Three UASB reactors were operated at different salinity levels in order to assess the effects on the granular sludge properties. High levels of activity inhibition were observed at sodium concentrations over 7 g Na(+)/L, which resulted in low applicable organic loading rates and VFA accumulation in reactor effluents. However, either sludge adaptation or selection for saline resistant microorganisms occurred, which could be concluded from the observed increase in the 50% activity inhibitory concentrations of sodium during continuous flow experiments. Changes in Na(+) susceptibility in time are likely to be expected when treating saline wastewaters. The latter was evidenced by the high sodium tolerance of granular methanogenic sludge coming from a full-scale industrial reactor treating such wastewater. High salinity conditions resulted in a reduced granule strength, predicting process instabilities during long term reactor operation. Batch tests showed that high sodium concentrations seemed to displace the calcium from the granular sludge, a factor known to affect anaerobic granules formation. 相似文献
Accurate measurement, inference and modeling techniques are fundamental to Internet topology research. Spatial analysis of the Internet is needed to develop network planning, optimal routing algorithms, and failure detection measures. A first step toward achieving such goals is the availability of network topologies at different levels of granularity, facilitating realistic simulations of new Internet systems. The main objective of this survey is to familiarize the reader with research on network topology over the past decade. We study techniques for inference, modeling, and generation of the Internet topology at both the router and administrative levels. We also compare the mathematical models assigned to various topologies and the generation tools based on them. We conclude with a look at emerging areas of research and potential future research directions. 相似文献
To increase the productivity of knowledge workers, it is necessary to manage their organization so that they are motivated
to collaborate with each other for their synergy. However, it is difficult for managers to grasp the explicit interactions
of workers in the organization all the time. Owing to advanced communications technology, and the reduced size and improved
capabilities of computers, we are able to record group behaviors as logging data in the office. The aim of this study is to
extract features of group behavior from long-range office-logging data. We apply principal component analysis to the data
matrix whose element is the mean travel velocity calculated from an individual’s trajectory per day. The results demonstrate
the feasibility of our approach, since nontrivial informative group features can be extracted. 相似文献
AlthoughTc cannot be found for a liquid-quenched Bi1.6Pb0.4Sr2Ca2Cu3Ox glassy sample, a highTc is found after annealing for 24 h at 1100 K. The maximum offset temperature of the superconducting transition is 113.3 K at 2.2 × 10–2mAmm–2. The maximumTcoff is larger than that (the maximumTcoff is 103.4 K at 2.0 × 10–2 mAmm–2) of sintered specimens before liquid quenching. 相似文献
Discusses three new techniques that were implemented in a CMOS 60-ns 16-Mbit DRAM device. (1) A two-step half-conductive-state technique was used to control the conductivity of latch transistors, thus minimizing the time delay caused by bit-line stray capacitance. (2) The 'split-block row decoder' technique enabled the decoder layout within the 2.9- mu m cell pitch required for 16-Mbit integration density. The three transistors that are required per word line were split into two and one, placed on both sides of each word line, and alternately reversed on each side of the 2-Mbit cell array. (3) Additional dummy cells were added to the vacant spaces resulting from use of a twisted bit-line architecture, which reduces stray capacitance between adjacent bit lines. The overhead space required for all the dummy cells and twisted bit lines was thus held at 2.6 percent of the entire chip area.<> 相似文献
We describe a most straightforward synthetic method for preparing neurokinin‐1 (NK1) receptor antagonist derivatives by asymmetric hydrogenation of 3‐amido‐2‐arylpyridinium salts using dinuclear iridium complexes with enantiopure diphosphine ligands, affording the corresponding chiral piperidines in high cis‐diastereoselectivity (>95:5) and moderately high enantioselectivity (up to 86%). Deprotection treatments afforded the NK‐1 receptor antagonist (+)‐CP‐99,994 (83% ee). In addition, we observed unique additive effects of 10‐camphorsulfonic acid in the asymmetric hydrogenation of 3‐amido‐2‐arylpyridinium salts.
The iron(III) chloride‐catalyzed Friedel–Crafts arylation of 4‐aryl‐4‐methoxy‐2,5‐cyclohexadienones, which were easily prepared by the phenyliodine(III) diacetate (PIDA)‐mediated oxidation of 4‐arylphenols in methanol, proceeded site‐selectively to form meta‐terphenyl (2,4‐diarylphenol) derivatives in good yields. The subsequent PIDA‐mediated oxidation and iron(III) chloride‐catalyzed Friedel–Crafts arylation of the resulting products gave the corresponding 2,4,6‐triarylphenol derivatives. The present method provides useful highly substituted polyarylated compounds.
Filter-based absorption photometers have been widely used to measure mass concentrations of black carbon (BC) by measurement of the absorption coefficient of BC. In these techniques, correction for the effect of multiple scattering by the filter medium is necessary, even if only BC particles are extracted by evaporating co-existing volatile compounds using a heated inlet. The correction depends on particle size, because it varies with the aerosol penetration depth into the filter. The size dependence has not, however, been taken into account in previous studies. For the first time, we quantify the particle size dependence of the sensitivities of two filter-based photometers, PSAP and COSMOS, using mono-disperse nigrosin particles, which were generated by the combination of a differential mobility analyzer and an aerosol particle mass analyzer. At diameters smaller than 200 nm, the absorption coefficients measured by PSAP and COSMOS were much larger than those calculated by Mie theory. The size-dependent correction factors for PSAP and COSMOS are determined by comparing the observed absorption coefficients at a flow rate of 0.7 standard liter per minute with those calculated by Mie theory. The correction factors to the mass absorption cross-section are also estimated for typical size distributions of ambient black carbon particles. The new factors reduce the mass absorption cross-sections measured by PSAP and COSMOS by 28–36% for typical ambient black carbon particles observed with an inlet heated to 400 °C. 相似文献