Double Negative Media Based on Magnetic Metamaterials and Semiconductors for the Microwave Frequency Range

Purpose of this paper is the development and creation of the magnetic metasurfaces with metallic inclusions operating both in the microwave and terahertz frequency ranges. Methods. The Maxwell’s equations and the expressions for the effective medium parameters are used to build the analytical models of the magnetic metasurfaces based on either a ferromagnetic (FM) or antiferromagnetic (AFM) dielectric matrix, containing a two-dimensional periodic structure of thin metal (non-magnetic) wires surrounded by insulators. Numerical simulation of such structures operating in the microwave range is carried out using the MaxLLG software package. The magnetron sputtering, liquid etching, optical lithography, and lift-off photolithography are used to create bicomponent magnetic metasurfaces, consisting of two magnetic materials with very different values of magnetization. The study of linear and nonlinear characteristics of the bicomponent magnetic metasurfaces is carried out using the methods of microwave and Brillouin spectroscopy. Results. Based on the developed analytical model of the magnetic metasurface with metallic (nonmagnetic) inclusions it is shown that the FM metasurface possesses properties of a left-handed medium in a microwave range and the AFM metasurface possesses similar properties in a terahertz range. In the last case, the material parameters of the AFM metasurface are twice negative in two frequency bands. For the magnetic metasurfaces with metallic magnetic inclusions, the formation of absorption bands in the spectrum of a traveling magnetostatic surface spin wave due to the resonant properties of the inclusions has been established. In the nonlinear regime, the effect of nonreciprocal parametric three-wave resonance was obtained. Conclusion. The results presented in the paper demonstrate a number of physical phenomena that are observed only in the magnetic metasurfaces with metallic (nonmagnetic and magnetic) inclusions.

Interest continues to grow in controlling the propagation of electromagnetic waves by utilizing periodically or randomly arranged artificial structures made of metal, dielectric, and other materials. When the size of the constituent structures and the separation between the neighboring structures are much smaller than the wavelength of the electromagnetic waves, the structure arrays behave as a continuous medium for the electromagnetic waves. That is, macroscopic medium parameters such as effective permittivity and permeability can be defined for the array. The artificial continuous medium is called a “metamaterial.” In the frequency region below the microwave frequency, the use of metallic structures as artificial media has been studied since the late 1940’s (Collin, 1990). At first, only control of the permittivity was studied and not that of the permeability. However, Pendry et al. (1999) proposed methods for fabricating artificial magnetic media, namely, magnetic metamaterials, which were built from nonmagnetic conductors. It was shown that not only can relative permeability be changed from unity but it also can have a negative value. Although the relative permeabilities of naturally occurring media are almost unity in such high frequency regions as microwave, terahertz, and optical regions, the restriction that the relative permeability is almost unity can be removed using the metamaterial. Moreover, the magnetic metamaterial enabled us to fabricate media with simultaneous negative permittivity and permeability, or negative refractive index media that were predicted by Veselago (1968). In fact, Shelby et al. (2001) made the first experimental verification of a negative refractive index metamaterial in the microwave region. This increased researcher interest in metamaterials. It was not possible to independently control the wavenumber and the wave impedance in a medium until magnetic metamaterials were developed. The wavenumber is related to the propagation and refraction of electromagnetic waves, and the wave impedance is connected with the reflection. Phenomena about electromagnetic waves are described by these two quantities. In dielectric media, both of the wavenumber and wave impedance change with a change of the permittivity, and we cannot set these parameters independently. However, the wavenumber and wave impedance can be changed independently in metamaterials because we can control the permeability as well as the permittivity with metamaterials. By utilizing the flexibility of the wavenumber and wave impedance in metamaterials, such novel phenomena as a perfect lens (superlens) (Pendry, 2000; Lagarkov & Kissel, 2004), a hyperlens (Jacob et al., 2006; Liu et al., 2007), and an invisibility cloak (Pendry et al., 2006; Leonhardt, 2006; Schurig et al., 2006) have been proposed and verified experimentally. No-Reflection Phenomena for Chiral Media

