GaN材料的高速生长对其C污染以及光致发光光谱的影响

利用金属有机化学气相沉积对GaN的高速生长进行了研究.结果表明,随着GaN生长速率的提高,其非故意掺杂的C含量也在提高,并且呈现出良好的线性关系.当生长速率由2μm/h增加至7.2μm/h时,利用SIMS测量发现其GaN中的C含量由2.9×1017增加至5.7×1018 cm-3 .研究表明,N空位的存在与C浓度之间存在紧密的联系。在高氨气分压生长条件下,N空位的浓度也在急剧下降。此时,与具有相近生长速率的常规样品相比,其C含量几乎下降了一个数量级。.光致发光光谱表明,黄带以及蓝带的强度与C污染存在线性关系.这个结果也证实了与C相关的缺陷是导致黄带以及蓝带发光的主要来源。     

碳纤维复合芯导线与钢芯铝绞线的起晕特性对比试验

为研究碳纤维复合芯导线（ACCC）的起晕特性,基于小电晕笼电晕测量系统进行了ACCC-600/71单根导线和LGJ-630/45钢芯铝绞线单根导线起始电晕特性的对比试验。试验结果表明：在干净及人工涂污下,ACCC-600/71导线的起晕电压均要高出LGJ-630/45导线起晕电压,说明ACCC-600/71导线确实能够降低线路损耗,在节能、环保方面具有良好运行性能;表面污秽会降低导线表面粗糙度系数,从而大幅度降低起晕电压,且污秽物颗粒度越大影响程度越高。     

基于DSP2812的绝缘子泄漏电流测控系统的研究

为了实时监测电力系统中绝缘子污秽状况,介绍了一种基于数字信号处理器TMS320F2812的绝缘子泄漏电流测控系统。该系统以数字信号处理能力较强的TMS320F2812为主控芯片,通过外围模块,如实时时钟模块、数据存储模块、数据通信模块、气象传感器模块、泄漏电流传感器模块等对现场环境下绝缘子的泄漏电流进行采集、分析、存储并发送预警信息。上位机软件采用基于VB编写的人机通信接口,实现对系统参数的设定、采集、波形绘制、数据存储等功能。现场试验证明,该系统能远程测量绝缘子泄漏电流并能发出预警,能够精确反映绝缘子的污秽情况。     

Occurrence and traceability of Listeria monocytogenes strains isolated from sheep's milk cheese-making plants environment

The aim of the study was to conduct an extensive survey on Listeria monocytogenes and Listeria spp. environmental contamination in 13 cheese-making plants. A total of 409 environmental and food samples were collected during years 2011–2013. Listeria spp. contamination was observed in all the facilities, while L. monocytogenes was recovered from 12 facilities with a prevalence ranging between 3.0% and 22.6%. Floor drains were the most contaminated sampling sites (48.8% of positive samples), serving as harbourage site for subsequent contamination. Out of 616 isolates, 277 (45.0%) were Listeria innocua, 274 (44.5%) L. monocytogenes, 41 (6.6%) Listeria ivanovii, 14 (2.3%) Listeria welshimeri and 10 (1.6%) Listeria gravyi. Serotyping carried out by PCR and agglutination method for L. monocytogenes revealed that 169 strains (61.7%) were serotype 1/2a, 65 (23.7%) 4b, 20 (7.3%) 1/2b, 10 (3.6%) 3a, 7 (2.5%) 1/2c and 3 (1.1%) 3b. PFGE conducted on L. monocytogenes isolates using AscI and ApaI restriction enzymes, yielded 6 clusters. Two predominant PFGE clusters were observed including respectively 36 and 32 strains. Within cheese-making plants, L. monocytogenes showed wide variability with strains distributed up to 4 different clusters. Pulsotypes isolated from raw milk filter were never detected in the processing environment, indicating that the contamination originated from sources other than raw milk. The isolation of strains with similar profile from different sampling sites, within and among cheese-making plants, indicated the possible transfer of L. monocytogenes contamination along production lines and from one facility to another. Strains recovered from food were confirmed as originating from the processing environment.     

井下混合流体光谱在线分析技术研究

地层流体光谱实时分析技术通过光谱学原理对地层流体进行在线测量,可为地层流体取样提供重要参考依据。针对取样过程中出现的水基泥浆对地层原油污染的情况,提出一种基于近红外光谱分析技术的油水比在线测量方法。通过对3组不同的光谱预处理方式的建模效果进行分析和对比,证明了采用校正后连续光谱进行偏最小二乘法回归建模能够更准确地预测混合流体流经光学窗口时的含油比率。     

Si晶片激光标识码制作技术的研究

Si片标识码在工艺加工管理中起重要作用.传统手写方式存在字体不美观、划痕深及硅渣污染等缺点.鉴于此,采用波长1060 nm光纤激光器进行激光标识码制作.研究中分别改变激光平均输出功率、脉冲频率及扫描速度,借助目视、金相显微镜及动态三维光学轮廓仪来观察标识码清晰程度、污染程度及深浅程度的变化,了解它们与上述参数间相互对应关系.重点解决清晰度与打标深度之间的矛盾,从而得到清晰、清洁且深度满足后续半导体纳米级加工工艺要求的激光标码技术.研究表明:低脉冲频率(20 kHz)下,随平均功率上升,标识码的清晰度逐渐增加,镜检结果显示硅渣的数量及其分布区域增大;高脉冲频率(90 kHz)下,平均功率增加对标识码清晰度的影响不明显,镜检结果没有发现硅渣.扫描频率与清晰度及污染程度成正比关系.扫描速度与打标深度呈反比关系.采用40％平均功率,25 kHz频率,1500 mm/s扫描速度及双线填充字体(TrueType)的工艺条件,所得标识码在目视及镜检下清晰美观,无硅渣污染.轮廓仪测量结果显示字迹深度及边缘凸起均在200 nm以下.经批量产品验证,根据研究成果所开发的工艺技术稳定且对后续工艺无不良影响.目前已取代手写方式.     

