Fracture toughness evaluation of silicon nitride from microstructures via convolutional neural network

The fracture toughness of silicon nitride (Si₃N₄) ceramics was evaluated directly from their microstructures via deep learning using convolutional neural network models. Totally 156 data sets containing microstructural images and relative densities were prepared from 45 types of Si₃N₄ samples as input feature quantities (IFQs) and were correlated to the fracture toughness as an objective variable. The data sets were divided into two groups. One was used for training, resulting in the creation of regression models for two kinds of IFQs: the microstructures only and a combination of the microstructures and the relative densities. The other group was used for testing the validity of the created models. As a result, the determination coefficient was approximately 0.8 even when using only the microstructures as the IFQs and was further improved when adding the relative densities. It was revealed that the fracture toughness of Si₃N₄ ceramics was well evaluated from their microstructures.     

A High-Rate Li–CO2 Battery Enabled by 2D Medium-Entropy Catalyst

Lithium-air batteries based on CO₂ reactant (Li–CO₂) have recently been of interest because it has been found that reversible Li/CO₂ electrochemistry is feasible. In this study, a new medium-entropy cathode catalyst, (NbTa)_0.5BiS₃, that enables the reversible electrochemistry to operate at high rates is presented. This medium entropy cathode catalyst is combined with an ionic liquid-based electrolyte blend to give a Li–CO₂ battery that operates at high current density of 5000 mA g⁻¹ and capacity of 5000 mAh g⁻¹ for up to 125 cycles, far exceeding reported values in the literature for this type of battery. The higher rate performance is believed to be due to the greater stability of the multi-element (NbTa)_0.5BiS₃ catalyst because of its higher entropy compared to previously used catalysts with a smaller number of elements with lower entropies. Evidence for this comes from computational studies giving very low surface energies (high surface stability) for (NbTa)_0.5BiS₃ and transmission electron microscopystudies showing the structure being retained after cycling. In addition, the calculations indicate that Nb-terminated surface promotes Li–CO₂ electrochemistry resulting in Li₂CO₃ and carbon formation, consistent with the products found in the cell. These results open new direction to design and develop high-performance Li–CO₂ batteries.     

Producing asphaltene fibres from bitumen-derived asphaltenes for carbon fibre development: Part one–Electrospinning

Bitumen-derived asphaltenes are rich in carbon but of low value and contain other elements such as nitrogen, sulphur, oxygen, vanadium, and nickel. Their use as a feedstock for producing carbon fibre (CF) is largely under-investigated. In this study, electrospinning was used to create asphaltene fibres (AFs), which is a pre-carbon fibre material, from asphaltenes. Various operational parameters were investigated in order to improve the spinning abilities, such as the concentration of asphaltenes in toluene, pumping rate, voltage, and distance between the tip of the needle to the collector. Results indicated that asphaltenes concentrations had the greatest effect on the quality of the produced AFs, with the range of asphaltenes concentrations from 45 to 50 wt.% being suitable for producing the AFs, while voltage, pumping rate, and tip distance had less of an effect on electrospun AF production.     

基于Kullback-Leibler距离的闭环系统传感器微小故障诊断

在闭环控制系统中,当故障幅值较小时,由故障带来的影响会被控制量所掩盖.因此,闭环系统中的微小故障诊断实现更为复杂.本文针对闭环系统中的传感器故障,提出了基于Kullback-Leibler(KL)距离的微小故障在线检测与估计方法.本文首先介绍了KL距离的定义及其在多变量故障检测中的应用,然后提出了结合KL距离与快速移动窗口主成分分析(MWPCA)的在线微小故障检测与估计模型.在高斯分布的假设下,利用系统输入输出残差构造MWPCA的数据矩阵,然后通过在线更新数据矩阵主成分的均值与方差实现KL距离的在线更新,最终实现闭环系统中传感器的在线故障检测与估计.仿真实验表明,该方法能有效实现具有低故障—噪声比(FNR)特性的微小故障诊断.     

