FDM 3D打印工艺参数对PLA制件力学性能的影响

采用五因素四水平正交试验设计,对16组不同工艺参数(打印层厚、填充密度、打印温度、填充速度、外壳厚度)的FDM 3D打印聚乳酸(PLA)制件力学性能进行了测试和结果分析,确定了影响PLA制件力学性能的主要因素,其中,外壳厚度对制件力学性能影响最为明显,打印温度影响最小,同时分析得到了在打印层厚0.15 mm,填充密度40%,打印温度210℃,填充速度60 mm/s,外壳厚度1.6 mm条件下可获得力学性能最佳的制件。最后对试验数据进行回归分析,拟合得到了FDM打印工艺参数与PLA制件力学性能指标的数学模型;通过对不同打印工艺参数的试样进行试验验证,表明该模型拟合误差小(5%以内),可靠性高,可用来对FDM 3D打印制件的加工提供参考。     

Tungsten-based heterogeneous multilayer structures via diffusion bonding

Recent work has shown that tungsten (W) and other refractory metals with body-centered cubic (bcc) structures exhibit certain novel behavior when their grain size, d, is refined into the ultrafine (UFG, 100 nm < d < 1000 nm) or nanocrystalline (NC, d < 100 nm) regime. For example, it has been shown that bcc refractory metals with such microstructures show decreased strain rate sensitivity besides their elevated strength and vanishing strain hardening response. Consequently, under both quasi-static and high-strain-rate loading, plastic instability in the form of shear banding becomes the dominant mode of plastic deformation. Such behavior is long sought-after in certain applications. However, due to the technology used to refine the grain size (primarily severe plastic deformation), the inability to scale the dimensions of the material may limit wider use and application of UFG/NC bcc refractory metals. In this work, the feasibility was demonstrated of production of large-scale W parts using a diffusion bonding method. The microstructure, preliminary mechanical properties, and issues and challenges associated with the fabrication procedures were examined and discussed. It is envisioned that diffusion bonding may serve as a promising technology for scaled-up fabrication of UFG bcc refractory metals for the targeted application.     

新型纳米平板陶瓷膜在纸箱生产废水回用中的工程应用

采用混凝沉淀+水解酸化+MBR+活性炭吸附组合工艺来回用纸箱厂废水。MBR膜采用的是新型纳米平板陶瓷膜。介绍了各处理段的工艺特点、构筑物的设计尺寸、设备选型等,并对新型纳米平板陶瓷膜的清洗进行了介绍。系统运行一年,出水水质稳定,优于≤城市污水再生利用城市杂用水水质≥GB/T 18920-2002表1中的城市绿化排放标准,即BOD5≤20 g/L,浊度≤10 NTU,色度≤30,并分析了本工程的处理成本及所产生的经济效益。     

Influence of deposition parameters on surface morphology and application of CuInS2 thin films in solar cell and photocatalysis

Copper indium disulfide (CuInS₂) thin films as an absorption layer for solar cell and photocatalytic degradation of organic pollutants, were successfully electrodeposited on the FTO coated glass substrate using the simple and inexpensive electrodeposition method and a sulfurization process. The effects of the Cu/In molar ratio, annealing temperature and kind of Cu²⁺ precursor (Cu(salen) and Cu(acac)₂ as novel Cu²⁺ precursors) on the structural and morphological properties of samples were examined. The XRD diffraction patterns and energy dispersive spectroscopy measurements exhibit that high-quality film with superior crystalline structure was formed in the presence of Cu(salen) as Cu²⁺ precursor. Also, we found that a suitable heat treatment temperature could suppress the CuS phases and form well-crystallized CIS. As we know, this is the first reported efficiency for any CuInS₂ superstrate solar cell to date that fabricated using Cu(salen) as Cu²⁺ precursor. In addition, the photocatalytic degradation of organic dye in the presence of as-synthesized CuInS₂ thin films was studied. The as-prepared semiconductor photocatalysts have a good reusability; it can be successfully reused for 5 times recycling photoactivity tests.     

Construction of BiVO4 microspheres sensitized TiO2 NTAs for the enhanced photocatalytic mineralization of organic dyes

In the present work, BiVO₄ microspheres were deposited on TiO₂ NTAs via the solvothermal method using urea as the mineralizer. The binary heterojunction formation significantly enhanced the solar response region and intensity, and the electron transfer path was built at the interface of two semiconductors, which was the main reason for the enhanced photoelectrochemical and photocatalytic performances. The S-2 electrode prepared with urea concentration of 2 mol/L displayed the high visible light photocurrent of 73.76 μA/cm² and photovoltage of −0.30 V. Furthermore, the S-2 photocatalyst also showed excellent photocatalytic decoloration ability of MO, RhB and MB dyes, and the corresponding decomposition efficiencies were 55.82%, 41.62% and 89.90% under solar irradiation. Except for the organic dyes, Cr(VI) ions also could be reduced into Cr(III), and the photocatalytic efficiency achieved 74.05% after 3 h solar irradiation. The active group and photocatalytic mechanism were proposed to illuminate the essential reason. The experimental results indicated that the novel BiVO₄/TiO₂ NTAs with binary heterojunction are attractive photocatalysts for the dyeing and printing water treatment.     

