Comparison of exhaust emissions from Swedish environmental classified diesel fuel (MK1) and European Program on Emissions, Fuels and Engine Technologies (EPEFE) reference fuel: a chemical and biological characterization, with viewpoints on cancer risk

Diesel fuels, classified as environmentally friendly, have been available on the Swedish market since 1991. The Swedish diesel fuel classification is based upon the specification of selected fuel composition and physical properties to reduce potential environmental and health effects from direct human exposure to exhaust. The objective of the present investigation was to compare the most stringent, environmentally classified Swedish diesel fuel (MK1) to the reference diesel fuel used in the "European Program on Emissions, Fuels and Engine Technologies" (EPEFE) program. The study compares measurements of regulated emissions, unregulated emissions, and biological tests from a Volvo truck using these fuels. The regulated emissions from these two fuels (MK1 vs EPEFE) were CO (-2.2%), HC (12%), NOx (-11%), and particulates (-11%). The emissions of aldehydes, alkenes, and carbon dioxide were basically equivalent. The emissions of particle-associated polycyclic aromatic hydrocarbons (PAHs) and 1-nitropyrene were 88% and 98% lower than those of the EPEFE fuel, respectively. The emissions of semi-volatile PAHs and 1-nitropyrene were 77% and 80% lower than those from the EPEFE fuel, respectively. The reduction in mutagenicity of the particle extract varied from -75 to -90%, depending on the tester strain. The reduction of mutagenicity of the semi-volatile extract varied between -40 and -60%. Furthermore, the dioxin receptor binding activity was a factor of 8 times lower in the particle extracts and a factor of 4 times lower in the semi-volatile extract than that of the EPEFE fuel. In conclusion, the MK1 fuel was found to be more environmentally friendly than the EPEFE fuel.     

Reliability of optimal control strategies for photochemical air pollution

This study illustrates how consideration of modeling uncertainties can affect optimal control strategies for urban ozone. Control strategies are investigated for illustrative cases of air parcel trajectories ending at Azusa, CA, and Riverside, CA, on August 28, 1987. The control strategies are designed to achieve a specified air quality target with a given reliability, considering uncertainties in the California Institute of Technology's trajectory model and its inputs, including uncertainties in emissions and in the SAPRC-97 chemical mechanism. A decoupled stochastic optimization scheme is used to solve the chance-constrained programming problem. Least-cost control strategies derived using nominal model inputs and parameter values have low reliability for some target O3 concentrations when uncertainties are taken into account. For the case considered, reducing volatile organic compound (VOC) emissions from motor vehicles is identified as the least-cost approach to meeting O3 targets at Azusa. However, the optimal control strategies for Riverside depend on the target O3 concentrations and the level of reliability required. Consideration of model uncertainty is found to shift the focus from VOC controls to nitrogen oxide controls for the Riverside trajectory.     

EFFECT OF A PROPELLER AND GAS DIFFUSION ON BUBBLE NUCLEI DISTRIBUTION IN A LIQUID

A multi-bubble dynamics code accounting for gas diffusion in the liquid and through the bubble wall was developed and used to study the modification of a bubble nuclei population dynamics by a propeller.The propeller flow field was obtained using a Reynolds-Averaged Navier-Stokes(RANS) solver and bubble nuclei populations were propagated in this field.The numerical pro-cedure enabled establishment of the possibility of production behind the propeller of relatively large visible bubbles starting from typical ocean nuclei size distributions.The resulting larger bubbles are seen to cluster in the blade wakes and tip vortices.Parametric investigations of the initial nuclei size distribution,the dissolved gas concentration,and the cavitation number were conducted to ide-ntify their effects on bubble entrainment and the resultant void fractions and bubble distribution modifications downstream from the propeller.Imposed synthetic turbulence-like fluctuations unto the average RANS flow field were also used to study the effect avera-ging in the RANS procedure has on the results.     

Demonstration of a micro-fabricated hydrogen storage module for micro-power systems

The objective of this work was to demonstrate a micro-fabricated hydrogen storage module for micro-power systems. Hydrogen storage materials were developed as thin-film inks to be compatible with an integrated manufacturing process. Performance and durability of storage modules were evaluated. Further, applications were demonstrated for a nickel-hydrogen battery and a micro-fabricated hydrogen-air PEM fuel cell. The ink making process, in which polymer binders and solvents were added to the palladium-treated alloys, slightly decreased the storage capacities, but had little effect on the activation properties of the treated alloys. After 5000 absorption/desorption cycles under hydrogen, the hydrogen storage capacities of the thin-film inks remained high. Absorption/desorption behavior of the ink was tested in the environment of a new type nickel-hydrogen battery, in which it would in contact with 26 wt% KOH solution, and the ink showed no apparent degradation. Storage modules were successfully used as the hydrogen source for PEM fuel cell.     