How do the plants used in phytoremediation in constructed wetlands,a sustainable remediation strategy,perform in heavy‐metal‐contaminated mine sites?

This review draws on knowledge for the treatment of heavy‐metal leachate in contaminated mine sites. Mine waste rock dumps and tailings generate a continuous stream of metalliferous and saline leachate over the long term. The mining industry has many legacy sites, which have compromised aquatic ecosystems and groundwater because of heavy‐metal contamination. Chemical and engineering methods are available and have been extensively utilised. However, these methods require intensive energy and often produce substantial volumes of secondary waste. We therefore argue in favour of phytoremediation as a sustainable remediation strategy leading towards efficient and sustainable metal removal and immobilisation through constructed wetlands.     

Identification and characterization of metabolic properties of bacterial populations recovered from arsenic contaminated ground water of North East India (Assam)

Diversity of culturable bacterial populations within the Arsenic (As) contaminated groundwater of North Eastern state (Assam) of India is studied. From nine As contaminated samples 89 bacterial strains are isolated. 16S rRNA gene sequence analysis reveals predominance of Brevundimonas (35%) and Acidovorax (23%) along with Acinetobacter (10%), Pseudomonas (9%) and relatively less abundant (<5%) Undibacterium, Herbaspirillum, Rhodococcus, Staphylococcus, Bosea, Bacillus, Ralstonia, Caulobacter and Rhizobiales members. High As(III) resistance (MTC 10–50 mM) is observed for the isolates obtained from As(III) enrichment, particularly for 3 isolates of genus Brevundimonas   (MTC 50 mM). In contrast, high resistance to As(V) (MTC as high as 550 mM) is present as a ubiquitous property, irrespective of isolates' enrichment condition. Bacterial genera affiliated to other groups showed relatively lower degree of As resistance [MTCs of 15–20 mM As(III) and 250–350 mM As(V)]. As(V) reductase activity is detected in strains with high As(V) as well as As(III) resistance. A strong correlation could be established among isolates capable of reductase activity and siderophore production as well as As(III) tolerance. A large number of isolates (nearly 50%) is capable of anaerobic respiration using alternate inorganic electron acceptors [As(V), Se(VI), Fe(III), ₃NO²⁻${{\text{NO}}_3}^{2\mathrm{-}}$, ₄SO²⁻${{\text{SO}}_4}^{2\mathrm{-}}$, S₂O₃²⁻${{\text{S}}_2{\text{O}}_3}^{2\mathrm{-}}$]. Ability to utilize different carbon sources ranging from C2–C6 compounds along with some complex sugars is also observed. Particularly, a number of strains is found to possess ability to grow chemolithotrophically using As(III) as the electron donor. The study reports for the first time the identity and metabolic abilities of bacteria in As contaminated ground water of North East India, useful to elucidate the microbial role in influencing mobilization of As in the region.     

Adsorption of Zn(II) in Oxisols as affected by selective removal of soil fractions

The relative contribution of organic matter, amorphous and crystalline Fe oxides and Al oxides to soil Zn adsorption was evaluated in contaminated and uncontaminated Brazilian soils. Soil samples were equilibrated with Zn solutions and Zn adsorption was determined using the Langmuir adsorption isotherm. The Fe and Al oxides (non‐silicated clays) and the organic matter contents of the soils were the main contributors to the variation in Zn adsorption. The Zn maximum adsorption capacity in the soil with the greatest sand and organic carbon contents was higher than in the higher clay content soil, which was second in organic carbon content. Related to the whole soil samples, as the soil organic matter was removed, the Zn maximum adsorption capacity decreased in most of the observations. The removal of Fe and Al oxides decreased the soil Zn maximum adsorption capacity in some cases and increased it in others, with no clear variation in the pathway. For both whole soil and soil fractions, the isotherms for Zn adsorption to soil, fitted to the Langmuir equation, showed two linear portions or pathways (Part I and Part II). The bonding energy coefficient was higher in Part I (related to specific chemical adsorption) than in Part II (related to electrostatic interactions), which suggests a higher affinity between Zn and soil particles in Part I as compared with Part II.     

石灰、粉煤灰改性对盐渍土吸附石油污染物行为的影响

有效调控污染物的运移是实现污染土工程再利用的前提。考虑石油污染盐渍土的特殊性及工程利用的力学需求,优选石灰和粉煤灰为改性材料,结合静态动态试验,研究石灰和粉煤灰对滨海盐渍土中石油污染物的吸附解吸行为的影响。结果表明:单独的石灰和粉煤灰,对石油污染物的吸附率分别为26%和14%,两者联合作用时,吸附率提高到39%,在盐渍土中加入石灰和粉煤灰可有效提高对石油污染物的吸附量,加快吸附稳定速率;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油的吸附动力学均符合Lagergren二级动力学非线性方程,联合作用可使吸附平衡时间由400min缩短至60min;石灰、粉煤灰有利于吸附赋存于土颗粒孔隙中未被盐渍土颗粒吸附的呈自由态的石油;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油污染物的吸附等温线均为非线性Freundlich模式;石油被解吸的能力依次为盐渍土粉煤灰+盐渍土石灰+盐渍土石灰+粉煤灰+盐渍土,石灰+粉煤灰对石油污染物的吸附以化学吸附为主,具有不可逆性,有助于缓解环境温度的影响,增强稳定性。