Chromium speciation in coal and biomass co-combustion products

Chromium speciation is vital for the toxicity of products resulting from co-combustion of coal and biomass. Therefore, understanding of formation processes has been studied using a combination of X-ray absorption fine structure (XAFS) spectroscopy and thermodynamic equilibrium calculations. The influence of cofiring on Cr speciation is very dependent on the type of fuel. Cr(VI) contents in the investigated fly ash samples from coal and cofiring average around 7% of the total chromium. An exception is cofiring 7-28% wood for which ashes exhibited Cr(VI) concentrations of 12-16% of the total chromium. Measurements are in line with thermodynamic predictions: RE factors of Cr around 1 are in line with volatile Cr only above 1400 °C; lower Cr(VI) concentrations with lower oxygen content and Cr(III) dissolved in aluminosilicate glass. Stability of Cr(VI) below 700 °C does not correlate with Cr(VI) concentrations found in the combustion products. It is indicated that Cr(VI) formation is a high-temperature process dependent on Cr evaporation (mode of occurrence in fuel, promoted by organic association), oxidation (local oxygen content), and formation of solid chromates (promoted by presence of free lime (CaO) in the ash). CaCrO(4)(s) is a probable chemical form but, given different leachable fractions (varying from 25 to 100%), different forms of Cr(VI) must be present. Clay-bound Cr is likely to dissolve in the aluminosilicate glass phase during melting of the clay.     

自适应平台直方图高动态范围红外图像显示方法

针对不同场景高动态范围红外图像的自适应显示方法问题,提出了一种基于图像分割的自适应平台直方图显示方法,首先进行图像分割,再根据分割结果讨论平台阈值的选取,并分析了平台阈值的选取依据。试验结果表明本文方法对不同场景均获得了良好显示效果,具备实用性。     

Searching General Sufficient‐and‐Necessary Conditions for Ultrafast Hydrogen‐Evolving Electrocatalysis

The development of cost‐effective and high‐performance electrocatalysts for the hydrogen evolution reaction (HER) is one critical step toward successful transition into a sustainable green energy era. Different from previous design strategies based on single parameter, here the necessary and sufficient conditions are proposed to develop bulk non‐noble metal oxides which are generally considered inactive toward HER in alkaline solutions: i) multiple active sites for different reaction intermediates and ii) a short reaction path created by ordered distribution and appropriate numbers of these active sites. Computational studies predict that a synergistic interplay between the ordered oxygen vacancies (at pyramidal high‐spin Co³⁺ sites) and the O 2p ligand holes (OLH; at metallic octahedral intermediate‐spin Co⁴⁺ sites) in RBaCo₂O_5.5+δ (δ = 1/4; R = lanthanides) can produce a near‐ideal HER reaction path to adsorb H₂O and release H₂, respectively. Experimentally, the as‐synthesized (Gd_0.5La_0.5)BaCo₂O_5.75 outperforms the state‐of‐the‐art Pt/C catalyst in many aspects. The proof‐of‐concept results reveal that the simultaneous possession of ordered oxygen vacancies and an appropriate number of OLH can realize a near‐optimal synergistic catalytic effect, which is pivotal for rational design of oxygen‐containing materials.     

混合滤波器组ADC通路失配偏差的校准方法

 针对各采样通路之间的不匹配影响混合滤波器组ADC的重构精度这一问题,本文提出了一种校准混合滤波器组ADC通路失配偏差的模型,该模型将通路间的增益偏差、相位偏差和带宽失配偏差引入到混合滤波器组ADC中.基于此模型,建立根据输出数据求解超定方程组估算失配偏差的方法,给出引入失配偏差的混合滤波器组的结构,推导出其完美重构条件.设计实现了160MHz 12-bit的两通路混合滤波器组ADC系统,实验结果表明,提出的通路失配偏差的校准方法可提高系统的无杂散动态范围(SFDR)23dB.     

