Can a repulsive potential in graphene have boundstates in a magnetic field?

We consider Klein tunneling through a repulsive and cylindrical potential with range R and strength V. Recently it was found that, in the strong coupling regime R/l < 1, the repulsive potential can have bound states peaked inside the potential with tails extending over l mean square root of 2(N+1), where N is Landau level (LL) index and f is the magnetic length. The presence of these bound states is a consequence of a subtle interplay between Klein tunneling and quantization effect of magnetic fields. Because of the presence of these bound states the effective coupling between the repulsive potential and an electron can be attractive. Here we show that this effect is a consequence of singular interaction between the repulsive potential and an electron that cannot be captured in perturbative approaches.     

Convective Heat Transfer in a Bubble Laminar Flow in a Round‐Cylinder Tube

The problem of heat exchange between a twophase laminar flow in a roundcylinder tube and the isothermal wall of the tube is studied. An exact analytical solution is obtained.     

Grey Problems of a Mechanical Transmission System in a Reliability Study

1 IntroductionReiability acted as an imPortant index that was aPPied to weigh the quality of a mechanicalProdct, and it has brOadiy been thought. Currently, an imPortant taSk of machine scope is to aimat the market's needs inside and outside the country and adust the strUcture of ProductS tooccuPy the Inarket in Products of high qualiy It is a key aspeCt of all tO sahsfy reiability needsof users in the new Products explored. The machine transAnssion system is an imPortantcomPosition of…     

Diffusion of carbon and titanium in γ -iron in a magnetic field and a magnetic field gradient

The diffusion coefficients of carbon and titanium in γ -iron were measured in a 6T magnetic field and in magnetic field gradients ranging from 30 to 45 T/m. We have found that the diffusion of carbon in γ -iron is retarded by application of a 6T magnetic field. In contrast with carbon diffusion, no noticeable effect of a magnetic field on the diffusivity of titanium in γ -iron is observed. On the other hand, the diffusion of carbon in γ -iron can be enhanced in a magnetic field gradient when carbon atoms move towards the direction with a higher magnetic field strength. The higher the magnetic field gradient strength becomes, the more the carbon diffusion is enhanced. Nevertheless, a magnetic field gradient causes a decrease in diffusivity of carbon in γ -iron when the opposite magnetic field gradient is applied.     

What’s in a name?

SomerecentsubmissiontoCARBONhaveindicatedatrendtogetcertain“buzz”wordsintothetitle .Themostcommonbeing“nano” ,andmore recently“fullerene like” .Inthelasteightmonthsover 35 %ofallpaperssubmittedtomehavenanointhetitle .WithrespecttotheformerIhavebeenp     

What＇ s in a name？

Some recent submission to CARBON have indicateda trend to get certain “buzz” words into the title.The most common being “nano”, and more-recently “fullerene-like”. In the last eight months over 35 % of all papers submitted to me have nano in the title. With respect to the former I have been presented with nanothermodynamics,nanobuckling, nanocomposite, with one even talking about a “nanotube nanocomposite” !     

The Behaviour of Mg in γ-phase in a Ni-base Superalloy

1.IntroductionSince the biginning of 1960s,the effectof Mg upon superalloy has been studiedand some satisfactory developments havebeen achieved.The role of Mg on the alloycan be summarized as follows:(1)Themechanical plasticity of Ni-base superalloycan be improved by adding Mg asdesulphurizer,because of forming insolubleMgS instead of other low melting eutectic     

Fe–As Bond Fluctuations in a Double-Well Potential in LaFeAsO

While for a long time, iron-based superconductors have been investigated looking at the average crystalline structure, there is now growing interest on the divergence of local from the average structure. Here, we use advanced data analysis of EXAFS, a fast and local probe, which has key advantages compared to crystallographic measurements, in unveiling the dynamics of the local structure. The results show that the Fe–As pair oscillates in the double-well potential both in undoped and in cobalt-doped LaFeAsO crystals. The parameters and the characteristics of the double-well potential are determined by curve fits of the polarized EXAFS data. Temperature-dependent Fe–As pair distribution and tunneling frequency are derived from selected model of two potential wells. We observe the softening of the Fe–As oscillations at the tetragonal to orthorhombic structural phase transition at 150 K in LaFeAsO. A weak broad softening is observed while decreasing the temperature from 70 to 40 K in superconducting LaFe_0.89Co_0.11AsO which could be correlated with the onset of short-range charge density wave order.     

Heterodiffusion of aluminum in α-iron in a pulsed magnetic field

Using an X-ray diffraction technique, the coefficients of volume diffusion of Al in α-Fe at T = 730°C have been measured for the first time in a pulsed magnetic field with a pulse amplitude of 39.8–238.8 kA/m and a frequency of 1–8 Hz. It is established that both frequency and amplitude of magnetic field pulses significantly influence the diffusion process.     