A pylon set is proposed for installation in the supersonic inlet of an air-breathing propulsion system. For rectangular and axisymmetric inlets, the pylon set is installed near the cowl front edge. This set contains 3 – 4 airfoil-shaped strips or cross-section rings depending on the type of inlet. The pylons are located at different distances (tiers) from the forebody. Fuel injection takes place through these pylons, which provides uniform mixing downstream. The mutual locations, sizes and angles of these pylons are very important for efficient application. Optimal values of geometrical parameters were determined from multi-parametric Navier-Stokes Equations (NSE) numerical simulations of the laminar and turbulent external/internal flows. These simulations have shown substantial benefits for mixing, combustion and thrust of the proposed approach by comparison with traditional well-known designs. In this paper, numerical simulation and experimental test results are presented for the cases with and without the pylon set installed in a supersonic inlet without fuel injection through the pylons. These tests are intended for examination of several phenomena. First, if a supersonic flow regime can be reached with the installed pylon set in the NASA LaRC Mach 4 Blowdown Facility. Second, comparison of inlet performance with and without pylons. Third, comparison of numerical simulation and experimental test results. And finally, improved inlet design based on results obtained in this preliminary stage of our research project. The experimental tests at the NASA LaRC were conducted in September, 2004. Some numerical simulation results for the case with fuel injection (hydrogen and helium) were obtained using the NASA VULCAN code. Details of these numerical simulation results and experimental test results obtained at the NASA LaRC Mach 6 Facility will be presented at the next appropriate AIAA Conferences. Preliminary numerical simulation results have shown the efficiency of this approach for mixing, combustion and thrust enhancement. Mach 4 numerical simulations and experimental tests results are illustrated in Figures 3 – 11 and a numerical simulation result for Mach 6 with helium injection is shown in Figure 12. _________________________________________________________ ** Research Professor, Hampton University, Senior AIAA Member ** Research Assistant, Hampton University Aeropropulsion Center *** Professor, Hampton University Aeropropulsion Center **** Professor, Hampton University Aeropropulsion Center ♦ Aerospace Engineer, NASA Langley Research Center ♦♦ Aerospace Engineer, NASA Langley Research Center ♦♦♦ Aerospace Engineer, NASA Langley Research Center + Senior Technologist, NASA Glenn Research Center, AIAA Associate Fellow 43rd AIAA Aerospace Sciences Meeting and Exhibit 10 13 January 2005, Reno, Nevada AIAA 2005-21

Investigation on interfacial shear performance of concrete strengthened with bonded steel plate

The focus of this report is the peculiarities of electromagnetic wave propagation in magnetic metamaterials with a periodic array of two-dimensional (2D) electronic gas layers. A model system is considered which consists of alternating layers of a magnetic insulator and nanoscale metallic layers or GaAs-AlGaAs-type semiconductor bilayers with 2D electronic plasma. In the presence of a strong external magnetic field perpendicular to the plane of the layers, the Landau quantization of the electron motion and confinement of the electrons within 2D layers lead to the realization of the integer quantum Hall effect. Assuming that a unit cell dimension of the structure is much smaller than the wavelength of interest and using expressions for the effective permittivity and permeability tensors of the system, the dispersion relations and behavior of refracted electromagnetic waves are studied at an arbitrary angle of incidence with respect to the magnetic field. It is shown that when the wave is incident on the top surface of the structure, the negative refraction is impossible. Despite of that, the medium exhibits a propagation of a backward wave with wavefront normal directed toward the refracting interface. In addition, the frequency regions of existence for the backward waves can be tuned by applied magnetic field. The effects of the quantization of 2D electron dynamics are examined

This paper presents the results of numerical flow simulation in ventilation mill of Kostolac B power plant, where louvers and centrifugal separator with adjustable blade angle are used. Numerical simulations of multiphase flow were performed using the Euler-Euler and Euler-Lagrange approach of ANSYS FLUENT software package. The results of numerical simulations are compared with measurements in the mill for both types of separators. Due to very complex geometry and large number of the grid cells, convergent solution with the Eulerian model could not be obtained. For this reason the mixture model was employed resulting in very good agreement with measurements, concerning the gas mixture distribution and velocity at the main and secondary burners. There was large difference between the numerical results and measurements for the pulverized coal distribution at the burners. Taking into consideration that we analyzed dilute mixture with very low volume fraction of the coal, the only choice was the Euler-Lagrange approach, i.e. discrete phase model limited to volume fraction of the discrete phase less than 10-12%. Obtained distributions of the coal at the burners agree well for both types of separators.

