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排序方式: 共有912条查询结果,搜索用时 10 毫秒
71.
In Luxembourg the largest drinking water production plant treating reservoir water with conventional technology including ozonation is in operation since 1969. Its maximum capacity is 64,000 m3/d. After 40 years of operation the need for both modernizing and extension of capacity to 100,000 m3/d emerged. Nowadays, due to new developments in technology and research it is possible to assess the water treatment processes more effectively with regard to current and future requirements. Against this background, membrane processes combined with conventional and advanced processes were identified as potential option and long term pilot-scale tests were started in June 2008. Different treatment process schemes all including membranes are investigated in a one year pilot plant period. Various treatment steps such as different pre- and post-treatment steps, various membranes and membrane materials and also conventional treatment steps are compared and assessed. 相似文献
72.
Athanasios Stefanou Georges Gielen 《Analog Integrated Circuits and Signal Processing》2010,65(2):185-195
This paper presents a model to evaluate the impact of substrate noise on a CMOS regenerative comparator and moreover to predict
the resulting performance degradation of a flash analog-to-digital (A/D) converter. The proposed approach initially relates
substrate noise to the induced timing uncertainty of the comparator by means of an analytical linear model. In particular,
the analysis first focuses on analyzing and expressing the resulting non-uniform sampling distortion in regenerative comparators
in the presence of a deterministic ground bounce. Two sources of distortion are identified and evaluated: the input-dependent
and the substrate noise-dependent one. For each error contributor, the analysis investigates two cases of timing error, based
on the frequency correlation of the interfering signal with the sampling clock. The properties (number and power of distortion
tones) of the sampling error spectrum are found to be highly dependent on the spectral content of the interfering signal and
the sampling clock, while the model captures accurately the induced distortion. Subsequently, the linear model is extended
to estimate the degradation of flash A/D converters and is utilized to predict the performance of practical flash and time-interleaved
converters in the presence of substrate noise. 相似文献
73.
J. Jacquens D. Farrusseng S. Georges J.‐P. Viricelle C. Gaudillre G. Corbel P. Lacorre 《Fuel Cells》2010,10(3):433-439
The mixed ionic–electronic conductivity under dilute hydrogen, the stability and the catalytic activity under propane:air type mixtures of a series of LAMOX oxide‐ion conductors have been studied. The effect of exposure to dilute hydrogen on the conductivity of the β‐La2(Mo2 – yWy)O9 series at 600 °C depends on tungsten content: almost negligible for the highest (y = 1.4), it is important for La2Mo2O9 (y = 0). In propane:air, all tested LAMOX electrolytes are stable at 600–700 °C, but get reduced when water vapour is present. La2Mo2O9 is the best oxidation catalyst of the series, with an activity comparable to that of nickel. The catalytic activity of other tested LAMOX compounds is much lower, (La1.9Y0.1)Mo2O9 showing a deactivation phenomenon. These results suggest that depending on composition, La2(Mo2 – yWy)O9 compounds could be either electrolytes in single‐chamber SOFC and dual‐chamber micro‐SOFC (y = 1.4) or anode materials in dual‐chamber SOFC (low y) or oxidation catalysts in SOFCs operating with propane (y = 0). 相似文献
74.
Morin G Juillot F Casiot C Bruneel O Personné JC Elbaz-Poulichet F Leblanc M Ildefonse P Calas G 《Environmental science & technology》2003,37(9):1705-1712
The oxidation of Fe(II) in acid mine drainage (AMD) leads to the precipitation of Fe(III) compounds which may incorporate toxic elements, such as arsenic (As), within their structure or adsorb them at their surface, thus limiting their mobility. The present work provides evidence for spatial and seasonal variations of microbial activity that influence arsenite oxidation and As immobilization in the heavily contaminated AMD from the Carnoulès mine, Gard, France ([As III] = 80 to 280 mg x L(-1) in the acidic spring draining the waste-pile). In the first tens of meters of the AMD, the rapid oxidation of Fe(II) leads to the coprecipitation of large amounts of As with Fe(III) in bacterial mats. XRD, XANES, and SEM analyses of sediments and stromatolite samples revealed the unusual formation of As(III)-rich compounds, especially nanocrystalline tooeleite, Fe6(AsO3)4(SO4)(OH)4 x 4H2O, a rare ferric arsenite sulfate oxy-hydroxide mineral, together with XRD-amorphous mixed As(III)/As(V)-Fe(III) oxy-hydroxide compounds. In the wet season, the suspended sediments of the upstream zone essentially consist of tooeleite associated with am-As(III)-Fe(III) oxy-hydroxides, while am-As(V)-Fe(III) oxy-hydroxides, having As:Fe molar ratios as high as 0.6-0.8, dominate in the dry season. Comparing natural and bioassay samples revealed that the formation of As(III)-rich compounds in the wet season may be related to the metabolic activity of bacterial strains able to oxidize Fe(II) but not As(III). One of these strains, having an Acidithiobacillus ferrooxidans genotype, has been isolated from the Carnoulès AMD. In contrast, the formation of As(V)-rich compounds in the dry season can be related to both biotic and abiotic oxidation of As(III) to As(V). Some Thiomonas strains isolated from the Carnoulès AMD were shown to be able to catalyze the oxidation of As(III) to As(V) in solution. Therefore, they can promote the formation of mixed As(V)-Fe(III) oxy-hydroxides, provided enough Fe(II) oxidizes. These results yield a better understanding of natural processes at this site and may help in designing efficient As-removal processes. 相似文献
75.
