36 research outputs found
A numerical model of twin disc test arrangement for the evaluation of railway wheel wear prediction methods
Twin disc tests are commonly used to study wear in railway materials. In this work the implementation of a numerical model of the twin disc arrangement is given, which reproduces the distribution of tangential forces over the contact patch between the two discs. Wear is subsequently calculated by relating the forces and creepage between the two discs using three different wear functions found in the literature. The resulting wear rates are compared with experimental data for discs made of common railway wheel and rail steels. This allows a comparison and assessment of the validity of the different wear algorithms considered
Electron interactions and charge ordering in LaSrCuO
We present results of inelastic light scattering experiments on
single-crystalline LaSrCuO in the doping range and TlBaCuO at and . The main
emphasis is placed on the response of electronic excitations in the
antiferromagnetic phase, in the pseudogap range, in the superconducting state,
and in the essentially normal metallic state at , where no
superconductivity could be observed. In most of the cases we compare B
and B spectra which project out electronic properties close to
and , respectively. In the channel of electron-hole excitations
we find universal behavior in B symmetry as long as the material
exhibits superconductivity at low temperature. In contrast, there is a strong
doping dependence in B symmetry: (i) In the doping range we observe rapid changes of shape and temperature dependence of the
spectra. (ii) In LaSrCuO new structures appear for
which are superposed on the electron-hole continuum. The temperature dependence
as well as model calculations support an interpretation in terms of
charge-ordering fluctuations. For the response from fluctuations
disappears at B and appears at B symmetry in full agreement with
the orientation change of stripes found by neutron scattering. While, with a
grain of salt, the particle-hole continuum is universal for all cuprates the
response from fluctuating charge order in the range is so
far found only in LaSrCuO. We conclude that
LaSrCuO is close to static charge order and, for this reason,
may have a suppressed .Comment: 17 pages, 15 figure
Dynamical properties of charged stripes in La(2-x)SrxCuO4
Inelastic light-scattering spectra of underdoped La_2−xSr_xCuO4 single crystals are presented which provide direct evidence of the formation of quasi-one-dimensional charged structures in the two-dimensional CuO2 planes. The stripes manifest themselves in a Drude-like peak at low energies and temperatures. The selection rules allow us to determine the orientation to be along the diagonals at x=0.02 and along the principal axes at x=0.10. The electron-lattice interaction determines the correlation length which turns out to be larger in compound classes with lower superconducting transition temperatures. Temperature is the only scale of the response at different doping levels demonstrating the importance of quantum critical behavior
Phenomenology of the normal state in-plane transport properties of high- cuprates
In this article, I review progress towards an understanding of the normal
state (in-plane) transport properties of high- cuprates in the light of
recent developments in both spectroscopic and transport measurement techniques.
Against a backdrop of mounting evidence for anisotropic single-particle
lifetimes in cuprate superconductors, new results have emerged that advocate
similar momentum dependence in the transport decay rate ({\bf k}). In
addition, enhancement of the energy scale (up to the bare bandwidth) over which
spectroscopic information on the quasiparticle response can be obtained has led
to the discovery of new, unforeseen features that surprisingly, may have a
significant bearing on the transport properties at the dc limit. With these two
key developments in mind, I consider here whether all the ingredients necessary
for a complete phenomenological description of the anomalous normal state
transport properties of high- cuprates are now in place.Comment: 31 pages, 10 figure
A study on wear evaluation of railway wheels based on multibody dynamics and wear computation
The wear evolution of railway wheels is a very important issue in railway engineering. In the past, the reprofiling intervals of railway vehicle steel wheels have been scheduled according to designers' experience. Today, more reliable and accurate tools in predicting wheel wear evolution and wheelset lifetime can be used in order to achieve economical and safety benefits. In this work, a computational tool that is able to predict the evolution of the wheel profiles for a given railway system, as a function of the distance run, is presented. The strategy adopted consists of using a commercial multibody software to study the railway dynamic problem and a purpose-built code for managing its pre- and post-processing data in order to compute the wear. The tool is applied here to realistic operation scenarios in order to assess the effect of some service conditions on the wheel wear progression
Pair breaking versus symmetry breaking : origin of the Raman modes in superconducting cuprates
We performed Raman scattering experiments on superconductivity-induced features in Bi2Sr2(Ca1−xYx)Cu2O8+δ (Bi-2212), YBa2Cu3O6+x (Y-123), and Tl2Ba2CuO6+δ (Tl-2201) single crystals. The results in combination with earlier ones enable us to systematically analyze the spectral features in the doping range 0.07⩽p⩽0.24. In B2g (xy) symmetry, we find universal spectra and the maximal gap energy Δ0 to scale with the superconducting transition temperature Tc. The B1g (x2−y2) spectra in all three compounds show an anomalous increase of the intensity toward overdoping. The energy scale of the corresponding peak is neither related to the pairing energy nor to the pseudogap, but possibly stems from a symmetry breaking transition at the onset point of superconductivity at psc2≃0.27
NERAZLIKOVNOST RAZLIKA
Analiziraju se leksikološko-leksikografska polazišta i metodološki postupci u izradi Razlikovnog rječnika srpskog i hrvatskog jezika Vladimira Brodnjaka