厌氧/好氧SNEDPR系统处理低C/N污水的优化运行

为实现同步硝化内源反硝化除磷(SNEDPR)系统的优化运行,以实际生活污水为处理对象,采用厌氧(180min)/好氧运行的SBR反应器,并通过联合调控好氧段溶解氧(DO)浓度(0.3~1.0mg/L)和好氧时间(150~240min),考察了该系统脱氮除磷特性.并结合荧光原位杂交(FISH)技术对系统优化过程中各功能菌群的结构变化情况进行了分析.试验结果表明,当系统好氧段DO浓度由约1.0mg/L逐渐降至0.3mg/L,且好氧时间由-150min逐渐延长至240min后,出水PO_4^(3-)-P浓度稳定在0.4mg/L左右,但出水TN浓度由14.3mg/L降至8.7mg/L,TN去除率由75%提高至84%.此外,随着好氧段DO浓度的降低,SNED现象愈加明显-,SNED率由34.7%逐渐升高至63.8%.SNED的加强,降低了出水NO_3^--N浓度,并提高了系统的脱氮性能和厌氧段的内碳源储存量.FISH结果表明:经127d的优化运行,系统内PAOs,GAOs和AOB(氨氧化菌)仍保持在较高水平(分别全菌的29%±3%,20%±3%和13%±3%),其保证了系统除磷、硝化和反硝化脱氮性能;但NOB(亚硝酸盐氧化菌)含量减少了50%,为系统内实现短程硝化内源反硝化提供了可能.

SPNED-PR系统内PAOs-GAOs的竞争关系及其氮磷去除特性

为研究同步短程硝化内源反硝化除磷(SPNED-PR)系统的脱氮除磷特性及系统内聚磷菌(PAOs)和聚糖菌(GAOs)在氮磷去除的贡献和竞争关系,本研究以实际低C/N比(4左右)生活污水为处理对象,考察了不同浓度的溶解氧(DO)(0.5~2.0mg/L)、NO2--N(4.7~39.9mg/L)和NO3--N(5.0~40.0mg/L)对延时厌氧(150min)/低氧(180min,溶解氧0.5~0.7mg/L)运行的SPNED-PR系统氮磷去除特性和底物转化特性的影响.结果表明,DO浓度均不影响PAOs和GAOs的好氧代谢活性,且两者之间几乎不存在DO竞争.不同NO2--N浓度条件下,GAOs较PAOs更具竞争优势,NO2--N主要是通过GAOs去除的(约占58%);且GAOs所具有的高内源反硝化活性和亚硝耐受力,减弱了高NO2--N浓度(26.2~39.9mg/L)对PAOs反硝化吸磷的抑制,保证了系统的脱氮除磷性能.不同NO3--N浓度条件下,PAOs较GAOs处于竞争优势,其在NO3--N去除中的贡献比例达61.2%.此外,SPNED-PR系统的PURDO>PURnitrate>PURnitrite,PAOs对DO的优先利用保证了低氧条件下系统的高效除磷,且GAOs的内源短程反硝化特性保证了系统的高效脱氮.

GCr15钢在时效过程中的相变动力学及组织演变

利用DSC测试和等转变量法获得了经淬、回火后的GCrl5轴承钢在不同时效温度下残留奥氏体分解和碳化物转变的动力学模型，并利用XRD、SEM、洛氏硬度等测试方法，对不同温度时效不同时间后的微观组织进行了分析。结果表明，动力学模型能对时效过程中的组织演变进行较为准确的预测，时效处理可以降低残留奥氏体的含量，提高其相内碳浓度，但是同时也会促使碳化物颗粒长大，并使材料的洛氏硬度有所降低。

Preliminary assessment of the navigation and positioning performance of BeiDou regional navigation satellite system

BeiDou regional navigation satellite system （BDS） also called BeiDou-2 has been in full operation since December 27, 2012. It consists of 14 satellites, including 5 satellites in Geostationary Orbit （GEO）, 5 satellites in Inclined Geosynchronous Orbit （IGSO）, and 4 satellites in Medium Earth Orbit （MEO）. In this paper, its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing, including satellite visibility, Position Dilution of Precision （PDOP） value, the precision of code and carrier phase measurements, the accuracy of single point positioning and differential position- ing and ambiguity resolution （AR） performance, which are also compared with those of GPS. It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm, respectively, which are comparable to those of GPS, and the accuracy of BDS single point positioning has satisfied the design requirement. The real-time kinematic positioning is also feasible by BDS alolae in the opening condition, since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS. The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km, which is on the same level with that of GPS. For the combined BDS and GPS, the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly. The accu- racy of BDS/GPS carrier phase differential positioning is about 35 and 20 % better than that of GPS for two short baseline tests in this study. The accuracy of BDS code differential positioning is better than 2.5 m. However it is worse than that of GPS, which may result from large code multipath errors of BDS GEO satellite measurements.

固溶温度对S22053双相不锈钢组织与力学性能的影响

通过光学显微镜、拉伸试验和低温冲击试验研究了1040、1060和1080℃温度固溶处理S22053双相不锈钢的组织、室温力学性能和低温冲击性能。结果表明：不同温度的固溶处理会造成S22053不锈钢α相与γ相两相比例、形态的变化,进而造成其室温拉伸性能和低温冲击性能的变化。随着固溶处理温度的提高,S22053不锈钢的强度会出现一定程度的提高,而伸长率和断面收缩率几乎不受影响。试样的低温冲击性能随着固溶温度的升高先增加再显著降低。