Several glasses synthesized by sol–gel route and based on the BaO–B2O3–X–Al2O3–SiO2 (X = CaO, MgO) glass system have been investigated to evaluate their applicability as sealant for solid oxide fuel cell (SOFC). Chemical interactions with K41X stainless steel and hydrogen‐tightness of these materials were evaluated after operations at high temperatures over 1,000 h in air atmosphere. Formation of a new phase at the steel–glass interface and formation of porosity in the glass were observed and determined as critical problems over mid‐term operations. The role of MgO is important to obtain a gas‐tight sealing. Application of the glass paste without binder addition was performed in order to avoid possible residual porosity related problems. The best glass was finally used as sealant between anodic and cathodic compartments in complete SOFCs operated at 760 and at 800 °C. Open circuit voltages and power densities of the cells were recorded during the first hours of operation. 相似文献
76.
The volatiles released from several aphid and host plant species, alone or associated, were studied for their infochemical role in prey location. Using a four-arm olfactometer, the attraction of several combinations of three aphid (Myzus persicae, Acyrthosiphon pisum, and Brevicoryne brassicae) and three plant (Vicia faba, Brassica napus, and Sinapis alba) species toward Adalia bipunctata larvae and adults was observed. Both predatory larvae and adults were attracted only by A. pisum and M. persicae when they were crushed, whatever the host plant. (E)-beta-farnesene, the aphid alarm pheromone, was the effective kairomone for the ladybird. Plant leaves alone (V. faba, B. napus, and S. alba) or in association with nonstressed whole aphids (the three species) did not have any attraction for the predator. The B. brassicae specialist aphid is the only prey that was not attracted to A. bipunctata larvae and adults, even if they were crushed. Release of B. brassicae molecules similar to the host plant allelochemicals was demonstrated by GC-MS analysis. The lack of behavioral response of the ladybird at short distance toward the cruciferous specialist aphid was related only to the absence of (E)-beta-farnesene in the aphid prey volatile pattern. 相似文献
77.
78.
Arvind Jayaprakash Jin-Keun Choi Georges L. Chahine Farrel Martin Martin Donnelly Jean-Pierre Franc Ayat Karimi 《Wear》2012,274(1-2):619-629
Cavitation erosion prediction and characterization of cavitation field strength are of interest to industries suffering from cavitation erosion detrimental effects. One means to evaluate cavitation fields and materials is to examine pitting rates during the incubation period, where the test sample undergoes localized permanent deformations shaped as individual pits. In this study, samples from three metallic materials, an Aluminum alloy (Al 7075), a Nickel Aluminum Bronze (NAB) and a Duplex Stainless Steel (SS A2205) were subjected to a vast range of cavitation intensities generated by cavitating jets at different driving pressures and by an ultrasonic horn. The resulting pitted sample surfaces were examined and characterized with a non-contact 3D optical scanner and the resulting damage computer-analyzed. A statistical analysis of the pit population and its characteristics was then carried out. It was found that the various cavitation field strengths can be correlated to the measured pit distributions and that two characteristic quantities: a characteristic number of pits per unit surface area and unit time, and a characteristic pit diameter or a characteristic pit depth can be attributed to a given “cavitation intensity level”. This characterization concept can be used in the future to study the cavitation intensity of the full scale and to develop methods of full scale predictions based on model scale erosion data. 相似文献
79.
Georges Akhras Gouri Dhatt 《International journal for numerical methods in engineering》1976,10(4):787-797
An automatic algorithm is presented for reducing the bandwidth of symmetric sparse connectivity matrices. The procedure takes an arbitrary input sequence and creates an optimal bandwidth for complex network systems by renumbering the node labels. Thus, considerable improvement for computer storage and time is achieved in the solution of the systems. A large number of examples is presented to demonstrate the reliability and the efficiency of the method. 相似文献
80.