碳纳米管基复合吸附剂的制备及其吸附性能

为了解决碳纳米管(CNTs)在吸附水中污染物时易聚集、难分离的问题,本文采用静电自组装技术将碳纳米管固定化在具有微米级粒径的碳酸钙颗粒表面,设计制备了壳-核结构的CNTs基复合吸附剂.实验考查了不同碳纳米管分散体系对复合吸附剂制备的影响,并采用Zeta电位、拉曼光谱、扫描电镜等手段对复合吸附剂的制备过程和结构进行表征,探讨了制备的碳纳米管基复合吸附剂对菲的吸附性能.结果发现,复合吸附剂对菲的吸附能力随CNTs载量的增加而增大,CNTs标化的吸附系数则随CNTs载量的增加而下降,碳纳米管是复合吸附剂的主要吸附位点.     

某型直升机尾减速器从动机匣腐蚀故障分析及预防对策研究

目的分析某型直升机尾减速器从动机匣腐蚀故障原因,建立预防该类腐蚀故障问题的处理方法。方法通过腐蚀故障机基本信息分析,腐蚀故障部位结构、材料和腐蚀形貌分析,得出腐蚀故障原因,采取"原位"处理方式建立该类腐蚀故障处理方法。结果某型直升机尾减速器从动机匣安装面有异种金属接触和凹陷型结构,并承受交变载荷,易发生腐蚀故障,部队外场维护只能通过检查和监控延缓腐蚀进程,解决该问题需通过"湿装配"的密封剂处理技术和螺栓表面防护加强方法。结论采取机上原位进行尾减速器从动机匣螺栓固定端面"湿装配"密封处理和螺栓外表面防护涂层加强处理,能够防止电解液进入螺栓固定端面和螺栓孔内部,达到腐蚀预防的目的。     

广西苍梧马尾松林和大叶栎林的火行为比较

马尾松(Pinus massoniana)是中国南方大面积造林的树种,也是抗火能力最弱的树种。研究了广西苍梧11龄马尾松用材林和4龄大叶栎萌芽林在正常冬季和干旱夏季情景下的火行为,用behaveplus计算了火线强度、蔓延速度、树冠火可能性等参数。结果表明,两种林分在干旱夏季的火行为高于在正常冬季的火行为。无论是在正常冬季还是在干旱夏季,都没有出现马尾松可燃物模型的火行为一致高于大叶栎可燃物模型的情况;天气、地形、可燃物床结构对可燃物含水率有很大影响,而含水率是火行为的决定因素。虽然大叶栎被划分为难燃树种,大叶栎萌芽林的火行为高于成年大叶栎乔木林,苍梧大叶栎萌芽林在极端干旱的夏季情景有被火把点燃的可能性。如果将大叶栎萌芽林作为防火林带使用,需要经常清除林下枯枝落叶,割除黑莎草,减少细小可燃物。     

北京西山森林潜在火行为及防火林带有效宽度分布研究

可燃物类型及其栽量分布是决定林火行为的重要因素.以北京西山试验林场魏家村分场为研究区域,根据样地调查和森林清查数据对可燃物类型进行分类,并对可燃物载量的空间分布进行研究.根据历史气象数据确定当地平均最大风速平均值为3.6m/s,平均最大风速的最大值为14m/s,在此情景下,结合DEM数据和可燃物数据对研究区域的林火强度进行计算,并对防火林带的有效参数进行确定.     

The influence of hot particle contamination on Sr and Cs transfers to milk and on time-integrated ingestion doses

Most models for transfers of radionuclides through the food chain typically assume that the radioactivity is initially deposited in chemically available forms. It is known, however, that releases of radionuclides in the form of hot particles may significantly influence their environmental transfers and uptake to the food chain. This study presents models for time changes in ⁹⁰Sr and ¹³⁷Cs in milk which incorporate hot particle contamination using observed rates of hot particle dissolution following the Chernobyl accident. A general equation is presented for the influence of hot particles on overall ingestion doses. As expected from previous work, fallout of hot particles significantly influences time changes in radionuclide activity concentrations in foodstuffs. It is also shown that incorporation of radionuclides in hot particles influences time-integrated ingestion doses. For a situation in which a large proportion (90–100%) of fallout is in slowly dissolving hot particles, time-integrated ingestion doses from ⁹⁰Sr and ¹³⁷Cs are reduced by a factor of approximately two compared to the case where all radioactivity is deposited in bioavailable forms. However, the influence of rapidly dissolving hot particles on time-integrated ingestion doses is relatively minor. Remaining significant uncertainties in dose estimates are discussed.     

