Results 1 - 10 of 440
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[en] Using the 'cone algorithm' in QCD to identify jet, the hard and soft processes in high energy hadronic collisions are analysed in detail. A Monte Carlo simulation event sample is produced by PYTHIA. The resultant pseudorapidity distribution of jets has a plateau in the central region. The particle and transverse energy density in jets decreases exponentially with the increase of the distance from particles to jet axis. Through comparisons, we find the event average transverse momentum or maximum transverse momentum is positively correlated with multiplicity for the whole event sample, and negatively correlated with multiplicity for jet event subsample. Two ratio variables well describe the hardness of jet events, and they are positively correlated with the event average transverse momentum and negatively correlated with multiplicity, which confirms the event average transverse momentum is a better characteristic quantity to describe the hardness of jet events than multiplicity
[en] According to jet definition-cone algorithm to identify jets, the authors reanalyze UA1 minimum-bias non-single diffractive pp-bar data at √s 630 GeV. The correlations between pt-bar and multiplicity for the event sample and subsamples are studied in detail. The authors found that they are positively correlated for the event sample, while negatively correlated for the jet event subsample. The correlations and decorrelations between mini-jets are also studied. The authors further analyse the possibility of large rapidity gap existence between the two minijets, and find that there are no particles between two minijets in some events, but the statistics are not enough
[en] A detailed comparison between the kinetic and the thermodynamic effects on grain growth was given, and the corresponding models were fitted to the experimental data, respectively. It was found that both models can explain the derivation from the normal parabolic growth under ideal condition. According to the kinetic model, a single isothermal grain growth can be understood in terms of a single, thermally-activated rate process with constant Q and grain boundary (GB) energy, σb; impurity atoms accumulated in the GBs might exert a retarding force on GB migration, but do not change the grain growth activation energy, Q. On the other hand, it is necessary to invoke variable Q and σb according to the thermodynamic model, where the probably existing impurities and/or surface oxide seem to block surface and/or GB diffusion path, thus increasing Q and reducing σb
[en] Geochemical characteristics of rare-earth elements and metallogenetic elements in the ore-bearing volcanics are discussed on the basis of analytical results of l5 samples. The concentration of rare-earth elements is higher in mineralized volcanics than in unmineralized ones. The ores are especially rich in heavy rare-earth elements. Major compatible elements in the ores are U, Th, Mo, Pb etc., among which U, Th, Mo can be used. It was assumed that the metallogenetic materials might come from sialic crust and the concentration of metallogenic elements is closely related to magmatic differentiation
[en] The 'Cone algorithm' for the identification of jets is studied in some detail. Two methods are given to identify jets using the momenta of final state particles. Making use of the data sample produced by the LUND-PYTHIA Monte Carlo generator hadron-hadron collision events, the two methods are tested and compared with each other. An effective and practical method to identify jets is obtained
[en] Considering a spherical misfitting precipitate growing into a finite elastic-perfectly plastic supersaturated matrix, a kinetic modeling for such solid-state partitioning phase transformation is presented, where the interactions of interface migration, solute diffusion and misfit accommodation are analyzed. The linkage between interface migration and solute diffusion proceeds through interfacial composition and interface velocity; their effects on misfit accommodation are mainly manifested in an effective transformation strain, which depends on instantaneous composition field and precipitate size. Taking γ to α transformation of a binary Fe-0.5 at.% C alloy under both isothermal and continuous cooling conditions as examples, the effects of misfit accommodation on the coupling interface migration and solute diffusion are well evaluated and discussed. For the isothermal transformation, a counterbalancing influence between mechanical and chemical driving forces is found so that the mixed-mode transformation kinetics is not sensitive with respect to the elastic–plastic accommodation of the effective misfit strain. Different from the isothermal process, during the continuous cooling condition, the effects of misfit accommodation on the kinetics of solid-state partitioning phase transformation are mainly manifested in the great decrease of the transformation starting temperature and the thermodynamic equilibrium composition. The present kinetic modeling was applied to predict the experimentally measured γ/α transformation of Fe-0.47 at.% C alloy conducted with a cooling rate of 10 K min"−"1 and a good agreement was achieved.
[en] We demonstrate two distinctive effects of strain-induced island-island interaction on island size and spatial distribution during coarsening of 2D islands. When coarsening proceeds via only mass transport between islands, the interaction broadens the island size distribution, leading to a power-law dependence of island size uniformity on island number density. When coarsening proceeds via island migration in addition to mass transport between islands, the interaction can effectively direct island motion through island edge diffusion, leading to self-organized formation of a regular array of islands with both uniform size and spacing
[en] Structural inhomogeneity is found to be a promising way to overcome intrinsic brittleness and to improve the plasticity of metallic glasses (MGs), although such inhomogeneity has not been well-understood. In this study, quantitative observations and theoretical explanations on the structural inhomogeneity were presented for Al_8_8Ce_8Co_4 MG. Applying a technique called energy filtered electron diffraction (EFED), different medium-range orders (MROs) reflected from conspicuous and inconspicuous prepeaks, were observed, which, following reduced pair distribution functions obtained from the EFED measurement, correspond to different short-range orders (SROs). Then using reverse Monte Carlo (RMC) simulation, the structural inhomogeneity is attributed to diversity of Al−Co clusters, which lead to loosely and densely packed local atomic structures and contribute to soft and hard regions, as evidenced by synchrotron radiation X-ray diffraction, dynamic mechanical analysis and nano-indentation. The obtained structural essence of intrinsic inhomogeneity in MGs lays the foundation for further understanding and designing MGs with high plasticity, by adjusting properly inhomogeneous structure.
[en] The volcanic complex of Northwestern Zhejiang were previously classified as Jiande Group (upper Jurassic) which was subdivided into Laocun, Huangjian, Shouchang and Henshan formation. The age from the acid volcanic samples of these formation i.e. 132 Ma, 107 Ma and 93 Ma respectively has got by the authors. The results reflect that Laocun and Huangjiang formatiions belong to lower Cretaceous, but Shouchang formation should be classified as upper Cretaceous. The initial 87Sr/86Sr value, in the range of 0.70561-0.71434, showed the volcanic rocks are the anatexisic product of middle-lower sialic crust, and mixed with a little some of the mantle materials since there is individual lower value of 87Sr/86Sr