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101.
《Water research》1986,20(7):871-876
The removal and inactivation of indigenous viruses for individual water treatment processes were investigated both in a pilot (3 m3 h−1) and a full-scale (4000 m3 h−1) plant, treating water from the Seine and Oise rivers respectively.Viruses were recovered by the previously described methods of adsorption-elution using electronegative Balston filters (Joret and Block, 1981) for the pilot plant study or alternatively using either electronegative or electropositive 1 MDS Cuno filters (Sobsey and Glass, 1981) for the full-scale water supply.Depending on the efficiency of filtration, the volumes of water samples concentrated directly in the field varied from 30 to 100 litres for raw, preozonated, stored river water and decanted water, and from 550 to 1000 litres for treated water downstream from the clarification step. BGM cells were used for virus detection by the plaque assay method.During this study, the initial virus concentration in the Seine river water entering the pilot plant, varied from 190 to 1420 PFU/1000 l. The virus removal observed after coagulation-flocculation with 35–50 g m−3 of water aluminum chloride (WAC) (a basic aluminum chloride) and settling, was 31–90% effective (130–390 PFU/1000 l. of decanted water), and did not exceed 1–2 logarithms after sand filtration at a rate of 5 m h−1 (83% of 600–800 samples were positive for viruses, maximum concentration = 80 PFU/1000 l.).The preozonation of river water (0.8 ppm during 2–3 min without residual oxidant) inactivated 64–97% of viruses (maximum viral concentration in preozonated water being 300 PFU/1000 l.). Under these conditions, no viruses could be isolated from samples of 550–1000 litres of sand filtered water.The treatment process for the industrial water supply located at Mery sur Oise was preozonation (0.5–1 ppm for 1 min), storage, coagulation-flocculation, settling, sand filtration, second stage ozonation (1.4–1.6 ppm for 10 min, residual oxidant: traces to 0.3 ppm), activated carbon filtration, postozonation (0.4 ppm free residual for 4 min) and chlorine dioxide (0.1 ppm). Nine series of samples were taken after various stages of treatment and tested for viruses. All samples of raw river water yielded positive results with relatively low numbers (10–146 PFU/1000 l.) compared with the number of enterovirus in the Seine river.The efficiency of preozonation before storage could not be evaluated in this study due to its intermittent operation. Enteroviruses were found in 83% of samples after storage (7–100 PFU/1000 l.), 77% after settling and 55% after sand filtration (3–10 PFU/1000 l.). Enteroviruses were not detected after the second stage ozonation in any of the nine samples. The subsequent postozonation and final treatment with chlorine dioxide serves as an additional barrier to ensure virologically safe drinking water.During studies on pilot and full scale water treatment plants, viral isolates are as follows: ECHO virus (49 and 37% respectively), coxsackie B virus (42 and 49% respectively) and poliomyelitis virus (9 and 14% respectively). 相似文献
102.
《Acta Metallurgica》1987,35(4):989-1000
The effects of microadditions of cerium on the rate of annealing embrittlement, stress relief, and as-quenched magnetic domain structure in three iron-based metallic glasses have been investigated. Ribbons melt-spun from optimally doped castings of composition Fe80B16Si2C2 and Fe80B20 did not embrittle during annealing until the onset of crystallization, whereas Fe78B13Si9 ribbons were unaffected by cerium additions. In the first two glasses optimal doping resulted in the disappearance of quenched-in stresses in the ribbons, as evidenced by an absence of maze domains, and, for the Fe80B20 alloy, a slight enhancement of stress relief rate for small times and temperatures. The effects of doping were qualitatively different in the Fe78B13Si9 glass. We conclude that annealing embrittlement in the first two glasses is an impurity effect, and that the embrittling impurities are oxygen and/or sulfur, the dissolved concentrations of which are strongly reduced by cerium additions. That low concentrations (50–100 at. ppm) of these impurities are sufficient to cause annealing embrittlement suggests that impurity segregation may be involved in the embrittlement process. 相似文献
103.
104.
