天然气闭环燃料重整的均质压燃(HCCI)试验研究

氢具有良好的可燃性,可用少量氢作为添加荆来改善天然气的自燃特性.通过试验,对比了天然气和汽油HCCI的性能,利用模拟的重整气验证了天然气加氢的效果,研究了天然气燃料重整实现在线产生氢的可行性,并进行了天然气在线燃料重整产生富氢重整气的闭环试验.试验结果表明,利用再循环的废气进行燃料重整产生富氢重整气是扩展HCCI工作范围和降低NOx排放的切实可行的有效方法.     

Influence of the artificial saliva storage on 3‐D surface texture characteristics of contemporary dental nanocomposites

The aim of this study was to analyse the influence of the artificial saliva on a three‐dimensional (3‐D) surface texture of contemporary dental composites. The representatives of four composites types were tested: nanofilled (Filtek Ultimate Body, FUB), nanohybrid (Filtek Z550, FZ550), microfilled (Gradia Direct, GD) and microhybrid (Filtek Z250, FZ250). The specimens were polymerised and polished by the multistep protocol (SuperSnap, Shofu). Their surface was examined, before and after 3 weeks’ exposure to artificial saliva storage. The surface texture was analysed using the atomic force microscope (AFM). The obtained images were processed to calculate the areal autocorrelation function (AACF), anisotropy ratio S_tr (texture aspect ratio), and structure function (SF). The log–log plots of SF were used to calculate fractal properties, such as fractal dimension D, and pseudo‐topothesy K. The analysis showed changes in surface anisotropy ratio S_tr values, which became higher, whereas the S_q roughness (root‐mean‐square) reduced after the artificial saliva storage. All the samples exhibited bifractal structure before the saliva treatment, but only half of them remained bifractal afterwards (GD, FZ250), whereas the other half turned into a monofractal (FUB, FZ550). The cube‐count fractal dimension D_cc was found to be material‐ and treatment‐insensitive.     

DECISION ANALYSIS FOR NEW CONSTRUCTION TECHNOLOGY IMPLEMENTATION

This paper first reviews factors that are the basis of construction technology development. The economic feasibility study of implementing a new technology in a construction firm is decomposed into the feasibility study of technology acquistion and that of technology operation. Risks associated with each of these two parts are identified. Based on the theory of utility under uncertainty, a model for evaluation of new technology alternatives is proposed. An example of decision analysis for implementation of partially automated tremie concreting of slurry walls is presented to illustrate this method. The significance of sensitivity analysis in the evaluation process is discussed.     

Structure Studies on the Nitrosyl Derivative of Heme

The electronic spectra were obtained on the nitrosyl derivative of heme prepared by synthesis from hemin and sodium nitrite within the UV-vis region. They were compared with spectra of nitrosyl derivative of heme dimethyl ester within the IR region. The degree of hemin reacting with nitric oxide (NO) ligand as well as the stability constant of the heme:NO complex were calculated. Results showed that in the nitrosyl derivative of heme one NO ligand was bound with one heme iron of the pigment. Therefore, it seems that the cooked cured-meat pigment is a mononitrosyl derivative of heme.