波数线性校正方法在多烯烃和类胡萝卜素Raman光谱频率校正中的应用

采用密度泛函理论计算了两种类胡萝卜素(β-胡萝卜素和叶黄素) 和几种短链(n=2~5)多烯烃的Raman光谱,用波数线性校正(WLS)方法对计算频率进行了校正,并与常用的几种校正方法作了比较。最常用的单一参数校正(UFS)方法只适用于个别频率的校正,对于所有振动频率的综合校正效果并不理想。WLS方法对于多烯烃和类胡萝卜素的校正结果明显优于UFS方法,校正公式分别为ν_obs／ν_calc=0.999 9-0.000 027 4ν_calc和ν_obs／ν_calc=0.993 8-0.000 024 8ν_calc,这些结果说明WLS方法可以用于类胡萝卜素这样的大分子的频率校正。WLS方法对多烯烃和类胡萝卜素的校正参数非常接近,证明WLS方法对多烯烃的校正结果可以用于类胡萝卜素的频率校正,这为类胡萝卜素频率校正提供了一种新的方法。     

多壁纳米碳管的频率上转换效应研究

实验上测量了多壁纳米碳管的吸收光谱和光致发光谱,观察到了多壁纳米碳管的光频率上转换效应,激发波长为1064 nm,发射光谱为带状光谱,峰值波长为780 nm.由吸收光谱上观察到了纳米碳管的态密度分布的范霍夫奇点,这些奇点对应的吸收峰位置为685nm,719nm和894nm.上转换过程是纳米碳管的电子经双光子吸收,再经无辐射跃迁布居在范霍夫奇点,最后经辐射跃迁而产生荧光.     

Frequency Reliability-Based Robust Design of the Suspension Device of a Jarring Machine with Arbitrary Distribution Parameters

The frequency reliability with arbitrary distribution parameters in the stochastic dynamic structure system of practical engineering and its related theories were studied deeply in the paper. The frequency reliability method of avoiding resonance was proposed by mechanical dynamics, stochastic finite element method, and reliability theory. Then the frequency reliability formula with arbitrary distribution parameters was deduced through Edgeworth series method. Furthermore, the frequency reliability sensitivity method was presented based on the frequency reliability research, which provided a preliminary efficient way to analyze how each random parameter contributed to the system reliability. Moreover, the frequency reliability-based robust design method of the stochastic dynamic structure system was obtained by robust and optimization technology on the basis of frequency reliability and sensitivity method, which helped designers to establish acceptable parameter values and to determine the fluctuations of the parameters for the safe operations. Meanwhile, a numerical example of the suspension device of a jarring machine with arbitrary distribution parameters was provided and studied, the numerical results were in agreement with practice, which demonstrated the efficiency and accuracy of the proposed methods.     

Frequency stabilization of a frequency-doubled 197.2 THz distributed feedback diode laser on rubidium 5S1/2→7S1/2 two-photon transitions

A 197.2 THz (1520.2 nm) ITU-T grid distributed feedback (DFB) diode laser is frequency stabilized at 197.198 THz by 1ocking its second harmonic (SH) signal on the rubidium 5S_1/2→7S_1/2 two-photon transition at 394.396 THz (760.1 nm). With 100 mW from the DFB diode laser and amplifying by an erbium-doped fiber amplifier, we obtain an SH power of 15 mW using a periodically poled lithium niobate (PPLN) waveguide frequency doubler. The stability was 2×10⁻¹¹ (10 s), corresponding to a frequency variation of 4 kHz at 1520.2 nm. Our scheme provides a compact and high performance frequency reference in the communication band.     

Gender differences in children's intonational patterns

This study investigated differences among intonational variables in prepubescent girls' and boys' voices in conversational speech (American-English). Subjects were middle class boys and girls at each of four age levels: 3–4, 5–6, 7–8, and 9–10 years. Samples of conversational speech were recorded and acoustically analyzed for minimum and maximum FO, mean FO, and SD of FO (FOSD), as well as number and direction of FO changes (“shifts”) per utterance. Findings indicated that the mean FO of the males decreased at around age 7–8 years. Additionally, maximum FO, range, and percentage of rising and falling shifts all showed decreases for the males starting at ages 7–8 not paralleled by decreases for the females. Both physiological and sociocultural factors appear to account for the changes that mark the development of intonational patterns in prepubertal girls and boys.     

