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261.
陕西不同区域接地逆温特征分析 总被引:1,自引:0,他引:1
根据近年开展污染气象观测整理计算的33个项目54期有关边界层小球测风和低探观测资料,分析了陕西省冬季和夏季接地逆温强度及厚度区域分布特征,不同区域接地逆温最大厚度出现时风速廓线和温度廓线特征。分析表明:陕西省接地逆温以西安、咸阳和宝鸡等大城市周围,工业区以及陕北长城沿线荒漠区最为强盛,太白山区及秦巴山区最弱,山区、丘陵地带弱于平原地区,冬季强于夏季;接地逆温最大厚度出现时,地面风速较小,大气层接稳定,陕北长城沿线荒漠区大气水平扩散能力较强,陕南山区次之,关中城市工业区最弱。 相似文献
262.
Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) 总被引:1,自引:0,他引:1
Chad D. Vecitis Hyunwoong Park Jie Cheng Brian T. Mader Michael R. Hoffmann 《Frontiers of Environmental Science & Engineering in China》2009,3(2):129-151
Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment
technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate
(PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment
technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration
of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition
have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic
oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This
paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal
PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and
available degradation time. 相似文献
263.
Chad D. VECITIS Hyunwoong PARK Jie CHENG Brian T. MADER Michael R. HOFFMANN 《Frontiers of Environmental Science & Engineering》2009,3(2):129-151
Fluorochemicals (FCs) are oxidatively recalcitrant, environmentally persistent, and resistant to most conventional treatment technologies. FCs have unique physiochemical properties derived from fluorine which is the most electronegative element. Perfluorooctanesulfonate (PFOS), and perfluorooctanoate (PFOA) have been detected globally in the hydrosphere, atmosphere and biosphere. Reducing treatment technologies such as reverses osmosis, nano-filtration and activated carbon can remove FCs from water. However, incineration of the concentrated waste is required for complete FC destruction. Recently, a number of alternative technologies for FC decomposition have been reported. The FC degradation technologies span a wide range of chemical processes including direct photolysis, photocatalytic oxidation, photochemical oxidation, photochemical reduction, thermally-induced reduction, and sonochemical pyrolysis. This paper reviews these FC degradation technologies in terms of kinetics, mechanism, energetic cost, and applicability. The optimal PFOS/PFOA treatment method is strongly dependent upon the FC concentration, background organic and metal concentration, and available degradation time. 相似文献
264.
Turbulent velocity profile in fully-developed open channel flows 总被引:2,自引:0,他引:2
Hossein Bonakdari Frédérique Larrarte Laurent Lassabatere Claude Joannis 《Environmental Fluid Mechanics》2008,8(1):1-17
The determination of velocity profile in turbulent narrow open channels is a difficult task due to the significant effects
of the anisotropic turbulence that involve the Prandtl’s second type of secondary flow occurring in the cross section. With
these currents the maximum velocity appears below the free surface that is called dip phenomenon. The well-known logarithmic
law describes the velocity distribution in the inner region of the turbulent boundary layer but it is not adapted to define
the velocity profile in the outer region of narrow channels. This paper relies on an analysis of the Navier–Stokes equations
and yields a new formulation of the vertical velocity profile in the center region of steady, fully developed turbulent flows
in open channels. This formulation is able to predict time averaged primary velocity in the outer region of the turbulent
boundary layer for both narrow and wide open channels. The proposed law is based on the knowledge of the aspect ratio and
involves a parameter CAr depending on the position of the maximum velocity (ξdip). ξdip may be derived, either from measurements or from an empirical equation given in this paper. A wide range of longitudinal
velocity profile data for narrow open channels has been used for validating the model. The agreement between the measured
and the computed velocities is rather good, despite the simplification used. 相似文献
265.
为明确空中交通管理风险对航空器适航试飞活动不安全事件的影响,首先,依据航空器试飞科目绘制相应飞行剖面;其次,基于试飞活动飞行剖面,分析管制单位试飞保障流程,提取管制运行风险对试飞活动的影响因素;采用事故树分析法(FTA)分析事故发展过程,将事件和逻辑关系映射至贝叶斯网络(BN),依据国内外民航空管不安全事件分类统计结果... 相似文献
266.
Vertical Profile of Acid Volatile Sulfide (AVS) and Risk Assessment of Sediments from Baihua Lake,China 总被引:1,自引:0,他引:1
Acid volatile sulfide (AVS), simultaneously extracted metals (SEMs), and total concentrations of trace elements (Cu, Cd, Pb, Zn, Ni, Hg, As, and Cr) were studied in sediment cores from Baihua Lake in southwest China. The molar ratios of SEMs to AVS for all samples were lower than 1.0 except for the 25- to 30-cm layer of the sample collected at location YPZ, indicating that the heavy metals were currently not significantly bioavailable as a whole to benthic organisms. Based on the sediment quality guidelines and the potential ecological risk assessment, Hg presented a high ecological risk for the water body. 相似文献
267.
