Pulverized coal swirl flames in oxy-fuel conditions: Effects of oxidizer O2 concentration on flow field and local gas composition

In an experimental study the effects of varied oxygen concentrations in the oxidizer gas on resulting flow fields, combustion products and general behavior of pulverized coal swirl flames under oxy-fuel conditions have been investigated. Experiments were carried out in a small scale down-fired cylindrical combustion chamber equipped with an annular swirl burner. Studied flames had a constant power output of 40 kW_th and O₂/CO₂ oxidizer gas mixtures with O₂ concentrations ranging from 23 to 33 vol%. Detailed two-dimensional flow field measurements are obtained from laser Doppler anemometry (LDA). Velocity profiles (Mean and RMS) have been obtained for all conditions investigated and serve as basis for identification of flow field characteristics. Velocity RMS values are provided as supplementary material. To complement flow field measurements, in-flame gas composition measurements were also conducted using a sampling probe combined with infrared gas absorption analysis via Fourier-transform infrared (FTIR) spectrometry. The results obtained show increased velocities, particularly along the main vortex for flames with increased oxygen contents, while lower velocities are found to occur inside the recirculation regions. The opposite occurs with lower O₂ concentrations, showing significantly reduced velocities in the main vortex, but stronger recirculation than the high oxygen counterparts. This effect is attributed to a modification of the swirl level introduced by the expansion of product gases. Measured NO and CO in-flame concentrations showed significant variations under different O₂ concentrations in the oxidizer.     

Analysis of questioned documents: A review

During the last years (2000–2014), many publications concerning the forensic analysis of questioned documents have been published, and new techniques and methodologies are nowadays employed to overcome forensic caseworks. This article reviews a comprehensive collection of the works focused on this issue, including dating studies, the analysis of inks from pens and printers, the analysis of paper, the analysis of other samples related to questioned documents and studies on intersecting lines. These sections highlight the most relevant analytical studies by a wide range of analytical techniques. Separation and spectrometric techniques are critically discussed and compared, emphasizing the advantages and disadvantages of each one. Finally, concluding remarks on the research published are included.     

Flow measurements inside a heated multiple rotating cavity with axial throughflow

This paper discusses experimental results from a multiple cavity test rig representative of a high pressure compressor internal air system. Measurements of the axial, tangential and radial velocity components are presented. These were made using a two component, laser doppler anemometry (LDA) system for a range of non-dimensional parameters representative of engine conditions (Re up to 4 × 10⁶ and Re_z up to 1.8 × 10⁵). Tests were carried out for two different sizes of annular gap between the (non-rotating) drive shaft and the disc bores.

The axial and radial velocities inside the cavities are virtually zero. The size of the annular gap between disc bore and shaft has a significant effect on the radial distribution of tangential velocity. For the narrow annular gap (d_h/b = 0.092), there is an increase of non-dimensional tangential velocity V/Ωr with radial location from V/Ωr < 1 at the lower radii to solid body rotation V/Ωr = 1 further into the cavity. For the wider annular gap (d_h/b = 0.164), there is a decrease from V/Ωr > 1 at the lower radii to solid body rotation further into the cavity. An analysis of the frequency spectrum obtained from the tangential velocity measurements is consistent with a flow structure in the r– plane consisting of pairs of contra rotating vortices.     

Écoulement turbulent dans une cavité rotor–stator fermée de grand rapport d'aspect

A direct numerical simulation is combined with laboratory study to describe the turbulent flow in an annular high speed rotor–stator cavity. Comparisons are made for a turbulent flow characterized by a Reynolds number $\mathit{Re}=\Omega R_2^2/\nu =9.5\times {10}^4$ in a shrouded cavity of large aspect ratio $G=(R_2?R_1)/h=18.32$, where $R_1$ and $R_2$ are the inner and outer radii of the rotating disk, and h is the inter-disk space. A close agreement is found between the computed results and the experimental data for the mean and turbulent fields.? To cite this article: S. Poncet, A. Randriamampianina, C. R. Mecanique 333 (2005).     

二极管激光阵列波长光束组合实现20W输出

基于波长光束组合(WBC)技术,利用光栅衍射和外腔反馈,将二极管激光阵列(LDA)发光单元锁定在不同的波长上,以近似平行光束沿光栅的-1级衍射方向组合输出,改善LDA输出光束质量.实验中采用发光单元宽度为100μm、周期为500μm及由19个单元构成的l cm普通商用LDA,在连续运行最大注入电流为60.6A、自由运转输出功率为49.8 W时,获得功率为20.1 W的组合光束稳定输出,其光谱宽度为15 mm,对应的远场发散角由约70 mrad变为1.66 mrad,改善后的光束质量因子M2x.y约为32,与单个发光单元的光束质量相当.     

Face recognition using message passing based clustering method

Traditional subspace analysis methods are inefficient and tend to be affected by noise as they compare the test image to all training images, especifically when there are large numbers of training images. To solve such problem, we propose a fast face recognition (FR) technique called APLDA by combining a novel clustering method affinity propagation (AP) with linear discriminant analysis (LDA). By using AP on the reduced features derived from LDA, a representative face image for each subject can be reached. Thus, our APLDA uses only the representative images rather than all training images for identification. Obviously, APLDA is much more computationally efficient than Fisherface. Also, unlike Fisherface who uses pattern classifier for identification, APLDA performs the identification using AP once again to cluster the test image into one of the representative images. Experimental results also indicate that APLDA outperforms Fisherface in terms of recognition rate.     

Multivariate statistical analysis of tobacco of different origin, grade and variety according to polyphenols and organic acids

The aim of this work was to determine the concentration of polyphenols, organic acids in tobacco of different areas, grades and varieties by ultra-performance liquid chromatography tandem mass spectrometry (UPLC/MS/MS) and to achieve statistical classification by principal component analysis (PCA) and linear discriminant analysis (LDA). The obtained results revealed that tobacco of different varieties can be correctly classified according to the contents of polyphenols or organic acid. The results of PCA showed that different grades and geographic regions cannot completely be discriminated using polyphenols or organic acid as independent variables. However, there were marked differences in special class from the same type or grade tobacco. At the same time, the results of LDA also showed that the samples were correctly classified at 100% for different varieties of tobacco, but only 55.3% and 60% for different grades and areas, respectively. These results demonstrated that the composition of polyphenols and organic acids can be used as the useful variables to characterize the type and the special class or grade of tobacco.     

33 W半导体激光器列阵光纤耦合模块

利用光纤柱透镜和光束转换装置压缩半导体激光器列阵（LDA）的发散角，然后通过聚焦透镜将激光束耦合入芯径为400μm的微球透镜光纤。LDA与光纤耦合输出后，实现33W的高出纤功率，最高耦合效率大于80％，光纤的数值孔径（NA）为0．22。