Investigation of particle flattening behaviour and bonding mechanisms of APS sprayed coatings on magnesium alloys

Magnesium alloys are promising alternatives to other lightweight materials due to their high specific strength and stiffness. However, the use of magnesium alloys is limited by their poor wear behaviour and low corrosion resistance for many industrial applications. The thermal spray technology offers a wide range of possibilities to improve the surface properties of Mg-based components. In this study, three different coating materials, namely Al, NiAl5 and Al₂O₃, were applied on AZ91 and AE42 substrates using the atmospheric plasma spray technology. The investigation was focused on the bonding strength of the coatings and the related bonding mechanisms. For a better understanding of the bonding mechanisms, the flattening behaviour of the spray particles was investigated in correlation with the substrate pre-heating temperature. It was found that NiAl5-particles could well melt the substrate at the surface and deformed it locally; Al-particles did the same but to a lower extent. The dominating bonding mechanism for NiAl5-coatings could be attributed to a metallurgical bonding. For Al-coatings, this mechanism played a more important role once the substrate pre-heating temperature was increased. Al₂O₃ particles in contrast, were less able to deform the substrate in spite of their higher thermal load and the mechanical anchoring remained the main bonding mechanism. The thermo physical properties of the Mg substrate showed also to have an influence on the adhesion of the coatings.     

基于产能约束下的APS管理系统的应用研究

针对国内机械制造行业生产计划排程发展现状,分析了机械制造行业使用ERP系统中生产计划排程存在的缺陷,利用高级生产计划排程（APS）理念,研究了适用于面向订单生产的机械制造企业基于产能约束下的生产计划排程管理系统,以实现生产作业计划的排程、实时调度和生产过程的实时控制。     

黄芪多糖对人用狂犬病疫苗免疫原性的影响

目的研究黄芪多糖对狂犬病疫苗免疫应答的影响。方法将BALB/c小鼠和昆明小鼠各自随机分为2组,即试验组与对照组,分别于0、7d接种冻干人用狂犬病疫苗(Vero细胞)。对照组疫苗用灭菌注射用水稀释,试验组疫苗用10%黄芪多糖(APS)溶液稀释,每只腹腔免疫0·5ml。BALB/c小鼠于15d无菌取脾,进行淋巴细胞转化实验;昆明小鼠在免疫前和第1针免疫后4、7、14、30、45和60d眶静脉采血,分别进行外周血淋巴细胞CTL试验和小鼠中和抗体水平测定。结果试验组疫苗诱导小鼠产生的中和抗体和细胞免疫水平均高于对照组疫苗,二者差异有显著意义。结论黄芪多糖能提高狂犬病疫苗的免疫原性。     

Optical counting of guided particles in a vortex beam as an optical tube by laser-two-focus method

In this study, microscopic particles such as aerosols were counted by Laser-Two-Focus method, L2F, after being trapped and guided by an optical tube. This prevents particles diffusivity as they pass through the Gaussian beam in the L2F method by optical forces such as radiation pressure and photophoretic forces. In optical tube, particles can guid to the center of the beam where the intensity gets zero. A single-charged Bessel Gaussian beam, BG₀₁, is used as the particle guidance beam in this method, which is generated by passing the first-order Laguerre-Gaussian beam, LG₀₁, from an axicon lens. LG₀₁ beam are also produced by using holographic interference grid mask. The results of the theory and simulations showed that by optical guiding of particles in the L2F-method measurement, their transverse turbulence can be reduced by about 60% and then the probability of measuring all particles to be increased by about 30%. Measurements of in-laboratory aerosols less than 3.5 μm with this method showed a 20% increase in their condensation of them compared to the conventional L2F method.     

