On the interaction of electromagnetic radiation with plasma of an electric jet thruster

Experimental data on the amplification of electromagnetic radiation in a plasma of an electric jet thruster are presented. The conditions of anomalous radiation-plasma interaction are established.     

Supercurrents and hydrodynamic modes in3He-A 1 in an electric field

We consider the supercurrent in superfluid³He in an electric field. The possibility to generate hydrodynamic modes (first and second sound) in theA ₁-phase by an oscillating, electric field is proposed. It is shown that the resonance technique can amplify the small amplitude of the second-sound wave. The possibility of measurement is also discussed.     

Microwave radiation enhancement and self-focusing using quasi-stationary electric field in a medium with elongated nanoparticles

It is shown that a mechanism of microwave radiation enhancement and self-focusing can be operative in a wave channel and spatial cavity filled with air containing elongated (dumbbell-shaped) nanoparticles at a volume fraction of c ₀ ∼ 10⁻³. This nonlinear medium can be pumped using a quasi-stationary electric field. At an oscillation frequency of Ω ∼ 10¹⁰−10¹¹s⁻¹, the radiation enhancement and self-focusing in a wave channel is possible over a length of Δz ∼ 50−200 m, while that in a spatial cavity can take place within a period of time Δt ∼ (2−7) × 10⁻⁷ s.     

Scale-effects on mean and standard deviation of the mechanical properties of condensed matter: an energy-based unified approach

The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.     

Scale-effects on mean and standard deviation of the mechanical properties of condensed matter: an energy-based unified approach

The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.     

1/f noise in inhomogeneous condensed media: Relation with a nonequilibrium phase transition

An approach in which the spectral density of a noise signal, varying inversely as the frequency with a fractal exponent close to 1, is due to the inhomogeneity of the medium is proposed. In the critical region the nucleation process serves as the source of inhomogeneity. Yu. Fed’kovich Chernovtsy State University Pis’ma Zh. Tekh. Fiz. 25, 1–5 (September 26, 1999)     

Thermally activated plastic flow of metals and ceramics with an electric field or current

The effects of high density electric current pulses (10³–10⁶ A cm⁻²) on the flow stress of metals at low homologous temperatures and of a modest external electric field on the flow stress of fine-grained oxides at high temperatures is presented. The results in both cases are evaluated in terms of thermally-activated plastic deformation processes. In the case of the metals, the influence of an electron wind on each of the parameters in the equation for the thermally-activated motion of dislocations was determined, the largest effect being on the pre-exponential. The derived electron wind push coefficient was one or more orders of magnitude larger than the value normally accepted for the electron drag coefficient. In the case of the oxides, the substantial effect of an applied electric field on the flow stress was evaluated in terms of its influence on the electrochemical potential of vacancies in the space-charge cloud adjacent to the grain boundaries. Both the derived space-charge cloud width and the electric potential/stress parameter Δ∅/Δσ are in reasonable accord with theoretical predictions.     

A magnetic field source system for magnetic refrigeration and its interaction with magnetocaloric material

The magnetic field source system constitutes an important component of magnetic refrigeration. A specific methodology for its' dimensioning is proposed in this paper. It is based on analytical calculation models and takes into account the geometry of the system, the magnetic properties of the magnetocaloric material and the magnetothermal cycle (direct or active magnetic regenerative refrigeration). The analytical calculation of the field is first developed and applied to usual permanent magnet-based field sources with and without soft magnetic materials. Then the forces generated by the interaction between the field and the magnetocaloric effect material are analytically evaluated considering the real field distribution. All calculations are validated thanks to two- or three-dimensional finite element method simulations.     

掺杂磁性铁粒子膨胀石墨的制备及其对毫米波的干扰作用

将经酸化处理的可膨胀石墨浸渍在二茂铁的有机溶剂中,充分搅拌并静置5h~8h,经快速加热后制得表面沉积磁性铁颗粒的膨胀石墨。利用扫描电镜观察了不同工艺条件下产物的显微形貌与元素组成。由振动磁强计测试出这种石墨蠕虫在室温静态条件下的磁化曲线及磁化率,并结合工艺条件进行了对比分析。同时,还考核了掺杂磁性铁颗粒膨胀石墨对8mm电磁波信号发生装置的干扰作用。结果表明:铁氧化物沉积在膨胀石墨表层,随着二茂铁投入量的增大,膨胀石墨磁性能提高越明显,在0A/m~7.958×105A/m磁场强度下测得其平均磁化强度≥8emu/g,在军用毫米波雷达频段的衰减率最高可达-10dB,质量消光系数大于1.0g/m2,遮蔽效果优于现役毫米波干扰剂。     

Development and applications of an analytical electron microscope with a field emission electron gun

An analytical electron microscope with a field emission electron gun has been developed in order to improve the function of material identification, in order to obtain higher resolution of images, sharper electron diffraction patterns, and purer x-ray spectra with no effects of contamination from smaller areas than in the conventional instruments so far utilized. The performance capabilities of this newly developed analytical electron microscope, the Model H-600FE, have been examined and found to be very useful for the material characterization of nanometer-size areas. Various attributes of the microscope became apparent with reference to the results of different studies. These include better convergence of the electron beam (demonstrated by examination of an MoS₂ thin film), high-resolution transmission electron microscopy (using a gold film), high-resolution scanning electron microscopy (with a carbon film containing nanometer-size holes), high-angle resolution electron diffraction (of an iron carbide film), and precision x-ray analysis of nanometer-size areas (using a pyroxene crystal and a Cu---Zn---Al shape memory alloy).     

