Influence of resin composition on rheology and polymerization kinetics of alumina ceramic suspensions for digital light processing (DLP) additive manufacturing

Alumina ceramics with optimized microstructures and mechanical properties were obtained by the attractive digital lighting processing (DLP) additive manufacturing methodology in the present study. A acrylate-based resin system was designed for the alumina powders with a mean particle size of 0.5 μm. The influence of oligomer on the viscosity and polymerization kinetics of the ceramic suspensions has been elaborately discussed by rheology, curing depth and photo-DSC characterizations. The results indicated that the introduction of oligomer has improved the cross-linking density of resins and decreased the critical dose of energy for resin polymerization, which contributed to a tougher ceramic-resin slice with higher dimensional accuracy. Densifying processes including debinding and high temperature sintering of the ceramic parts were conducted according to the TG-DTA characterizations, alumina ceramics with uniform microstructures and eliminated delamination or intralaminar cracks were finally obtained. The flexural strength was 471 MPa for the ceramics obtained from the resin composition containing 20 wt% oligomer, Weibull modulus for the ceramics were determined to be 17.31 by evaluating thirty all sides polished ceramics, indicating the highly uniform property of the ceramics fabricated by DLP additive manufacturing.     

Effects of manufacturing process and surface treatments on mechanical properties of PLA/SCF composites using extrusion printing

Short carbon fiber (SCF) reinforced polylactic acid (PLA) composites were fabricated by extrusion printing, and the effects of process parameters and surface treatments on the mechanical properties of composites were studied. Based on the rheological properties of composites and the extrusion process simulation, pure PLA specimens and PLA/SCF specimens were manufactured under different printing parameters. Three kinds of surface treatment were adopted to improve the mechanical properties. The experimental results show that SCF can effectively improve the tensile strength and bending strength, but the compressive strength decreased. The specimen had the best mechanical properties when the layer height was 0.1 mm and the nozzle diameter was 0.6 mm. The mechanical properties can be further improved by coupling agent coating method, and the compressive strength was even higher than that of pure PLA specimen. The research in this paper can provide a reference for the fabrication of thermoplastic composites with excellent mechanical properties by extrusion printing.

     

Glutamine Induced High-Quality Perovskite Film to Improve the Efficiency of NIR Perovskite Light-Emitting Diodes

Formamidine lead iodide (FAPbI₃) is an important material for realizing high-performance near-infrared light-emitting diodes (NIR-LEDs). However, due to the uncontrollable growth of solution-processed films which usually causes low coverage, and poor surface morphology, the development of FAPbI₃-based NIR-LEDs is hindered, restraining its potential industrial applications. In this work, by employing glutamine (Gln) in perovskite precursor, the quality of FAPbI₃ film is improved significantly. Due to the ameliorated solution process by the organic additive, the film coverage over the substrate is substantially enhanced. Meanwhile, the trap state of grain is largely reduced. Consequently, NIR perovskite LEDs are demonstrated with a maximum external quantum efficiency (EQE) of 15% with the emission peak at 795 nm, which is four times higher than the device with pristine perovskite film.     

Boosting semantic segmentation via feature enhancement

Semantic segmentation aims to map each pixel of an image into its corresponding semantic label. Most existing methods either mainly concentrate on high-level features or simple combination of low-level and high-level features from backbone convolutional networks, which may weaken or even ignore the compensation between different levels. To effectively take advantages from both shallow (textural) and deep (semantic) features, this paper proposes a novel plug-and-play module, namely feature enhancement module (FEM). The proposed FEM first uses an information extractor to extract the desired details or semantics from different stages, and then enhances target features by taking in the extracted message. Two types of FEM, i.e., detail FEM and semantic FEM, can be customized. Concretely, the former type strengthens textural information to protect key but tiny/low-contrast details from suppression/removal, while the other one highlights structural information to boost segmentation performance. By equipping a given backbone network with FEMs, there might contain two information flows, i.e., detail flow and semantic flow. Extensive experiments on the Cityscapes, ADE20K and PASCAL Context datasets are conducted to validate the effectiveness of our design. The code has been released at https://github.com/SuperZ-Liu/FENet.     

Effect of silver oxide additives on structural,optical dispersion and protection features of lead boro-phosphate glasses

This work presents the structural, optical, refractive index dispersion, and shielding properties of Ag-containing lead-boro-phosphate glasses. The glasses were prepared using the classic melt-quenching method, in which the Ag₂O concentration was varied in each synthesis. The precipitation of Ag NPs was proved by the appearance of the (200) crystal plane in the XRD patterns and confirmed by the homogeneous distribution of spherical agglomerates observed in TEM images. FTIR and Raman analyses have revealed a network depolymerization process resulting from the distortion of the PO₄ units and the formation of Ag NPs. Therefore, the Ag ions contribute at high concentrations to an increase in the glass density and a reduction in the optical band gap energy. Ellipsometry parameters indicate that the glass becomes more optically dispersive due to the Ag NPs formation, which improves its performance for several potential applications in multi-functional optical devices. The mass attenuation factors are determined in the energy range of 15 keV–15 MeV and are very sensitive to the silver content at low energies. The Half value layer (HVL) decreases with the amount of Ag₂O, indicating the improvement in the material's ability to attenuate radiation. The results show that the glass sample with the highest Ag content has the highest shielding effectiveness.     

