高速电弧喷涂再制造曲轴质量和效率优化研究

为提高自动化高速电弧喷涂再制造发动机曲轴的效率和涂层的性能,研究了一种新型的自动化高速电弧喷涂再制造发动机曲轴喷涂路径,利用扫描电镜(SEM)、X射线衍射仪(XRD)和材料力学性能试验设备分别测试了涂层的微观组织和结合强度.实验结果表明:涂层组织均匀、致密,为铁素体韧性相与固溶体、金属间化合物的复合组织,采用新喷涂工艺制备涂层性能较好,大大提高了喷涂效率和涂层在曲轴轴颈圆角处的结合强度,降低了再制造成本和喷涂时间,节能、节材及环保效果显著,应用前景广阔.     

Evaporation heat and mass transfer in natural convection pipe flow

Abstract

A numerical analysis has been performed to examine film evaporation on natural convection heat and mass transfer in a vertical pipe. Coupled governing equations for liquid film and induced gas flow were simultaneously solved by the implicit finite difference method. Results for interfacial heat and mass transfer coefficients are specifically presented for ethanol film and water film vaporization. The predicted results indicate that the heat transfer from gas‐liquid interface to the gas flow is predominated by the transport of latent heat in association with film evaporation. The results are also contrasted with those of zero film thickness and show that the assumption of extremely thin film thickness made by Chang et al. [5] and Yan and Lin [19] is only valid for a system with a low liquid Reynolds number Re _l1. But as the liquid Reynolds number is high, the assumption becomes inappropriate.     

Synthesis of Poly(DL-Lactide-Co-Glycolide) Nanoparticles with Entrapped Magnetite by Emulsion Evaporation Method

The goal of this study was to synthesize Poly(DL-lactide-Co-glycolide) nanoparticles with entrapped magnetite, of under 100 nm in diameter, for future drug delivery applications. The emulsion evaporation method was selected to form poly(lactide-co-glycolide) (PLGA) nanoparticles with entrapped magnetite (Fe₃O₄) in the polymeric matrix, in the presence of sodium dodecyl sulfate (SDS) as a surfactant. Magnetite, a water-soluble compound, was surface functionalized with oleic acid to ensure its efficient entrapment in the PLGA matrix. The inclusion of magnetite with oleic acid (MOA) into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by dialysis, performed to eliminate the excess SDS, and lyophilization. The synthesized nanoparticles ranged in size from 38.6 to 67.1 nm for naked PLGA nanospheres and from 78.8 to 87.2 nm for MOA-entrapped PLGA nanospheres. The entrapment efficiency ranged from 57.36% to 77.3%.     

Influence of polymer blends on the characterization of gliclazide – encapsulated into poly (Æ-caprolactone) microparticles

Gliclazide (GLZ)-loaded microparticles made with a polymeric blend were prepared by a solvent evaporation technique. Organic solutions of two polymers, poly(?-caprolactone) (PCL) and Eudragit RS (E RS) or ethyl cellulose (EC), in different weight ratios, and 33.3% of GLZ were prepared and dropped into aqueous solution of poly vinyl alcohol, in different experimental conditions, achieving drug-loaded microparticles. The obtained microparticles were characterized in terms of yield of production, shape, size, surface properties, drug content, and in vitro drug release behavior. The physical state of the drugs and the polymer was determined by scanning electron microscopy (SEM), Fourier transform infra red and differential scanning calorimetry. Following the in vitro release studies microparticles made from blends of polymer, PCL/E RS or EC showed slower drug release than microparticles made from single PCL polymer. Surface morphology also revealed presence of porous and spherical structure of microparticles. Microparticles showing sustained release of GLZ were examined in rabbits and plasma GLZ concentrations were calculated using HPLC method of assay.     