Growth rates of Bénard-Marangoni convection in a fluid layer in the presence of a magnetic field

In this paper we analyze the effect of a uniform vertical magnetic field on the linear growth (and decay) rates of the steady Bénard-Marangoni instability in a horizontal layer of quiescent, electrically conducting fluid with a uniform vertical temperature gradient subject to a prescribed heat flux at its lower boundary. Explicit analytical expressions for the linear growth rates of long-waves instability modes are derived for the first time. The numerically-calculated linear growth (or decay) rates showing the stabilizing effect of the magnetic field are also presented.     

Vortex Dynamics in a Superconducting Film with a Kagome and?a?Honeycomb Pinning Landscape

The vortex dynamics in a superconducting thin Al film with a periodic Honeycomb or Kagome array of antidots has been investigated by electrical transport measurements. The large values of the superconducting coherence length and penetration depth of the Al films guarantee a maximum of one flux quantum trapped per pinning site. This allows us to directly compare the experimental results with previous theoretical investigations based on molecular dynamics simulations. For the Kagome lattice, two submatching features not anticipated theoretically at H/H ₁=1/3 and 2/3, where H ₁ is the field at which the number of vortices coincides with the number of pinning sites, are observed. Possible corresponding stable vortex patterns are suggested. For the Honeycomb pinning landscape, the commensurability effects are in agreement with the theoretical expectations. A preliminary analysis of the vortex mobility in this lattice shows the presence of a weak vortex guidance.     

Room temperature age-hardening in a β titanium alloy

A metastable titanium alloy containing 10 wt % Zr and 12 wt % V has been found to undergo a substantial age-hardening reaction at temperatures as low as 20° C. The reaction involves continued growth of athermal-phase particles produced during water quenching from the-phase field. The morphology of the as-quenched is retained, implying the absence of long-range diffusion during ageing: this is consistent with the low value of the activation energy measured (93 kJ kg mol^–1). It is suggested that the growth is caused by unpinning of/ interfaces as a result of the short-range motion of interstitials present in the alloy. The age-hardening produces a severe loss in tensile ductility and inhibition of stress-induced martensite formation.     

Ageing drivers: storm in a teacup?

The purpose of this paper is to address two important issues regarding ageing drivers. First, there is a presumption in the road safety arena that the expected increase in the number of ageing drivers on the roads will lead to an increase in crashes. Second, despite extensive research on ageing drivers, especially on their increased vulnerability and reduced driving abilities, the most widely recommended road safety strategy relates to the control of their driving licenses. This presumption and the associated policy recommendation are based mainly on the higher relative crash risks associated with ageing drivers compared to their younger counterparts. This study, however, argues that the average crash risks obtained in previous studies provide only indirect information concerning these issues and any decision based on these results may produce unexpected outcomes. An analytical framework to examine the marginal effect of changing the driver mix on the roads is proposed and a simple empirical model is estimated as an illustration. In contrast to previous studies, we found that increasing the number of licenses issued to ageing drivers had only an insignificant impact on the number of fatal crashes on the roads, suggesting that the concern over ageing drivers may be a storm in a teacup.     

Paramagnetic resonance in a “dirty” spin-glass

For a spin-glass with nonmagnetic defects (n _m ^1/3l 1, where n _m is the magnetic impurity concentration and l is the mean free path) an absorption function () is derived. Three ranges of temperature and external magnetic field are considered. In the vicinity of the transition the value of () d is estimated as a function of temperature and field.     

Current–voltage characteristics of a flat probe in a rarified plasma flow

Mathematical and numerical models of a collision-free plasma flow about the flat probe are developed. The current–voltage characteristics of flat probes located along and transverse across the flow, as well as the distributions of the current density over the probe width, are obtained. The numerical simulation results might be applied in probe diagnostics of plasma flows.     

Heat‐Transfer Processes in a Plasma Reactor in Destruction of Pesticides

The possibility of using a multijet electric arc plasmachemical reactor for decontamination and destruction of different powder pesticides with an expired effective date and storage life which have not been used in agriculture is studied. Studies of heat transfer are conducted on a setup operating without processing of raw material and with supply of pesticides (isophen and butyl ester of 2,4dichlorophenoxyacetic acid) to the reactor. The composition of waste gases at the reactor outlet is studied.     

Structural changes in ScCeSZ–NiO ceramics in a high-temperature hydrogen environment

It is shown that, in a solid oxide cell with ceramic Ni-containing anodes, in the first working cycle, the anode material is reduced in hydrogen, which causes changes in its microstructure and properties. We analyze structural changes in the anode material with different contents of NiO from the nonreduced (ScCeSZ–NiO) to the reduced (ScCeSZ–Ni) state, which are connected with its electric conductance.