压电智能骨料动态拉应力标定试验研究∗

为了监测混凝土内部受拉开裂损伤,提出了混凝土内部拉应力监测压电智能骨料,并对其进行了动态拉应力标定试验研究。首先,制备4个压电智能骨料受拉试件,建立拉应力监测系统;其次,对压电智能骨料施加往复拉应力,标定得到其灵敏度系数;然后,对压电智能骨料试件施加单调荷载直至其受拉破坏,得到其抗拉强度及输出的电压信号,对比了破坏过程的实际与监测荷载。结果表明,往复荷载作用下,SA输出与输入荷载呈良好的线性关系,SA的灵敏度系数一致性较好;单调荷载作用下,各SA抗拉强度均高于混凝土抗拉强度。综上,压电智能骨料有潜力应用于混凝土内部的拉应力监测。     

天津钢铁行业烧结烟气脱硫治理工程实践

天津两大钢铁企业分别采用LJS-FGD技术和石灰-石膏湿法工艺进行烧结烟气脱硫。通过分析两种脱硫方法的工程实践数据,从其脱硫效果、除尘脱硝效果、能耗技术指标等方面对两种脱硫方法进行比较:LJS-FGD技术在保证脱硫脱硝效果的基础上,具有总投资低、占地面积小、能耗低、污染小、运行成本低等特点;石灰-石膏湿法脱硫脱硝效果好,但能耗高,占地面积大,设备易于腐蚀。     

An interval joint-probabilistic programming method for solid waste management: a case study for the city of Tianjin, China

Currently, environmental protection and resources conservation continue to be challenges faced by solid-waste managers in China. These challenges are being further compounded by rapid socioeconomic devel- opment and population growth associated with increased waste generation rates and decreased waste disposal capacities. In response to these challenges, an interval joint-probabilistic mixed-integer programming （IJMP） method is developed for supporting long-term planning of waste management activities in the city of Tianjin, which is one of the largest municipalities in the northern part of China. In the IJMP, joint probabilistic constraints are introduced into an interval-parameter mixed-integer programming framework, such that uncertainties presented in terms of interval values and random variables can be reflected. Moreover, a number of violation levels for the waste-management-capacity constraints are examined, which can facilitate in-depth analyses of tradeoffs among economic objective and system-failure risk. The results indicate that reasonable solutions have been generated. They are valuable for supporting the adjustment of the city＇s existing waste-management practices and the long- term planning of the city＇s waste-management facilities.     

Using crosslinked polyvinyl alcohol polymer membrane as a separator in the microbial fuel cell

Separator between anode and cathode is an essential part of the microbial fuel cell （MFC） and its property could significantly influence the system perfor- mance. In this study we used polyvinyl alcohol （PVA） polymer membrane crosslinked with sulfosuccinic acid （SSA） as a new separator for the MFC. The highest power density of 7594-4 mW-m-2 was obtained when MFC using the PVA membrane crosslinked with 15% of SSA due to its desirable proton conductivity （5.16 x 10-2 S.cml）. The power density significantly increased to 11064- 30 mW.m-2 with a separator-electrode-assembly config- uration, which was comparable with glass fiber （11704- 46 mW.m-2）. The coulombic efficiencies of the MFCs with crosslinked PVA membranes ranged from 36.3% to 45.7% at a fix external resistance of lO00f2. The crosslinked PVA membrane could be a promising alter- native to separator materials for constructing practical MFC system.     

Seasonal and spatial variations of acid-volatile sulphide and simultaneously extracted metals in the Yangtze River Estuary

Surface sediments were collected from the Yangtze River Estuary (YRE) in May 2012, August 2012, November 2012 and February 2013 to analyse the seasonal and spatial distributions of acid-volatile sulphide (AVS), simultaneously extracted metals (SEM) and the sediment toxicity. An optimised method was used for the AVS and SEM analysis and the results showed that the seasonal variations of AVS were positively correlated with changes in water temperature and the position of higher AVS was relatively fixed. The average of SEM was gradually increased from May 2012 to February 2013 and there were abnormally high values of SEM_Cu and SEM_Ni in the YRE. Concentrations of the five SEM components were in the following order: Cd?相似文献   

Denitrification in bottom sediment near oil production facilities off the Louisiana Gulf Coast

There is little information on denitrification in Gulf of Mexico bottom sediment. Potential denitrification rates in surface sediment were measured along transects legs extending 0–800 m from two offshore oil production platforms. The average potential denitrification ranged from approximately 50 mg N m^?2 d^?1 in surface sediment near the platforms to 15 mg N m^?2 d^?1 in sediment 800 m from the platforms. Measured denitrification rates were correlated to a higher organic matter content in sediment nearer the platforms. This research examined only a small component of nitrogen processing in Gulf of Mexico sediment. Additional research should examine the effect of nitrogen loading and temporal and spatial variability on denitrification rate.     