低功率抽运光纤参量振荡器的时钟提取抖动性能

采用两次光调制技术将非归零(NRZ)码数据转换成归零(RZ)码光信号后,利用光纤参量振荡器(FOPO)结构实现了较低光功率抽运下的参量波长转换和时钟提取功能。实验表明,对于波长转换间隔为1.6nm的10Gbit/s时钟提取,优化的输入抽运光功率范围是8～14dBm;当输入信号的幅度抖动和相位抖动分别大于2.28mV和3.5ps时,该时钟提取系统可实现抖动抑制功能,其输入/输出抖动转移曲线斜率约为0.29和0.16。     

Universal coding of integers and unbounded search trees

In this paper we study universal coding problems for the integers, in particular, establish rather tight lower and upper bounds for the Elias omega code and other codes. In these bounds, the so-called log-star function plays a central role. Furthermore, we investigate unbounded search trees induced by these codes, including the Bentley-Yao search tree. We will reveal beautiful recursion structures latent in these search trees as well as in these codes. Finally, we introduce the modified log-star function to reveal the existance of better prefix codes than the Elias omega code and other known codes     

Various Approaches in Kinetics Modeling of Real Feedstock Hydrodesulfurization

This brief review discusses various important approaches in kinetics modeling of real feedstock hydrodesulfurization. These include analytical aspects of dealing with complicated real feedstock, structural approaches, linear-free energy relationships, and the continuum theory in hydrodesulfurization modeling.     

The composite characteristics of infilled frames

The analysis of the infilled frames, in regard to the stress distribution and stiffness, is complicated by the existence of an interface between the panel and the framework, which might be of different materials and of different dimensional parameters.Detailed theoretical and experimental studies are presented in respect of single-storey infilled frames. The theoretical approach uses a general stress function expressed in the form of Fourier Series. The stress distribution in the panel is obtained from the solution of the rigorous theoretical approach and is experimentally investigated by photoelastic frozen-stress technique using three different models. Tests on the stiffnesses of two other models made of Perspex frames with weak infills are also reported. The experimental and theoretical results of the five models show good agreement.     

对全球化语境下中国住区景观设计风格的思考

以全球化背景下的当代中国城市住区景观为对象,筒述了中国住区景观发展历程,对当代中国住区景观西化现象进行反思。通过探讨住区景观设计风格背后的问题,期望借此促进中国住区景观设计回归本土设计哲学。     

Intramolecular Donor–Acceptor Regioregular Poly(3‐hexylthiophene)s Presenting Octylphenanthrenyl‐Imidazole Moieties Exhibit Enhanced Charge Transfer for Heterojunction Solar Cell Applications

Intramolecular donor–acceptor structures prepared by covalently binding conjugated octylphenanthrenyl‐imidazole moieties onto the side chains of regioregular poly(3‐hexylthiophene)s exhibit lowered bandgaps and enhanced electron transfer compared to the parent polymer, e.g., conjugation of 90 mol% octylphenanthrenyl‐imidazole moieties onto poly(3‐hexylthiophene) chains reduces the optical bandgap from 1.91 to 1.80 eV, and the electron transfer probability is at least twice as high as that of pure poly(3‐hexylthiophene) when blended with [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester. The lowered bandgap and the fast charge transfer both contribute to much higher external quantum efficiencies, thus much higher short‐circuit current densities for copolymers presenting octylphenanthrenyl‐imidazole moieties, relative to those of pure poly(3‐hexylthiophene)s. The short‐circuit current density of a device prepared from a copolymer presenting 90 mol% octylphenanthrenyl‐imidazole moieties is 13.7 mA · cm^?2 which is an increase of 65% compared to the 8.3 mA · cm^?2 observable for a device containing pure poly(3‐hexylthiophene). The maximum power conversion efficiency of this particular copolymer is 3.45% which suggest that such copolymers are promising polymeric photovoltaic materials.