Influences of ultrasonic irradiation on the morphology and structure of nanoporous Co nanoparticles during chemical dealloying

The Co-61.8 wt% Al nanoparticles of 45 nm were prepared by hydrogen plasma-metal reaction (HPMR) method. The nanoparticles display core shell structure with Al13Co4 and CoAl core and aluminum oxide shell (about 2 nm). Under ultrasonic irradiation, nanoporous fcc-Co nanoparticles were produced successfully by chemically dealloying the Co-Al nanoparticles at room temperature, whereas, without ultrasonic irradiation CoAl phase could hardly react with sodium hydroxide solution. At 323 K the Co-Al nanoparticles could be dealloyed to fcc-Co and hcp-Co phases even without ultrasonic irradiation. The surface area of the dealloyed nanoparticles under ultrasonic irradiation was larger than that of the dealloyed sample without ultrasonic irradiation at the same temperature. It is believed that the microjet and shock-wave induced by ultrasonic irradiation give rise to particles size reduction, interparticle collision and surface cleaning, and accelerate the dealloying process and the phase transformation.     

SNCR应用于水泥窑氮氧化物控制的氨氧化

为了对水泥窑应用SNCR控制技术时CaO催化NH3氧化问题进行研究,该文采用固定床反应器,研究温度(650～950℃)、NH3体积分数(100×10-6～1500×10-6)和O2体积分数(0～4%)对于CaO催化NH3氧化作用的影响。采用Fourier变换红外光谱仪(FTIR)测量NH3和NO组分的体积分数。实验结果表明:CaO催化NH3氧化反应的转化率和产物NO的选择性随NH3体积分数增加而下降,随温度和O2体积分数增加而增加。基于NH3转化率和产物NO选择性随NH3体积分数的变化规律,提出CaO催化NH3氧化的首要途径是NH3和O2的吸附,吸附态NH3会与O2反应生成NO,而非前人提出的NH3与CaO反应生成CaN。采用该机理可以较好地解释实验规律。     

竖向荷载下分布式连接全装配RC楼盖横板向受力性能试验研究

为研究分布式连接全装配RC楼盖(DCPCD)横板向受力性能,进行了6个足尺DCPCD试件和2个现浇试件在竖向均布荷载下的静载试验,分析了试件的破坏模式、挠曲变形和应变发展规律.结果表明,DCPCD板缝连接件传力性能良好,试件弯曲刚度小于现浇试件,没有明显的塑性工作阶段,且较早进入弹塑性.DCPCD横板向挠曲变形以板缝变...     

一种高灵敏度测定血红蛋白的化学发光分析方法

研究了在碱性介质和阳离子表面活性剂CTMAB存在下,牛血红蛋白催化鲁米诺-铁氰化钾的化学发光行为和化学发光反应的条件,提出一种流动注射-化学发光法测定牛血红蛋白的新方法.该方法测定牛血红蛋白的线性范围为5.18×10-10~1.29×10-6mol/L,r2=0.998 5;检出限(RSN=3)为1.2×10-10mol/L;回收率为(100±10)%;dRSD≤5%(n=6).     

O2/CO2气氛下燃煤过程中SO2排放特性实验

通过沉降炉对O2/CO2气氛和空气气氛下煤粉燃烧过程中SO2排放特性进行实验,结果表明,随燃料/氧化学当量比的增加,烟气中SO2浓度升高,单位煤生成SO2的量随燃料/氧化学当量比的增加而减少.在实验条件下,不加石灰石时,气氛和温度对SO2的生成无明显影响,SO2的生成量只与煤中含硫量以及煤的种类有关.当煤中加入石灰石后,O2/CO2气氛下SO2的排放量远小于空气气氛下,这主要是因为石灰石在O2/CO2气氛下取得的脱硫效率大大高于空气气氛下的脱硫效率.     

Effect of Ni addition on the glass-forming ability and soft-magnetic properties of FeNiBPNb metallic glasses

The effect of Ni addition on the glass-forming ability (GFA) and soft-magnetic properties of an (Fe1-xNix)75.5B14.5P7Nb3 (x=0-0.6) alloy system were investigated. We found that the addition of Ni was effective in allowing the alloy to approach a eutectic point as well as increasing the thermal stability of the supercooled liquid. By increasing the amount of Ni,the supercooled liquid region (ΔTx),the reduced glass transition temperature Trg (Tg/Tl) and the Y parameter [Tx/(Tg+Tl)] increased from 49 to 75 K,0...     

Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast China

Pollen assemblages of 53 surface pollen samples from farmlands and wastelands in Northeast China were analyzed. Tree pollen percentages were usually higher than 30%, with Pinus (26.9%), Quercus (0.9%), Betula (0.9%) and Populus (0.7%) as the major types, and herb pollen percentages were usually higher than 50%, with weedy Poaceae (8.7%), Chenopodiaceae (7.1%), Artemisia (1.9%) and Compositae (3.5%) as the major taxa. Thus, the pollen assemblages were consistent with the regional vegetation compositions. However, there were differences in pollen assemblages among regions, especially among different geomorphological units. For example, in the mountains, there were more types of tree pollen and higher total percentages (average 42%) than in other areas, while cereal pollen percentages were lowest (11.2%). In the hills and high plains, herbs made up more than 60% of the pollens, with cereals (average 53.6%) the dominant type. In the low plains, pollen types were similar to those in the hills and high plains, but total pollen concentrations and the proportion of Concentricystes were much higher, while cereal pollen percentages were slightly lower (average 41.6%). Pollen assemblages in different land use types also differed. For example, in farmland, cereal pollen percentages were more than 40% and Chenopodiaceae was usually less than 2.5%, while in wasteland, weedy Poaceae was usually less than 10% and Chenopodiaceae was usually higher than 25%. Total pollen concentrations in farmland (average 3909 grains/g) were much lower than in wasteland (average 15074 grains/g). Redundancy analysis revealed that pollen assemblages were significantly negatively correlated with mean annual temperature (-0.73) and July mean temperature (-0.81) and significantly positively correlated with mean annual precipitation (0.48), indicating that pollen assemblages in the artificial or human-disturbed vegetation reflect regional climate well. Comparison of pollen assemblages in different areas of northern China showed that pollen concentrations reflect the intensities of human impact to some degree. For example, pollen concentrations decrease as human impacts increase in intensity. The cereal pollen proportions in farmland differed by area. In Northeast China, cereal pollen proportions were distinctly higher than in most other areas of northern China, suggesting differences in planting habits and climate.     

流域水污染治理模式创新研究

我国严峻的流域水污染已成为可持续发展的严重威胁,而目前的流域水污染治理模式却难以有效地解决这一难题.针对流域水污染防治的管理体制、机制、政策体系所存在问题,提出了创新流域水污染治理模式的对策与方法.     

关于变精度粗糙集模型近似算子性质的一点注记

通过引进一对新的增值算子,对变精度粗糙集模型的部分性质进行推广,把并与交的β上下近似集之包含关系推广到相等关系(定理2).