Sensitive crop species and appropriate bioassays for potential use in phytotoxicity assessment of Pb-contaminated soils

The present study aims to determine the phytotoxic effects of lead (Pb) on corn (Zea mays), wheat (Triticum aestivum), cucumber (Cucumis sativus), cabbage (Brassica oleracea) and lettuce (Lactuca sativa) and to identify the sensitive crop species and appropriate bioassays for potential use in phytotoxicity assessment of Pb-contaminated soil. In a laboratory experiment, Pb(NO₃)₂ was added to the background soil to obtain eight Pb treatments. The results indicate that the seed germination rate of lettuce decreases by 14.44%, 30.00% and 40.00% at 2000, 3000 and 4000 mg Pb kg^?1 soil, respectively. However, the germination of corn, wheat, cucumber and cabbage is not significantly influenced by the Pb-contaminated soil treated with all the tested concentrations. Furthermore, the root elongation is more sensitive to Pb than is seed germination. The minimum concentrations of adverse effect of maize, wheat, cucumber, cabbage and lettuce are 2000, 3000, 1300, 800 and 300 mg Pb kg^?1 soil, respectively. Moreover, dicotyledon species are more sensitive than monocotyledon species. In the genotoxicity study, the mitotic index (MI) fluctuates with an increasing Pb concentration. The micronuclei (MN) frequencies of cucumber, cabbage and lettuce exhibit a dose-dependent effect at concentrations ranging from 1300 to 4000 mg Pb kg^?1 soil. It can be concluded that lettuce is a good candidate for indicating the toxicity of Pb in soil. Root elongation and the micronucleus frequency of dicotyledon are appropriate bioassays for potential use in phytotoxicity assessment of Pb-contaminated soil.     

A predator’s body coloration enhances its foraging profitability by day and night

Few predators forage by both day and night. It remains unknown, however, how the costs and benefits of foraging or signaling are partitioned in animals that forage at all times. The orb-web spider Cyrtophora moluccensis is brightly colored and forages by day and night. We determined the benefits reaped when it forages by both day and night by estimating the biomass of prey caught in their webs. Additionally, we quantified whether the spider’s presence influences the number of prey caught by day and night and whether its colorful body is visible to diurnal and/or nocturnal insects using diurnal and nocturnal insect vision models. We found that approximately five times the biomass of prey was caught in C. moluccensis’ webs by night than by day. Hemipterans, hymenopterans, and dipterans were predominantly caught by day, while lepidopterans (moths) were predominately caught by night. Accordingly, we concluded that foraging by night is more profitable than foraging by day. We predicted that other benefits, for example, energetic advantages or enhanced fecundity, may promote its daytime activity. Foraging success was greater by day and night when the spider was present in the web than when the spider was absent. We also found that parts of the spider’s body were conspicuous to diurnal and nocturnal insects, possibly through different visual channels. The colorful body of C. moluccensis, accordingly, appears to influence its foraging success by attracting prey during both the day and night.     

Characteristics of culturable endophytic bacteria of Xanthoceras sorbifolia Bunge with tumor roots北大核心CSCD

Xanthoceras sorbifolia Bunge with tumor roots was discovered, and the endophytic bacteria that were isolated from the tumor roots were purified and identified. This paper aimed to study the characteristics of endophytic bacteria. The CAS detection plate, Salkowski colorimetry, phosphate solubilizing circle, and molybdenum antimony spectrophotometry were used to analyze endophytic bacteria ability, which produced siderophores, secreted indole-3-acetic acid (IAA), and dissolved phosphorus. Strains were isolated from the tumor roots through morphological and molecular identification, and they were named XSB1-XSB9, of which 6 strains belonged to Bacillus sp., 2 strains belonged to Brevibacillus sp., and 1 strain belonged to Pseudomonas sp. All 9 strains produced siderophores; strains XSB3, XSB4, XSB8, and XSB9 were extremely high yielding, and strains XSB5 and XSB6 were high yielding. The strains with high yields were XSB3, XSB4, XSB5, XSB6, XSB8, and XSB9 and accounted for 66.7% of the tested strains. Nine strains secreted IAA; the concentration of IAA secreted by the strains that contained tryptophan was between 15-50 mg/L, and the concentration of IAA secreted by the one strain without tryptophan was between 10-35 mg/L. The IAA ability of the XSB2, XSB3, XSB4, XSB5, and XSB9 strains were significantly different (P < 0.05) after adding tryptophan. These results indicate that the synthesis of IAA may be the tryptophan synthesis pathway where tryptophan is used as a precursor. All 9 strains had some ability to dissolve phosphorus. The concentration of phosphate in the solubilizing strains, XSB1, XSB2, XSB4, and XSB5, were significantly higher than that in the other strains (P < 0.01), and the concentration of phosphate solubilizing was between 50-90 mg/L; the ability to dissolve phosphate was increased by 19-29 times. The XSB4 and XSB5 strains, which produced siderophores, secreted IAA and had a strong capacity to dissolve phosphorus, may be candidate strains for promoting growth. This research provides the foundation for the development and utilization of rhizosphere microbes to understand the resistance mechanisms and cultivation level of X. sorbifolia. © 2018 Science Press. All rights reserved.