A large number of experimental results show that, the flow of heavy oil in porous media does not conform to Darcy seepage law. Heavy oil has the characteristics of threshold pressure gradient and its viscosity decreases nonlinearly with the increase of velocity. Heavy oil is a non-Newtonian fluid, but currently commercial reservoir numerical simulation simulators (ECLIPSE, CMG) do not have nonlinear numerical simulation function for heavy oil. In this paper, a new Hg Equation is introduced to match the nonlinear relationship between heavy oil viscosity and velocity, and a new heavy oil nonlinear reservoir numerical simulator is developed considering the threshold pressure gradient and shear thinning characteristics of heavy oil. Based on the basic data of the SZ Oilfield, this paper established a well group conceptual numerical model, and used the newly nonlinear numerical simulator for heavy oil to study the effects of the threshold pressure gradient and shear thinning of heavy oil on the laws of remaining oil distribution and development characteristics. The numerical simulation results show that the remaining oil distribution law of the model considering the nonlinear seepage characteristics of heavy oil is very different from the normal model, which is reflected in the lower sweep coefficient and the lower remaining oil saturation of the mainstream line. Based on the numerical simulation results, this paper proposed an effective pressure gradient to evaluate the sweep range of heavy oil in the reservoir and an effective well distance calculation method is proposed. In the development practice of SZ oilfield, this method has achieved very good application results. The novelty of this paper is that considering the characteristics of threshold pressure gradient and shear thinning of heavy oil, a new nonlinear reservoir numerical simulator for heavy oil is developed. The Hg equation is proposed to match the nonlinear change of heavy oil viscosity with shear rate. Based on the numerical simulation results a new calculation method of effective well distance is proposed.

It is shown that the dynamic relative permeability in a thin ferromagnetic film with in-plane magnetization in the presence of intrinsic dissipation exhibits negative values for the range of microwave frequencies belonging to those of backward volume spin-wave modes. This is accomplished according to the linearization of the equation of motion in the magnetostatic limit. By studying the coupling of backward volume spin waves with electromagnetic waves in the range of negative permeability the ferromagnetic film can be considered as a magnetic metamaterial.

We show that a deliberately engineered dispersive metamaterial slab can enable the coexistence and phase matching of ordinary fundamental and contra-propagating backward second harmonic electromagnetic waves. Energy flux and phase velocity are contra-directed in the backward waves, which is the extraordinary phenomenon that gives rise to unique nonlinear optical propagation processes. We demonstrate that frequencies, phase, and group velocities, as well as the losses inherent to the guided electromagnetic modes supported by such metamaterial, can be tailored to maximize the conversion of frequencies and to reverse the propagation direction of the generated second harmonic wave. Such a possibility, which is of paramount importance for nonlinear photonics, is proven using a numerical model describing the hyperbolic metamaterial made of carbon nanotubes standing on the metal surface. Extraordinary properties of the backward-wave second harmonic generation in the reflection direction and of the corresponding frequency doubling metareflector in the THz are investigated with a focus on the pulsed regime.

The approach of resolving analysis the cross-flow relative motion streamline on the cross-flow straight blade is presented to predict the rotation aerodynamic noise performance of cross-flow fan by solving the dipole source term of Ffowcs Williams and Hawkings equation, while the cross-flow fan is applied in the indoor unit of split-type air-conditioner and operated in the rated condition. The calculating results of the method are respectively drawn by programming in Matlab computational language, and compared with the results of CAA numerical simulation and noise experiment. There are some differences in the distribution condition of aerodynamic force fluctuation amplitude on the blade surface, and sound pressure in the related frequency on the indoor unit casing, or on the sphere far field, between the streamline computation approach and numerical simulation. The orders of magnitudes of these calculating results solved by the analysing streamline method are similar with that attained by the numerical simulation. The resolving analysis approach has the characteristics of decreasing the computing cost and not constructing the acoustics grid model of fan, compared with the numerical simulation. The error between the result of numerical simulation and noise test is larger than that between the result of theoretical calculation and noise test, so the approach could be used for the rotation aerodynamic noise analysis of the cross-flow fan.