Creating new water-soluble Iso- and n-fatty acid arginate hydrochloride with antimicrobial properties

Typically, short- and long-chain lipids from oils exhibit different antimicrobial activities and therefore have been used in agriculture and aquaculture, biomedical therapeutic and antibacterial fields. However, these fatty acids have limitations in terms of bioactive efficacy, thermostability and aqueous solubility. In this study, water-soluble iso-fatty acid arginate hydrochloride derivatives with antimicrobial properties were produced by introducing branched (iso-) chain and other linear- (n-) chain fatty acids to the “arginine” amino acid molecule. The two-step synthetic route was straightforward and provided an efficient 88% and 76% product yields for ethyl n-oleoyl arginate hydrochloride and ethyl iso-oleoyl arginate hydrochloride, respectively. ATR-FT-IR, NMR, and LC-MS-Q-TOF techniques were used to thoroughly characterize and confirm the products. These arginate products had strong antimicrobial activities against Listeria innucua, a Gram-positive bacterium with minimum inhibitory concentrations and minimum bactericidal concentrations ranging from 1.8 µg mL⁻¹ to 29.1 µg mL⁻¹. Therefore, the study demonstrated the development of a novel class of antimicrobial compounds from iso-fatty acids and arginates.     

Electrospinning of ultrafine non-hydrolyzed silk sericin/PEO fibers on PLA: A bilayer scaffold fabrication

We report the feasibility of electrospinning of protein-polymer multilayered scaffolds with selected materials such as non-hydrolyzed silk sericin (SS), polyethylene oxide (PEO), and polylactic acid (PLA), with tuned fiber size and properties for each layer. We present a new innovative way for the electrospinning (ES) of non-hydrolyzed SS mixed with PEO yielding fibers with an average diameter ranging between 120 and 150 nm. Different SS:PEO ratios have been electrospun to study the effect of the concentration of SS protein on the fibers size and shape, as well and their electrospinnability. Electrospun SS:PEO fibers display weak to no mechanical resistance (non-measurable) and their deposition onto a sturdier scaffold is necessary to allow their use in biomedical and/or pharmaceutical fields. Therefore, bilayer scaffolds have been fabricated consisting of a PLA support and SS:PEO fibers obtained from the optimized SS:PEO ratio (1.2:4). They are composed of a sturdy hydrophobic layer of PLA fibers and a layer of sticky hydrophilic SS:PEO fibers. The scaffolds have been characterized extensively by Fourier transforms infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and their resistance to mechanical stress. Finally, hydrophobicity of both layers has been determined by measuring the contact angle of water droplets on the scaffolds, further proving the bilayer nature of the scaffolds.     

Evaluation of pressure and viscous drags of a rising bubble at small Reynolds numbers

Journal of Mechanical Science and Technology - Pressure and viscous drags acting on a bubble rising in a viscous fluid are numerically estimated to obtain the corresponding drag coefficients that...     

Achieving Ultrahigh Electron Mobility in PdSe2 Field-Effect Transistors via Semimetal Antimony as Contacts

Even though atomically thin 2D semiconductors have shown great potential for next-generation electronics, the low carrier mobility caused by poor metal–semiconductor contacts and the inherently high density of impurity scatterings remains a critical issue. Herein, high-mobility field-effect transistors (FETs) by introducing few-layer PdSe₂ flakes as channels is achieved, via directly depositing semimetal antimony (Sb) as drain–source electrodes. The formation of clean and defect-free van der Waals (vdW) stackings at the Sb–PdSe₂ heterointerfaces boosts the room temperature transport characteristics, including low contact resistance down to 0.55 kΩ µm, high on-current density reaching 96 µA µm⁻¹, and high electron mobility of 383 cm² V⁻¹ s⁻¹. Furthermore, metal–insulator transition (MIT) is observed in the PdSe₂ FETs with and without hexagonal boron nitride (h–BN) as buffer layers. However, the layered h–BN/PdSe₂ vdW stacking eliminates the interference of interfacial disorders, and thus the corresponding device exhibits a lower MIT crossing point, larger mobility exponent of γ ∼ 1.73, significantly decreased hopping parameter of T₀, and ultrahigh electron mobility of 2,184 cm² V⁻¹ s⁻¹ at 10 K. These findings are expected to be significant for developing high mobility 2D-based quantum devices.