Frequency and Polarization Transformer: Longitudinal Modes

A frequency transformer that converts an elliptically polarized standing wave into frequency-shifted circularly polarized standing waves is considered. The transformer is a one-dimensional cavity in which a magnetoplasma, that supports longitudinal modes, is created. Theoretical derivation for the case of sudden and uniform creation of the magnetoplasma is given. Finite-Difference Time-Domain (FDTD) technique is developed to numerically simulate the problem. The simulation is used to verify the results of the theory as well as obtain results for the cases of creation of a lossy magnetoplasma with arbitrary space and time profile of the electron density. A few instructive results are presented as graphs to illustrate the effects of source parameters and system parameters.     

Fundamental aspects of contactless conductivity detection for capillary electrophoresis. Part I: Frequency behavior and cell geometry

A better understanding of the characteristics of the axial contactless conductivity cell could be obtained by carefully studying the effect of the cell geometry on its frequency behavior. A good fit between theoretical and experimental results shows that the axial contactless conductometric detector can effectively be described by the simplest possible equivalent circuitry consisting of a capacitor, resistor, and a second capacitor. The cell constant is largely defined by the length of the gap between the electrodes. The effective electrode size is thus not related to the dimensions of the real electrodes but more closely to the cross-sectional area of the internal diameter of the capillary. Typical experimental values of 20 MOmega and 0.1 pF were obtained for the resistance and capacitances, respectively, of a cell formed by a 2 mm gap between two 4 mm long electrodes fitted with a capillary of 50 microm ID. It could be shown that the diameter of the electrode is not critical and tight coupling of the electrodes to the outer wall of the capillary is not needed. The peak overshoot phenomenon, which has frequently been reported, is an artefact that can be minimized by optimizing the frequency for cell excitation. The frequency setting has to be optimized for each cell design, operational amplifier, electrolyte solution and capillary.     

Far infrared laser lines and assignments of CH3OH: a review

Methyl alcohol is the most important lasing molecule in the Far-Infrared (FIR) spectral region, and the most widely used for investigation and for applications. Since the last critical review of 1984, over seventy papers have been published dealing with the FIR laser lines and the infrared spectroscopy of CH₃OH. In 1984 we could list about 330 FIR laser lines, 98 of which were measured in frequency and 105 assigned. Since then more than 70 papers were published increasing the number of the known laser lines to 575 (103 measured in frequency). Also the FIR and IR spectroscopy was largely improved thanks to the analysis of high resolution FT spectra, and the number of the correctly assigned laser lines has been increased to 224. The wavenumbers of the assigned lines can now be predicted with an accuracy of about 0.001 cm^–1 or better, thus approaching the accuracy of the experimental frequency measurements.     

Comments on “Spectral analysis of thermally stimulated exoelectron emission from glass deposited on metal by argon plasma treatment”

A “spectral analysis” using a fit of a single glow curve only — without kinetic check — does not prove the correctness of the model of Sakurai and Momose [Phys. Lett. A 179 (1993) 55] and thus of parameters estimated on this basis. Contrary to this a “complete analysis” yields three of four parameters directly from the experiment. Two criteria are given to verify the model experimentally.     

探测光功率对半导体全光波长变换器性能的影响分析

根据半导体光放大器的高频滤波效应,利用动态载流子恢复时间的概念,分析了基于半导体光放大器交叉增益调制的全光波长变换器中变换信号的波形、啁啾与探测光功率的关系。理论计算表明,在保持变换信号消光比相同的情况下,在大的探测光功率下,变换信号的波形将变好,并且啁啾对变换信号码间干扰的影响会减小,理论很好地解释了文献中的实验结果。