Biomass waste gasification - can be the two stage process suitable for tar reduction and power generation?

A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100-350 kW_th. The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950 °C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar compound contents confirmed superiority of the two stage gasification system, drastic decrease of aromatic compounds with two and higher number of benzene rings by 1-2 orders. On the other hand the two stage gasification (with overall ER = 0.71) led to substantial reduction of gas heating value (LHV = 3.15 MJ/Nm³), elevation of gas volume and increase of nitrogen content in fuel gas. The increased temperature (>950 °C) at the entrance to the char bed caused also substantial decrease of ammonia content in fuel gas. The char with higher content of ash leaving the second stage presented only few mass% of the inlet biomass stream.     

Numerical Analysis of Heat Transfer and Gas Flow in PEM Fuel Cell Ducts by a Generalized Extended Darcy Model

Abstract

In this work, gas flow and heat transfer have been numerically investigated and analyzed for both cathode/anode ducts of proton exchange membrane (PEM) fuel cells. The simulation is conducted by solving a set of conservation equations for the whole domain consisting of a porous medium, solid structure, and flow duct. A generalized extended Darcy model is employed to investigate the flow inside the porous layer. This model accounts for the boundary-layer development, shear stress, and microscopic inertial force as well. Effects of inertial coefficient, together with permeability, effective thermal conductivity, and thickness of the porous layer on gas flow and heat transfer are investigated.     

Synthesis of calcium phosphate hydrogel from waste incineration fly ash and its application to fuel cell

Waste incineration fly ash was successfully recycled to calcium phosphate hydrogel, a type of fast proton conductor. The crystallized hydrogel from incineration fly ash had a lower electric conductivity and a lower crystallinity than that from calcium carbonate reagent. However, the difference in electric conductivity between these crystallized hydrogels decreases with temperature. This was due to the presence of potassium in the incineration fly ash. The fuel cell with a membrane electrode assembly (MEA) using the calcium phosphate hydrogel membrane prepared from incineration fly ash was observed to generate electricity. The performance of this fuel cell was almost equal to that of a mixture of K₂CO₃ and CaCO₃ reagents; further, the performance of the former was superior to the fuel cell with a perfluorosulfonic polymer membrane at temperatures greater than approximately 85 °C.     

Tar-free fuel gas production from high temperature pyrolysis of sewage sludge

Pyrolysis of sewage sludge was studied in a free-fall reactor at 1000–1400 °C. The results showed that the volatile matter in the sludge could be completely released to gaseous product at 1300 °C. The high temperature was in favor of H₂ and CO in the produced gas. However, the low heating value (LHV) of the gas decreased from 15.68 MJ/N m³ to 9.10 MJ/N m³ with temperature increasing from 1000 °C to 1400 °C. The obtained residual solid was characterized by high ash content. The energy balance indicated that the most heating value in the sludge was in the gaseous product.     

The effects of Orimulsion and Fuel Oil #6 on the hatching success of copepod resting eggs in the seabed of Tampa Bay,Florida

A 3-month microcosm study was conducted to observe the potential effects of two fuels, Orimulsion and Fuel Oil #6, on the hatching success of copepod resting eggs in the seabed of Tampa Bay, Florida. Microcosms were dosed with one of five hydrocarbon treatments via hydrocarbon-coated sand and compared with controls. Acartia tonsa eggs were nonviable in all treatments after only a few weeks of incubation, as evidenced by a marked decline in the abundance of nauplii. However, there was no evidence that exposure to simulated spills of 700 or 7000 ppm of either fuel led to significant increases in resting egg mortality as compared with controls. The results further indicate that, regardless of environmental conditions, resting eggs of A. tonsa do not remain viable in the sediment for extended periods of time.