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181.
较大含湿量是试验用混凝土结构的一个主要特点。根据火灾试验的特点,在大量调研的基础上,结合作者在试验中的经验教训,对含湿量对混凝土结构抗火性能试验的影响做了阐述,这些影响有关于材料性能的,有关于温度场分布的,有关于混凝土爆裂的,有关于结构变形的,有关于结构耐火极限的。重点分析了含湿量对结构变形的影响,讨论了一些有价值的建议和研究方向,对今后混凝土结构抗火性能试验有较大的借鉴意义。 相似文献
182.
Cheryle Hislop 《The Environmentalist》2007,27(1):119-129
The notion of creating marine protected areas (MPAs) in the high seas has been hailed as “an idea whose time has come”, and
advocates are calling for them to be part of a global representative system to be established by 2012. It is argued in this
paper that embedding the high seas MPA concept in the macro-goal of a global representative system subsumes more pragmatic
and politically acceptable “micro-actions”. Development of politically contentious policy proposals such as high seas MPAs
may have a better chance of success if they proceed by increments and are negotiated outside the limelight of a full scale,
temporally defined global project. The following paper critically analyses the salience of international environmental agreements
in the context of high seas MPAs and suggests a prototype MPA established by means of a negotiated agreement between a small
number of countries which share political will and technological capacity to make a difference. Modelled on the recently implemented
Titanic Accord, the prototypical high seas MPA would allow parties to develop a collaborative, rules-based regime which could be used to
manage the actions of citizens involved in activities that may have a negative impact on the specified area. 相似文献
183.
František Vožeh Antonín Doněk Jan Cendelín Ivana Korelusová Jan Vrba 《The Environmentalist》2007,27(4):501-504
The effect of long-term exposure to high frequency electromagnetic field (HF EMF) on some somatic and neural characteristics
was studied in neurodefective Lurcher mutant (+/Lc) and normal wild type mice (+/+). Both newborn and young adult (3 months)
animals derived from two strains (C3H, B6CBA) were exposed to HF EMF (870 MHz) from 1st to 21st day or from 91st to 120th
day respectively. In animals of both groups and controls we observed the development of body weight. Moreover, in the HF EMF
exposed adult B6CBA animals we studied spatial learning ability, motor functions and the CNS excitability. To investigate
specific energy absorption rate (SAR) in experimental animals we have done the basic 3D calculations of the electromagnetic
energy distribution in the simplified model of the mouse. The HF EMF exposed animals exhibited mild differences of body weight
between them and unexposed controls. The long-term exposure to HF EMF did not significantly influence the ability to learn
in the Morris water maze. However, significant lower swimming speed was found in the irradiated +/Lc as well as lower motor
activity of +/+ in the open field when compared to controls. No significant differences were found between HF EMF irradiated
animals and controls in examination of the CNS excitability and motor functions. 相似文献
184.
S. Hellsten U. Dragosits C. J. Place T. H. Misselbrook Y. S. Tang M. A. Sutton 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):3-13
Most ammonia (NH3) emission inventories have been calculated on an annual basis and do not take into account the seasonal variability of emissions
that occur as a consequence of climate and agricultural practices that change throughout the year. When used as input to atmospheric
transport models to simulate concentration fields, these models therefore fail to capture seasonal variations in ammonia concentration
and dry and wet deposition. In this study, seasonal NH3 emissions from agriculture were modelled on a monthly basis for the year 2000, by incorporating temporal aspects of farming
practice. These monthly emissions were then spatially distributed using the AENEID model (Atmospheric Emissions for National
Environmental Impacts Determination). The monthly model took the temporal variation in the magnitude of the ammonia emissions,
as well as the fine scale (1-km) spatial variation of those temporal changes into account to provide improved outputs at 5-km
resolution. The resulting NH3 emission maps showed a strong seasonal emission pattern, with the highest emissions during springtime (March and April) and
the lowest emissions during summer (May to July). This emission pattern was mainly influenced by whether cattle were outside
grazing or housed and by the application of manures and fertilizers to the land. When the modelled emissions were compared
with measured NH3 concentrations, the comparison suggested that the modelled emission trend corresponds fairly well with the seasonal trend
in the measurements. The remaining discrepancies point to the need to develop functional parametrisations of the interactions
with climatic seasonal variation. 相似文献
185.
186.
