基于涡动相关法的沉积物-水界面氧通量与水动力条件响应关系

沉积物-水界面是物质参与环境地球化学循环和生物耦合的"热区",水动力条件是沉积物-水界面物质交换的关键影响因素。溶解氧作为常用的水质评价指标,对调节生物化学进程有重要作用,因此本文采用涡动相关法这种非侵入式通量测量技术开展室内试验研究,探究沉积物-水界面氧通量与水动力条件的响应关系。结果表明:随着水体紊动增加(采用Batchelor尺度表征),扩散边界层厚度减小,氧通量增大。分析室内试验和相关研究中水动力条件、扩散边界层厚度及氧通量的关系,发现扩散边界层厚度与Batchelor尺度呈正相关关系,拟合结果表明可以用Batchelor尺度近似表示扩散边界层厚度;氧通量与扩散边界层厚度呈负相关关系,且当扩散边界层厚度小于0.5 mm时,扩散边界层厚度变化对氧通量影响更强烈,当厚度大于0.5 mm后,氧通量基本保持稳定。     

地磁坐标系下变姿态空间相机的外热流计算

为了提供准确的空间相机外热流数据,提出一种在地磁坐标系下进行频繁姿态变换的空间相机瞬态外热流计算方法。首先,确定了在J2000坐标系下太阳地球的相对位置及太阳辐照强度;其次,计算相机不同位置的地磁纬度,并采用二分法得到相机在轨运行时进出高磁纬地区(|L|60)的轨道时间;然后,依据其地磁纬度,确定相机不同时刻下的在轨姿态。最后,采用蒙特卡洛法(MCM)计算相机的各环境映射面的轨道视角系数,进而得出整轨周期内各环境映射面接受的瞬时外热流。此方法与IDEAS/TMG软件的外热流结果能够较好的吻合。与姿态稳定的相机相比,空间相机姿态频繁变化会导致外热流数值的明显波动。尤其是入光口所在的+Z面,其波动范围为0~1 245.4 W/m2。     

Production of new welding fluxes based on silicomanganese slag

ABSTRACT

The properties of a welding flux based on the silicomanganese slag are investigated. The flux is produced using the slag formed in the production of silicomanganese with different ratios of the slag fractions and different content of the water glass in the flux addition. The addition of up to 20–30% dust fraction of the silicomanganese slag to the composition of the flux results in excellent mechanical properties of specimens taken from the welded plates. The FD-UFS addition reduces the extent of contamination with non-metallic inclusions and reduces the size and amount of these inclusions. The optimum content of the water glass in the flux (up to 20–30%) was determined. Consequently, the resultant mechanical properties of the specimens taken from the welded plates are very high.     

橙红色荧光粉YPO4:Gd3+,Eu3+的制备及发光特性

采用高温固相法在1100℃下合成了橙红色荧光粉YPO₄:Gd₃₊,Eu₃₊,研究了Eu₃₊离子掺杂浓度、碱金属碳酸盐、助熔剂、敏化剂对荧光粉发光性能的影响。XRD检测结果显示：合成荧光粉为单相的YPO₄。Eu₃₊离子较佳掺杂浓度为2.5%,碱金属碳酸盐 Na₂CO₃能有效提高荧光粉的发光强度。添加助熔剂NH₄F可将荧光粉的煅烧合成温度从1100℃降低到800℃,并可促进发光中心进入晶格。Gd₃₊离子能将吸收的激发能有效传递给发光中心Eu₃₊离子,提高荧光粉的发光强度。色坐标分析显示,合成YPO₄:0.025Eu₃₊荧光粉色坐标为(0.61,0.39) ,位于橙红光的色坐标范围内。     

Recent advances in mapping environmental microbial metabolisms through 13C isotopic fingerprints

After feeding microbes with a defined ¹³C substrate, unique isotopic patterns (isotopic fingerprints) can be formed in their metabolic products. Such labelling information not only can provide novel insights into functional pathways but also can determine absolute carbon fluxes through the metabolic network via metabolic modelling approaches. This technique has been used for finding pathways that may have been mis-annotated in the past, elucidating new enzyme functions, and investigating cell metabolisms in microbial communities. In this review paper, we summarize the applications of ¹³C approaches to analyse novel cell metabolisms for the past 3 years. The isotopic fingerprints (defined as unique isotopomers useful for pathway identifications) have revealed the operations of the Entner–Doudoroff pathway, the reverse tricarboxylic acid cycle, new enzymes for biosynthesis of central metabolites, diverse respiration routes in phototrophic metabolism, co-metabolism of carbon nutrients and novel CO₂ fixation pathways. This review also discusses new isotopic methods to map carbon fluxes in global metabolisms, as well as potential factors influencing the metabolic flux quantification (e.g. metabolite channelling, the isotopic purity of ¹³C substrates and the isotopic effect). Although ¹³C labelling is not applicable to all biological systems (e.g. microbial communities), recent studies have shown that this method has a significant value in functional characterization of poorly understood micro-organisms, including species relevant for biotechnology and human health.     

