modified composites were increased by 13.54% and 12.88%, respectively. Force modulation atomic force microscope and linear scanning system of scanning electron microscope were carried out to analyze the microstructure of composite interface. The results indicate that a transition layer reinforced by CNTs is constructed between fiber and epoxy (EP) matrix, which has certain thickness and exhibits gradient distribution of modulus and carbon element content. The composites containing CNTs are sonicated before curing to disperse CNTs in the surrounding resin. As a result, the interface transition layer is weakened and the ILSS and flexural strength of prepared composites decrease by 7.33% and 5.34%, respectively. Therefore, the significant role of the interface transition layer in improving the interfacial performance of composites is evidenced again at another perspective.

A solid surface frequency modulated continuous wave (FMCW) radar signal model was built to solve the range ambiguity problem of wideband and low signal-to-noise ratio (SNR) FMCW signal under severe measurement conditions. Based on prior information, a distanee inversion method was proposed, which contained signal pretreatment, band intercepting, and energy weighting. Actual data processing results show that the SNR of the frequency spectrum rises from-5.55 to 8.32 dB after pretreatment. The index of similarity of the stock level shape increases from 0.46 to 0.71 and 0.79 by band envelope interception and least squares interception, respectively.