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101.
102.
G. Aad B. Abbott J. Abdallah A.A. Abdelalim A. Abdesselam O. Abdinov B. Abi M. Abolins H. Abramowicz H. Abreu E. Acerbi B.S. Acharya D.L. Adams T.N. Addy J. Adelman M. Aderholz S. Adomeit L. Zwalinski 《Physics letters. [Part B]》2012,707(5):459-477
A measurement of the production cross section of top quark pairs () in proton–proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider is reported. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. Using a data sample corresponding to an integrated luminosity of , a production cross section is measured for an assumed top quark mass of . A second measurement requiring at least one jet identified as coming from a b quark yields a comparable result, demonstrating that the dilepton final states are consistent with being accompanied by b-quark jets. These measurements are in good agreement with Standard Model predictions. 相似文献
103.
Irreversibility of a quantum walk induced by controllable decoherence employing random unitary operations 下载免费PDF全文
Quantum walk is different from random walk in reversibility and interference. Observation of the reduced re- versibility in a realistic quantum walk is of scientific interest in understanding the unique quantum behavior. We propose an idea to experimentally investigate the decoherence-induced irreversibility of quantum walks with trapped ions in phase space via the average fidelity decay. By introducing two controllable decoherence sources, i.e., the phase damping channel (i.e., dephasing) and the high temperature amplitude reservoir (i.e., dissipation), in the intervals between the steps of quantum walk, we find that the high temperature amplitude reservoir shows more detrimental effects than the phase damping channel on quantum walks. Our study also shows that the average fidelity decay works better than the position variance for characterizing the transition from quantum walks to random walk. Experimental feasibility to monitor the irreversibility is justified using currently available techniques. 相似文献
104.
《Electrochemistry communications》2000,2(9):626-629
Here we demonstrate for the first time a novel kind of anode material with low sensitivity to water, which consists of natural graphite and deposited copper. Through measurement of X-ray photoelectron spectroscopy, thermogravimetric and differential thermal analysis and high resolution electron microscopy, it is found that copper exists at the surface of natural graphite in the forms of metallic copper and copper carbides. Since the deposited copper covers and removes some active sites at the surface of natural graphite, which absorbs water relatively easily, cycling behavior in the presence of high humidity (1000 ppm H2O) is improved much. Concomitantly, reversible capacity enhances due to alloying of copper with lithium. 相似文献
105.
Debashis Mondal Donald B. Percival 《Annals of the Institute of Statistical Mathematics》2010,62(5):943-966
The wavelet variance is a scale-based decomposition of the process variance for a time series and has been used to analyze,
for example, time deviations in atomic clocks, variations in soil properties in agricultural plots, accumulation of snow fields
in the polar regions and marine atmospheric boundary layer turbulence. We propose two new unbiased estimators of the wavelet
variance when the observed time series is ‘gappy,’ i.e., is sampled at regular intervals, but certain observations are missing.
We deduce the large sample properties of these estimators and discuss methods for determining an approximate confidence interval
for the wavelet variance. We apply our proposed methodology to series of gappy observations related to atmospheric pressure
data and Nile River minima. 相似文献
106.
We consider the general continuous time finite-dimensional deterministic system under a finite horizon cost functional. Our
aim is to calculate approximate solutions to the optimal feedback control. First we apply the dynamic programming principle
to obtain the evolutive Hamilton–Jacobi–Bellman (HJB) equation satisfied by the value function of the optimal control problem.
We then propose two schemes to solve the equation numerically. One is in terms of the time difference approximation and the
other the time-space approximation. For each scheme, we prove that (a) the algorithm is convergent, that is, the solution
of the discrete scheme converges to the viscosity solution of the HJB equation, and (b) the optimal control of the discrete
system determined by the corresponding dynamic programming is a minimizing sequence of the optimal feedback control of the
continuous counterpart. An example is presented for the time-space algorithm; the results illustrate that the scheme is effective. 相似文献
107.
《Spectrochimica Acta Part B: Atomic Spectroscopy》1999,54(1):223-226
Tungsten (W) MIII X-ray absorption spectra of a periodic multilayer, (Si/W)100/Si, were measured with the change of X-ray grazing angle using sample current method. Under not total reflection condition, the absorbance changed little except at W MIII absorption edge. While under the total reflection condition, the absorbance increased with the increase of the X-ray energy and the increment changed from low to high at the W MIII absorption edge. This result reflected the variation of the X-ray evanescent wavelength caused by the absorption effect of W. 相似文献
108.
109.
《Applied Surface Science》2005,239(3-4):292-301
Hybrid titanium oxide thin films containing surfactants, sodium dodecyl benzylsulfonate and sodium dodecyl sulfate, have been prepared by a novel liquid-phase deposition method. It is a new attempt to prepare organic–inorganic hybrid thin film by this method which usually be applied in preparing metal oxide thin film before. The two kinds of surfactants/TiO2 hybrid thin films were characterized by means of FT-IR, SEM, XRD, fluorescence X-ray, ICP–AES and Raman spectroscopy, and showed noticeable differences in surface top view and particle diameter, cross-section image and thickness, deposited amount of Ti, XRD patterns and Raman shift. The reasons giving rise to above differences of the two kinds composite thin films has been discussed. The deposition mechanism of organic–inorganic hybrid thin film has been also presumed. The use of this processing parameter may open up a new way to the preparing of the organic–inorganic hybrid thin film. 相似文献
110.
Hongtao Sun Liyan Zhang Junjie Zhang Chunlei Yu Shixun Dai Zhonghong Jiang 《Solid State Communications》2005,133(12):781-784
Infrared-to-visible upconversion fluorescence property of Er3+/Yb3+-codoped novel bismuth-germanium glass under 975 nm LD excitation has been studied. Intense green and red emissions centered at 525, 546 and 657 nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were observed at room temperature. The quadratic dependence of the 525, 546 and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs. The structure of the bismuth-germanium glass has been investigated by peak-deconvolution of FT-Raman spectrum, and the structural information was obtained from the peak wavenumbers. This novel bismuth-germanium glass with low maximum phonon energy (∼750 cm−1) can be used as potential host material for upconversion lasers. 相似文献