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111.
112.
Although sound AA6061-T6 joints can be produced by friction stir welding, a loss in strength takes place in the weld region. In this study, it was demonstrated that the strength of the nugget could be increased by the use of a higher strength interlayer during friction stir welding. This strength recovery cannot, however, be attainable in the heat affected zone. Although an external cooling was applied during welding in order to increase strength in the heat affected zone, it was not sufficient for achieving the required cooling condition for improved strength. 相似文献
113.
1 INTRODUCTIONAntimonymercaptides[1~ 4 ] usedasheatstabiliz erisattractivenotonlyforitsrelativelylowcost ,butalsoforitssimilarstabilizingeffectcomparedwiththatofthemostexcellentone organotin .Bymakingfulluseoftheplentifulantimonyresource ,developingantimonym… 相似文献
114.
矿区生态环境修复旨在通过人工重建和改良,将受损矿区生态环境的健康风险或生态风险降至可接受风险水平。实现这一目标,需要运用适应性管理跟踪修复状况、评估阶段目标、调整完善修复措施,促进人工干预和改造后形成的生态系统与自然生态系统相适应。从制度层面来看,中国矿区生态环境修复的适应性管理程度不高,尚未形成全面、统一的制度体系,距系统性、审慎性、动态性的规范要求仍有提升空间。本文结合实践提出优化矿区生态环境修复制度的方案:以可接受风险水平为依据,统筹设定矿区生态环境修复的一般要求,为全国范围内的活动划定行为底线;以最坏情况分析、信息披露与公开评议为保障,共同预防在修复问题上的决策失误;以生态环境质量损害和生态系统服务价值评估为基础,建立动态的监测结果评估、修复方案调整和监管机制。 相似文献
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116.
There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/Xo) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H2/mol sucroseadded was obtained at initial pH of 7 and COD of 10 g/L. Initial S/Xo values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
117.
Cellulase cross‐linked enzyme aggregates (CLEA) activities can be modulated and enhanced by precipitant selection 下载免费PDF全文
118.
This paper reports an investigation into new connection types and their behaviors determined using full-scale experiments. T-shaped connections were created using the IPE standard profile. The aim of this study was to analyze the influence of T connections based on the IPE standard profile, height of beam to height of T-stub joint (H) of T-stub joints, and lengths (X) of T-stub joints on the behavior of steel connections, in order to provide the necessary data for improving Eurocode 3 and enable efficient use of residue IPE standard profiles and back to the consumption cycle. While the moment resistance values increased with an increase in H from Hmin to Hmax in model groups with X of 126 mm, and the energy dissipation increased with an increase in H from Hmin to Hmax and also with an increase in the lengths (X) of T-stub joints from 54 to 126 mm. 相似文献
119.
Kamile Tosun Burak Felekoğlu Bülent Baradan İ. Akın Altun 《Construction and Building Materials》2009,23(7):2534-2544
A comparative study has been performed on the sulfate resistance of Portland limestone cement (PLC) mortars exposed to extraordinary high sulfate concentrations (200 g/l). PLCs have been prepared by using two types of clinkers having different C3S/C2S ratios and interstitial phase morphologies. Blended cements have been prepared by replacing 5%, 10%, 20% and 40% of clinker with limestone. Cubic (50 × 50 × 50 mm) and prismatic (25 × 25 × 285 mm) cement mortars were prepared. After two months initial water curing, these samples were exposed to three different sulfate solutions (Na2SO4 at 20 °C and 5 °C, MgSO4 at 5 °C). Solutions were not refreshed and pH values of solutions were monitored during the testing stage. The compressive strength and length changes of samples have been monitored for a period of 1 year. Additional microstructural analyses have been conducted by XRD and SEM/EDS studies. Results indicated that in general, limestone replacement ratio and low temperature negatively affect the sulfate resistance of cement mortars. Additionally, clinkers of high C3S/C2S ratios with dendritic interstitial phase structure were found to be more prone to sulfate attack in the presence of high amounts of limestone.From the results, it is postulated that in the absence of solution change, extraordinary high sulfate content modified the mechanism of sulfate reactions and formation of related products. At high limestone replacement ratios, XRD and SEM/EDS studies revealed that while ettringite is the main deterioration product for the samples exposed to Na2SO4, gypsum and thaumasite formation were dominant products of deterioration in the case of MgSO4 attack. It can be concluded that, the difference between reaction mechanisms of Na2SO4 and MgSO4 attack to limestone cement mortars strongly depends on the pH change of sulfate solutions. 相似文献
120.
Effect of a sulfonated azo dye and sulfanilic acid on nitrogen transformation processes in soil 总被引:1,自引:0,他引:1
F. Olcay Topa Efsun Dindar Selnur Uarolu Hüseyin S. Bakaya 《Journal of hazardous materials》2009,170(2-3):1006-1013
Introduction of organic dyes into soil via wastewater and sludge applications has been of increasing concern especially in developing or under-developed countries where appropriate management strategies are scarce. Assessing the response of terrestrial ecosystems to organic dyes and estimating the inhibition concentrations will probably contribute to soil remediation studies in regions affected by the same problem. Hence, an incubation study was conducted in order to investigate the impact of a sulfonated azo dye, Reactive Black 5 (RB5) and sulfanilic acid (SA), a typical representative of aromatic sulfonated amines, on soil nitrogen transformation processes. The results apparently showed that nitrogen related processes in soil can be used as bioindicators of anthropogenic stress caused by organic dyes. It was found that urease activity, arginine ammonification rate, nitrification potential and ammonium oxidising bacteria numbers decreased by 10–20% and 7–28% in the presence of RB5 (>20 mg/kg dry soil) and SA (>8 mg/kg dry soil), respectively. Accordingly, it was concluded that organic dye pollution may restrict the nitrogen-use-efficiency of plants, thus further reducing the productivity of terrestrial ecosystems. Furthermore, the response of soil microbiota to SA suggested that inhibition effects of the organic dye may continue after the possible reduction of the parent dye to associated aromatic amines. 相似文献