脉冲噪声环境下基于分数低阶循环相关的MUSIC算法

该文以稳定分布作为噪声模型,研究了脉冲噪声环境下循环平稳信号的波达方向估计问题。针对在脉冲噪声环境中基于传统2阶循环相关的算法效果显著退化的问题,该文提出了基于分数低阶循环相关的分数低阶循环MUSIC算法(FLOCC-MUSIC)。将分数低阶循环相关与MUSIC算法相结合,可以有效抑制脉冲噪声的同频带干扰。计算机仿真表明了此算法可有效完成高斯噪声和脉冲噪声条件下的波达方向估计,其性能优于传统的基于2阶循环相关的Cyclic-MUSIC。     

Centering of organic-inorganic hybrid liposomal cerasomes in electrospun gelatin nanofibers

A study investigating the embedding of stabilized organic-inorganic liposomal cerasomes in gelatin nanofibers through the electrospinning of cerasome-dispersed gelatin aqueous solution is presented. Fluorescent and transmission electron microscopy confirm the embedding and centering of cerasomes in the electrospun nanofibers. A simple mechanism is proposed for the centering of cerasomes in gelatin nanofibers. The ability to incorporate cerasomes capable of encapsulating a variety of bioactive molecules provides a promising method to functionalize polymer nanofibers.     

负载限流控制全桥软开关变换器的研制

本文介绍了负载限流控制全桥软开关变换器,包括全桥软开关变换器电路结构和过载限流的工作原理,并阐述了如何实现副边整流桥的尖峰电压抑制。在理论分析的基础上,介绍了电路设计,研制了1台样机,并进行实验验证。     

Novel determination of caffeine in human urine by direct analysis in real time mass spectrometry

Determination of caffeine is necessary for clinical research. A new method for the determination of caffeine in human urine was established by direct analysis in real time mass spectrometry using multiple reaction monitoring. The m/z 195.1 to 138.1 amu transition was employed in positive ionization mode. The preparation and analysis conditions were systemically optimized. The calibration curve was linear from 0.5–50 µg/mL with a limit of detection limit of 0.2 µg/mL. Intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all concentrations. Moreover, the matrix effects for the determination of caffeine were evaluated. In conclusion, a simple, rapid, and reliable method without complex sample preparation and chromatographic separation was developed and validated for the determination of caffeine in human urine.     

Electrostatic Control of Structure in Self‐Assembled Membranes

Self‐assembling peptide amphiphiles (PAs) can form hierarchically ordered membranes when brought in contact with aqueous polyelectrolytes of the opposite charge by rapidly creating a diffusion barrier composed of filamentous nanostructures parallel to the plane of the incipient membrane. Following this event, osmotic forces and charge complexation template nanofiber growth perpendicular to the plane of the membrane in a dynamic self‐assembly process. In this work, we show that this hierarchical structure requires massive interfacial aggregation of PA molecules, suggesting the importance of rapid diffusion barrier formation. Strong PA aggregation is induced here through the use of heparin‐binding PAs with heparin and also with polyelectrolytes of varying charge density. Small angle X‐ray scattering shows that in the case of weak PA‐polyelectrolyte interaction, membranes formed display a cubic phase ordering on the nanoscale that likely results from clusters of PA nanostructures surrounded by polyelectrolyte chains.     

Dynamic rheological behavior of reactively compatibilized polypropylene/polyamide 6 blending melts

The dynamic rheological behavior is measured by small amplitude oscillatory shear on rotational rheometer for polypropylene/polyamide 6 (PP/PA6) blends compatibilized by a polypropylene grafted maleic anhydride (PP‐g‐MAH). Scanning electron microscope (SEM) results show that the PP/PP‐g‐MAH/PA6 (=100/6/40wt) is sea‐island structure, the PP/PP‐g‐MAH/PA6 (=100/6/60wt) blend is semi‐cocontinuous. Coarse PA6 zones can be observed when the weight ratio is 100/6/80. At low frequency the complex viscosity, dynamic modulus of the PP/PP‐g‐MAH/PA6 (PP/PP‐g‐MAH = 100/6wt) blends first increase then drop with the increase of PA6 weight content in the range of 0–100, the maximum value arrives at the weight content of 60. The Cole–Cole plots as well as the weighted relaxation spectra of the blends have a main arc and a tail when the weight ratio of PP/PP‐g‐MAH/PA6 is in the range of 100/6/20–100/6/60, but have different shapes when the weight ratio increases to 100/6/80 and 100/6/100. The possible reason is the weight ratio of 100/6/80 and 100/6/100 is close to the phase inversion point. In fitting the storage modulus data at low frequency, Palierne's model with two parameters interfacial tension and interfacial shear modulus is better than Bousmina's model. Palierne's model with only one parameter of interfacial tension can not fit the data well. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42091.     

5083Al/1060Al/TA1/Ni/SUS304五层爆炸复合板退火组织演化及力学性能

为改善5083Al和304不锈钢爆炸焊接质量,提升隔热效果,本研究采用1060Al、TA1和Ni作夹层材料,制备了具有热传导梯度的五层爆炸复合板。为消除爆炸焊接后的残余应力,减少绝热剪切带和微裂纹等缺陷,采用550℃×60min退火工艺对五层爆炸复合板进行退火处理,并通过SEM、EBSD和万能试验机等手段,分析研究退火对其组织演化及力学性能的影响。结果表明：五层爆炸复合板的4个焊接界面均呈波形,且在界面处存在微裂纹、孔洞、绝热剪切带和漩涡区等缺陷。经退火处理,4个焊接界面均发生不同程度的再结晶,微裂纹、绝热剪切带等缺陷得到有效改善;5083Al/1060Al/TA1界面的β相和Al-Ti金属间化合物增多,TA1/Ni界面在原TiNi₃熔化层的基础上新增TiNi熔化层和Ti₂Ni熔化层。界面抗拉剪强度均有所降低,但均仍远高于相应国标使用要求;拉脱试样在5083Al/1060Al界面断裂分离。     

Cell behaviors on surface of pure tantalum with nano-dimpled structure

Tantalum exhibits excellent biocompatibility and good chemical stability, which has been employed in dental and orthopedic applications.The local microenvironment of the surface of implants influence determines the surrounding cell responses.In this work, nano-dimpled structure on the surface of pure tantalum was fabricated by electrochemical anodization.The surface morphology of the nano-dimpled structure was observed, and the dimensions of the nano-dimpled structure were measured by scanning electron microscopy(SEM).The surface roughness of the sample with nano-dimpled structure was measured by atomic force microscopy(AFM).The results show that the diameter of nano-dimpled ranges from 40 to 180 nm, and the higher the applied voltage, the larger the diameter.Moreover, nano-dimpled structure has good hydrophilicity.In vitro results show that nano-dimpled structure can promote the adhesion and proliferation of mouse cranial anterior bone(MC-3T3-E1) cells.The filopodia of MC-3T3-E1 cells can be fully extended on this nano-dimpled structure.On the surface of the nano-dimpled structure with a dimple size of 40 nm, the cells have the longest aspect ratio.The small dimple size of the nanodimpled structure is beneficial to cell proliferation and osteogenic differentiation.