27,836 research outputs found
Exact O(g^2 alpha_s) top decay width from general massive two-loop integrals
We calculate the b-dependent self-energy of the top quark at O(g^2 \alpha_s)
by using a general massive two-loop algorithm proposed in a previous article.
From this we derive by unitarity the O(\alpha_s) radiative corrections to the
decay width of the top quark, where all effects associated with the quark
mass are included without resorting to a mass expansion. Our results agree with
the analytical results available for the O(\alpha_s) correction to the top
quark width
Analysis on the hull girder ultimate strength of a bulk carrier using simplified method based on an incremental-iterative approach
The hull girder ultimate strength of a typical bulk carrier is analyzed using a simplified method based on an incremental-iterative approach. First, vertical bending moment is examined by seven different methods. The moment versus curvature curves and the values of the ultimate longitudinal moments at collapse states are determined for both hogging and sagging cases. Second, the ultimate strength under coupled vertical and horizontal bending moment is accounted. An interaction curve is obtained, which corresponds to the results of series of calculation for the ship hull subject to bending conditions with different angles of curvature. It is found that the interaction curve is asymmetrical because the hull cross section is not symmetrical with respect to the horizontal axis and the structural response of the elements under compression is different from that under tension due to nonlinearity caused by buckling. The angles of the resultant bending moment vector and that of the curvature vector are different in investigated cases. The interaction design equations proposed by other researches are also addressed to discuss the results presented by this study
Chaos, Determinacy and Fractals in Active-Sterile Neutrino Oscillations in the Early Universe
The possibility of light sterile neutrinos allows for the resonant production
of lepton number in the early universe through matter-affected neutrino mixing.
For a given a mixing of the active and sterile neutrino states it has been
found that the lepton number generation process is chaotic and strongly
oscillatory. We undertake a new study of this process' sensitivity to initial
conditions through the quantum rate equations. We confirm the chaoticity of the
process in this solution, and moreover find that the resultant lepton number
and the sign of the asymmetry produces a fractal in the parameter space of
mass, mixing angle and initial baryon number. This has implications for future
searches for sterile neutrinos, where arbitrary high sensitivity could not be
determinate in forecasting the lepton number of the universe.Comment: 6 pages, 3 figure
In-plane thermal conductivity of large single crystals of Sm-substituted (YSm)BaCuO
We have investigated the in-plane thermal conductivity of
large single crystals of optimally oxygen-doped
(Y,Sm)BaCuO (=0, 0.1, 0.2 and 1.0)
and YBa(CuZn)O(=0.0071) as functions
of temperature and magnetic field (along the c axis). For comparison, the
temperature dependence of for as-grown crystals with the
corresponding compositions are presented.
The nonlinear field dependence of for all crystals was observed
at relatively low fields near a half of . We make fits of the
data to an electron contribution model, providing both the mean
free path of quasiparticles and the electronic thermal conductivity
, in the absence of field. The local lattice distortion due to the
Sm substitution for Y suppresses both the phonon and electron contributions. On
the other hand, the light Zn doping into the CuO planes affects solely
the electron component below , resulting in a substantial decrease in
.Comment: 7 pages,4 figures,1 tabl
Spanning Properties of Theta-Theta Graphs
We study the spanning properties of Theta-Theta graphs. Similar in spirit
with the Yao-Yao graphs, Theta-Theta graphs partition the space around each
vertex into a set of k cones, for some fixed integer k > 1, and select at most
one edge per cone. The difference is in the way edges are selected. Yao-Yao
graphs select an edge of minimum length, whereas Theta-Theta graphs select an
edge of minimum orthogonal projection onto the cone bisector. It has been
established that the Yao-Yao graphs with parameter k = 6k' have spanning ratio
11.67, for k' >= 6. In this paper we establish a first spanning ratio of
for Theta-Theta graphs, for the same values of . We also extend the class of
Theta-Theta spanners with parameter 6k', and establish a spanning ratio of
for k' >= 5. We surmise that these stronger results are mainly due to a
tighter analysis in this paper, rather than Theta-Theta being superior to
Yao-Yao as a spanner. We also show that the spanning ratio of Theta-Theta
graphs decreases to 4.64 as k' increases to 8. These are the first results on
the spanning properties of Theta-Theta graphs.Comment: 20 pages, 6 figures, 3 table
Recommended from our members
Fluid drag-reducing effect and mechanism of superhydrophobic
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In this paper, drag-reducing property and mechanism of superhydrophobic surface are investigated.
Superhydrophobic surfaces with micro-nano textures were fabricated and tested using SEM and contact
angle measurement. Experiments on a channel and a flat plate with superhydrophobic surface were
conducted separately. For the channel flow, the drag was acquired by measuring the pressure loss. A 54%
drag reduction was found both in laminar and turbulent flow over Re range from 500 to 5000. For flow over
a plate, PIV measurement was used to obtain the velocity distribution at Reδ=12000. There was a 19%
reduction on the total stress in the whole boundary layer. Suppressions of the turbulence intensities and the
Reynolds shear stress were found, which may cause the drag reduction
- …