排序方式: 共有34条查询结果,搜索用时 15 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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Experimental characteristics of a lower hybrid wave multi-junction coupler in the HT-7 tokamak 总被引:1,自引:0,他引:1
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A phase-controlled lower hybrid wave (LHW) multi-junction (MJ) coupler
(3(rows)×(columns)× (subwaveguides)) has been developed in the
HT-7 tokamak. Simulations show that it is more effective for driving plasma current
than an ordinary phase-controlled LHW antenna (3(rows)×12(columns))
(traditional coupler). The plasma--wave coupling experiments show that the
reflection coefficient (RC) is below 10%, implying that the MJ grill can launch
the wave into the plasma effectively. The effect of power spectrum launched by the
MJ coupler on RC indicates that an optimal condition is requisite for a better
coupling in the lower hybrid current drive (LHCD) experiments. Studies indicate that
the drive efficiency of the MJ antenna is higher than that of the traditional one,
which is mainly ascribed to the discrepancy in impurity concentration, plasma
temperature, and spectrum directivity. An improved confinement with an electron
internal transport barrier is obtained by LHCD. The analysis shows that the
modified negative (low) magnetic shear and the change of radial electric field
profile due to LHCD are possible factors responsible for the eITB formation. 相似文献
19.
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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