Effect of Bolts Assembly on the Deformation and Pressure Distribution of Flow‐Channel Plates in Micro‐PEMFC

The main aim of this study is to simulate the response of a micro‐PEMFC numerically by utilizing a 3‐D FEM model while the micro‐PEMFC was assembled by three pairs of bolt along the upper and lower portions, respectively, of the end plates. The effects of different bolts locking sequences on the deformation and pressure distributions at flow‐channel plates in a micro‐PEMFC were investigated. The simulated results showed that if one locked the middle bolt either on the upper or lower portion first, then the obtained warpage, uniformities of deformation and von Mises equivalent stress were superior than those results if one locked either one of the four corner bolts first. Also, among the three pairs of bolts used for assembling the cell, the first locking bolt of the first pair of locking bolt and the first locking bolt of the rest of two pairs of locking bolt were to minimize the warpage and stress should locate on the different portions of the end plates.     

JPEG forensics scheme for signature embedding and packet‐level detection

As the volume of multimedia digital information transmitted over the Internet continues to rise, the problem of preventing the unauthorized tampering and dissemination of digital content has emerged as a major concern. Thus, the present study proposes a forensic scheme for tracking the dissemination of copyright‐protected JPEG images over the Internet. The proposed scheme incorporates two basic mechanisms, namely signature embedding and signature detecting. To preserve the quality of the protected JPEG images, the signature is embedded at the application layer. By contrast, the signature detection process is performed at the packet level in order to improve the scalability of the proposed mechanism. For any flows regarded as suspicious, the signatures embedded in the JPEG packet trains are compared with the known digital signatures for forensic purposes. The experimental results show that the embedded signature has no effect on the visual quality of the JPEG image. Moreover, it is shown that the computational complexity of the proposed detection scheme is significantly lower than that of existing application‐level schemes. Thus, the scheme provides an ideal solution for the forensic analysis of JPEG streams over large‐scale network environments such as the Internet. Copyright © 2013 John Wiley & Sons, Ltd.     

Distinguishing the Importance of Fullerene Phase Separation from Polymer Ordering in the Performance of Low Band Gap Polymer:Bis‐Fullerene Heterojunctions

One way to improve power conversion efficiency (PCE) of polymer based bulk‐heterojunction (BHJ) photovoltaic cells is to increase the open circuit voltage (V _oc). Replacing PCBM with bis‐adduct fullerenes significantly improves V _oc and the PCE in devices based on the conjugated polymer poly(3‐hexyl thiophene) (P3HT). However, for the most promising low band‐gap polymer (LBP) system, replacing PCBM with ICBA results in poor short‐circuit current (J _sc) and PCE although V _oc is significantly improved. The optimization of the morphology of as‐cast LBP/bis‐fullerene BHJ photovoltaics is attempted by adding a co‐solvent to the polymer/fullerene solution prior to film deposition. Varying the solubility of polymer and fullerene in the co‐solvent, bulk heterojunctions are fabricated with no change of polymer ordering, but with changes in fullerene phase separation. The morphologies of the as‐cast samples are characterized by small angle neutron scattering and neutron reflectometry. A homogenous dispersion of ICBA in LBP is found in the samples where the co‐solvent is selective to the polymer, giving poor device performance. Aggregates of ICBA are formed in samples where the co‐solvent is selective to ICBA. The resultant morphology improves PCE by up to 246%. A quantitative analysis of the neutron data shows that the interfacial area between ICBA aggregates and its surrounding matrix is improved, facilitating charge transport and improving the PCE.     

高炉喷吹溶剂若干问题的探讨

基于国内外研究成果，对高炉喷吹熔剂的若干问题进行了分析讨论。喷吹熔剂的作用，主要是可以使铁水的硅含量和硫含量降低，当熔剂和煤粉混喷时，对煤粉还具有助燃，防爆作用，在熔剂选择方面，ＭｇＯ系比ＣａＯ系的喷吹效果好，就熔剂的喷吹方式而言，熔剂与煤混磨、混喷最为理想。     

监理工作的信息管理

介绍信息管理工作中涵盖的内容,确保信息资源的利用方法。     

城市河流生态修复的环境价值及实现机制初探

探讨了城市河流环境价值内涵、分类体系和常用度量方法，以上海市长宁区河流生态修复为案例，测算其环境价值，分析投入产出；在此基础上，识别我国城市河流生态修复资金短缺的根因，初步探讨城市河流生态修复的环境价值实现机制。结果表明：（1）生态修复后的城市河流环境价值增值显著，约46244.24×104元/年，相当于2007年长宁区GDP的1.19%，年均产出投入比为14.34；（2）城市河流生态修复的正外部经济效应显著，河流沿线居民和企业是最大的受益者；（3）政府进行河流两岸统一开发、水资源定价、税费征收与转移支付是城市河流生态修复环境价值的主要实现途径；（4）营造全社会参与河流保护氛围，并使公众理解城市河流环境价值，是价值实现的关键步骤。     

Do Cu(II) ions need Al atoms in their environment to make CuSiBEA active in the SCR of NO by ethanol or propane? A spectroscopy and catalysis study

The two-step postsynthesis method (creation of vacant T-sites and associated SiOH groups by dealumination of BEA zeolite with nitric acid followed by incorporation of copper in the resulting SiBEA by impregnation with an aqueous solution of copper nitrate) allows to obtain a CuSiBEA zeolite which contains 0.8 Cu wt%. The incorporation of Cu(II) into the lattice of SiBEA is evidenced by XRD while the concomitant consumption of SiOH groups is monitored by FTIR. The presence of mainly isolated mononuclear Cu(II) in D_2d-distorted tetrahedral symmetry is evidenced by diffuse reflectance UV–vis-NIR, EXAFS and XANES. The CuSiBEA zeolite is active in the selective catalytic reduction (SCR) of NO with ethanol or propane with maximum NO conversion of 40 and 20% and selectivity toward N₂ close to 80–90 and 90–100%, respectively. These results suggest that the SCR process occurs on isolated mononuclear Cu(II) in D_2d-distorted tetrahedral symmetry after Al atoms have been removed from the zeolite structure. Thus, Cu(II) ions do not need Al atoms in their environment to be catalytically active. The lack of correlation between the SCR activity in presence of ethanol and the oxidation of NO to NO₂ suggests that the two reactions are more competitive than sequential. The higher activity of CuSiBEA with ethanol than with propane may be due to different activation energies and/or reaction mechanisms.     

高档普采工作面生产系统可靠性分析

通过对高档普采工作面生产系统的结构分析，构造简化马尔可夫图及可修复串联系统可靠性指标函数，并通过实例计算，得出分析结论。     

原子荧光光谱法测定铅锌精矿中汞的研究

研究原子荧光光谱法测定铅、锌及其混合精矿中汞的分析方法．考察原子化温度、灯电流、负高压、载气流量、延迟时间等仪器条件，进行测定介质与酸度、硼氢化钾与氢氧化钾浓度、工作曲线线性、共存元素干扰等条件试验．该方法操作简单、准确、灵敏度高，应用于铅矿、锌矿及其混合矿中汞的分析，线性范围为O．05～1μg／100mL，回收率为95％～106％，RSD≤5％．