Influence of an electric field on the hardening process and the properties of an epoxy composite discretely reinforced with phosphocarbon fibers

The influence of an electric field on the hardening process, the structure, and the properties of an epoxy composite in the presence of a phosphorus-containing carbon filler has been investigated. It has been shown that under the action of an electric field the process of formation of a three-dimensional epoxy polymer in the presence in the system of phosphocarbon fibers proceeds more intensively with the formation of a more rigidly bound structure of the polymer as compared to the same composition hardened in the absence of the field. It has been established that the fibrous filler-binder interface has a dominant role in the formation of a spatially cross-linked polymer and in the properties of the product hardened both under the action of the electric field and without it. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 47–54, May–June, 2007.     

Soil washing for metal removal: a review of physical/chemical technologies and field applications

Soil washing is one of the few permanent treatment alternatives to remove metal contaminants from soils. This paper reviews the various technology types and pilot/full-scale field applications of soil washing applicable to soils highly contaminated with heavy metals. The physical separation technologies, the chemical extraction processes and the integrated processes that combine both physical and chemical methods are discussed separately. This paper reviews basic principles, applicability, advantages and limitations, methods of predicting and improving performance of each physical/chemical technology. The discussion is based on a review of 30 recent laboratory investigations and 37 field applications of soil washing systems which have been undertaken, mostly in the US, for the period 1990-2007. This paper also examines and compares the status of soil washing technology for remediation of soils contaminated with metals in the US, in Canada and in Europe.     

Wave radiation and diffraction by a two-dimensional floating rectangular body with an opening in its bottom

The radiation and diffraction problem of a two-dimensional rectangular body with an opening in its bottom floating on a layer of water of finite depth is analysed based on the linearized velocity potential theory through an analytical solution procedure. The expressions for the potentials are obtained by the method of separation of variables, in which the unknown coefficients are determined by the boundary condition and matching requirement on the interface. The hydrodynamic coefficients and wave excitation forces are obtained and verified using the near-field and far-field methods and the symmetry properties of coupled hydrodynamic coefficients. The effect of the opening on the wave excitation force and hydrodynamic coefficients is investigated. Piston resonant behaviour and sloshing resonant behaviour are also investigated and their effect on the wave excitation force and hydrodynamic coefficients is discussed.     

Single-Gaussian-beam interaction with a dielectric microsphere: radiation forces, multiple internal reflections, and caustic structures

We analyze the generation of radiation forces in the various internal reflections that occur when a tightly focused, unpolarized Gaussian beam interacts with a dielectric microsphere. The Euler transformation is used to compute the relevant axial-force vectors that are associated with the internal reflections rapidly. The net force is computed as the average of the forces generated by the s- and p-polarization components of the electric-field vector. The force characteristics are strongly dependent on the algebraic value of the index mismatch Δn at the sphere interface. For the two cases of Δn = 0.65, 0.32 with a sphere index n(2) = 1.65, the inclusion of the contributions from the second and third internal reflections after the magnitude of the effective force by at least 10%. For Δn < 0, the individual force contributions from internal reflections beyond the first are at least 4 orders of magnitude less than those of the first interaction. The caustic structures produced by the internal reflections are also profiled for both cases of Δn = ±0.32.     

Delineation of the genomics field by hybrid citation-lexical methods: interaction with experts and validation process

In advanced methods of delineation and mapping of scientific fields, hybrid methods open a promising path to the capitalisation of advantages of approaches based on words and citations. One way to validate the hybrid approaches is to work in cooperation with experts of the fields under scrutiny. We report here an experiment in the field of genomics, where a corpus of documents has been built by a hybrid citation-lexical method, and then clustered into research themes. Experts of the field were associated in the various stages of the process: lexical queries for building the initial set of documents, the seed; citation-based extension aiming at reducing silence; final clustering to identify noise and allow discussion on border areas. The analysis of experts’ advices show a high level of validation of the process, which combines a high-precision and low-recall seed, obtained by journal and lexical queries, and a citation-based extension enhancing the recall. This findings on the genomics field suggest that hybrid methods can efficiently retrieve a corpus of relevant literature, even in complex and emerging fields.     

Preparation and characterization of a novel hydroxyapatite/carbon nanotubes composite and its interaction with osteoblast-like cells

Hydroxyapatite (HA) and its based biomaterials could chemically bond directly to bone when implanted, resulting in the formation of a strong bone-implant interface. Carbon nanotubes (CNT) are believed to be very promising in the enhancement ceramic matrix and played an important role as reinforcement for imparting strength and toughness to brittle HA bioceramic. Here we demonstrate the potential use in reinforcing biomaterials through an attempt to use CNT strengthen brittle HA bioceramic. This work aims to study the optimum sintering conditions of CNT modified HA to get CNT–HA composite with improved mechanical properties using a rapid spark plasma sintering system. The microstructure, phases, chemical compositions and mechanical properties of the ceramic samples were characterized by various advanced methods. Though no obvious chemical reaction between CNT and HA has been detected, the physical crosslink caused by the presence of CNT resulted in that a CNT–HA composite with a relatively high value of modulus (~ 131.1 GPa) and hardness (~ 6.86 GPa) achieved at the sintering temperature of 1100 °C. In vitro cellular responses to the composites were assessed to investigate the proliferation and morphology of a human osteoblast cell line cultured on the various composites.     

The extended/generalized finite element method: An overview of the method and its applications

An overview of the extended/generalized finite element method (GEFM/XFEM) with emphasis on methodological issues is presented. This method enables the accurate approximation of solutions that involve jumps, kinks, singularities, and other locally non‐smooth features within elements. This is achieved by enriching the polynomial approximation space of the classical finite element method. The GEFM/XFEM has shown its potential in a variety of applications that involve non‐smooth solutions near interfaces: Among them are the simulation of cracks, shear bands, dislocations, solidification, and multi‐field problems. Copyright © 2010 John Wiley & Sons, Ltd.