Abstract—We present the results of synthesis of arrays of gold and bilayer Au/Ni nanorods in a matrix of porous anodic alumina and of experimental investigation and numerical simulation of their optical and magnetooptical properties. We show that the spectra of these structures have two singular features located near 520 nm and in the range of 700–800 nm. Au/Ni nanorods exhibit a significant modulation and enhancement of the magnetooptical intensity effect in the range of the long-wavelength resonance. Experimentally observed features agree with results of numerical simulation.

The optimization of flow control devices (FCDs) for a T-type five-strand billet caster tundish was carried out by water modeling and numerical simulation. In water modeling experiments, flow characteristics of the bare tundish and tundish configurations with designed U-type baffles and a round turbulence inhibitor were analyzed using residence time distribution (RTD) curves. Mathematical models for liquid steel in the real plant tundish were established using the fluid dynamics software package Fluent. The flow field, the temperature field, and the RTD curves of liquid steel in the proposed tundish configurations were obtained. The results of numerical simulation and water modeling were validated with each other by the predicted and experimental RTD curves. The results of flow field and temperature field were used to reflect the actual state of a real plant tundish and to choose the optimal FCD. Finally, from the whole performance of the multi-strand tundish, the optimal scheme was determined by combining the results of water modeling and numerical simulation. With the optimal tundish equipped with U-type baffle with deflector holes and round turbulence inhibitor, not only was the flow characteristic of each strand improved, but also the difference of flow characteristics between multiple strands was smaller.

The method of integral equations, which is based on the Green function of periodically arranged sources, is used for analyzing periodic metamaterials (photonic crystals) in the form of the simplest metallic and dielectric inclusions into a rectangular cubic lattice in a dielectric medium (matrix). Dielectric inclusions in the form of parallelepipeds and cubes are considered, as well as similar metallic inclusions (perfectly conducting metal rods) and 1D nanosized structures with metallic layers. Metal inclusions are investigated in the case of ideal conduction and in the case of penetration of a field into the metal, which is simulated as an electron plasma. The results are applicable from microwave of optical frequencies.

Through connecting split and closed rings together, a three-dimensional magnetic metamaterial is proposed in this paper. When the electric field of the induced electromagnetic wave is perpendicular to the dielectric board, this construction exhibits negative effective permeability. Its magnetic resonant frequency is insensitive to the variation of the width of the metallic wires, which facilitates practical fabrications and applications. Meanwhile this construction is of significance for designing polarization-independent and isotropic magnetic and left-handed metamaterials.

Rectangular waveguides loaded by anisotropic metamaterials are analyzed to assess the controllability of transmission characteristics of the involved electromagnetic waves. Dispersion relations of TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m0</sub> modes in the metamaterial-loaded waveguide (MLW) are theoretically investigated. It is shown that all propagating modes (the forward wave, the backward wave and the evanescent wave) in the MLW can be realized below the cut-off frequency by changing transverse and longitudinal components of permeability tensors of the loading metamaterials. Numerical simulations are carried out to verify the proposed theory and the controllability. Transmission characteristics and effective constitutive parameters of three MLWs with different cells, which should theoretically support forward waves, backward waves and evanescent waves, respectively, are numerically calculated. Dispersion curves and magnetic field distribution for the backward wave MLW and the forward wave MLW are simulated. It is shown that the simulated results are in a good agreement with theoretical predictions. Implementation of the controllable MLW was achieved by using axially rotating control rods. Rotating the control rods can reconfigure the metamaterial and make propagating modes in the MLW switch from backward waves to forward waves or evanescent waves.