煤粉在高温空气中着火前后孔隙结构的变化

在高温空气点火试验台上,采用不同温度的高温热空气对处于高速湍流流动的烟煤煤粉气流进行快速加热,以模拟煤粉气流在电站锅炉炉膛内受热升温以及初期着火燃烧过程。在煤粉气流发生均相着火前后过程中,对其中不同粒径煤粉的孔隙结构及其比表面积随热风温度的升高而产生的变化进行了试验研究。结果表明,煤粉颗粒孔隙主要受热变形和挥发分析出2方面的影响,产生截然相反的2种变化趋势。由于不同粒径煤粉颗粒传热特性的差异,当粒径较大且热风温度较低时,其孔隙结构的变化以热变形的影响为主,孔隙产生闭合;当粒径较小且热风温度较高时,则挥发分析出的影响占优,孔隙出现增长。随着热风温度的升高,小于3 nm的孔隙随挥发分析出的加剧而急剧增加。     

Face recognition using illuminant locality preserving projections

A novel supervised manifold learning method was proposed to realize high-accuracy face recognition under varying illuminant conditions.The proposed method,named illuminant locality preserving projections(ILPP),exploited illuminant directions to alleviate the effect of illumination variations on face recognition.The face images were first projected into low-dimensional subspace.Then the ILPP translated the face images along specific direction to reduce lighting variations in the face.The ILPP reduced the distance between face images of the same class,while increase the distance between face images of different classes.This proposed method was derived from the locality preserving projections(LPP)methods,and was designed to handle face images with various illuminations.It preserved the face image’s local structure in low-dimensional subspace.The ILPP method was compared with LPP and discriminant locality preserving projections(DLPP),based on the YaleB face database.Experimental results showed the effectiveness of the proposed algorithm on the face recognition with various illuminations.     

Characterization of epitaxial GaAs MOS capacitors using atomic layer-deposited TiO2/Al2O3 gate stack: study of Ge auto-doping and p-type Zn doping

ABSTRACT: Electrical and physical properties of a metal-oxide-semiconductor [MOS] structure using atomic layer-deposited high-k dielectrics (TiO2/Al2O3) and epitaxial GaAs [epi-GaAs] grown on Ge(100) substrates have been investigated. The epi-GaAs, either undoped or Zn-doped, was grown using metal-organic chemical vapor deposition method at 620°C to 650°C. The diffusion of Ge atoms into epi-GaAs resulted in auto-doping, and therefore, an n-MOS behavior was observed for undoped and Zn-doped epi-GaAs with the doping concentration up to approximately 1017 cm-3. This is attributed to the diffusion of a significant amount of Ge atoms from the Ge substrate as confirmed by the simulation using SILVACO software and also from the secondary ion mass spectrometry analyses. The Zn-doped epi-GaAs with a doping concentration of approximately 1018 cm-3 converts the epi-GaAs layer into p-type since the Zn doping is relatively higher than the out-diffused Ge concentration. The capacitance-voltage characteristics show similar frequency dispersion and leakage current for n-type and p-type epi-GaAs layers with very low hysteresis voltage (approximately 10 mV).PACS: 81.15.Gh.     

P3HT : PCBM solar cells—The choice of source material

Bulk heterojunction solar cells based on P3HT : PCBM blend films are among the most intensively studied polymer solar cells. In spite of that, there is a huge variation of reported efficiencies in the literature, even for same device architectures and film preparation procedures. Here we investigated the influence of starting properties of P3HT and PCBM (different suppliers) on blend film morphology and device performance. We found that there was a strong dependence of the film morphology and device performance on the source of chemicals used. Both P3HT and PCBM affected the results, and higher nominal purity did not necessarily result in better device performance. The dependence of the film morphology and device performance on the properties of P3HT and PCBM is discussed in detail. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39776.     

Measurement of Enzymatic and Nonenzymatic Polyunsaturated Fatty Acid Oxidation Products in Plasma and Urine of Macular Degeneration Using LC-QTOF-MS/MS

Oxidized polyunsaturated fatty acids (PUFA) are associated to pathogenesis of diseases including cardiovascular and neurodegeneration. The novel products are not only biomarkers but also lipid mediators in gene regulation and signaling pathways. Herein, simultaneous quantitation of 28 products derived from nonenzymatic and enzymatic oxidation of PUFA i.e. 5-, 15-F_2t-isoprostanes, 7-, 17-F_2t-dihomo-isoprostanes, 7-, 17-F_2t-dihomo-isofurans, 5-, 8-, 18-F_3t-isoprostanes, 4-, 10-, 13-, 14-, 20-F_4t-neuroprostanes, 5-, 8-, 9-, 11-,12-, 15-, 20-HETE, 4-, 7-, 11-, 14-, 17-HDHA, RvE1, and NPD1 using LC-(ESI)-QTOF-MS/MS was developed. These products were measurable in a single sample and the analytical time was relative short (~15 min). Furthermore, we showed that the use of internal standards is a requisite to normalize matrix effects and preparation loss for the quantitation. Validation assays indicated the method to be robust for plasma and mid-stream urine sample analysis in particular from those of age-related macular degeneration subjects, where the accuracy of quantitation displayed good repeatability.     

Crystallization and chemi-crystallization of recycled photo-degraded polypropylene

Injection moulded bars have been made from virgin polypropylene and from blends containing recycled photo-degraded polypropylene, then subjected to further ultraviolet (UV) exposure. Crystallinity measurements have been made at different depths from the exposed surface using X-ray diffraction and differential scanning calorimetry. Strong evidence for chemi-crystallization is provided for the photo-degraded samples. The crystallinity results are interpreted in terms of molecular scission and photo-initiated molecular defects. Scission leads to greater crystallizability and accounts for the observed chemi-crystallization. Molecular defects inhibit crystallization and eventually limit chemi-crystallization, as observed with a blend containing 75% virgin material and 25% recycled photo-degraded polymer after further UV exposure.     

Between-Individual Comparisons in Performance Evaluation: A Perspective From Prospect Theory.

This article examines how between-individual comparisons influence performance evaluations in rating tasks. The authors demonstrated a systematic change in the perceived difference across ratees as a result of changing the way performance information is expressed. Study 1 found that perceived performance difference between 2 individuals was greater when their objective performance levels were presented with small numbers (e.g., absence rates of 2% vs. 5%) than when they were presented with large numbers (e.g., attendance rates of 98% vs. 95%). Extending this finding to situations involving trade-offs between multiple performance attributes across ratees, Study 2 showed that the relative preference for 1 ratee over another actually reversed when the presentation format of the performance information changed. The authors draw upon prospect theory (D. Kahneman & A. Tversky, 1979; A. Tversky & D. Kahneman, 1981) to offer a theoretical framework describing the between-individual comparison aspect of performance evaluation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effective-index method with built-in perturbation correction forthe vector modes of rectangular-core optical waveguides

The effective-index method (EIM) with built-in perturbation correction is developed for the analysis of the vector modes of general rectangular-core optical waveguides. This method maintains the simplicity and the high efficiency of the conventional EIM, yet produces significantly more accurate results. Numerical examples for a wide range of waveguides are presented to demonstrate the accuracy of the method for the calculation of the propagation constants and the modal birefringence     

A two-step deep learning approach to data classification and modeling and a demonstration on subject type relationship analysis in the Web of Science

Scientometrics - It is common sense that some subjects have strong relationships while others are perhaps almost mutually independent, but a quantitative and systematic approach to describe such...