Coaxial electrospinning preparation and antibacterial property of polylactic acid/tea polyphenol nanofiber membrane

The polylactic acid (PLA)/tea polyphenol (TP) nanofiber membranes were prepared by coaxial electrospinning. The physical properties, antibacterial agent release, degradation, and antibacterial properties were investigated. Results demonstrated that stepwise and controlled antibacterial agent release profiles were achieved based on the core-shell configuration and disparate degradation rate of PLA and TP. The mechanical performance decreased with the increase of the TP content in the shell layer. The cumulative antibacterial agent release rate of nanofiber membranes with different TP content was different, while the antibacterial agent release trend was the same. The antibacterial agent release rate of the sample was the fastest at the initial stage from 2 h to 8 h, and then gradually slowed down after 24 h. In addition, the antibacterial activity of the PLA/TP nanofiber membranes was confirmed by the inhibition zone method against both Gram-positive ( Staphylococcus aureus) and Gram-negative ( Escherichia coli). Results showed that the antibacterial performance of PLA/TP nanofiber was intensified with the increasing content of TP, especially had better antibacterial performance against S. aureus.

Integrated modelling method of bonding strength and residual life prediction for selective repair structure of aluminium alloy

To accurately describe and predict the overall strength and residual life of selective repair bonded structures, an integrated simulation model of crack propagation including bonding strength is established. Based on two methods, an integrated simulation model including a cohesive zone method model for predicting the residual life of a selective repair structure is established. By comparing the computational efficiency and accuracy of both the stress intensity factor and residual life of selective repair structures using different calculation methods, the modelling scheme is optimised. Based on this optimised scheme, the effect of adhesive thickness on the stress intensity factor and residual life of the repair structure is analysed. FM94 adhesive measuring 0.2–0.4 mm thickness is used to decrease the stress intensity factor and improve the remaining life such that material utilisation efficiency is guaranteed.

On the efficiency of coupled discrete-continuum modelling analyses of cemented materials

Computational load of discrete element modelling (DEM) simulations is known to increase with the number of particles. To improve the computational efficiency hybrid methods using continuous elements in the far-field, have been developed to decrease the number of discrete particles required for the model. In the present work, the performance of using such coupling methods is investigated. In particular, the coupled wall method, known as the “wall-zone” method when coupling DEM and the continuum Finite Differences Method (FDM) using the Itasca commercial codes PFC and FLAC respectively, is here analysed. To determine the accuracy and the efficiency of such a coupling approach, 3-point bending tests of cemented materials are simulated numerically. To validate the coupling accuracy first the elastic response of the beam is considered. The advantage of employing such a coupling method is then investigated by loading the beam until failure. Finally, comparing the results between DEM, DEM-FDM coupled and FDM models, the advantages and disadvantages of each method are outlined.

Research on Micro/Nano Surface Flatness Evaluation Method Based on Improved Particle Swarm Optimization Algorithm

Flatness error is an important factor for effective evaluation of surface quality. The existing flatness error evaluation methods mainly evaluate the flatness error of a small number of data points on the micro scale surface measured by CMM, which cannot complete the flatness error evaluation of three-dimensional point cloud data on the micro/nano surface. To meet the needs of nano scale micro/nano surface flatness error evaluation, a minimum zone method on the basis of improved particle swarm optimization (PSO) algorithm is proposed. This method combines the principle of minimum zone method and hierarchical clustering method, improves the standard PSO algorithm, and can evaluate the flatness error of nano scale micro/nano surface image data point cloud scanned by atomic force microscope. The influence of the area size of micro/nano surface topography data on the flatness error evaluation results is analyzed. The flatness evaluation results and measurement uncertainty of minimum region method, standard least squares method, and standard PSO algorithm on the basis of the improved PSO algorithm are compared. Experiments show that the algorithm can stably evaluate the flatness error of micro/nano surface topography point cloud data, and the evaluation result of flatness error is more reliable and accurate than standard least squares method and standard PSO algorithm.

Sheet Bulk Forming of Thin-Walled Components with External Gearing through Upsetting Using Controllable Deformation Zone Method

Sheet-bulk metal forming (SBMF) is a promising process for manufacturing complex sheet components with functional elements. In this study, the entire forming process for a typical thin-walled component with external gearing is investigated, including sheet forming and bulk forming processes. Deep drawn cups are prepared during sheet forming; subsequently, upsetting is performed on the sidewall to form external gearing. The upsetting method performed is known as upsetting with a controllable deformation zone (U-CDZ). Compared with the conventional upsetting method, a floating counter punch with a counter force is used in the U-CDZ method such that the forming mechanism is changed into the accumulation of the deformation zone instead of deformation throughout the entire sidewall. The effects of the counter force and material flow are investigated to understand the mechanism. The forming quality, i.e., the formfilling and effective strain distribution, improved, whereas a high forming load is avoided. In addition, a punch with a lock bead is used to prevent folding at the inner corner during the experiment.

