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排序方式: 共有74条查询结果,搜索用时 15 毫秒
1.
Ostojic R. Catalan Lasheras N. Lucas J. Venturini Delsolaro W. Landgrebe D. 《Applied Superconductivity, IEEE Transactions on》2004,14(2):199-202
The LHC insertions will be equipped with individually powered MQM superconducting quadrupoles, produced in three versions with magnetic lengths of 2.4 m, 3.4 m, and 4.8 m. The quadrupoles feature a 56 mm aperture coil, designed on the basis of an 8.8 mm wide Rutherford-type NbTi cable for a nominal gradient of 200 T/m at 1.9 K and 5390 A. A total of 96 quadrupoles are in production in Tesla Engineering, UK. In this report we describe the construction of the pre-series MQM quadrupoles and present the results of the qualification tests. 相似文献
2.
This paper investigates the remote sensing of height and displacement velocity of turbulent clouds, composed mainly of liquid water, using a combination of simultaneous radiometric and geostationary satellite beacon measurements. Because a radiometer integrates the sky brightness temperature distribution observed within the solid angle subtended by the antenna beamwidth, the paper shows how this process can be modeled as a low-pass filter using the small angle approximation and the frozen-in hypothesis. The 3-dB cutoff frequency of that filter is used in conjunction with the Fresnel frequency of the amplitude scintillations power spectrum to derive the cross-path wind speed and the height of the turbulent layer/cloud. In order to quantify the 3-dB cutoff frequency of the filter-radiometer, a dual aperture radiometer was constructed and was used in conjunction with a ground station receiver monitoring the 39.5-GHz beacon transmissions of ITALSAT F1 and measuring amplitude scintillations. The experimental results derived on cloud heights are then compared with the vertical profiles obtained by a 94-GHz radar, indicating agreement except in those cases where the thickness of the cloud structure becomes important. This aspect is then discussed in the paper and a radiometric definition is given for the cloud height. Finally, the important aspect of instrumentation is described including the effect of the radiation pattern of a radiometer antenna upon the cross correlation and cross spectrum between two coaxial measured antenna temperatures 相似文献
3.
The objective of this study was to assess workers' exposure to bioaerosols in sludge drying units. Simultaneous collection of inhalable dust and airborne biological agents was carried out using rotating cup samplers (CIP 10, Arelco). Sixteen stationary and 30 personal measurements were performed in three drying plants, during summer and winter. Microbial content of air was characterized by high amounts of Gram-negative bacteria, endotoxin, and thermophilic actinomycetes. High differences between exposure levels were observed with regard to workplaces and tasks. Dryers and conveyors in operation were closed, and the monitoring task in the dryer room was associated with low levels of personal exposure, close to background levels. Conversely, cleaning and maintenance of the dryer and conveyors required the equipment to be opened, giving significantly higher task-based personal exposure levels. The fall of dried sludge into indoor containers resulted in high emission and spreading of dust. Mean personal exposure levels to fungi were moderate or low for all tasks. Based on the results of this study, appropriate means of operational control and personal protection are being developed and implemented on sites. 相似文献
4.
Catalan G 《Applied optics》1994,33(10):1907-1915
Approximate formulas are derived for the axial coma resulting from tilt and decenter of a surface and for the spherical aberration resulting from a change in its axial position. These expressions include terms that represent aberrations induced by the subsystem preceding the surface in addition to other terms that are intrinsic contributions from the misaligned surface itself. This separation of the terms gives a simple method of designing a system that is insensitive to a misalignment at a given surface. The method is illustrated by applying it to a two-mirror astronomical telescope with corrector. Two examples are given-one for tilt and the other for despace. In both examples an appreciable reduction in the sensitivity is obtained. The limitations of these solutions and the problem of simultaneous correction for two types of misalignment are examined. 相似文献
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Exercise training-induced changes in sensitivity to endothelin-1 and aortic and cerebellum lipid profile in rats 总被引:2,自引:0,他引:2
Latorre E Morán M Aragonés MD Saborido A Fernández I Delgado J Catalán RE Megías A 《Lipids》2002,37(1):43-52
The purpose of this work was to study whether exercise training induces changes in the lipid profile of rat aorta and nervous
system and in the in vitro intrinsic responsiveness of these tissues to endothelin-1 (ET-1) treatment. The exercise program performed successfully produced
the characteristic metabolic alterations of the trained state. Exercise training induced a large and significant increase
in the levels of both aortic ethanolamine plasmalogens (PlasEtn) and glucosylceramides. In contrast, a decrease of aortic
ceramide and cholesterol levels was evoked by exercise training. ET-1 increased PlasEtn content only in sedentary animals.
An exercise-induced increase in cerebellum levels of ceramides and ceramide monohexosides was found. The cerebellum ceramide
content was increased by FT-1 more noticeably in sedentary rats than in trained animals. In contrast, cerebral cortex was
observed to be largely insensitive to both exercise training and ET-1 treatment. It was concluded that exercise training (i)
induces changes in both vascular and cerebellar lipid profiles, the former being much more pronounced than the latter, and
(ii) diminishes the aortic and cerebellar sensitivity to ET-1 action. 相似文献
8.
R. M. Bowman G. Catalan M. H. Corbett J. M. Gregg 《Journal of Materials Science: Materials in Electronics》2000,11(7):543-547
Pulsed laser deposition (PLD) has been used to fabricate relaxor thin films and thin film capacitors based on the Pb(Mg1/3Nb2/3)O3 system. Best capacitor structures show dielectric constants (r) of 1000 and losses (tan ) 0.02 at 1 kHz at 300 K. Electromechanical investigations show that tensile longitudinal strains of up to 0.2% can be achieved in these films. 相似文献
9.
Quantitative scanning electron microscope (SEM) studies of cement-stabilized waste specimens exposed to a leaching solution at constant pH in the range 4-7 have shown that the acid neutralization capacity (ANC) of the waste matrix is consumed at two consecutive leaching fronts. The first front is associated with the dissolution of portlandite (Ca(OH)2) and the partial reaction of calcium silicate hydrate (CSH) gel. The second front marks the dissolution of Ca-Al hydroxy sulfate minerals. The advancement of the first front is limited by the diffusion of OH- ions from the first front toward the leaching solution. The advancement of the second front, however, is controlled by the diffusion of H+ ions from the leaching solution toward the second front. Leaching of copper, zinc, and lead only occurs between the second front and the specimen surface. The leaching behavior of metals is modeled by considering that metals are leached from the waste matrix as a result of the advancement of the second front. The proposed model takes into account the leachable metal fraction in the waste matrix and the effect of metal remineralization on metal mobility. 相似文献
10.
This paper presents neural network-based dimension reduction of texture features in content-based image retrieval. In particular,
we highlight the usefulness of hetero-associative neural networks to this task, and also propose a scheme to combine the hetero-associative
and auto-associative functions. A multichannel Gabor-filtering approach is used to derive 30-dimensional texture features
from a set of homogeneous texture images. Multi-layer feedforward neural networks are then trained to reduce the number of
feature dimensions. Our results show that the methods lead to a reduction of up to 30% while keeping or even improving the
performance of similarity ranking. This has the benefit of alleviating the ill-effects of the high dimensionality of features
in current image indexing methods and resulting in significant speeding up retrieval rates. Results using principal component
analysis are also provided for comparison.
Receiveed: 6 July 1998?,Received in revised form: 6 November 1998?Accepted: 15 December 1998 相似文献