Modified nanoprecipitation method to fabricate DNA-loaded PLGA nanoparticles

Objective: The objective of this study was to formulate DNA-loaded poly(d,l-lactide-co-glycotide) (PLGA) nanoparticles by a modified nanoprecipitation method. Methods: DNA-loaded PLGA nanoparticles were prepared by the modified nanoprecipitation method and the double emulsion/solvent evaporation method. The characterizations of DNA-loaded nanoparticles such as entrapment efficiency, morphology, particle size, zeta potential, structural integrity of the loaded DNA, and stability of the loaded DNA in PLGA nanoparticles against DNase I, in vitro release, cell viability and in vitro transfection capability were investigated. Results: The resulted PLGA nanoparticles by the modified nanoprecipitation method had uniform spherical shape, narrow size distribution with average particles size near 200 nm, negative zeta potential of ?12.6 mV at pH 7.4, and a sustained-release property in vitro. Plasmid DNA could be efficiently encapsulated into PLGA nanoparticles (>95%) without affecting its intact conformation using this modified nanoprecipitation method, which was superior to the double emulsion/solvent evaporation method. The PLGA nanoparticles were much safer to A549 cell compared to commercial Lipofectamine 2000 and could successfully transfer plasmid-enhanced green fluorescent protein into A549 cells. Conclusion: In conclusion, the modified nanoprecipitation method could be applied as an efficient way to fabricate DNA-loaded PLGA nanoparticles instead of the conventional double emulsion/solvent evaporation method.     

基于时序特征数据高效索引技术的物联网感知设备安全自动监测技术

物联网设备已经被广泛应用于各个领域,为保证物联网的安全,排除内部隐患,基于时序特征数据高效索引技术设计物联网感知设备安全自动监测方法。结合时序特征数据高效索引技术提取物联网信息特征,在报文传输过程的基础上,区分不同流量数据之间的差异、恶意攻击软件与感知设备的系统特征,计算样本数据的表征值,得到物联网感知设备的原始信息特征。对数据特征进行分类,计算其数据内的缺失值和错误值,得到特征向量的筛选优化结果,计算训练损失函数,调整实际操作的阈值,保证数据特征分类的准确性。搭建物联网感知设备监测模型,训练判别器,进行物联网的自动监测。分别对数据包、字节以及数据流量进行识别,该监测技术可以准确地区分良性数据与攻击数据,从而保证物联网感知设备的安全。     

Selective Growth of Vertical-aligned ZnO Nanorod Arrays on Si Substrate by Catalyst-free Thermal Evaporation

By thermal evaporation of pure ZnO powders, high-density vertical-aligned ZnO nanorod arrays with diameter ranged in 80–250 nm were successfully synthesized on Si substrates covered with ZnO seed layers. It was revealed that the morphology, orientation, crystal, and optical quality of the ZnO nanorod arrays highly depend on the crystal quality of ZnO seed layers, which was confirmed by the characterizations of field-emission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence measurements. For ZnO seed layer with wurtzite structure, the ZnO nanorods grew exactly normal to the substrate with perfect wurtzite structure, strong near-band-edge emission, and neglectable deep-level emission. The nanorods synthesized on the polycrystalline ZnO seed layer presented random orientation, wide diameter, and weak deep-level emission. This article provides a C-free and Au-free method for large-scale synthesis of vertical-aligned ZnO nanorod arrays by controlling the crystal quality of the seed layer.     

立式热虹吸再沸器HTRI优化设计

立式热虹吸再沸器是间壁式换热器里计算最为复杂的一类换热器,结合工作实践,在分析工艺流体在再沸器换热管内物理变化过程和间壁换热器传热研究的基础上,利用HTRI软件对立式热虹吸再沸器进行优化设计。     

国内外离子膜法烧碱生产技术综述(续完)

对目前国内外离子膜法烧碱生产装置的相关工艺进行了系统的阐述.     

罗布泊盐湖卤水等温蒸发研究

罗布泊盐湖卤水属含钾硫酸镁亚型卤水。通过罗布泊罗北凹地卤水等温（25℃）蒸发试验,获得卤水在等温蒸发过程中的析盐规律及析盐质量分数规律,为盐田工艺及卤水开发利用提供了可靠依据。