废高磁合金钢中钴、镍的分离和利用 总被引:1,自引:0,他引:1
用硫酸、盐酸和硝酸溶解废高磁合金钢、并将Fe^2 氧化为Fe^3 。先用黄铁矾法除去大部分铁,用尿素除去少量的铁及铝、钛、铜;最后在NH3-NH4Cl体系中分离钴、镍,并制成相应的盐。钴、镍的回收率分别国81.5%、89.7%。 相似文献
187.
Spraying water under high pressure generates charge-separating processes. While cleaning tanks and vessels in which an explosive atmosphere is present, an explosion may occur in the event of a resulting discharge. Water forms electrical double layers at the phase boundaries. Mechanical separation processes dissolve the water into many drops. This leads to charge separation and the charging of the sprayed water. The mechanical separation processes include water exiting from the nozzle, hydrodynamic instability in the jet and impact with an obstacle. Given that water has many charge carriers, the charge is stronger than with solvents. Whether the charges and the resulting discharges are potentially capable of igniting an explosive atmosphere must be investigated. The aim of this research is to define the quantity and polarity of the electrostatic charges of sprayed water under high pressure. Different measurement techniques and methods are used to enable mutual validation and to generate verified measurement results of the electric field and the potential. Water of different electrical conductivity is sprayed in free space and into a grounded conductive 1 m3 vessel. Design changes to the vessel allow centric or oblique spraying. The result is intended to extend the scope of application of the German regulation TRGS 727 and the international IEC TS 60079-32-1, which refer to ignition hazards due to electrostatic charging. This project is funded by the DGUV (German Social Accident Insurance) and partners from industry. 相似文献
188.
Safety studies for production and use of hydrogen reveal the importance of accurate prediction of the overpressure effects generated by delayed explosions of accidental high pressure hydrogen releases. Analysis of previous experimental work demonstrates the lack of measurements of turbulent intensities and lengthscales in the flammable envelope as well as the scarceness of accurate experimental data for explosion overpressures and flame speeds. AIR LIQUIDE, AREVA STOCKAGE ENERGIE and INERIS join in a collaborative project to study un-ignited and ignited high pressure releases of hydrogen.The purpose of this work is to map hydrogen flammable envelopes in terms of concentration, velocity and turbulence, and to characterize the flame behaviour and the associated overpressure. These experimental results (dispersion and explosion) are also compared with blind FLACS modelling. 相似文献
189.
A high speed flow visualization experiment was conducted to characterize the boiling induced turbulence when a cryogenic liquid is released on water. The advective transport of turbulent structures traversing through the liquid was captured and reconstructed using image processing software to obtain information on velocity components. The numerical results obtained from image processing were used to determine turbulence parameters like turbulent intensity, turbulent kinetic energy and eddy dissipation rate. An interesting aspect of the study was the formation of wavy structures called ‘thermals’ which were characteristic of turbulent convection. The thermals were found to act as a catalyst in increasing heat transfer and turbulence between water and cryogenic pool. The turbulent intensity was influenced by the turbulent velocity and had direct effects on the vaporization flux. Among the turbulence parameters, increase in turbulent kinetic energy resulted in faster vaporization of cryogenic liquid through enhanced mixing, whereas variations in the eddy dissipation rate had weak dependence on vaporization. Additionally, the initial height of cryogenic liquid was also found to strongly affect the vaporization mass flux. 相似文献
190.
农作物秸秆燃烧是大气中黑碳(black carbon,BC)气溶胶的主要来源之一。目前农作物秸秆燃烧排放黑碳的研究主要集中在通过离线样品分析获得的BC排放特征,缺少实时在线排放特征的研究。本研究收集了我国具有代表性的4种农作物秸秆(小麦秸秆、水稻秸秆、玉米秸秆和大豆秸秆),通过在实验室燃烧平台模拟农作物秸秆露天燃烧的过程,利用黑碳仪获得农作物秸秆燃烧过程中BC的实时浓度排放变化;利用质量重建,获得BC在线排放因子。结果表明:农作物秸秆在明燃过程中BC的排放因子较为稳定。通过平均排放因子的计算,获得小麦秸秆、水稻秸秆、玉米秸秆和大豆秸秆的BC排放因子分别为(0.32±0.05) g?kg~(-1)、(0.31±0.13) g?kg~(-1)、(0.31±0.09) g?kg~(-1)和(0.44±0.01) g?kg~(-1)。在排放因子的基础上,结合我国农作物秸秆露天燃烧量,最终建立了2015年我国省级(不含港澳台地区)典型农作物秸秆燃烧的BC排放清单。 相似文献