Fabrication of phytic acid embellished kaolinite and its effect on the flame retardancy and thermal stability of ethylene vinyl acetate composites

A modified kaolinite by grafting with phytic acid (PA-g-Kaol) is fabricated, and it was introduced into ethylene vinyl acetate (EVA) with intumescent flame retardancy (IFR) together to improve the flame retardancy of EVA composites. The results show the limiting oxygen index value of EVA/ (18.0 wt% IFR)/ (2.0 wt% PA-g-Kaol) is 30.8%. Meanwhile, there is only one dripping produced in the vertical burning test. What's more, the flame-retardant mechanism is demonstrated by TG-IR, real-time-IR and GC–MS analysis. The results indicate that some pyrolytic products of IFR and PA-g-Kaol, like ammonia and phosphoric acid, catalyze the crosslinking of EVA and flame retardant, the resultant compact char protects the substrate from further burning.     

T型连接井交汇水流数值模拟

A numerical simulation is made on Wangqingtuo T-junction Chamber, the confluence in the downstream junction chamber without outlet is analyzed, and then the impact of the direction of the inflow from reservoir on the flow pattern in the downstream triple-hole box culvert and the position of the full-uniform flow through the downstream cross-section is estimated as well. The study result can provide a reference for the similar project concerned.     

改进RetinaFace的自然场景口罩佩戴检测算法

新型冠状病毒可以通过空气中的飞沫、气溶胶等载体进行传播，在公共场所下正确佩戴口罩可以有效地防止病毒的传播。提出了一种自然场景下人脸口罩佩戴检测方法，对RetinaFace算法进行了改进，增加了人脸口罩佩戴检测任务，优化了损失函数。在特征金字塔网络中引入了一种改进的自注意力机制，增强了特征图的表达能力。建立了包含3 000张图片的数据集，并进行手工标注，用于网络训练。实验结果表明该算法可以有效进行口罩佩戴检测，在自然场景视频中也取得了不错的检测效果。     

Influence of Yb Concentration on the Optical Properties of CaF2 Transparent Ceramics Codoped with Er and Yb

Er, Yb:CaF₂ nanoparticles with different Yb concentrations were synthesized by a coprecipitation method using nitrates as raw materials. X‐ray powder diffraction and transmission electron microscopy analysis showed that the nanoparticles were single fluorite phase and the nanoparticle size was found to decrease with increasing Yb concentrations. The obtained nanoparticles were hot‐pressed at 800°C under 30 MPa under vacuum environment to fabricate Er, Yb:CaF₂ transparent ceramics. The influence of Yb ion concentrations on the optical transmission, microstructure, and luminescence properties of Er, Yb:CaF₂ transparent ceramics were investigated. The addition of Yb ions was found effectively to reduce grain size and has a positive effect on improving the optical transmission of Er, Yb:CaF₂ transparent ceramics. The highest transmittance in the near‐infrared spectral region of the Er, Yb:CaF₂ transparent ceramic reached about 90%. The green, red, and near‐infrared emission intensities were found to increase with increasing Yb concentration.     

Synthesis and luminescence characterization of Pr3+, Gd3+ co-doped SrF2 transparent ceramics

Pr³⁺, Gd³⁺ co-doped SrF₂ transparent ceramic, as the potential material for visible luminescent applications, was prepared by hot-pressing of precursor nanopowders. The microstructure, phase compositions, and in-line transmittance, as well as the photoluminescence properties were investigated systematically. Highly optical quality Pr,Gd:SrF₂ transparent ceramic with nearly pore-free microstructure was obtained at 800°C for 1.5 hours. The average in-line transmittance of the x at.% Pr, 6 at.% Gd:SrF₂ (x = 0.2, 0.5, 1.0, 2.0) transparent ceramics reached to 87.3 % in the infrared region. The photoluminescence spectra presented intense visible light emissions under the excitation of 444 nm, the main intrinsic emission bands located at 483 and 605 nm, which were attributed to the transitions of Pr³⁺: ³P₀ → ³H₄ and ¹D₂ → ³H₄, respectively. With the co-doping of Gd³⁺ ions, the emission intensity of the Pr:SrF₂ transparent ceramic was greatly enhanced. All the emission bands of x at.% Pr, 6 at.% Gd:SrF₂ transparent ceramics exhibited the highest luminescence intensity with the 1.0 at.% Pr³⁺ doping concentrations, whereas the lifetimes decreased dramatically with the Pr³⁺ doping contents increasing from 0.2 to 2.0 at.% due to its intense concentration quenching effect. The 1 at.% Pr, 6 at.% Gd:SrF₂ transparent ceramic is a promising material for visible luminescent device applications.     