Application of USP Inlet Extensions to the TSI Impactor System 3306/3320 Using HFA 227 Based Solution Metered Dose Inhalers

ABSTRACT

The objective of this study was to further evaluate the need for a vertical inlet extension when testing solution metered dose inhalers using the TSI Model 3306 Impactor Inlet in conjunction with the TSI Model 3320 Aerodynamic Particle Sizer (APS). The configurations tested using the TSI system were compared to baseline measurements that were performed using the Andersen Mark II 8-stage cascade impactor (ACI). Seven pressurized solution metered dose inhalers were tested using varied concentrations of beclomethasone dipropionate (BDP), ethanol, and HFA 227 propellant. The inhalers were tested with the cascade impactor, and with the TSI system. The TSI system had three different configurations as the manufacturer provided (0 cm) or with inlet extensions of 20 and 40 cm. The extensions were located between the USP inlet and the Model 3306 Impactor Inlet. There were no practical differences between each system for the stem, actuator, or USP inlet. The fine particle mass (aerodynamic mass < 4.7 µm) was affected by extension length and correlated well with the ACI when an extension was present. APS particle size measurements were unaffected by the extension lengths and correlated well to particle size determined from the ACI analysis. It has been confirmed that an inlet extension may be necessary for the TSI system in order to give mass results that correlate to the ACI, especially for formulations having significant concentrations of low volatility excipients. Additionally, the results generated from this study were used to evaluate the product performance of HFA 227 based solution formulations that contain varying concentrations of ethanol as a cosolvent.     

Analysis of the influence of atmospheric plasma spray (APS) parameters on adhesion properties of alumina-titania coatings

Alumina-13 wt% titania wear resistant coatings were deposited using the Atmospheric Plasma Spray (APS) process under several processing conditions. Coating adhesion was then measured locally on cross sections by the indentation test and results were correlated with process variables. In order to identify the most influential factors on adhesion, artificial intelligence was used. The analysis was based on an Artificial Neural Network (ANN) taking into account training and test procedures to predict the dependences of measured property on experimental conditions. This study pointed out primarily that adhesion was largely sensitive to parameters that modified the in-flight particle characteristics (i.e. velocity and temperature). These effects were quantitatively demonstrated and predicted with an optimized neural network structure.     

A Class of Adaptive Cyclostationary Beamforming Algorithms

One of the main benefits of the cyclostationary beamforming algorithms is their ability to extract signals from co-channel interference with only a knowledge of the cycle frequency. In this paper, we study the popular cyclostationary beamformers, and propose five new algorithms, namely, the adaptive cyclic adaptive beamforming (ACAB), adaptive cross-SCORE (ACS), constrained least-squares (CLS), adaptive phase-SCORE (APS), and maximal constrained autocorrelation (MCA) algorithms. All these algorithms are adaptive and have a computational complexity of O(n ²) complex multiplications, where n is the number of array elements. A comparative study of these algorithms is made based on numerical simulations. Each of these algorithms has specific application scenarios. The ACS and the APS algorithms are particularly suited for very adverse signal environments. The ACAB, MCA and cyclic adaptive beamforming (CAB, from the work of Wu and Wong) algorithms can provide good performance in the case of medium or weak interference, while the CLS algorithm is especially suitable for weak interference. The CAB algorithm is shown to be a special case of the least-square self-coherent restoral (LS-SCORE) algorithm. Some insights as to how one can assign carrier frequency and symbol rate during digital modulation are also suggested. The proposed adaptive algorithms are easy to implement, and thus are very promising for applications in wireless and mobile communications. This work was supported by the NSERC of Canada.     

APS喷涂Cr2O3涂层的工程化应用研究

从工程化应用的角度出发,研究了APS喷涂Cr2O3陶瓷涂层的工艺参数对涂层性能的影响.研究结果表明,粉末粒度分布、电弧电流和喷涂距离是影响涂层性能的关键因素,其他辅助条件,如抽风效果,也是获得良好结构涂层不可忽视的关键因素.所制备的性能稳定、均匀的耐磨涂层可满足激光雕刻的要求。     

Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying

The high‐temperature behavior of high‐purity, low‐density (HP‐LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon‐shrouded plasma spraying is described. The high purity yttria‐stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as‐processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP‐LD coatings is compared with that of state‐of‐the‐art electron beam physical vapor deposition TBCs.     

空间辐射对芯片温度场分布影响的研究

简述了ANSYS有限元瞬态热分析方法的基本原理和步骤,推导了瞬态传导辐射微分方程,利用此有限元方法对基于有源像元传感器的探测芯片在轨运行期间温度场进行了计算,得出了详细的温度变化和分布云图情况,研究了不同辐射率的空间辐射对芯片温度分布的影响,比较了芯片在不同辐射率的空间辐射和无空间辐射时的温度分布情况,并绘制了最值温度节点的时间温度曲线,研究结果为相关芯片热设计提供了重要的理论依据.