高灵敏度网状石墨烯微弱压力传感器的研究北大核心

为了改善微弱压力传感器的灵敏度，利用微结构来产生压阻效应的方法，制备出一种性能优异的压力传感器。研究了三种不同结构的石墨烯压力传感器，并设计和研究了石墨烯压力传感器的版图结构、工艺制备流程和材料表征。最后，对三种不同结构的石墨烯压力传感器进行了灵敏度测试。实验结果表明，网状结构的石墨烯压力传感器具有较高的灵敏度，在低压强下(0～200 Pa)的灵敏度可达到0.303 kPa-1,最低可检测到24.5 Pa的压强。该网状结构的石墨烯压力传感器是一种可以感知微弱压力变化的高性能压力传感器。     

车用涡轮增压器瞬态响应性评估与测试

基于车用涡轮增压器瞬态响应的影响因素，提出独立于内燃机的车用涡轮增压器瞬态响应评估指标D_x。通过数值模拟和试验的方法研究在不同终了转速下D_x随不同初始压比的变化以及转子转动惯量、涡轮效率和压气机效率对D_x影响。研究结果表明：试验结果与仿真结果吻合较好，证明该测试方法可用于涡轮增压器的瞬态性能测试以及增压器瞬态性能的影响因素研究。使用误差传播理论对试验测得的瞬态响应评估参数D_x值进行系统误差估计，试验测得的系统不确定度为1.35%。     

农产品射频杀菌钝酶技术研究进展

农产品中通常含有大量的腐败菌和内源酶，这些腐败菌和内源酶会对农产品品质造成不良的影响。射频是一种介电加热技术，其加热速度快、效率高，能有效地灭活农产品中的微生物和内源酶而且对农产品的品质(如色泽、质地以及营养成分等)影响较小。文章综述了射频杀菌钝酶技术的作用机制以及近年来在农产品加工中的应用进展，指出了射频杀菌钝酶技术的不足及解决方案，并对射频杀菌钝酶技术未来在农产品和食品中的应用进行了展望。     

聚乙烯醇纳米纤维膜/罗纹空气层织物复合吸声材料的制备及其性能

为探究针织物基复合吸声材料在降低噪声方面的可应用性，通过制备聚乙烯醇纳米纤维膜与罗纹空气层织物复合材料，研究其吸声及其它基本性能，采用正交试验法对影响材料声学性能的因素进行分析，通过对实验数据进行极差分析，探究该材料可用于吸声的最佳参数。结果表明：复合材料吸声性能的影响因素从大到小依次为：覆膜情况、密度盘刻度、纱线种类；当密度盘刻度为2、毛/腈(50/50)混纺纱覆膜的情况下，复合材料的吸声效果达到最佳，平均吸声系数高于0.3,可用作吸声材料；聚乙烯醇纳米纤维膜的增加对织物吸声性能有很大改善；织物的吸声系数随着织物密度的增加而提高。     

深度学习与影像自动化评估的肾肿瘤剜除术难度预分析

目的 早期肾癌可以通过肾肿瘤剜除术进行有效治疗，为了降低手术难度和减少手术并发症，需要对手术的难度进行合理有效的评估。本文将深度学习、医学影像组学和图像分析技术进行结合，提出一种基于CT（computed tomography）影像的肾肿瘤剜除术难度自动评估方法。方法 首先建立一个级联的端到端分割模型对肾脏、肾肿瘤和腹壁同时进行分割，同时融入子像素卷积与注意力机制，保证了小体积肿瘤分割的精确性；然后使用影像组学特征对误判的肾肿瘤进行去除；最后依据分割结果，采用国际标准的梅奥肾周粘连概率（Mayo adhesive probability，MAP）评分和R.E.N.A.L评分对肾脏和肾肿瘤进行自动化的评估计算，并根据计算结果得出肾肿瘤剜除术难度。结果 将实验的自动化评估结果与三甲医院泌尿科的3位医疗专家的结果进行对比，从预测的平均结果来看，超过两个专家，与最好的专家相差仅0.1%。平均预测时间，单个肿瘤约为244 ms，标准差只有8 ms，专家评估时间约为26 s，标准差在3 s左右，自动评估速度是人工的108倍左右。结论 自动化评估结果整体上与专家评估水平基本一致，同时评估速度更加快速稳定，可以有效替代专家进行自动化评估，为术前准确诊断、手术方案个体化规划和手术入路选择提供准确可靠的决策支持，给手术难度诊断评估提供智能化的医疗解决方案。