矩形通道内冲孔矩形小翼涡流发生器的流动换热特性

雷诺数Re=214～10 703时,通过数值模拟方法对布置有冲孔和无孔的两种矩形小翼涡流发生器的矩形通道进行了传热和流阻特性的研究。计算结果表明:在低雷诺数下,冲孔矩形小翼涡流发生器的传热因子j值与无孔矩形小翼涡流发生器相差不大,而在高雷诺数下,冲孔涡流发生器的传热因子j值略低于无孔涡流发生器,大约低1.03%～3.05%。在相同的雷诺数下,无孔矩形小翼涡流发生器的阻力因子f大于冲孔涡流发生器,而且随着雷诺数的增大二者的差距也越来越大。通过对比综合性能指标可知,两种通道的综合性能指标均随着雷诺数的增加而减小,而且冲孔矩形小翼涡流发生器的综合性能要优于无孔矩形小翼涡流发生器。     

The effect of antimicrobial peptide HX-12C on the properties of chitosan/polyacrylic acid hydrogel

Antimicrobial peptide (AMP) hydrogel is a novel biomaterial widely used in wound healing. However, there have been limited studies investigating the effect of AMP on hydrogel properties so far. Therefore, this study aimed to examine the influence of the AMP HX-12C on the chitosan/polyacrylic acid (CS/PAA) double-network (DN) hydrogel. The results showed that the mechanical properties of CS/PAA/HX-12C hydrogel are significantly improved compared with those of CS/PAA hydrogel. The maximum tensile stress increased from 41.0 to 258.5 KPa, and the compression stress required for 80% hydrogel deformation increased from 3.7 to 6.7 MPa. Furthermore, the thermal stability of CS/PAA/HX-12C showed a noticeable enhancement when compared with CS/PAA hydrogel. In addition, the CS/PAA/HX-12C hydrogel exhibited improved porosity and swelling performance. The addition of HX-12C significantly enhanced the antibacterial activity of the hydrogel against Escherichia coli and methicillin-resistant Staphylococcus aureus. Cytotoxicity test showed that the viability of L929 cell remained above 90% after treatment with CS/PAA/HX-12C hydrogel extract, indicating the good biocompatibility. In conclusion, AMP assuredly enhances the mechanical property, swelling performance and antimicrobial activity of hydrogel. The CS/PAA/HX-12C hydrogel shows potential for use as anti-infective medical material.     

温压实验液态产物中菲和蒽系列的演化特征

对华北中元古界下马岭组低熟海相页岩进行温压(Ⅰ系列)和温控(Ⅱ系列)模拟实验,并对原始样品和实验过程中的液态产物进行GCMS分析。结果表明:样品含较高丰度的菲、艹屈、萘等系列化合物,液态产物中检出了实验过程中新产生的蒽、甲基蒽和苯并萘并噻吩;随着温度的升高,菲系列中丰度较高的9-甲基菲、1-甲基菲逐渐向热稳定性更好的3-甲基菲、2-甲基菲转化,菲的相对丰度先减小后增大;模拟实验样品中检出的蒽系列化合物与温度呈正相关,表明其来源与热演化过程有关;温压实验过程中检测出丰度较高的苯并萘并噻吩,而其他温度段几乎检测不到,说明该化合物的形成需要适当的温度和压力;压力增大会抑制菲的烷基化和抑制蒽系列化合物形成,但会促进9-甲基菲的转化和苯并萘并噻吩的形成。     

热轧板带钢工艺润滑系统改造

详细分析了唐钢热轧工艺润滑系统在原系统设计上的工作原理与缺陷,并通过技术攻关和改造成功地解决了系统设计和设备选型中的不足.经过一年的生产实践表明,新改造的热轧工艺润滑系统完全能满足使用要求,不仅大大提高了板带表面质量,而且明显消除了薄规格轧制时机架的震动并降低了能耗.     

三角翼涡流发生器纳米氧化镁颗粒污垢特性

为了探究三角翼涡流发生器的纳米氧化镁颗粒污垢特性, 选用粒径为50 nm的氧化镁颗粒配制的胶体溶液为研究对象, 研究了在不同水浴温度、颗粒浓度、流速、三角翼间距以及不同布置等工况下三角翼涡流发生器的污垢特性。结果表明:三角翼涡流发生器具有抑垢特性, 水浴温度、浓度、流速对其抑垢能力及结垢速率均有影响, 水浴温度升高、颗粒浓度降低以及工质流速升高都会导致三角翼的抑垢能力增强。三角翼不同列间距的抑垢能力随着布置方式的改变而改变, 采用均匀分布布置形式时40 mm列间距的抑垢能力最强, 而采用同列数布置时80 mm列间距的抑垢能力最强。