Results 1 - 10 of 8789
Results 1 - 10 of 8789. Search took: 0.039 seconds
|Sort by: date | relevance|
[en] The liquid wastes generated by the reprocessing of spent fuel can be converted into solid form by using several known processes. When the wastes contain nitrates and nitrites large quantities of noxious nitrogen oxide gases are formed, which are at present released to the atmosphere. Their evolution may be suppressed by adding urea to the waste solution before the solution is heated, so that upon heating the urea reacts wth the nitrates and nitrites to evolve elemental nitrogen, carbon dioxide and ammonia. The addition of urea does not add any additional materials to the solids being formed from the waste solution. A slight excess of a stoichiometric amount of urea relative to the nitrates and nitrites present is added to the liquid waste, and the solution is heated to at least 1300 C while bubbling carbon dioxide through the solution. This method can be used with the pot calcination process of waste solidification, or in the fluidized bed calcination process. (LL)
[en] Positron-annihilation lifetimes in nitrogen dioxide and nitric oxide gases are carefully determined. Nitrogen is used as a dilutant. The free-positron-annihilation rate in units of the effective number of electrons per molecule Z/sub eff/ for nitrogen dioxide as a mixture of dimers and monomers is determined to be 720 to 1090 and the free-positron-annihilation rate for nitric oxide is Z/sub eff/ = 34. The positronium quenching rate in nitrogen dioxide gas is very high, and the conversion reaction by NO2 is found to be mainly responsible for the quenching. The quenching rate is determined to be 460D nsec-1 amagat-1, where D is the partial density. The positronium quenching rate in nitric oxide is determined to be only about 0.15D nsec-1 amagat-1, and it changes with the concentration of nitrogen. (auth)
[en] Complete text of publication follows. In this paper we use the ERA-40 and ECMWF operational surface level air temperature data sets from 1957 to 2006 to examine polar temperature variations during years with different levels of geomagnetic activity, as defined by the Ap index. Previous modelling work has suggested that NOx produced at high latitudes by energetic particle precipitation can eventually lead to detectable changes in surface air temperatures (SATs). We find that during winter months, polar SATs in years with high Ap index are different than in years with low Ap index; the differences are statistically significant at the 2-sigma level and range up to about ±4.5 K depending on location. The temperature differences are larger when years with wintertime Sudden Stratospheric Warmings are excluded. We take into account solar irradiance variations, unlike previous analyses of geomagnetic effects in ERA-40 and operational data. Although we can not conclusively show that the polar SAT patterns are physically linked by geomagnetic activity, we conclude that geomagnetic activity likely plays a role in modulating wintertime surface air temperatures. We tested our SAT results against variation in the Quasi Biennial Oscillation, the El Nino Southern Oscillation and the Southern Annular Mode. The results suggested that these were not driving the observed polar SAT variability. However, significant uncertainty is introduced by the Northern Annular Mode and we cannot robustly exclude a chance linkage between sea surface temperature variability and geomagnetic activity.
[en] Verticle column amounts of NO2 have been measured using visible spectroscopy from September 1994. We will compare the seasonal change in the column amounts between Ny-Alesund (Spitsbergen, Norway 79 degrees N) which is usually inside the polar vortex, and Fairbanks (Alaska 65 degrees N) which usually is outside polar vortex. Decreasing daylength in the fall causes a rapid decrease in the vertical column of NO2 due to night-time conversion of NO2 to N2O5, slower increase in the NO2 amounts at Ny-Alesund in the spring may be caused by reduction in the N2O5 reservoir in the arctic night due to heterogenous conversion of N2O5 to HNO3 on sulfate aerosols (PSC's)
[en] Based on a literature study the state of the art regarding the title subject is presented and discussed. From the small-scale investigations carried out so far it appears that there is a considerable potential for advanced reburning to reduce NOx emissions. Reductions of 80% are reported. However, there are still problems to be solved, regarding the chemistry and the optimal configuration of the process. It is concluded that further small-scale research is needed to be able to carry out a large-scale project to demonstrate the process
[en] Exhaust Gas Recirculation (EGR) method has already shown its benefits on controlling NOx emissions in internal combustion engines. By using EGR, power reduction and increase of other pollutants may be appeared; therefore use of this method needs an accurate regulation system limiting EGR cylinder-to-cylinder maldistribution. On the other hand, emission law limitations make engine manufacturers to recycle back blowby gases into the cylinders. As the same reasons, mentioned above, homogeneous distribution of blowby bases show better performance and more emission reduction. Geometrical parameters and injection location of EGR/blowby have substantial effects on homogeneous cylinder-to-cylinder distribution of EGR/blowby. Therefore a numerical simulation of air flow with another species gas (for example CO2 injection inside intake manifold as EGR/blowby) is needed to evaluate the maldistribution quantitatively. In this study, the flow field of compressible and unsteady turbulent flow is solved for different injection locations to compare EGR/blowby maldistribution of each location. Although this method is practicable, it is time consuming because of various injection locations and long solution duration. Furthermore a new method based on particle tracking is proposed which decreases the time and effort needed to find appropriate injection locations. (author)
[en] Highlights: • The first example of inorganic anion-water cluster formation inside the cucurbit[n]uril hydrophobic cavity. • A cyclic water octamer was captured and stabilized generating an inorganic anion-water cluster in the cavity of cucurbituril. • The octameric water cluster is stabilized and linked by two coordinated nitrate anions through hydrogen bonds. • A novel cucurbituril-based half-opened molecular capsule was assembled. • The structural presentation of a water cluster encapsulated in a hydrophobic cavity provides opportunity to study the properties and behavior of water cluster in special small environments. A nitrate-water cluster [(NO3)2(H2O)8]2− confined in the hydrophobic cavity of a cucurbituril complex with Sr2+ has been observed. It represents the first example of inorganic anion-water cluster formation inside the cucurbit[n]uril hydrophobic cavity.
[en] The outlook for small-scale combined heat and power (CHP) in the USA is discussed. Improved technologies and environmental benefits suggest that the market will increase, but regulatory and other barriers are expected to limit applications in the short-term to niche markets. The environmental benefits of small-scale CHP, the market opportunities offered by the deregulation of electric power, environmental regulatory barriers, comparisons of nitrogen oxide emissions, promising emerging technologies (gas microturbines and fuel cells), emerging markets (small manufacturing plants and medium and small commercial/institutional CHP systems) and the need for policies to overcome barriers and spur future growth are considered
[en] Results from recent testing by the Oxygenated Fuels Association (OFA) indicate that oxygen content ceilings on gasoline for the purpose of controlling NOx emissions appear to be unwarranted. OFA Executive Director Jack Murray reported the study findings to the US Environmental Protection Agency in November 1992. The forum for Murray's comments was the EPA's public hearing on the administrator's proposed finding that no control or prohibition on maximum oxygen content of a winter oxygenated gasoline program is necessary under section 211(c)(4)(A) of the Clean Air Act, as amended by the Clean Air Act Amendments of 1990