基于随机相位调制的数字全息相移量提取方法

提出了一种在相移数字全息中提取相移角的方法.该方法通过在相移数字全息中引入随机相位板对物光波的相位进行调制,使得物光波在全息面上的相位分布成为近似理想的随机分布,进而根据这种随机分布的统计性质对相移角进行提取.计算机模拟结果表明,该方法提取出的相移角与设定的相移角之间的相对误差小于千分之一.同时,经过对比采用随机相位板和不采用随机相位板的计算结果发现,物体衍射光波在全息面上的相位分布具有一定的相关性.     

An improved method for assay of vitamin C in fish feed and tissues

Summary A method was devised to assay four forms of vitamin C: L-ascorbic acid (AA), dehydroascorbic acid (DHA), ascorbate-2-mono- and polyphosphate (AMP, APP), as well as ascorbate-2-monosulphate (AMS), in sample series of different fish tissues and feed. Direct and indirect detection were combined. Sample extractions were carried out with 0.2 mol L⁻¹ sodium acetate buffer (pH 4.8) and extracts were deproteinized after different chemical or enzymatic reactions, with perchloric acid. The DHA was reduced to AA with dithioerythritol (DTE). Ascorbate oxidase enzyme was used for the detection of background and an acidic phosphatase enzyme for the hydrolysis of different phosphate esters. Ascorbate-2-sulphate was detected directly with help of coinjection of the compound. Chromatographic analysis was carried out with a single column isocratic reverse phase method. The mobile phase was an aqueous buffer of 0.04 M sodium-acetate, 0.05 mM EDTA, 0.5 mM tetrabutylammonium dihydrogen phosphate (TBA) adjusted to pH 3.76 with 85% H₃PO₄ and with 24 mL methanol added to 1000 mL. C-18 columns were used with 0.6 mL min⁻¹ flow rate at 23°C. The vitamin C forms were detected by UV absorption at 250 nm. The determination limit was 1.0–5.0 μg g⁻¹ in AA equivalent. The standard deviations were between 1–6% and depended on the concentrations of vitamin C forms and tissues. Recoveries were between 90–96% in samples. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

New type of spherical pore Al alloy foam with low porosity and high strength

The Ultra Light Metal Structure with variouskinds of pores (open, close) realizes the lightness andmultifunction of structural material. The functionsinclude lightness (ρ < 1), high specific strength, highenergy absorption, sound insulation, heat insulationand electromagnetism shield. It is one of the hotspotsin material research nowadays[1— . The requirements 6]of high speed movement and high technology make Alalloy foam, which has higher specific st…     

Structural evolution of poly(lactic acid) upon uniaxial stretching investigated by in situ infrared spectroscopy

Structural evolution of poly(lactic acid) (PLA) upon uniaxial stretching was studied with in-situ polarized infrared spectroscopy measurements, and its structural change affected by annealing was also investigated. Band shifting was used to reflect the structural ordering process. It was found that the band at 1302 cm⁻¹ always moves to low wavenumbers before crystallization, indicating the occurrence of intermolecular packing ordering. However, the band at 869 cm⁻¹ shifts to high wavenumbers, which is related to the transition from the amorphous phase to the ordered phase. Interestingly, during stretching, the shifting for the band at 1302 cm⁻¹ always occurs before that for the lower wavenumber band, whereas these two band shifts take place simultaneously under annealing. Based on the different characteristics of the structural evolution under stretching and annealing processes, a critical temperature was found at around 63 °C, which influences the effect weight of kinetic and thermodynamic factors to the crystallization behavior. The effect of the drawing temperature on crystallization and mechanical property of PLA films was also analyzed.     

Experimental line broadening and line shift coefficients of the acetylene ν1 + ν3 band pressurized by hydrogen and deuterium and comparison with calculations

Theoretical and experimental values have been determined for the pressure broadening of the ν₁ + ν₃ band of acetylene by hydrogen and deuterium at 195 K, and experimental values of the pressure shifts have been determined. Theoretical values have been calculated on the basis of a recent potential energy surface using the close coupling scheme. We discuss the detailed contribution of the various rotational angular momenta of the perturbing gas and the ortho and para contribution to the total pressure broadening cross-sections. We give routes to circumvent the computational cost of such calculations. Experimental values have been measured using a tunable diode laser spectrometer assuming a Voigt line shape. These pressure broadening parameters are compared with measurements performed recently at room temperature and with present measurements performed at 195 K in the ν₁ + ν₃ band of acetylene. A satisfactory agreement is obtained with the present results and available ones at 295 K.     

Fourier transform profilometry based on composite structured light pattern

In Fourier transform profilometry (FTP), the zero frequency of the imaged patterns will influence the measurement range and precision. The π phase shifting technique is usually used to eliminate the zero order component, but this method requires the capture of two fringe patterns with a π phase difference between them, which will impede the real time application of the method. In this paper, a novel method is proposed, in which a composite structured light pattern is projected onto the object. The composite structured light pattern is formed by modulating two separate fringe patterns with a π phase difference along the orthogonal direction of the two distinct carrier frequencies. This method can eliminate the zero frequency by using only one fringe pattern. Experiments show that there is no decrease in the precision of this novel method compared with the traditional π phase shifting technique.     

无相移滤波技术用于分析化学信号处理

把无相移滤波技术引入了分析化学信号处理领域。其方法为：先将输入序列按顺序滤波，然后将所得结果逆转后反向通过滤波器，再将所得结果逆转后输出。通过对色谱信号的实验研究表明，与普通的数字滤波方法相比较，无相移滤波不但具有普通数字滤波的优点，而且不会产生滤波前后的相位偏移，具有良好的应用前景，尤其对于需要准确计算保留时间的场合，用此预处理方法非常适合。     

Comparative analysis of phase extraction methods based on phase-stepping and shifting curve in grating interferometry

Two phase extraction methods which are based separately on phase-stepping and shifting curve are mainly used in phase-sensitive imaging in gating interferometry to determine the x-ray phase shift induced by an object in the beam. In this paper, the authors perform a full comparative analysis and present the main virtues and limitations of these two methods according to the theoretical analysis of the grating interferometry.     

两步相移实现投影栅相位测量轮廓术

提出一种新的投影栅相位测量方法--两步相移法。该方法只需两幅相移条纹图，因此计算量小，速度快。给出了实验及计算结果，并同四步相移法进行了比较，证明了该方法具有较高的精度。