Parallel color-coding

We present new parallelization and memory-reducing strategies for the graph-theoretic color-coding approximation technique, with applications to biological network analysis. Color-coding is a technique that gives fixed parameter tractable algorithms for several well-known NP-hard optimization problems. In this work, by efficiently parallelizing steps in color-coding, we create two new biological protein interaction network analysis tools: Fascia for subgraph counting and motif finding and FastPath for signaling pathway detection. We demonstrate considerable speedup over prior work, and the optimizations introduced in this paper can also be used for other problems where color-coding is applicable.     

Evaluation of anaerobic co-digestion of spent brewery grains and an azo dye

Anaerobic batch biodegradation of spent brewery grains (SBG) was investigated in the presence of co-substrates and a monoazo dye (Acid Orange 7 – AO7) under mesophilic and thermophilic regimes. The highest values for the yield coefficient of biogas (STP) on substrate (Y_bs) were obtained under mesophilic conditions (0.381–0.516 Lbiogas/g COD_removed and 0.147 to 0.475 L_biogas/g COD_removed for mesophilic and thermophilic regimes, respectively). A stimulation of the degradation of SBG associated with microbial growth was observed in the presence of co-substrates (glucose and acetate). Supplemented co-substrates also lowered the residual COD leading to an increase in the COD removal efficiency, particularly under thermophilic regime (from 41% to 70%). Although biogas yield (Y_bs) indicates a decrease in the presence of the dye, suggesting that it has inhibitory effects, the overall COD removal was not significantly altered. An increase of colour removal was observed when the temperature of the operation was increased (87 ± 2% and 93 ± 1% for mesophilic and thermophilic reactors, respectively), which could be explained by both faster adsorption and biotic reductive cleavage of azo dye bond mechanisms. These results indicate that raw SBG is more prone to biodegradation under an anaerobic mesophilic regime; hence its bio-energetic valorisation is possible.     

网络化雷达现状及技术发展趋势

随着新的作战对象和作战样式的出现,以及作战环境更加复杂,仅依靠单个雷达节点的能力已经越来越难以满足新的作战需求。文中针对网络化雷达这一新体制雷达开展研究,通过分析国外网络化雷达系统发展现状、趋势及关键技术,总结对我国网络化雷达技术发展的经验启示,为我国网络化雷达系统发展提供技术参考。     

Effect of segment structures on the hydrolytic degradation behaviors of totally degradable poly(L-lactic acid)-based copolymers

A series of high-molecular-weight terpolymers named PTG-b-LG and PT-b-LG were synthesized based on the macroinitiators of PTG copolymers and PTMC, respectively. In vitro degradation of PTG-b-LG and PT-b-LG was carried out by immersing into PBS, in comparison with that of PLLA. Mass loss, water uptake, GPC, DSC, WAXD, and ¹H NMR were examined for the degradation study. It was found that PTG-b-LG degraded faster than PT-b-LG and PLLA due to the Di-random block structure, which had lower regularity of chain and lower crystallinity. The compositional changes appeared to be more complex, but the molar mass decreased owing to chain fragmentation caused by hydrolysis. Moreover, morphological changes were also observed during the degradation in all situations with the crystallization of by-products and a preferential degradation of amorphous domains. Specifically, PTG-b-LG presented an adjustable degradation rate and may be used for the fabrication of totally biodegradation stents in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47887.     

橡胶在季戊四醇酯基础油中溶胀规律的理论模型

采用季戊四醇分别和不同碳数脂肪酸合成一系列单酸季戊四醇酯，测定5种橡胶在不同单酸季戊四醇酯中的体积变化率，探索可解释和预测橡胶在季戊四醇酯中溶胀趋势的最佳理论模型。结果表明：季戊四醇酯的摩尔体积(Vm)和非极性参数(NPI)，以及季戊四醇酯与橡胶之间的Hildebrand一维溶解度参数差值(Δδ)和能量差(Ra)在解释和预测季戊四醇酯对橡胶的溶胀规律方面皆具有一定的局限性。提出了抗溶胀参数(ΔAS)可解释和预测季戊四醇酯对5种橡胶的溶胀趋势，以及同碳数正、异构酯对5种橡胶溶胀的差异，弥补和修正了Vm、NPI、Δδ和Ra的不足。