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.     

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.     

Errors in measuring the directivity of a field by the method of a reference field in the range of 25–400 MHZ

Conclusions The cited data on error components in measuring the field-strength lead to the conclusions that the reference field (provided that the distances are measured with an error of ±2%) can be determined with an error of 6%, at frequencies up to 150 MHz, and of ±7% in the range from 150 to 400 MHz. The error in determining the resulting field-strength is smaller for small angles of elevation, since the beam reflected from the ground has a substantial effect on the value of the field.     

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.     

Toward a definition of “bibliometrics”

The definitions of the term bibliometrics as used in the literature are examined and evaluated. Most such definitions are held to be too broad. A new definition is proposed; then its advantages and possible defects pointed out. A crucial question is whether Zipf's law of word occurrence should be considered a part of this particular sub-discipline.     

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.     

When is a search not a search? Part 3 – The worst of the worst: When complex applications also lack unity

Complex Applications are often difficult for patent examiners to search comprehensively due to problems relating to Articles 83 and 84 of the EPC. Non-Unity occurs when there is no single general inventive concept in an application (Article 82, EPC). But what does an examiner do when his application contains both? This article explores the particular problems and possible solutions when an application is both complex and lacking unity, and also notes that the streamlined EPO procedure can deal with these more effectively.Whilst the article comments on EPO procedure, it is the opinion of the authors alone and is not an official EPO view.     

Vorticity evolution mechanism in near‐field of a transverse jet

Abstract

Flow structure and vorticity evolution processes in the near field of an elevated jet in a crossflow are experimentally studied in a wind tunnel. The instantaneous and time‐averaged flow field characteristics are observed and measured by using a flow visualization technique and a high‐speed Particle Image Velocimeter (PIV). Time histories of the instantaneous velocity of the vortical flows in the shear‐layer are recorded by a hot‐wire anemometer and a high‐speed data acquisition system in order to analyze the frequency characteristics of the traveling coherent structure in the shear‐layer. Experiments are performed between two different jet‐to‐crossflow momentum flux ratios R = 0.08 and 0.56, which are selected from two regimes with different kinds of flow patterns at a fixed crossflow Reynolds number 2051. The behaviors and mechanisms of the vortical flow structure and the vorticity evolution mechanisms appear to be distinct in different flow regimes. By analyzing the pictures of the smoke flow visualization and the instantaneous vorticity contour maps, two kinds of vorticity evolution mechanisms, “shear‐induced vortices” and “swing‐induced vortices”, can be identified in the shear‐layer evolving from the jet exit. The time‐averaged velocity field and vorticity properties are also discussed in this paper.     

Squeezing of light field in a dissipative Jaynes–Cummings model

Based on the time-convolutionless master-equation approach, we investigate squeezing of light field in a dissipative Jaynes–Cummings model. The results show that squeezing light can be generated when the atom transits to a ground state from an excited state, and then a collapse-revival phenomenon will occur in the squeezing of light field due to atom-cavity coupling. Enhancing the atom-cavity coupling can increase the frequency of the collapse-revival of squeezing. The stronger the non-Markovian effect is, the more obvious the collapse-revival phenomenon is. The oscillatory frequency of the squeezing is dependent on the resonant frequency of the atom-cavity.     

The onset of steady Bénard-Marangoni convection in a two-layer system of conducting fluid in the presence of a uniform magnetic field

The onset of steady Bénard-Marangoni convection in two horizontal liquid layers of electrically conducting immiscible fluids subjected to a uniform vertical magnetic field and temperature gradient is analysed by means of a combination of analytical and numerical techniques. The free surface can be either deformable or nondeformable and the interface between the fluids is always assumed to be flat. The effect of the lower layer on the critical values of Rayleigh, Marangoni and wave numbers for the onset of steady convection is investigated. When the free surface is nondeformable, the critical parameters for the onset of pure Marangoni convection are increased, whereas for the onset of pure Bénard convection they are decreased compared to the single-layer model. The results for a single-layer and for two-layers are qualitatively similar for Bénard-Marangoni convection when the free surface is deformable. All disturbances can be stabilized with sufficiently strong magnetic field when the free surface is nondeformable. If the free surface is allowed to deform and gravity waves are excluded, then the layers are always unstable to disturbances with sufficiently small wave number with magnetic field. Inclusion of gravity waves has a stabilizing effect on certain disturbances of small wave number in the presence of weak or moderate magnetic field.     

Statistical reasoning in diagnostic problem-solving—The case of flow-rate measurements

There are various methods for measuring flow rates in rivers, but all of them have practical issues and challenges. A period of exceptionally high water levels revealed substantial discrepancies between two measurement setups in the same waterway. Finding a causal explanation of the discrepancies was important, as the problem might have ramifications for other flow-rate measurement setups as well. Finding the causes of problems is called diagnostic problem-solving. We applied a branch-and-prune strategy, in which we worked with a hierarchy of hypotheses, and used statistical analysis as well as domain knowledge to rule out options. We were able to narrow down the potential explanations to one main suspect and an alternative explanation. Based on the analysis, we discuss the role of statistical techniques in diagnostic problem-solving and reasoning patterns that make the application of statistics powerful. The contribution to theory in statistics is not in the individual techniques but in their application and integration in a coherent sequence of studies – a reasoning strategy.     

