分段滤波用于消除脉搏血氧检测中多种运动干扰的研究

脉搏血氧饱和度检测仪可以无损、实时地检测动脉血液中的含氧百分比,从而快速对人体的呼吸状况以及心肺功能作出判断,但其检测精度极易受到测试部位运动的影响.人体测试部位的运动大致可以分为突发性运动干扰以及周期性的运动干扰.突发性干扰表现在局部脉搏波的波形突变上,而周期性的干扰体现在多个局部脉搏波的波形的周期性变化上.文章有针对性地提出了一种将微分阈值分段与迭带中值滤波相结合的方法来剔除突发扰动的方法,并且在上诉方法上再加上一级多点移动平滑以消除周期性运动干扰.实验证明该方法在消除多种运动伪差上有着较好的效果,且该方法计算简单,易于实现,有着一定的实际应用价值.     

Evolution of concentration fluctuation during phase separation of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica

The influence of nanosilica on the concentration fluctuation of polystyrene/poly (vinyl methyl ether) (PS/PVME) mixtures was investigated during phase separation. The amplitude of concentration fluctuation was quantified by dielectric spectrums based on the idea of Lodge–Mcleish model and the linearized Cahn–Hilliard theory could describe the amplitude evolution of concentration fluctuation at the early stage of phase separation. Hydrophilic nanosilica A200 dispersed in PVME‐rich phase behaved an obvious inhibition effect on the concentration fluctuation of blend matrix, while hydrophobic nanosilica R974 dispersed in PS‐rich phase had little effect on the concentration fluctuation. The kinetics and amplitude evolution of concentration fluctuation during phase separation for PS/PVME/A200 nanocomposites were remarkably restrained due to the surface adsorption of PVME on A200. As the segmental dynamics of PVME and PS in homogeneous matrix was hardly influenced by A200 and R974, the enhanced miscibility and the significantly constrained flow relaxation of PVME chains might contribute to the retarded concentration fluctuation of PS/PVME/A200 nanocomposites. While the weak interaction between R974 and components of blend matrix and little effect of R974 on the molecular dynamics of PS chains may result in the weak retardation of concentration fluctuation for blend matrix. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1337–1349     

Synthesis of SnO_2 nanorods from aqueous solution:The effect of preparation conditions on the formed patterns

<正>SnO_2 nanorods were deposited on the Si substrates in an aqueous solution containing both SnCl_4 and CO(NH_2)_2.It is found that different self-assembled patterns of SnO_2 nanorods can be obtained by changing the deposition conditions such as the molar ratio of CO(NH_2)_2 to SnCl_4 and the pretreatment of the substrate.Scattered SnO_2 nanorods,for example,can be changed into flower-like patterns when the molar ratio of CO(NH_2)_2 to SnCl_4 is raised,and well-aligned nanorod arrays can be formed when the pretreatment of the substrate is changed.In addition,some interesting patterns,e.g.tree-like patterns,can also be observed.     

Fracture dynamics problem on mode I semi-infinite crack

By means of the theory of complex functions, fracture dynamics problems concerning mode I semi-infinite crack were studied. Analytical solutions of stress, displacement and dynamic stress intensity factor under the action of moving increasing loads Pt ³/x ³, Px ³/t ², respectively, are very easily obtained using the ways of self-similar functions. The correlative closed solutions are attained based on the Riemann–Hilbert problems.     

一类具有欧拉形式的中立型微分方程的振动性

研究具有欧拉形式的无界时滞中立型微分方程解的振动性，给出了方程振动的几个充分条件。     

Non-contact evaluation of the resonant frequency of a microstructure using ultrasonic wave

This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.     

Influence of NH<Subscript>3</Subscript> flow rate on pyridine-like N content and NO electrocatalytic oxidation of N-doped multiwalled carbon nanotubes

Nitrogen-doped multiwalled carbon nanotubes (N-MWCNTs) have been prepared by pyrolysis of pyridine and iron phthalocyanine over an iron catalyst at 850 °C at various ammonia gas (NH₃) flow rates. X-ray photoelectron spectroscopy results reveal that the pyridine-like nitrogen (N) content can be controlled by changing the flow rate of NH₃, and that pyridine-like N plays an important role: it can increase the electrocatalytic activity and the rate of nitric oxide (NO) electrooxidation and decrease the activation energy of NO electrooxidation. Cyclic voltammetry results demonstrate that the N-MWCNTs sample grown with 200 mL/min NH₃ flow has the maximum N content of 3.22 atomic %, and its content of pyridine-like N that is chemically active is also the highest among all the N-MWCNTs samples. Electrochemical impedance spectroscopy results indicate that two-step electron transfer process occurs at the N-MWCNT-modified electrode, and the control step is different in various potential regions. The stability of NO electrooxidation at the N-MWCNT-modified electrode is examined, and the reaction mechanism is discussed.