《International Journal of Impact Engineering》2002,27(5):521-534
Impact of a large meteoroid or a man-made projectile with an atmosphereless cosmic body (Moon, Mercury, asteroid and comet) produces a transient atmosphere. Several physical aspects in the early and late phases of the impact generated vapor plume evolution are considered numerically and analytically. Intensity of light flashes and velocities versus mass distribution function are determined. For a 10 kg mass of impacting meteoroid, the plume intensively interacts with the solar wind in the region with the size of several hundred kilometers. For a 350 kg man-made projectile of the Deep Impact Mission hitting the P9 Comet Temple 1 with the velocity of about 10 km/s the size of the disturbed zone is of the order of 104 km. The expulsion of the interplanetary magnetic field, formation of the collisionless shock wave structure associated with intense electrostatic turbulence, electron heating, and even production of X-rays lasting for several minutes are characteristic features of such impacts. These effects give the basis for new techniques of remote detection of meteoroid impacts. 相似文献
105.
《Materials Science and Engineering: A》2002,322(1-2):132-147
This paper discusses our current understanding of the processes thought to be dominant in the exponential creep regime as well as the implications for creep modeling relating to both power-law and exponential creep regions. The significance and implications of creep controlled by vacancy diffusion along dislocation cores are discussed. It is pointed out that creep substructures, other than subgrains, have been reported in the literature, and a bifurcation diagram is presented to demonstrate how this evolution can occur from an initially homogeneous dislocation substructure. The use of nonlinear dislocation dynamics in creep modeling is advocated to rationalize the observed diversity in the creep substructures. It is demonstrated that the dislocation substructure evolution models can be coupled with a viscoplastic model through the volume fractions of the ‘hard’ and ‘soft’ phases. This coupling is shown to lead to the stress-subgrain size relationship in a simple and a natural way. 相似文献
106.
《Materials Letters》2003,57(13-14):1941-1944
Single crystal of BaGd2Mn2O7 was grown by the floating zone method, and its crystal structure was determined using single crystal X-ray method. This compound has the ordered structure of tilting oxygen octahedron surrounding a central manganese ion (space group P42/mnm). The lattice constants are a=0.55374(8), c=2.0618(1) nm and Z=4. The oxygen octahedron surrounding a central manganese ion is slightly distorted and mutually tilts between the neighboring oxygen octahedrons with an angle of several degrees. These single crystal data confirmed our previous results from the Rietveld analysis of powder X-ray diffraction patterns [J. Alloys Compd. 311 (2000) 69]. 相似文献
107.
《Materials Characterization》2002,48(2-3):189-194
The growth of Si and Ge on silicon nitride surfaces has been investigated using scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and Auger electron spectrometer (AES). In the early stages, Si or Ge nanoclusters appeared irrespective of the different substrates. When annealed, the Si clusters were more stable against coalescence than those of Ge. As these clusters continued to grow, crystalline facets started to form. Both Si and Ge islands grew predominantly with (111)-oriented top facets on the crystalline Si3N4(0001)/Si(111). By contrast, they both grew in random orientation on the amorphous Si3N4 surface. Low-index facets such as (111) and (001) coexisted with high-index facets such as (113). 相似文献
108.
109.
110.
《Nanostructured Materials》1998,10(3):457-464
In this study, silver and iron elements are evaporated simultaneously to form nanocrystalline solid solution particles and then quench to liquid nitrogen temperature. The average composition of the nanocrystalline Ag-Fe system analyzed by scanning electron microscopy with energy-dispersive spectroscopy is close to the gross composition of the raw materials. X-ray diffraction patterns indicate only Ag peaks in those of the nanocrystalline Ag-Fe solid solutions. Transmission electron microscopy images of the Ag-Fe system indicates a mean particle of about 10 nm for these nanocrystalline solid solutions. The magnetic properties of Ag-Fe systems depend on the mean particle's sizes and the concentration of solid solutions. The temperature dependence of the magnetic properties is analyzed and related to the microstructural changes induced by the thermal treatments. Nanocrystalline Ag-Fe system with a Curie temperature of Fe occurs at about 580 °C. The magnetization and remanence of as prepared or after heat-treatment nanocrystalline Ag-Fe solid solutions increase with increasing atomic percentage of iron. 相似文献