Stochastic analysis of groundwater flow in a two‐dimensional generalized fractal field

Abstract

Stochastic analysis of groundwater flow in a generalized fractal field is performed in this study. The random field is described by fractional Levy motion (fLm), which is a generalized version of traditional fractional Brownian motion (fBm) and is superior to describe a field with a high degree of variability. A truncated power variogram of the fLm is derived using the weighted superposition of mutually uncorrelated exponential variograms. When the Levy index of fLm α equals 2, the fBm is recovered. When the upper and lower cutoffs of the truncated power variogram are close, the stationary exponential model can be well approximated. First‐order perturbation analyses of flow in a two‐dimensional fLm field are performed and results are compared to those in the stationary exponential and fractal fBm fields. Since the proposed general fractal model has broader applications than the stationary and fBm models, it is versatile enough to simulate flow in different scenarios and provide more accurate modeling results.     

Critical assessment 28: electrical field/current application – a revolution in materials processing/sintering?

The interest towards field-assisted sintering techniques has been growing rapidly in the last 20 years, particularly in applications involving hard to sinter materials, such as nanocrystalline, refractory, and metastable materials. These techniques, in fact, allow obtaining the densification in conditions that are considerably milder than in traditional pressureless sintering or in hot-pressing. Despite this success, there is still a poor understanding of the involved basic mechanisms. In this assessment, all the main aspects associated with the use of these technique will be presented and discussed, with particular emphasis on spark plasma sintering.     

Confinement of energetic ions in a tokamak plasma at magnetic field in the range of 0.7–1.0 T

We have experimentally studied the influence of toroidal magnetic field (B _T) and plasma current (I _p) on the capture and confinement of energetic ions (EIs) formed upon ionization of a neutral beam injected in a tokamak. Based on the results of measurements of the flux of 2.45-MeV fusion neutrons, it is concluded that the amount of EIs significantly grows with increasing B _T from 0.7 to 1.0 T and Ip from 140 to 180 kA. In addition to the classical Coulomb slowing down, a supplementary channel of EI losses is found that accounts for a 15% decrease in their confinement time.     

Investigations of paper aging—a search for archive paper

The change of mechanical (folding endurance index, breaking stress, breaking length, breaking index, tear index ), optical (brightness), chemical (cold extract pH, alkali reserve) and physical (water absorbency by surface, smoothness) characteristics of 5 paper samples were measured during the accelerated aging at 105 ± 2°C, and the measured exponential dependencies were described and fitted by the formal first-order kinetics. The statistic parameters of such fitting calculations evidenced good agreement of the experimental and calculated data. The relative decrease of each paper property corresponding to 48 days of accelerated aging was evaluated in order to compare the durability of paper samples. The best aging resistance was obtained for paper MAESTRO® Classic (SCP Ruomberok, Slovak Republic) and this paper material may be recommended for archival applications.     

Unexpected Magnetic Behavior of Dinuclear Co(II) Complex in?Dithiocarbamates: A Possibility of Intramolecular Exchange Interactions

This study mainly interested in the magnetism of tetrahedrally coordinated dinuclear cobalt (II) complexes. Using the observed room temperature magnetic measurements suggested that the predicted magnetic behavior has to be tested with additional experimental measurements in order to testify the validity of the UV measurements. Using the theoretical background for magnetic behavior of Co(II) ion in a tetrahedral coordination, it is strongly recommended that the proposed structure of the complex has to be tested with additional characterization.     

When should we change the definition of the second?

The microwave caesium (Cs) atomic clock has formed an enduring basis for the second in the International System of Units (SI) over the last few decades. The advent of laser cooling has underpinned the development of cold Cs fountain clocks, which now achieve frequency uncertainties of approximately 5×10(-16). Since 2000, optical atomic clock research has quickened considerably, and now challenges Cs fountain clock performance. This has been suitably shown by recent results for the aluminium Al(+) quantum logic clock, where a fractional frequency inaccuracy below 10(-17) has been reported. A number of optical clock systems now achieve or exceed the performance of the Cs fountain primary standards used to realize the SI second, raising the issues of whether, how and when to redefine it. Optical clocks comprise frequency-stabilized lasers probing very weak absorptions either in a single cold ion confined in an electromagnetic trap or in an ensemble of cold atoms trapped within an optical lattice. In both cases, different species are under consideration as possible redefinition candidates. In this paper, I consider options for redefinition, contrast the performance of various trapped ion and optical lattice systems, and point to potential limiting environmental factors, such as magnetic, electric and light fields, collisions and gravity, together with the challenge of making remote comparisons of optical frequencies between standards laboratories worldwide.