大坝应急计划的风险分析

概述应急计划的制定过程。在计划制定过程中，不同阶段可作为讨论各种风险分析法的基础，说明风险分析法怎样才能成为制定应急计划的工具。重点讨论便于应用、且又不需要大量资料数据的定性方法。     

速度随深度线性变化的横向各向同性介质的倾角时差误差

Levin利用共中心点(CMP)道集模拟了均质、横向各向同性介质下平界面倾斜层产生的反射时差。对某些介质而言,当各向异性对称轴是垂直对称轴时,我们可以发现,叠加速度与熟知的以余弦倾角校正为基础的多向同性预测速度间存在差异。文中,我们用具有垂直对称轴、且介质速度随深度线性变化的横向各向同性介质做了类似的试验。Levin对同一组内的四种各向异性介质的研究结果表明,对所研究的速度梯度来说,以反射层倾角做倾角校正获得的叠加速度与相应均质介质叠加速度几乎没有差异。正如各向同性介质一样,非均匀横向各向同性介质中的旅行时可用垂向速度等于非均质介质的垂向rms均方根速度     

Effects of the sample preparation temperature on the nanostructure of compression moulded ultrahigh molecular weight polyethylene

In this study, the effects of the sample sectioning temperature on the surface nanostructure and mechanical response of compression moulded ultrahigh molecular weight polyethylene (UHMWPE) at a nanometer scale (nanomechanical properties) have been characterized. The primary focus of this work was to determine if the sample sectioning temperature significantly changed the nanostructure of UHMWPE, while the secondary focus was to characterize the effect on the mechanical response due to the changes in the sectioned surface nanostructure. The goals of this study were: (a) to investigate the potential possibility of creating surface artefacts by the sample preparation technique by sectioning at different temperatures relative to the published range of glass transition temperatures, Tg, for PE (-12, -80 and -25 degrees C); (b) to determine the possibility of molecular orientation induced by plastic deformation of the UHMWPE sample during the process of sample preparation; (c) to measure the relative difference in nanomechanical properties owing to evolution of different nanostructures as a function of sample sectioning temperature. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and nanoindentation were used to demonstrate that the sectioning temperature caused a change in nanostructure of the compression moulded UHMWPE sectioned surface, explaining the change in mechanical response to indentation at a nanoscale. In this study, it was demonstrated that significant plastic deformation occurs when a shear stress is applied between the glass or diamond blade and the UHMWPE during sample preparation under ambient conditions at a temperature of 22 degrees C. These results also suggest that an optimum sample sectioning temperature should definitely be below the measured Tg of the polymer.     

Effect of time of restriction on the decrease in mitochondrial H2O2 production and oxidative DNA damage in the heart of food-restricted rats

In the present study, the question if medium-term (4 months) caloric restriction (40%) decreases mitochondrial H2O2 production and oxidative DNA damage was investigated. Caloric restriction (CR) is the only experimental manipulation that increases maximum life span. Previous long-term CR studies have showed that CR decreases the mitochondrial rate of free radical production in diverse tissues and species. Those studies agree with the idea that the superior longevity of the restricted animals can be partly due to their lower mitochondrial rate of free radical generation. However, caloric restriction effects strongly depend on implementation time. Previous studies have shown that the decrease induced by CR on oxygen radical generation and oxidative damage to mitochondrial DNA occurs after 1 year but not after 6 weeks of restriction. In the present investigation, mitochondrial H2O2 production did not change in medium-term (4 months) caloric restricted animals, and, in agreement with that, no differences were found in either mitochondrial or nuclear oxidative DNA damage between restricted and ad libitum-fed animals. These results confirm the importance of the time of CR implementation, and show that time longer than 4 months is needed to decrease the mitochondrial rate of free radical generation and the oxidative damage to mtDNA in the rat heart.     

激光传感器用于纱线速度的测定

激光技术具有不接触、高精度、高速动态等优点,通过首次将激光技术整合到一台低价位的串联传感器中,从此在纺织生产过程中便开始有了一种全新的测定纱线速度和纱线长度的方法。     

Phenotypic and genotypic characterization of Oenococcus oeni strains isolated from Italian wines

A phenotypic and genotypic characterization of 84 Oenococcus oeni isolates from Italian wines of different oenological areas was carried out. Numerical analysis of fatty acid profiles grouped the isolates into two clusters at low level of similarity (63%), the minor cluster containing seven isolates besides the type and the reference strains. Forthy-eight O. oeni isolates, representative of the two clusters, showed no differences in their metabolic properties (heterolactic fermentation pattern, citrate degradation capability and formation of some secondary metabolites). Moreover, the analysis of species-specific randomly amplified polymorphic DNA and 16S-23S rDNA intergenic spacer region polymorphism as well as the sequence-specific separation of V3 region from 16S rDNA by denaturing gradient gel electrophoresis demonstrated a substantial homogeneity among the isolates. On the basis of ApaI Pulsed Field Gel Electrophoresis (PFGE) restriction patterns, the 84 isolates were grouped into five different clusters at 70% similarity, but no correlation with the phenotypic groups could be demonstrated. However, by combining phenotypic and genotypic data, the 84 O. oeni isolates grouped into eight phenotypic-genotypic combined profiles and a relationship between the origin of the isolates and their combined profile became evident, so that a sort of strain specificity can be envisaged for each wine-producing area.