Ion fluxes in medium frequency pulsed DC magnetron sputtering

The ion fluxes which bombard the substrate during deposition by asymmetric medium frequency pulsed DC magnetron sputtering have been measured as a function of substrate position and pulse frequency. It has been found that, particularly at higher pulse frequencies, the ion flux is dominated by very high energy fluxes which are determined by the positive overshoot voltage in the pulse off period. The behaviour of the ion fluxes on the magnetron centre line and in an offset position has been compared and it is shown that on the centre line there is an additional mid energy ion flux which is not present in the offset position and is thought to arise from the ion flow directed along the magnetic field lines from the racetrack region to the substrate or probe position because of the unbalanced magnetron configuration.     

Influence of Coating Granulation Process on Iron Ore Sinter Quality and Productivity

For better blast furnace performance, there has always been a need for better quality raw materials like sinter, lump ore, and pellets. Among these raw materials the usage of sinter in blast furnace is at higher side compared to other iron bearing materials. As the quality of sinter product improves, its usage in blast furnaces also increases. Iron ore fines are the main source for sinter making. To improve the sinter properties it is necessary to provide good quality of iron ore fines. Due to depletion of high grade iron ore resources, goethite and limonitic ore content in iron ore fines is expected to increase gradually. Usually limonitic and goethite ore are associated with higher alumina and LOI. The conventional sintering process is one of the well established processes for high quality hematite ore. It does not fully respond to the low grade iron ore associated with goethite and limonite. This has led to deterioration in sinter properties and productivity. In recent years the improvement in the quasi‐particle structure with the granulation process is an effective method for improving sinter quality and productivity. To improve the sinter quality and productivity for low grade iron ore fines, different granulation processes like the conventional one, and other two advanced granulation processes like coke breeze, and flux & coke breeze coating granulation were studied in detail by conducting laboratory pot grate sintering experiments. From the test results it was found that sinter productivity, physical and metallurgical properties of the sinter improved with flux & coke breeze coating granulation process compared to conventional and coke breeze coating granulation process. Proper selection of the granulation time is very important to achieve the desired sinter properties. In the present work detailed laboratory experiments have been carried out by varying the coating time from 30s to 110s to study the influence of flux & coke breeze coating granulation time on mineralogy, productivity, physical, and metallurgical properties of sinter. With a coating granulation time of 50s, higher productivity, higher yield, and stronger sinter (higher T.I) with lower RDI and ‐5mm size sinter were achieved.     

高饱和蒸发压力氨喷雾冷却沸腾传热特性

利用冷却工质的相变蒸发带走大量热量的喷雾相变冷却技术成为大功率电子元件散热需求的最佳途径.建立了双喷嘴阵列氨喷雾相变冷却实验系统,研究了饱和蒸发压力以及进口流量对氨喷雾相变冷却传热特性的影响规律.实验结果表明:在氨喷雾相变冷却过程中,维持较高的饱和蒸发压力有利于传热系数提高,过热度降低;流量对传热特性影响较大,低流量时...     

Mass Transfer Enhancement in Double‐Pass,Parallel‐Plate Mass Exchangers under Asymmetric Wall Fluxes

A device involving mass exchangers with a permeable membrane inserted to divide the open duct into two subchannels for conducting double‐pass laminar countercurrent operations under asymmetric wall mass fluxes, which results in a substantial improvement of the mass transfer, has been developed and investigated theoretically. The resultant partial differential equations for such a double‐pass forced‐convection mass transfer problem are referred to as conjugated Graetz problems and solved analytically in this work by using an eigenfunction expansion in terms of power series for the homogeneous part and an asymptotic solution for the inhomogeneous part. The theoretical predictions of mass transfer efficiency improvement in double‐pass, parallel‐plate mass exchangers are obtained by suitably adjusting the permeable membrane location. They are represented graphically and compared with the results from an open duct of a single‐pass operation (without a permeable membrane inserted). The increment of power consumption is also discussed.