Growth and Optical Properties of the Whole System of Li(Mn1-x,Nix)PO4 (0 ≤ x ≤ 0.5) Single Crystals

A series of single crystals of Li(Mn1-x,Nix)PO4 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.10, 0.15, 0.20, and 0.50) have been grown to large sizes up to 5 mm in diameter and 120 mm in length using the floating zone method for the first time. The comprehensive characterizations of the as-grown crystals were performed before further physical property measurements. The composition of the grown crystals was determined by energy-dispersive X-ray spectroscopy. The crystal structures were characterized by the X-ray powder diffraction method with a GSAS fitting for structural refinement, which reveals a high phase purity of the as-obtained crystals. The polarized microscopic images and Laue patterns prove the excellent quality of the single crystals. Oriented cuboids with sizes of 2.7 × 3.8 × 2.1 mm3 along the a, b, and c crystalline directions were cut and polished for further anisotropic magnetic and transparent measurements. We also first proposed a new potential application in the non-linear optical (NLO) and laser generation application for LiMPO4 (M = transition metal) materials. The optical and laser properties, such as the absorption spectra and the second harmonic generation (SHG), have been investigated and have furthermore confirmed the good quality of the as-grown single crystals.

Diversity and abundance of arbuscular fungi mycorrhizal (AMF) in rhizosphere Zea mays in tidal swamp

Sefrila M, Ghulamahdi M, Purwono Melati M, Mansur I. 2021. Diversity and abundance of arbuscular fungi mycorrhizal (AMF) in rhizosphere Zea mays in tidal swamp. Biodiversitas 22: 5071-5076. This study aims to find out the diversity and dominance of AMF spores and look at the morphology of fungi mycorrhizal arbuscular fungi that exist in the rooting area of corn (Zea mays L.) crops in the tidal swamp. The study was conducted in September 2020. Soil sampling at the tidal swamp village of Mulyasari Tanjung Lago District, Banyuasin, South Sumatra, Indonesia randomly sampling the corn root zone method. The research stages are soil sampling, soil chemistry analysis, AMF isolation and trapping, and morphological identification of AMF spores. The results showed the number of spores found in soil samples in the corn crop rhizosphere before trapping was less when compared to after trapping. The spores' shape is round, oblong, and oval, with colors ranging from clear, yellow, to brown. AMF spores found come from 2 genera namely (Acaulospora scrobiculata, A. bireticulata, A. mellea, A. laevis) and Glomus (Glomus monosporum, G. constrictum, G. manihotis).

Effects of Intensity Modulated Total-Body Circuit Training Combined with Soccer Training on Physical Fitness in Prepubertal Boys After a 6-Month Intervention

The purpose of this study was to examine the effects of a 6-month high- or moderate-intensity total-body circuit training (CT) program on physical fitness in prepubertal soccer players. Sixty-seven prepubertal boys with a mean age of 11.2 ± 0.7 years completed the study. Participants from a soccer academy were randomly assigned either to a high-intensity CT group (HCT, n = 22) or a moderate-intensity CT group (MCT, n = 24). A control group (CON, n = 21) comprised age-matched individuals who were not involved in any regular training regime. CT protocols were included in the experimental group’s training sessions 3 times per week over 24 weeks as part of their usual weekly training regime. Based on the HR zone method, CT protocols included high- or moderate-intensity (85–95% HRmax or 75–85% HRmax) series of 3 different sets of upper- and lower-body strength exercises with articular and muscular mobilization, all culminated with 40-m sprints. Physical fitness was evaluated by the Eurofit test which included the flamingo balance (FLB), plate tapping (PLT), sit-and-reach (SAR), standing broad jump (SBJ), handgrip (HG), sit-ups (SUP), bent arm hang (BAH), 10×5 m shuttle run (SHR), and the Physical Working Capacity test (PWC170). The two-way ANOVA indicated group×time interaction effects for 5 components: the largest was for the SBJ (F2,63 = 42.895, p < 0.001, η2 = 0.577), and the lowest for the SHR (F2,63 = 5.006, p < 0.01, η2 = 0.137) indicating better improvements in the HCT compared to the MCT group. Furthermore, for HCT and MCT groups the highest pre- to post-intervention percentage changes were for the FLB and the SAR, while in the CON group the changes of all physical fitness components were not significant (p < 0.05). In conclusion, the intensity-controlled total-body CT protocol incorporated into a standard soccer training program is effective for enhancement in physical fitness performance in prepubertal soccer players.