Although most of jet fuels are currently made from petroleum, nonfood oilseeds such as flax and canola seeds may be an alternative for renewable jet fuel production in the near future. Vegetable oils produced from those oilseeds can be upgraded to liquid hydrocarbons to produce renewable jet fuels. The production efficiency and cost are heavily relied on the vegetable oil fatty acid profile (FAP). Previous research indicated that vegetable oil FAP is affected by oilseed species and oil extraction conditions. Cold press oil extractions from flax and canola seeds were conducted. The effect of the frequency controlling the screw rotating speed on the oil extraction efficiency and quality was discussed. Characterization of the vegetable oils produced, including density, pH value, viscosity, moisture, element component, heating value and FAP, was carried out. The residual oil contents left in the cold press meals were also determined. The results show that the oil extraction efficiency of oilseeds increased when the frequency decreased. For flax and canola seeds, their highest oil extraction efficiency was the same (81.0%), which was both obtained at 15 Hz. The cold press frequency had a minor influence on the FAPs of flax oils. However, the FAPs of canola oils produced at 15 Hz were different from those produced at 20 Hz and 25 Hz to some extent. The main fatty acid in flax and canola oils was linolenic acid and erucic acid, respectively. 相似文献
268.
O.M. Popoola 《International Journal of Green Energy》2016,13(14):1473-1482
Most practices currently adopted in modeling the presence of people in residential houses do not reflect the complexity of the impact occupants have on lighting loads. Hence the needs to contribute a methodology, that will be able to look into such characteristics. This study entailed the use of adaptive Neuro Fuzzy inference system (ANFIS) for estimation and prediction of lighting load usage profile for energy and demand side management initiatives. Results obtained showed a better correlation analysis and root mean square error (RMSE) in contrast to the regression method model. This shows that ANFIS model has good prediction accuracy capability. 相似文献
269.
Alya Limayem Robert Scott Donofrio Chao Zhang Edward Haller Michael G. Johnson 《Journal of environmental science and health. Part. B》2013,48(11):827-832
The multidrug resistant Enterococcus faecium (MEF) strains originating from farm animals are proliferating at a substantial pace to impact downstream food chains and could reach hospitals. This study was conducted to elucidate the drug susceptibility profile of MEF strains collected from poultry products in Ann Arbor, MI area and clinical settings from Michigan State Lab and Moffitt Cancer Center (MCC) in Florida. Presumptive positive Enterococcus isolates at species level were identified by Matrix Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) analysis. The antibiotic susceptibility profile for both poultry and clinical strains was determined by the Thermo Scientific's Sensititre conform to the National Committee for Clinical Laboratory Standards (NCCLS) and validated via quantitative real-time PCR (qPCR) methods. Out of 50 poultry samples (Turkey: n = 30; Chicken: n = 20), 36 samples were positive for Enterococcus species from which 20.83% were identified as E. faecium. All the E. faecium isolates were multidrug resistant and displayed resistance to the last alternative drug, quinupristin/dalfopristin (QD) used to treat vancomycin resistant E. faecium (VRE) in hospitals. Results indicate the presence of MEF strains in food animals and clinical settings that are also resistant to QD. 相似文献
270.
As an effort to better utilize the microbial fuel cell (MFC) technology, we previously proposed an innovative MFC system named M2FC consisting of ferric-based MFC part and ferrous-based fuel cell (FC) part. In this reactor, ferric ion, the catholyte in the MFC part, was efficiently regenerated by the FC part with the generation of additional electricity. When both units were operated separately, the ferric-based MFC part produced approximately 1360 mW m−2 of power density with FeCl3 as catholyte and Fe-citrate as anolyte. The ferrous-based FC part with FeCl3 as catholyte and Fe-EDTA as anolyte displayed the highest power density (1500 mW m−2), while that with ferricyanide as catholyte and Fe-noligand as anolyte had the lowest power density (380 mW m−2). The types of catholytes and chelating complexes as anolyte were found to play important roles in the reduction of ferric ions and oxidation of ferrous ion. Linear sweep voltammetry results supported that the cathode electrolytes were electrically active and these agreed well with the M2FC reactor performance. These results clearly showed that ligands played critical role in the efficiency and rate for recycling iron ion and thus the M2FC performance. 相似文献