排序方式: 共有34条查询结果,搜索用时 46 毫秒
11.
P. Belov D. Britzger S. Camarda A. M. Cooper-Sarkar C. Diaconu J. Feltesse A. Gizhko A. Glazov V. Kolesnikov K. Lohwasser A. Luszczak V. Myronenko H. Pirumov R. Plačakytė K. Rabbertz V. Radescu A. Sapronov A. Schöning S. Shushkevich W. Slominski P. Starovoitov M. Sutton J. Tomaszewska O. Turkot G. Watt K. Wichmann M. Lisovyi HERAFitter developers’ team 《The European Physical Journal C - Particles and Fields》2014,74(10):1-10
Sets of parton distribution functions (PDFs) of the proton are reported for the leading (LO), next-to-leading (NLO) and next-to-next-to-leading-order (NNLO) QCD calculations. The parton distribution functions are determined with the HERAFitter program using the data from the HERA experiments and preserving correlations between uncertainties for the LO, NLO and NNLO PDF sets. The sets are used to study cross-section ratios and their uncertainties when calculated at different orders in QCD. A reduction of the overall theoretical uncertainty is observed if correlations between the PDF sets are taken into account for the ratio of \(WW\) di-boson to \(Z\) boson production cross sections at the LHC. 相似文献
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M. A. Pedrosa C. Hidalgo E. Calderon A. Alonso R. O. Orozco J. L. De Pablos TJ-II team P. Balan 《Czechoslovak Journal of Physics》2005,55(12):1579-1587
The influence of plasma density and edge gradients in the development of perpendicular sheared flow has been investigated
in the plasma edge region of the TJ-II stellarator. It has been experimentally observed that the generation of spontaneous
perpendicular sheared flow (i.e. the naturally occurring shear layer) requires a minimum plasma density or gradient. It has
been found that there is a coupling between the onset of sheared flow development and an increase in the level of plasma edge
turbulence; once sheared flow is fully developed the level of fluctuations and turbulent transport slightly decreases whereas
edge gradients and plasma density increase. The resulting shearing rate is close to the one required to trigger a transition
to improved confinement regimes with reduction of edge turbulence, showing that spontaneous sheared flows and fluctuations
keep themselves near marginal stability.
Presented at the Workshop “Electric Fields, Structures and Relaxation in Edge Plasmas”, Tarragona, Spain, July 3–4, 2005. 相似文献
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M.?Asif the?HT- team 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):269-272
Multifaceted asymmetric radiation from the edge (MARFE) phenomena during
lower hybrid current drive (LHCD) Experiments on the HT-7 superconducting
tokamak are summarized in this paper. The best correlation has been found
between the total input (ohmic + LHCD) power and the product of the edge
line average density and Z eff. Studies show that the critical density
of MARFE onset is observed in the region of Z eff
1/2fGW = 0.6-0.9, where
, (here
is the
maximum line average electron density and nGW is the Greenwald
density). These MARFEs generally appear to have the same characteristics as
high fGW MARFEs and are positionally stable throughout the LHCD
pulse. Improved confinement mode induced by a MARFE is observed, and it is
maintained for about 65 ms. MARFE cools the plasma edge, and the electron
density profile is observed to become more narrow and peaked. 相似文献
16.
Lasue J Wiens RC Stepinski TF Forni O Clegg SM Maurice S;ChemCam team 《Analytical and bioanalytical chemistry》2011,400(10):3247-3260
ChemCam is a remote laser-induced breakdown spectroscopy (LIBS) instrument that will arrive on Mars in 2012, on-board the
Mars Science Laboratory Rover. The LIBS technique is crucial to accurately identify samples and quantify elemental abundances
at various distances from the rover. In this study, we compare different linear and nonlinear multivariate techniques to visualize
and discriminate clusters in two dimensions (2D) from the data obtained with ChemCam. We have used principal components analysis
(PCA) and independent components analysis (ICA) for the linear tools and compared them with the nonlinear Sammon’s map projection
technique. We demonstrate that the Sammon’s map gives the best 2D representation of the data set, with optimization values
from 2.8% to 4.3% (0% is a perfect representation), together with an entropy value of 0.81 for the purity of the clustering
analysis. The linear 2D projections result in three (ICA) and five times (PCA) more stress, and their clustering purity is
more than twice higher with entropy values about 1.8. We show that the Sammon’s map algorithm is faster and gives a slightly
better representation of the data set if the initial conditions are taken from the ICA projection rather than the PCA projection.
We conclude that the nonlinear Sammon’s map projection is the best technique for combining data visualization and clustering
assessment of the ChemCam LIBS data in 2D. PCA and ICA projections on more dimensions would improve on these numbers at the
cost of the intuitive interpretation of the 2D projection by a human operator. 相似文献
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The first plasma was obtained in the EAST on September 26th, 2006. Single-null (SN) and double-null (DN) diverted plasmas were achieved successfully in the EAST tokamak on January 22nd, 2007. The employed plasma diagnostics for first plasma study of EAST are as follows: a vertical one-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer for measuring the line average density, a 10-channel soft X-ray array for intensity measurement, a 16-channel heterodyne Electron Cyclotron Emission (ECE) for measuring the electron temperature profile, a 8-channel XUV bolometer array to measure plasma radiation losses, a 3-channel hard X-ray array for intensity measurement, an electromagnetic measurement system, a 35-channel Hα radiation array, 20 probes for divertor plasma, a one-channel visible bremsstrahlung emission, an impurity optical spectrum measurement system and two optical spectroscopic multi-channel analyzers (OMA). The first experimental results of diagnostic systems are summarized in this Letter. 相似文献
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Maingi R Bell RE Canik JM Gerhardt SP Kaye SM Leblanc BP Osborne TH Bell MG Fredrickson ED Lee KC Menard JE Park JK Sabbagh SA;NSTX team 《Physical review letters》2010,105(13):135004
We report observation of a new high performance regime in discharges in the National Spherical Torus Experiment, where the H mode edge "pedestal" temperature doubles and the energy confinement increases by 50%. The spontaneous transition is triggered by a large edge-localized mode, either natural or externally triggered by 3D fields. The transport barrier grows inward from the edge, with a doubling of both the pedestal pressure width and the spatial extent of steep radial electric field shear. The dynamics suggest that 3D fields could be applied to reduce edge transport in fusion devices. 相似文献
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Raman spectroscopic analysis of arctic nodules: relevance to the astrobiological exploration of Mars
Jorge-Villar SE Edwards HG Benning LG;AMASE team 《Analytical and bioanalytical chemistry》2011,401(9):2927-2933
The discovery of small, spherical nodules termed ‘blueberries’ in Gusev Crater on Mars, by the NASA rover Opportunity has given rise to much debate on account of their interesting and novel morphology. A terrestrial analogue in the form of
spherical nodules of similar size and morphology has been analysed using Raman spectroscopy; the mineralogical composition
has been determined and evidence found for the biological colonisation of these nodules from the spectral signatures of cyanobacterial
protective biochemical residues such as scytonemin, carotenoids, phycocyanins and xanthophylls. This is an important result
for the recognition of future sites for the planned astrobiological exploration of planetary surfaces using remote robotic
instrumentation in the search for extinct and extant life biosignatures and for the expansion of putative terrestrial Mars
analogue geological niches and morphologies. 相似文献