Low frequency limits of third-order harmonic coefficients for atomic hydrogen in any level of discrete energy spectrum

In this paper the analytical expression is derived for the third-order optical harmonic coefficients x _abcd ^v (,,) of the atomic hydrogen at very low frequencies 0 in many level of the discrete energy spectrum.The author expresses his thank to Prof. Nguyen Van Hieu for suggesting the problem and fruitful discussions.     

A Dynamic Anomaly Detection Approach Based on Permutation Entropy for Predicting Aging-Related Failures

Software aging is a phenomenon referring to the performance degradation of a long-running software system. This phenomenon is an accumulative process during execution, which will gradually lead the system from a normal state to a failure-prone state. It is a crucial challenge for system reliability to predict the Aging-Related Failures (ARFs) accurately. In this paper, permutation entropy (PE) is modified to Multidimensional Multi-scale Permutation Entropy (MMPE) as a novel aging indicator to detect performance anomalies, since MMPE is sensitive to dynamic state changes. An experiment is set on the distributed database system Voldemort, and MMPE is calculated based on the collected performance metrics during execution. Finally, based on MMPE, a failure prediction model using the machine learning method to reveal the anomalies is presented, which can predict failures with high accuracy.     

Preparation and Characterization of an Organic/Inorganic Composite Based on Ferrospinel with Poly(Methyl Methacrylate) and Polyaniline

A novel organic/inorganic composite based on LiNi–ferrospinel with poly(methyl methacrylate) (PMMA) and polyaniline (PANI), PANI/PMMA/LiNi_0.5Fe₂O₄ composite, was synthesized via a facile in-situ polymerization process. The structures of the resulting samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy. The optical and thermal properties of the PANI/PMMA/LiNi_0.5Fe₂O₄ composite were studied by fluorescent spectroscopy and thermogravimetry analysis. It was indicated that the existence of LiNi_0.5Fe₂O₄ (LFNO) in the PANI/PMMA/LFNO composite resulted in changes in the fluorescence spectra. The as-obtained composite may have potential for electrical and electromagnetic applications in antistatic materials, electromagnetic shields, radar absorbers, and so forth.     

Analysis of retroreflector-introduced spectrum distortion in birefringent crystal-based interleaver filters

Spectrum distortion in a birefringent crystal-based interleaver filter introduced by the right-angle total internal reflection retroreflector is studied. The phase shift between two perpendicularly polarized components of the polarized light incident onto the retroreflector is calculated. The sensitivity of the phase shift to the incident angle for different materials from which the retroreflector is made is also considered. This study indicates that the phase shift is less sensitive to the incident angle for retroreflectors having a higher index of refraction, suggesting a fixed-phase compensator that can be used to cancel out the phase shift introduced by the retroreflector to recover the interleaver filter's spectrum. The fold-back 50 GHz channel spacing birefringent crystal interleaver filter is fabricated to demonstrate that the spectrum distortion due to the phase shift introduced by retroreflector can be eliminated by a phase compensator.     

Conical bubble photoluminescence from rhodamine 6G in 1, 2-propanediol

A modified U-tube conical bubble sonoluminescence device is used to study the conical bubble photoluminescence. The spectra of conical bubble sonoluminescence at different concentrations of rhodamine 6G (Rh6G) solution in 1,2-propanediol have been measured. Results show that the sonoluminescence from the conical bubbles can directly excite Rh6G, which in turn can fluoresce. The light emission of this kind is referred to as conical bubble photoluminescence. The maximum of fluorescence spectral line intensity in the conical bubble photoluminescence has a red shift in relative to that of the standard photo-excited fluorescence, which is due to the higher self-absorption of Rh6G, and the spectral line of conical bubble photoluminescence is broadened in width compared with that of photo-excited fluorescence.     

Contracting on Average Random IFS with Repelling Fixed Point

We consider random iterated function systems which consist of strictly increasing and (not necessarily strictly) convex functions on a compact interval or on a half line. We assume that the system is contracting on average in a sense which is wide enough to permit the existence of a common fixpoint at which some functions of the system are expanding and perhaps none of them are contracting (see Fig. 1). We prove that the Hausdorff dimension of any of the possibly uncountably many invariant measures is smaller than or equal to the accumulated entropy divided by the Liapunov exponent. Mathematics Subject Classification. Primary 42A85 Secondary 11R06; 26A46; 26A30; 26A78; 28A80     

Synthesis of Polyaniline Submicrometer-Sized Tubes with Controllable Morphology

Polyaniline submicrometer-sized tubes with controllable morphology have been synthesized by chemical oxidative polymerization of aniline with the aid of sodium dodecylbenzenesulfonate. The products were characterized by field-emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy, respectively. The effects of the concentrations of sodium dodecylbenzenesulfonate, reaction temperatures and growth conditions on the morphologies of polyaniline submicrometer-sized tubes have been investigated.     

Diffusion tensor parameters and principal eigenvector coherence: Relation to b-value intervals and field strength

Diffusion-weighted MRI images acquired at b-value greater than 1000 s mm^− 2 measure the diffusion of a restricted pool of water molecules. High b-value images are accompanied by a reduction in signal-to-noise ratio (SNR) due to the application of large diffusion gradients. By fitting the diffusion tensor model to data acquired at incremental b-value intervals, we determined the effect of SNR on tensor parameters in normal human brains, in vivo. In addition, we also investigated the impact of field strength on the diffusion tensor model. Data were acquired at 1.5 and 3 T, at b-values 0, 1000, 2000 and 3000 s mm^− 2 in twenty diffusion-sensitised directions. Fractional anisotropy (FA), mean diffusivity (MD) and principal eigenvector coherence (κ) were calculated from diffusion tensors fitted between datasets with b-values 0–1000, 0–2000, 0–3000, 1000–2000 and 2000–3000 s mm^− 2. Field strength and b-value effects on diffusion parameters were analysed in white and grey matter regions of interest. Decreases in FA, κ and MD were found with increasing b-value in white matter. Univariate analysis showed a significant increase in FA with increasing field strength in highly organised white matter. These results suggest there are significant differences in diffusion parameters at 1.5 and 3 T and that the optimal results, in terms of the highest values of FA in white matter, are obtained at 3 T with a maximum b = 1000 s mm^− 2.     

空温式翅片管气化器非稳态结霜速率分析

观测了某实际运营的空温式翅片管气化器附近湿空气流动状态。基于热力学理论和湿空气流动状态建立了空温式翅片管气化器表面非稳态结霜模型,推导了非稳态结霜速率的关系式,分析了不同工况下非稳态结霜速率影响因素。非稳态结霜速率随湿空气温度、相对湿度和气流速度增加而增加,其主要影响因素为湿空气温度和相对湿度,而气流速度影响相对较小。非稳态结霜速率分析为精确计算空温式翅片管气化器传热特性提供了一定理论依据。     

基于FPGA的DDS设计方法

介绍了一种基于FPGA的DDS设计方法,结合DDS的原理,给出了具体设计程序以及仿真波形。基于FPGA的DDS与传统的专业DDS芯片相比具有电路简单、输出波形调整灵活以及性价比高等特点。